Geomagnetic Storm of March 2015

The magnetic storm of March 2015, named the "St. Patrick’s day event" (17 March 2015) was the first superstorm of solar cycle 24, with a corresponding Dst index reaching as low as -234 nT. It was a two-step storm; it's source can be traced back to the solar event on March 15 (a partial halo CME, associated with a C9 flare), while the second intensification was caused by the strong magnetic fields of the magnetic cloud that followed.