It always amuses me when people invoke "cosmic rays" as their stray random radiation event of choice.
I didn't choose "cosmic rays" as my "random radiation event of choice" for two reasons: first, I wrote "cosmic ray burst," the origin of many, many more particles than a single cosmic ray. A physics expert
(if there are any in this crowd) may wish to comment on the typical number of particles emanating from a single cosmic ray impacting the atmosphere.
Second, the phrase "cosmic ray burst" came from a Sun document describing the non-ECC cache memory problem.
Otherwise I agree with your posting, to which I add that no one has seen new DRAM memory chips encased within ceramic for quite a while because of the presence of trace amounts of uranium.