火光 is read as かこう (kakou) and means firelight.
かこう
kakou
かやく
gunpowder
ひだね
live coals (for firelighting)
ひつけやく
instigator
ひけし
(Edo-period) fireman
ひあそび
playing with fire
かりょくはつでんしょ
thermal power station (i.e. using combustion)
かざんかつどう
volcanic activity
かでんみん
slash-and-burn farmer (in Korea)
かせいかつどう
igneous activity
かこうげん
crater floor
かざんじょうほう
volcanic activity report
ひにあたる
to warm oneself at the fire