Forty Years of Solar Microwave Burst Flux Measurements

We report results from an investigation of 40 years of solar radio burst data, from 1960-1999, compiled by the National Geophysical Data Center at NOAA, Boulder, CO. This data set consists of more than a half-million entries corresponding to several hundred thousand bursts measured at many frequencies from approximately 150 MHz to 35 GHz, and covering more than three 11-year solar activity cycles. We discuss the ways in which limitations and biases in the data set are identified and, where possible, corrected. We present the corrected number distributions for bursts greater than 20 SFU (solar flux units, 1 SFU = 10 sup {-22} W/m sup 2 Hz), and power law fits to them, as a function of frequency, time, and phase of the solar cycle. We compare these distributions and their variation with similar measures in other wavelengths, and discuss the implications for coronal heating and other aspects of flare physics.