ON THE BRIGHTNESS AND WAITING-TIME DISTRIBUTIONS OF A TYPE III RADIO STORM OBSERVED BY STEREO/WAVES

Type III solar radio storms, observed at frequencies below {approx}16 MHz by space-borne radio experiments, correspond to the quasi-continuous, bursty emission of electron beams onto open field lines above active regions. The mechanisms by which a storm can persist in some cases for more than a solar rotation whilst exhibiting considerable radio activity are poorly understood. To address this issue, the statistical properties of a type III storm observed by the STEREO/WAVES radio experiment are presented, examining both the brightness distribution and (for the first time) the waiting-time distribution (WTD). Single power-law behavior is observed in the number distribution as a function of brightness; the power-law index is {approx}2.1 and is largely independent of frequency. The WTD is found to be consistent with a piecewise-constant Poisson process. This indicates that during the storm individual type III bursts occur independently and suggests that the storm dynamics are consistent with avalanche-type behavior in the underlying active region.