A Comparison of Solar X-Ray Flare Timescales and Peak Temperatures with Associated Coronal Mass Ejections

Abstract

Recent work has shown that plots of solar flare X-ray peak temperatures, Tm, versus log peak fluxes, Fp, show statistically significant separations of lower Tm flares with fast (Vcme ≥ 1000 km s−1) and wide (Wcme = 360°) strong coronal mass ejections (CMEs) from higher Tm flares with no CMEs or slow (Vcme < 1000 km s−1) or narrow (<360°) weak CMEs. We extend that statistical separation to CME kinetic energies, Ecme. Flares with long-duration timescales also have well-known associations with fast CMEs and solar energetic (E > 10 MeV) particle events. Using a data set of 585 ≥ M3.0 GOES X-ray flares, we ask whether longer flare timescales (rise times, TR; durations from onset to half-power decay, TD; decay times to half power, Td; and decay times to C2, TC2) also statistically discriminate among the three groups of CMEs for speeds, widths, and energies. All log–log plots of flare timescales versus Fp produce significant separations of the three groups of CMEs generally better than those of Tm versus log Fp. We use separations of CME distribution medians to sort the four flare timescales as effective discriminants among the three CME groups. Separations between the confined flares (no-CMEs) and weak CMEs are generally smaller than those between the weak CMEs and strong CMEs. A combination of Tm and TC2 provides optimum group separations, but Tm and log TD or log Td appears best for CME forecasting purposes.

A Database of Magnetic and Thermodynamic Properties of Confined and Eruptive Solar Flares

“…Note also, that while Hinterreiter et al (2018) While a large number of statistical studies have compared confined and eruptive flares' magnetic properties, few have analyzed the thermodynamic properties and energy partition of confined flares, and even fewer have compared those with eruptive events. Kahler & Ling (2022) analyzed GOES peak temperatures in hundreds of flares, of flare class M3.0 and above, and found, that for a given peak X-ray flux, confined flares have higher temperatures than eruptive flares, confirming earlier results of Kay et al's (2003) study of 69 flares. Cheng et al (2011) analyzed nine M-and X-class flares from the same ARs: six confined and three eruptive events.…”

Improved modelling of SEP event onset within the WSA–Enlil–SEPMOD framework

“…Next, we need to define the SEP injection times and temporal profiles, together with their fluxes and energy spectra. For the solar flare source, we use as the SEP injection time the peak time of the associated GOES X-ray emission, i.e., 06:38 UT (we note that Jebaraj et al, 2023, reported a radio Type III emission starting at 06:31 UT, which could be used as an alternative constraint), and employ an exponential decay time that is scaled with the flare class, under the assumption that this parameter is related to the duration of the X-ray emissione.g., Kahler & Ling (2022) showed that stronger flares tend to decay over longer time scales, possibly due to the longer duration of the related reconnection processes. For the coronal shock source, we use the onset time of the corresponding radio Type II emission (considered a signature of a formed CME-driven shock; e.g., Vršnak & Cliver, 2008;Magdalenić et al, 2010), i.e., 06:33 UT according to the analysis performed by Jebaraj et al (2023) employing ground-based observations.…”