Contribution of ULF Wave Activity to the Global Recovery of the Outer Radiation Belt During the Passage of a High‐Speed Solar Wind Stream Observed in September 2014

Silva, L A Da ; Sibeck, D ; Alves, L R ; Souza, V M ; Jauer, P R ; Claudepierre, S G ; Marchezi, J P ; Agapitov, O ; Medeiros, C ; Vieira, L E A(National Institute for Space Research, Sao Jose dos Campos, Brazil)

关键词: ADIABATIC EQUATIONS;    EARTH MAGNETOSPHERE;    EXTREMELY LOW FREQUENCIES;    GEOMAGNETISM;    INTERPLANETARY MAGNETIC FIELDS;    MAGNETIC FIELDS;    MAGNETOHYDRODYNAMIC WAVES;    OUTER RADIATION BELT;    PARTICLE MOTION;    RADIATION BELTS;    RELATIVISTIC ELECTRON BEAMS;    SOLAR ACTIVITY EFFECTS;    SOLAR WIND;    SPACE DENSITY;    TROPICAL REGIONS;   

RP-ID  :  GSFC-E-DAA-TN70790

学科分类：空间科学

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

Energy coupling between the solar wind and the Earth's magnetosphere can affect the electron population in the outer radiation belt. However, the precise role of different internal and external mechanisms that leads to changes of the relativistic electron population is not entirely known. This paper describes how ultralow frequency (ULF) wave activity during the passage of Alfvenic solar wind streams contributes to the global recovery of the relativistic electron population in the outer radiation belt. To investigate the contribution of the ULF waves, we searched the Van Allen Probes data for a period in which we can clearly distinguish the enhancement of electron fluxes from the background. We found that the global recovery that started on 22 September 2014, which coincides with the corotating interaction region preceding a high‐speed stream and the occurrence of persistent substorm activity, provides an excellent scenario to explore the contribution of ULF waves. To support our analyses, we employed ground‐ and space‐based observational data and global magnetohydrodynamic simulations and calculated the ULF wave radial diffusion coefficients employing an empirical model. Observations show a gradual increase of electron fluxes in the outer radiation belt and a concomitant enhancement of ULF activity that spreads from higher to lower L‐shells. Magnetohydrodynamic simulation results agree with observed ULF wave activity in the magnetotail, which leads to both fast and Alfven modes in the magnetospheric nightside sector. The observations agree with the empirical model and are confirmed by phase space density calculations for this global recovery period.