| Autor: |
Chen, Zewen, Su, Zhenpeng, He, Zhaoguo, Wu, Zhiyong, Dai, Guyue, Wang, Bin, Xiong, Ying, Zheng, Huinan, Cui, Jun, Wang, Yuming |
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| Zdroj: |
Geophysical Research Letters; 5/16/2022, Vol. 49 Issue 9, p1-11, 11p |
| Abstrakt: |
Earth's radiation belt relativistic electron dropouts frequently occur during the main phase of geomagnetic storms, which have been partially attributed to the ring current ion enhancements causing geomagnetic field reconfigurations. In contrast to early studies on the global radiation belt response to the ring current buildup on a timescale of several hours, we here describe a rapid, localized, significant decay of relativistic electrons driven by freshly injected energetic protons during the 27 May 2017 geomagnetic storm. Near the proton injection front, the magnetic field lines were stretched outward, with an inferred migration of their equatorial crossings by ∼0.5 RE during several minutes. Because of the betatron and Fermi decelerations, the relativistic electron fluxes decreased by 2–3 orders of magnitude with pitch‐angle distributions evolving from pancake/flat‐top type to cigar type. This rapid localized response pattern of relativistic electrons could be general over strong particle injections during both geomagnetic storms and substorms. Plain Language Summary: Relativistic electrons of the Van Allen belts pose a significant radiation hazard for both satellites and astronauts in the geospace. During geomagnetic storms, the radiation belt relativistic electron fluxes characteristically exhibit a sharp decrease at the main phase preceding a substantial increase at the recovery phase. How these relativistic electrons are depleted at the storm main phase remains not fully understood. One class of depletion processes is betatron and Fermi decelerations that act when electrons are transported outward along with the stretching of geomagnetic field lines driven by the ring current ion enhancement. On the basis of multi‐satellite observations and modeling for the 27 May 2017 geomagnetic storm, we here describe a rapid localized deceleration of relativistic electrons driven by a proton injection. The relativistic electron fluxes decreased by 2–3 orders of magnitude within several minutes on the stretched magnetic field lines near the proton injection front, different from the commonly known global radiation belt response to the ring current buildup on a timescale of several hours. This rapid localized response pattern of relativistic electrons could be general over strong particle injections that are able to stretch geomagnetic field lines during both storms and substorms. Key Points: Storm proton injection caused a significant localized stretching of magnetic field lines on a timescale of several minutesRelativistic electrons were locally decelerated through betatron and Fermi processes on the stretching magnetic field linesRelativistic electron fluxes on the same magnetic field lines decreased by 2–3 orders of magnitude (depending on pitch‐angle) [ABSTRACT FROM AUTHOR] |
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