Inward shift of outer radiation belt electrons as a function ofDstindex and the influence of the solar wind on electron injections into the slot region

Abstract. Radiation belt electron flux dropouts are a kind of drastic variation in the Earth's magnetosphere, understanding of which is of both scientific and societal importance. Using electron flux data from a group of 14 satellites, we report multi-satellite simultaneous observations of magnetopause and atmospheric losses of radiation belt electrons during an event of intense solar wind dynamic pressure pulse. When the pulse occurred, magnetopause and atmospheric loss could take effect concurrently contributing to the electron flux dropout. Losses through the magnetopause were observed to be efficient and significant at L ≳ 5, owing to the magnetopause intrusion into L ∼ 6 and outward radial diffusion associated with sharp negative gradient in electron phase space density. Losses to the atmosphere were directly identified from the precipitating electron flux observations, for which pitch angle scattering by plasma waves could be mainly responsible. While the convection and substorm injections strongly enhanced the energetic electron fluxes up to hundreds of keV, they could delay other than avoid the occurrence of electron flux dropout at these energies. It is demonstrated that the pulse-time radiation belt electron flux dropout depends strongly on the specific interplanetary and magnetospheric conditions and that losses through the magnetopause and to the atmosphere and enhancements of substorm injection play an essential role in combination, which should be incorporated as a whole into future simulations for comprehending the nature of radiation belt electron flux dropouts.

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Magnetospheric Response to Solar Wind Forcing: ULF Wave – Particle Interaction Perspective

10.5194/angeo-2021-57 ◽

2021 ◽

Author(s):

Qiugang Zong

Keyword(s):

Solar Wind ◽

Radiation Belt ◽

Ring Current ◽

Dynamic Pressure ◽

Plasma Heating ◽

Interplanetary Shock ◽

Wind Forcing ◽

Ulf Waves ◽

Radiation Belt Electrons ◽

The Impact

Abstract. Solar wind forcing, e.g. interplanetary shock and/or solar wind dynamic pressure pulses impact on the Earth’s magnetosphere manifests many fundamental important space physics phenomena including producing electromagnetic waves, plasma heating and energetic particle acceleration. This paper summarizes our present understanding of the magnetospheric response to solar wind forcing in the aspects of radiation belt electrons, ring current ions and plasmaspheric plasma physics based on in situ spacecraft measurements, ground-based magnetometer data, MHD and kinetic simulations. Magnetosphere response to solar wind forcing, is not just a “one-kick” scenario. It is found that after the impact of solar wind forcing on the Earth’s magnetosphere, plasma heating and energetic particle acceleration started nearly immediately and could last for a few hours. Even a small dynamic pressure change of interplanetary shock or solar wind pressure pulse can play a non-negligible role in magnetospheric physics. The impact leads to generate series kind of waves including poloidal mode ultra-low frequency (ULF) waves. The fast acceleration of energetic electrons in the radiation belt and energetic ions in the ring current region response to the impact usually contains two contributing steps: (1) the initial adiabatic acceleration due to the magnetospheric compression; (2) followed by the wave-particle resonant acceleration dominated by global or localized poloidal ULF waves excited at various L-shells. Generalized theory of drift and drift-bounce resonance with growth or decay localized ULF waves has been developed to explain in situ spacecraft observations. The wave related observational features like distorted energy spectrum, boomerang and fishbone pitch angle distributions of radiation belt electrons, ring current ions and plasmaspheric plasma can be explained in the frame work of this generalized theory. It is worthy to point out here that poloidal ULF waves are much more efficient to accelerate and modulate electrons (fundamental mode) in the radiation belt and charged ions (second harmonic) in the ring current region. The results presented in this paper can be widely used in solar wind interacting with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields.

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Simulations of the Relativistic Radiation Belt Electrons Using the VERB-3D Code

10.5194/egusphere-egu21-3802 ◽

2021 ◽

Author(s):

Dedong Wang ◽

Yuri Shprits ◽

Alexander Drozdov ◽

Nikita Aseev ◽

Irina Zhelavskaya ◽

...

Keyword(s):

Space Weather ◽

Radiation Belt ◽

Model Performance ◽

Dynamic Evolution ◽

Relativistic Electrons ◽

Outer Radiation Belt ◽

Chorus Waves ◽

Van Allen Probes ◽

Radiation Belt Electrons ◽

Simulation Results

Using the three-dimensional Versatile Electron Radiation Belt (VERB-3D) code, we perform simulations to investigate the dynamic evolution of relativistic electrons in the Earth&#8217;s outer radiation belt. In our simulations, we use data from the Geostationary Operational Environmental Satellites (GOES) to set up the outer boundary condition, which is the only data input for simulations. The magnetopause shadowing effect is included by using last closed drift shell (LCDS), and it is shown to significantly contribute to the dropouts of relativistic electrons at high $L^*$. We validate our simulation results against measurements from Van Allen Probes. In long-term simulations, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high&#8208;latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high&#8208;latitude waves can result in a net loss of MeV electrons. Variations in high&#8208;latitude chorus may account for some of the variability of MeV electrons.&#160;Our simulation results for the NSF GEM Challenge Events show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. We also perform simulations for the COSPAR International Space Weather Action Team (ISWAT) Challenge for the year 2017. The COSPAR ISWAT is a global hub for collaborations addressing challenges across the field of space weather. One of the objectives of the G3-04 team &#8220;Internal Charging Effects and the Relevant Space Environment&#8221; is model performance assessment and improvement. One of the expected outputs is a more systematic assessment of model performance under different conditions. The G3-04 team proposed performing benchmarking challenge runs. We &#8216;fly&#8217; a virtual satellite through our simulation results and compare the simulated differential electron fluxes at 0.9 MeV and 57.27 degrees local pitch-angle with the fluxes measured by the Van Allen Probes. In general, our simulation results show good agreement with observations. We calculated several different matrices to validate our simulation results against satellite observations.

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The relativistic electron response in the outer radiation belt during magnetic storms

Annales Geophysicae ◽

10.5194/angeo-20-957-2002 ◽

2002 ◽

Vol 20 (7) ◽

pp. 957-965 ◽

Cited By ~ 55

Author(s):

R. H. A. Iles ◽

A. N. Fazakerley ◽

A. D. Johnstone ◽

N. P. Meredith ◽

P. Bühler

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Wind Speed ◽

Interplanetary Magnetic Field ◽

Relativistic Electron ◽

Radiation Belt ◽

Solar Wind Speed ◽

Recovery Phase ◽

Magnetic Storms ◽

Outer Radiation Belt

Abstract. The relativistic electron response in the outer radiation belt during magnetic storms has been studied in relation to solar wind and geomagnetic parameters during the first six months of 1995, a period in which there were a number of recurrent fast solar wind streams. The relativistic electron population was measured by instruments on board the two microsatellites, STRV-1a and STRV-1b, which traversed the radiation belt four times per day from L ~ 1 out to L ~ 7 on highly elliptical, near-equatorial orbits. Variations in the E > 750 keV and E > 1 MeV electrons during the main phase and recovery phase of 17 magnetic storms have been compared with the solar wind speed, interplanetary magnetic field z-component, Bz , the solar wind dynamic pressure and Dst *. Three different types of electron responses are identified, with outcomes that strongly depend on the solar wind speed and interplanetary magnetic field orientation during the magnetic storm recovery phase. Observations also confirm that the L-shell, at which the peak enhancement in the electron count rate occurs has a dependence on Dst *.Key words. Magnetospheric physics (energetic particles, trapped; storms and substorms) – Space plasma physics (charged particle motion and accelerations)

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