Annales Geophysicae (ANGEO)
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Open Access journal
ISSN (Print) 0992-7689 - ISSN (Online) 1432-0576
Published by European Geosciences Union [8 journals]
- A statistical study of the motion of pulsating aurora patches: using the
THEMIS All-Sky Imager
Abstract: A statistical study of the motion of pulsating aurora patches: using the THEMIS All-Sky Imager
Bing Yang, Eric Donovan, Jun Liang, and Emma Spanswick
Ann. Geophys., 35, 217-225, doi:10.5194/angeo-35-217-2017, 2017
This is the first statistical study of the motion of patchy pulsating aurora (PPA). Our results show that PPA patches mainly drift eastward after midnight and westward before midnight, which suggests that the drifts of auroral patches could be a proxy for the ionospheric convection and provide a convenient and accurate method to remotely sense the magnetospheric convection. We also found that patch velocities do not seem to depend on AE index.
- Three-dimensional data assimilation for ionospheric reference scenarios
Abstract: Three-dimensional data assimilation for ionospheric reference scenarios
Tatjana Gerzen, Volker Wilken, David Minkwitz, Mainul M. Hoque, and Stefan Schlüter
Ann. Geophys., 35, 203-215, doi:10.5194/angeo-35-203-2017, 2017
The reliable estimation of ionospheric refraction effects is an importanttopic in the GNSS (Global Navigation Satellite Systems) positioning andnavigation domain, especially in safety-of-life applications. This paperdescribes a three-dimensional ionosphere reconstruction approach that combines three datasources with an ionospheric background model: space- and ground-based total electron content(TEC)measurements and ionosonde observations. First the background model isadjusted by F2 layer characteristics, obtained from space-based ionosphericradio occultation (IRO) profiles and ionosonde data, and secondly the finalelectron density distribution is estimated by an algebraic reconstructiontechnique.
The method described is validated by TECmeasurements of independent ground-based GNSS stations, space-based TEC fromthe Jason 1 and 2 satellites, and ionosonde observations. A significantimprovement is achieved by the data assimilation, with a decrease in theresidual errors by up to 98 % compared to the initial guess of thebackground. Furthermore, the results underpin the capability of space-basedmeasurements to overcome data gaps in reconstruction areas where less GNSSground-station infrastructure exists.
- A high-altitude balloon experiment to probe stratospheric electric fields
from low latitudes
Abstract: A high-altitude balloon experiment to probe stratospheric electric fields from low latitudes
Subramanian Gurubaran, Manu Shanmugam, Kaliappan Jawahar, Kaliappan Emperumal, Prasanna Mahavarkar, and Suneel Kumar Buduru
Ann. Geophys., 35, 189-201, doi:10.5194/angeo-35-189-2017, 2017
Results from a high-altitude balloon experiment conducted from a low-latitude station in India are presented in this work. The objectives of this experiment were to probe and understand the processes driving the various electric field sources at low latitudes. During this experiment, electric fields in the range of 5–6 mV m−1 were observed at the balloon float altitude of 35 km. Atmospheric waves of few 100 km horizontal wavelength are suggested to be a potential source of these electric fields.
- Large-scale gravity wave perturbations in the mesopause region above
Northern Hemisphere midlatitudes during autumnal equinox: a joint study by
the USU Na lidar and Whole Atmosphere Community Climate Model
Abstract: Large-scale gravity wave perturbations in the mesopause region above Northern Hemisphere midlatitudes during autumnal equinox: a joint study by the USU Na lidar and Whole Atmosphere Community Climate Model
Xuguang Cai, Tao Yuan, and Han-Li Liu
Ann. Geophys., 35, 181-188, doi:10.5194/angeo-35-181-2017, 2017
Atmospheric gravity waves play highly important roles in the dynamic and chemical processes in the upper atmosphere. To assess their magnitude, continuous full diurnal cycle measurements of temperature perturbations are necessary. In this paper we have calculated the large-scale gravity wave modulations between 85 and 99 km altitude based on the measurements by a unique Na lidar at Utah State University in the month of September from 2011 to 2015. The waves with period of 3–5 h dominate.
- The response of the H geocorona between 3 and 8 Re to geomagnetic
disturbances studied using TWINS stereo Lyman-α data
Abstract: The response of the H geocorona between 3 and 8 Re to geomagnetic disturbances studied using TWINS stereo Lyman-α data
Jochen H. Zoennchen, Uwe Nass, Hans J. Fahr, and Jerry Goldstein
Ann. Geophys., 35, 171-179, doi:10.5194/angeo-35-171-2017, 2017
Circumterrestrial Lyman-α column brightness observations from3–8 Earth radii (Re) have been used to study temporal densityvariations in the exospheric neutral hydrogen as response to geomagneticdisturbances of different strength, i.e., Dst peak values between −26 and−147 nT. The data used were measured by the two Lyman-α detectors(LAD1/2) onboard both TWINS satellites between the solar minimum of 2008 andnear the solar maximum of 2013. The solar Lyman-α flux at 121.6 nm isresonantly scattered near line center by exospheric H atoms and measured bythe TWINS LADs. Along a line of sight (LOS), the scattered LOS-columnintensity is proportional to the LOS H column density, assuming opticallythin conditions above 3 Re. In the case of the eight analyzedgeomagnetic storms we found a significant increase in the exosphericLyman-α flux between 9 and 23 % (equal to the same increase inH column density ΔnH) compared to the undisturbed case shortbefore the storm event. Even weak geomagnetic storms (e.g., Dst peak values ≥ −41 nT) under solar minimum conditions show increases up to23 % of the exospheric H densities. The strong H density increase in theobserved outer exosphere is also a sign of an enhanced H escape flux duringstorms. For the majority of the storms we found an average time shift of about11 h between the time when the first significant dynamic solar windpressure peak (pSW) hits the Earth and the time when theexospheric Lyman-α flux variation reaches its maximum. The resultsshow that the (relative) exospheric density reaction of ΔnHhave a tendency to decrease with increasing peak values of Dst index or theKp index daily sum. Nevertheless, a simple linear correlation between ΔnH and these two geomagnetic indices does not seem to exist. Incontrast, when recovering from the peak back to the undisturbed case,the Kp index daily sum and the ΔnH essentially showthe same temporal recovery.
- Understanding the variability of magnetic storms caused by ICMEs
Abstract: Understanding the variability of magnetic storms caused by ICMEs
Remi Benacquista, Sandrine Rochel, and Guy Rolland
Ann. Geophys., 35, 147-159, doi:10.5194/angeo-35-147-2017, 2017
The Earth's magnetic field creates a magnetic bulk all around it called the magnetosphere. This bulk a priori protects us from the particles coming from the sun but sometimes undergoes violent events such as interplanetary coronal mass ejections. These cause the entry of particles into the magnetosphere, which can be harmful for satellites. In this paper, we performed a statistical study to characterize the interplanetary coronal mass ejections and their ability to disturb the magnetosphere.
- Climatology of thermospheric neutral winds over Oukaïmeden
Observatory in Morocco
Abstract: Climatology of thermospheric neutral winds over Oukaïmeden Observatory in Morocco
Mohamed Kaab, Zouhair Benkhaldoun, Daniel J. Fisher, Brian Harding, Aziza Bounhir, Jonathan J. Makela, Amine Laghriyeb, Khalifa Malki, Ahmed Daassou, and Mohamed Lazrek
Ann. Geophys., 35, 161-170, doi:10.5194/angeo-35-161-2017, 2017
we present the first multi-year results of the climatology of horizontal winds obtained during a period of 26 months. We compare the observed climatologies of neutral winds to that provided by the recently updated Horizontal Wind Model (HWM14) in order to validate that model's predictions of the thermospheric wind patterns over the eastern portion of Africa. HWM14 generally compares well with the horizontal winds, but significant magnitude and phase differences remain in certain seasons.
- Pancake-like and tablet-like distribution functions of energetic electrons
in the middle magnetosphere
Abstract: Pancake-like and tablet-like distribution functions of energetic electrons in the middle magnetosphere
Peter Bespalov and Olga Savina
Ann. Geophys., 35, 133-138, doi:10.5194/angeo-35-133-2017, 2017
We propose a simple explanation of the prolonged existence of pancake-like electron velocity distributions in the radiation belts. The pancake-like distribution function is characterized by a longitudinal particle velocity (along the magnetic field) of the order of the thermal velocity of the background plasma. The parameters of the tablet-like distribution function are refined. The stability of these distributions is examined.
- A study of geomagnetic field variations along the 80° S
Abstract: A study of geomagnetic field variations along the 80° S geomagnetic parallel
Stefania Lepidi, Lili Cafarella, Patrizia Francia, Andrea Piancatelli, Manuela Pietrolungo, Lucia Santarelli, and Stefano Urbini
Ann. Geophys., 35, 139-146, doi:10.5194/angeo-35-139-2017, 2017
We study geomagnetic field variations from 1 min data at three Antarctic sites (Mario Zucchelli Station, Scott Base, Talos Dome) along the 80° S geomagnetic parallel. The daily variation depends on local time, due to the polar extension of midlatitude ionospheric currents. The ~1–7 mHz power maximizes around 12 MLT, close to the cusp, and the coherence does so between stations around 24 MLT. The wave propagation is consistent with a daytime solar wind source and with nighttime substorm processes.
- Observations of equatorial ionization anomaly over Africa and Middle East
during a year of deep minimum
Abstract: Observations of equatorial ionization anomaly over Africa and Middle East during a year of deep minimum
Olawale Bolaji, Oluwafisayo Owolabi, Elijah Falayi, Emmanuel Jimoh, Afolabi Kotoye, Olumide Odeyemi, Babatunde Rabiu, Patricia Doherty, Endawoke Yizengaw, Yosuke Yamazaki, Jacob Adeniyi, Rafiat Kaka, and Kehinde Onanuga
Ann. Geophys., 35, 123-132, doi:10.5194/angeo-35-123-2017, 2017
Movement of plasma to higher latitudes by EIA is known to relate to eastward electric field/EEJ and thermospheric meridional neutral wind. Experiments from GPS measurements that unveil thermospheric meridional neutral wind effect on plasma transportation in the F region are very few compared with electric field/EEJ. This work includes examples of thermospheric meridional neutral wind effects on GPS TEC measurements and their roles in transportation of plasma compared to electric field/EEJ.
- Spin axis offset calibration on THEMIS using mirror modes
Abstract: Spin axis offset calibration on THEMIS using mirror modes
Dennis Frühauff, Ferdinand Plaschke, and Karl-Heinz Glassmeier
Ann. Geophys., 35, 117-121, doi:10.5194/angeo-35-117-2017, 2017
Vector magnetic field instruments mounted on spacecraft require precise in-flight calibration of the offsets of all three axes, i.e., the output in vanishing ambient field. While calibration of the spin plane offsets is trivial, we apply a new technique for determining the spin axis offset, not relying on solar wind data but on magnetosheath encounters. This technique is successfully applied to the satellites of the THEMIS mission to update the calibration parameters of the complete mission.
- Scintillation measurements at Bahir Dar during the high solar activity
phase of solar cycle 24
Abstract: Scintillation measurements at Bahir Dar during the high solar activity phase of solar cycle 24
Martin Kriegel, Norbert Jakowski, Jens Berdermann, Hiroatsu Sato, and Mogese Wassaie Mersha
Ann. Geophys., 35, 97-106, doi:10.5194/angeo-35-97-2017, 2017
Small-scale ionospheric disturbances may cause severe radio scintillations ofsignals transmitted from global navigation satellite systems (GNSSs).Consequently, small-scale plasma irregularities may heavily degrade theperformance of current GNSSs such as GPS, GLONASS or Galileo. This paperpresents analysis results obtained primarily from two high-rate GNSS receiverstations designed and operated by the German Aerospace Center (DLR) incooperation with Bahir Dar University (BDU) at 11.6° N,37.4° E. Both receivers collect raw data sampled at up to 50 Hz, fromwhich characteristic scintillation parameters such as the S4 index arededuced.
This paper gives a first overview of the measurement set-up and the observedscintillation events over Bahir Dar in 2015. Both stations are located closeto one another and aligned in an east–west, direction which allows us toestimate the zonal drift velocity and spatial dimension of equatorialionospheric plasma irregularities. Therefore, the lag times of movingelectron density irregularities and scintillation patterns are derived byapplying cross-correlation analysis to high-rate measurements of the slanttotal electron content (sTEC) along radio links between a GPS satellite andboth receivers and to the associated signal power,respectively. Finally, the drift velocity is derived from the estimated lagtime, taking into account the geometric constellation of both receivingantennas and the observed GPS satellites.
- Vertical wavenumber spectra of three-dimensional winds revealed by
radiosonde observations at midlatitude
Abstract: Vertical wavenumber spectra of three-dimensional winds revealed by radiosonde observations at midlatitude
Shao Dong Zhang, Chun Ming Huang, Kai Ming Huang, Ye Hui Zhang, Yun Gong, and Quan Gan
Ann. Geophys., 35, 107-116, doi:10.5194/angeo-35-107-2017, 2017
We present the first statistical results of vertical wind fluctuation spectra, which revealed a very shallow spectral structure, with mean slopes of −0.58 and −0.23 in the troposphere and lower stratosphere, respectively. No existing spectral theories can comprehensively explain the observed three-dimensional wind spectra, indicating that the spectral features of atmospheric fluctuations are far from fully understood.
- An improved troposphere tomographic approach considering the signals
coming from the side face of the tomographic area
Abstract: An improved troposphere tomographic approach considering the signals coming from the side face of the tomographic area
Qingzhi Zhao and Yibin Yao
Ann. Geophys., 35, 87-95, doi:10.5194/angeo-35-87-2017, 2017
A troposphere tomographic method has been proposed considering the signal rays penetrating from the side of the area of interest. Given the method above needs the establishment of a unit scale factor model using the radiosonde data at only one location in the research area, an improved approach is proposed by considering the reasonability of modelling data and the diversity of the modelling parameters for building a more accurate unit scale factor model.
- Ground-based acoustic parametric generator impact on the atmosphere and
ionosphere in an active experiment
Abstract: Ground-based acoustic parametric generator impact on the atmosphere and ionosphere in an active experiment
Yuriy G. Rapoport, Oleg K. Cheremnykh, Volodymyr V. Koshovy, Mykola O. Melnik, Oleh L. Ivantyshyn, Roman T. Nogach, Yuriy A. Selivanov, Vladimir V. Grimalsky, Valentyn P. Mezentsev, Larysa M. Karataeva, Vasyl. M. Ivchenko, Gennadi P. Milinevsky, Viktor N. Fedun, and Eugen N. Tkachenko
Ann. Geophys., 35, 53-70, doi:10.5194/angeo-35-53-2017, 2017
Before many catastrophic phenomena such as earthquakes, sound is generated at a very low frequency. It is already established that it can disturb the upper layer of the atmosphere – the ionosphere. Control of disasters' precursors is important. Using the unique, powerful sound generator, whose loudness is comparable to an ascending jet, we have constructed the theory and conducted a series of experiments trying to model acoustic action of disasters on the ionosphere.
- Absence of the strahl during times of slow wind
Abstract: Absence of the strahl during times of slow wind
Chris Gurgiolo and Melvyn L. Goldstein
Ann. Geophys., 35, 71-85, doi:10.5194/angeo-35-71-2017, 2017
Observations during periods when the solar wind has a speed
- Induction effects of geomagnetic disturbances in the geo-electric field
variations at low latitudes
Abstract: Induction effects of geomagnetic disturbances in the geo-electric field variations at low latitudes
Vafi Doumbia, Kouadio Boka, Nguessan Kouassi, Oswald Didier Franck Grodji, Christine Amory-Mazaudier, and Michel Menvielle
Ann. Geophys., 35, 39-51, doi:10.5194/angeo-35-39-2017, 2017
The electrical inductions within the Earth surface due to geomagnetic field variations were examined. For that purpose the records of the geomagnetic and geo-electric field variations observed in West Africa were used. We have found that the geomagnetic field brisk variations induce non-negligible geo-electric field variations at low latitudes. This result implies a possible intense geomagnetically induced current flow in the vicinity of the equatorial electrojet influence area.
- Signature of ionospheric irregularities under different geophysical
Abstract: Signature of ionospheric irregularities under different geophysical conditions on SBAS performance in the western African low-latitude region
Oladipo Emmanuel Abe, Xurxo Otero Villamide, Claudia Paparini, Rodrigue Herbert Ngaya, Sandro M. Radicella, and Bruno Nava
Ann. Geophys., 35, 1-9, doi:10.5194/angeo-35-1-2017, 2017
Rate of change of TEC (ROT) and its index (ROTI) are considered agood proxy to characterize the occurrence of ionospheric plasmairregularities like those observed after sunset at low latitudes. SBASs(satellite-based augmentation systems) are civil aviation systems thatprovide wide-area or regional improvement to single-frequency satellitenavigation using GNSS (Global Navigation Satellite System) constellations.Plasma irregularities in the path of the GNSS signal after sunset causesevere phase fluctuations and loss of locks of the signals in GNSS receiverat low-latitude regions. ROTI is used in this paper to characterize plasmadensity ionospheric irregularities in central–western Africa under nominaland disturbed conditions and identified some days of irregularityinhibition. A specific low-latitude algorithm is used to emulate potentialpossible SBAS message using real GNSS data in the western African low-latituderegion. The performance of a possible SBAS operation in the region underdifferent ionospheric conditions is analysed. These conditions includeeffects of geomagnetic disturbed periods when SBAS performance appears to beenhanced due to ionospheric irregularity inhibition. The results of thispaper could contribute to a feasibility assessment of a European Geostationary Navigation Overlay System-based SBAS inthe sub-Saharan African region.
- On the response of quasi-adiabatic particles to magnetotail
Abstract: On the response of quasi-adiabatic particles to magnetotail reconfigurations
Dominique C. Delcourt, Helmi V. Malova, and Lev M. Zelenyi
Ann. Geophys., 35, 11-23, doi:10.5194/angeo-35-11-2017, 2017
In a magnetic field reversal, the guiding center may not be valid due to large variation of the magnetic field on the length scale of the particle gyro-radius. Although they do not execute regular helical motion and temporarily meander inside the field reversal, quasi-adiabatic particles exit this reversal with a magnetic moment nearly identical to that at entry. We show that this behavior, which is a steady-state concept, can persist during dipolarization despite the induced electric field.
- Measurements of the total ozone column using a Brewer spectrophotometer
and TOMS and OMI satellite instruments over the Southern Space Observatory
Abstract: Measurements of the total ozone column using a Brewer spectrophotometer and TOMS and OMI satellite instruments over the Southern Space Observatory in Brazil
Lucas Vaz Peres, Hassan Bencherif, Nkanyiso Mbatha, André Passaglia Schuch, Abdoulwahab Mohamed Toihir, Nelson Bègue, Thierry Portafaix, Vagner Anabor, Damaris Kirsch Pinheiro, Neusa Maria Paes Leme, José Valentin Bageston, and Nelson Jorge Schuch
Ann. Geophys., 35, 25-37, doi:10.5194/angeo-35-25-2017, 2017
In this paper, we analyze the total ozone column over the Southern Space Observatory, Brazil, between 1992 and 2014 by Brewer spectrometer and TOMS and OMI satellite instruments, finding good agreement between the two. In addition, the seasonal TOC variation is dominated by an annual cycle, and the Quasi-Biennial Oscillation modulation was the main mode of interannual variability and in opposite phase to the total ozone column anomaly time series.