[Propagation+Space Weather] Today's Space Weather Forecast Discussion on 2015 May 18 1230 UTC

[nw7us@sunspotwatch.com]

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Here is the current forecast discussion on space weather and geophysical activity, issued 2015 May 18 1230 UTC.

Solar Activity

24 hr Summary: Solar activity increased to low levels with a pair of impulsive weak C1/Sf flares from new Region 2349 (S21E39, Cro/beta). Region 2339 (N12W87, Hax/alpha) decayed further as it rotated nearly out of view. New Region 2350 (S16E29, Cro/beta) developed rapidly during the period but remained quiet. The remaining five spotted regions were stable or decayed further. No Earth-directed coronal mass ejections (CME) were noted during the period.

Forecast: Solar activity is expected to remain very low with a chance for C-class activity over the next three days (18-20 May). A slight chance for M-class (R1-R2/Minor-Moderate) activity continues on 18 May until Region 2339 fully rotates beyond the limb on day two (19 May).

Energetic Particle

24 hr Summary: The greater than 2 MeV electron flux reached high levels with a peak flux of 9241 pfu at 17/1735 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) threshold for the forecast period (18-20 May).

Solar Wind

24 hr Summary: Solar wind parameters at the ACE satellite remained at nominal levels as solar wind speed ranged from about about 375 km/s to 425 km/s. Total magnetic field (Bt) strength gradually increased from near 3 nT to a peak of 15 nT later in the period. The Bz component was variable early in the period before it shifted predominantly positive after 17/1700 UTC. The Bz component rotated steadily southward reaching nearly -12 nT by about 18/1000 UTC. The phi angle was mostly positive (away) during the period, but had brief variations to a negative (towards) sector. An increase in total magnetic field strength and density suggested the possible arrival of the co-rotating interactive region (CIR) ahead of the positive polarity coronal hole high speed stream (CH HSS).

Forecast: Solar wind speed is expected to gradually increase after midday on day one (18 May) due to positive polarity CH HSS influences. Solar wind speed is expected to remain enhanced through day two (19 May). By day three (20 May), solar wind parameters are expected to slowly return to nominal conditions as CH HSS effects wane.

Geospace

24 hr Summary: The geomagnetic field was quiet to unsettled.

Forecast: The geomagnetic field is expected to be at unsettled to active levels late on day one (18 May) and continuing through day two (19 May) as the Earth comes under the influence of a positive polarity, equatorial CH HSS. By day three (20 May), field conditions are expected to return to mostly quiet levels as CH HSS effects begin to wane.

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