I tried writing raigeki using japanese input, and I came up with 雷撃
the first part (雷 ) means "thunder, booming sound in the air created during stormy weather " according to babylon.com
the second part (撃 ) means "poke, push "
hope that helps a bit ^_^
[edit]
according to babelfish, 雷撃 combined means "torpedo attack"
however, 雷 means thunder, and 撃 means attack.
Strange fellows, those japanese
[edit2]
If I write "kaminari" with japanese inpu, it comes up with 雷. so I guess the pronunciaton of 雷 changes if it is used in combination with 撃