Characterizing Solar Energetic Particle Event Profiles with Two-Parameter Fits
Abstract
The intensity-time profiles of solar energetic (E > 10 MeV) particle (SEP) events observed at 1 AU reflect a number of physical processes involving solar injection and interplanetary transport. In addition to energy spectral and composition studies, SEP intensity-time profiles are the basis for diagnostic time scales needed for describing and modeling the acceleration and transport of SEPs. We briefly review commonly used time scales and point out the absence of holistic descriptions of the SEP profiles. We define the requirements for such a description and select a modified Weibull function from among three candidates as one which provides a reasonable two-parameter fit for most observed SEP events. Besides the peak intensity Ip, each event energy range can be described by shape and duration parameters alpha and beta. Fits are applied to the profiles of fourteen recent large SEP events observed in three integral energy ranges by the GOES spacecraft. The fits are generally robust, with < 1% uncertainties in the parameters, but they can be very dependent on the choices of fit end times. We show the fit parameters as functions of energy range and solar source longitude. The fit parameters can be used not only as targets for modeling efforts but also in space weather applications.
- Publication:
-
AAS/Solar Physics Division Abstracts #47
- Pub Date:
- May 2016
- Bibcode:
- 2016SPD....4710202K