Astrophysics (Index)About

scale height

(H)
(measure of exponential falloff)

Scale height is a measure of the decrease of something that falls off exponentially by height, specifically, the height over which it falls by a factor of e (~ 2.718). Examples can include:

Despite the word "height", it might be applied to dimensions not thought of as vertical, though the term scale length is sometimes used in such cases. When it is thought of as vertical (e.g., re density or pressure of an atmosphere above a body's surface, or density of stars in a galaxy above/below its plane), it may be referred to as a vertical scale height. Equation forms associated with scale height:

A = A0e-z/H

   A       z
ln —— = - ——
   A0      H

dA
—— = -HA
dz

(The first two are forms of the solution to the differential equation.)


(science)
Further reading:
http://en.wikipedia.org/wiki/Scale_height
http://en.wikipedia.org/wiki/Scale_length

Referenced by pages:
alpha disk
atmospheric tide
e-folding time
surface brightness profile
zonal flow

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