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
229
by solar wind-magnetosphere interaction, further accelerate the ions with a component that drives them
outward along geomagnetic field lines. While the basic components controlling outflow are understood,
quantitative relationships between solar wind conditions and energy inputs, and between energy inputs
and resulting outflow, have not been established.
For example, researchers do not know how the amount of electromagnetic energy entering the ionosphere depends on the specific solar wind conditions. In recent years, the spatial and temporal distribution
of Poynting flux has received much attention. Driven by both dayside and nightside reconnection and
associated fast flows, the associated Poynting flux drives not only convection but also ionospheric outflows
and is now recognized as an important term in the ionospheric energy balance. The spatial and temporal
variability of precipitating electron flux is also not well established, and the altitude and locations where
these inputs deposit their energy are not yet clear. In addition, the atmospheric and ionospheric responses
are poorly quantified.
Current understanding is limited by poor knowledge of the wave environment generated by the energy
input; which waves accelerate and heat the plasma; and the impact of any feedback and saturation processes. These issues must be resolved in order to develop a predictive understanding of the ionospheric
response to solar wind forcing; their resolution also has strong links to decadal survey key science goals
2 and 4. Identifying the factors that control solar wind and ionospheric contributions to magnetospheric
populations is fundamental to determining the dynamics of the magnetosphere, ionosphere, and atmosphere, their coupling, and the response to solar wind variability.
SWMI science goal 3 is the panel’s second critical goal related to linkages between different regions
and populations.
9.4.1.3 SWMI Science Goal 3. Understand How Plasmas Interact Within the Magnetosphere and at Its
Boundaries
Digging Deeper
The interaction between the solar wind and magnetosphere results in energy and mass transfer across
the magnetic fields at their interface. One key to understanding magnetospheric processes lies at the magnetopause. Past observations by single spacecraft or closely spaced spacecraft established that processes such
as magnetic reconnection, diffusive entry, and Kelvin-Helmholtz instability operate at the magnetopause
and lead to solar wind entry across the magnetopause These processes, especially reconnection, and their
consequences depend on the IMF orientation, solar wind convection electric field, and solar wind pressure. Even within the magnetotail itself, significant ion densities are known to exist in the lobes, yet only a
portion eventually enters into the plasma sheet; the remaining fraction escapes down the tail through the
distant side of the near-Earth or mid-tail reconnection. This is another critical aspect of solar wind entry:
solar wind plasma has not been at least quasi-trapped into the magnetosphere until it crossed the nightside
reconnection separatrix. Due to the lack of large-scale observations of the outer magnetosphere, significant
questions remain concerning the global consequences of these processes and their relative importance
under different solar wind conditions.
Another crucial interface within the magnetosphere is that between the magnetotail and the inner
magnetosphere. In response to solar-wind energy input, magnetotail processes produce narrow flow bursts,
transporting plasmas and magnetic flux from the distant magnetotail to the inner magnetosphere. While
the past decade revealed the size of individual flow channels and their temporal evolution, much remains
unknown about their global occurrence properties. This limits the ability to understand the transport of
magnetotail particles into the inner magnetosphere, where they interact with other particle populations.
The current inability to observe the three-dimensional, time-dependent magnetotail limits the ability to
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR WIND-MAGNETOSPHERE INTERACTIONS
229
by solar wind-magnetosphere interaction, further accelerate the ions with a component that drives them
outward along geomagnetic field lines. While the basic components controlling outflow are understood,
quantitative relationships between solar wind conditions and energy inputs, and between energy inputs
and resulting outflow, have not been established.
For example, researchers do not know how the amount of electromagnetic energy entering the ionosphere depends on the specific solar wind conditions. In recent years, the spatial and temporal distribution
of Poynting flux has received much attention. Driven by both dayside and nightside reconnection and
associated fast flows, the associated Poynting flux drives not only convection but also ionospheric outflows
and is now recognized as an important term in the ionospheric energy balance. The spatial and temporal
variability of precipitating electron flux is also not well established, and the altitude and locations where
these inputs deposit their energy are not yet clear. In addition, the atmospheric and ionospheric responses
are poorly quantified.
Current understanding is limited by poor knowledge of the wave environment generated by the energy
input; which waves accelerate and heat the plasma; and the impact of any feedback and saturation processes. These issues must be resolved in order to develop a predictive understanding of the ionospheric
response to solar wind forcing; their resolution also has strong links to decadal survey key science goals
2 and 4. Identifying the factors that control solar wind and ionospheric contributions to magnetospheric
populations is fundamental to determining the dynamics of the magnetosphere, ionosphere, and atmosphere, their coupling, and the response to solar wind variability.
SWMI science goal 3 is the panel’s second critical goal related to linkages between different regions
and populations.
9.4.1.3 SWMI Science Goal 3. Understand How Plasmas Interact Within the Magnetosphere and at Its
Boundaries
Digging Deeper
The interaction between the solar wind and magnetosphere results in energy and mass transfer across
the magnetic fields at their interface. One key to understanding magnetospheric processes lies at the magnetopause. Past observations by single spacecraft or closely spaced spacecraft established that processes such
as magnetic reconnection, diffusive entry, and Kelvin-Helmholtz instability operate at the magnetopause
and lead to solar wind entry across the magnetopause These processes, especially reconnection, and their
consequences depend on the IMF orientation, solar wind convection electric field, and solar wind pressure. Even within the magnetotail itself, significant ion densities are known to exist in the lobes, yet only a
portion eventually enters into the plasma sheet; the remaining fraction escapes down the tail through the
distant side of the near-Earth or mid-tail reconnection. This is another critical aspect of solar wind entry:
solar wind plasma has not been at least quasi-trapped into the magnetosphere until it crossed the nightside
reconnection separatrix. Due to the lack of large-scale observations of the outer magnetosphere, significant
questions remain concerning the global consequences of these processes and their relative importance
under different solar wind conditions.
Another crucial interface within the magnetosphere is that between the magnetotail and the inner
magnetosphere. In response to solar-wind energy input, magnetotail processes produce narrow flow bursts,
transporting plasmas and magnetic flux from the distant magnetotail to the inner magnetosphere. While
the past decade revealed the size of individual flow channels and their temporal evolution, much remains
unknown about their global occurrence properties. This limits the ability to understand the transport of
magnetotail particles into the inner magnetosphere, where they interact with other particle populations.
The current inability to observe the three-dimensional, time-dependent magnetotail limits the ability to