Astron. Astrophys. 320, L13-L16 (1997)

2. Observational features

Let us briefly summarise the main observational discrepancies found from the SMM and Yohkoh observations and their comparison with microwave observations.

2.1. Hard X-ray emission

A comparison by MacKinnon et al. (1985) of hard X-ray fluxes for a few flare events, observed by the Hard X-ray Imaging Spectrometer (HXIS) in energy band of 16-30 keV and by the Hard X-ray Burst Spectrometer (HXRBS) in a range of 25-300 keV range aboard the Solar Maximum Mission, systematically showed the following discrepancies:

• 16-30 keV HXIS footpoint fluxes in a few flares were about of the simulteneous HXRBS flare fluxes, extrapolated by a power law into this lower energy range;
• footpoint spectra for some flares are much softer than the HXRBS; the difference between the spectral indices is about 1-2 units which cannot be considered as the observational errors.

2.2. Microwave emission

• the energy distributions of electrons, producing a burst emission, were found to have a power law with a spectral index equal to 3.2, whereas the simultaneous hard X-ray observations gave a spectral index equal to 5;
• the total number of electrons (), producing microwave emission, is systematically lower by three orders of magnitude, than the total number of electrons () responsible for hard X-ray emission.

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998
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