Early evolution of an X-ray emitting solar active region |
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Authors: | C J Wolfson L W Acton J W Leibacher D T Roethig |
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Institution: | (1) Lockheed Palo Alto Research Laboratory, 3251 Hanover Street, 94304 Palo Alto, Calif., U.S.A. |
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Abstract: | The birth and early evolution of a solar active region has been investigated using X-ray observations from the Lockheed Mapping X-Ray Heliometer on board the OSO-8 spacecraft. X-ray emission is observed within three hours of the first detection of H plage. At that time, a plasma temperature of 4 × 106 K in a region having a density of the order of 1010 cm–3 is inferred. During the fifty hours following birth almost continuous flares or flare-like X-ray bursts are superimposed on a monotonically increasing base level of X-ray emission produced by plasma with a temperature of the order 3 × 106 K. If we assume that the X-rays result from heating due to dissipation of current systems or magnetic field reconnection, we conclude that flare-like X-ray emission soon after active region birth implies that the magnetic field probably emerges in a stressed or complex configuration. |
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