DICTIONARY OF GEOPHYSICS, ASTROPHYSICS, and ASTRONOMY

Wien distribution law
Wien distribution law A relation between
the monochromatic emittanceF (erg/sec/wavelength/cm
2 /steradian) of an ideal black body and
that body’s temperature T :
F∝λ −5 f(Tλ).
Wien’s law See Wien’s displacement law.
wiggle (cosmic string) After cosmological
phase transitions in which cosmic strings are
produced, the strings will trace regions where
the Higgs field departs from the low temperature
vacuum manifold of the theory. These regions
have random spatial locations and, therefore, the
ensuing string has no reason to be straight. The
string will, in general, possess an irregular shape
and small scale structures in the form of wiggles
will accumulate all along its length. Further
interactions will make the number of these
small irregularities increase. Universal expansion
does not eliminate these wiggles; hence,
wiggly strings are the most natural outcome during
network evolution.
This structure can be analytically approximated
by an effective equation of state describing
how a distant observer would perceive the
string. The effective energy per unit length Ũ
(larger than the Goto–Nambu energyU, as there
is more string matter in a given segment due to
the wiggles) and the effective tension ˜T (smaller
than the tension of a Goto–Nambu string) will
satisfy the relation Ũ ˜T=U 2 .
Furthermore, the space around the wiggly
string is no longer locally flat, and thus the string
will behave like a standard gravitational attractor.
Now particle geodesics in the vicinity of a
wiggly string will be deflected by two mechanisms:
the conical deficit angle deviation (from
far away the string looks pretty straight and featureless)
and the standard gravitational attraction.
The relative velocity between two test particles
on different sides of the string will be
δv = 8πGŨvsγs + 4πG
Ũ−˜T /(vsγs)
where vs is the velocity of the string, γs is the
corresponding Lorentz factor (1 − v 2 s /c2 ) −1/2 ,
and G is Newton’s constant. The first of these
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effects dominates for fast moving strings and
would lead to the formation of wakes. The second
one is relevant for slow strings and could be
at the root of the generation of filamentary distributions
of astrophysical large scale structures.
See cosmic phase transition, cosmic string, cosmic
topological defect, deficit angle (cosmic
string), wake (cosmic string).
Wilson cycle The Atlantic ocean is presently
“opening”, growing wider due to the creation
of new sea flow at the Mid-Atlantic Ridge. It
is expected that in the future, subduction zones
will form on the boundaries of the Atlantic, and
the ocean will close resulting in a continental
collision between the Americas and Europe and
Africa. This opening and closing of the Atlantic
has happened twice in the past and is known as
the Wilson cycle, in honor of J. Tuzo Wilson who
first proposed this behavior. The last closing
of the Atlantic Ocean created the Appalachian
Mountains and occurred about 200 million years
ago.
wind The general term for moving air, typically
driven by naturally arising pressure gradients
depending on altitude differences, solar
heating, surface temperature, and the Coriolis
force due to the Earth’s rotation.
wind chill factor The perceived sensation of
temperature, TWC, in the presence of a wind.
Based on studies of the rate of water freezing
under different conditions.
The following equations can be used to determine
the wind chill factor TWC:
Wind speed V given in mph:
TWC =Ts − ((Ts − T )(.474266
+ .303 √
V −.02 ∗ V ))
Wind speed in knots:
TWC =Ts − ((Ts − T )(.474266
+ .325518 √
V −.0233 ∗ V ))
Wind speed in m/s:
TWC =Ts − ((Ts − T )(.474266
+ .4538 √
V −.045384 ∗ V ))