blue flash

== English == === Noun === blue flash (plural blue flashes) (meteorology, astronomy) A very rare phenomenon observed in the morning or evening when the sun is crossing or immediately below the horizon, in which a momentary flash of blue light appears above the upper rim of the solar disk, caused by refraction of light in the atmosphere. (nuclear physics) A phenomenon sometimes observed when a criticality accident occurs in nuclear materials, inducing a discharge of radiation into the environment. === See also === green flash === Anagrams === flushable