The dynamics of the inner boundary of the outer radiation belt during geomagnetic storms

2020 ◽  
Author(s):  
Xiaofei Shi ◽  
Jie Ren ◽  
Qiugang Zong
Keyword(s):  
Radiation Belt ◽  
Electron Flux ◽  
Geomagnetic Storms ◽  
Minimum Energy ◽  
Onset Time ◽  
Recovery Phase ◽  
Outer Radiation Belt ◽  
H Index ◽  
Late Recovery ◽  
Energy Dependent

<p>We present a statistical study of energy-dependent and L shell-dependent inner boundary of the outer radiation belt during 37 isolated geomagnetic storms using observations from Van Allen Probes from 2013 to 2017. There are mutual transformations between "V-shaped" and "S-shaped" inner boundaries during different storm phases, resulting from the competition among electron loss, radial transport and local acceleration. The radial position, onset time, E<sub>st</sub> (the minimum energy at L<sub>st</sub> where the inner boundary starts to exhibit an S-shaped form), and the radial width of S-shaped boundary (ΔL) are quantitatively defined according to the formation of a reversed energy spectrum (electron flux going up with increasing energies from hundreds of keV to ~1 MeV) from a kappa-like spectrum (electron flux steeply falling with increasing energies). The case and statistical results present that (1) The inner boundary has repeatable features associated with storms: the inner boundary is transformed from S-shaped to V-shaped form in several hours during the storm commencement and main phase, and retains in the V-shaped form for several days until it evolves into S-shaped during late recovery phase; (2) ΔL shows positive correlation with SYM-H index; (3) The duration of the V-shaped form is positively correlated with the storm intensity and the duration of the recovery phase; (4) The minimum energy E<sub>st</sub> are mainly distributed in the range of 100-550 keV. All these findings have important implications for understanding the dynamics of energetic electrons in the slot region and the outer radiation belt during geomagnetic storms.</p>

scholarly journals Variability of Relativistic Electron Flux (E > 2 MeV) during Geo-Magnetically Quiet and Disturbed days: A Case Study

2020 ◽  
Author(s):  
Tulsi Thapa ◽  
Binod Adhikari ◽  
Prashrit Baruwal ◽  
Kiran Pudasainee
Keyword(s):  
Relativistic Electron ◽  
Geomagnetic Storm ◽  
Radiation Belt ◽  
Cross Correlation ◽  
Electron Flux ◽  
Geomagnetic Storms ◽  
Correlation Technique ◽  
Outer Radiation Belt ◽  
Cross Correlation Analysis ◽  
Intense Storm

Abstract. We analyzed the relativistic electron fluxes (E > 2 MeV) during three different geomagnetic storms: moderate, intense, and super-intense and one geo-magnetically quiet period. We have opted Continuous wavelet analysis and cross-correlation technique to extend current understanding and of the radiation-belt dynamics. We found that the fluctuation of relativistic electron fluxes dependent basically on prolonged southward interplanetary magnetic field IMF-Bz. Cross-correlation analysis depicted that SYM-H does not show a strong connection either with relativistic electron enhancement events or persistent depletion events. Our result supports the fact that geomagnetic storms are not a primary factor that pumps up the radiation belt. In fact they seem event specific; either depletion or enhancement or slight effect on the outer radiation belt might be observed depending on the event. Solar wind pressure and velocity were found to be highly and positively correlated with relativistic electron. We found that, the count of relativistic electron flux (> 2 MeV) decreases during the main phase of geomagnetic storm with the increase in – from quiet to super intense storm – geomagnetic storm conditions (Table 1). However, Psw was found to be weakly correlated in case of intense storms following an abrupt increase of electron flux for ~ 4 hrs, which is interesting and unique.

scholarly journals Medium Energy Electron Flux in Earth's Outer Radiation Belt (MERLIN): A Machine Learning Model

2020 ◽  
Author(s):  
Artem Smirnov ◽  
Max Berrendorf ◽  
Yuri Shprits ◽  
Elena A. Kronberg ◽  
Hayley J Allison ◽  
...  
Keyword(s):  
Machine Learning ◽  
Radiation Belt ◽  
Electron Flux ◽  
Learning Model ◽  
Energy Electron ◽  
Medium Energy ◽  
Outer Radiation Belt ◽  
Machine Learning Model

ULF Wave Power During Geomagnetic Storms and Implications for Radial Diffusion Processes

2021 ◽  
Author(s):  
Jasmine Sandhu ◽  
Jonathan Rae ◽  
John Wygant ◽  
Aaron Breneman ◽  
Sheng Tian ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Diffusion Coefficients ◽  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Radial Diffusion ◽  
Ulf Waves ◽  
Wave Power ◽  
Outer Radiation Belt ◽  
Large Variability ◽  
Ulf Wave

<p>Ultra Low Frequency (ULF) waves drive radial diffusion of radiation belt electrons, where this process contributes to and, at times, dominates energisation, loss, and large scale transport of the outer radiation belt. In this study we quantify the changes and variability in ULF wave power during geomagnetic storms, through a statistical analysis of Van Allen Probes data for the time period spanning 2012 – 2019. The results show that global wave power enhancements occur during the main phase, and continue into the recovery phase of storms. Local time asymmetries show sources of ULF wave power are both external solar wind driving as well as internal sources from coupling with ring current ions and substorms.</p><p>The statistical analysis demonstrates that storm time ULF waves are able to access lower L values compared to pre-storm conditions, with enhancements observed within L = 4. We assess how magnetospheric compressions and cold plasma distributions shape how ULF wave power propagates through the magnetosphere. Results show that the Earthward displacement of the magnetopause is a key factor in the low L enhancements. Furthermore, the presence of plasmaspheric plumes during geomagnetic storms plays a crucial role in trapping ULF wave power, and contributes significantly to large storm time enhancements in ULF wave power.</p><p>The results have clear implications for enhanced radial diffusion of the outer radiation belt during geomagnetic storms. Estimates of storm time radial diffusion coefficients are derived from the ULF wave power observations, and compared to existing empirical models of radial diffusion coefficients. We show that current Kp-parameterised models, such as the Ozeke et al. [2014] model, do not fully capture the large variability in storm time radial diffusion coefficients or the extent of enhancements in the magnetic field diffusion coefficients.</p>

On the effect of ULF waves on the outer radiation belt during geomagnetic storms

2021 ◽  
Author(s):  
Christopher Lara ◽  
Pablo S. Moya ◽  
Victor Pinto ◽  
Javier Silva ◽  
Beatriz Zenteno
Keyword(s):  
Relativistic Electron ◽  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Cumulative Effect ◽  
Radiation Belts ◽  
Ulf Waves ◽  
Relativistic Electrons ◽  
Relative Role ◽  
Outer Radiation Belt ◽  
Ulf Wave

<p>The inner magnetosphere is a very important region to study, as with satellite-based communications increasing day after day, possible disruptions are especially relevant due to the possible consequences in our daily life. It is becoming very important to know how the radiation belts behave, especially during strong geomagnetic activity. The radiation belts response to geomagnetic storms and solar wind conditions is still not fully understood, as relativistic electron fluxes in the outer radiation belt can be depleted, enhanced or not affected following intense activity. Different studies show how these results vary in the face of different events. As one of the main mechanisms affecting the dynamics of the radiation belt are wave-particle interactions between relativistic electrons and ULF waves. In this work we perform a statistical study of the relationship between ULF wave power and relativistic electron fluxes in the outer radiation belt during several geomagnetic storms, by using magnetic field and particle fluxes data measured by the Van Allen Probes between 2012 and 2017. We evaluate the correlation between the changes in flux and the cumulative effect of ULF wave activity during the main and recovery phases of the storms for different position in the outer radiation belt and energy channels. Our results show that there is a good correlation between the presence of ULF waves and the changes in flux during the recovery phase of the storm and that correlations vary as a function of energy. Also, we can see in detail how the ULF power change for the electron flux at different L-shell We expect these results to be relevant for the understanding of the relative role of ULF waves in the enhancements and depletions of energetic electrons in the radiation belts for condition described.</p>

scholarly journals Electron flux enhancement in the inner radiation belt during moderate magnetic storms

2007 ◽  
Vol 25 (6) ◽  
pp. 1359-1364 ◽  
Author(s):  
H. Tadokoro ◽  
F. Tsuchiya ◽  
Y. Miyoshi ◽  
H. Misawa ◽  
A. Morioka ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Electron Flux ◽  
Recovery Phase ◽  
Magnetic Activity ◽  
Magnetic Storms ◽  
Natural Phenomena ◽  
Early Recovery ◽  
Flux Enhancement ◽  
Angle Scattering ◽  
Order Of Magnitude

Abstract. During moderate magnetic storms, an electron channel (300–1100 keV) of the NOAA satellite has shown sudden electron flux enhancements in the inner radiation belt. After examinating the possibility of contamination by different energetic particles, we conclude that these electron flux enhancements are reliable enough to be considered as natural phenomena, at least for the cases of small to moderate magnetic storms. Here, we define small and moderate storms to be those in which the minimum Dst ranges between −30 and −100 nT. The electron flux enhancements appear with over one order of magnitude at L~2 during these storms. The enhancement is not accompanied by any transport of electron flux from the outer belt. Statistical analysis shows that these phenomena have a duration of approximately 1 day during the period, starting with the main phase to the early recovery phase of the storms. The flux enhancement shows a dawn-dusk asymmetry; the amount of increased flux is larger in the dusk side. We suggest that this phenomenon could not be caused by the radial diffusion but would be due to pitch-angle scattering at the magnetic equator. The inner belt is not in a stationary state, as was previously believed, but is variable in response to the magnetic activity.

scholarly journals Simulation of energy-dependent electron diffusion processes in the Earth's outer radiation belt

2016 ◽  
Vol 121 (5) ◽  
pp. 4217-4231 ◽  
Author(s):  
Q. Ma ◽  
W. Li ◽  
R. M. Thorne ◽  
Y. Nishimura ◽  
X.-J. Zhang ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Diffusion Processes ◽  
Outer Radiation Belt ◽  
Electron Diffusion ◽  
Energy Dependent

Long‐Term Dropout of Relativistic Electrons in the Outer Radiation Belt During Two Sequential Geomagnetic Storms

2020 ◽  
Vol 125 (10) ◽  
Author(s):  
H. Wu ◽  
T. Chen ◽  
V. V. Kalegaev ◽  
M. I. Panasyuk ◽  
N. A. Vlasova ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Relativistic Electrons ◽  
Outer Radiation Belt
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