The Sun Online and solar activity. December 17, 2013

The strongest solar flare was a C3.1 long-duration flare peaking on December 16 at 21h33 UTC originating from new active region NOAA AR 1927, located at the west limb. The flare was associated with a CME, observed in LASCO/C2 (first measurement on December 16 at 21h27 UTC)  and STEREO A coronagraphic data (at 21h39 UTC). The CME is travelling to the west with an estimated speed of 650 km/s (estimated via Stereo CAT), with possible arrival of a glancing blow late December 19 (UTC time). The probability for C-flares is around 70%, M-flares around 30%, with NOAA ARs 1917 and 1927 as
main source candidates. The chances for an X-flare are low. The proton flux measured by GOES, is below threshold levels. We are currently inside a slow solar wind stream with a solar wind speed of 400 km/s, as observed by ACE. The interplanetary magnetic field currently is weak with a maximum magnitude of 5 nT.
Geomagnetic conditions are quiet (K<3) to unsettled (K=3) and are expected to remain so for the next 48 hours.

Equipment: Coronado 90 + SBIG 8300s + LX75
Processing: Photoshop
Date: 12/17/13
Time UT: 19:00
Exposure 0.8 sec.

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