On April 03, 2010, the SIDC sent out a PRESTO message alerting about the halo CME heading for Earth. PROBA2 witnesses the radiation flare associated with the plasma eruption.
PROBA2 on the cover of the ESA-portal
PRESTO alert - PRESTO alert - PRESTO alert - April 03, 2010 A B7.4 flare peaking at 09:54 UT was detected today in the Catania sunspot group 56 (NOAA AR 1059) located around S25W05. It was accompanied by a post-eruption arcade, coronal dimmings, possibly an EIT wave and a partial halo CME (angular width around 210 degrees). The CME was first detected at 10:33 UT (by LASCO) and at 09:54 UT (by SECCHI/COR2 on STEREO A). The CME was moving at a projected plane-of-the-sky speed of around 250 km/s (according to the LASCO data). Using some reasonable assumptions on the CME geometry, the true radial CME speed can be estimated to be around 600 km/s. The arrival of the corresponding ICME (possibly an interplanetary flux rope) at the Earth is thus expected in the morning of April 6. The flux rope orientation as inferred from the SOHO/EIT and SOHO/MDI data is ESW, although it may change during propagation. STEREO A and B data indicate that the bulk of the CME was propagating to the south of the ecliptic (according to the COR2 data). If the flux rope will arrive at the Earth, we expect a strong geomagnetic disturbance. Currently, the Earth is inside a slow solar wind flow (460 km/s) with average (5 nT) interplanetary magnetic field magnitude. Geomagnetic conditions are expected to remain quiet in the coming hours.
