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Time Variations of Solar X-ray Bright Points

Published online by Cambridge University Press:  14 August 2015

L. Golub ,
A. S. Krieger ,
J. K. Silk ,
A. F. Timothy  and
G. S. Vaiana
L. Golub
Affiliation:
American Science & Engineering, Cambridge, Mass., U.S.A.
A. S. Krieger
Affiliation:
American Science & Engineering, Cambridge, Mass., U.S.A.
J. K. Silk
Affiliation:
American Science & Engineering, Cambridge, Mass., U.S.A.
A. F. Timothy
Affiliation:
American Science & Engineering, Cambridge, Mass., U.S.A.
G. S. Vaiana
Affiliation:
Center for Astrophysics, Cambridge, Mass., U.S.A.

Summary

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An example of the overall view of the X-ray corona (nominal filter passband 2–32 Å and 44–54 Å) showing a coronal hole, filament activity, bright points and the large scale-scale loop structures, is shown in Figure 1. This is one of the 32000 X-ray images obtained with the AS & E X-ray telescope on Skylab. A comprehensive review describing the characteristics of the various features and their implications regarding the high velocity solar streams, evolution of magnetic fields in active regions, and sources of soft X-ray emission has been given by Vaiana et al. (1975). In the present summary we will only be concerned with the bright points. Studies of solar X-ray bright points, show that these features represent a distinct class of solar activity. Bright points appear first as a diffuse cloud of soft X-ray emission typically growing to 30″ in diameter, with growth rates of ∼1 km s−1. Several hours after the point first becomes visible a bright compact core forms, growing to 10″. The lifetime distribution of bright points follows a Poisson distribution with a mean of eight hours (see references). The points are distributed uniformly over the entire solar surface, with approximately 500 on the Sun at any time. Their occurrrence appears to be independent of major active regions, except for a visibility factor near high loop structures or a possible decrease in number in active region latitudes.

Type
Part 1: General Solar Activity, Coronal Holes and Bright Points
Information
Symposium - International Astronomical Union , Volume 68: Solar X, Gamma, and EUV Radiation , 1975 , pp. 23 - 24
Copyright
Copyright © Reidel 1975 

References

Golub, L., Krieger, A. S., Silk, J. K., Timothy, A. F., and Vaiana, G. S.: 1974, Astrophys. J. Letters 189, L93.CrossRefGoogle Scholar
Harvey, K. L. and Martin, S. F.: 1973, Solar Phys. 32, 389.CrossRefGoogle Scholar
Krieger, A. S., Viana, G. S., and Van Speybroeck, L. P.: 1971, in Howard, R. (ed.), ‘Solar Magnetic Fields’, IAU Symp. 43, 397.Google Scholar
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Vaiana, G. S., Krieger, A. S., and Timothy, A. F.: 1973, Solar Phys. 32, 81.CrossRefGoogle Scholar
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