The first Solar Particle Events of the new Solar Cycle 24 have taken place. While the event on 14 August 2010 was rather small in amplitude, it was detected by ESA's Standard Radiation Environment Monitor (SREM) units flying on Herschel, Planck and INTEGRAL missions. The images below show the energetic proton fluxes at Herschel and Planck as derived from the raw SREM counts by the Singular Value Decomposition method developed at ISARS/NOA (GR). This method can be applied rapidly following an event to get the proton energy spectrum. It can be noted that while both Herschel and Planck are located at the Lagrangian point L2, 1.5 million km from the Earth anti-sunward, the difference in their halo orbit phase and diameter leads to slightly different event observation between the two missions. This event was not seen by the SREM on Rosetta, at the time much further away with helioradial distance of nearly 3 AU.

The SREM instrument is a joint development by ESA, RUAG Space (formerly Contraves Space) and Paul Scherrer Institute in Switzerland. Currently, ESA missions carrying an SREM unit include Proba-1, INTEGRAL, GioveB, Rosetta, Herschel and Planck, and further flights of the remaining SREM units are being planned. More information on the SREM and the methods applied can be found at and


Herschel SREM Solar Proton Event August, 2010

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