[GEM] THE GEM MESSENGER, Volume 26, Number 37

[Newsletter Editor]

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     THE GEM MESSENGER
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Volume 26, Number 37
Sep.18,2016

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Table of Contents

1. 2016 GEM-CEDAR Workshop Report: Tail Environment and Dynamics at Lunar Distances Focus Group

2. Opportunities for Dual Incoherent Scatter Radar Experiments at Resolute Bay

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1. 2016 GEM-CEDAR Workshop Report: Tail Environment and Dynamics at Lunar Distances Focus Group
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From: Chih-Ping Wang, Andrei Runov, David Sibeck, Viacheslav Merkin, and Yu Lin (cat at atmos.ucla.edu)

The Tail Environment and Dynamics at Lunar Distances FG held two session at the 2016 GEM summer workshop. The first session is a joint session with Modeling Methods and Validation FG on mid-tail modeling challenge. The second session include presentations of recent progress on various topics of the mid-tail.

Session 1:

Modeling challenge for an event observed ARTEMIS in the mid-tail under prolonged N IMF from 13-14 Feb 2014. We focused on a few intervals during which IMF By changed direction, steady solar wind/IMF remained steady, or solar wind/IMF fluctuated slightly. Simulations using 3D hybrid code and MHD code were conducted. The MHD simulations, including GUMICS, BATS-R-US, LFM, and OpenGGCM, were conducted on NASA CCMC with lower grid resolutions and by different modelers with higher grid resolutions.

http://people.atmos.ucla.edu/cat/download/2016GEM/mid-tail%20modeling%20challenge/

Xueyi Wang presented results from Auburn University 3-D hybrid simulations. He showed the magnetotail dynamics for different steady IMF conditions. For this challenge event, the large-scale tail configuration from the hybrid simulation is found to be similar to those of the CCMC global MHD simulations.

Chih-Ping Wang compared the differences between the predictions from different CCMC global MHD simulations conducted. All the models predicted the large-scale mid-tail current sheet motion in respond to IMF By direction change, consistent with ARTEMIS observations. For steady solar wind/IMF, LFM and OpenGGCM predicted mesoscale perturbations while GUMICS and BATS-R-US did not. The perturbations in CCMC LFM are near the flanks and likely caused by Kelvin-Helmholtz vortices, while the perturbations in CCMC OpenGGCM are associated with flapping of the tail current sheet.

Ilja Honkonen compared the performance of different global MHD models in different regions from the near-Earth magnetosphere to the magnetotail.  For this event, he presented the results from GUMICS simulations. GUMICS predicted well large-scale response to IMF By direction changes and the agreement is better for higher resolution run. 

Joseph Jensen presented results from OpenGGCM with high grid resolution and compared the results with the lower grid run from CCMC OpenGGCM. The high-resolution run produced mesoscale perturbations on the flanks under steady solar wind/IMF that were not seen in the lower-resolution CCMC OpenGGCM run. The mesoscale perturbations are likely caused by waves propagating tailward along the flanks.

Slava Merkin presented results from a LFM run with grid resolution twice higher than that of the CCMC LFM run. The high-resolution run produced both K-H perturbations along the flanks and mesoscale current sheet flapping across the mid-tail. The flapping was not seen in the CCMC LFM run.

The main conclusion for this session is that higher grid resolutions are necessary to simulate mesoscale dynamics in the mid-tail. In order to catch the generation and propagation of the mesoscale perturbation to and within the mid-tail, higher grid resolutions need to be specified throughout the simulation domain, not just the mid-tail region.

Session 2:

http://people.atmos.ucla.edu/cat/download/2016GEM/June%2023%20session/

Gabor Facsko presented statistical analysis of plasma parameters and the magnetic field that were from Grand Unified Magnetosphere Ionosphere Coupling simulation (GUMICS-4) magnetohydrodynamic code near the orbit of Moon made for a time period which covers a full year. The velocity and the magnetic field downstream of the bow shock near the lunar orbit are very much like those in the solar wind. Density and temperature of the plasma are, however, strongly modified by the Earth.

Anton Artemyev presented simultaneous observations of the magnetotail current sheet from THEMIS D (r~10RE), Geotail (r~30RE), and ARTEMIS P1 (r~55RE). Distributions of plasma (ion) density and temperature along and across the magnetotail is studied for fourteen events (each event include several current sheet crossings at different downtail distances). He demonstrated that plasma temperature varies across and along the magnetotail more significant than plasma density does. This temperature variation across the tail mainly contributes to the cross tail pressure balance. 

Shin Ohtani proposed based on his model calculation and reexamination of previous observations that the poleward boundary intensification (PBI) of auroral emission is an effect of ionospheric polarization caused by a polar-cap flow channel approaching the auroral oval, rather than an ionospheric manifestation of distant reconnection.  The distant reconnection may start independently of PBIs or may be triggered by the Alfvén wave reflected at the ionosphere changes the plasma and magnetic configuration in the distant plasma sheet.  The sequence of substorm growth-phase processes in the magnetosphere and ionosphere is an important target for the Heliophysics System Observatory.

Katariina Nykyri created 2.5-D macro-scale local simulation based on ARTEMIS event which showed quasi-periodic ~10 minute oscillations of the plasma parameters at the mid-tail dusk side flank. The observations of the virtual probe in the simulation created in the magnetospheric interial frame was compared with the ARTEMIS measurements. The simulations were in good agreement suggesting that the vortex with the size of 8 RE was created by a 12-20 RE KH wave.

Miles Bengtson (an Embry-Riddle M.S student supervised by Katariina Nykyri) discussed an event in ARTEMIS data showing high tailward ion and electron flow speeds possibly originating from mid-tail reconnection site. Significant electric fields were observed during the event as well as the reversal of the electron to ion temperature ratio.

Peter Chi presented an investigation of the nature of the narrowband ion cyclotron waves at the Moon in the magnetotail using ARTEMIS observations, a type of waves first detected by the Apollo Lunar Surface Magnetometers. The combination of ARTEMIS field and particle measurements and wave modeling suggests that these waves can be generated by asymmetric velocity distributions due to (1) the absorption of plasma sheet particles by the Moon or (2) pickup ions from the lunar exosphere. ARTEMIS also detected right-handed waves at approximately the proton gyrofrequency, a different wave type associated with the ion/ion resonant instability in the PSBL previously observed by ISEE and Geotail.

Joachim Birn presented results from test particle tracing in the dynamic fields of a 3-D MHD simulation of near tail reconnection and plasmoid ejection, associated with tailward propagating “anti-dipolarization fronts” (ADFs). Tailward moving energetic ions near the plasma sheet boundary typically were accelerated close to the near-Earth x-line and ejected along the magnetic field, while energetic particles near the equatorial plane underwent more complicated trajectories with possible acceleration at multiple sites within the tailward moving plasmoid and ADF.


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2. Opportunities for Dual Incoherent Scatter Radar Experiments at Resolute Bay
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From: Robert Gillies, Roger Varney (rgillies at ucalgary.ca)

Dear Geospace Community,

Both of the Resolute Bay incoherent scatter radars are now fully operational and available for use by the geospace community. We are soliciting requests for experiments utilizing either or both of the RISR Canadian face (RISR-C) and the RISR North face (RISR-N). The University of Calgary operates RISR-C and SRI International operates RISR-N on behalf of the US National Science Foundation. The intention of both groups is to coordinate operations of the radars to optimize scientific impact and capitalize on efficiencies.  Both radars will be run collaboratively with coordination, scheduling and operations shared by the University of Calgary and SRI International. 

RISR-C and RISR-N are both electronically steerable phased array radars using the Advanced Modular Incoherent Scatter (AMISR) technology. The Resolute Bay Observatory (RBO) also includes a variety of other complementary instruments in addition to the AMISRs. Resolute Bay is located at 83° magnetic latitude, and the field of view of the two AMISRs extends from 75° magnetic latitude to the geomagnetic pole. The RBO affords unique opportunities to study polar cap and polar cap boundary phenomena. General information on the capabilities of the AMISRs is available at http://data.phys.ucalgary.ca/sort_by_project/RISR-C/documentation/RISR_information.pdf. 

Requests for experiments and questions regarding the technical and scientific capabilities of the systems should be addressed to both rgillies at ucalgary.ca and roger.varney at sri.com. All requests will be reviewed by a scheduling committee appointed by the University of Calgary, the University of Saskatchewan, and SRI International, and which will allocate radar time in the interests of both Canada and the United States. Due to the high cost of generating electricity onsite, the radars will normally run one 7-10 day continuous campaign per month consisting of multiple different experiments. Requests for experiments should include a description of the scientific goals of the experiment and justifications for the requested dates and times of day (e.g. satellite conjunctions, phenomena specific to a certain MLT sector, new moon). The radars are open to requests from researchers in any country for any scientific purpose related to atmospheric or geospace science.

Sincerely,
Robert Gillies, University of Calgary
Roger Varney, SRI International


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