[Propagation+Space Weather] Today's Space Weather Forecast Discussion on 2015 May 15 1230 UTC

[nw7us@sunspotwatch.com]

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Here is the current forecast discussion on space weather and geophysical activity, issued 2015 May 15 1230 UTC.

Solar Activity

24 hr Summary: Solar activity remained at low levels. Region 2339 (N12W54, Fac/beta-gamma) leader spots slightly decayed while the trailer spots increased in number. The region remained the largest and most complex spot group on the disk and produced the largest flare observed during the period, a C4 flare at 14/1753 UTC. Additional, smaller C-class flares occurred from both region 2339 and region 2342 (N17W15, Cao/beta). All other regions on the disk were mostly simple and displayed no significant growth.

A filament eruption occurred at approximately 15/0018 UTC from just NE of Region 2342. The 8 degree long filament was centered at approximately N22E01 and its eruption was observed in SDO/AIA and GONG/H-alpha imagery. Initial analysis indicated the majority of the ejecta was likely reabsorbed, and examination of subsequent SOHO/LASCO coronagraph imagery did not reveal a resultant coronal mass ejection (CME).

The CME associated with the filament eruption from near N16W16 that occurred on 13 May was modeled earlier today. The bulk of the ejecta is expected to propagate north of the ecliptic plane with a glancing blow suggested early on day three (17 May).

Forecast: Solar activity is expected to be low with a slight chance for M-class (R1-R2/Minor-Moderate) flare activity over the next three days (15-17 May) with Region 2339 being the most likely source.

Energetic Particle

24 hr Summary: The greater than 2 MeV electron flux at geosynchronous orbit reached high levels and peaked at 4130 pfu at 14/0920 UTC. The greater than 10 MeV proton flux at geosynchronous orbit was at background levels.

Forecast: The greater than 2 MeV electron flux at geosynchronous orbit is expected to persist at moderate to high levels in response to the high speed solar wind stream described below. The 10 MeV proton flux is expected to remain below S1 (Minor) thresholds.

Solar Wind

24 hr Summary: Solar wind speed at the ACE spacecraft decreased steadily from a high just over 700 km/s to under 550 km/s by about 15/0430 UTC. It remained fairly steady afterwards as the high speed stream conditions diminished. Total magnetic field strength was fairly stable as Bt remained steady below 5nT. Bz was highly variable and reached a maximum negative deviation of -4nT. Phi remained negative throughout the period.

Forecast: The solar wind speed is expected to slowly decrease through days one and two (15-16 May) as the high speed stream diminishes and rotates away from a geoeffective position. On day three (17 May), a glancing blow from the CME that lifted off the Sun on 13 May is expected to produce an increase in wind speed and more unsettled magnetic field conditions at the near-Earth environment.

Geospace

24 hr Summary: The geomagnetic field was at quiet to unsettled levels due to higher than ambient level wind speeds and frequent periods of sustained southward Bz.

Forecast: The geomagnetic field is expected to be at quiet to unsettled levels, with a diminishing chance of active conditions on days one and two (15-16 May). One day three (17 May) conditions are expected to reach minor storming levels (G1-Minor) due to the forecasted arrival of the CME to Earth.

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