• Weekly Highlights of Solar and Geomagnetic Activity, 19 - 25 April

    From OldbieOne@21:1/5 to SWPC.Webmaster@noaa.gov on Fri Apr 30 11:59:23 2021
    <SWPC.Webmaster@noaa.gov> wrote in message news:4FTWNR1Nqjz1ZW7@panix2.panix.com...
    :Product: Weekly Highlights and Forecasts
    :Issued: 2021 Apr 26 0356 UTC
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    # Weekly Highlights and Forecasts
    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.

    Thank you for continuing to post these valuable reports to USENET


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