An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The location on the surface of the → Sun where → coronal  → magnetic field lines become tangent to the → photosphere. Bald patches play an important role in solar → magnetohydrodynamics.

→ bald, such called because of visual reference to a haircut (Titov et al. 1993, A&A 276, 564); → patch.

The spatial region where the variation of the → point spread function of an imaging system is considered negligible.

→ isoplanatic; → patch.

1) A small piece of material used to mend a tear or break, to cover a hole, or to strengthen a weak place.
2) A piece of material used to cover or protect a wound, an injured part, etc.
3) A small piece, scrap, or area of anything (Dictionary.com). → bald patch; → patchy turbulence.

M.E. pacche; of uncertain origin.

Pac, from Bašgaridi (Giroft) pac "patch; fragment," probably from *parka-, from *par- "piece" + diminutive/relation suffix -ka; cf. pâré "piece, part, portion;" parré "portion, segment (of an orange);" pargâlé "piece, portion; patch;" Kermâni pariké "portion, half;" Tabari perik "minute quantity, particle;" Lârestâni pakva "patch;" Borujerdi parru "patch;" (Fin Bandar Abbâs) park "patch;" (Tâti) pajina "patch, darn;" → part.

A → turbulence that is not continuous in space, but is separated by regions of stability and → laminar flow.

Patchy adj. of → patch; → turbulence.