[HN Gopher] G4 (Severe) Watch in Effect for 12 November
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       G4 (Severe) Watch in Effect for 12 November
        
       Author : hnburnsy
       Score  : 11 points
       Date   : 2025-11-11 21:28 UTC (1 hours ago)
        
 (HTM) web link (www.swpc.noaa.gov)
 (TXT) w3m dump (www.swpc.noaa.gov)
        
       | h2zizzle wrote:
       | >To include
       | 
       | "Including", or "which is to include/which may include".
        
       | vorpalhex wrote:
       | We had a G5 in 2024 and I believe the only possibly related issue
       | was some cellular infrastructure in Europe (local impact only).
       | 
       | Modern technology is significantly more hardened than telegraphs
       | in the 1800s.
        
       | superkuh wrote:
       | But we won't actually know anything till about 1 hour before it
       | happens. That's when any potential interplanetary coronal mass
       | ejections actually have their magnetic field orientation and
       | intensity measured by ACE and other satellites far out at the L1
       | lagrange point: https://services.swpc.noaa.gov/images/ace-mag-
       | swepam-24-hour...
       | 
       | If you see the red line on this plot, the interplanetary magnetic
       | field, be more than -10 nanotesla for about 4 hours then there's
       | a good chance of lower than normal latitude aurora. Negative
       | means the magnetic field is pointing downwards out of the
       | ecliptic plane of the solar system and this is the most
       | energetically favorable orientation for reconnecting CME magnetic
       | field lines with Earth's magnetic field lines and letting solar
       | particles/energy in.
       | 
       | It can be 20nT positive (upwards) magnetic field with intense
       | density and high velocity but still be a non-event aurora-wise
       | just because energy is delivered to the Earth's ring currents at
       | 10x slower rate than if it's pointing downwards.
       | 
       | None of the WSA-ENLIL or related predictive models take into
       | consideration the magnetic field orientation of iCMEs because
       | it's really hard to know from remote observations. They can be
       | thought of as warnings to pay attention to the ACE L1
       | measurements.
        
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       (page generated 2025-11-11 23:01 UTC)