Depleting effects of ICME-driven sheath regions on the outer electron radiation belt

作者：Hietala H^*; Kilpua E K J; Turner D L; Angelopoulos V

来源：Geophysical Research Letters, 2014, 41(7): 2258-2265.

DOI：10.1002/2014GL059551

• radiation belts
• interplanetary coronal mass ejections
• geomagnetic storms
• space weather
• sheath regions

We study the effect of interplanetary coronal mass ejection (ICME)-driven sheath regions on relativistic outer radiation belt electron fluxes. We employ superposed epoch analysis, and, unlike previous studies, we segregate the sheath from the ejecta. We find that sheaths typically result in more than an order of magnitude decrease in the relativistic electron fluxes and that the fluxes stay below the pre-event level for more than 2 days after the sheath passage. The electron depletions are stronger for sheaths that exhibit higher power in magnetic and dynamic pressure fluctuations in the ultralow frequency range and cause larger magnetospheric compressions. Depletions are even stronger for sheaths that encompass the entire storm main phase. Our findings suggest that sheaths are effective at depleting the electron fluxes because they increase radial diffusion under magnetospheric compression conditions, thereby enhancing magnetopause shadowing losses, particularly when the Dst effect can act in concert.
Key Points Sheath region superposed separately from the ejecta Fluxes decrease by >1 order of magnitude and stay below pre-event level for >2 days Magnetopause shadowing, ULF-driven radial diffusion, and Dst effect act together

• 出版日期2014-4-16