[Propagation+Space Weather] Today's Space Weather Forecast Discussion on 2015 Sep 19 1230 UTC

[nw7us@sunspotwatch.com]

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Here is the current forecast discussion on space weather and geophysical activity, issued 2015 Sep 19 1230 UTC.

Solar Activity

24 hr Summary: Solar activity was at very low levels. Region 2415 (S19W36, Eac/beta-gamma) was responsible for several B-class flares over the period. The largest was a B9/Sf flare at 18/1313 UTC. Slight decay was observed in several of the smaller intermediate spots of Region 2415. Slight decay and separation was observed in Region 2419 (N13E03, Cai/beta). Region 2418 (S15W01, Cho/beta) was relatively stable during the period. No Earth-directed coronal mass ejections (CMEs) were observed during the period.

Forecast: Solar activity is likely to be low with a slight chance for M-class (R1-R2/Minor-Moderate) flares all three days (19-21 Sep), primarily due to the flare probability of Region 2415.

Energetic Particle

24 hr Summary: The greater than 2 MeV electron flux ranged from normal to moderate levels with a peak flux of 899 pfu at 18/1250 UTC. The greater than 10 MeV proton flux was at background levels.

Forecast: The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at normal to moderate levels on days one and two (19-20 Sep) with high levels likely on day three (21 Sep) due to a combination of coronal hole high speed stream (CH HSS) and CME influences. The greater than 10 MeV proton flux is expected to continue at background levels for the forecast period.

Solar Wind

24 hr Summary: Solar wind parameters were near nominal levels with a prolonged period of southward Bz from 19/0439-0731 UTC in conjunction with a solar sector boundary crossing into a negative (towards) sector at 19/0506 UTC. Solar wind speeds ranged from 384-482 km/s while total field was between 4-10 nT. The Bz component reached a maximum southward deflection of -8 nT at 19/0628 UTC.

Forecast: Solar wind parameters are expected to continue near nominal levels for the rest of the UTC day on day one (19 Sep). On days two and three (20-21 Sep), a glancing blow from the 18 Sep CME in conjunction with a positive polarity CH HSS is expected to enhance solar wind speed and field activity. A rise in lower energy protons in the ACE/EPAM instrument suggests a slightly earlier arrival of the 18 Sep CME, possibly around midday on day two (20 Sep).

Geospace

24 hr Summary: The geomagnetic field was at quiet to minor storm (G1-Minor) levels. Active to minor storm periods were observed from 19/0300-0900 UTC due to a prolonged period of southward Bz in conjunction with a SSBC.

Forecast: The geomagnetic field is expected to be at quiet to active levels for the rest of the UTC day on day one (19 Sep). On days two and three (20-21 Sep), a combination of CH HSS and CME effects is expected to impact the geomagnetic field. Unsettled to minor storm (G1-Minor) are expected on 20 Sep followed by active to minor storm levels on 21 Sep.

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