High-energy protons associated with liftoff of a coronal mass ejection

Large solar energetic particle (SEP) events occur in association with fast coronal mass ejections (CMEs) and flares. We have studied in detail the rise phase of the SEP event of 1998 May 2 observed with the particle telescope ERNE aboard the Solar and Heliospheric Observatory (SOHO) spacecraft and ground-based neutron monitors. Using the ERNE data and numerical modeling of the SEP transport, we present improved evaluations of the solar release profile of deka-MeV protons. The SOHO EIT images are used to study the CME liftoff processes and possible sources of deka-MeV and hecto-MeV proton streams. In a first stage of the deka MeV proton production, which starts not later than 4 minutes after the radio flash and the Moreton wave start, particles get accelerated from a few MeV through 20 MeV in approximate to 15 minutes. Both ERNE and neutron monitor data are used to study the release of solar protons in the hecto-MeV range. The proton acceleration to above 400 MeV was completed not later than 15-20 minutes after the onset of the eruption. However, injection profiles of deka-MeV protons and hecto-MeV protons were different. Differences in the release scenarios, energy spectra, and composition of deka-MeV protons versus hecto-MeV protons suggest two different acceleration regions involved, perhaps situated on initially open lines and initially closed lines of the coronal magnetic field. The first SEP productions were followed by a prolonged period of proton reacceleration, which continued in the similar to 10-100 MeV range for many hours and during which a common energy spectrum was formed.