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The Dynamics of Solar Coronal Magnetic Fields

Published online by Cambridge University Press:  19 July 2016

B. C. Low
B. C. Low*
Affiliation:
High Altitude Observatory National Center for Atmospheric Research Boulder, Colorado, USA

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The solar corona is a hot (106K) highly ionized plasma structured by its magnetic field into open regions where the solar wind escapes and closed regions where relatively dense plasma is trapped in near static equilibrium. Observed in Thomson-scattered light at times of solar eclipse or by artificial occultation using a coronagraph, these closed regions show up conspicuously as helmet-shaped bright structures. The large scale corona evolves in time in response to the solar dynamo that continually injects new magnetic flux into the corona with the eventual reversal of the global magnetic polarity at the end of each half cycle of eleven years. It was discovered in the 1970s using spaceborne coronagraphs that in addition to its long-term evolution, the corona also undergoes dynamical reconfiguration with ejection of mass of the order of 1015g into interplanetary space (MacQueen 1980). These time dependent phenomena take place once every few days at solar activity minimum and as often three times a day at solar activity maximum. Since the 1970s, coronal mass ejections have been studied at the High Altitude Observatory by the use of the coronagraph on the NASA Solar Maximum Mission Satellite and groundbased instruments at Hawaii. This brief review presents three points of interest in the coronal mass ejection as a hydromagnetic process, emphasizing the unique opportunity offered by the corona to study hydromagnetic phenomena by direct observation (Hundhausen 1987, Kahler 1987, Low 1986).

Type
1. A Survey of Magnetic Phenomena near the Solar Photosphere, in the Corona, and in Stellar Winds
Information
Symposium - International Astronomical Union , Volume 140: Galactic and Intergalactic Magnetic Fields , 1990 , pp. 13 - 15
Copyright
Copyright © Kluwer 1990 

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