The First Ground Level Event of Solar Cycle 24 and its longitudinal distribution in the inner heliosphere

Ground level events (GLEs) are solar energetic particle (SEP) events that are recorded by ground-based instrumentation. The energy of the particles is so high that they produce secondary particles, i.e. protons and neutrons, which are detected as sudden increases in cosmic ray intensities measured by e.g. neutron monitors. On May 17 at 1:25 UT a M5.1 X-ray flare from the active region 11476 (N11W76) was detected accompanied by type II and III radio bursts and a coronal mass ejection heading towards STEREO A. The corresponding shock wave passed STEREO A on May 18 at 12:43 UT but missed the Earth and STEREO B. The event onset of near relativistic electrons was at SOHO (250 -700 keV),at STEREO A and B (125-335 keV)at 1:51 UT,6:05 UT and 3:38 UT, respectively. In contrast to observations close to the Earth no strong anisotropies have been observed at both STEREO A and B. The neutron monitor network recorded the first GLE for solar cycle 24.The Electron Proton Helium INstrument on board SOHO measured protons with energies of more than 600 MeV (rigidities of more than 1.2 GV). The interplanetary field direction was such that neutron monitor stations with asymptotic direction in the 1 to 2 GV range over Australia were connected best and recorded the biggest increase of 17% (Apatity and Oulu) with an onset time of 1:52 UT. Data observed close to and at Earth will be presented and the longitudinal structure of the event in the inner heliosphere will be discussed