Subject: Weekly Highlights of Solar and Geomagnetic Activity, 18 - 24 March 2024

:Product: Weekly Highlights and Forecasts
:Issued: 2024 Mar 25 0644 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
18 - 24 March 2024

Solar activity during the week reached high levels. The largest
flare was an X1.1/ 2F at 23/0133 UTC. Region 3614 (N17, L=224,
Dso-B/210 on 23 Mar) produced the flare which appeared along a
filanment channel to the north of the spot group. A 240 SFU 10cm
radio burst and Type II sweep (791 km/s) were observed. The flare
was also accompanied by an EUV wave, dimming and post-eruptive
arcades visible in GOES SUVI 195 Angstrom imagery. An asymmetric
halo cme was first visible in SOHO/LASCO C2 imagery at 23/0048 UTC.
Plane of sky measurments averaged from C2 and C3 suggested the CME
was moving at 1492 km/s. While Region 3614 produced the largest
flare of the week, Region 3615 (S13, L-215, Fkc-BGD/810 on 24 March)
was the most prolific. It produced 27 M-class flares during the
week, three of which were greater than M5 (R2). The largest was an
M7.4, 3B on 20/0736 UTC.

The X1.1 and CME described above triggered a 10 MeV proton event.
The 10 MeV flux began rising at 23/0400 UTC, crossed the 10 pfu (S1)
threshold at 23/0815 UTC and the 100 pfu (S2) threshold at 23/1405
UTC. The event peaked on 23/1820 UTC at 956 pfu. A second peak of
687 pfu was observed at 24/1230 UTC as the CME described earlier
approached.

The greater than 2 MeV electron flux at geosynchronous orbit ranged
from normal to moderate levels throughout the week.

Four distinct geomagnetic storms ocurred during the week. The first
was associated with a CME arrival at 21/0225 UTC. Bz dipped
southward to -12 nt and, and a couple of periods of prolonged
southward Bz led to three synoptic periods of minor (G1) geomagnetic
storm conditions between 21/1200-2100 UTC. The second even began on
22/2320 UTC Bz shifted southward around 23/0100 UTC and remained
there for about 7 hours. This gave rise to two periods of minor (G1) geomagnetic storm conditions between 23/0300-0900 UTC. This activity
was most likely a CIR, in advance of a negative polarity coronal
hole, based on the density increase and rotation of the Phi angle
..Solar wind speed and temperature began rising at the end of the
storm activity, suggesting the high-speed stream had become
geoeffective. The third storm began with the 23/1800 UTC UTC
synoptic period (Kp=5-, G1), peaked during the 2100-0000 UTC
synoptic period, reaching Kp=6- (G2), and returned to G1 conditions
for the final period from 24/0000 UTC to 24/0300 UTC. The final
storm began with the arrival of the CME described in the first
paragraph. The interplanetary shock arrived at L1 at 24/1411 UTC and
a sudden impulse (377 nT at Meanook Observatory) was detected at
24/1437 UTC. Solar wind speed jumped from the 500-550 km/s high
speed stream values to approximately 800 km/s and remained elevated.
Bz dipped southward to -27 nT at 24/1510 UTC. Kp ranged from 6+ (G2)
moderate storm conditions to 8o (G4) sever conditions between
24/1200-2100 UTC. The severe synoptic period was from 24/1500-1800
UTC. The magnetic cloud appears to have arrived around 24/1826 UTC
distinguised by a slow rotation of the Phi angle. Earth was still
within the magnetic cloud at the end of this reporting period.

Forecast of Solar and Geomagnetic Activity
25 March - 20 April 2024

The threat of high solar activity remains throughout the coming
week. Region 3615 (Fkc-BGD) is expected to remain on the visible
disk until March 29th-30th. The departure of Region 3615 is
anticipated to bring a period of low solar activity with a lingering
chance for M flares. Regions 3614 and 3615 are expected to return on
April 11th, increasing the potential for moderate to high activity.

Along with the high solar activity, there is a chance for another
proton event at geosynchronous orbit, with the greatest threat from
Region 3615 until it departs. The threat will decrease until the
region returns on April 11th.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be at moderate to high levels during the forecast
period. The high levels are anticipated between March 28th-31st, and
again from 6-8 April in the wake of coronal holes.

The beginning of the forecast period is expected to see strong (G3)
geomagnetic conditions declining to mostly quiet conditions after
March 26th. Levels will increase to potentially minor (G1) levels
with the influence of a coronal hole high speed stream on April
3rd-5th. High speed streams on April 9th-11th and 19th-20th are
expected to bring less than minor (G1) storm conditions. The threat
of more CMEs and subsequent storms associated with Regions 3614 and
3615, or with new regions that emerge, remains.


--- MBSE BBS v1.0.8.4 (Linux-x86_64)
* Origin: NOAA Space Weather Prediction Center (3:633/280.2@fidonet)