Solar Physics

, Volume 25, Issue 2, pp 418-424

First online:

The impulsive X-ray burst of October 10, 1970

  • S. R. KaneAffiliated withSpace Sciences Laboratory, University of California
  • , S. W. KahlerAffiliated withE. O. Hulburt Center, Naval Research Laboratory
  • , J. D. KurfessAffiliated withE. O. Hulburt Center, Naval Research Laboratory

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An impulsive burst of 100–400 keV solar X-rays associated with a small solar flare was observed on October 10, 1970 with a large area scintillator aboard a balloon floating at an altitude of 4.2 g cm-2 above the Earth's surface. The X-ray burst was also observed simultaneously in 10–80 keV range by the OGO-5 satellite and in 8–20 Å range by the SOLRAD-9 satellite. The impulsive X-ray emission reached its maximum at ∼ 1643 UT at which time the differential photon spectrum in 20–80 keV range was of the form 2.3 × 104 E -3.2 photons cm-2 s-1 keV-1 at 1 AU. The event is attributed to a Hα-subflare located approximately at S13, E88 on the solar disc. The spectral characteristics of this event are examined in the light of the earlier X-ray observations of small solar flares.