Can a CME's magnetic orientation be predicted before arrival?
In plain words
A coronal mass ejection (CME, a cloud of magnetized gas thrown out by the Sun) causes a big storm only if its magnetic field points opposite to Earth's. Today that direction is measured only about an hour before arrival, by a spacecraft just upstream of Earth.
Precise statement
Predict the time series of the north-south interplanetary magnetic field component $B_z$ inside a CME at $1\,\mathrm{au}$ from observations at or near the Sun (photospheric magnetograms, coronagraph images), including rotation, deflection and erosion during propagation. An answer is a forecast method that achieves skill above climatology in $B_z$ sign and magnitude with lead time of a day or more.
What would settle it
Blind forecasts for a statistical sample of CMEs scored against in-situ $B_z$ at L1, beating climatological and persistence baselines.