CME impact - geomagnetic storm warning

A cannibal CME, described below, has just hit Earth's magnetic field. Solar wind data from the DSCOVR spacecraft show a stairstep structure indicative of two or more CMEs pressed together. G1- to G2-class geomagnetic storms are possible in the hours ahead. Aurora alerts: SMS Text.

Note: The following news item describes the CME before it arrived from the perspective of forecasters anticipating the storm.

HERE COMES A CANNIBAL CME: The CME heading for Earth is a cannibal. SOHO coronagraphs caught the storm cloud leaving the sun on Nov. 2nd following a slow-motion solar flare (M1.7) in the magnetic canopy of sunspot AR2891:


This CME is a cannibal because it ate one of its own kind. Cannibal CMEs are fast coronal mass ejections that sweep up slower CMEs in front of them. The mish-mash contains tangled magnetic fields and compressed plasmas that can do a good job sparking geomagnetic storms.

The slower CMEs, in this case, were hurled into space on Nov. 1st and 2nd by departing sunspot AR2887. The cannibal caught up with them almost immediately after leaving the sun. This NOAA computer model shows what happened:

The cannibal cloud swept up one whole CME and a portion of another. If NOAA's model is correct, the combined CME will make first contact with our planet around 0600 UT on Nov. 4th. The model also predicts a +250 km/s increase in solar wind speed and a 6-fold jump in solar wind density in the CME's wake. These conditions, if they materialize, would set the stage for geomagnetic storms as strong as category G2.

Subscribers to our Space Weather Alert Service will receive a text message when the CME arrives.


(Source:; November 3, 2021;
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