[GEM] THE GEM MESSENGER, Volume 28, Number 49

Newsletter Editor editor at igpp.ucla.edu
Fri Oct 12 10:30:56 PDT 2018


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     THE GEM MESSENGER
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Volume 28, Number 49
Oct.12,2018

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

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Table of Contents

1. GEM Geospace Systems Science (GSS) Focus Group: 2018 Workshop Report

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1. GEM Geospace Systems Science (GSS) Focus Group: 2018 Workshop Report
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From: Joe Borovsky, Bill Lotko, Vadim Uritsky, and Juan Alejandro Valdivia (jborovsky at spacescience.org)

The Geospace Systems Science Focus Group held its fifth-year sessions at the GEM Summer Workshop in Santa Fe. Two sessions were held, entitled “System Science Progress” and “Discussion: The Future of Geospace Systems Science”.

8 widely varied presentations were given in the session “Progress in System Science”.

Brian Walsh spoke about solar wind propagation from an upstream solar wind monitor and uncertainties in the solar wind that hits the Earth. In solar-wind-driven models, putting in statistical uncertainties in the solar-wind parameters increases the quality of the model outputs. An example given was magnetopause location prediction.

Misha Sitnov talked about building magnetospheric models from spacecraft measurements wherein the measurements are sorted by phase of geomagnetic activity. An example was an examination of the substorm current wedge, which is highlighted by subtracing the curl of an expansion-phase model from the curl of a growth-phase model. The model-subtraction result showed remarkable agreement with theoretical pictures of the substorm current wedge.

Alexander Lipatov spoke on “Effects of transmitted interplanetary impulse interaction with plasmaspheric plume. First results from 3-D hybrid kinetic modeling”. Using hybrid simulations he showed an examination of the reaction of a plasmaspheric drainage plume to the passage of an interplanetary shock past the Earth.

Shin Ohtani spoke about the link between the auroral streamer and a plasma-sheet flow channel, in the analogy to an electrical circuit. Time constants in an electrical circuit analogy to the magnetotail connected to the ionosphere were matched with time constants for auroral streamers. It was found that the time constants depend on the geometry of the plasma-sheet flow and the ionospheric-footprint shape of the flow.

Lynn Kistler spoke about the University of New Hampshire project to discern whether auroral ionospheric outflow feedback plays a role in creating sawtooth oscillations of the magnetosphere. Predictions are that auroral outflow of ions should be the source of ions in the plasma sheet. Spacecraft measurements are not supporting the prediction: (1) the source of oxygen ions appears to be the cusp (where there can be no feedback with the tail) and (2) the timing of the oxygen density is wrong for producing sawtooth oscillations. A reanalysis of FAST data is underway to look at FAST observations of outflow.

Katariina Nykyri spoke about the nonadiabatic heating in Kelvin-Helmholtz vortices on the flanks of the magnetosphere. There is an observed dawn-dusk asymmetry in the plasma sheet temperature that cannot be explained by asymmetries in the magnetosheath source. The plasma-sheet temperature asymmetry could be caused by asymmetries in the occurrence and behavior of Kelvin-Helmholtz waves on the magnetopause related to the average Parker-spiral orientation of the solar-wind magnetic field. Examination of ion distribution functions in hybrid simulations of Kelvin-Helmholtz showed non-adiabatic heating.

Joe Borovsky talked about the creation of an aggregate index of magnetospheric activity. Using canonical correlation analysis between the solar wind and the magnetospheric, an aggregate index of solar-wind-driven magnetospheric activity was derived. The aggregate index is built on multiple geomagnetic indices plus properties of the plasma sheet and the time since the last substorm onset.

Ankush Bhaskar gave a presentation on “Radiation belt response to interplanetary reverse shock”. Energetic-electron and -proton measurements on a geosynchronous spacecraft were examined. The particle fluxes were observed to drop when the ram pressure of the solar wind suddenly drops as the reverse shock passes the Earth. Two competing effects act on the energetic-particle fluxes. (1) The magnetosphere expands as the ram pressure drops and radial gradients in the particle populations should lead to an increase in observed fluxes. (2) Adiabatic cooling of the particle populations as the magnetosphere expands should lead to a decrease in the observed fluxes. The conclusion is that adiabatic effects are important during the magnetospheric expansion. 

The session “Discussion: The Future of Geospace Systems Science” was an audience-participation discussion. A number of topics were raised, including the effect of the past history of the magnetosphere on the reaction of the magnetosphere to the solar wind, the impact of one subsystem of the magnetosphere on the entire system, the increasing importance of machine learning and data mining, and the lack of metric tools for magnetospheric physics. The audience maintained that there is an active need for systems science approaches as part of the activities of the magnetospheric-research community.


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