Corona discharge with a discharge current of a few hundred microamperes can blow out a small candle flame within about 1 cm of a discharge point. A pinwheel, with radial metal spokes and pointed tips bent to point along the circumference of a circle, can be made to rotate if energized by a corona discharge; the rotation is due to differential electric attraction between the metal spokes and the space charge shield region that surrounds the tips. Corona discharge A corona discharge is an electrical discharge brought on by the ionization of a fluid such as air surrounding a conductor that is
22° halo a 22° halo unreliable as a sign of bad weather. 22° halo A 22° halo is an optical phenomenon that belongs to the family of ice crystal halos, in the form of a ring with a radius of approximately 22° around the Sun or Moon. When visible around the moon, it is called a moon ring or winter halo. It forms as the sun- or moonlight is refracted in millions of hexagonal ice crystals suspended in the atmosphere. The halo is large; the radius is roughly the size of an outstretched hand at arm's length. A 22° halo may be