Evolution of the magnetotail energetic-electron population during high-speed-stream-driven storms: Evidence for the leakage of the outer electron radiation belt into the Earth's magnetotail

We studied the evolution of ion and electron distribution functions, approximated by distributions, in the plasma sheet with the distance from the Earth using the data of the Time History of Events and Macroscale Interactions during Substorms spacecraft mission. Five events were used to calculate the main parameters of the distribution. For these events at least four spacecraft were aligned along the tail between approximately 7 and 30 R E . It was found that for the majority of events the values of increase tailward. The observed radial profiles could be related to the inner magnetosphere sources of particle acceleration and to the net tailward transport of particles. This net transport is the result of a balance between the average regular bulk transport toward the Earth and the turbulent transport by eddies in the tailward direction.

Section: Discussionmentioning

confidence: 99%

Role of turbulent transport in the evolution of the κ distribution functions in the plasma sheet

Stepanova

Антонова

2015

“…Early in the storm at the time of density recovery, the temperature drops for both types of storms. This has been interpreted as a new denser population of radiation belt electrons appearing at geosynchronous orbit with a temperature somewhat cooler than the typical temperatures for the radiation belt [ Borovsky and Denton , , ]. During the storms, the temperature of the electron radiation belt steadily increases for both types of storms.…”

Section: The Outer Electron Radiation Beltmentioning

confidence: 99%

“…Borovsky and Denton, 2010a, Figure 3]. It has been noted that the flux recovery follows the temporal trend of the radiation belt temperature rather than the trend of the radiation belt density [Borovsky and Denton, 2011]. In the days after the storm onset, the 1.1-1.5 MeV omnidirectional electron flux steadily increases for both types of storms (bottom panel): in this time period, the radiation belt temperature steadily increases (second panel) while the number density remains constant (top panel).…”

Section: The Outer Electron Radiation Beltmentioning

confidence: 99%

The differences between storms driven by helmet streamer CIRs and storms driven by pseudostreamer CIRs

Borovsky

Denton

2013

Self Cite

[1] A corotating interaction region (CIR) is formed when fast coronal hole origin solar wind overtakes slow solar wind and forms a region of compressed plasma and magnetic field. The slow wind upstream of the coronal hole fast wind can be either of helmet streamer origin or pseudostreamer origin. For a collection of 125 CIR-driven geomagnetic storms, the slow wind ahead of each CIR is examined; for those storm not containing ejecta, each CIR is categorized as a helmet streamer CIR (74 of the 125 storms) or a pseudostreamer CIR (11 of the 125 storms). Separate superposed epoch studies are performed on the two groups to discern the differences between storms driven by pseudostreamer CIRs and those driven by helmet streamer CIRs. A major difference is that pseudostreamer CIR storms tend not to have a calm before the storm, so the outer plasmasphere does not refill before storm onset, and the outer electron radiation belt does not exhibit a pre-storm decay. The superdense plasma sheet is weaker for pseudostreamer CIR storms, and the dropout of the electron radiation belt is weaker. Pseudostreamer CIR storms and helmet streamer CIR storms tend to be of the same strength as measured by the magnitude of Kp, MBI (midnight boundary index), or Dst.Citation: Borovsky, J. E., and M. H. Denton (2013), The differences between storms driven by helmet streamer CIRs and storms driven by pseudostreamer CIRs,

“…Further, the systems‐science coupling of the outer electron radiation belt to other plasma populations of the magnetosphere such as the plasma sheet and ring current [ Ebihara et al , ; Jordanova , ], the outer plasmasphere [ Borovsky and Steinberg , ; Borovsky and Denton , ], the plasmaspheric drainage plume [ Borovsky et al , ], substorm injection electrons [ Friedel et al , ], and waves driven by those populations such as ULF waves [ Ozeke et al , ], chorus [ Meredith et al , ; Summers et al , ], and electromagnetic ion cyclotron (EMIC) [ Ukhorskiy et al , ; Lazutin et al , ] has been considered; how the outer proton radiation belt fits into the coupled system has been less well considered. Of particular relevance for the present study, the evolution of the outer electron radiation belt through high‐speed stream‐driven (corotating interaction region (CIR)‐driven) storms has been repeatedly investigated [ Paulikas and Blake , ; Belian et al , ; Borovsky et al , ; Lam , ; Miyoshi and Kataoka , ; Kataoka and Miyoshi , ; Borovsky and Denton , , , , , ; McPherron et al , ; Denton et al , ], but the evolution of the outer proton radiation belt has not been studied.…”

Section: Introductionmentioning

confidence: 99%

The proton and electron radiation belts at geosynchronous orbit: Statistics and behavior during high‐speed stream‐driven storms

Borovsky

Cayton²,

Denton

et al. 2016

Self Cite

The outer proton radiation belt (OPRB) and outer electron radiation belt (OERB) at geosynchronous orbit are investigated using a reanalysis of the LANL CPA (Charged Particle Analyzer) 8‐satellite 2‐solar cycle energetic particle data set from 1976 to 1995. Statistics of the OPRB and the OERB are calculated, including local time and solar cycle trends. The number density of the OPRB is about 10 times higher than the OERB, but the 1 MeV proton flux is about 1000 times less than the 1 MeV electron flux because the proton energy spectrum is softer than the electron spectrum. Using a collection of 94 high‐speed stream‐driven storms in 1976–1995, the storm time evolutions of the OPRB and OERB are studied via superposed epoch analysis. The evolution of the OERB shows the familiar sequence (1) prestorm decay of density and flux, (2) early‐storm dropout of density and flux, (3) sudden recovery of density, and (4) steady storm time heating to high fluxes. The evolution of the OPRB shows a sudden enhancement of density and flux early in the storm. The absence of a proton dropout when there is an electron dropout is noted. The sudden recovery of the density of the OERB and the sudden density enhancement of the OPRB are both associated with the occurrence of a substorm during the early stage of the storm when the superdense plasma sheet produces a “strong stretching phase” of the storm. These storm time substorms are seen to inject electrons to 1 MeV and protons to beyond 1 MeV into geosynchronous orbit, directly producing a suddenly enhanced radiation belt population.