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Origin of low proton-to-electron temperature ratio in the Earth's plasma sheet

Abstract : We study the proton-to-electron temperature ratio (Tp/Te) in the plasma sheet (PS) of the Earth's magnetotail using 5 years of Cluster observations (2001-2005). The PS intervals are searched within a region defined with -19 < X ≤ -7 RE and |Y| < 15 RE (GSM) under the condition |BX| ≤ 10 nT. One hundred sixty PS crossings are identified. We find an average value of p/Te> 6.0. However, in many PS intervals Tp/Te varies over a wide range from a few units to several tens of units. In 86 PS intervals the Tp/Te decreases below 3.5. Generally, the decreases of Tp/Te are due to some increase of Te while Tp either decreases or remains unchanged. In the majority of these intervals the Tp/Te drops are observed during magnetotail dipolarizations. A superposed epoch analysis applied to these events shows that the minimum value of Tp/Te is observed after the dipolarization onset during the "turbulent phase" of dipolarization, when a number of transient BZ pulses are reduced, but the value of BZ is still large and an intensification of wave activity is observed. The Tp/Te drops, and associated increases of Te often coincide either with bursts of broadband electrostatic emissions, which may include electron cyclotron harmonics, or with broadband electromagnetic emission in a frequency range from proton plasma frequency (fpp) up to the electron gyrofrequency (fce). These findings show that the wave activity developing in the current sheet after dipolarization onset may play a role in the additional electron heating and the associated Tp/Te decrease.
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Submitted on : Monday, May 16, 2022 - 4:49:27 PM
Last modification on : Monday, July 4, 2022 - 9:29:55 AM

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E. E. Grigorenko, E. A. Kronberg, P. W. Daly, N. Yu. Ganushkina, B. Lavraud, et al.. Origin of low proton-to-electron temperature ratio in the Earth's plasma sheet. Journal of Geophysical Research: Space Physics, 2016, 121, pp.9985-10. ⟨10.1002/2016JA022874⟩. ⟨insu-03669418⟩

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