[GEM] THE GEM MESSENGER, Volume 27, Number 40

[Peter Chi]

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     THE GEM MESSENGER
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Volume 27, Number 40
Aug.28,2017

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

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Table of Contents

1. 2017 GEM Workshop Report: Quantitative Assessment of Radiation Belt
Modeling Focus Group

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1. 2017 GEM Workshop Report: Quantitative Assessment of Radiation Belt
Modeling Focus Group
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From: Weichao Tu, Wen Li, Jay Albert, and Steve Morley (Focus Group
Leaders) (wetu at mail.wvu.edu)

In the 2017 GEM Summer Workshop, “Quantitative Assessment of Radiation Belt
Modeling” (QARBM) Focus Group held four sessions on Wednesday June 21st and
Thursday June 22nd. All of the sessions were well-attended with helpful
discussions. There were 39 scheduled short talks over the 4 sessions,
covering a wide range of topics, as listed below:

Session 1 - “Observations of radiation belt processes”

In the first session ten talks were presented on the observational studies
of the dynamical processes in the radiation belts based on the long-term
Van Allen Probes data and the new data from MMS, Lomonosov, etc. The
session starts with three presentations on the long-term or statistical
studies of radiation belt electrons, with topics including: the long-term
perspective on outer belt electrons by comparing Van Allen Probes era with
the previous two solar cycles, untangling the solar wind drivers of
radiation belt using an information theoretical approach, and statistical
studies on the peaks in electron phase space densities. Then the following
three talks focused on the observed loss of radiation belt electrons,
including detailed event studies on the radiation belt dropouts observed by
Van Allen Probes to understand the underlying loss mechanisms, studies
showing new signatures of ultrarelativistic electron loss in the heart of
the Earth's radiation belts, and new observations of electron precipitation
by the ELFIN-L instrument on Lomonosov Spacecraft. The remaining four talks
in the session discussed the observed properties of various magnetospheric
waves, including the statistics of low frequency hiss, estimation of the
plasmasphere electron densities from hiss wave observations, the phase
coherency scales of individual chorus elements and the greater chorus
active region observed by Van Allen Probes and MMS, and EMIC waves observed
by the Van Allen Probes.

Session 2 - “Modeling of local processes and transport”

This session focused on various plasma excitations and their detailed
effects on energetic electrons. Oscillations in electron flux seen by Van
Allen Probes were shown and analyzed in terms of radial diffusion
processes, presumably driven by ULF waves. One talk focused on the loss of
relativistic and ultra-relativistic radiation belt electrons using
quasi-linear diffusion by EMIC waves, while in another talk transport
coefficients for EMIC waves were obtained directly from test particle
simulations and used in a modified Fokker-Planck equation. A three-wave
coupling mechanism for the generation of highly oblique chorus waves was
presented, and other talks treated diffusion coefficients for such waves
computationally and analytically. Particle-in-cell (PIC) simulations of the
generation of magnetosonic waves were shown, as were LAPD and PIC findings
of electrostatic waves generated along with whistler-mode waves. Finally,
broadband electrostatic turbulence was discussed and interpreted as phase
space electron holes, and diffusion coefficients analogous to those for
upper band chorus waves were presented.

Session 3 - “Global modeling, metrics and validation”

This session was joint with the “Modeling Methods and Validation” FG. There
were eleven presentations, with discussion emphasizing the need for metrics
and validation methods that can be used to quantitatively assess the global
modeling of radiation belt dynamics. The session started with an overview
talk on the global radiation belt modeling, metrics and validation, an
introduction on the existing and new measures of model performance, and a
brief comparison between the different metrics. Following those metrics
talks, modelers presented their new modeling results and expressed their
interests in testing those proposed metrics with their results. One talk
presented the global validation of the reduced Fokker Planck computations
of radiation belts dynamics. Two talks discussed the newly developed
magnetic field models, including the latest TS07D model and the
event-specific magnetic field models by fitting to in-situ data. On the
simulation of the radiation belt dynamics, one talk focused on simulating
the electron precipitation loss observed by multiple NOAA POES satellites
using a drift-diffusion model; one talk used the MHD-test particle
simulation to simulate the prompt electron acceleration by the 17 March
2015 interplanetary shock; and the remaining three talks simulated the
global dynamics of radiation belt electrons based on various Fokker-Planck
models, such as the CIMI model with new applications of whistler wave
distribution models, the UCLA 3D diffusion model in modeling diffusive
transport of 100s keV electrons in the slot region, and the long-term VERB
code simulation with parametrized EMIC waves.

Session 4 - “New challenge results and plans”

The final session consists of nine presentations and extensive discussion
focusing on new results from multi-satellite observations and “QARBM”
challenge events. One talk showed the statistical study of spatial extent
of relativistic electron precipitation, and another talk discussed a
statistical examination of favorable plasma conditions concerning EMIC wave
excitation. Interesting wave characteristics were also presented including
Langmuir waves modulated by rising-tone chorus, response of whistler mode
waves to interplanetary shocks, and whistler wave growth during ICME and
CIR-driven storms. Two other talks discussed the construction of electron
density in the inner magnetosphere using neural network. Recent updates on
the quantitative assessment of “QARBM” challenge events were presented for
the “dropout” and “enhancement” events respectively. The final presentation
of the session also provided an overview of the existing community
resources for the challenge events, followed by an open discussion on the
missing resources for the challenge events, approaches to assess modeling
results with various metrics, and plans for FG activities over the next
year.


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The Geospace Environment Modeling (GEM) program is sponsored by the
Division of Atmospheric and Geospace Sciences (AGS) of the National Science
Foundation (NSF).

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