SOHO/LASCO Halo CME 20251201a

Halo Alert: halo-message.20251201a

UCMEO 93001 51201 1900/
51201 60248 80636 0401/ 040// 323// 41706
51201 60306 80706 12289 14299 1122/
99999

PLAIN

SOHO/LASCO HALO CME December 01, 2025

C2 Start Time: 02:48 UT

C3 Start Time: 03:06 – 07:06 UT

Type of CME:
Partial HALO CME — FRONTSIDE
pa1: 40      pa2: 40       Total Width: 360 degrees

Velocity Measurements:

C2 4 points 1408.5 km/sec @ PA 40
C3 6 points 1753.4 km/sec @ PA 40
Average through both fields: 1706.6 km/sec Acceleration: 66.19 m/sec^2.

COMMENT: A partial HALO event can be seen in LASCO C2/C3 in the far Northeast
quadrant @ 02:48 UT. As reported by NOAA, the CME is associated with a X1.9 solar
flare in AR 14299 [N22,E89]. Opening lines associated with the CME can be viewed in
SDO/AIA 193 starting @ 02:33 UT in the Northeast limb, peaking @ 02:48 UT. Multiple
filament eruptions can be seen near the Eastern limb along with post-eruption arcades
and an EUV wave.

STEREO BEACON Data
COR2 A shows a bright, asymmetric partial HALO CME in the Northeast quadrant
02:38 - 06:53 UT. Preliminary time/height measure shows 3 points - 1567.3 km/sec @ 43 deg.

Preliminary UCMEO velocity and position measurements are delivered first.
Images, movies, and time/height information for this event will be available at:

https://umbra.nascom.nasa.gov/lasco/observations/halo/2025/251201/

Best Regards,

--Taylor Lanier

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SOHO/LASCO C2 Diff	SOHO/LASCO C3 Diff	SDO AIA 171 Angstrom

GOES-19 CCOR-1	SDO/AIA 193 Angstrom Diff	STEREO COR2 Ahead Diff

SOHO/LASCO C2	SOHO/LASCO C3	GOES-19 SUVI 131 Angstrom