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Estimating Electron Temperature and Density Using Van Allen Probe Data: Typical Behaviour of Energetic Electrons in the Inner Magnetosphere
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  • Dovile Rasinskaite,
  • Clare E. J. Watt,
  • Colin Forsyth,
  • Andrew W Smith,
  • Christian J. Lao,
  • Suman Chakraborty,
  • Justin C. Holmes,
  • Gian Luca Delzanno
Dovile Rasinskaite
Northumbria University

Corresponding Author:[email protected]

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Clare E. J. Watt
Northumbria University
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Colin Forsyth
University College London
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Andrew W Smith
Northumbria University
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Christian J. Lao
University College London
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Suman Chakraborty
Northumbria University
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Justin C. Holmes
Los Alamos National Laboratory
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Gian Luca Delzanno
Los Alamos National Laboratory (DOE)
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Abstract

Earth’s inner magnetosphere contains multiple electron populations influenced by different factors. The cold electrons of the plasmasphere, warm plasma that contributes to the ring current, and the relativistic plasma of the radiation belt often seem to behave independently. Using omni-directional flux and energy measurements from the HOPE and MagEIS instruments aboard the Van Allen Probes, we provide a detailed density and temperature description of the inner magnetosphere, offering a comprehensive statistical analysis of the entire Van Allen Probe era. While number density and temperature data at geosynchronous orbit are available, this study focuses on the inner magnetosphere (2 < L∗ < 6). Values of density and temperature are extracted by fitting energy and phase space density to obtain the distribution function. The fitted distributions are related to the zeroth and second moments to estimate the number density and temperature. Analysis has indicated that a two Maxwellian fit is sufficient over a wide range of L∗ and that there are two independent plasma populations. The more energetic population has a median number density of approximately 1.2 × 104 m−3 and a temperature of around 130 keV, with a temperature peak observed between L* = 4 and L*= 4.5. This population is relatively uniform in MLT. In contrast, the less energetic warm electron population has a median number density of about 2.5 × 104 m−3 and a temperature of 7.4 keV. Strong statistical trends in density and temperature across both L* and MLT are presented, along with potential sources driving these variations.
01 Nov 2024Submitted to ESS Open Archive
01 Nov 2024Published in ESS Open Archive