Annales Geophysicae (ANGEO)
[SJR: 1.176] [H-I: 63] [3 followers] Follow
Open Access journal
ISSN (Print) 0992-7689 - ISSN (Online) 1432-0576
Published by European Geosciences Union [8 journals]
- Global distribution of vertical wavenumber spectra in the
lower stratosphere observed using high-vertical-resolution temperature
profiles from COSMIC GPS radio occultation
Abstract: Global distribution of vertical wavenumber spectra in the lower stratosphere observed using high-vertical-resolution temperature profiles from COSMIC GPS radio occultation
Noersomadi and T. Tsuda
Ann. Geophys., 34, 203-213, doi:10.5194/angeo-34-203-2016, 2016
We studied the characteristics of gravity waves in the lower stratosphere using high-vertical-resolution COSMIC GPS-RO temperature profiles retrieved by the FSI method. We analyzed vertical wavenumber spectrum of the normalized temperature perturbations and calculated the wave potential energy in the wavelength ranges from 0.5 to 3.5 and 0.5 to 1.75 km. We investigated the correlation between the spectral parameters with topography and the background mean zonal winds.
- Impact of variational assimilation using multivariate background error
covariances on the simulation of monsoon depressions over India
Abstract: Impact of variational assimilation using multivariate background error covariances on the simulation of monsoon depressions over India
M. Dhanya and A. Chandrasekar
Ann. Geophys., 34, 187-201, doi:10.5194/angeo-34-187-2016, 2016
The three-dimensional variational technique (3DVar) is a popular technique used for data assimilation. Background error covariance (BEC) influences the performance of 3DVar technique. In this study, two formulations of BEC, namely the cv5 and cv6 options in the 3DVar assimilation in the Weather Research and Forecasting (WRF) model, are compared. It is found that the formulation of BEC impacts the analysis. Utilising the cv6 option moderately improves the simulation of monsoon depressions.
- Modeling of ion dynamics in the inner geospace during enhanced
Abstract: Modeling of ion dynamics in the inner geospace during enhanced magnetospheric activity
C. Tsironis, A. Anastasiadis, C. Katsavrias, and I. A. Daglis
Ann. Geophys., 34, 171-185, doi:10.5194/angeo-34-171-2016, 2016
We investigate the effect of magnetic disturbances on the ring current buildup and the dynamics of the current systems in the inner geospace by means of numerical simulations of ion orbits during enhanced magnetospheric activity. For this purpose, we developed a particle-tracing model that solves for the ion motion in a dynamic geomagnetic field and an electric field due to convection, corotation and Faraday induction and which mimics reconfigurations typical to such events. The kinematic data of the test particles is used for analyzing the dependence of the system on the initial conditions, as well as for mapping the different ion species to the magnetospheric currents. Furthermore, an estimation of Dst is given in terms of the ensemble-averaged ring and tail currents. The presented model may serve as a tool in a Sun-to-Earth modeling chain of major solar eruptions, providing an estimation of the inner geospace response.
- Generation of a severe convective ionospheric storm under stable
Rayleigh–Taylor conditions: triggering by meteors?
Abstract: Generation of a severe convective ionospheric storm under stable Rayleigh–Taylor conditions: triggering by meteors?
M. C. Kelley and R. R. Ilma
Ann. Geophys., 34, 165-170, doi:10.5194/angeo-34-165-2016, 2016
This manuscript presents a novel and interesting hypothesis about the seeding of equatorial spread F irregularities by meteors. Based on radar experiments, the study postulates that the triggering of these irregularities occurs even under very stable ionospheric conditions. The article demonstrates significant work on the relationship between meteors and F region irregularities at equatorial latitudes. The novel mechanism can encourage the ionospheric community to test this hypothesis.
- A statistical study over Europe of the relative locations of lightning
and associated energetic burst of electrons from the radiation belt
Abstract: A statistical study over Europe of the relative locations of lightning and associated energetic burst of electrons from the radiation belt
F. Bourriez, J.-A. Sauvaud, J.-L. Pinçon, J.-J. Berthelier, and M. Parrot
Ann. Geophys., 34, 157-164, doi:10.5194/angeo-34-157-2016, 2016
The purpose of our paper was to provide a statistical study of one of the interactions between lightning and particles occurring above thunderstorms. In our case, the satellite DEMETER was able to measure the energy of both particles and lightning. By correlating those measurements with lightning detection, we were able to determine the position of the causative lightning. The aim of this research was mainly to prepare the next spacecraft mission, which will study thunderstorms from space.
- Physical origin of pickup currents
Abstract: Physical origin of pickup currents
V. M. Vasyliūnas
Ann. Geophys., 34, 153-156, doi:10.5194/angeo-34-153-2016, 2016
So-called pickup electric currents, associated with the ionization of neutral particles in the presence of a flowing plasma, are conventionally described as produced directly by differential displacement of ions and electrons as the result of acceleration and gyromotion under the action of the electric field E = −V × B∕c. This is not the appropriate physical description for the case when the electron inertial length of the background plasma is small in comparison with the spatial scale of the system. The pickup process in this case does not directly produce a current, except for a small transient on the electron-gyroperiod timescale, which then decays exponentially at the ionization (momentum-loading) rate, as can be shown by an explicit solution of the equations. Rather, the plasma is first slowed down by the momentum loading; the spatially inhomogeneous velocity change then leads to a perturbation of the magnetic field, and the curl of the perturbed field is the current. The timescale for the development of the pickup current is not the ion gyroperiod (as the conventional description might suggest) but rather the Alfvén wave travel time over the spatial scale of the inhomogeneity.
- A method to improve the utilization of GNSS observation for water
Abstract: A method to improve the utilization of GNSS observation for water vapor tomography
Y. B. Yao, Q. Z. Zhao, and B. Zhang
Ann. Geophys., 34, 143-152, doi:10.5194/angeo-34-143-2016, 2016
Existing water vapor tomographic methods use Global Navigation Satellite System (GNSS) signals penetrating the entire research area while they do not consider signals passing through its sides. To solve this issue, an approach which uses GPS data with both signals that pass the side and top of a research area is proposed. The advantages of proposed approach include improving the utilization of existing GNSS observations and increasing the number of voxels crossed by satellite signals.
- Electron/positron measurements obtained with the Mars Science Laboratory
Radiation Assessment Detector on the surface of Mars
Abstract: Electron/positron measurements obtained with the Mars Science Laboratory Radiation Assessment Detector on the surface of Mars
J. Köhler, R. F. Wimmer-Schweingruber, J. Appel, B. Ehresmann, C. Zeitlin, D. M. Hassler, G. Reitz, D. E. Brinza, S. Böttcher, E. Böhm, S. Burmeister, J. Guo, A.-M. Harri, H. Kahanpää, J. Krauss, H. Lohf, C. Martin, D. Matthiä, A. Posner, and S. Rafkin
Ann. Geophys., 34, 133-141, doi:10.5194/angeo-34-133-2016, 2016
The Radiation Assessment Detector (RAD), on board the Mars Science Laboratory (MSL) rover Curiosity, measures the energetic charged and neutral particles and the radiation dose rate on the surface of Mars. In this work we compare predicted electron/positron spectra with the signal measured by RAD. We find that the RAD electron/positron measurements agree well with the spectra predicted by Planetocosmics.
- Modulation of surface meteorological parameters by extratropical
planetary-scale Rossby waves
Abstract: Modulation of surface meteorological parameters by extratropical planetary-scale Rossby waves
K. Niranjan Kumar, D. V. Phanikumar, T. B. M. J. Ouarda, M. Rajeevan, M. Naja, and K. K. Shukla
Ann. Geophys., 34, 123-132, doi:10.5194/angeo-34-123-2016, 2016
The link between upper-tropospheric planetary-scale Rossby waves and surface meteorological parameters is examined. The propagating Rossby waves along with undulations in the subtropical jet create convergence and divergence regions in the mid-troposphere. The surface relative humidity, wind speeds, and temperature are synchronized with the phase of the propagating Rossby waves. The present study finds important implications for medium-range forecasting through Rossby wave propagation.
- The formation of multiple layers of ice particles in the polar
summer mesopause region
Abstract: The formation of multiple layers of ice particles in the polar summer mesopause region
H. Li, J. Wu, and Z. Zhou
Ann. Geophys., 34, 117-122, doi:10.5194/angeo-34-117-2016, 2016
This paper presents a two-dimensional theoretical model to study the formation process of multiple layers of small ice particles in the polar summer mesosphere as measured by rockets and associated with polar mesosphere summer echoes (PMSE). The proposed mechanism primarily takes into account the transport processes induced by gravity waves through collision coupling between the neutral atmosphere and the ice particles. Numerical solutions of the model indicate that the dynamic influence of wind variation induced by gravity waves can make a significant contribution to the vertical and horizontal transport of ice particles and ultimately transform them into thin multiple layers. Additionally, the pattern of the multiple layers at least partially depends on the vertical wavelength of the gravity wave, the ice particle size and the wind velocity. The results presented in this paper will be helpful to better understand the occurrence of multiple layers of PMSE as well as its variation process.
- Simultaneous multiplicative column-normalized method (SMART) for
3-D ionosphere tomography in comparison to other algebraic methods
Abstract: Simultaneous multiplicative column-normalized method (SMART) for 3-D ionosphere tomography in comparison to other algebraic methods
T. Gerzen and D. Minkwitz
Ann. Geophys., 34, 97-115, doi:10.5194/angeo-34-97-2016, 2016
The accuracy and availability of satellite-based applications like GNSS positioning and remote sensing crucially depends on the knowledge of the ionospheric electron density distribution. The 3-D reconstruction of the ionosphere is one of the major tools to provide ionospheric corrections and to study physical processes in the ionosphere. In this paper, we introduce two reconstruction methods SMART and SMART+, and compare them to well-known reconstruction techniques ART and SART.
- Twin mesospheric bores observed over Brazilian equatorial region
Abstract: Twin mesospheric bores observed over Brazilian equatorial region
A. F. Medeiros, I. Paulino, M. J. Taylor, J. Fechine, H. Takahashi, R. A. Buriti, L. M. Lima, and C. M. Wrasse
Ann. Geophys., 34, 91-96, doi:10.5194/angeo-34-91-2016, 2016
This paper reports two consecutive mesospheric bores observed in the airglow emissions (OH and OI5577). Both bores propagated to the east and showed similar spectral characteristics. However, the first one exhibited a dark leading front with several trailing waves behind and progressed into a brighter airglow region. However, the second bore, observed in the OH layer, was comprised of several bright waves propagating into a darker airglow region.
- The effects of the big storm events in the first half of 2015 on
the radiation belts observed by EPT/PROBA-V
Abstract: The effects of the big storm events in the first half of 2015 on the radiation belts observed by EPT/PROBA-V
V. Pierrard and G. Lopez Rosson
Ann. Geophys., 34, 75-84, doi:10.5194/angeo-34-75-2016, 2016
With the Energetic Particle Telescope (EPT) on board the ESA satellite PROBA-V, we analyze the high-resolution flux measurements of the charged particle radiation environment at 820 km of altitude for the year 2015. On 17 March 2015, a big geomagnetic storm event injected unusual electron fluxes up to low radial distances in the radiation belts. Two other major events appeared in January and June 2015, again with injections of electrons in the inner belt, contrary to what was observed in 2013.
- Ion Bernstein waves in the magnetic reconnection region
Abstract: Ion Bernstein waves in the magnetic reconnection region
Y. Narita, R. Nakamura, W. Baumjohann, K.-H. Glassmeier, U. Motschmann, and H. Comişel
Ann. Geophys., 34, 85-89, doi:10.5194/angeo-34-85-2016, 2016
Four-spacecraft Cluster observations of turbulent fluctuations in the magnetic reconnection region in the geomagnetic tail show for the first time an indication of ion Bernstein waves, electromagnetic waves that propagate nearly perpendicular to the mean magnetic field and are in resonance with ions. Bernstein waves may influence current sheet dynamics in the reconnection outflow such as a bifurcation of the current sheet.
- Mapping of steady-state electric fields and convective drifts
in geomagnetic fields – Part 1: Elementary models
Abstract: Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models
A. D. M. Walker and G. J. Sofko
Ann. Geophys., 34, 55-65, doi:10.5194/angeo-34-55-2016, 2016
This paper introduces a new method for mapping electric fields in the magnetosphere along geomagnetic field lines. This is important for conjugate studies of electric fields measured in the ionosphere by SuperDARN radars, and at spacecraft carrying electric field probes. First elementary methods in a dipole field are reviewed and then the theory of of a new method described for general magnetic field models. The method is tested in a dipole model with a Harris magnetotail field.
- Mapping of steady-state electric fields and convective drifts
in geomagnetic fields – Part 2: The IGRF
Abstract: Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 2: The IGRF
A. D. M. Walker
Ann. Geophys., 34, 67-73, doi:10.5194/angeo-34-67-2016, 2016
The method of electric field mapping along geomagnetic field lines, derived in an accompanying paper, is applied to the International Geomagnetic Reference Field. Formulae for the geomagnetic field gradient tensor are derived and these are used in a software package developed to map the electric field. A number of examples are presented illustrating the method. The method will be of importance in conjugate studies of ionospheric convection when the external magnetic field can be neglected.
- High-speed stereoscopy of aurora
Abstract: High-speed stereoscopy of aurora
R. Kataoka, Y. Fukuda, H. A. Uchida, H. Yamada, Y. Miyoshi, Y. Ebihara, H. Dahlgren, and D. Hampton
Ann. Geophys., 34, 41-44, doi:10.5194/angeo-34-41-2016, 2016
Stereoscopy of aurora was performed at the record fast sampling rate of 100 fps to measure the emission altitude of rapidly varying fine-scale structures. The new method unveiled that very different types of aurora appear in the same direction at different altitudes.
- The geomagnetic cutoff rigidities at high latitudes for different
solar wind and geomagnetic conditions
Abstract: The geomagnetic cutoff rigidities at high latitudes for different solar wind and geomagnetic conditions
W. Chu and G. Qin
Ann. Geophys., 34, 45-53, doi:10.5194/angeo-34-45-2016, 2016
To study the coupling between the magnetosphere and the solar wind at high latitudes, the cosmic rays window (CRW) is defined. The area of the CRW is related to the solar wind-magnetospheric conditions, such as the z component of Interplanetary Magnetic Field, the solar wind dynamic pressure, AE index and Dst index. This result on the CRW may be used to help forecasting the variation of the cosmic rays during the geomagnetic storms.
- Mass-loading, pile-up, and mirror-mode waves at comet
Abstract: Mass-loading, pile-up, and mirror-mode waves at comet 67P/Churyumov-Gerasimenko
M. Volwerk, I. Richter, B. Tsurutani, C. Götz, K. Altwegg, T. Broiles, J. Burch, C. Carr, E. Cupido, M. Delva, M. Dósa, N. J. T. Edberg, A. Eriksson, P. Henri, C. Koenders, J.-P. Lebreton, K. E. Mandt, H. Nilsson, A. Opitz, M. Rubin, K. Schwingenschuh, G. Stenberg Wieser, K. Szegö, C. Vallat, X. Vallieres, and K.-H. Glassmeier
Ann. Geophys., 34, 1-15, doi:10.5194/angeo-34-1-2016, 2016
The solar wind magnetic field drapes around the active nucleus of comet 67P/CG, creating a magnetosphere. The solar wind density increases and with that the pressure, which compresses the magnetosphere, increasing the magnetic field strength near Rosetta. The higher solar wind density also creates more ionization through collisions with the gas from the comet. The new ions are picked-up by the magnetic field and generate mirror-mode waves, creating low-field high-density "bottles" near 67P/CG.
- Radial dependence of ionization losses of protons of the
Earth's radiation belts
Abstract: Radial dependence of ionization losses of protons of the Earth's radiation belts
A. S. Kovtyukh
Ann. Geophys., 34, 17-28, doi:10.5194/angeo-34-17-2016, 2016
Coulomb losses and charge exchange of protons are considered in detail. On the basis of modern models of the plasmasphere and the exosphere, the radial dependences of the rates of ionization losses of protons, with μ from 0.3 to 10 keV nT−1, of the Earth's radiation belts near the equatorial plane are calculated for quiet periods. For calculation of Coulomb losses of protons we used data of ISEE-1 satellite (protons with energy from 24 to 2081 keV) on L from 3 to 9, data of Explorer-45 satellite (protons with energy from 78.6 to 872 keV) on L from 3 to 5 and data of CRRES satellite (protons with energy from 1 to 100 MeV) on L ≤ 3 (L is the McIlwain parameter). It is shown that with decreasing L the rate of ionization losses of protons of the radiation belts is reduced; for protons with μ > 1.2 keV nT−1 in a narrow region (ΔL ∼ 0.5) in the district of plasmapause in this dependence may form a local minimum of the rate. We found that the dependence from μ of the boundary on L between Coulomb losses and charge exchange of the trapped protons with hydrogen atoms is well approximated by the function Lb = 4.71μ0.32, where [μ] = keV nT−1. Coulomb losses dominate at L < Lb(μ), and at L > Lb(μ) dominates charge exchange of protons. We found the effect of subtracting the Coulomb losses from the charge exchange of protons of the radiation belts at low μ and L, which can simulate a local source of particles.