We won't know any actionable detail till about 1 hour before it arrives at Earth. That's when 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.
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.