Hot Flare Precursor Events in GOES 1-s Data: Filament Eruptions

Abstract

Solar flares exhibit precursor soft X-ray emission at high temperatures (the Hot Onset Precursor Event, here HOPE for short). This phenomenon is readily seen for events at or above the GOES C-class, but at present we do not know whether or not a “pure” filament-eruption event, such as one coming from the polar-crown filament zone, also exhibits this property. We study this question using both older and more modern GOES/XRS soft X-ray data. The currently operating GOES-R spacecraft (GOES-16 through GOES-19) have different sensor technology and also higher cadence than in the earlier satellites in the series, and so we devote an Appendix to describing these data from the point of view of a user interested in the detection of faint sources; most GOES/XRS users focus on flare observations, rather than the quiet Sun. Because the HOPE signatures appear at the very beginning of the development of a flare, they require study at the lowest flux levels. Our searches both with GOES-R and earlier data do not detect HOPE in purely filament-eruption events. At a representative HOPE temperature of 10 MK, the emission measure for any HOPE source must be less than about \(10^{46}\text{ cm}^{-3}\).