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Prediction for CME (2026-03-18T09:23:00-CME-001)

CME Observed Time: 2026-03-18T09:23Z
DONKI Link: https://kauai.ccmc.gsfc.nasa.gov/DONKI/view/CME/45144/-1
CME Note: Partial halo CME first seen to the SE by STEREO A COR2 at 2026-03-18T09:23Z, as well as to the West in SOHO LASCO C2/C3 and GOES CCOR-1 in later frames. The source of this event is an M2.7 flare from Active Region 4392 (S16W05) which peaked at 2026-03-18T08:42Z. This flare could be seen in GOES SUVI 131, along with dimming and field line opening seen in GOES SUVI 195, 284 and STEREO A EUVI 195. The dimming feature appears to propagate towards the Northwest, suggesting possible deflection. | Arrival information: Sharp increase in B_total from already elevated ~20 nT (following the IPS at L1 as detected by ACE and DSCOVR at 2026-03-20T01:31Z) to ~36 nT. This arrival signature also includes sudden increase in solar wind speed from 450 to 550 km/s, in ion temperature from 20k to over 800k and in ion density from the already elevated 19 particles/cc to over 55 particles/cc. The shock seems to be followed by a flux rope starting at ~2026-03-21T02:18Z, with smoother rotation of magnetic field components and a drop in ion temperature and density. This arrival signature is associated with the arrival of CME 2026-03-18T09:23Z, simulated with an expected arrival at Missions Near Earth at 2026-03-20T17:24Z (+- 7 hours). Starting around 2026-03-21T11:45Z, there is an observed slow and smooth rise in B_total up to a peak of ~38.97nT at 2026-03-21T15:32Z with rotation in the magnetic field components, B_z largely northward. A further drop here in density alongside minimal change in solar wind speed and temperature indicate a likely merged second structure within this arrival, of which no current CME candidate exists following further analysis. A reverse shock is observed at 2026-03-21T19:10Z returning B_total to elevated background levels, prior to the separate start of coronal hole high speed stream with ID 2026-03-21T19:13:00-HSS-001.
CME Shock Arrival Time: 2026-03-20T20:17Z
Observed Geomagnetic Storm Parameters due to CME:
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Predicted Arrival Time: 2026-03-20T23:30Z (-12.0h, +12.0h)
Confidence that the CME will arrive: 60.0%
Predicted geomagnetic storm max Kp range due to CME: 5.0 - 7.0
Prediction Method: SIDC
Prediction Method Note:

#--------------------------------------------------------------------#
# DAILY BULLETIN ON SOLAR AND GEOMAGNETIC ACTIVITY from the SIDC     #
# (RWC Belgium)                                                      #
#--------------------------------------------------------------------#
SIDC URSIGRAM 60318
SIDC SOLAR BULLETIN 18 Mar 2026, 1235UT
SIDC FORECAST
SOLAR FLARES  : C-class flares expected, (probability >=50%)
GEOMAGNETISM  : Quiet (A<20 and K<4)
SOLAR PROTONS : Quiet
PREDICTIONS FOR 18 Mar 2026  10CM FLUX: 113 / AP: 010
PREDICTIONS FOR 19 Mar 2026  10CM FLUX: 115 / AP: 024
PREDICTIONS FOR 20 Mar 2026  10CM FLUX: 117 / AP: 041

Coronal mass ejections: The M2.7 flare (SIDC Flare 7228) was also associated with a large dimming, EUV wave  and Type II radio burst. An associated CME was observed in STEREO A COR2 at 09:23 UTC on March 18 and to the west in SOHO/LASCO-C2 data from 10:36 UTC on March 18, after a data gap.



#--------------------------------------------------------------------#
# DAILY BULLETIN ON SOLAR AND GEOMAGNETIC ACTIVITY from the SIDC     #
# (RWC Belgium)                                                      #
#--------------------------------------------------------------------#
SIDC URSIGRAM 60319
SIDC SOLAR BULLETIN 19 Mar 2026, 1236UT
SIDC FORECAST
SOLAR FLARES  : C-class flares expected, (probability >=50%)
GEOMAGNETISM  : Moderate (ISES: Major) magstorm expected (A>=50 or K=6)
SOLAR PROTONS : Quiet
PREDICTIONS FOR 19 Mar 2026  10CM FLUX: 115 / AP: 022
PREDICTIONS FOR 20 Mar 2026  10CM FLUX: 117 / AP: 044
PREDICTIONS FOR 21 Mar 2026  10CM FLUX: 118 / AP: 037

Coronal mass ejections: The CME reported yesterday, observed in STEREO A
COR2 at 09:23 UTC on March 18 and to the west in SOHO/LASCO-C2 data from
09:24 UTC on March 18, is expected to arrive at Earth late on March 20 to
early on March 21.

Lead Time: 33.40 hour(s)
Difference: -3.22 hour(s)
Prediction submitted by Melissa Kane (M2M SWAO) on 2026-03-19T10:53Z

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