The solar energetic particle (SEP) event from 26 Dec 2013 was a so-called widespread event observed by multiple spacecraft. The two STEREO and one close to Earth spacecraft spanned a total longitudinal angle of 210 degrees at that time. Together with the 25 Feb 2014 (Lario et al., 2016, Klassen et al., 2016) this is the widest event ever observed with the STEREO spacecraft. Unusually long-lasting SEP anisotropies together with prolonged intensity rise times but short onset delays point to a spatial and temporal extended SEP acceleration and/or injection.
While it is generally accepted that energetic protons can be accelerated by shocks, this is still debated for solar energetic electrons. We therefore analyze the multi-spacecraft remote-sensing and in-situ data to characterize the possible role of the shock for the electron event.
The SEP event was accompanied by a complex solar event including an interaction of the associated coronal mass ejection (CME) with a pre-event CME. The interaction happened already within a height of about 4 solar radii and before the first SEPs were detected in-situ. The radio observations by STEREO B (Fig. 1 left) show two type II bursts indicating the presence of two distinct shocks likely associated to ...