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
233
of turbulence: mixing (Is there evidence for mixing?), energy cascade (How do the turbulent fluctuations
interact to transfer energy?), and heating (What is the plasma heating rate and is the heating important?). It
is not known whether turbulence affects transport and entropy conservation, and it is not known whether
turbulence leads to reconnection events in the magnetotail or alters large-scale dynamics there.
The magnetosheath flow around the magnetosphere is also turbulent, and the same three questions
about the nature of the turbulence apply: dynamics, driving, and dissipation. There is an additional question for the turbulent magnetosheath flow: Is eddy viscosity important for the coupling of the flow to the
magnetosphere?
The turbulence inside and around the magnetosphere has potential impact on the dynamics of the
magnetosphere and its response to solar input (decadal survey key science goal 2). Turbulence in both the
magnetosheath and the magnetotail provides unique opportunities to discover and characterize fundamental processes that occur here and throughout the universe (decadal survey key science goal 4).
Wave-particle interactions are ubiquitous in the magnetosphere. Waves clearly play an important role
in both energization and loss of ring current and radiation belt particles, but it is necessary to establish
which WPIs are most effective. In the inner magnetosphere, current knowledge is limited to the statistical distributions of waves, and so moving forward will require a better characterization of the spatialtemporal structure of the waves and how they are produced. Researchers must understand how wave
production is modulated by macroscale plasma properties and how high-frequency waves are modulated
by lower-frequency, large-scale fluctuations. They must determine how particle populations are modified
by wave-particle interactions and understand how that feeds back on wave generation. Finally, a better
understanding is needed of the importance and detailed physics of nonlinear interactions with the largeamplitude waves that are observed.
The instabilities that occur in our solar system are expected to also occur throughout the universe,
affecting particle populations in many different environments. Advancing understanding of the waves and
their interaction with particles at Earth thus enables decadal survey key science goal 4. Moreover, determining the roles played by waves in energization and loss of magnetospheric particles will be necessary
for advancing understanding to the point of predictive capability for the near-Earth environment, enabling
decadal survey key science goals 1 and 2.
9.4.3 System Dynamics
Serendipitous multipoint measurements by the Heliophysics Systems Observatory plus the global
perspective from the IMAGE and TWINS missions have provided a greater appreciation for the degree to
which the various regions and processes interact. Still, researchers have only a rudimentary understanding
of how all the pieces fit together to determine the global magnetospheric response to solar wind variability.
In particular, we lack a full understanding of how nonlinear feedback between the ionosphere and magnetosphere regulates magnetospheric dynamics. This motivates SWMI science goal 7.
9.4.3.1 SWMI Science Goal 7. Determine How Magnetosphere-Ionosphere-Thermosphere Coupling
Controls System-Level Dynamics
Digging Deeper
In previous studies of the magnetosphere-ionosphere-thermosphere system, signs of nonlinear feedback were observed, and that the coupling affects the global transport of plasma is known. This nonlinear
coupling involves both electrodynamic communication and mass exchange between these regions, but
what controls the nonlinearities is not known. At a fundamental level, the mapping between a location
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR WIND-MAGNETOSPHERE INTERACTIONS
233
of turbulence: mixing (Is there evidence for mixing?), energy cascade (How do the turbulent fluctuations
interact to transfer energy?), and heating (What is the plasma heating rate and is the heating important?). It
is not known whether turbulence affects transport and entropy conservation, and it is not known whether
turbulence leads to reconnection events in the magnetotail or alters large-scale dynamics there.
The magnetosheath flow around the magnetosphere is also turbulent, and the same three questions
about the nature of the turbulence apply: dynamics, driving, and dissipation. There is an additional question for the turbulent magnetosheath flow: Is eddy viscosity important for the coupling of the flow to the
magnetosphere?
The turbulence inside and around the magnetosphere has potential impact on the dynamics of the
magnetosphere and its response to solar input (decadal survey key science goal 2). Turbulence in both the
magnetosheath and the magnetotail provides unique opportunities to discover and characterize fundamental processes that occur here and throughout the universe (decadal survey key science goal 4).
Wave-particle interactions are ubiquitous in the magnetosphere. Waves clearly play an important role
in both energization and loss of ring current and radiation belt particles, but it is necessary to establish
which WPIs are most effective. In the inner magnetosphere, current knowledge is limited to the statistical distributions of waves, and so moving forward will require a better characterization of the spatialtemporal structure of the waves and how they are produced. Researchers must understand how wave
production is modulated by macroscale plasma properties and how high-frequency waves are modulated
by lower-frequency, large-scale fluctuations. They must determine how particle populations are modified
by wave-particle interactions and understand how that feeds back on wave generation. Finally, a better
understanding is needed of the importance and detailed physics of nonlinear interactions with the largeamplitude waves that are observed.
The instabilities that occur in our solar system are expected to also occur throughout the universe,
affecting particle populations in many different environments. Advancing understanding of the waves and
their interaction with particles at Earth thus enables decadal survey key science goal 4. Moreover, determining the roles played by waves in energization and loss of magnetospheric particles will be necessary
for advancing understanding to the point of predictive capability for the near-Earth environment, enabling
decadal survey key science goals 1 and 2.
9.4.3 System Dynamics
Serendipitous multipoint measurements by the Heliophysics Systems Observatory plus the global
perspective from the IMAGE and TWINS missions have provided a greater appreciation for the degree to
which the various regions and processes interact. Still, researchers have only a rudimentary understanding
of how all the pieces fit together to determine the global magnetospheric response to solar wind variability.
In particular, we lack a full understanding of how nonlinear feedback between the ionosphere and magnetosphere regulates magnetospheric dynamics. This motivates SWMI science goal 7.
9.4.3.1 SWMI Science Goal 7. Determine How Magnetosphere-Ionosphere-Thermosphere Coupling
Controls System-Level Dynamics
Digging Deeper
In previous studies of the magnetosphere-ionosphere-thermosphere system, signs of nonlinear feedback were observed, and that the coupling affects the global transport of plasma is known. This nonlinear
coupling involves both electrodynamic communication and mass exchange between these regions, but
what controls the nonlinearities is not known. At a fundamental level, the mapping between a location