• Weekly Highlights of Solar and Geomagnetic Activity, 20 - 26 September

    From SWPC.Webmaster@noaa.gov@21:1/5 to All on Mon Sep 27 13:00:12 2021
    XPost: rec.radio.amateur.space, rec.radio.shortwave, rec.radio.info

    :Product: Weekly Highlights and Forecasts
    :Issued: 2021 Sep 27 0235 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
    20 - 26 September 2021

    Solar activity was at very low to moderate levels. Region 2871 (S27,
    L=357, class/area=Dao/310 on 21 Sep) produced the largest flare of
    the period, an M2/1n flare at 23/0444 UTC. Associated with the flare
    was a Type II radio sweep (966 km/s) followed by a Type IV radio
    sweep. A subsequent CME signature was observed in SOHO/LASCO C2
    coronagraph imagery. Analysis and modeling of the event suggested
    most of the ejecta was away from the Sun-Earth line but a glancing
    blow from the periphery of the CME may be possible on 27 Sep. An
    additional M1/1n flare was produced by the same region at 23/1528
    UTC. A subsequent CME signature associated with the event was also
    analyzed with a similar potential for the periphery of the ejecta to
    influence Earth around 27 Sep.

    Other activity included a Type II radio sweep (739 km/s) associated
    with an eruption around Region 2875 (S32, L=053, class/area Bxo/010
    on 24 Sep). The associated CME signature was narrow and directed
    away from the Sun-Earth line. Most numbered active regions were in
    decay and they transited through the W hemisphere with most decaying
    to plage by the end of the period. The remaining numbered regions in
    the E hemisphere were relatively simple and quiet.

    No proton events were observed at geosynchronous orbit.

    The greater than 2 MeV electron flux at geosynchronous orbit was at
    normal to moderate levels throughout the reporting period.

    Geomagnetic field activity ranged from quiet to active levels.
    Active levels were observed on 22 Sep in response to a SSBC followed
    by influence from positive polarity CH HSS. Unsettled conditions
    were observed on 21 Sep, and 23-25 Sep due to coronal hole activity.
    The remainder of the reporting period was quiet.

    Forecast of Solar and Geomagnetic Activity
    27 September - 23 October 2021

    Solar activity is expected to range from very low to low levels. Low
    levels are likely on 27-29 Sep and very low levels are likely for
    the remainder of the outlook period.

    No proton events are expected at geosynchronous orbit.

    The greater than 2 MeV electron flux at geosynchronous orbit is
    expected to reach moderate to high levels. High levels are likely on
    29 Sep - 02 Oct, 05-08 Oct and 20-21 Oct due primarily to influence
    from multiple, recurrent CH HSSs. Normal to moderate levels are
    expected for the remainder of the outlook period.

    Geomagnetic field activity is expected to range from quiet to G2
    (Moderate) geomagnetic storm conditions. G1-G2 (Minor-Moderate)
    conditions are likely on 27 Sep in response to combined effects of
    an anticipated positive polarity CH HSS and possible glancing blow
    from a CME that left the Sun on 23 Sep. Active conditions associated
    with coronal hole activity are likely on 28-29 Sep, 05 Oct, 10 Oct
    and 19 Oct. Unsettled conditions are likely on 04 Oct, 18 Oct and
    20-21 Oct. The remainder of the outlook period is expected to be at
    quiet levels.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)