Multi-spacecraft observations of wide-spread SEP events and unexpected energetic particle distributions

With the end of 2009 the solar cycle 23 came to an end with solar activity increasing again. The meanwhile well separated two STEREO spacecraft in combination with further observers located at L1 provide an unique platform to investigate the longitudinal spread of energetic particles at 1 AU. In some cases the angular distribution was even far above 100 degrees as for instance in the January 17, 2010 SEP event, which shows energetic electrons and protons spreading almost all around the Sun. Large time delays between the flare and electron onsets at the spacecraft of about one hour as well as a lack of anisotropies and velocity dispersion are accompanying observations. Together with results from a 3D propagation model perpendicular diffusion is suggested to play a major role in understanding the observed particle distribution. Another example presented is the May 5, 2009 SEP event which was strongest observed at STEREO A, weaker at Earth and not by STEREO B. Multi-point radio measurements together with EUVI observations by STEREO B support an eastern source as seen from STEREO B for this event. However in-situ particle time-intensity profiles and anisotropies resemble a well connected source, rather than the eastern AR separated by ~100 degrees from the footpoint of STEREO A. These contradictory observations probably indicate an extremely asymmetric particle distribution.