ST2.5

EDI
Inner-magnetosphere Interactions and Coupling

The Earth's inner magnetosphere contains different charged particle populations, such as the Van Allen radiation belts, ring current particles, and plasmaspheric particles. Their energy range varies from eV to several MeV, and the interplay among the charged particles provide feedback mechanisms which couple all those populations together. Ring current particles can generate various waves, for example, EMIC waves and chorus waves, which play important roles in the dynamic evolution of the radiation belts through wave-particle interactions. Ring current electrons can be accelerated to relativistic radiation belt electrons. Plasmaspheric medium can also affect these processes. In addition, precipitation of ring current and radiation belt particles will influence the ionosphere, while up-flows of ionospheric particles can affect dynamics in the inner magnetosphere. Understanding these coupling processes is crucial.

While the dynamics of outer planets’ magnetospheres are driven by a unique combination of internal coupling processes, these systems have a number of fascinating similarities which make comparative studies particularly interesting. We invite a broad range of theoretical, modelling, and observational studies focusing on the dynamics of the inner magnetosphere of the Earth and outer planets, including the coupling of the inner magnetosphere and ionosphere and coupling between the solar wind disturbances and various magnetospheric processes. Contributions from all relevant fields, including theoretical studies, numerical modelling, observations from satellite and ground-based missions are welcome. In particular, we encourage presentations using data from MMS, THEMIS, Van Allen Probes, Arase (ERG), Cluster, cube-sat missions, Juno, SuperDARN, magnetometer, optical imagers, IS-radars and ground-based VLF measurements.

Convener: Dedong WangECSECS | Co-conveners: Hayley AllisonECSECS, Ondrej Santolik, Chao YueECSECS, Qiugang Zong
vPICO presentations
| Thu, 29 Apr, 09:00–11:45 (CEST)

vPICO presentations: Thu, 29 Apr

Chairpersons: Dedong Wang, Hayley Allison, Chao Yue
09:00–09:05
09:05–09:07
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EGU21-380
|
ECS
|
Highlight
Jinxing Li, Jacob Bortnik, Xin An, Wen Li, Vassilis Angelopoulos, and Christopher Russell

Naturally occurring chorus emissions are a class of electromagnetic waves found in the space environments of the Earth and other magnetized planets. They play an essential role in accelerating high-energy electrons forming the hazardous radiation belt environment. Chorus typically occurs in two distinct frequency bands separated by a gap. The origin of this two-band structure remains a 50-year old question. Using measurements from NASA’s Van Allen Probes we report that banded chorus waves are commonly accompanied by two separate anisotropic electron components. We demonstrate, using numerical simulations, that the initially excited single-band chorus waves alter the electron distribution immediately via Landau resonance, and suppresses the electron anisotropy at medium energies. This naturally divides the electron anisotropy into a low and a high energy components which excite the upper-band and lower-band chorus waves, respectively. This mechanism may also apply to the generation of chorus waves in other magnetized planetary magnetospheres.

How to cite: Li, J., Bortnik, J., An, X., Li, W., Angelopoulos, V., and Russell, C.: Generation of two-band chorus waves in the Earth's outer radiation belt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-380, https://doi.org/10.5194/egusphere-egu21-380, 2021.

09:07–09:09
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EGU21-6342
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ECS
Dong Lin, Wenbin Wang, Viacheslav Merkin, Kevin Pham, Shanshan Bao, Kareem Sorathia, Frank Toffoletto, Xueling Shi, Oppenheim Meers, George Khazanov, Adam Michael, John Lyon, Jeffrey Garretson, and Brian Anderson

Auroral precipitation plays an important role in magnetosphere-ionosphere-thermosphere (MIT) coupling by enhancing ionospheric ionization and conductivity at high latitudes. Diffuse electron precipitation refers to scattered electrons from the plasma sheet that are lost in the ionosphere. Diffuse precipitation makes the largest contribution to the total precipitation energy flux and is expected to have substantial impacts on the ionospheric conductance and affect the electrodynamic coupling between the magnetosphere and ionosphere-thermosphere. Kinetic theory and observational analysis also demonstrate that diffuse precipitation is subject to multiple reflection effects, i.e. secondary electrons produced by the primary precipitation are reflected between the north and south hemispheres multiple times before they are fully lost in the atmosphere. In this study, we make use of the newly developed Multiscale Atmosphere-Geospace Environment (MAGE) model developed at the NASA DRIVE Science Center for Geospace Storms (CGS) to explore the role of diffuse electron precipitation in MIT coupling. Diffuse precipitation in MAGE is derived from the electron distribution in the Rice Convection Model (RCM), a ring current model that solves for energy dependent drifts of electrons and ions. Diffuse precipitation, together with mono-energetic electron precipitation based on parameterization of the magnetohydrodynamic (MHD) parameters from the Grid Agnostic MHD with Extended Research Applications (GAMERA) magnetosphere model, are input to the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM) to calculate the ionospheric ionization rate and conductivity and height-integrated conductance. With controlled numerical experiments, we investigate 1. how the diffuse precipitation affects the location and structure of a mesoscale ionospheric convection process, i.e., subauroral polarization streams (SAPS); 2. How multiple reflection effects impact the ionosphere-thermosphere and their coupling with the magnetosphere. Our study demonstrates that diffuse electron precipitation plays a critical role in determining the location and structure of SAPS. The multiple reflection effects make diffuse precipitation number flux and energy flux a few times higher than the unmodified precipitation, resulting in a greatly enhanced auroral ionospheric conductance, lower cross polar cap potential,  higher total field-aligned currents, and changes in global thermospheric winds and temperature. Therefore, diffuse electron precipitation has both local and global impacts on MIT coupling.

How to cite: Lin, D., Wang, W., Merkin, V., Pham, K., Bao, S., Sorathia, K., Toffoletto, F., Shi, X., Meers, O., Khazanov, G., Michael, A., Lyon, J., Garretson, J., and Anderson, B.: Diffuse electron precipitation in magnetosphere-ionosphere-thermosphere coupling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6342, https://doi.org/10.5194/egusphere-egu21-6342, 2021.

09:09–09:11
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EGU21-2071
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Highlight
Solène Lejosne, Naomi Maruyama, Richard S. Selesnick, and Mariangel Fedrizzi

Neutral winds have long been viewed as a driver of Jupiter’s radiation belts. On the other hand, the impact of thermospheric neutral winds in driving plasma dynamics in the Earth’s inner magnetosphere is yet to be quantified. We now have the appropriate combination of data and physics-based model to address this fundamental science question.

In this work, we revisit the local time asymmetry of the equatorial electron intensity observed in the innermost radiation belt (L=1.30). We combine in-situ field and particle observations, together with a physics-based coupled model, RCM-CTIPe, to determine whether the dynamo electric fields produced by tidal motion of upper atmospheric winds flowing across the Earth’s magnetic field lines are the main drivers of the drift-shell distortion observed in the Earth’s inner radiation belt.

Our results provide a first quantification of the contribution of the neutral wind in transporting the trapped energetic particles of the Earth’s inner radiation belt.

How to cite: Lejosne, S., Maruyama, N., Selesnick, R. S., and Fedrizzi, M.: Thermospheric Neutral Winds: A Driver of the Earth’s Inner Radiation Belt to Be Reckoned With, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2071, https://doi.org/10.5194/egusphere-egu21-2071, 2021.

09:11–09:13
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EGU21-9315
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ECS
Hui Zhu and Lunjin Chen

In this study, we use the Van Allen Probes data statistically to investigate the features of magnetic dips by the means of superposed epoch analysis. Based on the different max values of electron and proton plasma betas, we categorize the dips into two types: electron-driven dips and proton-driven dips. Superposed epoch analysis on two types of magnetic dips suggests the correlation between the magnetic fluctuations and plasma betas. Moreover, the occurrence of the butterfly distributions of relativistic electrons driven by the magnetic dips is confirmed by the statistical results. Our results reveal the statistical characteristics of magnetic dips and build up the relationship among the magnetic fluctuations and several parameters, indicating the potentially important role of magnetic dips in the dynamics of the inner magnetosphere.

How to cite: Zhu, H. and Chen, L.: Superposed Epoch Analyses of electron-driven and proton-driven magnetic dips, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9315, https://doi.org/10.5194/egusphere-egu21-9315, 2021.

09:13–09:15
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EGU21-15306
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ECS
Yikai Hsieh and Yoshiharu Omura

Whistler mode chorus emissions in the Earth’s magnetosphere cause energetic electron precipitation and the associated pulsating aurora. First-order cyclotron resonance in parallel whistler mode wave-particle interactions is the main mechanism of the precipitation. Not only cyclotron resonance but also Landau resonance and higher-order cyclotron resonances occur in the oblique whistler mode wave-particle interactions. Especially, electrons can be accelerated and scattered to lower equatorial pitch angles rapidly via Landau resonance. We apply test particle simulation and the Green’s function method to check the energetic electron precipitation caused by oblique chorus emissions. We simulate the wave-particle interactions around L=4.5 for electron ranges from 10 keV to a few MeV. We further compare the precipitation fluxes between parallel and oblique chorus emissions. Our simulation result reveals that oblique chorus emissions lead to more electron precipitation than parallel chorus emissions. At kinetic energy E < 100 keV, the electron precipitation ratio (oblique case/parallel case) is about 1.3. At 100 keV < E < 0.5 MeV, the ratio is greater than 2. At E > 0.5 MeV, the ratio is greater than 2 orders. Multiple resonances effect in the oblique whistler mode wave-particle interactions is the reason for the greater precipitation.

How to cite: Hsieh, Y. and Omura, Y.: Energetic electron precipitation via oblique whistler mode chorus emissions in the outer radiation belt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15306, https://doi.org/10.5194/egusphere-egu21-15306, 2021.

09:15–09:20
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EGU21-6779
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solicited
Yiqun Yu, Shengjun Su, Jinbin Cao, Michael Denton, and Vania Jordanova

Satellite surface charging often occurs in the inner magnetosphere from the pre-midnight to the dawn sector when electron fluxes of  hundreds of eV to tens of keV are largely enhanced. Inner magnetosphere ring current models can be used to simulate/predict the satellite surface charging environment, with their flux outer boundary conditions specified either based on observations or provided by other models, such as MHD models. In the latter approach, the flux spectrum at the outer boundary is usually assumed to follow a Kappa or Maxwellian distribution, which however often departs greatly from, or underestimates, the realistic distribution below tens of keV, the energy range that is crucial in the spacecraft surface charging anomaly. This study aims to optimize the electron flux boundary condition of the inner magnetosphere ring current model to achieve a better representation of the surface charging environment. The MHD-parameterized flux spectrum is combined with an empirical electron flux model that specifies the < 40 keV electron flux spectrum. New simulation results indicate that the surface charging environment, monitored by an integrated electron flux between 10<E<50 keV, is significantly enhanced by 1-2 orders of magnitude as opposed to the case in which Kappa/Maxwellian distribution is used at the outer boundary. The new results therefore show better agreement with Van Allen Probes measurements. The improved boundary condition also impacts the auroral precipitation, which may change the conductivity and circulated dynamics. 

How to cite: Yu, Y., Su, S., Cao, J., Denton, M., and Jordanova, V.: Simulating the Effects of Lower-Energy (<30 keV) Electrons on the Inner Magnetosphere Satellite Surface Charging Environment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6779, https://doi.org/10.5194/egusphere-egu21-6779, 2021.

09:20–09:22
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EGU21-532
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ECS
Xiongjun Shang, Si Liu, and Fuliang Xiao

With observations of Van Allen Probes, we report a rare event of quasiperiodic whistler-mode waves in the dayside magnetosphere on 20 February 2014 as a response to the enhancement of solar wind dynamic pressure (Psw). The intensities of whistler-mode waves and anisotropy distributions of energetic electrons exhibit a ~5 mins quasi-periodic pattern, which is consistent with the period of synchronously observed compressional ULF waves. Based on the wave growth rates calculation, we suggest that the quasiperiodic whistler-mode waves could be generated by the energetic electrons with modulated anisotropy. The Poynting vectors of the whistler-mode waves alternate between northward and southward direction with a period twice the compressional ULF wave's near the equator, also exhibiting a clear modulated feature. This is probably because the intense ULF waves slightly altered the location of the local magnetic minimum, and thus modulated the relative direction of the wave source region respect to the spacecraft. Current results provide a direct evidence that the Psw play an important role in the generation and propagation of whistler-mode waves in the Earth's magnetosphere.

How to cite: Shang, X., Liu, S., and Xiao, F.: Solar wind compression induced ULF-modulation of whistler-mode waves in the deep inner magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-532, https://doi.org/10.5194/egusphere-egu21-532, 2021.

09:22–09:24
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EGU21-634
Jianjun Liu

Interplanetary (IP) shock driven sudden compression produces disturbances in the polar ionosphere. Various studies have investigated the effects of IP shock using imagers and radars. However, very few studies have reported the plasma flow reversal and a sudden vertical plasma drift motion following a CME driven IP shock. We report on the cusp ionospheric features following an IP shock impingement on 16 June 2012, using SuperDARN radar and digisonde from the Antarctic Zhongshan Station (ZHO). SuperDARN ZHO radar observed instant strong plasma flow reversal during the IP shock driven sudden impulse (SI) with a suppression in the number of backscatter echoes. Besides, we also report on a “Doppler Impulse” phenomenon, an instant and brief downward plasma motion, were observed by the digisonde in response to the SI and discuss the possible physical causes. Geomagnetic disturbance and convection patterns indicate the flow reversal was generated by the downward field-aligned current (FAC). We speculate that sudden enhancement in ionization associated with SI is responsible for generating the Doppler Impulse phenomenon.

How to cite: Liu, J.: Transient cusp ionospheric disturbances caused by a solar wind dynamic pressure enhancement, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-634, https://doi.org/10.5194/egusphere-egu21-634, 2021.

09:24–09:26
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EGU21-821
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Highlight
Hui Wang, Yangfan He, and Hermann Luehr
The spatial and temporal distributions of ionospheric electromagnetic ion cyclotron (EMIC) waves during magnetic storms from 2014 to 2018 were studied using Swarm observations. Ionospheric EMIC waves preferably occurred during storms and their recovery phases at subauroral regions within an average magnetic latitude of 40°-55°. There were more wave events during more intense and longer period storms. However, the correlation between event number and storm duration was not good. This might be due to the effect of heavy oxygen ions on EMIC wave generation and the loss of ring current high-energy ions by the EMIC waves. There are obvious magnetic local time (MLT) differences in the peak occurrence frequency of EMIC waves during storm phases. The enhanced solar wind dynamic pressure was favorable for duskside EMIC waves. With an increased substorm activity the wave occurrence rate peak shifted from the morning side to the dusk-premidnight sector. During the recovery phase of a storm, EMIC waves in the 12-24 MLT sector appeare preferably in the earlier part than those in the 00-12 MLT sector. This shift in local time is related to the eastward rotation of the plasmaspheric plume towards morning during the late storm recovery phase and its overlap with the ring current.  Highest occurrence frequency of the storm time EMIC waves could be found in the South Atlantic Anomaly region, which might be related to the drift shell splitting
and the wave propagation effect in the weak magnetic field region
.

How to cite: Wang, H., He, Y., and Luehr, H.: Local time and longitudinal differences in the occurrence frequency of ionospheric EMIC waves during magnetic storm periods, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-821, https://doi.org/10.5194/egusphere-egu21-821, 2021.

09:26–09:28
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EGU21-1156
Yangfan He, Hui Wang, Lühr Hermann, Kistler Lynn, Saikin Anthony, Lund Eric, and Shuying Ma

The temporal and spatial evolution of electromagnetic ion cyclotron (EMIC) waves during
the magnetic storm of 21–29 June 2015 was investigated using high-resolution magnetic field observations
from Swarm constellation in the ionosphere and Van Allen Probes in the magnetosphere. Magnetospheric
EMIC waves had a maximum occurrence frequency in the afternoon sector and shifted equatorward during
the expansion phase and poleward during the recovery phase. However, ionospheric waves in subauroral
regions occurred more frequently in the nighttime than during the day and exhibited less obvious
latitudinal movements. During the main phase, dayside EMIC waves occurred in both the ionosphere
and magnetosphere in response to the dramatic increase in the solar wind dynamic pressure. Waves were
absent in the magnetosphere and ionosphere around the minimum SYM-H. During the early recovery
phase, He+ band EMIC waves were observed in the ionosphere and magnetosphere. During the late
recovery phase, H+ band EMIC waves emerged in response to enhanced earthward convection during
substorms in the premidnight sector. The occurrence of EMIC waves in the noon sector was affected by
the intensity of substorm activity. Both ionospheric wave frequency and power were higher in the summer
hemisphere than in the winter hemisphere. Waves were confined to an MLT interval of less than 5 hr with a
duration of less than 186 min from coordinated observations. The results could provide additional insights
into the spatial characteristics and propagation features of EMIC waves during storm periods

How to cite: He, Y., Wang, H., Hermann, L., Lynn, K., Anthony, S., Eric, L., and Ma, S.: Storm Time EMIC Waves Observed by Swarm and Van Allen Probe Satellites, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1156, https://doi.org/10.5194/egusphere-egu21-1156, 2021.

09:28–09:30
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EGU21-1444
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Highlight
Si Liu and Zhonglei Gao

Nonlinear resonance between energetic electrons and chorus waves is widely used to explain the frequency sweep of chorus, which predicts that rising tone elements are comprised by multiple subpackets with the frequency gradually increasing. Here we report two events that subelements with their frequencies downward chirping occur in rising tone chorus. The duration of those subelements is comparable with the regular subpackets, and their frequency sweep rates 6-12 kHz/s are consistent with previous theory and observations. Waveform of the subelement shows similar morphology to regular chorus element, consisting several finer structures "hyper-subpackets". We propose a possible scenario that the falling tone subelements are formed by nonlinear process with much shorter timescale. The starting frequency of each subelement controlled by the linear growth phase increases may because the electron distribution varies fast. This study provides new insight on chorus generation and also brings challenges.

How to cite: Liu, S. and Gao, Z.: Unexpected frequency-sweep reverse of subelements in chorus rising tone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1444, https://doi.org/10.5194/egusphere-egu21-1444, 2021.

09:30–09:32
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EGU21-4595
Kaijun Liu, Kyungguk Min, Bolu Feng, and Yan Wang

Oxygen ion cyclotron harmonic waves, with discrete spectral peaks at multiple harmonics of the oxygen ion cyclotron frequency, have been observed in the inner magnetosphere. Their excitation mechanism has remained unclear, because the singular value decomposition (SVD) method commonly used in satellite wave data analysis suggests that the waves have quasi-parallel propagation, whereas plasma theory reveals unstable modes at nearly perpendicular propagation. Hybrid simulations are carried out to investigate the excitation of these waves. The simulation results show that waves at multiple harmonics of the oxygen ion cyclotron frequency can be excited by energetic oxygen ions of a ring-like velocity distribution. More importantly, analyzing the simulated waves in a three-dimensional simulation using the common SVD method demonstrates that, while the excited waves have quasi-perpendicular propagation, the superposition of multiple waves with different azimuthal angles causes the SVD method to yield incorrectly small wave normal angles. In addition, the scattering of oxygen ions by the excited waves is examined in the simulations. The waves can cause significant transverse heating of the relatively cool background oxygen ions, through cyclotron resonance. The waves may also scatter energetic radiation belt electrons through bounce resonance and transit time scattering, like fast magnetosonic waves.

How to cite: Liu, K., Min, K., Feng, B., and Wang, Y.: Excitation of Oxygen Ion Cyclotron Harmonic Waves in the Inner Magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4595, https://doi.org/10.5194/egusphere-egu21-4595, 2021.

09:32–09:34
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EGU21-1456
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ECS
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Highlight
Chao Yue

Van Allen Probes observations of ion spectra often show a sustained gap within a very narrow energy range throughout the full orbit. To understand their formation mechanism, we statistically investigate the characteristics of the narrow gaps for oxygen ions and find that they are most frequently observed near the noon sector with a peak occurrence rate of over 30%. The magnetic moment (μ) of the oxygen ions in the gap shows a strong dependence on magnetic local time (MLT), with higher and lower μ in the morning and afternoon sectors, respectively. Moreover, we find through superposed epoch analysis that the gap formation also depends on geomagnetic conditions. Those gaps formed at lower magnetic moments (μ < 3000 keV/G) are associated with stable convection electric fields, which enable magnetospheric ions to follow a steady drift pattern that facilitates the gap formation by corotational drift resonance. On the other hand, gaps with higher μ values are statistically preceded by a gradual increase of geomagnetic activity. We suggest that ions within the gap were originally located inside the Alfven layer following closed drift paths, before they were transitioned into open drift paths as the convection electric field was enhanced. The sunward drift of these ions, with very low fluxes, forms a drainage void in the dayside magnetosphere manifested as the sustained gap in the oxygen spectrum. This scenario is supported by particle-tracing simulations, which reproduce most of the observed characteristics and therefore provide new insights into inner magnetospheric dynamics.

How to cite: Yue, C.: Sustained oxygen spectral gaps and their dynamic evolution in the inner magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1456, https://doi.org/10.5194/egusphere-egu21-1456, 2021.

09:34–09:36
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EGU21-1492
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ECS
Direct Observational Evidence of the Simultaneous Excitation of Electromagnetic Ion Cyclotron Waves and Magnetosonic Waves by an Anisotropic Proton Ring Distribution
(withdrawn)
Shangchun Teng, Nigang Liu, Qianli Ma, Xin Tao, and Wen Li
09:36–09:38
|
EGU21-1529
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Highlight
Zhenxia Zhang

Based on data from the ZH-1 satellites, companied with Van Allen Probes and NOAA observations, we analyze the high energy particle evolutions in radiation belts, slot region and SAA during August 2018 major geomagnetic storm (minimum Dst ≈ −190 nT). 

  1) Relativistic electron enhancements in extremely low L-shell regions (reaching L ∼ 3) were observed during storm. Contrary to what occurs in the outer belt, such an intense and deep electron penetration event is rare and more interesting. Strong whistler-mode (chorus and hiss) waves, with amplitudes 81–126 pT, were also observed in the extremely low L-shell simultaneously (reaching L ∼ 2.5) where the plasmapause was suppressed. The bounce-averaged diffusion coefficient calculations support that the chorus waves can play a significantly important role in diffusing and accelerating the 1–3 MeV electrons even in such low L-shells during storms.

2) A robust evidence is clearly demonstrated that the energetic electron flux with energy 30∼600 keV are increased by 2∼3 times in the inner radiation belt near equator and SAA region on dayside during the major geomagnetic storm. This is the first time that the 100s keV electron flux enhancement is reported to be potentially induced by the interaction with magnetosonic waves in extremely low L-shells (L<2) observed by Van Allen Probes. Proton loss in outer boundary of inner radiation belt takes place in energy of 2~220 MeV extensively during the occurrence of this storm but the loss mechanism is energy dependence which is consistent with some previous studies. It is confirmed that the magnetic field line curvature scattering plays a significant role in the proton loss phenomenon in energy 30-100 MeV during this storm. This work provides a beneficial help to comprehensively understand the charged particles trapping and loss in SAA region and inner radiation belt dynamic physics.

How to cite: Zhang, Z.: Electron filling and proton loss in radiation belts and SAA during 2018 storm based on ZH-1 satellite observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1529, https://doi.org/10.5194/egusphere-egu21-1529, 2021.

09:38–09:40
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EGU21-2149
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ECS
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Highlight
Nursultan Toyshiev, Galina Khachikyan, and Beibit Zhumabayev

Recently, attention was drawn [1] that after geomagnetic storms that cause formation of new radiation belts in slot region or in the inner magnetosphere, after about 2 months, there is an increase in seismic activity near the footprints of geomagnetic lines of new radiation belts. More detailed studies showed [2] that on May 30, 1991, an earthquake M=7.0 occurred in Alaska with (54.57N, 161.61E) near the footprint of geomagnetic line L = 2.69 belonging to new radiation belt, which was observed by the CRRES satellite [3] around geomagnetic lines 2<L<3 after geomagnetic storm on March 24, 1991. After geomagnetic storm on September 3, 2012, the Van Allen Probes satellites observed new radiation belt around 3.0≤L≤3.5 [4], and about 2 months later, on October 28, 2012, earthquake M=7.8 occurred off the coast of Canada (52.79N, 132.1W) near the footprint of geomagnetic line L=3.32 belonging to the new radiation belt. Also, Van Allen Probes observed new radiation belt around L=1.5-1.8 after geomagnetic storm on June 23, 2015 [5], and ~2 months later, in September 2015, seismic activity noticeably increased near the footprint of these geomagnetic lines. We consider variations in seismic activity in connection with the strongest geomagnetic storms in 2003 with Dst~- 400 nT (Halloween Storm) and the formation of a belt of relativistic electrons in the inner magnetosphere around L~1.5 existed until the end of 2005 as observed SAMPEX [6]. Analysis of data from the USGS global seismological catalog showed that near the footprint of geomagnetic lines L=1.4-1.6 the number of earthquakes with M≥4.5 increased in 2003-2004 by ~70% compared with their number in two previous years. On the Northern Tien Shan, on December 1, 2003 a strong for the region earthquake M=6.0 occurred on the border of Kazakhstan and China (42.9N, 80.5E) near the footprint of L = 1.63, adjacent to the new radiation belt.

How to cite: Toyshiev, N., Khachikyan, G., and Zhumabayev, B.: Increase in seismic activity near the footprints of new radiation belts forming after geomagnetic storms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2149, https://doi.org/10.5194/egusphere-egu21-2149, 2021.

09:40–09:42
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EGU21-2459
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ECS
Zhonglei Gao

Electron cyclotron harmonic (ECH) and whistler-mode chorus waves can contribute significantly to the magnetospheric dynamics. In the frequency-time spectrogram, ECH usually appears as a series of harmonic structureless bands, while chorus often exhibits successive discrete elements. Here, we present surprising observations by Van Allen Probes of lag-correlated rising tones of ECH and upper-band chorus waves. The time lags of ECH elements with respect to chorus elements range from 0.05 to 0.28 s, negatively correlated with the chorus peak amplitudes. The ECH elements seemingly emerge only when the chorus elements are sufficiently intense (peak amplitude >3 mV/m), and their peak amplitudes are positively correlated. Our data and modeling suggest that upper-band chorus may promote the generation of ECH through rapidly precipitating the ~keV electrons near the loss cone. This phenomenon implies that ECH and chorus may not grow independently but competitively or collaboratively gain energy from hot electrons.

How to cite: Gao, Z.: Lag-correlated rising tones of electron cyclotron harmonic and whistler-mode upper-band chorus waves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2459, https://doi.org/10.5194/egusphere-egu21-2459, 2021.

09:42–09:44
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EGU21-2775
Frantisek Nemec, Mychajlo Hajoš, Barbora Bezděková, Ondřej Santolík, and Michel Parrot

Electromagnetic waves observed in the inner magnetosphere at frequencies between about 0.5 and 4 kHz sometimes exhibit a quasiperiodic (QP) time modulation of the wave intensity with modulation periods from tens of seconds up to a few minutes. Such waves are typically termed “QP emissions” and their origin is still not fully understood. We use a large set of more than 2,000 of these events identified in the low-altitude DEMETER spacecraft data to analyze how the wave properties (modulation period, intensity) depend on relevant controlling factors. Moreover, in-situ measurements of energetic electron precipitation are used to check for precipitation peaks matching the individual QP elements. We successfully identified several such events and we perform their detailed analysis. Most importantly, while the waves may propagate unducted across L-shells, the precipitating particles follow magnetic field lines from the interaction region down to the observation point. They can thus be used to deduce important information about the location and spatial extent of the anticipated generation region of the emissions.

How to cite: Nemec, F., Hajoš, M., Bezděková, B., Santolík, O., and Parrot, M.: Quasiperiodic emissions and related particle precipitation bursts observed by the DEMETER spacecraft, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2775, https://doi.org/10.5194/egusphere-egu21-2775, 2021.

09:44–09:46
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EGU21-2805
|
ECS
Barbora Bezděková, František Němec, Michel Parrot, Jyrki Manninen, Oksana Krupařová, and Vratislav Krupař

Wave intensity measured in the very low frequency (VLF) range (up to 20 kHz) is typically represented using frequency-time spectrograms. Since the characterization of spectrogram main features and/or their direct comparison is a challenging task, we transform the measurements of the low-altitude DEMETER spacecraft using the principal component analysis (PCA). The present study is focused on both the physical interpretation of the first two principal components and their application to real physical problems. To understand the physical meaning of the first principal components, their scatter plot is constructed and discussed. Moreover, the dependence of the first principal component (PC1) coefficients on the geomagnetic activity and their seasonal/longitudinal variations are analyzed. The obtained distributions are well comparable with those obtained by previous studies for average wave intensities, indicating that the PC1 coefficients are directly related to the overall wave intensity. Furthermore, the variations of PC1 coefficients around interplanetary (IP) shock arrivals are analyzed, suggesting that the fast forward shock occurrence has the most significant effect. It is shown that the wave intensity variations depend on the wave intensity detected before the shock arrival. The shock strength and interplanetary magnetic field orientation are also important. To further demonstrate the adaptability of PCA, we use a similar method to analyze also ground-based VLF measurements performed by the Kannuslehto station located in northern Finland.

How to cite: Bezděková, B., Němec, F., Parrot, M., Manninen, J., Krupařová, O., and Krupař, V.: Variations of VLF Wave Intensity Analyzed via Principal Component Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2805, https://doi.org/10.5194/egusphere-egu21-2805, 2021.

09:46–10:30
Break
Chairpersons: Hayley Allison, Chao Yue, Dedong Wang
11:00–11:02
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EGU21-8779
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ECS
Yixin Hao, Yixin Sun, Elias Roussos, Ying Liu, Peter Kollmann, Chongjing Yuan, Norbert Krupp, Chris Paranicas, Xuzhi Zhou, Go Murakami, Hajime Kita, and Qiugang Zong

The existence of planetary radiation belts with relativistic electron components means that powerful acceleration mechanisms are operating within their volume. Mechanisms that bring charged particles planetward toward stronger magnetic fields can cause their heating. On the basis that electron fluxes in Saturn’s radiation belts are enhanced over discrete energy intervals, previous studies have suggested that rapid inward plasma flows may be controlling the production of their most energetic electrons. However, rapid plasma inflows languish in the planet’s inner magnetosphere, and they are not spatially appealing as a mechanism to form the belts. Here we show that slow, global-scale flows resulting from transient noon-to-midnight electric fields successfully explain the discretized flux spectra at quasi- and fully relativistic energies, and that they are ultimately responsible for the bulk of the highest energy electrons trapped at Saturn. This finding is surprising, given that plasma flows at Saturn are dominated by the planetary rotation; these weak electric field perturbations were previously considered impactful only over a very narrow electron energy range where the magnetic drifts of electrons cancel out with corotation. We also find quantitative evidence that ultrarelativistic electrons in Jupiterʼs radiation belts are accelerated by the same mechanism. Given that similar processes at Earth drive a less efficient electron transport compared to Saturn and Jupiter, the conclusion is emerging that global-scale electric fields can provide powerful relativistic electron acceleration, especially at strongly magnetized and fast-rotating astrophysical objects.

How to cite: Hao, Y., Sun, Y., Roussos, E., Liu, Y., Kollmann, P., Yuan, C., Krupp, N., Paranicas, C., Zhou, X., Murakami, G., Kita, H., and Zong, Q.: The Formation of Saturn’s and Jupiter’s Electron Radiation Belts by Magnetospheric Electric Fields, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8779, https://doi.org/10.5194/egusphere-egu21-8779, 2021.

11:02–11:04
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EGU21-3120
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Highlight
Yuri Shprits, Hayley Allison, Alexander Drozdov, Dedong Wang, Nikita Aseev, Irina Zhelavskaya, and Maria Usanova

Measurements from the Van Allen Probes mission clearly demonstrated that the radiation belts cannot be considered as a bulk population above approximately electron rest mass. Ultra-relativistic electrons (~>4Mev) form a new population that shows a very different morphology (e.g. very narrow remnant belts) and slow but sporadic acceleration.

We show that acceleration to multi-MeV energies can not only result of a two-step processes consisting of local heating and radial diffusion but occurs locally due to energy diffusion by whistler mode waves. Local heating appears to be able to transport electrons in energy space from 100s of keV all the way to ultra-relativistic energies (>7MeV). Acceleration to such high energies occurs only for the conditions when cold plasma in the trough region is extremely depleted down to the values typical for the plasma sheet.

There is also a clear difference between the loss mechanisms at MeV and multi MeV energies The difference between the loss mechanisms at MeV and multi-MeV energies is due to EMIC waves that can very efficiently scatter ultra-relativistic electrons, but leave MeV electrons unaffected.

We also present how the new understanding gained from the Van Allen Probes mission can be used to produce the most accurate data assimilative forecast. Under the recently funded EU Horizon 2020 Project Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER) we will study how ensemble forecasting from the Sun can produce long-term probabilistic forecasts of the radiation environment in the inner magnetosphere.

How to cite: Shprits, Y., Allison, H., Drozdov, A., Wang, D., Aseev, N., Zhelavskaya, I., and Usanova, M.: Acceleration and Loss of Ultra-relativistic Electrons in the Earth Van Allen Radiation Belts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3120, https://doi.org/10.5194/egusphere-egu21-3120, 2021.

11:04–11:06
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EGU21-3802
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ECS
Dedong Wang, Yuri Shprits, Alexander Drozdov, Nikita Aseev, Irina Zhelavskaya, Angelica Castillo, Hayley Allison, Sebastian Cervantes, and Frederic Effenberger

Using the three-dimensional Versatile Electron Radiation Belt (VERB-3D) code, we perform simulations to investigate the dynamic evolution of relativistic electrons in the Earth’s outer radiation belt. In our simulations, we use data from the Geostationary Operational Environmental Satellites (GOES) to set up the outer boundary condition, which is the only data input for simulations. The magnetopause shadowing effect is included by using last closed drift shell (LCDS), and it is shown to significantly contribute to the dropouts of relativistic electrons at high $L^*$. We validate our simulation results against measurements from Van Allen Probes. In long-term simulations, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high‐latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high‐latitude waves can result in a net loss of MeV electrons. Variations in high‐latitude chorus may account for some of the variability of MeV electrons. 

Our simulation results for the NSF GEM Challenge Events show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. We also perform simulations for the COSPAR International Space Weather Action Team (ISWAT) Challenge for the year 2017. The COSPAR ISWAT is a global hub for collaborations addressing challenges across the field of space weather. One of the objectives of the G3-04 team “Internal Charging Effects and the Relevant Space Environment” is model performance assessment and improvement. One of the expected outputs is a more systematic assessment of model performance under different conditions. The G3-04 team proposed performing benchmarking challenge runs. We ‘fly’ a virtual satellite through our simulation results and compare the simulated differential electron fluxes at 0.9 MeV and 57.27 degrees local pitch-angle with the fluxes measured by the Van Allen Probes. In general, our simulation results show good agreement with observations. We calculated several different matrices to validate our simulation results against satellite observations.

How to cite: Wang, D., Shprits, Y., Drozdov, A., Aseev, N., Zhelavskaya, I., Castillo, A., Allison, H., Cervantes, S., and Effenberger, F.: Simulations of the Relativistic Radiation Belt Electrons Using the VERB-3D Code, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3802, https://doi.org/10.5194/egusphere-egu21-3802, 2021.

11:06–11:11
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EGU21-12763
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ECS
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solicited
Johnathan Ross, Sarah Glauert, Richard Horne, Nigel Meredith, and Clare Watt

Electromagnetic ion cyclotron (EMIC) waves play an important role in relativistic electron losses in the radiation belts through diffusion via resonant wave-particle interactions. We present a new statistical model of electron diffusion by EMIC waves calculated, using Van Allen Probe observations, by averaging observation specific diffusion coefficients. The resulting diffusion coefficients therefore capture a wider range of wave-particle interactions than previous average models which are calculated using average observations. These calculations, and their role in radiation belt simulations, are then compared against existing diffusion models. The new diffusion coefficients are found to significantly improve the agreement between the calculated decay of relativistic electrons and Van Allen Probes data.

 

How to cite: Ross, J., Glauert, S., Horne, R., Meredith, N., and Watt, C.: Statistical EMIC diffusion models calculated by averaging observation specific diffusion coefficients, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12763, https://doi.org/10.5194/egusphere-egu21-12763, 2021.

11:11–11:13
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EGU21-5211
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ECS
Shuo Ti, Tao Chen, and Jiansheng Yao

Large-amplitude electromagnetic ion cyclotron (EMIC) waves induce unique dynamics of charged particle movement in the magnetosphere. In a recent study, modulation of the ion pitch angle in the presence of large-amplitude EMIC waves is observed, and there lacks a good explanation for this phenomenon. We investigate this modulation primarily via a 1-D hybrid simulation model and find that the modulation is caused by the bulk velocity triggered by large-amplitude EMIC waves. Affected by the bulk velocity, the number density of ions will enhance around pitch angle . Beyond that, the ion pitch angle is also modulated by the EMIC waves, and the modulation period is half of the EMIC waves' period. In addition, parameters that affect ion pitch angle modulation, including the wave amplitude, ion energy, ion species, and wave normal angle, are studied in our work.

How to cite: Ti, S., Chen, T., and Yao, J.: Modulation of Ion Pitch Angle in the Presence of Large-amplitude, Electromagnetic Ion Cyclotron (EMIC) Waves: 1-D Hybrid Simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5211, https://doi.org/10.5194/egusphere-egu21-5211, 2021.

11:13–11:15
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EGU21-6003
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ECS
Man Hua, Binbin Ni, Wen Li, Qianli Ma, Xudong Gu, Song Fu, Xing Cao, Yingjie Guo, and Yangxizi Liu

The Earth’s inner energetic electron belt typically exhibits one-peak radial structure with high flux intensities at radial distances < ~2.5 Earth radii. Recent studies suggested that human-made very-low-frequency (VLF) transmitters leaked into the inner magnetosphere can efficiently scatter energetic electrons, bifurcating the inner electron belt. In this study, we use 6-year electron flux data from Van Allen Probes to comprehensively analyze the statistical distributions of the bifurcated inner electron belt and their dependence on electron energy, season, and geomagnetic activity, which is crucial to understand when and where VLF transmitters can efficiently scatter electrons in addition to other naturally occurring waves. We reveal that bifurcation can be frequently observed for tens of keV electrons under relatively quiet geomagnetic conditions, typically after significant flux enhancements that elevate fluxes at L = 2.0 – ~2.5 providing the prerequisite for the bifurcation. The bifurcation typically lasts for a few days until interrupted by substorm injections or inward radial diffusion. The L-shells of bifurcation dip decrease with increasing electron energy, and the occurrence of bifurcation is higher during northern hemisphere winter than summer, supporting the important role of VLF transmitter waves in energetic electron loss in near-Earth space.

How to cite: Hua, M., Ni, B., Li, W., Ma, Q., Gu, X., Fu, S., Cao, X., Guo, Y., and Liu, Y.: Statistical Distribution of Bifurcation of Earth's Inner Energetic Electron Belt at tens of keV, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6003, https://doi.org/10.5194/egusphere-egu21-6003, 2021.

11:15–11:17
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EGU21-6074
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Highlight
Clare Watt, Hayley Allison, Rhys Thompson, Sarah Bentley, Jonathan Rae, Nigel Meredith, Sarah Glauert, RIchard Horne, Shuai Zhang, Alex Degeling, Anmin Tian, and Quanqi Shi

It is important to understand the variability of plasma processes across many different timescales in order to successfully model plasma in the inner magnetosphere. In this presentation, we focus on the interplay between the variability cold plasmaspheric plasma, whistler-mode wave activity, and the efficacy of wave-particle interactions in the inner magnetosphere. We use in-situ observations to quantify the amount and timescales of variability in pitch-angle diffusion due to plasmaspheric hiss in Earth’s inner magnetosphere, and suggest reasons for the variability. We then use a stochastic parameterization scheme to investigate the consequences of that variability in a numerical diffusion model. The results from the stochastic parameterization are contrasted with the standard approach of constructing averaged diffusion coefficients. We demonstrate that even when the average diffusion rates are the same, different timescales of variability in the wave-particle interactions lead to different end results in numerical diffusion models. We discuss the implications of our results for the modelling of wave-particle interactions in magnetospheres, and suggest quantifications that are vital for accurate modelling.

How to cite: Watt, C., Allison, H., Thompson, R., Bentley, S., Rae, J., Meredith, N., Glauert, S., Horne, R., Zhang, S., Degeling, A., Tian, A., and Shi, Q.: The nature of the variability of wave particle interactions in the inner magnetosphere and consequences for diffusion models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6074, https://doi.org/10.5194/egusphere-egu21-6074, 2021.

11:17–11:19
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EGU21-10735
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Highlight
Ondrej Santolik, William S. Kurth, and Craig A. Kletzing

Whistler-mode electromagnetic waves, especially natural emissions of chorus and hiss, have been shown to transfer energy between different electron populations in the inner magnetosphere via quasi-linear or nonlinear wave particle interactions. Average or median intensities of chorus and hiss emissions have been found to increase with increasing levels of geomagnetic activity but their stochastic variations in individual spacecraft measurements at the same location are usually comparable to these large-scale temporal effects. Statistical properties of variations of wave power directly influence results of quasi-linear diffusion models.

We use the survey measurements of the Waves instruments of the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard two Van Allen Probes to asses the probability distribution function of these stochastic variations. We take advantage of the entire data set of these measurements with a nearly 100% coverage from August 31, 2012 till October 13, 2019 (2600 days) for spacecraft A, and from  September 1, 2012 till July 16, 2019 (2510 days) for spacecraft B. 

How to cite: Santolik, O., Kurth, W. S., and Kletzing, C. A.: Variability of natural whistler-mode emissions in the inner magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10735, https://doi.org/10.5194/egusphere-egu21-10735, 2021.

11:19–11:21
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EGU21-7748
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ECS
Qian He and Si Liu

Chorus waves with extremely low frequency (ELF) below 0.1 fce are proposed to be a potential mechanism of scattering losses of relativistic electrons in the radiation belt. However, the generation of ELF chorus is still an open question. Here we report three interesting events that the occurrence of ELF chorus waves shows evident correlation with the increase of background plasma density while the disturbance of ambient magnetic field is negligible. We calculate the growth rate of chorus waves by using the correlated data of waves and particles form the Van Allen Probes. The calculated growth rates agree well with the wave along the satellite orbit. The current study suggests that the plasma density may play an important role on controlling the wave frequency during the chorus generation process.

How to cite: He, Q. and Liu, S.: The generatin of extremely low-frequency chorus waves associated with plasma density enhancement, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7748, https://doi.org/10.5194/egusphere-egu21-7748, 2021.

11:21–11:23
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EGU21-9131
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ECS
Qianli Ma

We investigate the statistical distribution of energetic electron precipitation from the equatorial magnetosphere due to hiss waves in the plasmasphere and plumes. Using Van Allen Probes measurements, we calculate the pitch angle diffusion coefficients at the pitch angle of bounce loss cone, and evaluate the energy spectrum of precipitating electron flux using quasi-linear theory. Our ~6.5 years survey shows that, during disturbed times, the plasmaspheric hiss mostly causes the electron precipitation at L > 3 near the dayside in the plasmasphere, and hiss waves in plume cause the precipitation at L > 5 near dayside and L > 3.5 near the dusk side. The precipitating energy flux increases with increasing geomagnetic index, and is typically higher in the plasmaspheric plume than the plasmasphere. The characteristic energy of precipitation increases from ~20 keV at L = 6 to ~100 keV at L = 3, potentially causing the loss of electrons at several hundred keV. Although the total precipitating energy flux due to hiss waves is generally lower than the precipitation due to whistler mode chorus waves, the characteristic energy of precipitation due to hiss is higher, and the precipitation extends closer to the Earth.

How to cite: Ma, Q.: Statistical Distribution of Energetic Electron Precipitation due to Hiss Waves In the Earth’s Inner Magnetosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9131, https://doi.org/10.5194/egusphere-egu21-9131, 2021.

11:23–11:25
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EGU21-13458
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ECS
Sigiava Aminalragia-Giamini, Christos Katsavrias, Constantinos Papadimitriou, Ioannis A. Daglis, Ingmar Sandberg, and Piers Jiggens

The nature of the semi-annual variation in the relativistic electron fluxes in the Earth’s outer radiation belt is investigated using Van Allen Probes (MagEIS and REPT) and GOES (EPS) data during solar cycle 24. We perform wavelet and cross-wavelet analysis in a broad energy and spatial range of electron fluxes and examine their phase relationship with the axial, equinoctial and Russell-McPherron mechanisms. It is found that the semi-annual variation in the relativistic electron fluxes exhibits pronounced power in the 0.3 – 4.2 MeV energy range at L-shells higher than 3.5 and, moreover, it exhibits an in-phase relationship with the Russell-McPherron effect indicating the former is primarily driven by the latter. Furthermore, the analysis of the past 3 solar cycles with GOES/EPS indicates that the semi-annual variation at geosynchronous orbit is evident during the descending phases and coincides with periods of a higher (lower) HSS (ICME) occurrence.

This work has received funding from the European Union's Horizon 2020 research and innovation programme “SafeSpace” under grant agreement No 870437 and from the European Space Agency under the “European Contribution to International Radiation Environment Near Earth (IRENE) Modelling System” activity under ESA Contract No 4000127282/19/NL/IB/gg.

How to cite: Aminalragia-Giamini, S., Katsavrias, C., Papadimitriou, C., A. Daglis, I., Sandberg, I., and Jiggens, P.: On the semi-annual variation of relativistic electrons in the outer radiation belt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13458, https://doi.org/10.5194/egusphere-egu21-13458, 2021.

11:25–11:45