LEVELS OF SOLAR SOFT X-RAY BACK GROUND AND ENHANCED EMISSIONS WITH IMPORTANCE X

During the periods of January, 1986-December, 1992, 130 solar soft X-ray events with importance≥ X1 at 1- 8Å wavelengths reported and the corresponding background emissions are analyzed. And it is found that more than 90% of X-ray events with importance ≥X1 appeared at the level≥C1 of background emission. Such a statistical rule may be interpreted as the result that the nonthermal electrons accelerated by solar flare to heat chromosphere plasma.