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

[nw7us@sunspotwatch.com]

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

Solar Activity

24 hr Summary: Solar activity was low. The largest event of the period was a C5/1n flare at 18/1419 UTC associated with a filament eruption near Region 2321 (N11W22, Eai/beta-gamma). The 7 degree long filament, centered near N05W16, resulted in an asymmetric, faint full-halo coronal mass ejection (CME), first visible in SOHO/LASCO C2 imagery at 18/1524 UTC. WSA-Enlil model output and forecaster analysis suggests this CME will arrive at Earth late on 21 Apr/early 22 Apr.

Region 2321 continued a moderate decay trend throughout the period while Regions 2324 (N19E01, Cki/beta) and 2325 (N05E10, Cai/beta) underwent only minor decay. The remaining four active regions on the visible disk were relatively stable throughout the period. Forecast: Solar activity is likely to be low with a slight chance for M-class (R1-Minor) flares on days one and two (19-20 Apr). Solar activity is likely to be very low with a chance for C-class flares on day three (21 Apr).

Energetic Particle

24 hr Summary: The greater than 2 MeV electron flux was at moderate to high levels, reaching a peak flux value of 3,740 pfu at 18/1640 UTC. The greater than 10 MeV proton flux was at background levels throughout the period.

Forecast: The greater than 2 MeV electron flux is expected to persist at moderate to high levels over the next three days (19-21 Apr). The greater than 10 MeV proton flux is expected to remain at background levels for the next three days (19-21 Apr).

Solar Wind

24 hr Summary: Solar wind parameters continued to return to near-background levels this period. Solar wind speeds steadily decreased from initial values near 550 km/s to end-of-period values near 425 km/s. IMF total field values were steady between 1-5 nT and Bz reached a maximum southward component of -5 nT early in the period. The phi angle was variable early in the period but settled into a negative (towards the Sun) solar sector orientation after 18/2015 UTC, where it remained for the rest of the period.

Forecast: Solar wind parameters are expected to persist at near-background levels on day one (19 Apr) under a nominal solar wind regime. An enhanced solar wind environment is expected on days two and three (20-21 Apr) due to the influence of a positive polarity coronal hole high speed stream (CH HSS) as well as the anticipated arrival of the 18 Apr CME late on day three (21 Apr).

Geospace

24 hr Summary: The geomagnetic field was at quiet to unsettled levels under a nominal solar wind regime.

Forecast: Geomagnetic field activity is expected to be at quiet to unsettled levels on day one (19 Apr) due to a continued nominal solar wind environment. Quiet to active geomagnetic field conditions are expected on days two and three (20-21 Apr) due to a combination of the influence of a positive polarity CH HSS and the arrival of the 18 CME late on day three (21 Apr).

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