Keep in mind that when designing digital electronics for the aerospace
environment (both for spacecraft and earth-bound aircraft) there are
basically 2 kinds of SEUs; one which cause a relatively 'benign' bit flip
and those that result in 'stuck bits'.

The benign bit flip (usually termed a SEU, or single-event upset), for
example in a memory device, is not permanent.  You can read and write to the
affected bit afterward.  The original information that is stored in the
affected bit(s) is obviously lost.

The case of 'stuck bits' is known as a single event latch-up (SEL).  The
latter case can be subdivided into 2 further categories; non-destructive and
destructive latch-up.

Non-destructive latch-up means that the output of the device stays at a
constant logic level, no matter how the inputs to the device change; for
example you might have a latch that won't clear.  The only remedy is to
cycle the power to the device or circuit.  A destructive latch-up causes the
same stuck 'bit' in a digital device, however, the current draw is excessive
and the device is destroyed.

Some basic techniques to mitigate single event upsets (SEU or bit flips) and
latch-up are
1. Error detection and correction (EDAC)circuits and devices
2. Watchdog timers on microprocessors
3. Semiconductor material selection and design techniques (employed by the
semi manufacturer)
4. Current monitoring
5. Multiple processors and majority voting (such as is employed on the space
shuttle)
6. Selection of SEU-immune components or components with a high threshold
for single particle effects

Many semiconductor devices can experience total dose effects from cosmic
radiation too.  This results from the accumulated effects of exposure to
ionizing radiation.  This adversely affect (i.e. degrading) the performance
of a device on a gradual basis, until it ultimately fails or does not meet
performance criteria.

The field of radiation effects on electronics is a complex one.  Keep in
mind that both digital and analog devices can both be susceptible to the
deleterious effects of ionizing radiation.  [An example of an analog device
being destroyed by single cosmic rays is a HEXFET.  Given the right
conditions, a single cosmic ray can cause a single event gate rupture in the
device, which will toast your HEXFET!]

Here's a good starting link (NASA web site) if you'd like to learn more
about radiation effects on electronics:
http://erc.gsfc.nasa.gov/
Enjoy!
Gary

p.s.  Not all ionizing radiation effects on electronics are considered
'bad'!  Sometimes ionizing radiation can actually be used to improve the
performance of a semiconductor device!  And don;t forget that we also
utilize semiconductor devices as detectors of ionizing radiation too!