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Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS
175
While empirical models of electron precipitation have become increasingly sophisticated, knowledge of
the associated conductivity dynamics on spatial scales down to 1 km is still lacking. Even less is known
about conductivity enhancements due to ionospheric turbulence—effects that have been theoretically
predicted to be capable of doubling the total height-integrated conductivity during disturbed geomagnetic
conditions. A compelling question is thus, What are the spatial and temporal scales of ionospheric structure
and associated conductivity that determine energy deposition, plasma and neutral flows, and electrical
current flow in the ionosphere-thermosphere interaction?
Plasma of ionospheric origin mixes with solar wind plasma to populate the plasma sheet, ring current,
and plasmasphere. During episodic events such as storms and substorms, the presence of ionospheric
plasma in these regions can be a controlling factor in geospace dynamics. For example, dense, convecting plasmaspheric plumes are thought to modulate dayside magnetic reconnection upon contacting the
magnetopause. What are the processes that cause the plume structure to appear as storm-enhanced densities in the ionosphere? Ionospheric outflows emerging from the dayside cleft ion fountain and nightside
Alfvénic acceleration regions can dominate both the density and the pressure of the plasma sheet during
superstorms and the energy density of the ring current. Plasma in the inner magnetosphere is composed of
protons and He + and O + ions of ionospheric origin. The relative abundance of these ions influences the
plasma wave intensities that are responsible for the scattering and loss of radiation belt electrons. Recognition that ionospheric plasma is a critical agent in regulating the geospace system is accompanied by the
humbling reality that researchers do not know what controls the abundance or distribution of ionospheric
plasma in the magnetosphere. How does the flow of ionospheric plasma into the magnetosphere during
storms change as a result of IT plasma and neutral redistributions?
The AIMI panel concluded that an additional major goal of the coming decade is to understand how
the IT and magnetosphere interact to regulate their coupled response to solar wind forcing.
8.4.4 AIMI Science Goal 4. Plasma-Neutral Coupling in a Magnetic Field
How do neutrals and plasmas interact to produce multiscale structures in the AIM system?
An intriguing aspect of the IT system is the transfer of energy and momentum that occurs between the
plasma and neutral components of the system, and how electric and magnetic fields serve to accentuate and
sometimes moderate this interchange. The pathways through which ions and neutrals interact are of course
fundamental to space physics, as they occur all over our solar system. Addressing the compelling science
questions described within previous sections also presents many opportunities to employ the IT system as a
local laboratory to expand understanding of plasma-neutral coupling processes that have broad applicability
across the solar system. In particular, these interactions occur over local, regional, and global scales, and in
many cases cross-scale coupling exists. Some insight into the range of topics that can be addressed is provided in the following section, which begins with the low latitudes and then moves toward the polar regions.
The equatorial IT system represents a rich laboratory for investigation of plasma-neutral coupling in
the presence of a magnetic field. The unique features are the quasi-horizontal orientation of the B field,
the plasma instabilities that arise from this configuration, the ability of winds to generate electric fields
through the E- and F-region dynamo mechanisms, the change in plasma-neutral collision frequency with
height, the unimpeded ability of neutral winds to move plasma along field lines, and the relatively rapid
change in magnetic inclination with latitude. Combined with a variety of chemical processes, interactions
between the plasma and neutral gases in the above environment produce emergent behaviors in the neutral
and plasma densities, their bulk motions, and their temperatures. One example of emergent structures in
neutral density is provided in Figure 8.15.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS
175
While empirical models of electron precipitation have become increasingly sophisticated, knowledge of
the associated conductivity dynamics on spatial scales down to 1 km is still lacking. Even less is known
about conductivity enhancements due to ionospheric turbulence—effects that have been theoretically
predicted to be capable of doubling the total height-integrated conductivity during disturbed geomagnetic
conditions. A compelling question is thus, What are the spatial and temporal scales of ionospheric structure
and associated conductivity that determine energy deposition, plasma and neutral flows, and electrical
current flow in the ionosphere-thermosphere interaction?
Plasma of ionospheric origin mixes with solar wind plasma to populate the plasma sheet, ring current,
and plasmasphere. During episodic events such as storms and substorms, the presence of ionospheric
plasma in these regions can be a controlling factor in geospace dynamics. For example, dense, convecting plasmaspheric plumes are thought to modulate dayside magnetic reconnection upon contacting the
magnetopause. What are the processes that cause the plume structure to appear as storm-enhanced densities in the ionosphere? Ionospheric outflows emerging from the dayside cleft ion fountain and nightside
Alfvénic acceleration regions can dominate both the density and the pressure of the plasma sheet during
superstorms and the energy density of the ring current. Plasma in the inner magnetosphere is composed of
protons and He + and O + ions of ionospheric origin. The relative abundance of these ions influences the
plasma wave intensities that are responsible for the scattering and loss of radiation belt electrons. Recognition that ionospheric plasma is a critical agent in regulating the geospace system is accompanied by the
humbling reality that researchers do not know what controls the abundance or distribution of ionospheric
plasma in the magnetosphere. How does the flow of ionospheric plasma into the magnetosphere during
storms change as a result of IT plasma and neutral redistributions?
The AIMI panel concluded that an additional major goal of the coming decade is to understand how
the IT and magnetosphere interact to regulate their coupled response to solar wind forcing.
8.4.4 AIMI Science Goal 4. Plasma-Neutral Coupling in a Magnetic Field
How do neutrals and plasmas interact to produce multiscale structures in the AIM system?
An intriguing aspect of the IT system is the transfer of energy and momentum that occurs between the
plasma and neutral components of the system, and how electric and magnetic fields serve to accentuate and
sometimes moderate this interchange. The pathways through which ions and neutrals interact are of course
fundamental to space physics, as they occur all over our solar system. Addressing the compelling science
questions described within previous sections also presents many opportunities to employ the IT system as a
local laboratory to expand understanding of plasma-neutral coupling processes that have broad applicability
across the solar system. In particular, these interactions occur over local, regional, and global scales, and in
many cases cross-scale coupling exists. Some insight into the range of topics that can be addressed is provided in the following section, which begins with the low latitudes and then moves toward the polar regions.
The equatorial IT system represents a rich laboratory for investigation of plasma-neutral coupling in
the presence of a magnetic field. The unique features are the quasi-horizontal orientation of the B field,
the plasma instabilities that arise from this configuration, the ability of winds to generate electric fields
through the E- and F-region dynamo mechanisms, the change in plasma-neutral collision frequency with
height, the unimpeded ability of neutral winds to move plasma along field lines, and the relatively rapid
change in magnetic inclination with latitude. Combined with a variety of chemical processes, interactions
between the plasma and neutral gases in the above environment produce emergent behaviors in the neutral
and plasma densities, their bulk motions, and their temperatures. One example of emergent structures in
neutral density is provided in Figure 8.15.