564
FXXX12 KWNP 100031
DAYDIS

:Product: Forecast Discussion
:Issued: 2024 Oct 10 0030 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC contact on the Web
# http://www.swpc.noaa.gov/wwire.html
#
#             Forecast Discussion
#
Solar Activity

.24 hr Summary...
Solar activity reached high levels with an X1.8 flare at 09/0156 UTC
from Region 3848 (N12W25, Dki/beta-gamma-delta). The event was
accompanied by Type II (5176 km/s) and Type IV radio sweeps as well as a
2700 sfu Tenflare and Castelli U signature. The associated Halo CME is
Earth directed and model analysis suggests arrival 10 Oct. There was
also an impulsive X1.4 at 09/1544 UTC from Region 3842 (S13W90,
Eki/beta-gamma). The flare was accompanied by a 229 pfu Tenflare and a
Type IV radio sweep. The associated CME becomes visible in coronagraph
imagery at 09/1612 UTC and analysis determined the event to be well
ahead of Earths orbit. 3842 also produced an impulsive M7.7 flare at
09/2312 UTC.

There are five regions on the visible disk, the two already mentioned
along with 3849 (S07W02, Eai/beta-gamma), 3850 (S10W06, Cao/beta), and
3852 (S14E40, Dki/beta-gamma) which were mostly inactive.

.Forecast...
Solar activity is expected to be moderate (R1-R2, Minor-Moderate) with
a chance for isolated X-class (R3-Strong or greater) flares through 12
Oct.

Energetic Particle

.24 hr Summary...
The greater than 2 MeV electron flux is rebounding and is getting close
to crossing the 1000 pfu threshold as of 09/1900 UTC. The greater than
10 MeV proton flux exceeded the 1000 pfu threshold reaching S3 (Strong)
levels at 09/1255 UTC, 09/1724 UTC and again at 09/2035 UTC. The greater
than 10 MeV flux has been remaining just below the S3 threshold during
most of the period. The greater than 100 MeV proton flux crossed the
alert threshold of 1 pfu at 09/0408 UTC reaching a peak of 4 pfu at
09/0805 UTC and has been on the slow decline since.

.Forecast...
The greater than 2 MeV electron flux will likely cross the alert
threshold or hover just below going into 10 Oct. Electrons will become
suppressed at geostationary orbit as the CME associated with the X1.8
flare arrives and will remain suppressed until the solar wind eases 12
Oct. S1-S2 (Minor-Moderate) solar radiation storm levels are expected to
continue through 10 Oct and begin a slow recovery through the rest of
the period.

Solar Wind

.24 hr Summary...
Solar wind parameters continue to show waning CME influences with the
total magnetic field dropping to around 6 nT and the Bz component
becoming variable around +/-3 nT. Solar winds have decreased after
09/1800 UTC from around 425 km/s to 300 km/s. The phi angle has been
mostly positive (away from the Sun).

.Forecast...
Solar wind parameters are expected to become disturbed early to mid UTC
day on 10 Oct. The CME associated with the X1.8 flare has a measured
velocity between 1400-1600 km/s, the CME will lose speed as it traverses
interplanetary space and is expected to reach Earth with a velocity of
600-700 km/s according to Enlil model guidance. The solar wind will
experience an abrupt jump, or sudden impulse, which will be associated
with the shock of the CME. The winds will ease slightly following the
shock but will maintain higher velocities as the bulk of the magnetic
cloud moves in. The total magnetic field is expected to increase upon
arrival. CME influences will likely continue into 11 Oct with waning
influences 12 Oct.

Geospace

.24 hr Summary...
Waning influences from CME arrival caused the geomagnetic field to hit
G1 (Minor) storming levels between the 03-06 synoptic periods and has
been Active to Unsettled since.

.Forecast...
The geomagnetic field will remain Quiet to Unsettled prior to the
arrival of the CME associated with the X1.8 flare. After the sudden
impulse described in the Solar Wind section arrives at the ACE satellite
it will be roughly 35-45 minutes (if speeds are 600-700 km/s) before
magnetometers on the Earths surface start to respond. Behind the shock
will be the bulk of the magnetic cloud which will maintain a disturbed
geomagnetic field for 10 Oct into 11 Oct.

The magnitude of the flare, the associated protons, the location of the
region being near center disk, and a strong consensus on the speed leads
to high confidence in timing and potential magnitude. Current thinking
is that the bulk the disturbance will be on 10 Oct with elevated but
waning influences into 11 Oct. A G4 (Severe) geomagnetic storm Watch has
been issued for 10 Oct and 11 Oct.

Caveats to be considered; there is usually a +/-8 hour time window of
arrival, the current 3-day forecast has an arrival around 10/1200 UTC
and the orientation of the magnetic cloud is always uncertain. If the Bz
component of the magnetic field remains northward impacts will be
minimal but if a sustained southward Bz is what comes in contact with
Earths magnetosphere for an extended period then G4, possibly G5
(Extreme), conditions will be possible.

-Bri