Solar flare X-ray burst on September 28,1961
The bright chromospheric flare of September 28, 1961, emitted a burst of X rays observed by high-altitude balloon-borne detectors. The burst had a small precursor, a very rapid rise, and a three-component decay. The main part of the burst is therefore interpreted as being made up of three separate pulses. The x- ray burst shows two remarkable associations with the flare's radio noise emission: (1) microwave bursts at the highest radio frequencies coincide precisely in time with the precursor and the main peak; and (2) groups of type III bursts occur at or near the time of discontinuities in the decay of the X-ray burst and thus are associated with the leading edges of the three energeti c electron pulses whose bremsstrahlung constitutes the observed X-ray flux. The appearance of both type III radiation originating in the corona at about 10/sup 5/ km and bremsstrahlung X rays that cannot reasonably be produced above roughly 5000-km height in the chromosphere gives strong evidence that energetic electrons undergo large-scale motions in the solar atmosphere during chromospheric flares. For this particular flare a filamentary structure appears to be rooted near the sunspot where the flare occurs. Although no direct observations exist on this point, the filament no doubt extends up into the lower corona perhaps to heights of 10/sup 5/ km. This leads to the possibility that the electrons are contained and guided by this structure. The photon energy spectrum is found to be nearly constant in form, whereas the X-ray intensity varies greatly. This fact makes it extremely unlikely that the bremsstrahlung originates from a thermal distribution of high-tempernture electrons. A detailed analysis of the spectral time variation shows that the solar electrons must spend most of their time above the 15,000km level. (auth)
- Research Organization:
- Univ. of California, Berkeley
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-005091
- OSTI ID:
- 4740525
- Journal Information:
- Journal of Geophysical Research, Vol. 67, Issue 11; Other Information: Orig. Receipt Date: 31-DEC-63; ISSN 0148-0227
- Publisher:
- American Geophysical Union
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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