[GEM] THE GEM MESSENGER, Volume 28, Number 41

Newsletter Editor editor at igpp.ucla.edu
Mon Aug 20 12:24:24 PDT 2018


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     THE GEM MESSENGER
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Volume 28, Number 41
Aug.20,2018

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

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Table of Contents

1. GEM 3D Ionospheric Electrodynamics and its Impact on the Magnetosphere-Ionosphere-Thermosphere Coupled System Focus Group: 2018 Workshop Report

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1. GEM 3D Ionospheric Electrodynamics and its Impact on the Magnetosphere-Ionosphere-Thermosphere Coupled System Focus Group: 2018 Workshop Report
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From: Hyunju Connor, Haje Korth, Gang Lu, and Bin Zhang (hkconnor at alaska.edu)

The 3D ionospheric electrodynamics and its impact on magnetosphere – ionosphere – thermosphere coupled system (IEMIT) focus group held two sessions at the 2018 GEM summer workshop in Santa Fe, New Mexico. The first session was jointed with the InterHemispheric approaches to understand Magnetosphere – Ionosphere Coupling (IHMIC) focus group, and the second one was a stand-alone session. Both sessions had approximately 50 attendees.

Session 1: joint with the IHMIC focus group

There were four speakers contributed to the IEMIT side of this joint session. 

Denny Oliveira investigated impact of interplanetary shocks on geomagnetically induced currents (GICs) by studying geomagnetic disturbances at the ground magnetometer stations during 547 interplanetary shock events. He suggested that high-speed and nearly frontal shocks can produce high-risk GIC across the whole latitudes. 

Hyunju Connor investigated the high-latitude thermospheric density enhancement observed on May 15 2005 when sudden enhancement of solar wind dynamic pressure (Psw) comes with the strong IMF By fluctuations. Her OpenGGCM-CTIM simulations showed that Psw enhancement is the primary source for the Joule heating and thus for the neutral density increase.

Doga Ozturk presented from the idealized BATSRUS simulations that the sudden jump and drop of solar wind pressure can produce different responses in the magnetosphere – ionosphere system. The magnetospheric compression and depression caused by the increase and decrease of Psw, respectively, produce magnetospheric flow vortices in the opposite direction, resulting in the different field-aligned currents in the ionosphere.

Kevin Pham tested impact of preconditioning on ionosphere – thermosphere system by introducing different IMF input at the beginning of simulation runs and then identical IMF input for ~12 hours. The CMIT-only simulation shows that the magnetosphere does not remember different preconditions. However, the CMIT-IPWM model suggests that the IT system remembers such preconditions and produces different ion outflows, which eventually can impact the magnetospheric memory of preconditions.

Session 2: stand-alone IEMIT session

There were seven speakers in this session, covering observations, simulations, and theory in the MIT coupling.

Marc Lessard presented the RENU2 sounding rocket observations that can unveil the neutral upwelling near the cusp. The rock passed poleward moving auroral forms and observed soft electron precipitation and enhanced electron temperature. The neutral densities below and above the rocket are also available.

Brent Sadler showed the 2D IT simulation study motivated by the RENU2 rocket observations. His model results showed that periodic soft electron precipitation can produce neutral density enhancement above 400 km altitude. 

Kristina Lynch presented the observations from Isinglass rocket mission and introduced the Auroral Reconstruction CubeSwarm (ARCS) mission concept. By flying a localized swarm of 32 cubesats over dedicated auroral imagery, ARCS can investigate strong localized ionospheric flows observed in and around the nightside discrete auroral arcs.

Christine Gabrielse presented a statistical characterization of meso-scale (30-500 km) high latitude ionosphere plasma flows collected by SuperDARN. She found more flows occur in the auroral oval than in the polar cap, and that those auroral flows have a pre-midnight preference (like substorm phenomena) whereas the polar cap flows had a post-midnight preference (like polar cap arcs). The meso-scale flow orientation had an IMF By dependence that suggested the flows were generally aligned with the background convection. She also showed that the flow width did not change under most input parameters (e.g., AL index, season), but the flow speed varied between seasons (faster during summer), AL, and F10.7 (faster in the polar cap during high F10.7).

Olga Verkhoglyadova overviewed applicability and limitation of direct current (DC) and alternationg current (AC) approaches, and future developments in our understanding of energy transport in high-latitude IT. The solar wind driving of high-latitude electrodynamics is generally considered in the DC approach and is described by an evolving set of quasi-steady-state electrostatic processes. The AC approach retains the magnetic induction term that naturally includes ultra low frequency (ULF) wave solutions and describes dynamic processes occurring at temporal scales from seconds to ~15 minutes. 

Russell Cosgrove discussed ways that using the electrostatic assumption can lead to incorrect results in ionospheric modeling.  The electromagnetic 5-moment fluid equations were solved for Alfven (and other) waves in the E region ionosphere, and it was shown that collisions can dramatically reduce the parallel wavelength. For example, a 100km transverse wavelength wave suffers 90 degrees of phase rotation in passing from 400km to 100km in altitude, and this will greatly impact the ionospheric conductance on these scales.  Effects on E region dynamos were also discussed.

Larry Lyons discussed relation between auroral zone activities and large-scale traveling ionospheric disturbances (LSTIDs). A total of 8 night observations showed that LSTIDs appear almost always during moderate substorm and streamer events. Isolated period of auroral activities leads to isolated periods of waves. Continuous auroral activities give repetitive LSTIDs.


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