Speaker
Description
The PAMELA satellite experiment has recently provided accurate spectral measurements for 26 solar energetic particle (SEP) events occurring between December 2006 and September 2014. Observations cover the range between 80 MeV and 2 GeV, bridging the low-energy measurements from in situ space-based instruments and the high-energy data from the worldwide network of neutron monitors during ground level enhancements (GLEs). Reported results significantly improve the characterization of the most energetic SEP events. Measured spectra deviate from a simple power-law shape, exhibiting an exponential cutoff at high energies (several tens/hundreds MeV) that can be interpreted in terms of the limits of shock acceleration. No qualitative distinction between the spectra of GLE and non-GLE events was observed, suggesting that GLEs are not a separate class, but rather the most energetic subset of a continuous distribution of SEP events. We also took advantage of the superior energy resolution of the PAMELA instruments to calibrate the high-energy proton channels of the EPEAD and the HEPAD detectors on board GOES 13 and 15, improving the reliability of the spectroscopic observations of SEPs.
