Re: Might it be an opportunity?
"The cross section is not planet sized at a considerable distance from Mars. In the same way a coin held against a lightbulb casts a shadow far larger than itself on far away walls."
I read your list of qualifications and note that optics is not one of them.
The Sun is roughly 900 000 miles across. Using your coin and lightbulb example, how big would the coin need to be to provide the same shadowing at the same scale?
It is easy to work out. If you draw a cone from the Sun to Mars with the base the Sun diameter and the frustrum the Mars diameter, that includes the path of every light ray from the Sun that reaches Mars.
To obstruct all the light, therefore, a disc at any point along the cone must fully occupy the cone diameter. At half the Sun-Mars distance, for instance, the disc will be roughly half the Sun diameter. That's the area we need to fill with a magnetic field strong enough to deflect all the charged particles. (In reality as they are physical particles they have an angular velocity and it is a lot more complex, but in the direction of needing a bigger field generator.)
tl;dr the Sun is a lot bigger than a light bulb so how big would the coin be? Answer; somewhere between the size of Mars and the Sun depending on distance.
I can't avoid observing that in the context of your apparent ignorance of basic optics, accusing me of lack of vision is rather funny.