March 2012 Solar Proton Event

Following a quiet period in February, March has brought increased solar activity and with it the largest solar energetic particle event of cycle 24 so far. A cluster of sunspots designated sunspot 1429 appeared at on the Eastern limb of the solar disk, on the 2nd of March. This produced an M3 class solar flare, which was followed in the morning of the 5th of March with an X1.1 class solar flare and an impressive associated CME visible on the LASCO C2 images at 04:00:05. Eastern events are not well connected magnetically to the Earth so, while the activity was quite dramatic, the increase in fluxes of solar energetic particles was not so significant. However, as the sunspot cluster migrated across the solar disk there was an even larger X5.4 class flare at 00:24, again with an associated CME which is visible on the LASCO C2 images at 00:36:06. The CME was wide enough and the activity now more centrally located such that high energy particles were more able to reach the Earth in significant quantities. The highest energy (>100 MeV) protons increased significantly after 02:00 on the morning of the 7th and ultimately rose to a peak of 69.3 particles/cm2/s (over 3 orders of magnitude above the background level) at 15:25 UT. Significant 'snow' on the LASCO C2 images caused by high energy particle impacts on the detector can be seen at 04:00 due to this flux increase.

The plots from the NOAA GOES spacecraft show the x-ray fluxes and the high energy particle fluxes as measured from geostationary Earth orbit. When the 1-8 Angstrom (top plot, blue line)rises above 10E-5 Watts/m2 the flare is classified as M-class, then it rises above 10E-4 Watts/m2 the flare is classified as X-class. NOAA/SWPC classifies Solar proton events as beginning when the particle flux in the >10 MeV channel rises above 10 particles/cm2/s.

When you click on the flux time series, data images are displayed from the AIA instrument on-board the NASA SDO (Solar Dynamic Observatory) spacecraft and the LASCO C2 coronagraph on-board the ESA/NASA Solar and Heliospheric Observatory (SOHO). The NASA SDO images show the X-ray flaring, and the SOHO/Lasco image show the CMEs being launched into space. You need to click on the time series after the peak of the shock (past 7 March, 00:31) to capture the CME. Shocks associated with CMEs can further accelerate particles in the interplanetary medium which is why we see an increasing flux of the highest energy particles for some time after the activity on or near the solar surface. These images are brought to you courtesy of our colleagues working on Helioviewer (

SDO X-ray Flare SOHO/Lasco Image of the CME launch

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"Click" on the plot to retrieve the SDO AIA and SOHO Lasco images for that datapoint from .
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