A statistical study of 90–MeV proton events during the rising phase of solar cycle 23 observed with SOHO/ERNE

This study aims to comprehend solar and interplanetary (IP) phenomena generating solar energetic particle (SEP) events with proton energies exceeding 90MeV and identify the locations and commencement times of proton acceleration during such events. Forty energetic proton events, with intensities surpassing 10^−3 cm ^−2 sr^ −1 MeV^ −1 at ∼ 94MeV, were meticulously selected from observations by the Energetic and Relativistic Nuclei and Electrons (ERNE) instrument onboard the Solar and Heliospheric Observatory (SOHO) during solar cycle 23. Using the fixed path length method (1.2AU) and velocity dispersion analysis (VDA), we estimated particle injection times, cross-validating results with the height of radio type II/IV burst emission and comparing them with flare and coronal mass ejection (CME) characteristics. All analyzed proton events were associated with CMEs, 27 with on-the-disk soft X-ray flares, and two void of any flare signatures. Radio type II/IV burst emission association was significant, and for non-associated events, one lacked radio emission while the other exhibited metric continuum and tilted type III burst lane emission. Protons were predominantly injected when CME leading edges were below 5R , reaching peak intensities above 10R preceding the potential passage of IP shocks. In events where the CME front surpassed the estimated type II burst location, we propose a connection between type II bursts, CME interaction processes, and shocks at the CME flanks.