Peak-Flux-Density Spectra of Large Solar Radio Bursts and Proton Emission from Flares.
Environmental research papers, Jul 81-Jul 85,
AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
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We have reexamined the relationship between U-shaped peak-flux-density microwave spectra and solar proton events for approx 200 large Sp or 2GHz or 800 solar flux uits sfu microwave burst 1965 - 1979. The radio spectra fell into two basic classes a U-shaped with two maxima or 800 sfu in the range from 200 MHz to or 10 GHz 59 percent of all events, and b cutoff spectra with a maximum or 800 sfu at f or 2 GHz and Sp 200 MHz 100 sfu 18 percent. Nine percent of the events had intermediate spectra with a maximum or 800 sfu at f or 2 GHz and 100 sfu or Sp 200 MHz 800 sfu. We were unable to classify 15 percent of the events because of incomplete data. The associations of the three classes of spectra with Type II andor Type IV meter wavelenght bursts and 10 MeV proton events of any size or 0.01 pr per sq cm per sec per sr are as follows U-shaped Type IIIV 90 percent of large microwave bursts with U-shaped spectra are associated with Type IIIV events, protons 77 percent intermediate Type IIIV 78 percent, protons 73 percent and cutoff Type IIIV 22 percent, protons 33 percent. These statistics affirm various lines of evidence linking coronal shock waves and interplanetary proton events. They also suggest that the meter wavelength branch of the U-shaped spectrum may be attributable to second phase vs flash phase accelerated electrons.