Copyright © National Academy of Sciences. All rights reserved.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR WIND-MAGNETOSPHERE INTERACTIONS
227
response. This foundation does not yet exist; to provide it will require instant-to-instant determination of
the state of the system, at both global and mesoscales. Progress in the coming decade will thus require
a comprehensive set of observations that connect global-scale changes to the mesoscale currents, flows,
fields, heating, and particle acceleration that modify that global response. For example, continuous, global
auroral imaging would enable researchers to follow rapid storm- and substorm-driven changes down to
the scale of individual auroral arcs. Nonstop global plasma imaging could resolve the minute-to-minute
development of cross-scale, cross-region plasma energization and transport, erosion of the plasmasphere,
and development of internal structure. Uninterrupted radar measurements could follow ionospheric flows
and fields. Additional observations that would help relate global and mesoscale magnetospheric evolution
to solar wind driving would include continuous global distributions of field-aligned currents linking the
magnetosphere and ionosphere, detailed measurements of ionospheric ion outflow, and observations of
plasma-sheet and cusp plasma conditions and composition. The key to significant progress in this area is
to have these global and mesoscale observations available simultaneously.
While touching on decadal survey key science goals 1, 3, and 4, this thrust is aimed squarely at decadal
survey key science goal 2. This problem is one of the most challenging scientific problems remaining in
the realm of geospace, and one of the most important to solve toward the goal of providing the capability
to predict the effects of solar variability on the environment and on society. The geospace community has
moved ever closer to that goal over the past several decades; with the proper focus and implementation,
the coming decade can more fully realize the benefits to society of this endeavor.
Linkages
Researchers know that key regions are coupled and understand the general nature of the linkages.
Some involve transfer of charged particles from one region to another, while others involve electrodynamic
connections, and still others involve plasma instabilities and waves. Pathfinder observations have been
collected of ionospheric plasma outflows, auroral and radiation-belt precipitation into the ionosphere, solarwind plasma entry into the magnetosphere, and signatures of nonlinear feedback in the electrodynamic
coupling between the solar wind, magnetosphere, and ionosphere. However, still lacking is a quantitative
understanding of the linkages, including their critically important nonlinear, feedback aspects. In addition,
researchers do not understand the dependence of these linkages on the conditions within the regions nor
on the variability of the driver. Furthermore, there is compelling evidence that preconditioning, system
memory, and prior history of the solar wind driver confound the coupling. Since history in the solar wind
often does not repeat itself (except for recurring patterns such as stream interaction regions), this presents
a challenge for general understanding.
To understand how the magnetospheric system as a whole behaves in response to variations in the
solar wind driver, researchers need a quantitative understanding of these linkages, including what and how
conditions control them and what the feedback processes are and how they work. These needs motivate
the two SWMI science goals discussed next.
9.4.1.2 SWMI Science Goal 2. Identify the Controlling Factors That Determine the Dominant Sources
of Magnetospheric Plasma
Digging Deeper
There are two primary sources for magnetospheric plasma: the solar wind and the ionosphere. Solar
wind plasma enters predominantly via reconnection between interplanetary and magnetospheric magnetic
fields; diffusive entry constitutes a smaller contribution. Ionospheric plasma enters by flowing outward into
the magnetosphere, as the result of being heated and/or directly accelerated through auroral processes
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR WIND-MAGNETOSPHERE INTERACTIONS
227
response. This foundation does not yet exist; to provide it will require instant-to-instant determination of
the state of the system, at both global and mesoscales. Progress in the coming decade will thus require
a comprehensive set of observations that connect global-scale changes to the mesoscale currents, flows,
fields, heating, and particle acceleration that modify that global response. For example, continuous, global
auroral imaging would enable researchers to follow rapid storm- and substorm-driven changes down to
the scale of individual auroral arcs. Nonstop global plasma imaging could resolve the minute-to-minute
development of cross-scale, cross-region plasma energization and transport, erosion of the plasmasphere,
and development of internal structure. Uninterrupted radar measurements could follow ionospheric flows
and fields. Additional observations that would help relate global and mesoscale magnetospheric evolution
to solar wind driving would include continuous global distributions of field-aligned currents linking the
magnetosphere and ionosphere, detailed measurements of ionospheric ion outflow, and observations of
plasma-sheet and cusp plasma conditions and composition. The key to significant progress in this area is
to have these global and mesoscale observations available simultaneously.
While touching on decadal survey key science goals 1, 3, and 4, this thrust is aimed squarely at decadal
survey key science goal 2. This problem is one of the most challenging scientific problems remaining in
the realm of geospace, and one of the most important to solve toward the goal of providing the capability
to predict the effects of solar variability on the environment and on society. The geospace community has
moved ever closer to that goal over the past several decades; with the proper focus and implementation,
the coming decade can more fully realize the benefits to society of this endeavor.
Linkages
Researchers know that key regions are coupled and understand the general nature of the linkages.
Some involve transfer of charged particles from one region to another, while others involve electrodynamic
connections, and still others involve plasma instabilities and waves. Pathfinder observations have been
collected of ionospheric plasma outflows, auroral and radiation-belt precipitation into the ionosphere, solarwind plasma entry into the magnetosphere, and signatures of nonlinear feedback in the electrodynamic
coupling between the solar wind, magnetosphere, and ionosphere. However, still lacking is a quantitative
understanding of the linkages, including their critically important nonlinear, feedback aspects. In addition,
researchers do not understand the dependence of these linkages on the conditions within the regions nor
on the variability of the driver. Furthermore, there is compelling evidence that preconditioning, system
memory, and prior history of the solar wind driver confound the coupling. Since history in the solar wind
often does not repeat itself (except for recurring patterns such as stream interaction regions), this presents
a challenge for general understanding.
To understand how the magnetospheric system as a whole behaves in response to variations in the
solar wind driver, researchers need a quantitative understanding of these linkages, including what and how
conditions control them and what the feedback processes are and how they work. These needs motivate
the two SWMI science goals discussed next.
9.4.1.2 SWMI Science Goal 2. Identify the Controlling Factors That Determine the Dominant Sources
of Magnetospheric Plasma
Digging Deeper
There are two primary sources for magnetospheric plasma: the solar wind and the ionosphere. Solar
wind plasma enters predominantly via reconnection between interplanetary and magnetospheric magnetic
fields; diffusive entry constitutes a smaller contribution. Ionospheric plasma enters by flowing outward into
the magnetosphere, as the result of being heated and/or directly accelerated through auroral processes