noun
subparhelion
A rare atmospheric optical phenomenon: a bright spot on the parhelic circle below the sun, caused by reflection from ice crystals. Technical term used in meteorology and optics.
映幻日は、太陽の下に現れる光点の一種である。
A subparhelion is a kind of bright spot that appears below the sun.
幻日 (parhelion/sun dog) is a more common term for a bright spot at the same altitude as the sun, while 映幻日 specifically refers to a spot below the sun.
The term is composed of 映 (reflection), 幻 (phantom/illusion), and 日 (sun), describing a reflected phantom sun. The exact derivation is uncertain; it is a technical coinage for the optical phenomenon.