Proton Enhancements and Their Relation to the X-Ray Flares During the Three Last Solar Cycles

Abstract

Energetic proton measurements obtained from the GOES and IMP-8 satellites as well as from ground-based neutron monitors are compared with the GOES soft X-ray measurements of the associated solar flares for the period 1975-2003. The present study investigates a broad range of phenomenology relating proton events to flares (with some references to related interplanetary disturbances), including correlations of occurrence, intensities, durations and timing of both the particle event and the flare as well as the role of the heliographic location of the designated active region. 1144 proton events of >10 MeV energy were selected from this 28-year period. Owing primarily to the low particle flux threshold employed more than half of this number was found to be reliably connected with an X-ray flare. The statistical analysis indicates that the probability and magnitude of the near-Earth proton enhancement depends critically on the flare's importance and its heliolongitude. In this study all flares of X-ray importance >X5 and located in the most propitious heliolongitude range, 15 • W to 75 • W, were succeeded by a detectable proton enhancement. It was also found that the heliolongitude frequently determines the character of the proton event time profile. In addition to intensity, duration and timing, proton events were found to be related to the other flare properties such as lower temperatures and longer loop lengths.

Solar flares, coronal mass ejections and solar energetic particle event characteristics

“…Indeed, when comparing the number of events within each bin the relevant numbers are 48 over 13 which lead to a factor of 3.96. These results are in line with results reported, for instance, in Belov et al (2005), Laurenza et al (2009), Park et al (2010 and Dierckxsens et al (2015), among others. Figure 6A presents the distribution of the non-SEP-related CME events and that of the SEP-related CMEs (Fig.…”

“…There is a large spread of SEP events from the E30°-W30°region. As expected (Belov et al 2005), the western hemisphere includes a second peak at W50°-W60°, where the SEP occurrence is prevalent, which is not seen in the eastern hemisphere. The disparity is maintained until the limb.…”

“…5D). First of all, one can see that there is a zone between -40 and 40°in latitude that holds all SFs, together with the SEP-related ones -which is typical for source regions (Belov et al 2005). Since SFs are mainly coming from active regions, Figure 5C essentially outlines the active-region belt of the Sun (Maunder 1904).…”

“…The dependence of the expected probability for the SEP occurrence on the heliolongitude of the parent SF has been extensively reported and documented (Belov et al 2005;Laurenza et al 2009;Cane et al 2010;Dierckxsens et al 2015;Trottet et al 2015). That means that a small percentage of SEP-related flares is expected to appear in association with C-class SFs.…”

“…A key element for the decoding of the characteristics of SEP events is the establishment of empirical and/or semiempirical statistical relations between their characteristics and the observed properties of the parent solar events (Gopalswamy et al 2003Garcia 2004aGarcia , 2004bBelov et al 2005;Trottet et al 2015). Although such relations are not deterministic and thus do not lead to first-principle physical laws, they should be considered as deductive approaches.…”