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

[nw7us@sunspotwatch.com]

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

Solar Activity

24 hr Summary: Solar activity was at low levels. The largest flare of the period, a C2.3 flare occurred at 19/1159 UTC from an unnumbered region on the Northeast limb. The remaining spotted regions were stable or decayed further. A Type II radio sweep (est. velocity of 766 km/s) was observed at 18/1436 UTC, though no notable associated flare was observed. Shortly following, SOHO/LASCO C2 coronagraph data indicated a CME occurred off the NW limb of the solar disk. This event is believed to be associated with the Type II, however it does not appear to be Earth directed. There were two additional filament eruptions; the first was in the Northwest near 18/2300 UTC and the second in the Southeast near 19/0600 UTC. No Earth-directed coronal mass ejections (CME) were noted during the period, based on available LASCO imagery.

Forecast: Solar activity is expected to remain very low with a chance for C-class activity over the next three days (19-21 May).

Energetic Particle

24 hr Summary: The greater than 2 MeV electron flux was at normal background levels. The greater than 10 MeV proton flux remained at background levels.

Forecast: The greater than 2 MeV electron flux is expected to persist at normal background levels for days one and two (19-20 May) in response to the onset of coronal hole high speed stream (CH HSS) or possible glancing blow CME effects. Day three (21 May) should see an increase to moderate or high levels with a delayed response to the elevated solar wind. The greater than 10 MeV proton flux is expected to remain below S1 (Minor) threshold for the forecast period (19-21 May).

Solar Wind

24 hr Summary: Solar wind parameters at the ACE satellite suggested the continued presence of a positive polarity coronal hole (CH) high speed stream (HSS) possibly combined with a transient feature originally expected for 17 May. Bt increased from near 5nT to near a peak of 17nT over the period. Bz fluctuated between positive and negative over the period, with deflections to near -16nT. Solar wind velocity began the period near 400 km/s, decreased to near 380 km/s until around 18/1600 UTC. Afterwards it began rising again, eventually reaching 560 km/s near 19/1000 UTC. Phi remained positive.

Forecast: Solar wind velocity is expected to continue increasing through day one (19 May) in response to the high speed solar wind stream, remain elevated for day two (20 May), then slowly return to nominal levels as CH HSS effects wane on day three (21 May).

Geospace

24 hr Summary: The geomagnetic field reached G2 (Major) storm conditions for the first period of the day then decreased to quiet to unsettled conditions.

Forecast: The geomagnetic field is expected to be at unsettled to active conditions early on day one (19 May), due to continued CH HSS effects. Mostly quiet levels are expected for days two and three (20-21 May) as the high speed wind stream begins to stabilize then wane.

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