Forecast of solar proton flux profiles for well‐connected events

Abstract

We have developed a forecast model of solar proton flux profiles (> 10 MeV channel) for well-connected events. Among 136 solar proton events (SPEs) from 1986 to 2006, we select 49 well-connected ones that are all associated with single X-ray flares stronger than M1 class and start to increase within 4 h after their X-ray peak times. These events show rapid increments in proton flux. By comparing several empirical functions, we select a modified Weibull curve function to approximate a SPE flux profile. The parameters (peak flux, rise time, and decay time) of this function are determined by the relationship between X-ray flare parameters (peak flux, impulsive time, and emission measure) and SPE parameters. For 49 well-connected SPEs, the linear correlation coefficient between the predicted and the observed proton peak fluxes is 0.65 with the RMS error of 0.55 log 10 (pfu). In addition, we determine another forecast model based on flare and coronal mass ejection (CME) parameters using 22 SPEs. The used CME parameters are linear speed and angular width. As a result, we find that the linear correlation coefficient between the predicted and the observed proton peak fluxes is 0.83 with the RMS error of 0.35 log 10 (pfu). From the relationship between error of model and CME acceleration, we find that CME acceleration is an important factor for predicting proton flux profiles.

Forecasting Solar Energetic Particle (SEP) events with Flare X-ray peak ratios

“…The current trend in forecasting SEP events is to combine multiple solar eruptive observable inputs to develop increasingly accurate forecasts. These forecasts generally have taken properties of X-ray flares in combination with those of associated CMEs (Huang et al, 2012;Ji et al, 2014;Swalwell et al, 2017) or of radio bursts (Alberti et al, 2017). However, in all these studies only the 0.1-0.8 nm X-ray flare flux is used, while the 0.05-0.4 nm flux, despite its ready availability along with the GOES 0.1-0.8 nm flux, is ignored.…”

“…For current SEP forecasting models, only the 0.1-0.8 nm band has been utilized, with two exceptions to our knowledge. Ji et al (2014) used three GOES X-ray flare parameters, one of which was the flare emission measure, to construct a model to forecast the peak E > 10 MeV SEP-event intensities. Although they give no information on the source of the emission measure, a timevarying quantity, we assume it is derived from the ratio of the GOES 0.05-0.4 nm and 0.1-0.8 nm bands.…”

The Reported Durations of GOES Soft X‐Ray Flares in Different Solar Cycles

“…However, we have to be careful to distinguish those works that used the flare listings for only the correct peak X‐ray fluxes (e.g., Belov, ; Garcia, ) and not for times or fluences. Further, many authors used the pre‐1998 GOES XRS flux time profiles to determine independently their own flare times and fluences (e.g., Balch, ; Cane et al, ; Ji et al, ; Laurenza et al, ; Papaioannou et al, ; Trottet et al, ) or used those independent lists for further analyses (e.g., Kahler & Ling, ; Kahler et al, ). Finally, there have been many SEP event studies based on X‐ray flare reports together with coronal mass ejections (CMEs) from the Solar and Heliospheric Observatory's Large Angle and Spectroscopic Coronagraph catalog listings (e.g., Belov, ; Dierckxsens et al, ; Miteva et al, ; Park & Moon, ).…”

Fast injection of the relativistic electrons into the inner zone and the formation of the split‐zone structure during the Bastille Day storm in July 2000

“…Figure 4 (left) shows that high-energy protons are followed later by lower energy protons. This is the hallmark of an energetic, well-connected event [Reames, 1999; Journal of Geophysical Research: Space Physics 10.1002/2015JA022072 Ji et al, 2014]. The high-energy protons arrive first but do not trigger the proton channels because their electronic energy loss (dE/dx) is too small to trigger.…”