Peak-Flux-Density Spectra of Large Radio Bursts and Proton Emission from Flares.
Abstract
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 Sp(200 MHz) < 100 sfu (18 percent). (2) If the current NOAA proton prediction threshold of J (> 10 MeV) > or = 10 protons/sq cm/sec/sr 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 and/or 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 protons/sq cm/sec/sr (1965-1979) originated in visible hemisphere flares with relatively weak (Sp < or = 300 sfu) and associated 200-MHz emission.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 19, 1985
- Accession Number
- ADA169134
Entities
People
- Edward W. Cliver
- L. C. Gentile
- L. F. Mcnamara
Organizations
- Air Force Research Laboratory