[Propagation+Space Weather] Today's Space Weather Forecast Discussion on 2015 May 17 1230 UTC

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Here is the current forecast discussion on space weather and geophysical activity, issued 2015 May 17 1230 UTC.

Solar Activity

24 hr Summary: Solar activity remained at very low levels with only B-class activity observed. Region 2339 (N11W80, Fac/beta) remained the largest and most complex spot group on the disk, but showed signs of decay as it started to rotate around the west limb. Region 2346 (S08W08, Bxo/beta) decayed during the period as its leader spots lost penumbral area and overall spot count diminished; and region 2347 (N04W10) dissipated. The remaining spotted regions were stable.

An eruptive filament was observed in SDO/AIA and GONG/H-alpha imagery at approximately 17/0715 UTC from the SE quadrant of the disc. The nearly 12 degree curved filament was centered at about S10E40. Initial analysis indicates some material may have ejected away from the Sun. We await SOHO/LASCO coronagraph imagery to determine if a coronal mass ejection (CME) occurred.

The CME first noted at 16/1230 UTC in SOHO/LASCO C3 imagery was modeled. WSA/ENLIL output showed the ejecta well north of the ecliptic plane and not geoeffective. Several smaller CMEs were noted during the period in SOHO/LASCO coronagraph imagery but none appeared to be Earth-directed.

Forecast: Solar activity is expected to be low with a slight chance for M-class (R1-R2/Minor-Moderate) flare activity over the next two days (17-18 May) with Region 2339 remaining the likely source. On day three (19 May), solar activity is expected to decrease to very low levels with C-class flares likely when Region 2339 rotates beyond the west limb.

Energetic Particle

24 hr Summary: The greater than 2 MeV electron flux reached high levels with a peak flux of 11,006 pfu at 16/1610 UTC. The greater than 10 MeV proton flux remained at background levels.

Forecast: The greater than 2 MeV electron flux is expected to persist at moderate to high levels in response to coronal hole high speed stream (CH HSS) effects. The greater than 10 MeV proton flux is expected to remain below S1 (Minor) thresholds for the forecast period (17-19 May).

Solar Wind

24 hr Summary: Solar wind parameters at the ACE satellite returned to nominal levels as solar wind speeds continued to decrease from about 435 km/s to end of period speeds near 380 km/s. Total magnetic field (Bt) strength remained fairly steady between 1-4 nT until about 16/2100 UTC, when it gradually increased to between 6-7 nT before it decreased once again towards the end of the period. The Bz component remained variable, but predominantly negative with a maximum southward deviation of -4 nT. The phi angle started the period in a negative (towards) orientation until 17/0414 UTC when the angle sharply shifted to a positive (away) sector.

Forecast: Solar wind is expected to remain at nominal speeds through early on day one (17 May). By midday on the 17th, a glancing blow from the 13 May CME is expected to impact the ACE satellite with an increase in density and a slight increase in wind speeds. By midday on day two (18 May), a positive polarity, equatorial CH HSS is expected to keep wind speeds enhanced through day three (19 May).

Geospace

24 hr Summary: The geomagnetic field was at quiet levels.

Forecast: The geomagnetic field is expected to remain at quiet levels for the first half of day one (17 May). By midday on the 17th, conditions are expected to reach active to minor storm levels (G1-Minor) due to glancing blow effects from the 13 May CME. By day two through day three (18-19 May), field conditions are expected to be at quiet to active levels under CME influences coupled with the expected positive polarity, equatorial CH HSS.

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