Evidence for solar wind modulation of lightning

Or, the earth's electric fields repel more cosmic rays when it is excited by solar winds.

It's the magnetic field in the solar wind deflecting the charged cosmic rays. It is not a scattering effect from increased density.

What is talked about here is the arrival of the high speed stream, but it is not the high speed stream itself. What is important is the momentum transfer from the high speed stream to the slow stream out in front of it. This builds up to a genuine shockwave by Mar's orbit but at earth it is just a smooth increase in dynamic pressure. There's a pile up of the "frozen-in" magnetic field at this co-rotating interaction region and that field's intensity deflects the cosmic rays (and other charged particles) from certain directions at certain distances.

This is the pretty much the same mechanism as the Forbush decrease associated with coronal mass ejections.