Peak-Flux-Density Spectra of Large 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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From this study of the peak flux density spectra of nearly 200 large sp or 2 GHz or 800 solar flux units microwave bursts and their associated proton and sweep frequency emissions, we have found the following 1 There appear to be two basic peak-flux-density spectral types a U-shaped, with two maxima or 800 sfu in the range of 200 MHz to or 19 GHz 59 percent of all events and b cutoff, with a spectral maximum or 800 sfu at f or 2 GHz and Sp200 MHz 100 sfu 18 percent. 2 If the current NOAA proton prediction threshold of J 10 MeV or 10 protonssq cmsecsr had been in effect during the period covered by our data base 1965-1979, the U-burst yes or no proton event forecast tool would have had a false alarm rate of approx. 50 percent and would have failed to provide a warning for approx. 50 percent of the significant prompt proton flares attributable to disk flares during this period. 3 The associations of flare-bursts of different peak flux density spectral type with Type II andor Type IV bursts and with 10-MeV proton events of any peak intensity are given. 4 In 74 percent of the microwave bursts with u-shaped spectra, the 200 MHz emission peak occurred during a Type III event. For 49 percent of the U-bursts, a Type II was in progress during, or began or 0.5 min after, the peak 200-MHz emission. 5 Several 8 of 46 of the proton events with J 10 MeV or 10 protonssq cmsecsr 1965-1979 originated in visible hemisphere flares with relatively weak Sp or 300 sfu and associated 200-MHz emission.