[Propagation+Space Weather] Weekly Propagation Summary - 2021 Apr 26 16:10 UTC

[nw7us@sunspotwatch.com]

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Here is this week's space weather and geophysical report, issued 2021 Apr 26 0356 UTC.

Highlights of Solar and Geomagnetic Activity 19 - 25 April 2021

Solar activity ranged from very low to R1 (Moderate) over the reporting period. Region 2816 (S24, L=262, class/area Dai/120 on 19 Apr) produced an M1/Sn flare at 19/2342 UTC, the largest of the period. The impulsive flare produced both a Type II and Type IV radio sweep. Subsequent coronagraph imagery indicated any ejecta from the event was not Earth-directed. However, the Region would go on to produce a C3/1f flare on 22/0921 UTC that would also produce a Type II and Type IV radio sweep. Analysis and modeling of this event suggested CME effects would reach Earth over 25 Apr. Over the next few days, Region 2816 would continue to slowly decay. No other CME signatures observed in available coronagraph imagery suggested a component on the Sun-Earth line.

No proton events were observed at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit was at normal to high levels. High levels were observed on 19-25 Apr before geomagnetic activity in response to a passing CME caused flux to drop to normal to moderate levels on 26 Apr.

Geomagnetic field activity was quiet to G1 (Minor) geomagnetic storm levels. G1 (Minor) storm conditions were first observed late on 23 Apr during a transition from a CIR into a negative polarity CH HSS following a period of peak total magnetic field strength of 11 nT while Bz reached as far south as -10 nT. A second isolated period of G1 (Minor) storm conditions was observed early on 25 Apr during the onset of influence from a CME that left the Sun on 22 Apr and was first observed at L1 at 24/2221 UTC. Solar wind parameters increased abruptly to a total magnetic field strength of 11 nT and Bz dropped to -8 nT. Solar wind speeds increased to ~490 km/s and would fluctuate between ~460-500 km/s through the end of the reporting period. A negative polarity CH HSS produced active conditions on 19 Apr and unsettled conditions on 20-21 Apr. Wind speeds from the HSS decreased from ~650 km/s on 20 Apr to under 450 km/s by 22 Apr. Only quiet conditions were observed on 22 Apr.

Forecast of Solar and Geomagnetic Activity 26 April - 22 May 2021

Solar activity is expected to be low with a slight chance for moderate activity from Region 2820 (S22, L=210, class/area Dai/80 on 25 Apr) over 26 Apr - 01 May, when the region will rotate around the W. limb.

No proton events are expected at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit is expected to range from moderate to high. High levels are likely on 14-22 May due to activity associated with an anticipated negative polarity CH HSS. Normal to moderate levels are likely for the remainder of the outlook period.

Geomagnetic field activity is expected to range from quiet to G2 (Moderate) geomagnetic storm levels. Active conditions are likely on 26 Apr due to waning CME effects. Active conditions are again likely on 02-03 May and unsettled on 04 May under influence from a positive polarity CH HSS. A SSBC is expected to cause unsettled conditions on 11 May and negative polarity CH HSS influence is expected to cause active conditions on 12 May, G1 (Minor) conditions on 13 May, G2 (Moderate) conditions on 14 May before decreasing to active conditions on 12-17 May as CH HSS effects wane. Another negative polarity CH HSS is expected to cause active conditions on 20 May and unsettled conditions on 21 May. The remainder of the outlook period is expected to be at quiet levels.

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