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 Hα 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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Wolfson, C.J., Acton, L.W., Leibacher, J.W. et al. Early evolution of an X-ray emitting solar active region. Sol Phys 55, 181–193 (1977). https://doi.org/10.1007/BF00150884
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DOI: https://doi.org/10.1007/BF00150884