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  • Weekly Highlights of Solar and Geomagnetic Activity, 25 - 31 October 20

    From SWPC.Webmaster@noaa.gov@21:1/5 to All on Mon Nov 1 13:00:18 2021
    XPost: rec.radio.amateur.space, rec.radio.shortwave, rec.radio.info

    :Product: Weekly Highlights and Forecasts
    :Issued: 2021 Nov 01 0509 UTC
    # Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
    # Product description and SWPC contact on the Web
    # https://www.swpc.noaa.gov/content/subscription-services
    #
    # Weekly Highlights and Forecasts
    #
    Highlights of Solar and Geomagnetic Activity
    25 - 31 October 2021

    Solar activity ranged from low to high levels. Low levels occurred
    on 25, 27, and 30-31 Oct. Moderate levels were reached on 26 and 29
    Oct as Region 2891 (N17, L=212, class/area Dki/350 on 29 Oct)
    produced M1 flare activity at 26/0247 UTC, 26/1557, and 29/0242 UTC.
    High levels were reached on 28 Oct as Region 2887 (S25, L=278,
    class/area Dki/440 on 24 Oct) produced an M1/1n flare at 28/0740
    UTC, an M2/1f flare at 28/1028 UTC, and an X1/2n flare at 28/1535
    UTC. Two CMEs were modelled during the period. The first was a CME
    off the SE limb beginning at 26/2024 UTC although the source region
    was unclear. It was speculated to come from Region 2887. WSA ENLIL
    modeling showed a potential glancing arrival late on 30 Oct. The
    second CME was associated with the X1 flare on 28 Oct. Type II (1457
    km/s) and IV radio emissions were observed coinciding with the flare
    and WSA ENLIL modeling of the event showed an arrival of mid to late
    on 30 Oct as well, although parameterization of the event was
    difficult.

    Coinciding with the X1 flare on 28 Oct was a greater than 10 MeV and
    100 MeV proton event. The greater than 10 MeV event began at 28/1740
    UTC, reached a peak flux of 29 pfu (S1-Minor) at 29/0250 UTC and
    ended at 30/1610 UTC. S1 thresholds were crossed once again
    beginning at 30/2100 UTC, reaching a peak flux of 11pfu at 30/2105
    UTC and ending at 30/2130 UTC due to an enhancement from the 26 Oct
    CME. The greater than 100 MeV proton event began at 28/1635 UTC,
    reached a peak flux of 7.3 pfu at 28/1815 UTC and ended at 30/0440
    UTC. The greater than 10 MeV proton flux continued to decline
    towards background levels on 31 Oct - 01 Nov.

    The greater than 2 MeV electron flux at geosynchronous orbit was at
    normal to moderate levels throughout with a peak flux of 348 pfu
    observed at 25/1700 UTC

    Geomagnetic field activity was at quiet levels on 25 Oct through
    late on 30 Oct under a nominal solar wind environment. Around
    30/1800 UTC, a weak discontinuity was observed that was believed to
    be the arrival of the 26 Oct CME. Total field increased to 11 nT
    while the Bz component deflected southward to a maximum of -10 nT at
    30/2045 UTC. Solar wind speed slowly increased to 400 km/s. A weak
    shock was observed beginning at 31/0914 UTC which is believed to be
    the arrival of a glancing blow from the 28 Oct CME. Total field
    increased from 4 nT to 13 nT while the Bz component briefly reached
    a maximum southward deflection of -11 nT at 31/1124 UTC. Solar wind
    speed continued to rise to a peak of 465 km/s at 31/1905 UTC. By
    31/1500 UTC, total field had calmed to between 5-8 nT and remained
    there through the end of the period. The geomagnetic field responded
    with an isolated active period late on 30 Oct followed by unsettled
    to G1 (Minor) storming on 31 Oct.

    Forecast of Solar and Geomagnetic Activity
    01 November - 27 November 2021

    Solar activity is expected to be at low levels with a chance for
    further M-class flare activity (R1-R2, Minor-Moderate) on 01-08 Nov
    as Regions 2887 and 2891 transit across the visible disk. Very low
    to low levels are expected on 09-15 Nov. Low levels with a chance
    for M-class flares are likely again on 16-27 Nov as Regions 2887 and
    2891 return to the visible disk on 16 Nov and 21 Nov, respectively.

    No proton events are expected at geosynchronous orbit as Regions
    2887 and 2891 decay and simplify magnetically.

    The greater than 2 MeV electron flux at geosynchronous orbit is
    expected to be at normal to moderate levels with a chance for high
    levels on 02-03 Nov due to CME influence.

    Geomagnetic field activity is expected to reach active levels on 01
    Nov followed by quiet to unsettled levels on 02 Nov as CME effects
    diminish. Unsettled levels are expected once again on 04-05 Nov and
    15-16 Nov due to recurrent CH HSS activity.

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