[Propagation+Space Weather] Today's Space Weather Forecast Discussion on 2015 Sep 20 1230 UTC

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Here is the current forecast discussion on space weather and geophysical activity, issued 2015 Sep 20 1230 UTC.

Solar Activity

24 hr Summary: Solar activity reached moderate levels due to an M1 flare observed at 20/0503 UTC from newly numbered Region 2420 (N09E78, Hax/alpha). Both regions 2415 (S19W49, Eac/beta-gamma) and 2419 (N12W12, Cai/beta) contributed to low level C-class flaring during the period. Slight decay was observed in Region 2419 while consolidation was seen in the leader spots of Region 2415. An accurate classification of Region 2420 is not possible at this time due to limb proximity.

Beginning at approximately 20/0633 UTC in SDO/AIA 193 imagery, a filament eruption was observed in the SE quadrant. We are currently waiting on coronagraph imagery to determine if there was an associated coronal mass ejection (CME).

Forecast: Solar activity is expected to be at low levels with a chance for M-class (R1-R2, Minor-Moderate) flares over the forecast period (20-22 Sep). The most likely regions to produce M-class activity are Regions 2415 and 2420.

Energetic Particle

24 hr Summary: The greater than 2 MeV electron flux ranged from normal to moderate levels with a peak flux of 426 pfu observed at 19/1445 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 day one (20 Sep) with high levels possible on days two and three (21-22 Sep) due to a combination of coronal hole high speed stream (CH HSS) and coronal mass ejection (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 indicated the passage of the 18 Sep CME. The earlier than expected arrival indicated a more Earthward direction than could be previously detected in coronagraph imagery. At 20/0527 UTC, an IP shock passage was observed at the ACE spacecraft. Total field quickly increased from 8 nT to a maximum of 22 nT at 20/0536 UTC while the Bz component deflected southward to a maximum of -17 nT. Solar wind speed increased from 443 km/s to 540 km/s initially with further increases to a maximum near 626 km/s, albeit averaging in the mid to upper 500 km/s range. By the end of the period, total field had decreased to near 9 nT. Phi angle was variable until 20/0000 UTC when it became mostly positive (away).

Forecast: Solar wind conditions are expected to continue to be enhanced under CME influence for the rest of day one (20 Sep). CME activity is expected to give way to a positive polarity coronal hole high speed stream (CH HSS) on days two and three (21-22 Sep). Solar wind speeds are likely to remain in the 500 km/s range through late on 22 Sep.

Geospace

24 hr Summary: The geomagnetic field was initially at quiet to unsettled levels until the 20/0300-0600 UTC period. A prolonged period of negative Bz caused an initial G1 (Minor) storm period during this time. By 20/0605 UTC, a geomagnetic sudden impulse of 27 nT was observed at the Boulder magnetometer indicating the arrival of the 18 Sep CME. The geomagnetic field responded to CME activity with a period of G3 (Strong) geomagnetic storming from 20/0600-0900 UTC and G1 (Minor) storm levels from 20/0900-1200 UTC.

Forecast: The geomagnetic field is expected to slowly recover through early on day two (21 Sep) as CME effects diminish. Active to G1 (Minor) storm periods are expected during this time. CME effects are expected to give way to a geoeffective CH HSS causing unsettled to active periods through the majority of day two and into day three (22 Sep).

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