The Inner Magnetosphere: Physics and Modeling

Department of Automatic Control and Systems Engineering
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While some of the specific processes that mediate this coupling with the solar wind were clarified in the past decade, major questions remain regarding the spatial extent over which they operate and the condi-. Coupling between the magnetosphere and the ionosphere represents a key linkage in geospace.

Researchers from the Northwest University and the South African Space Agency visit GFZ

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 magnetosphere-ionosphere 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.

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. 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. EUV images confirmed the predicted existence of plasmaspheric plumes see Figure 9. 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.

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. Wolf, M. Harel, R. Spiro, G. Voigt, P. Reiff, and C. Chen, Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, , Journal of Geophysical Research , In the upper panels, both simulations show a plasmoid release.

Wiltberger, W. Lotko, J. Lyon, P. Damiano, and V. Copyright American Geophysical Union. Reproduced by permission of American Geophysical Union. The past decade of research has also identified other ways in which the ionosphere-thermosphere and magnetosphere affect each other: plasmaspheric corotation lag was discovered and interpreted as a consequence of two-way coupling between the magnetosphere-ionosphere-thermosphere regions. Recent work demonstrates that the diffuse aurora is the main source of energy deposition into the ionosphere and that relativistic precipitation can have important effects on atmospheric chemistry, including ozone depletion.

Several serendipitous opportunities for imaging of both the northern and the southern aurorae simultaneously provided tests of auroral conjugacy and the dynamical processes thought to drive the aurorae. Plasmaspheric images from the IMAGE satellite in green, above revealed coherent plume structure and plasmapause distortions from time-varying electric fields. IMAGE ENA images orange, above show the partial ring current whose pressure distorts the solar wind forcing field that erodes the plasmasphere.

Goldstein, B. Sandel, M. Thomsen, M. Reiff, Simultaneous remote-sensing and in situ observations of plasmaspheric drainage plumes, Journal of Geophysical Research A, doi Coordinated studies employing imaging, remote sensing, modeling, and local measurements have demonstrated the critical importance of hot-cold plasma interactions.

Imaging revealed the dynamics of ring-current-plasmasphere overlap see Figure 9. Theoretical predictions that absence of cold dense plasma facilitates the acceleration of energetic electrons to relativistic energies were confirmed by observations. Studies showed that cold, dense plasma plays a pivotal role in defining the wave environment that controls energetic particle behavior, overturning the decades-old idea of a passive, quiescent plasmasphere in favor of an extremely dynamic, influential one.

Other aspects of this influence included partial quenching of dayside magnetopause reconnection by plasmaspheric plumes and the creation of ionospheric density enhancements that refract and scintillate GPS signals, producing ranging errors of tens of meters. It is clear that much progress has been made in understanding the system-level dynamics of the inner magnetosphere. In the coming decade, this knowledge must be refined and extended to encompass the entire magnetosphere-ionosphere-thermosphere system.

Over the past decade, researchers have made many advances toward understanding the structure, dynamics, and linkages in other planetary magnetospheres or systems with magnetospheric-like aspects. For the inner rocky planets, there are new results on atmospheric loss at Mars, through numerical modeling of the solar wind interaction with the atmosphere, identification of Venus lightning from high-altitude radio wave measurements, and magnetospheric dynamics at Mercury, with events analogous to substorms at Earth.

Flux-tube interchange processes transport Io-originating plasma outward through weak, centrifugally driven transport on the dayside. On the evening and nightside, where there is no confinement by the solar wind, this transport occurs through a more explosive centrifugal instability, leading to plasmoid loss. Plumes of water gas and ice crystals emanate from rifts in the south polar region of Enceladus Figure 9. Flux-tube interchange in the middle magnetosphere followed by plasmoid release in the magnetotail was revealed as the primary transport mechanisms for cold Enceladus plasma.

This understanding will enable a capability to anticipate, predict, and ameliorate the effects of variable space weather. After describing each science goal, the panel discusses how their accomplishment relates to the achievement of the four decadal survey key science goals identified in Chapter 1 see Box 9. Table 9. These injections yield bright auroral displays in the same region as the SKR radio emissions. Gurnett, J. Groene, A. Persoon, J. Menietti, S. Ye, W. Kurth, R. MacDowall, and A.

The Inner Magnetosphere: Physics and Modeling

Lecacheux, The reversal of the rotational modulation rates of the north and south components of Saturn kilometric radiation near equinox, Geophysical Research Letters L, doi Mitchell, S. Krimigis, C. Paranicas, P.

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Kurth, D. Clarke, J. Nichols, J. Observation from instruments on space platforms have provided researchers with a global view of the different plasma regions found in the magnetosphere and enabled a general understanding of their statistical structure and shape. During the past decade, space missions have delivered pathfinder global observations of some of the inner magnetospheric regions.

These observations, from the IMAGE and TWINS satellites, were revolutionary in their global perspective but were unfortunately characterized by relatively low spatial and temporal resolution. Also during the past decade, from THEMIS and from serendipitous alignments of Heliophysics Systems Observatory satellites, researchers acquired pathfinder one-dimensional simultaneous in situ observations of the outer magnetosphere, but still have no unambiguous observations of its two-dimensional or three-dimensional structure and evolution.

In sum, scientists do not know the instantaneous global and mesoscale structure of each of the various regions, nor how it evolves with time and solar wind driving. To understand how the system as a whole behaves in response to variations in the solar wind driver requires a better view of the simultaneous evolution of the various parts of the system, leading to the first SWMI science goal for the coming decade. Investigation into the global and mesoscale magnetospheric reaction to the solar wind is a challenging problem.


Bashkirov, D. Mass loading at the magnetopause through the plasmaspheric plume. Fuller-Rowell, and M. Recommended for implementation by NOAA. Page 67 Share Cite.

Much like meteorology, the plasmas of geospace interact in a highly complex, nonlinear way. Actions and reactions feed back on each other.


An integral element of such simulations is an electromagnetic field model. Recent studies of the inner magnetosphere have substantially. The Inner Magnetosphere: Physics and Modeling, Volume Editor(s). Tuija I. Pulkkinen; Nikolai A. Tsyganenko; Reiner H.W. Friedel.

For example, merging of the magnetic fields of the solar wind and Earth may impose up to a few hundreds of thousands of volts across the entire magnetosphere, activating an enormous, global convection cycle that strips away tons of near-Earth plasma and drags Earthward the plasma-loaded magnetic field lines of the distant nightside magnetosphere. In response, geospace creates its own cross-scale network of intricately interconnected electrical currents and fields whose effect is anything but uniform.

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Partial and temporary shielding occurs in some regions, while amplification of solar wind driving occurs in other regions, although exactly where and on what timescales are poorly known. Internal feedback profoundly modifies the whole system and can outlast by hours the cessation of solar wind forcing.

Predicting the behavior of this highly coupled, self-modifying system will require powerful models that include many physical processes operating over a wide range of spatial and temporal scales. The development and validation of such models will require a strong foundation in observations of global. TABLE 9. This foundation does not yet exist; to provide it will require instant-to-instant determination of the state of the system, at both global and mesoscales.

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Progress in the coming decade will thus require a comprehensive set of observations that connect global-scale changes to the mesoscale currents, flows, fields, heating, and particle acceleration that modify that global response. For example, continuous, global auroral imaging would enable researchers to follow rapid storm- and substorm-driven changes down to the scale of individual auroral arcs.