The mag field of the sun affects spot/flare activity when influx of cosmic dust/gas/particles (mostly electron but some protons as well) cause a reversal in equatorial polarity or sets up an imbalance in equatorial polarity.

this 'excites' the sun and results in hyperactivity ie flares and spots
Severe mag field disruption via heavy influx of protons, possibly foreign neutrons, maybe the cause of CME, but I have no data on that in front of me.

Dawn