Re:SOHO risk? (Score 1)

Thanks for the concern. The volume of the CME, by the time it reaches the vicinity of L1, is so enormous that the desntiy of the material is somewhat less than that in the best vacuum we can make in a laboratory on earth.

The real concern is whether the energetic, charged particles damage spacecraft and instrument subsystems: single-event upsets in silicon (memory, CPU's, &c.), damage to solar cells (each solar energetic particle [SEP] storm cuts a small notch in the performance of the solar arrays), and potential arcing in high voltage systems if they're not powered down.

Interestingly, some of the instruments with CCD detectors (MDI, LASCO, EIT) may keep observing just to keep flushing the electrons knocked loose by the SEP impacts.

We have seen bigger SEP events than this one (by a little) on SOHO anf survived. We are even able to keep recording solar wind parameters when other spacecraft's solar wind detectors are saturated by the SEP's.