[Propagation+Space Weather] Today's Space Weather Forecast Discussion on 2021 Dec 15 1230 UTC

[nw7us@sunspotwatch.com]

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Here is the current forecast discussion on space weather and geophysical activity, issued 2021 Dec 15 1230 UTC.

Solar Activity

24 hr Summary: Solar activity was at low levels. Newly numbered region 2908 (S19E69, Dao/beta) rotated onto the visible disk, but appears to be relatively stable and quiet. An additional region trails region 2908 on the SE limb, but it too has been quiet and remains too foreshortened to properly classify and thus number at this time. Of the four numbered active regions region 2907 (S19E43, Dki/beta-gamma-delta) was the most impressive. Region 2907 exhibited overall growth and an increase in magnetic complexity as it has developed a delta spot in its leading penumbra grouping. It was also responsible for the vast majority of the C-class flares produced this period with a C8.1/SF flare occurring at 15/1044 UTC being the largest.

Between 15/0856 and 15/0900 UTC, a disappearing filament was reported by Learmonth solar observatory near S27E47. This was most likely associated with a procession of C1 flares from region 2907. Ejecta from this event is likely, as evidenced in H-alpha, but crucial coronagraph imagery is unavailable at this time. Another notable event was a large filament eruption beginning near 15/0200 UTC in the SW quadrant that is not anticipated to have an Earth-directed component. However, again, updated coronagraph imagery is needed to perform a successful analysis.

Forecast: Low solar activity is likely to continue with a slight chance for R1/R2 (Minor/Moderate) radio blackouts through 17 Dec.

Energetic Particle

24 hr Summary: The greater than 2 MeV electron flux was normal to moderate and the greater than 10 MeV proton flux maintained background values.

Forecast: The greater than 2 MeV electron flux is expected to continue at normal to moderate levels 15 Dec, with a chance for high levels on 16-17 Dec due to CH HSS effects. The greater than 10 MeV proton flux is expected to remain at background.

Solar Wind

24 hr Summary: The solar wind environment was indicative of a slow regime until approximately 15/0246 UTC when parameters became enhanced as the co-rotating interaction region ahead of a negative polarity coronal hole, and then subsequent high speed stream became geoeffective. Shortly after arrival total field increased to a peak of 16 nT and has since settled to 7-8 nT range. The Bz component of the IMF underwent its greatest southward deflection of -15 nT briefly at approximately 15/0517 UTC and also underwent a sustained deflection of ~6-7 nT from 15/0715-0902 UTC. Bz has since been northward or neutral. During this time wind speeds have undergone an increase from ambient-like levels to ~530-555 km/s. Phi began the period in a positive orientation, but became predominantly negative around 15/1835 UTC as a solar sector boundary crossing occurred.

Forecast: An enhanced solar wind environment is anticipated to continue through 17 Dec with parameters forecasted to begin to gradually wane over 16-17 Dec.

Geospace

24 hr Summary: The geomagnetic field was quiet with an isolated unsettled period to cap off the overall 24hr period.

Forecast: Quiet to unsettled levels, with an isolated period of active levels are forecast, due to possible CIR and CH HSS effects on 15 Dec. Continuing, but weakening HSS influences are expected to result in quiet to unsettled conditions 16-17 Dec.

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