:Product: Forecast Discussion
:Issued: 2026 Oct 20 1230 UTC
# Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
#
Solar Activity

.24 hr Summary...
Solar activity returned to low levels, with the largest flare of the
period being a C3.5/Sf at 20/0245 UTC from Region 4557 (No6W33,
Cai/beta), which produced the majority of the activity this period as
new flux continued to emerge and consolidate. Despite Region 4551
(S15W63, Eko/beta-gamma) being relatively stable this period, it still
produced a few smaller flares earlier in the period, as did Region 4559
(S20W60, Bxo/beta) which re-developed spots this period. Region 4560
(N13W06, Dri/beta) showed some new emergence in its intermediate area
while being quiet throughout the period.

No Earth-directed CMEs were observed in the available coronagraph
imagery.

.Forecast...
Solar activity is expected to be at low levels through 22 Oct, with a
chance (25%) for M-class flares (R1-R2, Minor-Moderate) due primarily to
the flare potential of Regions 4551 and 4557.

Energetic Particle

.24 hr Summary...
The greater than 2 MeV electron flux was at normal to moderate levels.
The greater than 10 MeV proton flux was at background levels.

.Forecast...
The greater than 2 MeV electron flux is expected to remain at normal to
moderate levels through 22 Oct. The greater than 10 MeV proton flux is
expected to continue at background levels, with no S1 (Minor) solar
radiation storms expected through 22 Oct.

Solar Wind

.24 hr Summary...
Solar wind parameters were at near background levels for most of the
period: total magnetic field (Bt) averaged 5 nT, with the Bz
(north-south) component mostly positive before 20/0000z and variable
afterwards, and solar wind speeds decreasing from ~375 km/s to ~315
km/s.

After approximately 20/0600 UTC, the interplanetary magnetic field
started gradually enhancing, reaching a max of 9 nT at 20/1150 UTC with
Bz reaching a max southward deflection of 6 nT at 20/0740 UTC then
flipping sharply northward. Wind speeds also began slowly increasing,
ending the period at approximately 355 km/s.

Phi angle was predominantly oriented in the negative sector during the
first half of the period and largely positive in the second.

.Forecast...
Solar wind conditions are expected to encounter weak enhancements on 20
Oct as the anticipated influences of a positive polarity CH HSS arrive.
Elevated conditions are likely to persist through 21 Oct before
beginning to ease by 22 Oct.

Geospace

.24 hr Summary...
The geomagnetic field was at quiet levels over the past 24h.

.Forecast...
The geomagnetic field is likely to reach G1 (Minor) geomagnetic storm
levels late on 20 Oct due to anticipated effects from a positive
polarity CH HSS. Active conditions are likely on 21 Oct, followed by
mostly unsettled conditions on 22 Oct as HSS effects wane.