Plasma Physics of the Local Cosmos (2004) / Chapter Skim
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4 Plasma Interactions
4 Plasma Interactions
Pages 46-56
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From page 46... ...
They can be loosely classified into electromagnetic interactions, flow-object interactions, plasmaneutral interactions, and radiation-plasma interactions. Magnetic field lines connecting different plasma populations act as channels for the transport of plasmas, currents, electric fields, and waves between the two environments.
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From page 47... ...
Similarly, the ionospheric feedback electric fields map upward along the magnetic fields, affecting processes in the overlying regions. In the terrestrial environs, the development of a disturbance ring current drives strong electric fields in regions of low ionospheric conductivity These, in turn, affect both the planet's thermal plasma envelope and the further development of the energetic-plasma ring current.
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From page 48... ...
because the transfer of torque through the electromagnetic coupling of the planet to the magnetosphere is a close analogue to the shedding of angular momentum from a central body to a surrounding nebula by means of magnetic fields and field-aligned currents thought to occur in other astrophysical environments (see sidebar, "The Formation of Stellar and Planetary Svstems")
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From page 49... ...
The volume of space inside the magnetopause is dominated by the plasma and magnetic field associated with the planet, while outside the magnetopause the solar wind's plasma and magnetic field dominate. A magnetopause also exists at the Jovian moon Ganymede, whose intrinsic magnetic field was discovered in 1996; in this case, however, the ambient plasma is that of the jovian magnetosphere rather than the solar wind.
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From page 50... ...
The NASA Messenger mission, now under development, will take this important next step. The solar wind most certainly breaches, by magnetic reconnection, the magnetopauses of Jupiter and the other gas giants as well, but the extent of the contribution of the resulting energy transfer to magnetospheric dynamics at these planets is not known ~ In the case of nonmagnetized bodies, such as Venus, Mars, and comets, it is the planetary or cometary ionosphere, not a strong intrinsic magnetic field, that is the obstacle to the solar wind.
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From page 51... ...
(b) A Hubble Space Telescope image of the young stellar object HH 30 showing the bipolar outflows and the circumstellar dust disk (d A sketch of a protester viewed in the equatorial plane illustrating the interaction between the protostellar magnetic field and the surrounding accretion disk by means of which angular momentum is transferred outward.
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From page 52... ...
Because almost all of these studies were based on single-point measurements during transient magnetopause crossi ngs, they cou Id not determi ne the extent of mergi ng, its du ration, whether it was more rapid i n the subsolar region or elsewhere, or whether it was triggered by varying solar wind conditions. Recent imaging of the proton aurora by the NASA IMAGE satellite, which can identify protons accelerated by the reconnection electric field as they bombard the dayside upper atmosphere, has shown that magnetic reconnection occurs continuously at the magnetopause, changing location in response to variations in the direction of the solar-wind magnetic field.
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From page 53... ...
The detection of such energetic neutral atoms by a remote imager allows global images to be made of magnetospheric plasmas, which are invisible to standard astronomical observing techniques.
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From page 54... ...
SUMMARY Plasmas throughout the universe are strongly affected by the presence of magnetic fields and the currents that flow in response to any stresses placed on the magnetic field. Magnetized plasmas can
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From page 55... ...
Magnetic fields provide the connection between different plasma environments that acts to intro
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From page 56... ...
At sharp boundaries, like these, a host of microphysical plasma processes can occur, including magnetic reconnection, particle acceleration, wave excitation, and the generation of parallel electric fields. Phenomena associated with plasma-neutral interactions and radiation-plasma interactions mediate plasma coupling and can even represent controlling factors in the formation of plasma boundaries and the generation of stellar winds, It is fair to say that the wide range of plasma interactions that occur in solar system and astrophysical settings is appreciated but not very well understood.
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