[quote name="mabb_"]Be interesting to know what impact that would of had on earth[/quote]
Would temporarily knock out power grids and satellite/radio communications, ground airflights as well.
Cancer, not really. Its not a (short term) problem for people on the surface. People on aircraft or astronauts would get a good dose of radiation though, but I'm not sure if the exposure would be long enough to give them cancer, and airliners take precautions and ground flights whenever solar activity is very high.
The plasma doesn't slam directly directly into the earth in a straight line either, being protons they'll be either deflected or redirected by the earth's magnetic field towards the (magnetic) poles (which don't necessarily coincide with the geographical poles). There they'll do their business with the atmosphere and put on a good light show, courtesy of the laws of atomic physics.
By the way, this hard-on bearer:
<!-- m -->
http://libibm.iucaa.ernet.in/wslxRSLT.php?A1=31603<!-- m -->
recently did a conference on solar/stellar seismology where I live(I missed it though, but I got to attend a talk by Frank Close(Oxford) on antimatter), and I know one professor that has decades of work done on the Sun (namely its interior and its activity cycles).
