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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Born, R.: 1974,Solar Phys. 38, 127.
Bradt, H., Garmire, G., Oda, M., Spada, G., and Sreekantan, B. V.: 1968,Space Sci. Rev. 8, 471.
Bruzek, A.: 1967,Solar Phys. 2, 451.
Bruzek, A.: 1969,Solar Phys. 8, 29.
Bumba, V. and Howard, R.: 1964,Astrophys. J. 141, 1492.
Dodson, H. W. and Hedeman, E. R.: 1956,Monthly Notices Roy, Astron. Soc. 116, 427.
Frazier, E. N.: 1972,Solar Phys. 26, 130.
Glackin, D. L.: 1975,Solar Phys. 43, 317.
Golub, L., Krieger, A. S., Silk, J. K., Timothy, A. F., and Vaiana, G. S.: 1974,Astrophys. J. Letters 189, L93.
Harvey, K. L. and Martin, S. F.: 1973,Solar Phys. 32, 389.
Mosher, J. M: 1976, California Institute of Technology, Ph.D. Thesis.
Oda, M.: 1965,Appl. Optics 4, 143.
Solar-Geophysical Data: 1975, No. 374, Part I, U.S. Dept. of Commerce (Boulder, Colorado, U.S.A.).
Solar-Geophysical Data: 1976a, No. 378, Supplement, U.S. Dept. of Commerce (Boulder, Colorado, U.S.A.).
Solar-Geophysical Data: 1976b, No. 378, Part II, U.S. Dept. of Commerce (Boulder, Colorado, U.S.A.).
Tucker, W. H. and Koren, M.: 1971,Astrophys. J. 118, 283.
Vaiana, G. S., Krieger, A. S., Timothy, A. F., and Zombeck, M.: 1976,Astrophys. Space Sci. 39, 75.
Weart, S. R.: 1970,Astrophys. J. 162, 987.
Wolfson, C. J., Acton, L. W., and Gilbreth, C. W.: 1975,Mapping X-Ray Heliometer for OSO-8, Final Report, NASA-CR-144710.
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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