Solar and Heliospheric Physics
A survey of gradual solar energetic particle events
Article first published online: 11 MAY 2011
Copyright 2011 by the American Geophysical Union.
Journal of Geophysical Research: Space Physics (1978–2012)
Volume 116, Issue A5, May 2011
How to Cite
2011), A survey of gradual solar energetic particle events, J. Geophys. Res., 116, A05103, doi:10.1029/2010JA016133., and (
- Issue published online: 11 MAY 2011
- Article first published online: 11 MAY 2011
- Manuscript Accepted: 16 FEB 2011
- Manuscript Revised: 8 FEB 2011
- Manuscript Received: 21 SEP 2010
- solar energetic particles;
- space environment
 We develop a database of 110 gradual solar energetic particle (SEP) events, over the period 1967–2006, providing estimates of event onset, duration, fluence, and peak flux for protons of energy E > 60 MeV. The database is established mainly from the energetic proton flux data distributed in the OMNI 2 data set; however, we also utilize the McMurdo neutron monitor and the energetic proton flux from GOES missions. To aid the development of the gradual SEP database, we establish a method with which the homogeneity of the energetic proton flux record is improved. A comparison between other SEP databases and the database developed here is presented which discusses the different algorithms used to define an event. Furthermore, we investigate the variation of gradual SEP occurrence and fluence with solar cycle phase, sunspot number (SSN), and interplanetary magnetic field intensity (Bmag) over solar cycles 20–23. We find that the occurrence and fluence of SEP events vary with the solar cycle phase. Correspondingly, we find a positive correlation between SEP occurrence and solar activity as determined by SSN and Bmag, while the mean fluence in individual events decreases with the same measures of solar activity. Therefore, although the number of events decreases when solar activity is low, the events that do occur at such times have higher fluence. Thus, large events such as the “Carrington flare” may be more likely at lower levels of solar activity. These results are discussed in the context of other similar investigations.