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Solar and Space Physics: A Science for a Technological Society
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SOLAR AND SPACE PHYSICS: A SCIENCE FOR A TECHNOLOGICAL SOCIETY
understand transport processes at the inner edge of the magnetotail and their response to time-varying
solar wind.
Exquisite regions of overlap between the cold plasmasphere plasma and the hotter populations of the
plasma sheet, ring current, and radiation belt define conditions in the inner magnetosphere. In the regions
of overlap, these disparate plasmas interact with one another, largely through intermediary electromagnetic waves, leading to important dynamical consequences: enhanced particle precipitation, large-scale
instabilities, particle energization, and enhanced transport. Because systems-level measurements have
been insufficient, a quantitative understanding is lacking of how these particle interactions are controlled
by external driving parameters and how important they are under various conditions. To predict how the
system behaves in response to variations in the solar wind requires quantitative understanding of the nature
and significance of the fundamental processes driven by these overlapping, disparate plasma populations.
Progress in the coming decade requires a program incorporating coordinated multipoint and/or remotesensing global measurements, along with global numerical simulations and local theory.
This goal directly addresses decadal survey key science goal 2, with significant contributions to understanding fundamental processes (key science goal 4) and enabling prediction of magnetospheric variability
(key science goal 1).
9.4.2 Universal Processes
Scientists have identified a range of important physical processes operating in different magnetospheric
regions, and understand what their consequences are, locally and in some cases globally. This understanding stems from pathfinder observations of some of these processes and of the solar wind conditions under
which they appear to operate. In addition, scientists eagerly anticipate information about reconnection
and particle energization from the Magnetospheric Multiscale (MMS) and Radiation Belt Storm Probes
(RBSP) missions. However, even with these additions to the Heliophysics Systems Observatory, adequate
insight into the nature and consequences of important processes like turbulence and wave-particle interactions will still be lacking. Moreover, scientists do not know the relative effectiveness of these various
processes under different conditions, nor how they turn on and off. To understand how the system as a
whole behaves in response to variations in the solar wind driver, improved knowledge is needed of how
various conditions control these processes, including their own nonlinear feedback. Thus, for the coming
decade, including the goals for MMS and RBSP, there are three SWMI science goals (4-6 below) relating
to fundamental physical processes in solar wind-magnetosphere interactions.
9.4.2.1 SWMI Science Goal 4. Establish How Energetic Particles Are Accelerated, Transported, and Lost
Digging Deeper
The flux of energetic particles in Earth’s radiation belts exhibits extreme variability, with timescales
ranging from a few minutes to days. However, current understanding of the underlying physical mechanisms
for this variability remains incomplete. The observed variability, particularly for energetic electrons in the
outer radiation belt, has been associated with pronounced changes in either the acceleration or the loss
processes, both of which are enhanced during geomagnetic activity associated with solar disturbances.
The current difficulty in modeling radiation belt dynamics is due to the inability to adequately quantify
the variability of the dominant source and loss processes under different levels of geomagnetic activity.
In the essentially collisionless magnetosphere, energetic particles tend to behave adiabatically in the
absence of perturbing influences, that is, preserving certain characteristic invariant properties of their
gyro, bounce, and drift motions when the magnetic fields they move within evolve slowly relative to the
time scales of these motions. Changes in the adiabatic trapped particle motion are primarily due to interac-
Solar and Space Physics: A Science for a Technological Society
230
SOLAR AND SPACE PHYSICS: A SCIENCE FOR A TECHNOLOGICAL SOCIETY
understand transport processes at the inner edge of the magnetotail and their response to time-varying
solar wind.
Exquisite regions of overlap between the cold plasmasphere plasma and the hotter populations of the
plasma sheet, ring current, and radiation belt define conditions in the inner magnetosphere. In the regions
of overlap, these disparate plasmas interact with one another, largely through intermediary electromagnetic waves, leading to important dynamical consequences: enhanced particle precipitation, large-scale
instabilities, particle energization, and enhanced transport. Because systems-level measurements have
been insufficient, a quantitative understanding is lacking of how these particle interactions are controlled
by external driving parameters and how important they are under various conditions. To predict how the
system behaves in response to variations in the solar wind requires quantitative understanding of the nature
and significance of the fundamental processes driven by these overlapping, disparate plasma populations.
Progress in the coming decade requires a program incorporating coordinated multipoint and/or remotesensing global measurements, along with global numerical simulations and local theory.
This goal directly addresses decadal survey key science goal 2, with significant contributions to understanding fundamental processes (key science goal 4) and enabling prediction of magnetospheric variability
(key science goal 1).
9.4.2 Universal Processes
Scientists have identified a range of important physical processes operating in different magnetospheric
regions, and understand what their consequences are, locally and in some cases globally. This understanding stems from pathfinder observations of some of these processes and of the solar wind conditions under
which they appear to operate. In addition, scientists eagerly anticipate information about reconnection
and particle energization from the Magnetospheric Multiscale (MMS) and Radiation Belt Storm Probes
(RBSP) missions. However, even with these additions to the Heliophysics Systems Observatory, adequate
insight into the nature and consequences of important processes like turbulence and wave-particle interactions will still be lacking. Moreover, scientists do not know the relative effectiveness of these various
processes under different conditions, nor how they turn on and off. To understand how the system as a
whole behaves in response to variations in the solar wind driver, improved knowledge is needed of how
various conditions control these processes, including their own nonlinear feedback. Thus, for the coming
decade, including the goals for MMS and RBSP, there are three SWMI science goals (4-6 below) relating
to fundamental physical processes in solar wind-magnetosphere interactions.
9.4.2.1 SWMI Science Goal 4. Establish How Energetic Particles Are Accelerated, Transported, and Lost
Digging Deeper
The flux of energetic particles in Earth’s radiation belts exhibits extreme variability, with timescales
ranging from a few minutes to days. However, current understanding of the underlying physical mechanisms
for this variability remains incomplete. The observed variability, particularly for energetic electrons in the
outer radiation belt, has been associated with pronounced changes in either the acceleration or the loss
processes, both of which are enhanced during geomagnetic activity associated with solar disturbances.
The current difficulty in modeling radiation belt dynamics is due to the inability to adequately quantify
the variability of the dominant source and loss processes under different levels of geomagnetic activity.
In the essentially collisionless magnetosphere, energetic particles tend to behave adiabatically in the
absence of perturbing influences, that is, preserving certain characteristic invariant properties of their
gyro, bounce, and drift motions when the magnetic fields they move within evolve slowly relative to the
time scales of these motions. Changes in the adiabatic trapped particle motion are primarily due to interac-