Hostname: page-component-7bb8b95d7b-495rp Total loading time: 0 Render date: 2024-09-18T22:06:52.990Z Has data issue: false hasContentIssue false

X-ray emission from the solar wind

Published online by Cambridge University Press:  14 August 2015

E. Boldt
Affiliation:
NASA, Goddard Space Flight Center, Greenbelt, Md., U.S.A.
A. Klimas
Affiliation:
Aeronautical Research Associates of Princeton, Inc., Princeton, N.J., U.S.A.
G. Sandri
Affiliation:
Aeronautical Research Associates of Princeton, Inc., Princeton, N.J., U.S.A.

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Recent developments have made it possible to detect cosmic X-rays with energies as low as several hundred eV. Several measurements of the diffuse X-radiation in this range have been reported (Baxter et al., 1969; Bowyer et al., 1968; Henry et al., 1968). In this note we investigate the possibility that these observers have detected X-radiation emitted by the solar wind. We conclude that they probably have not. However, we also find that bremsstrahlung may be detectable from a region of the sky near the sun. If this measurement is possible, it would represent an important method for determining some characteristics of the solar wind away from the ecliptic plane of the solar system. Even though the mean free path for electron collisions is large compared with the astronomical unit, the collision frequency, electron density, and energy released per encounter are sufficient to yield detectable soft X-radiation for lines of sight close to the sun. We have estimated the expected X-ray intensity in the vicinity of the earth on the basis of two models of the solar wind flow pattern; in the first, the flow is radial in all directions away from the sun, and in the second, the flow is confined to a disc of uniform thickness near the ecliptic. In both cases, we neglect temperature gradients for the electrons and compute the total flux received from interplanetary plasma along the line of sight. Most of the received intensity comes from the segment of the line of sight which is nearest the sun. The results are insensitive with respect to the position of the boundary of the solar cavity. Accordingly, we neglect the boundary and consider an infinitely large solar cavity.

Type
Research Article
Copyright
Copyright © Reidel 1970 

References

Baxter, A. J., Wilson, B. G., and Green, D. W.: 1969, Astrophys. J. (Letters) 155, L145.CrossRefGoogle Scholar
Bowyer, C. S., Field, G. B., and Mark, J. E.: 1968, Nature 217, 32.Google Scholar
Greene, J.: 1959, Astrophys. J. 130, 693.Google Scholar
Henry, R. C., Fritz, G., Meekins, J. F., Friedman, H., and Byram, E. T.: 1968, Astrophys. J. (Letters) 153, L11.Google Scholar
Parker, E. N.: 1963, Interplanetary Dynamical Processes, Interscience, New York and London, pp. 5172.Google Scholar
Tucker, W. H. and Gould, R. J.: 1966, Astrophys. J. 144, 244.Google Scholar