The neupert effect: What can it tell us about the impulsive and gradual phases of eruptive flares?

Abstract

The Neupert Effect is the name given to the correlation observed in many flares between the impulsive time profile of the microwave and hard X-ray emissions and the time derivative of the soft X-ray profile. We have used data collected between 1980 and 1989 from the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission (SMM) and the soft X-ray detector on GOES to determine which events show this correlation and which do not. We have found that of 66 HXRBS events observed in 1980 with a peak rate of >1000 counts/s, 58 (80%) showed good correlation with peaks in the GOES time derivative plot corresponding to peaks in the HXR plots to within ±20 s. The more gradually varying X-ray events that are commonly referred to as Type C flares and that are often accompanied by eruptive flares, tend to show poorer correlation between the SXR time derivative and the HXR time profile. In several cases studied, the later, more gradually varying, peaks either did not register at all in the SXR time derivative plots or resulted in very broad peaks that, in one case on 1981 April 26, was delayed by 13 minutes.