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Flares on the Sun : Selected Results from Hinotori

1983; Springer Nature (Netherlands); Linguagem: Inglês

10.1007/978-94-009-7157-8_35

2214-7985

Katsuo Tanaka,

Stellar, planetary, and galactic studies

The X-ray observations of solar flares by Japanese astronomy satellite Hinotori (ASTRO-A) are reviewed. Detailed results from the X-ray telescope and the soft X-ray spectrometers are given. The hard X-ray images in the 17–40 keV range show a wide variety of source structures. Examples of compact single source, stationary coronal source, and double sources are presented. High resolution spectra in the range 1.7–2.0A indicate strong turbulence and blue-shifted components in the beginning of flares. From the FeXXV and FeXXVI spectra two kinds of thermal plasma are shown to appear. The cooler component of Te=15–20xl06 K, which increases in the impulsive phase of the hard X-ray burst, is suggested to be produced by the dissipation of the electron beams. The hotter component of Te=30–50xl06 K and Ne=1011 – 1012 cm-3 increases towards the flare maximum. This component is also responsible for emitting 17–40keV continuum, and emitted from a very compact source. The results are discussed in comparison with flare loop models. It is shown that evolutionary changes in the loop density realize various source structures in the hard X-ray under the unitary electron beam hypothesis.