Cold Plasmaspheric Electrons Affected by ULF Waves in the Inner Magnetosphere: A Van Allen Probes Statistical Study

Abstract

Six years of Van Allen Probes data are used to investigate cold plasmaspheric electrons affected by ultralow‐frequency (ULF) waves in the inner magnetosphere (L<7) including spatial distributions, occurrence conditions, and resonant energy range. Events exhibit a global distribution within L= 4–7 but preferentially occur at L∼5.5–7 in the dayside, while there is higher occurrence rate in the duskside than dawnside. They can occur under different geomagnetic activities and solar wind velocities (VS), but the occurrence rates are increasing with larger AE, |SYMH|, and VS. These features are closely associated with the generation and propagation of ULF waves in Pc4 (45–150 s) and Pc5 (150–600 s) bands. Combined with electron observations from HOPE instrument, the resonant energies inferred from wave power indicate that cold electrons at ones to hundreds of electron volts can be affected by ULF waves. This study may shed new light on further investigations on the acceleration and transportation of cold plasmaspheric particles that would affect plasmaspheric material release to the Earth's magnetosphere and instabilities for exciting various waves.

Magnetospheric Response to Solar Wind Forcing: ULF Wave – Particle Interaction Perspective

“…For a given plasma electron with energy between 1 eV to 1 keV, the drift-bounce resonant conditions for N = 1 and N = 2 can be satisfied with a ULF wave number |m| <100 [Ren et al, 2017b[Ren et al, , 2018[Ren et al, , 2019b]. As we can see from Figure 20, a sharp enhancement at SYM-H index has been observed, indicating the interplanetary shock arrival.…”

Even moderate geomagnetic pulsations can cause fluctuations of &lt;i&gt;fo&lt;/i&gt;F2 frequency of the auroral ionosphere

“…It is modulated by intensive ultralow-frequency (ULF) waves, and this was a topic of numerous studies. Clear features of Pc5 pulsations in the Doppler velocities of the Flayer ionospheric irregularities were found by Ruohoniemi et al (1991) using coherent-scatter radar observations. Wright et al (1997) analyzed ionospheric signatures of auroral Pc4-5s with Doppler sounding.…”

Interaction between long-period ULF waves and charged particle in the magnetosphere: theory and observations (overview)

“…Действительно, если начальное положение частицы таково, что в течение первого полупериода она по-лучает энергию от волны, то в целом происходит ее ускорение: хотя в течение следующего полупериода частица теряет энергию, но ввиду уменьшения величины поля из-за затухания волны это уменьшение не компенсирует увеличение энергии за время первого полупериода. Расчет изменения энергии частицы в этом случае произведен в работе [Zhou et al, 2016].…”

“…Примеры модуляции потоков протонов при баунс-дрейфовом резонансе с волной можно найти, например, в ра-ботах [Liu et al, 2013;Le et al, 2017;Min et al, 2017;Takahashi et al, 1990Takahashi et al, , 2018bWang et al, 2021]. B статьях [Yang et al, 2011;Ren et al, 2016] даны примеры модуляции потоков ионов кислорода. В работе [Pokhotelov et al, 2000b] показано, что потоки частиц, модулированные в баунс-дрейфовом резонансе, могут оказывать обратное влияние на сами волны.…”