Wednesday, March 28, 2012

Solar Sector Boundary Crossing

     A solar sector boundary crossing (polarity of the IMF reverses) indicated by ACE data has been responsible for the unsettled geomagnetic field. A high latitude Aurora Watch will be in effect over the next 24-48 hours. A favorably positioned negative polarity coronal hole is expected to continue to keep our geomagnetic field unsettled through March 29, 2011 UTC.  Old Sunspot Region 1429 is expected to return to the solar disk midday on  March 29th which should increase M-class flare probabilities.

     SOHO LASCO observed a full asymmetric halo CME on the 26th @ 23:12 UTC which was associated with Type II & Type IV radio sweeps.  This CME was determined to be a backsided event according to NOAA and not expected to be geoeffective.

      Although there was a large Sf and CME from old Sunspot Region 1429 that contributed to this halo CME there was also a filament eruption from the NE limb immediatly after, followed by a C5.3 flare the 27th @ 02:50 UTC with an associated CME (seen on SDO) from Sunspot Region  1444.  We expect this latter CME to be geoeffective.

     Here on the left we can see a CME associated with the C5.3 Sf from Sunspot Region 1444 as seen from SDO AIA 304 on March 27th at 2:57UTC.

      A Geomagnetic K-index of 4 threshold was reached: 2012 Mar 27 @ 22:35 UTC, and an EXTENDED WARNING: Geomagnetic K-index of 4 expected, continues in effect.


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