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

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.

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Wavelet and Cross-Correlation Analysis of Relativistic Electron Flux with Sunspot Number, Solar Flux, and Solar Wind Parameters

Journal of Nepal Physical Society ◽

10.3126/jnphyssoc.v6i2.34865 ◽

2020 ◽

Vol 6 (2) ◽

pp. 104-112

Author(s):

P. Poudel ◽

N. Parajuli ◽

A. Gautam ◽

D. Sapkota ◽

H. Adhikari ◽

...

Keyword(s):

Solar Wind ◽

Relativistic Electron ◽

Sunspot Number ◽

Radiation Belt ◽

Solar Wind Velocity ◽

Cross Correlation ◽

Electron Flux ◽

Solar Flux ◽

Cross Correlation Analysis ◽

Solar Wind Parameters

The Geostationary Operational Environmental Satellites (GOES) have been monitoring the Earth's radiation environment and is providing the electron flux data (of energy >0.8 MeV, >2 MeV, and >4 MeV) by means of a connected sensor subsystem. Relativistic electron flux is one of the components of the radiation belt which not only affects the electrical system in satellites but also has an impact on Earth’s upper atmospheric climatic variation. We have carried out a study to determine the relation of sunspot number (R), solar flux (F10.7), and solar wind parameters i.e., solar wind velocity (Vsw), plasma density Nsw), the southern component of the interplanetary magnetic field (IMF-Bz), Plasma temperature (Tsw) with relativistic electron flux of energy >0.8 MeV, >2 MeV, and >4 MeV in outer radiation belt using the data of 24 years (1996-2020) covering solar cycle 23 and 24. Time series analysis, Cross-correlation and wavelet analysis techniques have been used in this study. The time series plot displayed that the radiation is occupied mostly by electron flux of energy less than 4 Mev and solar cycle 23 (1996-2008) was strong to produce more intensity of relativistic electron flux of all energy in comparison to cycle 24 (2008-2019). Results from cross-correlation analysis illustrated that Bz has no significant impact on the enhancement of relativistic electron flux of any energy range in the radiation belt. Whereas other studied parameters have a positive correlation with relativistic electron flux, but with significantly different coefficient values for different energy. We found that electron flux >0.8 MeV and >2 MeV has a strong positive association with sunspot number, solar flux, solar wind velocity, plasma density and temperature whereas weak correlation with electron flux of energy >4 MeV. This result leads us to conclude that solar activity and solar parameters have greater influence in producing relativistic electron flux of energy ~ 0.8-4 MeV, than of flux > 4 MeV. The study made to observe the distribution of relativistic electrons in radiation belt with time through continuous wavelet analysis showed that electron flux of energy >0.8 has a higher periodicity in comparison to the flux of other energy ranger.

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

10.5194/egusphere-egu21-5977 ◽

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

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.

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Relativistic electron flux dropouts in the outer radiation belt associated with corotating interaction regions

Journal of Geophysical Research Space Physics ◽

10.1002/2015ja021003 ◽

2015 ◽

Vol 120 (9) ◽

pp. 7404-7415 ◽

Cited By ~ 4

Author(s):

C.‐J. Yuan ◽

Q.‐G. Zong ◽

W.‐X. Wan ◽

H. Zhang ◽

A.‐M. Du

Keyword(s):

Relativistic Electron ◽

Radiation Belt ◽

Electron Flux ◽

Outer Radiation Belt ◽

Corotating Interaction Regions ◽

Interaction Regions

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

10.5194/egusphere-egu2020-19607 ◽

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

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, Est (the minimum energy at Lst where the inner boundary starts to exhibit an S-shaped form), and the radial width of S-shaped boundary (&#916;L) 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) &#916;L 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 Est 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.

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