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Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR WIND-MAGNETOSPHERE INTERACTIONS
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9.3.6 Comparative Magnetospheres
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 highaltitude radio wave measurements, and magnetospheric dynamics at Mercury, with events analogous to
substorms at Earth.
In situ data have yielded a better understanding of the dynamics, structure, and linkages of Jupiter’s
complex magnetosphere. 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. Observations far down the distant magnetotail revealed anti-sunward flows of plasma every
few days, as well as bursts of energetic particles accelerated in regions ~200 Jupiter radii down the tail
on the dusk flank. Earth-orbiting satellites imaged X-ray emissions from the auroral/polar regions resulting
from capture, acceleration, and subsequent atmospheric charge exchange of highly ionized heavy solar
wind ions.
There have been advances in theoretical understanding and observational tests of the impact of solar
wind dynamic pressure variations on Jovian auroral emissions, and significant progress in understanding
magnetospheric interactions with Jupiter’s satellites, especially Io. ENA imaging demonstrated that an
extensive torus of neutral gas from Europa has a significant impact on Jupiter’s magnetosphere.
Extensive measurements have been made of Saturn’s highly structured, interconnected, dynamical
system. Magnetospheric phenomena reveal two distinct, narrow band modulations near Saturn’s rotation
period (Figure 9.7a). Plumes of water gas and ice crystals emanate from rifts in the south polar region
of Enceladus (Figure 9.7b). Negatively charged hydrocarbon ions were discovered in Titan’s ionosphere
and may be important to the chemistry of Titan’s upper atmosphere. 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. Solar wind pressure variations strongly modulate the activity in
the outer magnetosphere, including Saturn kilometric radio emission and acceleration of energetic particles
in Saturn’s ring current (Figure 9.7c). Saturn’s rotating ring current results from both relatively symmetric
centrifugal acceleration of the sub-corotating cold plasma, and from more asymmetric hot plasma pressure.
9.4 SCIENCE GOALS FOR THE COMING DECADE
Today, researchers stand on the threshold of developing a comprehensive understanding of Earth’s
magnetosphere, its coupled behavior, and its impacts. This understanding will enable a capability to anticipate, predict, and ameliorate the effects of variable space weather. In this section, the SWMI panel takes
stock of where we are in the progression shown in Figure 9.2, and identifies the high-priority science goals
that must be pursued in the coming decade. 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 9.1). Table 9.1 summarizes the expected contributions of the SWMI science goals to the
decadal survey key science goals. Table 9.1 demonstrates that the discipline advances through a strategic
and thoughtful combination of discovery-class observations promoting new physical models and theories,
and the targeted observations needed to differentiate between competing physical theories.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR WIND-MAGNETOSPHERE INTERACTIONS
223
9.3.6 Comparative Magnetospheres
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 highaltitude radio wave measurements, and magnetospheric dynamics at Mercury, with events analogous to
substorms at Earth.
In situ data have yielded a better understanding of the dynamics, structure, and linkages of Jupiter’s
complex magnetosphere. 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. Observations far down the distant magnetotail revealed anti-sunward flows of plasma every
few days, as well as bursts of energetic particles accelerated in regions ~200 Jupiter radii down the tail
on the dusk flank. Earth-orbiting satellites imaged X-ray emissions from the auroral/polar regions resulting
from capture, acceleration, and subsequent atmospheric charge exchange of highly ionized heavy solar
wind ions.
There have been advances in theoretical understanding and observational tests of the impact of solar
wind dynamic pressure variations on Jovian auroral emissions, and significant progress in understanding
magnetospheric interactions with Jupiter’s satellites, especially Io. ENA imaging demonstrated that an
extensive torus of neutral gas from Europa has a significant impact on Jupiter’s magnetosphere.
Extensive measurements have been made of Saturn’s highly structured, interconnected, dynamical
system. Magnetospheric phenomena reveal two distinct, narrow band modulations near Saturn’s rotation
period (Figure 9.7a). Plumes of water gas and ice crystals emanate from rifts in the south polar region
of Enceladus (Figure 9.7b). Negatively charged hydrocarbon ions were discovered in Titan’s ionosphere
and may be important to the chemistry of Titan’s upper atmosphere. 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. Solar wind pressure variations strongly modulate the activity in
the outer magnetosphere, including Saturn kilometric radio emission and acceleration of energetic particles
in Saturn’s ring current (Figure 9.7c). Saturn’s rotating ring current results from both relatively symmetric
centrifugal acceleration of the sub-corotating cold plasma, and from more asymmetric hot plasma pressure.
9.4 SCIENCE GOALS FOR THE COMING DECADE
Today, researchers stand on the threshold of developing a comprehensive understanding of Earth’s
magnetosphere, its coupled behavior, and its impacts. This understanding will enable a capability to anticipate, predict, and ameliorate the effects of variable space weather. In this section, the SWMI panel takes
stock of where we are in the progression shown in Figure 9.2, and identifies the high-priority science goals
that must be pursued in the coming decade. 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 9.1). Table 9.1 summarizes the expected contributions of the SWMI science goals to the
decadal survey key science goals. Table 9.1 demonstrates that the discipline advances through a strategic
and thoughtful combination of discovery-class observations promoting new physical models and theories,
and the targeted observations needed to differentiate between competing physical theories.