The SOLAR-A spacecraft has spectroscopic capabilities in a wide energy band from soft X-rays to gamma-rays. The Wide Band Spectrometer (WBS), consisting of three kinds of spectrometers, soft X-ray spectrometer (SXS), hard X-ray spectrometer (HXS) and gamma-ray spectrometer (GRS), is installed on SOLAR-A to investigate plasma heating, high-energy particle acceleration, and interaction processes. SXS has two proportional counters and each counter provides 128-channel pulse height data in the 2-30 keV range every 2 s and 2-channel pulse count data every 0.25 s. HXS has a NaI scintillation detector and provides 32-channel pulse height data in the 20-400 keV range every 1 s and 2-channel pulse count data every 0.125 s. GRS has two identical BGO scintillation detectors and each detector provides 128-channel pulse height data in the 0.2-10 MeV range every 4 s and 4-channel pulse count data (0.2-0.7, 0.7-4, 4-7, and 7-10 MeV) every 0.25-0.5 s. In addition, each of the BGO scintillation detectors provides 16-channel pulse height data in the 8-100 MeV range every 4 s and 2-channel pulse count data (8-30 and 30-100 MeV) every 0.5 s. The SXS observations enable one to study the thermal evolution of flare plasma by obtaining time series of electron temperatures and emission measures of hot plasma; the HXS observations enable one to study the electron acceleration and heating mechanisms by obtaining time series of the electron spectrum; and the GRS observations enable one to study the high-energy electron and ion acceleration and interaction processes by obtaining time series of electron and ion spectra.

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Two balloons each carrying a payload consisting of three sets of NaI(T1) scintillation counters have been launched from Thompson, Manitoba, Canada, in April 1975, to search precipitating mechanisms of auroral particles through observations of the bremsstrahlung X-rays in conjugation with the geo-stationary statellite ATS-6. Two omnidirectional counters, one of which had the modulation collimator, were used together with the directional counter inclined from the zenith. On the basis of the spin-modulated data obtained during the appearance of two distinct auroral X-ray bursts, two-dimensional source models, arc-and disc-shaped, are proposed for the auroral X-ray illuminating region. Also shown is an example of the eastward drift of another auroral X-ray source. Some of problems related to the analyses of data, i.e., background fluxes due to cosmic rays, and the response functions of the detectors are discussed.

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