[Propagation+Space Weather] Today's Space Weather Forecast Discussion on 2015 Apr 21 1230 UTC

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Here is the current forecast discussion on space weather and geophysical activity, issued 2015 Apr 21 1230 UTC.

Solar Activity

24 hr Summary: Solar activity reached moderate (R1-Minor) levels as Region 2322 (N11W80, Dac/beta) produced an impulsive M1/Sf (R1-Minor) flare at 21/0721 UTC. A region just beyond the East limb then produced an M2/Sf flare at 21/1040 UTC. Another M-class flare was in progress at the time of this summary. Magnitude and location will be determined as imagery becomes available. Representative LASCO coronagraph imagery is not yet available to determine if there were associated CMEs from the M-flares.

Regions 2321 (N07W51, Hsx/alpha), 2322, and 2324 (N19W26, Cai/beta) also produced low level C-class flares during the period. New regions 2331 (S10E17, Bxi/beta) and 2332 (S13W10, Bxo/beta) were numbered today, but were relatively inactive throughout the period. The four remaining numbered regions on the visible disk were mostly inactive.

The coronal mass ejection (CME) first observed in LASCO C2 imagery at 21/0312 UTC appeared to be from an area just beyond the East limb and should pose no threat to Earth. No Earth-directed CMEs were observed this period. Forecast: Solar activity is likely to be low with a slight chance for M-class (R1-Minor) flares over the next three days (21-23 Apr) as Region 2322 rotates off the visible disk and the active region just beyond the East limb rotates on.

Energetic Particle

24 hr Summary: The greater than 2 MeV electron flux was at normal to high levels this period, reaching a peak of 2620 pfu at 20/1905 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 be at moderate to high levels over the next three days (21-23 Apr) in response to the anticipated onset of a positive polarity coronal hole high speed stream (CH HSS). The greater than 10 MeV proton flux is expected to persist at background levels over the next three days (21-23 Apr).

Solar Wind

24 hr Summary: Solar wind parameters reflected an ambient solar wind regime for the first half of the period. Solar wind velocities were steady near 390 km/s, IMF total field values were steady between 4-6 nT while Bz reached a maximum southward component of -7 nT. After approximately 21/0215 UTC, velocities increased to just over 600 km/s, total field was near 9 nT, and Bz became variable between -7 nT and 9 nT. Phi angle had switched from negative (towards) to a positive (away) orientation right at the beginning of the period and remained mostly positive throughout the remainder of the period. This increase in activity is likely the onset of the anticipated positive polarity coronal hole high speed stream (CH HSS)

Forecast: Solar wind parameters are expected to become further enhanced late on day one (21 Apr) due to the anticipated arrival of the 18 Apr CME, as well as the influence of the CH HSS. Elevated solar wind velocities and magnetic tendencies are forecast to persist through day two (22 Apr). Solar wind parameters are expected to begin decreasing midday on day three (23 Apr) as CH HSS and CME effects begin to wane.

Geospace

24 hr Summary: The geomagnetic field was at quiet to active levels.

Forecast: The geomagnetic field is expected to be at unsettled to active levels, with minor (G1-Minor) storming likely for the remainder of day one (21 Apr). The anticipated arrival of the 18 Apr CME midday on day one is expected to trigger periods of G1 (Minor) geomagnetic storm conditions in conjunction with the positive polarity CH HSS. Day two (22 Apr) is forecast to persist with G1 conditions. Unsettled to active conditions are expected to return after 0900 UTC on day three (23 Apr) as CH HSS and CME effects subside.

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