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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
tions that control their relative importance (such as small-scale solar wind dynamic pressure variations
and how they drive ULF waves regionally and globally in the magnetosphere).
9.3.4.2 Magnetosphere-Ionosphere Coupling
Coupling between the magnetosphere and the ionosphere represents a key linkage in geospace. Over
the past decade, combined ground-based and space-based observations, theory, and modeling greatly
advanced understanding of this coupling as well as fostering new discoveries and new areas of investigation. Empirical studies of spacecraft data established correlations between solar wind and magnetosphereionosphere coupling parameters. For example, solar wind density and dynamic pressure increases lead to
enhanced ionospheric outflow. Empirical relationships quantified how electromagnetic energy flux into
the ionosphere led to consequent outflow rates. Supporting theory has shown that producing this outflow
requires a multistep process involving a combination of WPI and electromagnetic forcing. Researchers
have also realized the important consequences this outflowing ionospheric plasma has on the dynamic
evolution of the magnetosphere. Observations have shown how this outflow merges with plasmas of solar
wind origin in the plasma sheet, creating a multi-species plasma. Theorists have shown how differently
reconnection behaves in multispecies plasmas, which in turn substantially modifies its impacts on magnetospheric evolution and topology. Multifluid global-scale simulations have confirmed the major role
ionospheric outflow plays in the creation of periodic substorm or so-called sawtooth intervals (Figure 9.5).
Although the basic correlations and the fundamental building blocks have been established, the creation of
a complete theory of outflow and a detailed understanding of their magnetospheric consequences remains
a goal for the next decade.
9.3.5 System Dynamics
The past decade has witnessed a tremendous improvement in understanding how the inner magnetosphere responds to storm-time disturbances as a coherent system of coupled, mutually interacting plasmas.
Imaging and global simulations have played a central role by providing quantitative contextual information
that ties together single-point observations and gives much-needed global constraints for predictive models.
The modern picture that has resulted is one where multiple dynamic linkages are initiated by processes
with spatial scales ranging from highly localized to global.
Investigations uncovered key causal relationships between solar wind driving and inner-magnetospheric response. Changes in the north-south component of the IMF were shown to trigger the aurora,
ring current injections, and the commencement or cessation of plasmaspheric erosion. Numerical models
and global ENA images showed that the ring current is highly asymmetric during the main phase of storms
(Figure 9.6). EUV images confirmed the predicted existence of plasmaspheric plumes (see Figure 9.6) and
tracked their temporal evolution globally.
The directly driven response of the inner magnetosphere was found to engender electrodynamic
coupling among different regions. For example, storm-time ring-current-ionosphere coupling profoundly
distorts the inner magnetospheric field and feeds back to the ring current itself, skewing its peak toward
dawn (see Figure 9.6). Moreover, subauroral polarization streams (SAPS) were identified as duskside flow
channels, arising from ionospheric coupling, that maintain plumes long past the subsidence of solar wind
driving. These studies affirmed early theoretical concepts, 4 quantifying just how poorly shielded the innermost magnetosphere can be during rapid changes in magnetospheric convection.
4 See, for example, R.A. Wolf, M. Harel, R.W. Spiro, G.H. Voigt, P.H. Reiff, and C.-K. Chen, Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, 1977, Journal of Geophysical Research 87:5949, 1982.
Solar and Space Physics: A Science for a Technological Society
220
SOLAR AND SPACE PHYSICS: A SCIENCE FOR A TECHNOLOGICAL SOCIETY
tions that control their relative importance (such as small-scale solar wind dynamic pressure variations
and how they drive ULF waves regionally and globally in the magnetosphere).
9.3.4.2 Magnetosphere-Ionosphere Coupling
Coupling between the magnetosphere and the ionosphere represents a key linkage in geospace. Over
the past decade, combined ground-based and space-based observations, theory, and modeling greatly
advanced understanding of this coupling as well as fostering new discoveries and new areas of investigation. Empirical studies of spacecraft data established correlations between solar wind and magnetosphereionosphere coupling parameters. For example, solar wind density and dynamic pressure increases lead to
enhanced ionospheric outflow. Empirical relationships quantified how electromagnetic energy flux into
the ionosphere led to consequent outflow rates. Supporting theory has shown that producing this outflow
requires a multistep process involving a combination of WPI and electromagnetic forcing. Researchers
have also realized the important consequences this outflowing ionospheric plasma has on the dynamic
evolution of the magnetosphere. Observations have shown how this outflow merges with plasmas of solar
wind origin in the plasma sheet, creating a multi-species plasma. Theorists have shown how differently
reconnection behaves in multispecies plasmas, which in turn substantially modifies its impacts on magnetospheric evolution and topology. Multifluid global-scale simulations have confirmed the major role
ionospheric outflow plays in the creation of periodic substorm or so-called sawtooth intervals (Figure 9.5).
Although the basic correlations and the fundamental building blocks have been established, the creation of
a complete theory of outflow and a detailed understanding of their magnetospheric consequences remains
a goal for the next decade.
9.3.5 System Dynamics
The past decade has witnessed a tremendous improvement in understanding how the inner magnetosphere responds to storm-time disturbances as a coherent system of coupled, mutually interacting plasmas.
Imaging and global simulations have played a central role by providing quantitative contextual information
that ties together single-point observations and gives much-needed global constraints for predictive models.
The modern picture that has resulted is one where multiple dynamic linkages are initiated by processes
with spatial scales ranging from highly localized to global.
Investigations uncovered key causal relationships between solar wind driving and inner-magnetospheric response. Changes in the north-south component of the IMF were shown to trigger the aurora,
ring current injections, and the commencement or cessation of plasmaspheric erosion. Numerical models
and global ENA images showed that the ring current is highly asymmetric during the main phase of storms
(Figure 9.6). EUV images confirmed the predicted existence of plasmaspheric plumes (see Figure 9.6) and
tracked their temporal evolution globally.
The directly driven response of the inner magnetosphere was found to engender electrodynamic
coupling among different regions. For example, storm-time ring-current-ionosphere coupling profoundly
distorts the inner magnetospheric field and feeds back to the ring current itself, skewing its peak toward
dawn (see Figure 9.6). Moreover, subauroral polarization streams (SAPS) were identified as duskside flow
channels, arising from ionospheric coupling, that maintain plumes long past the subsidence of solar wind
driving. These studies affirmed early theoretical concepts, 4 quantifying just how poorly shielded the innermost magnetosphere can be during rapid changes in magnetospheric convection.
4 See, for example, R.A. Wolf, M. Harel, R.W. Spiro, G.H. Voigt, P.H. Reiff, and C.-K. Chen, Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, 1977, Journal of Geophysical Research 87:5949, 1982.