Weekly Propagation Summary – 2015 Dec 21 16:10 UTC
Here is this week’s space weather and geophysical report, issued 2015 Dec 21 0423 UTC.
Highlights of Solar and Geomagnetic Activity 14 – 20 December 2015
Solar activity was at low levels. The period was dominated by low to mid-level C-class flare activity from a number of active regions, the largest of which was a C6/1f flare at 16/0903 UTC from Region 2468 (S15, L=128, class/area=Dao/120 on 10 Dec). Region 2468 was the most productive region on the visible disk throughout the summary period, however, an unnumbered region behind the northeast limb produced multiple mid-level C-class flares within quick succession and caused a slow increase in the background GOES-15 x-ray flux late in the period.
Two asymmetrical full-halo coronal mass ejections (CMEs) were observed in SOHO/LASCO C2 coronagraph imagery on 16 Dec. The first CME was observed in C2 imagery beginning at 16/0924 UTC and was associated with the C6/1F flare mentioned above. The second CME, associated with a filament eruption, was first observed in coronagraph imagery at 16/1436 UTC. Both CMEs were determined to be Earth-directed and arrived at Earth late on 19 Dec. See the geomagnetic summary below for further information on this event.
No proton events were observed at geosynchronous orbit.
The greater than 2 MeV electron flux at geosynchronous orbit reached high levels on 14 Dec and 19 Dec with moderate levels observed throughout the remainder of the period.
Geomagnetic field activity reached active to G1 (Minor) geomagnetic storm levels late on 14 Dec and early on 15 Dec due to the influence of a corotating interaction region followed by the onset of a negative polarity coronal hole high speed stream (CH HSS). Isolated active field conditions were observed early on 16 Dec and again late on 17 Dec due to weak substorming. The CMEs from 16 Dec presumably merged in the interplanetary medium and impacted the Earth at 19/1528 UTC. During the passage of the interplanetary shock, solar wind parameters aboard the ACE spacecraft became suddenly enhanced. Total field strength values initially increased from 5 nT to 17 nT and the Bz component went strongly southward shortly after the initial shock passage. The prolonged period of southward magnetic field (-Bz) associated with the passage of the 16 Dec CMEs caused periods of active conditions late on 19 Dec and active to G2 (Moderate) geomagnetic storm levels on 20 Dec. G2 storm conditions were observed between 20/0300-0600 UTC and 20/1500-2359 UTC.
Forecast of Solar and Geomagnetic Activity 21 December – 16 January 2016
Solar activity is expected to be low throughout the period with a chance for M-class flares (R1-R2 (Minor-Moderate) Radio Blackouts) on 21 Dec through 03 Jan to the increased flare activity from an unnumbered region behind the east limb.
No proton events are expected at geosynchronous orbit.
The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at normal levels on 21-27 Dec, moderate levels on 31 Dec-02 Jan, and 14-16 Jan. High flux levels are expected on 28-30 Dec and 03-13 Jan.
Geomagnetic field activity is expected to be at active to G2 (Moderate) geomagnetic storm levels early on 21 Dec due to the waning effects of the 16 Dec coronal mass ejections. G1 (Minor) geomagnetic storms are likely on 02, 06, and 10 Jan due to the influence of recurrent coronal hole high speed streams.
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