• Weekly Highlights of Solar and Geomagnetic Activity, 11 - 17 December 2

    From SWPC.Webmaster@noaa.gov@21:1/5 to All on Mon Dec 18 13:00:13 2023
    XPost: rec.radio.amateur.space, rec.radio.shortwave, rec.radio.info

    :Product: Weekly Highlights and Forecasts
    :Issued: 2023 Dec 18 1406 UTC
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    # Weekly Highlights and Forecasts
    Highlights of Solar and Geomagnetic Activity
    11 - 17 December 2023

    Solar activity ranged from low to high levels. Of the 19 numbered
    active regions that were observed on the visible disk this week,
    Region 3514 (N05, L=141, class/area=Ekc/470 on 14 Dec) was the
    primarily responsible for the most significant activity. The region
    produced an X2.8 flare (R3-Strong) at 14/1702 UTC, the strongest
    since Sep 2017. Associated with the event were Type II (est. 2118
    km/s) and Type IV radio sweeps, a radio burst values with a
    Castelli-U profile, a Tenflare, and extremely high radio burst
    fluxes reported by the USAF RSTN observatories. Subsequent
    coronagraph imagery contained a CME signature with a halo shock and
    ejecta that was primarily headed towards the SW. This ejecta was
    modeled alongside other CME-producing events, an M5.8 flare (R2 -
    Moderate) at 14/0744 UTC, an M2.3 flare (R1 - Minor) at 14/1348 UTC
    and double peak M6.9 flare at 15/0734 UTC. The resulting WSA-Enlil
    output suggested anticipated CME influence for late on 16 Dec and
    through 17 Dec.

    Other activity of note included coronal dimming on late on 11 Dec
    and 12 Dec from the vicinity of Region 3514. The X-ray response from
    these events were below the R1 event threshold but signatures in
    coronagraph imagery were identified following the events. Modeling
    and analysis of these events suggested CME influence likely around
    14-15 Dec.

    With high levels observed on 14-15 Dec, and moderate levels observed
    on 17 Dec (all from Region 3514), the remainder of the summary
    period was at low solar activity levels. Other CME activity observed
    in coronagraph imagery was determined to not be along the Sun-Earth

    The GOES-16 greater than 10 MeV proton flux briefly exceeded the S1
    (Minor) threshold at the very end of the 15 Dec UT day. Flux levels
    reached a peak of 13.9pfu shortly after at 16/0015 UTC. The proton
    enhancement was thought to be produced by the combined contribution
    of the CMEs associated with the X2.8 flare at 14/1702 UTC and the
    M6.9 flare at 15/0734 UTC.

    The greater than 2 MeV electron flux at geosynchronous orbit was at
    high levels on 11-12 Dec. Due to an increase in geomagnetic
    activity, electron flux levels remained at normal to moderate levels
    from 13-17 Dec.

    Geomagnetic field activity ranged from quiet to G1 (Minor) storm
    levels. Quiet levels were observed over 11 Dec. An increase to
    active levels was observed after a brief period of southward Bz
    reached -12 nT. This was likely caused by a filament eruption on the
    Sun over 08 Dec. Quiet to unsettled conditions on 13 Dec increased
    to active levels again on 14 Dec (southward Bz reached ~-11 nT). On
    15 Dec, only quiet to unsettled conditions followed the arrival of a
    CME associated with activity on the Sun over 11-12 Dec. An increase
    to active conditions was observed on 16 Dec when solar wind speeds
    increased to above 500 km/s. Activity would increase to G1 (Minor)
    geomagnetic storm levels over 17 Dec as CME influence from activity
    on the Sun over 14-15 Dec passed by Earth. Total magnetic field
    strength increased to a peak 17 nT and Bz reached as far south -14
    nT as the CME passed. Solar wind speeds increased to roughly 550
    km/s before decreasing to below 500 km/s by the end of the 17 Dec UT

    Forecast of Solar and Geomagnetic Activity
    18 December - 13 January 2024

    Solar activity is expected to be low levels, with a chance for
    moderate activity (R1-R2/Minor-Moderate) throughout the outlook

    No proton events are expected at geosynchronous orbit.

    The greater than 2 MeV electron flux at geosynchronous orbit is
    expected to reach high levels due to multiple, recurrent CH HSSs on
    20-22 Dec, 03-05 Jan, and 08-10 Jan. The remainder of the outlook
    period is likely to be at normal to moderate levels.

    Geomagnetic field activity is expected to reach G1 (Minor) storm on
    18 Dec due to waning CME influence. Active levels are likely on 19
    Dec as solar wind influence is anticipated to transition to a CH
    HSS. Unsettled levels due to recurrent CH HSSs are also likely on
    20-21 Dec, 23 Dec, 30 Dec-02 Jan, and 08-10 Jan. The remainder of
    the outlook period is expected to be mostly quiet.

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