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Solar and Space Physics: A Science for a Technological Society
214
SOLAR AND SPACE PHYSICS: A SCIENCE FOR A TECHNOLOGICAL SOCIETY
is converted to plasma thermal energy, plasma bulk flow energy, and energized particles through a topological magnetic field reconfiguration. Charged particles in general conserve certain quantities of motion
called adiabatic invariants, which relate aspects of the particle motion to magnetic field parameters and can
lead to reversible energy changes. The term “wave-particle interactions” (WPIs) refers to the general and
broad process by which electromagnetic waves and charged particles exchange energy and momentum.
“Turbulence” describes the flow state of a fluid (including magnetized fluids) that is chaotic and stochastic. Turbulent media provide a rich opportunity for WPI. These same physical processes, determining the
structure and dynamics of Earth’s coupled solar wind-magnetosphere system, also govern other planetary
magnetospheres; by studying these fundamental processes in our own neighborhood, researchers glean
universally applicable knowledge.
9.2.1.3 Coupling to the Ionosphere and Solar Wind
The magnetosphere is physically bounded by the ionosphere and solar wind at its lower and upper
extents, respectively. Earth’s magnetosphere has no internal plasma sources, and so these boundary
regions are the two major sources of magnetospheric plasma. The solar wind is a large source of protons
and electrons into the magnetosphere, while the ionosphere contributes not only protons but also heavy
ion species like oxygen, helium, and nitrogen, and their accompanying electrons. Furthermore, the solar
wind and IMF, through magnetic reconnection and viscous interaction, drive convective flow throughout
the magnetosphere. The ionosphere, with its high conductance, regulates and modulates this convective
flow. In addition, the neutral gas of the upper atmosphere, known as the thermosphere, can also influence
magnetospheric flow through ion-neutral collisions.
9.2.1.4 Space Weather and the Magnetosphere
“Space weather” is the name given to the time-dependent conditions and changes that occur in
near-Earth space to the magnetospheric plasmas and fields. These include changes in the plasma density,
temperature, and spatial distributions, from the cold plasmasphere to the very energetic radiation belts.
In particular, space weather implies changes that have significant impact on technology and society. For
example, the variable ionosphere and plasmasphere alter geolocation signals from GPS and transmissions
from communication spacecraft; strong magnetospheric currents create geomagnetically induced currents
in power distribution systems; energetic particles cause radiation damage to microelectronics and spacefarers; and substorm-related satellite charging causes malfunctions and surface degradation.
9.2.1.5 Magnetospheric Questions That Flow from the Motivations
The motivations underlying the study of solar and space physics 3 apply directly to the study of Earth’s
magnetosphere and its interaction with the solar wind and upper atmosphere: Earth’s magnetosphere (and
those of other planets) is a fascinating, complex system, in which fundamental physical processes that
operate throughout the universe combine with unique conditions of plasma sources, sinks, and drivers
to create dynamic conditions that can affect humans and the technologies they depend on in space and
sometimes on the ground.
3 See the introduction to Part II of this decadal survey report.
Solar and Space Physics: A Science for a Technological Society
214
SOLAR AND SPACE PHYSICS: A SCIENCE FOR A TECHNOLOGICAL SOCIETY
is converted to plasma thermal energy, plasma bulk flow energy, and energized particles through a topological magnetic field reconfiguration. Charged particles in general conserve certain quantities of motion
called adiabatic invariants, which relate aspects of the particle motion to magnetic field parameters and can
lead to reversible energy changes. The term “wave-particle interactions” (WPIs) refers to the general and
broad process by which electromagnetic waves and charged particles exchange energy and momentum.
“Turbulence” describes the flow state of a fluid (including magnetized fluids) that is chaotic and stochastic. Turbulent media provide a rich opportunity for WPI. These same physical processes, determining the
structure and dynamics of Earth’s coupled solar wind-magnetosphere system, also govern other planetary
magnetospheres; by studying these fundamental processes in our own neighborhood, researchers glean
universally applicable knowledge.
9.2.1.3 Coupling to the Ionosphere and Solar Wind
The magnetosphere is physically bounded by the ionosphere and solar wind at its lower and upper
extents, respectively. Earth’s magnetosphere has no internal plasma sources, and so these boundary
regions are the two major sources of magnetospheric plasma. The solar wind is a large source of protons
and electrons into the magnetosphere, while the ionosphere contributes not only protons but also heavy
ion species like oxygen, helium, and nitrogen, and their accompanying electrons. Furthermore, the solar
wind and IMF, through magnetic reconnection and viscous interaction, drive convective flow throughout
the magnetosphere. The ionosphere, with its high conductance, regulates and modulates this convective
flow. In addition, the neutral gas of the upper atmosphere, known as the thermosphere, can also influence
magnetospheric flow through ion-neutral collisions.
9.2.1.4 Space Weather and the Magnetosphere
“Space weather” is the name given to the time-dependent conditions and changes that occur in
near-Earth space to the magnetospheric plasmas and fields. These include changes in the plasma density,
temperature, and spatial distributions, from the cold plasmasphere to the very energetic radiation belts.
In particular, space weather implies changes that have significant impact on technology and society. For
example, the variable ionosphere and plasmasphere alter geolocation signals from GPS and transmissions
from communication spacecraft; strong magnetospheric currents create geomagnetically induced currents
in power distribution systems; energetic particles cause radiation damage to microelectronics and spacefarers; and substorm-related satellite charging causes malfunctions and surface degradation.
9.2.1.5 Magnetospheric Questions That Flow from the Motivations
The motivations underlying the study of solar and space physics 3 apply directly to the study of Earth’s
magnetosphere and its interaction with the solar wind and upper atmosphere: Earth’s magnetosphere (and
those of other planets) is a fascinating, complex system, in which fundamental physical processes that
operate throughout the universe combine with unique conditions of plasma sources, sinks, and drivers
to create dynamic conditions that can affect humans and the technologies they depend on in space and
sometimes on the ground.
3 See the introduction to Part II of this decadal survey report.