High-energy particles were recorded by the near-Earth spacecraft and ground-based neutron monitors ( NMs ) on 2012 May 17 .
This event was the first Ground Level Enhancement ( GLE ) of the solar cycle 24 .
In present study , we try to identify the acceleration source ( s ) of solar energetic particles ( SEPs ) by combining in-situ particle measurements from WIND /3DP , GOES 13 , and solar cosmic rays ( SCRs ) registered by several NMs , as well as the remote-sensing solar observations from SDO /AIA , SOHO /LASCO , and RHESSI .
We derive the interplanetary magnetic field ( IMF ) path length ( 1.25 \pm 0.05 AU ) and solar particle release ( SPR ) time ( 01:29 \pm 00:01 UT ) of the first arriving electrons by using their velocity dispersion and taking into account the contamination effects .
It is found that the electron impulsive injection phase , indicated by the dramatic change of spectral index , is consistent with the flare non-thermal emission and type III radio bursts .
Based on the potential field source surface ( PFSS ) concept , a modeling of the open-field lines rooted in the active region ( AR ) has been performed to provide escaping channels for flare-accelerated electrons .
Meanwhile , relativistic protons are found to be released \sim 10 min later than the electrons , assuming their scatter-free travel along the same IMF path length .
Combining multi-wavelength imaging data on the prominence eruption and coronal mass ejection ( CME ) , we obtain some evidence of that GLE protons , with estimated kinetic energy of \sim 1.12 GeV , are probably accelerated by the CME-driven shock when it travels to \sim 3.07 solar radii .
The time-of-maximum ( TOM ) spectrum of protons is typical for the shock wave acceleration .