Proposal for a GEM Focus Group on “Geospace System”
We propose to initiate a GEM focus group (FG) to undertake a global, system-dynamics study
of the coupled solar wind-magnetosphere-ionosphere-thermosphere system. The coupled system is
identified simply as the geospace system (GS).
Motivation
The proposal responds to two circumstances: first, 50 years of magnetospheric research have
shown the geospace system to be interactively coupled in multiple ways from the solar wind to the
thermosphere; and second, as GEM continues to move in its long-range program from the ‘divideand-conquer’ stage to the more challenging synthesis stage, a focus group devoted to problems of the
coupled system will leverage scientific progress in each of the GEM research areas and their evolving
focus groups. The magnitude of the task to comprehend the global system in its coupled complexity
is almost certainly too great for a single, scientist-centered research team and probably too great for
the multiple teams of a single institution. Instead it would seem to require a sustained collaborative
effort by experts of manifold specialties distributed among many institutions. It might even take the
combined collaboration of the GEM community and a sizable portion of the CEDAR community.
An open planning session was held at the 2009 GEM Workshop in Snowmass to explore community interest in a focus group on the geospace system. It was decided that the proposed FG naturally
resides within the broad purview of the GGCM Research Area. The planning session identified FG
objectives, desirable attributes of GS projects, prospective GS topical studies, and organization of FG
efforts. These ideas are incorporated in this proposal.
Objectives
The primary objectives of the FG are:
1) To investigate problems in which the coupled solar wind-magnetosphere-ionosphere-thermosphere behaves as an integral system and to reveal the relationships between key elements of the
system and their modes of interaction;
2) To facilitate GGCM development through i) applications of global models to these problems, ii)
evaluation of their successes and deficiencies in capturing observed system behavior, and iii)
identification of missing physics and strategies for improving model fidelity; and
3) To advance empirical understanding by identifying and coordinating observations applicable to
the coupled solar wind-magnetosphere-ionosphere-thermosphere system, and to propose and coordinate empirical tests and validations of global models using key observations.
Attributes of Geospace System Study Projects
To achieve these objectives, the FG will need to marshal community resources and exploit synergies with other GEM Focus Groups. Thus candidate studies of the geospace system should:
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involve relational issues between system elements and processes, especially, though not exclusively, elements and processes that are being investigated by other GEM FGs;
be addressable with existing tools, methods, and data sets, but be open to new developments;
have sufficiently broad and compelling interest to enlist a critical mass effort;
entail both model applications and observations; and
rally community efforts and organization around “challenge” themes and studies.
Projects utilizing new or timely “assets” in global modeling and/or observational capabilities
(e.g., AMPERE, multifluid MHD, coupled SWMIT models) are especially desirable. Building on the
work of the two GGCM FGs ending in 2010 would provide continuity, e.g., topical study (I) described below may enlighten the interplay between reconnection and global current regulation (FG2)
and augment the scope of validation studies (FG1). A Geospace System Challenge preferably would
be undertaken jointly with new or recharged versions of the existing but soon-to-expire GGCM FGs.
Prospective Topical Studies
It became apparent at the 2009 Snowmass planning session that approaching geospace problems
from a system perspective will likely require some reorientation in community thinking in order to
pose the right system questions. Two problem areas emerged as prime candidates for the initial thrust
of the focus group: (I) regulation of reconnection and transpolar potentials, including stormtime saturation, and the global current-voltage relation, and (II) global resonance and quasi-periodic response
of the coupled magnetosphere-ionosphere to solar wind driving, including sawtooth phenomena. The
first of these problems, to first approximation, may be regarded as a slowly evolving or quasi-static
property of the system, whereas the second is fundamentally dynamic. As is typical of system problems, (I) and (II) are not necessarily independent. Both involve relatively unexplored effects of mixed
plasma circulation (ionospheric and solar wind origin) and its nonlinear interaction with the ionosphere-thermosphere, e.g., effects on particle precipitation, conductance and electrodynamics.
Problem (II) on global resonance overlaps one of the key problems of GEM FG13 on Modes of
Solar Wind – Magnetosphere Energy Transfer. Although this overlap to some extent diminishes the
impetus for this study project in the context of a geospace system FG, the mainly observational approach of focus group (13) might find considerable synergy with the envisioned modeling approach
that would emerge from a GGCM sponsored FG on geospace system.
It was decided at the Snowmass workshop to convene a second planning session at the Fall AGU
Gem Mini-Workshop to define and further refine the FG thrust, and in fact, the effort may be limited
to just one topical study at that time. A GS FG devoted to problems of global scope, e.g. prospective
topics (I) and (II) described above, may offer a conceptual global framework for all GEM FGs, and it
may serve to sharpen the questions addressed by them, thereby, promoting greater FG synergy.
Planning for a Geospace System Challenge
If selected, the GS FG will hold at least 2 breakout sessions at the 2010 GEM Workshop to refine
the science questions of the primary project. If a consensus for a second project, or a secondary project, emerges at the 2009 AGU GEM Mini-Workshop, its science questions would also be refined at
the 2010 Summer Workshop. Initial planning for a geospace system Challenge will be discussed at
the 2010 Summer Workshop. Candidate events and comparison studies that address the science
questions of the Challenge would be identified. Interim progress on assembling and coordinating
relevant data sets and model results, together with interpretations of observational and model results,
will be reviewed at the 2011 Summer Workshop, which would also provide an opportunity to draw
on CEDAR community expertise at the anticipated joint meeting of CEDAR and GEM. Results from
the challenge will be presented and discussed at 2012 Summer Workshop. Possible venues for publication of challenge results by participating scientists include a journal special issue or section.
FG Co-chairs: Bill Lotko, George Siscoe, Simon Shepherd, Bob Strangeway
FG Term: Nominally 3 years; proposal to extend to 5 years may be considered in Year 3