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  Subjects -> PHYSICS (Total: 734 journals)
    - ELECTRICITY AND MAGNETISM (7 journals)
    - MECHANICS (18 journals)
    - NUCLEAR PHYSICS (44 journals)
    - OPTICS (84 journals)
    - PHYSICS (536 journals)
    - SOUND (17 journals)
    - THERMODYNAMICS (28 journals)

PHYSICS (536 journals)            First | 1 2 3 4 5 6 | Last

ECS Journal of Solid State Science and Technology     Full-text available via subscription  
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 4)
Embedded Systems Letters, IEEE     Hybrid Journal   (Followers: 14)
Energy Procedia     Open Access   (Followers: 2)
Engineering Failure Analysis     Hybrid Journal   (Followers: 22)
Engineering Fracture Mechanics     Hybrid Journal   (Followers: 15)
Environmental Fluid Mechanics     Hybrid Journal   (Followers: 2)
EPJ Nonlinear Biomedical Physics     Open Access  
EPJ Web of Conferences     Open Access  
European Journal of Physics     Full-text available via subscription   (Followers: 4)
European Journal of Physics Education     Open Access   (Followers: 5)
European Physical Journal - Applied Physics     Full-text available via subscription   (Followers: 4)
European Physical Journal C     Hybrid Journal  
Europhysics News     Open Access   (Followers: 1)
Experimental Mechanics     Hybrid Journal   (Followers: 14)
Experimental Methods in the Physical Sciences     Full-text available via subscription  
Experimental Techniques     Hybrid Journal   (Followers: 15)
Exploration Geophysics     Hybrid Journal   (Followers: 3)
Few-Body Systems     Hybrid Journal  
Fire and Materials     Hybrid Journal   (Followers: 4)
Flexible Services and Manufacturing Journal     Hybrid Journal   (Followers: 2)
Fluctuation and Noise Letters     Hybrid Journal   (Followers: 1)
Fluid Dynamics     Hybrid Journal   (Followers: 5)
Fortschritte der Physik/Progress of Physics     Hybrid Journal  
Frontiers in Physics     Open Access   (Followers: 2)
Frontiers of Materials Science     Hybrid Journal   (Followers: 4)
Frontiers of Physics     Hybrid Journal   (Followers: 1)
Fusion Engineering and Design     Hybrid Journal   (Followers: 2)
Geochemistry, Geophysics, Geosystems     Full-text available via subscription   (Followers: 21)
Geografiska Annaler, Series A: Physical Geography     Hybrid Journal   (Followers: 3)
Geophysical Research Letters     Full-text available via subscription   (Followers: 41)
Geoscience and Remote Sensing, IEEE Transactions on     Hybrid Journal   (Followers: 19)
Glass Physics and Chemistry     Hybrid Journal   (Followers: 1)
Granular Matter     Hybrid Journal   (Followers: 2)
Graphs and Combinatorics     Hybrid Journal   (Followers: 5)
Handbook of Geophysical Exploration: Seismic Exploration     Full-text available via subscription  
Handbook of Metal Physics     Full-text available via subscription  
Handbook of Surface Science     Full-text available via subscription   (Followers: 2)
Handbook of Thermal Analysis and Calorimetry     Full-text available via subscription  
Haptics, IEEE Transactions on     Hybrid Journal   (Followers: 4)
Heat Transfer - Asian Research     Hybrid Journal   (Followers: 5)
High Energy Density Physics     Hybrid Journal   (Followers: 1)
High Pressure Research: An International Journal     Hybrid Journal   (Followers: 1)
IEEE Journal of Quantum Electronics     Hybrid Journal   (Followers: 12)
IEEE Signal Processing Magazine     Full-text available via subscription   (Followers: 21)
IET Optoelectronics     Hybrid Journal   (Followers: 2)
Il Colle di Galileo     Open Access  
Imaging Science Journal, The     Hybrid Journal   (Followers: 2)
Indian Journal of Biochemistry and Biophysics (IJBB)     Open Access   (Followers: 4)
Indian Journal of Physics     Hybrid Journal   (Followers: 4)
Indian Journal of Pure & Applied Physics (IJPAP)     Open Access   (Followers: 8)
Indian Journal of Radio & Space Physics (IJRSP)     Open Access   (Followers: 4)
Industrial Electronics, IEEE Transactions on     Hybrid Journal   (Followers: 9)
Industry Applications, IEEE Transactions on     Hybrid Journal   (Followers: 5)
Infinite Dimensional Analysis, Quantum Probability and Related Topics     Hybrid Journal  
InfraMatics     Open Access  
Infrared Physics & Technology     Hybrid Journal  
Intelligent Transportation Systems Magazine, IEEE     Full-text available via subscription   (Followers: 1)
Intermetallics     Hybrid Journal   (Followers: 4)
International Applied Mechanics     Hybrid Journal   (Followers: 2)
International Geophysics     Full-text available via subscription   (Followers: 3)
International Heat Treatment & Surface Engineering     Hybrid Journal   (Followers: 2)
International Journal for Computational Methods in Engineering Science and Mechanics     Hybrid Journal   (Followers: 8)
International Journal for Ion Mobility Spectrometry     Hybrid Journal   (Followers: 1)
International Journal for Simulation and Multidisciplinary Design Optimization     Full-text available via subscription   (Followers: 1)
International Journal of Abrasive Technology     Hybrid Journal   (Followers: 2)
International Journal of Aeroacoustics     Full-text available via subscription   (Followers: 6)
International Journal of Applied Electronics in Physics & Robotics     Open Access  
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 3)
International Journal of Computational Materials Science and Surface Engineering     Hybrid Journal   (Followers: 7)
International Journal of Damage Mechanics     Hybrid Journal   (Followers: 5)
International Journal of Fatigue     Hybrid Journal   (Followers: 5)
International Journal of Fracture     Hybrid Journal   (Followers: 8)
International Journal of Geometric Methods in Modern Physics     Hybrid Journal   (Followers: 1)
International Journal of Geophysics     Open Access   (Followers: 3)
International Journal of Heat and Fluid Flow     Hybrid Journal   (Followers: 9)
International Journal of Low Radiation     Hybrid Journal  
International Journal of Low-Carbon Technologies     Open Access   (Followers: 1)
International Journal of Mass Spectrometry     Hybrid Journal   (Followers: 11)
International Journal of Material Forming     Hybrid Journal   (Followers: 2)
International Journal of Materials and Product Technology     Hybrid Journal   (Followers: 4)
International Journal of Mechanical Sciences     Hybrid Journal   (Followers: 5)
International Journal of Mechanics and Materials in Design     Hybrid Journal   (Followers: 5)
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology     Open Access   (Followers: 4)
International Journal of Micro-Nano Scale Transport     Full-text available via subscription   (Followers: 1)
International Journal of Microstructure and Materials Properties     Hybrid Journal   (Followers: 7)
International Journal of Microwave Science and Technology     Open Access   (Followers: 2)
International Journal of Modeling, Simulation, and Scientific Computing     Hybrid Journal   (Followers: 1)
International Journal of Modern Physics A     Hybrid Journal   (Followers: 1)
International Journal of Modern Physics B     Hybrid Journal  
International Journal of Modern Physics C     Hybrid Journal  
International Journal of Modern Physics D     Hybrid Journal  
International Journal of Modern Physics E     Hybrid Journal   (Followers: 1)
International Journal of Nanomanufacturing     Hybrid Journal   (Followers: 1)
International Journal of Nanoscience     Hybrid Journal   (Followers: 1)
International Journal of Nanotechnology     Hybrid Journal   (Followers: 4)
International Journal of Non-Linear Mechanics     Hybrid Journal   (Followers: 4)
International Journal of Physical Sciences     Open Access  
International Journal of PIXE     Hybrid Journal   (Followers: 1)
International Journal of Plasticity     Hybrid Journal   (Followers: 6)

  First | 1 2 3 4 5 6 | Last

Journal Cover COSPAR Colloquia Series
   Follow    
   Full-text available via subscription Subscription journal
     ISSN (Print) 0964-2749
     Published by Elsevier Homepage  [2563 journals]
  • Kinetic Instabilities in a Thin Current Sheet
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      A thin current sheet with thickness comparable to the ion inertial length gives rise to decoupling of ions from electrons. This situation is favorable for a number of dynamic processes leading to particle acceleration and plasma turbulence. In this article, we investigate the cross-field current instability that can be excited in a thin current sheet with a non-zero magnetic field component normal to the current sheet surface. There is strong observational evidence for this instability and substantial theoretical work on it. We first discuss briefly the observational basis, followed by a brief overview of theoretical predictions. We then present particle simulation of this instability for a thin current sheet using a two-dimensional fully electromagnetic particle-in- cell code. The instability is found to develop rapidly, resulting in particle acceleration, current filamentation, current density reduction at the sheet center, current sheet broadening, and undulations of the current sheet profile. These features revealed from simulation are quite similar to those observed for current disruption.


      PubDate: 2012-12-15T09:30:44Z
       
  • Plasma Sheet Expansion Observed by Cluster and Geotail
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Between 1000 and 1800 UT on October 10, 2001, when Cluster was approaching the plasma sheet from the northern lobe, Geotail traversed the southern lobe also approaching the plasma sheet during two substorm intensifications identified in the Kakioka magnetogram. In this paper we examine the temporal change of the tail configuration and evolution of the plasma sheet between 11 and 13 UT, when multiple intensifications of the first substorm took place. Changes in the tail configuration toward a dipole-like field were identified during all intensifications, suggesting plasma sheet expansion which were embedded in a gradual northward motion of the tail. We emphasize the importance of simultaneous measurements in both hemispheres in order to identify plasma sheet expansion or dipolarization, because flapping motions or local enhancements of the tail current density may mask and mimic the signatures. During a later intensification, Geotail and Cluster encountered the plasma sheet boundary layer, which is the most direct signature of expansion of the plasma sheet. Using the time difference among the Cluster four spacecraft and Geotail, the possible propagation speed of the dipolarization and spatial scale of the disturbance is discussed. In addition to the usual dawn-to-dusk electric field, significant contribution from a north-south electric field were observed both in the lobe and at the boundary of the plasma sheet associated with the dipolarization. This suggests the importance of the effects from a localized source region for dipolarization and/or reconnection process.


      PubDate: 2012-12-15T09:30:44Z
       
  • Geotail-Polar Observation of Substorm-Time Field Increase in the Tail and
           the Polar Magnetosphere
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We present a case study of substorm-time magnetic field perturbations in high-altitude polar lobe and in the tail lobe, simultaneously observed by the POLAR and GEOTAIL satellites, together with ground-based CANOPUS observations and WIND solar-wind observations. During the growth phase, the magnetic field strength (B total) increased both in the polar lobe (observed by POLAR) and in the tail lobe (observed by GEOTAIL); this is ascribed to the pileup of dayside-reconnected field lines over the magnetopause. On the other hand, while B totalat GEOTAIL decreased during the expansion phase, B totalat POLAR did not start decreasing until ~35 min after the expansion onset. This absence of the field-decrease signature in the polar lobe for ~35 min could be attributed to dipolarization/compression of closed field line region of the nightside inner magnetosphere. This compression could offset the effect of the magnetic field decrease in the polar lobe, and would be absent in the open field line region of the tail lobe allowing GEOTAIL to detect the decrease in B totalduring this ~35 min period.


      PubDate: 2012-12-15T09:30:44Z
       
  • Types of Auroral-Zone Disturbances: Current Status on Identification and
           Understanding
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      It is now known that there are several different types of auroral zone disturbances, each reflecting fundamentally different processes within the magnetosphere-ionosphere system. Four types known to be dynamically important are described here. Substorms follow a ≳ 0.5 hr growth period of enhanced convection. Onset occurs within the near-Earth plasma sheet and is often followed by new magnetic X-line in the mid-tail. Evidence now indicates that substorm onset results from a transition from a stable to unstable state of the nightside magnetosphere that initiates a few minutes prior to onset as the result of a reduction in the strength of convection caused by an appropriate change in the interplanetary magnetic field impacting the magnetosphere. Convection driven auroral enhancements occur at midnight-to-dawn MLTs and result from plasma sheet electrons, which are strongly energized during periods of enhanced convection and magnetic drift around the dawn side. Enhancements in solar wind dynamic pressure cause global disturbances that can be quite dramatic. These disturbances consists of increases in magnetospheric and ionospheric currents and electric fields, enhancements in auroral emissions and broadening of the auroral oval, and significant shrinkage of the polar cap size. Poleward boundary intensifications (PBIs) are auroral enhancements that initiate along the poleward boundary of the auroral oval. They occur during all overall levels of geomagnetic activity and are associated with few minute flow bursts in the tail plasma sheet. They are the most common disturbance. They are often repetitive and may be a manifestation of a large-scale ULF oscillation.


      PubDate: 2012-12-15T09:30:44Z
       
  • Stratified Current Sheet During Plasma Sheet Thinning
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      The current sheet structure during the plasma sheet compression is studied for a one-dimensional Harris-type current sheet. We find that a stratified structure embedded in a thick plasma sheet is formed by taking into account the non-MHD effect. The global (smoothed) current density is enhanced during the plasma sheet compression, but the neutral sheet current does not necessarily increase. The current density can be reduced than the initial state before the plasma sheet compression. This kinetic current sheet structure may play an important role on the onset mechanism of substorms in magnetotail.


      PubDate: 2012-12-15T09:30:44Z
       
  • Bifurcated Thin Current Sheets in the Earth's Magnetosphere: Comparison of
           Model and “In Situ” Observations
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      A self-consistent analytical theory of thin current sheets (TCSs) is used to investigate their fine structure in the Earth's magnetotail at various stages of temporal evolution. The model is based on the solution of Grad-Shafranov type equations under quasi-adiabatic (QA) approximation. Quasi-adiabaticity allows the construction of an average equilibrium, assuming the conservation of QA invariant of motion Iz, and then the investigation of its slower evolution due to lz- diffusion. This diffusion leads to a gradual trapping of transient and unbounded (or the so called Speiser orbit) particles into orbits trapped in the vicinity of the sheet midplane. It is found that the cross-tail current of such newly trapped population is opposite to the one from transient Speiser orbits and eventually flattens the profile of the magnetic field cB near the midplane. As a result profile Bz(z) acquires a complex concave shape instead of a simple linear one, a characteristic of Harris equilibrium. The corresponding TCS cross-tail current profile attains a “double humped” shape, which can be a typical characteristic of TCS during a major part of its “life cycle”. This process of current sheet deterioration by quasi-trapped plasma may finally lead to TCS disruption. The results of numerical modeling are compared with Geotail and Cluster observations of double-humped (also referred to as "bifurcated") current sheets in the Earth's magnetotail. The observables predicted by our QA model and the conditions under which they are expected to be observed by Geotail, Cluster and other spacecraft are discussed.


      PubDate: 2012-12-15T09:30:44Z
       
  • Instability at the Leading Edge of a Reconnection Jet
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      In a transient reconnection process, the leading edge of the reconnection jet pushes and compresses the plasma standing ahead of it. This causes curved magnetic field lines and a strong pressure gradient to develop at the edge. It implies that the leading edge of the jet could be unstable to the ballooning instability. We studied this situation by three-dimensional MHD simulations and clarified that the interface indeed becomes unstable. The leading edge on the current sheet plane is deformed into a wavy shape and then to a mushroom-like pattern subsequently. The growth rate of the instability is controlled by the wavelength in the current-wise direction with a shorter wavelength mode growing faster. The dispersion curve obtained from a series of simulations is given.


      PubDate: 2012-12-15T09:30:44Z
       
  • Solar Flares and Magnetic Reconnection
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Recent studies by the author and his colleagues on solar flares based on the magnetic reconnection model are reviewed. The studies have been done mainly by using the data sets of space-craft observations and super-computer simulations. The covered topics are an EUV observation of reconnection inflows, MHD simulations of the reconnection model, and a microwave observation of freely-streaming high-energy electrons. The universal scaling law to explain the relation of the temperature and the emission measure of the solar/stellar flares is also shown.


      PubDate: 2012-12-15T09:30:44Z
       
  • Supersonic and Subsonic Expansion Acceleration Mechanisms in Fast Magnetic
           Reconnection
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      The thermodynamic expansion acceleration mechanism associated with the fast magnetic reconnection is studied by two-dimensional magnetohydrodynamic (MHD) simulations and the Rankine Hugoniot analysis. In the acceleration mechanism caused in the reconnection jet region, the jet generated by a pair of slow shocks can be further accelerated by the expansion and propagation of the plasmoid formed by the reconnection process. It is remarkable that the resulting jet can exceed the Alfven speed measured in the upstream magnetic field region. This acceleration mechanism is classified into supersonic and subsonic cases. Either of those cases occurs depending on the upstream field conditions of the jet. The former is similar to the Parker's solar wind acceleration mechanism, which includes two-dimensional expansion process, but the latter is basically one-dimensional expansion process. This paper consists of two topics. Firstly, the upstream field conditions required to cause the supersonic case is shown. Secondly, it is shown that the plasma expansion acceleration in the supersonic case is stronger than the subsonic case because the supersonic case has the circulating enhancement mechanism of the expansion process while the subsonic case does not.


      PubDate: 2012-12-15T09:30:44Z
       
  • Computer Simulations on the Spontaneous Fast Reconnection Evolution in
           Three Dimensions
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      The dynamics of large-scale magnetic loop in three dimensions is studied by MHD simulations. The spontaneous fast reconnection model is used in this study. In this model, the fast reconnection evolves by the positive feedback between microscopic anomalous resistivities and macroscopic reconnection flows. It is demonstrated that even in the general three-dimensional situation, once a current-driven anomalous resistivity is ignited in a local region in the current sheet, the fast reconnection mechanism spontaneously evolves explosively by such positive feedback. It is remarkable that a fast shock builds up ahead of the magnetic loop in a very limited extent, since the three dimension fast reconnection jet strongly converges toward the magnetic loop top as in the two-dimension case.


      PubDate: 2012-12-15T09:30:44Z
       
  • Effects of guide field in three-dimensional magnetic reconnection
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We have studied by MHD simulations the effects of the guide field in three-dimensional magnetic reconnection. The guide field is introduced by adding a constant By component Byo to the anti-parallel reconnecting component Bx = tanh(z). An ad-hoc anomalous resistive region, which facilitates the study of reconnection in MHD, is assumed to have a finite extent in the ydirection and this gives rise to a three-dimensional situation. It is shown that the guide field makes the U-shaped reconnected field lines as well as the reconnection jet to be inclined from thezaxis. The guide field also acts as an obstacle to the jet and this effect produces a pair of helical streamlines in the jet leading part. Time series data from a virtual spacecraft that encounters or skims the jet leading part are found to show good agreement with the observed FTE signatures on either side of the dayside magnetopause.


      PubDate: 2012-12-15T09:30:44Z
       
  • Formation of Thin Electron Current Layer Associated with Lower Hybrid
           Drift Instability and its Relation to Quick Reconnection Triggering
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We have recently found that a quick triggering of magnetic reconnection in an ion-scale current sheet is possible. For the quick triggering of magnetic reconnection, the lower hybrid drift waves excited at the edges of the current sheet is indispensable. This wave excitation brings about formation of a thin magnetic neutral layer sustained by accelerated electrons, and this thin layer is subject to the quick reconnection. We found that the electron acceleration process is strongly coupled with the non-linear evolution of the lower hybrid drift instability. The inductive electric field, which is generated through the change of the current profile, can efficiently accelerate meandering electrons around the magnetic neutral layer. As a result, electric current in the thin layer is mostly carried by non-adiabatic electrons. The production of non-adiabatic electrons is playing a crucial role in making the quick triggering available.


      PubDate: 2012-12-15T09:30:44Z
       
  • Geotail Study of Comparison between the Double-Probe Electric Fields and
           the Convection Electric Fields in the Distant Tail
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      The double probe technique is one of the standard techniques for in situ DC electric field measurements in tenuous plasmas, but it is known for its sensitiveness to the plasma environment around a spacecraft. In the present study we compare the double-probe electric fields obtained by Geotail/EFD-P with the convection electric fields - V× Bin various regions of the distant tail. We have found that the sensitivity (effective length of the double probes) varies as a function of the spacecraft potential, and the offset weakly depends on the electron temperature of ambient plasma. Using this result, an empirical calibration formula for the double-probe electric fields is obtained.


      PubDate: 2012-12-15T09:30:44Z
       
  • Magnetic Reconnection in the Magnetotail: Review of the Japanese
           Contribution with the Spacecraft Geotail
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      This paper reviews the Japanese contribution to our current understanding of magnetic reconnection with the spacecraft Geotail. Past spacecraft observations have examined mainly the MHD characteristics of magnetic reconnection in the Earth's magnetotail, whereas Geotail has revealed various characteristics of magnetic reconnection at the kinetic level as well as the MHD level. At the MHD level, the role of magnetic reconnection in substorm physics is studied. It is firmly established that magnetic reconnection for substorm onsets takes place in the spatially limited region in the premidnight magnetotail at radial distances of 20–30 RE. Geotail observations provide strong evidence that reconnection observations in the magnetotail precede common substorm indicators on the ground. At the kinetic level, ion dynamics in magnetic reconnection is examined, and Hall physics (ion- electron decoupling) is confirmed first in the vicinity of the magnetic reconnection site.


      PubDate: 2012-12-15T09:30:44Z
       
  • Application of Spacecraft Potential to Investigate the Distribution of
           Low-Energy Plasma in Magnetosphere
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We have found that the spacecraft potential in the magnetosphere and the solar wind can be used to derive the electron number density of the plasma surrounding spacecraft. The relationship between the Geotail spacecraft potential and the electron number density as determined by the plasma wave observations in the solar wind and broader magnetosphere (except for the high-density plasmasphere) was investigated and an empirical formula correlating these values obtained. Using this empirical formula and plasma particle measurements, we have shown the distribution of low-energy plasma in the magnetosphere.


      PubDate: 2012-12-15T09:30:44Z
       
  • Lobe Trapped Continuum Radiation Generated in the Distant Magnetotail
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Lobe trapped continuum radiation (LTCR) has been observed by the plasma wave instrument (PWI) on-board the GEOTAIL spacecraft at frequencies as low as 1 kHz in the distant geomagnetic tail region. From the direction finding analysis with the wave form capture (WFC) data, the arrival directions of LTCR are almost parallel to the dawn-dusk direction. A 3-D ray tracing analysis shows that the initially radiated Earth-tail ray directions of LTCR are transformed into the dawn-dusk directions by the reflection at the cylindrical tail magnetopause. The propagation characteristics of LTCR can give us very important information on the macroscopic structure such as magnetotail flapping. By comparing the results of the direction finding with the 3-D ray tracing analysis, we find that the possible source regions for LTCR are located at the plasma sheet boundary layer away from the nominal tail axis and the low latitude boundary layer.


      PubDate: 2012-12-15T09:30:44Z
       
  • Whistler Mode Chorus Observed Around the Plasmapause During Magnetic
           Storms
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Drastic changes of relativistic electron population in the outer radiation belt during magnetic storms have been observed by many satellites. The relativistic electron flux decreases during a main phase of magnetic storm, and in some cases increases to above the prestorm level during the recovery phase. One of the plausible mechanisms of the relativistic electron enhancement during the recovery phase of magnetic storm is the wave-particle resonant diffusion by whistler mode chorus. In the present paper, we statistically studied chorus emissions observed by Akebono in the vicinity of the outer radiation belt associated with magnetic storms. In order to evaluate the contribution of whistler mode chorus to the relativistic electron enhancement, we performed direction finding analysis of the chorus using wave distribution function (WDF) method and quantitatively estimated the energies of whistler mode wave and relativistic electrons during recovery phase of magnetic storm.


      PubDate: 2012-12-15T09:30:44Z
       
  • Magnetospheric Active Wave Measurements
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      The magnetospheric community has conducted active wave measurements, which are made by radiating known signals to space and measuring the dispersion of the signals when propagating through magnetospheric plasma, for more than three decades. Because of the advances in space electronics and signal processing technology, active wave experiments can now cover a large dynamic range in frequency and be made in a large spatial range for versatile applications. They are becoming a promising new technique to probe the space plasma conditions. In this review we demonstrate the capability of magnetospheric sounding technique employed by the radio plasma imager (RPI) on board the IMAGE satellite. This new technique, combined with the mathematical density inversion algorithm, measures the plasma density in situat the satellite location and remotely and instantaneously along the magnetic field line from one hemisphere to the other down to as low as half an Earth radius (Re) in altitude. The technique has been formally validated. The database from the RPI active measurements covers all local times from 1.5 Re to 5 Re under different geomagnetic activities. Empirical models that are being developed specify the density as functions of radial distance, latitude, local time, distance along the field line from the earth's surface, solar wind conditions, geomagnetic indices, and other possible variables that affect the density distribution. The models can describe the statistical behaviors of the plasma distribution and can also provide snapshots of the plasma conditions on occasions. Dynamical processes that cause variations from the average models, such as depletion/refilling processes and plasma convection tail formation, can be studied. When applied to multiple satellites, or a constellation of satellites, the active wave measurements also make it possible for magnetospheric tomography, in which transmissions and reception of various waves within the constellation are used to derive the plasma density and magnetic field component in the constellation plane.


      PubDate: 2012-12-15T09:30:44Z
       
  • 2fpRadio Source in Geotail Observations and Numerical Simulations
           ~Microscopic View~
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We have studied several topics related to the 2f pradiation generated in the terrestrial electron foreshock. Our investigation started from the macroscopic geometry of the radio source, and is expanding to the microscopic processes. In this paper, we present a summary of latter studies, especially about the generation mechanism of electrostatic and electromagnetic 2f pwaves and the electron acceleration at the quasi-perpendicular shock.


      PubDate: 2012-12-15T09:30:44Z
       
  • Dayside Outer Magnetosphere ULF Waves Observed by Geotail
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      On the basis of our recent studies (Sakurai, 1999a, 1999b and 2001) the present paper is intended to review oscillation and propagation characteristics of Pc 3 and Pc 5 ULF waves observed near the dayside magnetopause by the Geotail satellite. These characteristics are studied on the basis of the simultaneous observations of the magnetic and electric fields, and low energy plasmas measured with the excellent instruments on board the satellite. The study reveals that the dominant ULF waves observed near the dayside magnetopause are Pc 3 and Pc 5 oscillations. The Pc 3 oscillations appear with a peak power around noon at the frequency of 25 mHz in the azimuthal component of the magnetic field. This frequency component shows clear resonant oscillations. In addition fast mode earthward propagation is recognized. The Poynting flux of Pc 3 waves is about 1-10 nW/m2on average, the strongest being along the magnetic field-line. Pc 5 oscillations are also dominant, and are observed mainly in the dawn and dusk-side flanks. They appear as clear oscillations in the radial component of the electric field, suggesting that resonant oscillations along the magnetic field-line are well established. The Poynting flux of Pc 5 can be estimated as 10 - 100 nW/m2in both directions across and along the magnetic field-line. This result suggests that Pc 5 wave energy is carried into both the ionosphere and the inner magnetosphere during an hour with the energy of 1010- 1013J, which is one or two orders of magnitude less than the substorm energy. By taking into account the continuous activation of ULF waves in the outer magnetosphere, these waves should play an important role in the energetics of the magnetosphere.


      PubDate: 2012-12-15T09:30:44Z
       
  • Compressional Variations Propagating in the Distant Tail Observed by
           Geotail on October 2, 1994
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Static pressure variations in the distant magnetotail lobe caused by the passage of a plasmoid are investigated. The traveling speed of the plasmoid is estimated to have been faster than the concurrent magnetosonic speed in the lobe. The magnetic field variation along the maximum variance direction was linearly related to the variation in the field strength, which suggests that a magneto-hydrodynamic compressional mode might have occurred. The propagation direction of the variation is determined from the background field direction and the maximum variance direction of the field. Shortly after the passage of the plasmoid, the relation between the field and velocity variations is consistent with the fast mode. Pressure variation in the fast mode was possibly generated in the trail of the plasmoid to restore equilibrium.


      PubDate: 2012-12-15T09:30:44Z
       
  • Relationship Between Plasma and Magnetic Field Parameters in the Distant
           Plasma Sheet
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Measurements of the magnetic field and low-energy plasma by Geotail have been used to study mean and instantaneous characteristics of plasma and magnetic field in the distant tail X = -(79-200) Reunder extremely quiet and weakly disturbed conditions. The analysis has been carried out separately for the tail lobes and the plasma sheet. A good consistency between variations of the plasma and magnetic parameters is observed only in the tail lobes, the correspondence being considered for appropriate components (VXand BY, VYand BY, VZand BZ). The distant plasma sheet seems to be constantly in regime of turbulence, i.e. such a regime when the magnetic field and plasma parameters are steadily subjected to fluctuations of different periods, the variations in magnetic field and plasma velocity being inconsistent in time. The mean values of V and B in the plasma sheet are not compatible with their instantaneous characteristics at all. The coefficient of diffusion across the plasma sheet, estimated from experimental data, is in harmony with predictions of theory for the plasma sheet with turbulence. The applicability of the frozen-in approximation to description of processes in the plasma sheet is discussed.


      PubDate: 2012-12-15T09:30:44Z
       
  • On Ion Properties within the Subsolar Magnetopause Current Layer under the
           Northward and Southward IMF
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      This paper describes the ion properties within the subsolar magnetopause current layer (MPCL) under the northward and southward IMF. This study was based on the magnetic field and plasma data measured by the GEOTAIL spacecraft on November 10, 1995 and January 3, 1996. An interesting signature of a “collimated” ion distribution was found under the southward IMF. This can be interpreted as evidence that the ions originating from the magnetosheath were distributed along the open field lines formed by the magnetic reconnection on the MPCL. Under the northward IMF the low energy ions were found to be coexisting (or mixing) with energetic magnetospheric ions on the outer edge of the magnetosphere. This result indicates that the LLBL existed under the northward IMF.


      PubDate: 2012-12-15T09:30:44Z
       
  • Influence of Solar Wind on Source of Ring Current Plasma
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      In the present study we aim to derive empirical equations relating source plasma of the ring current to the solar wind. We used the energy spectra at energies of 9-135 keV obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft. The plasma parameters (i.e., number density and temperature) of H+, O+, and He+were estimated by fitting the K-distribution function to the energy spectra in the region of a geocentric distance of 8.5–10.5 Reand magnetic local time of 2200-0200 hour. The results showed that the H+number density in the plasma sheet correlated with the solar wind density, while the O+and He+number density had no correlation with the solar wind parameters. Thus the origin of H+ions in the plasma sheet is thought to be the solar wind. O+and He+ions in the plasma sheet are expected to have different origin from the solar wind. It was also found that the temperature of H+, O+and He+has a good correlation with the solar wind velocity and that gradients of the derived empirical equations can be ordered by ion mass. This implies that ions are accelerated in a mass-dependent way.


      PubDate: 2012-12-15T09:30:44Z
       
  • Electron Inertia Effects in an MHD-Scale Kelvin-Helmholtz Vortex
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We study the electron inertial effects on an MHD-scale Kelvin-Helmholtz (K-H) vortex. An LLBL like situation, that is, an MHD/ion scale velocity shear layer collocated with a current layer, is set up and the evolution of an MHD/ion-scale K-H mode is followed. The magnetic field is assumed to be perpendicular to the flow and the simulation plane. For a duskside-like situation, it is shown that smaller vortices appear within the MHD-scale parent K-H vortex. For the reasonable initial condition we adopt here, these appear only when the electron inertia effects are turned on. The smaller vortices grow as they are entrained into the center of the larger vortex and eventually destroy the parent's vortex pattern. For a dawnside situation, in contrast, such a decay process is not observed. We will present detailed analyses revealing the nature of these more or less surprising results.


      PubDate: 2012-12-15T09:30:44Z
       
  • Geotail Observations of the Cold Plasma Sheet on the Duskside Magnetotail
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We have studied signatures of the cold plasma sheet in the duskside near-earth magnetotail with the Geotail data. In the duskside plasma sheet, cold plasmas are found 3-4 hours after the northward turning of the interplanetary magnetic field. The cold plasma sheet with two-temperature ions is often found on the duskside, while cold plasma sheet with one-temperature are also found on the duskside when northward interplanetary magnetic field continues for a very long interval (more than several hours). We discuss the development and evolution of the cold plasma sheet on the duskside.


      PubDate: 2012-12-15T09:30:44Z
       
  • The Dawn-Dusk Asymmetry in Magnetosheath and the Leakage of Energetic
           Electrons: The Geotail Observation
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We statistically and systematically studied the dawn-dusk magnetosheath asymmetry by using both thermal/middle energy electrons (≤ 40 keV: LEP) and energetic electrons (≥ 38 keV: EPIC) experiments onboard the Geotail spacecraft. We found the dawn-dusk magnetosheath asymmetry of energetic electrons distribution (≥ 38 keV), while the clear asymmetry could not be observed, for the lower energy electrons. It was also found that energetic electrons flux did not strongly change across the magnetopause as compared with that of the thermal/middle energy electrons in the dawn side magnetopause, and that the intensity of the energetic electrons increases with going towards the dawn side magnetopause from the bow shock. Those results suggest that energetic electrons leak out of magnetosphere into magnetosheath.


      PubDate: 2012-12-15T09:30:44Z
       
  • The Structure of the Plasma Sheet Under Northward IMF
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      The structure of the plasma sheet under northward IMF is studied by data from the Geotail spacecraft. The plasma sheet is known to become cold and dense (T < 2 keV, n > 1 cm-3) during extended northward IMF periods. We show that such cold-dense ions (CDIs) appear at itYgsm>10 Re , that is, 10Re off the tail axis to both flanks. CDIs on the dawnside have higher temperatures and some reach the upper-limit of 2 keV that we use to select CDIs. These CDIs having the highest temperature are distributed at the dawnside plasma sheet inner-edge (R < 15 Re ) and is connected to the hot-dense ions (HDIs: T >2 keV, n >1 cm-3) in the further inner region. A survey shows that HDIs under nominal solar wind dynamic pressure appear mostly in the dawnside inner-magnetosphere during extended northward IMF intervals. Both results point to the idea that HDIs are the inner-magnetosphere extension of dawnside CDIs, while such a partner to the duskside CDIs cannot be identified. This structure of the plasma sheet suggests that there is significant dawn-dusk asymmetry in heating and transport in the magnetotail under northward IMF.


      PubDate: 2012-12-15T09:30:44Z
       
  • Cluster: New View on the Boundaries of the Magnetosphere
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      After 1.5 years of operations, the Cluster mission is fulfilling successfully his scientific objectives. The main goal of the Cluster mission is to study, in three dimensions, the small-scale plasma stuctures in the key plasma regions in the Earth environment: solar wind and bow shock, magnetopause, polar cusps, magnetotail, and auroral zone. The relative distance between the four spacecraft is varied, according to the scientific region, between 100 and 18000 km during the course of the mission. During the first phase of the mission, the four spacecraft crossed the exterior cusp (Feb. 2001) with an inter-spacecraft distance of 600 km, during the second phase they were in the magnetotail (Aug. 2001) with 2000 km inter-spacecraft distance. Since January 2002, the four spacecraft are again in the cusp/solar wind with the smallest inter-spacecraft distance of 100 km and in June 2002, in the tail, this distance will be increased to 4000 km.. A few results obtained during the first 1.5 years of operation are presented as well as the access to data through the Cluster Science data System and the future operations for the extended mission.


      PubDate: 2012-12-15T09:30:44Z
       
  • Geotail, Polar, and Wind Observations of Auroral Kilometric Radiation
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Auroral kilometric radiation (AKR) is the plasma wave/radio phenomenon most clearly associated with substorms and increased geomagnetic activity. The GEOTAIL and POLAR Plasma Wave Instruments (PWI) both included sweep frequency receivers that had an upper frequency limit of 800 kHz and the WIND WAVES Thermal Noise Receiver (TNR) and Radio Receiver Band 1 (RAD1) went to 256 kHz and 1024 kHz, respectively. We have thus been able to observe the majority of the AKR spectrum in better detail than with earlier instrumentation and many important new discoveries have been made. Terrestrial low frequency (LF) bursts are a part of AKR observed during strong substorms. Although a limited portion of the LF burst spectrum is often detected on the dayside of the Earth and in the upstream solar wind, the complete spectrum is most frequently detected by spacecraft in the night side magnetosphere or geomagnetic tail. Frequently these observations show that the LF bursts have a tapered tail centered on the present or recent past solar wind plasma frequency. We have found that on the dayside and in the upstream solar wind the high frequency AKR is detected during LF burst events only if the path from the AKR source is not blocked by the earth or dense plasmasphere. POLAR observations from high over the AKR source region show that the AKR increases in intensity and its lower frequency limits decrease when LF bursts are observed indicating that the AKR source region is expanding to higher altitudes. Frequently the upper frequency limit also increases indicating that the source region is then also expanding to lower altitudes. Data from both satellite and ground-based experiments show that the LF bursts are well correlated with expansive phase onsets and occur during very geomagnetically-disturbed periods. High resolution (in both time and frequency) data from the POLAR Wide Band Receiver have yielded exciting data on the fine structure of AKR as well as details on the structure of LF bursts.


      PubDate: 2012-12-15T09:30:44Z
       
  • Occultations of Auroral Kilometric Radiation in the Vicinity of the Earth
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Auroral kilometric radiation (AKR) occultations in the vicinity of the Earth are studied using two observations by GEOTAIL and POLAR. We compared the dynamic spectra of both satellites for eight months paying attention to times and frequencies at which AKR is observed simultaneously. Then, we carefully examined the AKR illumination regions using the POLAR two-month orbit data. Two distinct regions where the AKR is occulted are found during the period. One is the region on the night side of the Earth, where the AKR does not propagate at frequencies >400 kHz. The other region is in the vicinity of the plasmapause, on both the day and night side of the Earth.


      PubDate: 2012-12-15T09:30:44Z
       
  • The Loading-Unloading Process in the Magnetotail During a Prolonged Steady
           Southward IMF Bz Period
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      The interplanetary magnetic field (IMF) Bz was continuously southward for 16 hours on April 18, 2002. During this period, the spacecraft Geotail was in the northern tail lobe at radial distances of 24–28 RE, and it observed sequences of increasing and decreasing in the magnetic field intensity in association with substorms. The increases in the magnetic field took approximately 40 minutes, and the decreases took approximately 50 minutes. The time scale of the increase is consistent with the typical time scale of the substorm growth phase, which usually begins with a clear southward turn of the IMF Bz. The time scale of the decrease agrees well with the typical time scale of the substorm expansion phase, although the substorm expansion phase frequently starts with a northward turn of the IMF Bz. It is suggested that the magnetotail has an intrinsic time scale for the loading-unloading process for substorms irrespective of the IMF Bz conditions.


      PubDate: 2012-12-15T09:30:44Z
       
  • Magnetotail Deflation: Geotail Observations
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      A sudden decrease in the total pressure in the mid-magnetotail associated with a substorm was designated as magnetotail deflation by Nakai and Kamide (2003). Utilizing UVI auroral image data from Polar and magnetic field and particle data from Geotail, a typical example of the magnetotail deflation is examined in detail. A series of auroral images during this event show that a precursory breakup first occurred, which was then followed by a major breakup. Although the foot point of Geotail was mapped within the auroral bulge formed during the precursory breakup, only minor changes in the magnetic field were observed at Geotail. In contrast, a clear magnetotail deflation occurred in conjunction with the major breakup. It is suggested that the major breakup is preferably initiated in the mid-tail premidnight region.


      PubDate: 2012-12-15T09:30:44Z
       
  • Comparison of Energetic Ion Composition between Ring Current and Plasma
           Sheet
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We calculated the energy density of H+, He+, and O+ions in the plasma sheet during the development of a magnetic storm, using energetic (9–210 keV) particle flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft. We found that the energy density ratio of O+/H+stayed at ~0.1 before storms, but increased as storms developed, reaching 0.5–1.0 at a peak of storms. The energy density ratio of He+/H+was rather constant at 0.01–0.02. These results are comparable with those in the outer ring current reported by the previous studies. This implies that the ions of ionospheric origin (O+and He+) are transported to the ring current through the plasma sheet.


      PubDate: 2012-12-15T09:30:44Z
       
  • Ten Years of Geotail and its Current Status: A Brief Summary
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Since its launch in 1992, GEOTAIL has extensively surveyed the magnetotail with a full set of plasma and field instruments over a wide range of distances from 9 Re to 220 Re away from the Earth by means of a sophisticated orbit strategy. In the first two years, the orbit was optimized to explore the distant tail, and thereafter was changed to study substorm processes in the near-Earth tail region. The near-tail orbit has also facilitated exploration of the dayside outer magnetosphere, the magnetopause, the magnetosheath, and the bow shock, as well as the upstream solar wind. GEOTAIL observations have revealed a number of new phenomena in these regions, and as of the end of 2003, about 600 papers have been published in refereed journals. Recent GEOTAIL studies have significantly advanced our understanding of the structure and formation of thin current sheets in the mid-tail plasma sheet during substorms, and have elucidated new kinetic aspects of magnetic reconnection. GEOTAIL has operated far beyond the designed mission life of three and half years. Most of the onboard instruments are still functioning well, and it is expected that GEOTAIL will continue to generate scientifically useful data.


      PubDate: 2012-12-15T09:30:44Z
       
  • Difference between Earthward and Tailward Flows in Their Dependences on
           Geomagnetic and IMF Conditions
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Earthward and tailward perpendicular fast flows in the plasma sheet were studied and their differences in response to geomagnetic conditions and to interplanetary magnetic field (IMF) conditions are discussed. We first identified the plasma sheet from 3.5 years of Geotail plasma and magnetic filed observations between 8 and 32 RE down the tail. We then studied occurrence rates of fast flows during geomagnetically quiet and active intervals as identified by Kp and ASY indices, and during northward and southward IMF intervals. As a result, both earthward and tailward flows were observed more often during active or southward IMF intervals than during quiet or northward IMF intervals, as expected. On the other hand, we found that there is a difference between earthward and tailward flows: Dependences on geomagnetic conditions are more evident in tailward flows than in earthward flows. We further discuss that tailward flows indicate the substorm expansion phase better than earthward flows do.


      PubDate: 2012-12-15T09:30:44Z
       
  • Preface
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16




      PubDate: 2012-12-15T09:30:44Z
       
  • Weak Langmuir Turbulence
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Langmuir wave turbulence generated by a beam-plasma interaction has been studied since the early days of plasma physics research. In particular, mechanisms which lead to the quasi power-law spectrum for Langmuir waves and the superthermal electron tail population have been sought. Meanwhile, the generation of harmonic Langmuir waves has been known for some time, in both laboratory and computer-simulated experiments. However, the phenomenon has not been adequately explained in terms of theory, nor has it been fully characterized by means of numerical simulations. In this paper, a theory of harmonic Langmuir wave generation is put forth and tested against the Vlasov simulation results. It is found that the harmonic Langmuir mode spectra can indeed exhibit quasi power-law feature, implying a multi-scale structure in both frequency and wave number space spanning several orders of magnitude. Moreover, the new hyper-diffusion process is shown to be responsible for the generation of superthermal electron population. These findings indicate that the harmonic excitation process and nonlinear hyper-diffusion may be important in understanding the high-frequency turbulent processes in plasmas.


      PubDate: 2012-12-15T09:30:44Z
       
  • New Non-Stochastic Acceleration in Multi-Component Plasmas
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We discuss a non-stochastic particle acceleration mechanism under the cyclotron resonance with two electromagnetic ion-cyclotron (EMIC) waves. We find that the strong ion acceleration occurs in multi-component plasma if a heavy ion can resonate with both the EMIC wave near the cutoff frequency and the other EMIC wave with the Alfven velocity. The particle is preferentially accelerated perpendicular to the ambient magnetic field, and the acceleration rate is simply expressed by Vi /VA =(Ei /Bo )(cc/VA )Ωt, where BQ is the ambient magnetic field, V(i)is a velocity perpendicular to the ambient field, VA is Alfven velocity, c is the light speed,Ω is a cyclotron frequency,tis time and E(i)is electric field of the EMIC wave near the cutoff frequency.


      PubDate: 2012-12-15T09:30:44Z
       
  • Geotail Observations of Solar Wind and Interplanetary Phenomena
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      In this review, based on the recent GEOTAIL observation I will cover three broad topics, bow shock and foreshock phenomena, interplanetary phenomena, interstellar medium, and solar flare effects. (1) I will concentrate on the physics of energetic diffuse ions found in the bow shock and foreshock regions, and discuss three subtopics, namely, the origin of these ions, their nonlinear reaction to the shock structure, and their transport process from the region upstream of the nose bow shock to the predawn foreshock region. (2) I will discuss two subtopics about propagating interplanetary shocks ahead of coronal mass ejecta: It is shown that in addition to the well-known diffusive ionacceleration at these shocks there sometimes occurs diffusive electronacceleration. The nonlinear reaction of the accelerated particles, the same phenomenon as found in the bow shock case, is identified at least once in an moderately strong interplanetary shock. (3) In addition to the above 'normal' bow shock/interplanetary phenomena, CEOTAIL has provided unique 3D phase space information on a 'stranger', namely pickup He+ions of local interstellar medium origin. (4) I will then describe unexpected direct observations of solar flare signals on GEOTAIL: the spiky enhancements (duration ~ several minutes) of the sunward electric fields and background counts of plasma detectors, both of which occur concurrently with the peaks of large solar X-ray flares.


      PubDate: 2012-12-15T09:30:44Z
       
  • Whistler Waves in Upstream Region of Interplanetary Shocks
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Whistler waves are considered to play an important role in the electron dynamics for the collisionless shock formation process at interplanetary shocks (IPSs). In this report, we analyze IPS events observed by GEOTAIL on 21 February 1994 and 15 July 2000, focusing on whistler wave properties in their upstream region extending the previous work of Shimada et al. (1999). In both events, we have identified the existence of whistler mode waves in the upstream region of the IPS as well as the tendency of the intensity increase toward the shock front. At the same time we have found the detailed features differing between these events: While the intermittent but clear wave bursts were found on 21 February 1994 event, the waves were more or less continuous on 15 July 2000 event.


      PubDate: 2012-12-15T09:30:44Z
       
  • Wave-Particle Interaction in the Bastille Shock of Year 2000
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      Diffusive shock acceleration process is regarded as one of the most important processes for astrophysical particle acceleration. We treat an ESP (energetic storm particle) event associated with an interplanetary shock (IPS) arrived at 1AU about 28 hours after a large flare/CME event happened in 14 July 2000 (known as the Bastille event). Using the magnetic field data from Geotail (X=24.9 Re, Y=7.4Re, Z=-1.8Re), and flux data of protons (~ several×102keV) from SOHO (X=2.2Re, Y=-67.8Re, Z=12.3Re), we study the wave-particle interaction in the upstream region of this IPS.


      PubDate: 2012-12-15T09:30:44Z
       
  • Particle-Field Dynamics in the Shock Transition Region
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We carried out particle-in-cell simulation to investigate the mechanism for steady and unsteady shock front formation depending on Mach number (MA) and plasma β. When even under the same MA, depending on β, the electric and magnetic field structures in the shock transition region (STR) are much different. At lower β or/and higher MAcondition, the shock front tends to be unsteady and electrons play more important role in the shock dissipation process through two-stream instability.


      PubDate: 2012-12-15T09:30:44Z
       
  • Electrostatic Quasi-Monochromatic Waves Downstream of the Bow Shock:
           Geotail Observations
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      The downstream region of the bow shock is a very turbulent region. Intense electrostatic waves in a wide frequency range can be observed. They are expected to be generated by electron beams which are accelerated in the transition re- gion of the bow shock. In the present paper, we focus on the Electrostatic Quasi-Monochromatic (EQM) waves which are mostly observed in the downstream region. Similar waves have been reported by other spacecraft observations. However, their generation mechanism, energy source, and wave mode are still unclear. Geotail observations show good correlation of the EQM waves with the cold electron beam-like component which correspond to the electrons accelerated in the bow shock. In the present paper, we introduce the characteristics of the EQM waves and discuss their correlation with electron velocity distributions.


      PubDate: 2012-12-15T09:30:44Z
       
  • Geomagnetic Activity Dependence of Occurrence Probability and Spatial
           Distribution of Upstream Events
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We investigated upstream events observed by the ion composition system (ICS) sensor of the energetic particles and ion composition (EPIC) instrument on board the Geotail spacecraft. We examined how occurrence probability and spatial distribution of upstream events depend on the geomagnetic activity. The results showed that the upstream events were observed more frequently in the dawn side during intense geomagnetic activity in particular. We also analyzed carbon-nitrogen-oxygen ions during the upstream events. From the above results we discuss origin of the upstream energetic ions.


      PubDate: 2012-12-15T09:30:44Z
       
  • Enhancement of Sunward Double-Probe Electric Fields Observed by Geotail
           During the Solar Flare
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      We report significant enhancement of sunward electric field, EX, detected by GEOTAIL during the November 24, 2000 flare (X2.3/2B). We found a good correlation of the time profile of EXwith that of hard X-ray (larger than 23keV) flux observed by YOHKOH. In addition, we have found 100 events that show similar enhanced double-probe EXin association with hard X-ray flares for which results of a statistical study are also presented.


      PubDate: 2012-12-15T09:30:44Z
       
  • Quest for Waves Excited by Interstellar Helium Pickup Ions
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16

      ‘Torus-like’ velocity distribution of the helium pickup ions of interstellar origin has directly been observed by the GEOTAIL spacecraft. These distributions possess a free energy to excite an electromagnetic wave owing to the anisotropic distribution. Although there have been several reports on the quest of waves induced by hydrogen pickup ions based on the observation beyond ~4AU, there has been no report on the waves of helium pickup ions. In this brief report, power spectrum analysis for helium pickup ion events obtained by GEOTAIL is carried out to search for such a wave excitement. We report, however, that the expected wave could not be found owing to the low density of the helium pickup ions at 1AU. The upper limit of the waves is determined to be 24.3% above the background level.


      PubDate: 2012-12-15T09:30:44Z
       
  • Author Index
    • Abstract: 2005
      Publication year: 2005
      Source:COSPAR Colloquia Series, Volume 16




      PubDate: 2012-12-15T09:30:44Z
       
  • Preface
    • Abstract: 2002
      Publication year: 2002
      Source:COSPAR Colloquia Series, Volume 15




      PubDate: 2012-12-15T09:30:44Z
       
  • Scientific organising committee
    • Abstract: 2002
      Publication year: 2002
      Source:COSPAR Colloquia Series, Volume 15




      PubDate: 2012-12-15T09:30:44Z
       
 
 
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