Formation
A subhelic arc is formed when sun rays enter one end face of an ice crystal in singly oriented columns and Parry columns, reflect off two of the crystals side faces, and exits the crystal through the opposite end face. The ray leave the crystal in the exact opposite angle, resulting in a net deviation angle of 120°, the angle for the formation of 120° parhelia.
The subhelic arc touches the top of the tricker arc, an indication the two have closely related ray paths.
The subhelic arc crosses the parhelic circle in an acute angle, and at a sun elevation of 27° it passes exactly through the 120° parhelion.
Read more about this topic: Subhelic Arc
Famous quotes containing the word formation:
“Out of my discomforts, which were small enough, grew one thing for which I have all my life been grateful—the formation of fixed habits of work.”
—Elizabeth Stuart Phelps (1844–1911)
“The moral virtues, then, are produced in us neither by nature nor against nature. Nature, indeed, prepares in us the ground for their reception, but their complete formation is the product of habit.”
—Aristotle (384–322 B.C.)
“... the mass migrations now habitual in our nation are disastrous to the family and to the formation of individual character. It is impossible to create a stable society if something like a third of our people are constantly moving about. We cannot grow fine human beings, any more than we can grow fine trees, if they are constantly torn up by the roots and transplanted ...”
—Agnes E. Meyer (1887–1970)