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

[nw7us@sunspotwatch.com]

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

Solar Activity

24 hr Summary: Solar activity continued at very low levels. The largest event of the period, a long duration B5 flare, occurred at 21/0547 UTC from a region just beyond the southwest limb. No coronagraph imagery was available at the time of this summary, but due to the location of the event, any associated coronal mass ejection (CME) will likely not have an Earth-directed component. Region 2386 (N11W41, Hsx/alpha) remained stable and mostly inactive. Region 2387 (N17W03, Dai/beta) showed a decaying trend in its intermediate spots, as well as weak consolidation in its trailer spots.

After further analysis, the previously reported filament eruption in the NW quadrant, which occurred between 20/0700 and 20/0845 UTC in SDO/AIA 304 imagery, did not appear to have an Earth-directed CME. No additional CMEs were detected in satellite imagery. Forecast: Solar activity is expected to be very low with a chance for C-class flares, and a slight chance for an M-class (R1-Minor) event, over the next three days (21-23 Jul), with Region 2387 as the likely origin.

Energetic Particles

24 hr Summary: The greater than 2 MeV electron flux reached high levels with a maximum flux of 1040 pfu observed at 20/1205 UTC. The greater than 10 MeV proton flux remained at background levels throughout the period.

Forecast: The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at moderate to high levels for the forecast period (21-23 Jul) while the greater than 10 MeV proton flux is expected to remain at background levels (below S1-Minor).

Solar Wind

24 hr Summary: Solar wind parameters were indicative of nominal conditions through the first half of the period. Solar wind speed averaged near 290 km/s, total interplanetary magnetic field (Bt) ranged between 3 and 10 nT, while the greatest southward deflection of the Bz component was -2 nT. Phi angle was oriented in a positive (away) sector. Shortly after the beginning of the new UT day, the solar wind environment saw a slight enhancement. Solar wind speeds experienced a gradual increase to nearly 450 km/s, the IMF total field strength ranged between 3 nT and 14 nT, and the Bz component fluctuated between +/- 10 nT. The increase in activity is likely associated with the passing of a weak co-rotating interaction region (CIR) preceding the onset of the anticipated positive polarity coronal hole high speed stream (CH HSS). Forecast: Effects from a trans-equatorial, positive polarity CH HSS are expected to continue on day one (21 Jul). A return to nominal conditions is expected by day two (22 Jul) as CH HSS effects wane. Enhanced solar wind parameters are expected to return early on day three (23 Jul) with the expected arrival of the 19 Jul CME associated with the filament eruption from the SW quadrant centered near S32W52.

Geospace

24 hr Summary: The geomagnetic field was quiet to unsettled.

Forecast: The geomagnetic field is expected to remain at quiet to unsettled levels on day one (21 Jul) in response to positive polarity CH HSS influence. A return to quiet conditions is expected on day two (22 Jul) as CH HSS effects subside. Early on day three (23 Jul), quiet to active conditions are expected following the expected arrival of the 19 Jul CME.

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