I think the idea that a reduction in the sun magnetic field would cause more cosmic rays to reach the surface of the earth is flawed.
Cosmic rays are basically the nuclei of atoms moving at speeds near the speed of light. They don't come from a single point, like the solar wind,
they basically come at us from all directions. While they are charged, and they do get deflected by a magnetic field, it is not the magnetic field of
the sun or the earth that protects us from them. It is the atmosphere of the earth that caused each particle to almost always hits an atom high above
earth, and becomes transformed into gamma rays and an subsequent chain of radioactive particles that don't do us much damage because there are not
that many of them.
The earths magnetic field protects our atmosphere from the solar wind, which is a flow of charged particles moving from the sun out in all
directions, but we see it as coming from a point source, not from all directions. Because the flow is coming at us roughly perpendicular to the
"magnetic axis" that connects the north and south magnetic poles, and because the solar wind moves way way slower than cosmic rays do, the magnetic
field will pull negatively charged particles to the positive pole, and vice versa. If the "magnetic axis" was parallel to the flow, we would get no
protection. The particles might get a little slowed or sped up before they hit, but they would still hit. Think about deflecting a punch by pushing
your opponents forearm to the side vs. trying to block by putting your palm right in front of your face.
The suns magnetic field may deflect a small percent of cosmic rays that are coming in along the disk of the solar system, but I don't think so.
They are much bigger and faster than the solar wind.
The idea that solar storms, or other magnetic storms could cripple the electric grid is valid, as this does happen on a small scale, and could on a
larger scale.
I forget what exactly happens if the earth's magnetic field disappears. I know it leads to more radiation, but think this takes some time for the
ozone layer to be destroyed, and then anyone who did not spend most of their time underground or underwater gets some unhealthy doses. I know it only
takes about 5m or so of water to equal the protection of the atmosphere from UV and cosmic rays. Thats why life flourished on earth in the oceans
before oxygen became plentiful, but only colonized land after we got an ozone layer.