XPost: rec.radio.amateur.space, rec.radio.shortwave, rec.radio.info

:Product: Weekly Highlights and Forecasts
:Issued: 2021 Oct 04 0141 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
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# Weekly Highlights and Forecasts
#
Highlights of Solar and Geomagnetic Activity
27 September - 03 October 2021

Solar activity was at very low to low levels. Low levels were
reached on 28 Sep - 01 Oct and 02-03 Oct. Region 2877 (S18, L=327,
Class/Area Dao/200 on 30 Sep) produced the strongest flare of the
period, a C2/Sn at 29/2156 UTC. Other activity included a C1 flare
at 28/0634 UTC. Associated with the flare was a Type II radio sweep
(534 km/s) and an partial-halo CME signature first seen in
SOHO/LASCO imagery around 28/0634 UTC. Analysis and modeling of the
event suggested onset at Earth late on 30 Sep - 01 Oct. The region
produced two more low-level, impulsive, C-class flares before
rotating around the SW limb on 03 Oct. Associated with the final
C-flare was a Tenflare of 100 sfu at 03/0523 UTC. The remaining
numbered active regions on the visible disk were relatively quiet
and stable.

No proton events were observed at geosynchronous orbit.

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

Geomagnetic field activity ranged from quiet to active conditions.
Active conditions were observed 30 Sep and 01-02 Oct in response to
the arrival of a CME that left the Sun on 28 Sep. Total field peaked
at 14 nT around 30/1820 UTC. The onset of the magnetic cloud was
observed after 01/1305 UTC and the Bz component was predominantly
positive over the next 18 hours. Solar wind speeds began increasing
from ~380 km/s midway through 30 Sep and peaked at ~560 km/s at
01/0120 UTC before gradually decreasing towards nominal levels over
the next two days. Unsettled conditions were observed on 27-28 Sep
due to influence from a positive polarity CH HSS. The remainder of
the summary period was at quiet levels.

Forecast of Solar and Geomagnetic Activity
04 October - 30 October 2021

Solar activity is expected to be at very low levels with a chance
for C-class flares over 04-10 Oct.

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
20-21 Oct in response to recurrent coronal hole influence. The
remainder of the outlook period is likely to be at normal to
moderate levels.

Geomagnetic field activity is expected range from quiet to active
levels. Active levels are likely 19 Oct and unsettled levels are
likely on 05-06 Oct, 08-09 Oct, 18 Oct, 20-21 Oct, and 25 Oct. All
increases in geomagnetic activity are in response to anticipated
influence from multiple, recurrent, CH HSSs. The remainder of the
outlook period is expected to be quiet.

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