Suprathermal Electron Acceleration by a Quasi-perpendicular Shock: Simulations and Observations

Abstract. We study one event of reconnection onset associated to a small substorm on 27 September 2006 by using Cluster observations at inter-spacecraft separation of about 10 000 km. We focus on the acceleration of suprathermal electrons during different stages of reconnection. We show that several distinct stages of acceleration occur: (1) moderate acceleration during reconnection of pre-existing plasma sheet flux tubes, (2) stronger acceleration during reconnection of lobe flux tubes, (3) production of the most energetic electrons within dipolarization fronts (magnetic pile-up regions). The strongest acceleration is reached at the location of Bz maxima inside the magnetic pile-up region where the reconnection jet stops. Very strong localized dawn-dusk electric field are observed within the magnetic pile-up regions and are associated to most of the magnetic flux transport.

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Recent scientific findings based on high-resolution core plasma imaging of the ionosphere with Swarm and ePOP

10.5194/egusphere-egu2020-12192 ◽

2020 ◽

Author(s):

David Knudsen

Keyword(s):

High Resolution ◽

Large Scale ◽

Electron Acceleration ◽

Alfven Waves ◽

Distribution Functions ◽

Alfvén Waves ◽

Topside Ionosphere ◽

High Time Resolution ◽

Ion Heating ◽

Suprathermal Electron

The Thermal Ion Imagers on Swarm A-C, and the Suprathermal Electron/Ion Imager on ePOP (now &#8220;Swarm-E&#8221;) provide a unique view of charged particle distribution functions in the ionosphere at high time resolution (up to 100 images/s). Through high resolution, CCD-based imaging (~3000 pixels/image), ion drift velocity is derived from these images at a resolution of 20 m/s or better, and in general agreement with velocities derived from ground based radars [1] and an empirical convection model [2]. This talk reviews recent scientific applications of this technique, which are wide-ranging and include mechanisms of ion heating and upflow [3,4], M-I coupling via Alfven waves [5,6],&#160;electron acceleration and heating by Alfven waves [7,8, 9], intense plasma flows associated with &#8220;Steve&#8221; [10,11], and electrodynamics of large-scale FAC systems[ 12], among others. In addition, future opportunities made possible by these data will be discussed.[1] Koustov et al. (2019), JGR,&#160;https://doi.org/10.1029/2018JA026245[2] Lomidze et al. (2019), ESS,&#160;https://doi.org/10.1029/2018EA000546[3] Shen and Knudsen (2020a), On O+ ion heating by BBELF waves at low altitude, JGR, in revision.[4] van Irsel et al. (2020), Highly correlated ion upflow and electron temperature variations in the high latitude topside ionosphere, submitted to JGR.[5] Pakhotin et al. (2020), JGR,&#160;https://doi.org/10.1029/2019JA027277[6] Wu et al. (2020a), Swarm survey of Alfvenic fluctuations and their relation to nightside field-aligned current and auroral arcs systems, JGR, in revision.[7] Liang et al. (2019), JGR,&#160;https://doi.org/10.1029/2019JA026679[8] Wu et al. (2020b), e-POP observations of suprathermal electron bursts in the ionospheric Alfven resonator, GRL, submitted. &#160;[9] Shen and Knudsen (2020b), Suprathermal electron acceleration perpendicular to the magnetic field in the topside ionosphere, JGR, in press.[10] Archer et al. (2019), JGR,&#160;https://doi.org/10.1029/2019GL082687[11] Nishimura et al. (2019), JGR,&#160;https://doi.org/10.1029/2019GL082460[12] Olifer et al (2020), Swarm observations of dawn/dusk asymmetries between Pedersen conductance in upward and downward FAC regions, submitted to JGR.&#160;

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