DICTIONARY OF GEOPHYSICS, ASTROPHYSICS, and ASTRONOMY

supersonic
Typical supernovae light curves. Type II supernovae
have a large amount of scatter (∼ 4 magnitudes in the
peak luminosity). Type II supernovae are separated
into two groups (Plateau and Linear) based on the light
curve. Figure courtesy of Mario Hamuy.
25M⊙ core-collapse simulation 20 ms after bounce.
In this simulation, the convective region stretches from
roughly 50 km to 300 km.
supersonic Involving speeds in excess of the
local speed of sound.
supersonic string model See elastic string
model.
superspace The space of inequivalent (under
general coordinate transformations) spatial
geometries and matter fields associated to the
ADM decomposition of space-time (see geometrodynamics).
Since the metric of space is
a symmetric tensor of rank 2, there are apparently
six gravitational degrees of freedom per
space point. However, the latter are subjected
to one Hamiltonian and three super-momentum
© 2001 by CRC Press LLC
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constraints which correspond to the transformations
of the reference frame which leave the geometry
unaltered. This leaves the equivalent of
two degrees of freedom per space point or a total
of (∞ 3 ) 2 gravitational degrees of freedom.
A (generally time dependent) solution to Einstein’s
equations traces out a 1-parameter path
through superspace.
One usually needs to impose some further restriction
to the metric in order to handle the constraints
and obtain manageable results. See minisuperspace,
ADM form of the Einstein–Hilbert
action.
surface boundary layer The usually
“weakly stratified” layer at the top of natural water,
which is immediately and directly affected
by either wind or convection.
surface gravity The limiting value of the
force applied at infinity to keep a unit mass at
rest on the black hole horizon. For an explicit
example, see Schwarzschild metric. The surface
gravity is also related to the temperature of
Hawking radiation. See black hole horizon.
surface tension (σ ) Molecules in the surface
of liquid water are subjected to a net inward
force due to hydrogen bonding with the water
molecules below the surface. Surface tension is
equal to the magnitude of that force divided by
the distance over which it acts.
surface waves Seismic waves that propagate
along the surface of the Earth (as opposed
to body waves). Surface waves are either
Rayleigh (longitudinal, with a vertical component)
or Love transverse waves. Surface waves
are primarily responsible for the damage associated
with earthquakes; they propagate more
slowly than body waves so that the body waves
provide a short precursory warning of the arrival
of the destructive surface waves.
surf zone The region at a coast where breaking
waves are found.
surge In solar physics, a relatively narrow active
region jet of material in which plasma is accelerated
outward at 50 to 200 km s −1 forafew
tens of minutes. Surges reach coronal heights