Depletions of Multi‐MeV Electrons and Their Association to Minima in Phase Space Density

Drozdov, Alexander; Allison, Hayley; Shprits, Y. Y.; Usanova, Maria; Saikin, A.; Wang, Dedong

doi:10.1029/2021gl097620

Cited by 16 publications

(27 citation statements)

References 77 publications

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“…The flux of relativistic electrons trapped in the Earth's Van Allen radiation belts can vary by several orders of magnitude in response to solar wind forcing (e.g., 1 ), and a number of wave-particle interactions have been proposed as contributing to the observed dynamics. For example, chorus waves are responsible for local acceleration (e.g., see [2][3][4][5][6][7][8][9][10][11] ), longer period ultra-low frequency (ULF) waves are responsible for particle acceleration as a result of inward radial diffusion (e.g., see [12][13][14][15][16][17][18][19][20][21] ), in addition to other wave-particle interactions such as electromagnetic ion-cyclotron (EMIC) waves that are responsible for loss of radiation belt electrons (e.g., see 22,23 ), manmade VLF transmitter waves (e.g., 24 ) and plasmaspheric hiss (e.g., 25 ) are also thought to be able to scatter the electrons into the loss cone and lead to the corresponding evolution of the electron flux. In this paper, we examine the chorus wave activity that accompanies a flux-limiting process in the inner magnetosphere that occurs during geomagnetic storms, and demonstrate that the theoretical predictions of Kennel and Petschek 26 accurately depict the behaviour of waves and electron fluxes in the outer Van Allen belt.Recent work associated with the capping of ~ 10-100 keV electron flux by Olifer et al 27 has revisited the dynamics of the energetic electron population in the outer electron radiation belt, revealing evidence for an energy-dependent limit to the electron flux in the belts (see also 28 , and references therein).…”

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confidence: 99%

Intense chorus waves are the cause of flux-limiting in the heart of the outer radiation belt

Chakraborty

Mann

Watt

et al. 2022

Sci Rep

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Chorus waves play a key role in outer Van Allen electron belt dynamics through cyclotron resonance. Here, we use Van Allen Probes data to reveal a new and distinct population of intense chorus waves excited in the heart of the radiation belt during the main phase of geomagnetic storms. The power of the waves is typically ~ 2–3 orders of magnitude greater than pre-storm levels, and are generated when fluxes of ~ 10–100 keV electrons approach or exceed the Kennel–Petschek limit. These intense chorus waves rapidly scatter electrons into the loss cone, capping the electron flux to a value close to the limit predicted by Kennel and Petschek over 50 years ago. Our results are crucial for understanding the limits to radiation belt fluxes, with accurate models likely requiring the inclusion of this chorus wave-driven flux-limiting process, that is independent of the acceleration mechanism or source responsible for enhancing the flux.

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confidence: 99%

Intense chorus waves are the cause of flux-limiting in the heart of the outer radiation belt

Chakraborty

Mann

Watt

et al. 2022

Sci Rep

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“…The magnetopause erosion is however not as efficient for non‐geoeffective sheaths as for geoeffective sheaths (Kalliokoski et al., 2020), which could imply that in the inner parts of the outer belt scattering by wave‐particle interactions has a key role in causing losses. Electromagnetic ion cyclotron (EMIC) waves can scatter multi‐MeV electrons rapidly (Aseev et al., 2017; Drozdov et al., 2022; Kurita et al., 2018; Shprits et al., 2017; Usanova et al., 2014). This scattering loss can also contribute to losses during geoeffective sheaths during which EMIC wave activity is more elevated (Kalliokoski et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

Outer Radiation Belt Flux and Phase Space Density Response to Sheath Regions: Van Allen Probes and GPS Observations

et al. 2023

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Turbulent and compressed sheath regions preceding interplanetary coronal mass ejections strongly impact electron dynamics in the outer radiation belt. Changes in electron flux can occur on timescales of tens of minutes, which are unlikely to be captured by a two‐satellite mission. The recently released Global Positioning System (GPS) data set generally has shorter revisit times (at L ∼ 4–8) owing to the large number of satellites in the constellation equipped with energetic particle detectors. Investigating electron fluxes at energies from 140 keV to 4 MeV and sheaths observed in 2012–2018, we show that the flux response to sheaths on a timescale of 6 hr, previously reported from Van Allen Probes (RBSP) data, is reproduced by GPS measurements. Furthermore, GPS data enables derivation of the response on a timescale of 30 min, which further confirms that the energy and L‐shell dependent changes in electron flux are associated with the impact of the sheath. Sheath‐driven loss is underestimated over longer timescales as the electrons recover during the ejecta. We additionally show the response of electron phase space density (PSD), which is a key quantity in identifying non‐adiabatic loss from the system and electron energization through wave‐particle interactions. The PSD response is calculated from both RBSP and GPS data for the 6 hr timescale, as well as from GPS data for the 30 min timescale. The response is divided based on the geoeffectiveness of the sheaths revealing that electrons are effectively accelerated only during geoeffective sheaths, while loss commonly occurs during all sheaths.

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“…manuscript submitted to JGR: Space Physics interactions has a key role in causing losses. Electromagnetic ion cyclotron (EMIC) waves can scatter multi-MeV electrons rapidly (Usanova et al, 2014;Aseev et al, 2017;Shprits et al, 2017;Kurita et al, 2018;Drozdov et al, 2022). This scattering loss can also contribute to losses during geoeffective sheaths during which EMIC wave activity is more elevated (Kalliokoski et al, 2020).…”

Section: Accepted Articlementioning

confidence: 99%

Outer Radiation Belt Flux and Phase Space Density Response to Sheath Regions: Van Allen Probes and GPS Observations

Kalliokoski

Henderson

Morley

et al. 2022

Preprint

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GPS measurements confirm 6-hour RBSP outer belt electron flux response to ICMEdriven sheaths at 6-hour and 30-minute timescales • PSD response shows that electron energization is associated only with geoeffective sheaths but loss occurs in response to all sheaths • Impacts in electron flux and PSD presented here are related to sheaths, and the lost electrons are replenished during the early ejecta

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Depletions of Multi‐MeV Electrons and Their Association to Minima in Phase Space Density

Cited by 16 publications

References 77 publications

Intense chorus waves are the cause of flux-limiting in the heart of the outer radiation belt

Intense chorus waves are the cause of flux-limiting in the heart of the outer radiation belt

Outer Radiation Belt Flux and Phase Space Density Response to Sheath Regions: Van Allen Probes and GPS Observations

Outer Radiation Belt Flux and Phase Space Density Response to Sheath Regions: Van Allen Probes and GPS Observations

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