[GEM] THE GEM MESSENGER, Volume 28, Number 42

Tue Aug 21 13:48:55 PDT 2018

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     THE GEM MESSENGER
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Volume 28, Number 42
Aug.21,2018

Announcement submission website: http://aten.igpp.ucla.edu/gem/messenger_form/

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Table of Contents

1. GEM Magnetic Reconnection in the Age of the Heliophysics System Observatory Focus Group: 2018 Workshop Report

2. Tplot Essentials with MMS Data

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1. GEM Magnetic Reconnection in the Age of the Heliophysics System Observatory Focus Group: 2018 Workshop Report
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From: Rick Wilder, Shan Wang, Michael Shay, and Anton Artemyev (frederick.wilder at lasp.colorado.edu)

This was the first year of the focus group, which aims to use recent spacecraft missions and ground assets to further elucidate both the kinetic physics and the system context of magnetic reconnection in the Earth’s magnetosphere. We had three sessions, one which was joint with the Dayside Kinetics focus group. The sessions were well attended and the talks spurred exciting discussion.

Session 1: This session focused on the local kinetic physics of magnetic reconnection. Blake Wetherton showed that MMS data provided direct confirmation of the Le et al 2009 equations of state for guide field reconnection. These equations can be used to model electrons in a hybrid simulation, and reproduce observations by MMS. Misha Sitnov argued that the conventional MHD parameter, the Joule heating rate j*E’, cannot distinguish between electron and ion dissipation and it can be replaced by new parameters known as the “Pi-D” parameters. Tetsuo Motoba showed that the probe spacing on MMS might be too small to evaluate ion dissipation in the tail. Rick Wilder showed that parallel electric fields were important for dissipation in the “outer” electron diffusion region (EDR), and became dominant when the guide field exceeded 0.3 times the reconnecting electric field. Prayash Sharma Pyakurel showed properties of electron-only reconnection using pic simulations. The transition from electron only to ion-coupled reconnection is not sudden, but a gradual transition as the width of the exhaust increases. Haoming Liang showed results from an initial study to develop and apply kinetic entropy as a diagnostic in collisionless particle-in-cell (PIC) simulations in order to address irreversible dissipation. Kinetic entropy was shown to be an indicator of non-Maxwellian distributions, diffusion regions and dissipation. Finally, Kyunghwan Dokgo presented 2D PIC simulations that show electron crescent distributions could generate upper hybrid waves near the EDR by beam-plasma interaction processes.

Session 2: The second session was on the global physics of magnetic reconnection, with special emphasis on the Earth’s magnetotail. Chih-Ping Wang showed evidence for magnetic reconnection through observations of distant tail plasma flows using ARTEMIS on 6 June 2017. Anton Artemyev showed conjugate observations between MMS and ARTEMIS during a mid-tail magnetic reconnection event. Andrei Runov showed THEMIS (7<R<25 RE) and ARTEMIS (~60 RE) observations of earthward and tailward rapid flux transport (RFT) events, which were interpreted as near-Earth reconnection ejecta. Comparisons of plasma properties and particle spectra revealed that ions populations within earth- and tail-ward RFTs are originated at R~25 - 30 RE, which is the most probable location of the near-Earth reconnection site. Chris Bard presented a new GPU-accelerated Hall MHD magnetosphere code and briefly showed results from a Ganymede-sized Earth-like (supersonic) magnetosphere, including an asymmetric out-of-plane B quadrupolar pattern. Joo Hwang presented MMS observations of guide-field magnetic reconnection, which occurred right after tail current sheet flapping, as well as an electron scale vortex embedded in the magnetotail flux rope. The electron vortex was accompanied by a large dissipative DC electric field (>250 mV/m) toward the vortex center. Non-linear electron phase space holes are observed to drift toward an X-line. 

Session 3: This was a joint session with the Dayside Kinetics focus group, and revolved around magnetic reconnection at the Earth’s magnetopause and in the Earth’s magnetosheath. Brian Walsh used global MHD simulations to discuss reconnection spreading at the dayside magnetopause, and showed that a typical MHD front moving through the magnetosheath and draping along the magnetopause is sufficiently fast and would likely not limit the spreading speed of reconnection. Mike Shay presented results from MMS that have shown reconnection occurring in the turbulent magnetosheath. The reconnection events found, however, are “electron-only” reconnection, where the ions do not participate in the reconnection process. Sarah Vines showed comparisons between the expected reconnection electric field derived from AMPERE and the LFM-MIX model and observations by MMS, and found the rates are on the order of 0.5 and 1 mV/m and were generally consistent. Allison Jaynes showed election enhancements up to over 100 keV in concert with elevated power in the whistler mode wave band during many crossings by MMS of the low latitude boundary layer. There are often intense parallel electric fields observed along with these signatures, indicating a non-linear component to the whistler mode waves and pointing towards the potential acceleration mechanism. Jason Shuster demonstrated the ability of the MMS Fast Plasma Instrument to compute terms in the Vlasov equation. Techniques for determining spatial and velocity-space gradients of the distribution function from the skymaps provided by FPI were presented and applied to thin current sheet observations in the magnetosheath. In support of the upcoming Solar wind - Magnetosphere - Ionosphere Link Explorer (SMILE), Hyunju Connor suggested an equation that represents magnetopause motion as a function of magnetopause reconnection rate and solar wind dynamic plasma pressure. This equation will help the SMILE team to extract the reconnection rate from the observable magnetopause motion. Ari Le presented a set of 3D fully kinetic simulations matching plasma parameters of three different MMS magnetopause diffusion region encounters with varying guide fields. Lower hybrid drift fluctuations contributed to electron transport and heating, while the anomalous dissipation in Ohm's law was very weak.

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2. Tplot Essentials with MMS Data
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From: Eric Grimes, Jim Lewis, Vassilis Angelopoulos and the SPEDAS team (egrimes at igpp.ucla.edu)

The SPEDAS development team invites you to a webinar we'll be holding on Wednesday, August 29, 2018 at 10AM Pacific / 1PM Eastern. The focus of this webinar will be on Tplot.

Time: Wednesday, August 29, 10:00am-12:00pm Pacific
URL: https://uclaigpp.webex.com/uclaigpp
Meeting name = Tplot Essentials with MMS Data
Password = MMS-tplot-5
Phone to use: 510-643-3817
Conference ID/pass = none; first person hears the ring, second starts the telecon

Tentative agenda:
1) Basics
2) Tplot options
3) Tplot tools
4) Export data
5) Saving figures

Eric Grimes (egrimes at igpp.ucla.edu), Jim Lewis, Vassilis Angelopoulos and the SPEDAS team 

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