DICTIONARY OF GEOPHYSICS, ASTROPHYSICS, and ASTRONOMY

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two after their outbreaks, are white visually and bright in blue photographically, but not in red. dwarf galaxy A galaxy having a small mass and low luminosity. They are categorized into: DIr dwarf irregular; D Sp dwarf spiral; D El dwarf elliptical; and D Sph dwarf spheroidal (and nucleated dwarf spheroidal). dwarf nova The subset of cataclysmic variables in which hydrogen accreted on the white dwarf has ignited while degenerate and so burned explosively. The system survives and the explosions repeat in periods from about 30 years (recurrent novae) up to 10 4 −5 years (classical novae). Most or all of the accreted hydrogen and its burning products are expelled at speeds of about 1000 km/sec, leading to a visible nebula called a nova remnant. These remain detectable for decades until the gas (only about 10 −5 solar masses) dissipates. A few novae are found in the Milky Way each year, and the total number is probably 20 to 50, many of which are hidden behindgalacticdust. Theejectamakesomecontribution to the galactic inventory of carbon and of rare isotopes like nitrogen-15 and (probably) aluminum-26. dwarf spheroidal galaxies Low mass ellipsoidal galaxies, which differ from other dwarf galaxies because of their lower surface brightness and lower luminosity. More quantitatively, a dwarf spheroidal (dSph) galaxy can be defined as a galaxy with absolute blue magnitude fainter than −14 (−8.5 for the faintest dwarf spheroidal known), surface brightness lower than 22 visual magnitudes per square arcsec (a surface brightness comparable to that of the night sky at new moon), andnonucleus. dSphgalaxieshavebeen discovered in the local group, including the first ever, the sculptor system, discovered in 1937 by H. Shapley. The local group dSph galaxies appear as a collection of faint stars, with no diffuse light coming from a background of unresolved, less luminous stars. In addition, dSph galaxies are extremely poor in atomic gas. dynamical friction The retarding effect on a massive body as it moves through a cloud of lighter bodies, arising from the fact that momentum is transferred to the lighter bodies by their © 2001 by CRC Press LLC dynamic pressure gravitational interaction with the massive body. Hence, heavier objects tend to sink to the center of clusters (and some of the lighter objects are expelled in the interactions). dynamical time (DT) A family of atomic times introduced in 1984 to replace ephemeris time. DT incorporates a relativistic correction for the change in the frequency of a clock due to the effect of its different, or changing, gravitational potential. The heavier the clock, the slower it runs. The second of DT is scaled from the second of International Atomic Time. “Terrestrial Dynamical Time” (TDT) is measured on the Earth’s geoid and is meant to approximate Terrestrial Time used in solar motion theories. “Barycentric Dynamical Time” (TDB) is referred to as the solar system barycenter. TDB differs from TDT only by periodic variations. Planetary ephemerides are computed using TDB, but published referred to TDT. See Barycentric Dynamical Time, Terrestrial Dynamical Time. dynamic height Height measured in units of dynamical meters. dynamic meter A unit of gravity potential used to represent the amount of work performed in lifting a unit mass vertically 1 m and defined as 10 5 dyn-cm/gm or 10 J/kg. Dynamic meters can be related to a depth, D, in the ocean as D = gh/10, where g is the gravitational acceleration and h is the geometric depth. One dynamic meter corresponds roughly to 1.02 geometric meters at the surface of the Earth where g = 9.8m/sec 2 . dynamic pressure The inferred momentum flux ρv 2 of the solar wind (ρ density, v velocity) before it strikes the magnetosphere. It is widely used as a parameter in theoretical or empirical models of the magnetopause and bow shock, and equals the pressure on a plate perpendicular to the flow of the solar wind, far ahead of Earth, assuming it absorbs all solar wind particles that hit it. A typical value is 2 nP (nanopascal). The size of the magnetosphere shrinks (expands) with growing (diminishing) dynamic pressure. 137
dynamic recrystallization dynamic recrystallization Deformationinduced reworking of grain size, shape, or orientation in a crystal with little or no chemical change. An important mechanism of ridding the crystal of tangled dislocations, in which the new dislocation-free crystals nucleate and grow through the deformed or partially recovered structure. Dynamic recrystallization will result in a new undeformed polycrystalline state with high-angle grain boundary (i.e., no particular orientation relationship between grains). dynamics The study of motion arising from interaction between bodies, and of bodies under the influence of external fields (gravitational, electric, and magnetic). © 2001 by CRC Press LLC 138 dynamic viscosity The coefficient of viscosity, usually denoted µ equal to the ratio of the shearing stress to the shear of the motion. See kinematic viscosity, eddy viscosity, absolute viscosity. dynamo The mechanism whereby strong magnetic fields are produced from small field fluctuations through distortion of field lines by motion of conducting fluids. A dynamo effect is responsible for the Earth’s magnetic field. Numerical simulations of the Earth’s internal dynamo can, in fact, reproduce the field reversals that have taken place in the Earth’s field.
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© 2001 by CRC Press LLC DICTIONARY
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a Volume in the Comprehensive Dicti
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PREFACE This work is the result of
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Curtis Mobley Sequoia Scientific, I
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© 2001 by CRC Press LLC Editorial
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A-boundary A-boundary (or atlas bou
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accretion, Eddington presenceispart
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active front active front An active
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ADM mass is the extrinsic curvature
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afternoon cloud (Mars) are the syno
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albedo because the horizontal dimen
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Allan Hills meteorite Allan Hills m
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anabatic wind layers of the star, t
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anomalistic year anomalistic year S
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anticyclonic anticyclonic Any rotat
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archaeoastronomy A coronal arcade i
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ascending node of functions), f(−
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astronomical refraction such as mou
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atmosphere effect mass of the atmos
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aurora australis Earth’s magnetic
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axial dipole principle an order of
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Ballerina model tosphere through lu
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asalt In 1967 Sakharov identified t
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eam spread function erates auroral
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Beta Lyrae systems Beaufort Wind Sc
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Big Bang cosmology universe must ha
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inary star system time (see light-c
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lack hole black hole A region of sp
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BL Lacertae object shift z = 0.07,
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oson boson An elementary particle o
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Brazil current A generalization of
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Brunt frequency companions to somew
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utterfly diagram a very recent epoc
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Callisto ing probability is as high
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carbonaceous chondrite the object w
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Cartesian coordinates 5.4 5.2 5.0 4
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cataclysmic variable [binary models
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Celsius, Anders tions from the Eart
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Čerenkov radiation γ -rays in pur
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charge exchange an ordinary differe
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circulation density against polar a
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coastally trapped waves coastally t
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color excess color excess A measure
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comet, artificial in 2003, rendezvo
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computational relativity defined by
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conservation of angular momentum Bu
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continental plate types of continen
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Page 97 and 98: core collapse the Earth has a core
Page 99 and 100: Coriolis Coriolis A term used to re
Page 101 and 102: coronal lines Except possibly for t
Page 103 and 104: cosmic microwave background, dipole
Page 105 and 106: cosmic nucleosynthesis temperature
Page 107 and 108: cosmochemistry of space surrounded
Page 109 and 110: cosmology does not apply at small (
Page 111 and 112: crater depth-diameter plots with a
Page 113 and 114: critical level they are recorded fr
Page 115 and 116: Curie (Ci) Curie (Ci) The special u
Page 117 and 118: curve of growth classical) field th
Page 119 and 120: cyclongenesis air masses along fron
Page 121 and 122: dark matter, cold study of clusters
Page 123 and 124: decibel universe and . indicates th
Page 125 and 126: de Hoffman-Teller frame de Hoffman-
Page 127 and 128: detritus detritus The particulate d
Page 129 and 130: differential heating/cooling differ
Page 131 and 132: diffusion creep wind speed. The ter
Page 133 and 134: dike results. Because the particle
Page 135 and 136: Dione at the new minima, so that th
Page 137 and 138: dispersion dispersion A phenomenon
Page 139 and 140: diurnal motion the non-periodic var
Page 141 and 142: Doppler broadening Doppler broadeni
Page 143 and 144: dragging phenomenon skin friction.
Page 145: ductile behavior variables of space
Page 149 and 150: earthquake intensity tude represent
Page 151 and 152: echelle spectrograph a central mass
Page 153 and 154: effective pressure independent theo
Page 155 and 156: Einstein Universe where Rab is the
Page 157 and 158: Electra Electra Magnitude 3.8 type
Page 159 and 160: elevation particles have been inter
Page 161 and 162: emissivity cence of aromatic hydroc
Page 163 and 164: energy particles are accelerated at
Page 165 and 166: environmental lapse rate environmen
Page 167 and 168: equatorial bulge tor being driven u
Page 169 and 170: equilibrium vapor pressure equilibr
Page 171 and 172: Eulerian Represents Newton’s 2nd
Page 173 and 174: exact solution The path of a star i
Page 175 and 176: extreme ultraviolet (EUV) extreme u
Page 177 and 178: fall speed (velocity) can be lofted
Page 179 and 180: F corona F corona The Fraunhofer, o
Page 181 and 182: figure of the Earth See cosmic topo
Page 183 and 184: first-order wave theory the fields
Page 185 and 186: flat universe flat universe A model
Page 187 and 188: focal mechanisms rays arriving para
Page 189 and 190: force balance force balance A term
Page 191 and 192: Fraunhofer lines where M is the mas
Page 193 and 194: friction velocity friction velocity
Page 195 and 196: F star where E and B are the electr
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G gabbro A coarse-grained igneous r
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Galilei (1564-1642). See Galilean t
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not become optically thin until muc
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gas. It is either a constant volume
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equator. While geodetic latitude is
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the Earth. These interactions can g
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that extend from the sun to Earth a
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Pleistocene, about 2 million years
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the difference between the number o
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temperature is ∼ 10 K everything
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of Einstein’s general relativity
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picture in the weak-field limit in
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Time (UT1) on January 1, 1972. In t
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tra would show a dip at frequencies
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Hα condensation Hα condensation T
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harmonic model harmonic model The r
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Helios mission mination shock, and
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helium burning strated to be 4 He.
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HI region sure and temperature char
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horse latitudes from the loci of th
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Hubble radius Press 1982; Mon. Not.
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hydraulic-fracturing method hydraul
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hydromagnetic wave netized cosmic p
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hysteresis (θ), tension head (ψ),
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igneous rocks rocks are classified
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inclination inclination In geophysi
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inferior conjunction the figure) in
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initial condition time. Different r
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interconnection field interconnecti
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interplanetary dust particles (IDPs
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intertropical convergence zone (ITC
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ionosonde Each sporadic E layer can
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ionospheric regions subsequently re
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iron Kα line iron Kα line A spect
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isotope delta value (δ) element is
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Jerlov water type one because of gr
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Julian year Gregorian Date (midnigh
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K Kaiser-Stebbins effect (1984) Ani
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ing the gravitational field outside
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observed. However, these correction
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L lagoon A shallow, sheltered bay t
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Langacker-Pi mechanism In cosmology
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the last scattering surface. See qu
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Law-of-the-Wall Scaling Relations L
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light bridge Observed in white ligh
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linear wave theory Also referred to
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and downcoast areas. Sediment is tr
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longshore sediment transport Transp
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deforming forces. If a potential Vn
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defined at moderate (3 Å) resoluti
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Prospector then dropped to an altit
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M M51 Object 51 in the Messier list
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or more km where the magma resides
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oring magnetic field lines to repul
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field, the force due to the magneti
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mencement (SC) in the geomagnetic f
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and the constant κ is equal to 1 m
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California, Berkeley Space Sciences
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For instance, in a model higher der
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interval, divided by that interval:
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median diameter, median grain size
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helium (for which the early tracers
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or in components, gαβ;γ = 0 , wh
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length range, normally associated w
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mirage Appearance of the image of s
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perature characteristics are found
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stratification are slight and turbu
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ock debris carried on or within a g
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N Nabarro-Herring creep When materi
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Nasmyth spectrum F(k/k η) 10 6 10
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esponding chromospheric network def
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(NASA) initiative to test and prove
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node A point of zero displacement.
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modes. Normal modes are excited by
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special relativity, such a vector h
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oblique-slip fault low elevation an
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One-form, 1-form attached to the fl
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orbital elements higher than the OW
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OVV quasar OVV quasar Optically vio
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P packageeffect Inoceanographyandot
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would exert alone, i.e., if all the
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the psychrometric constant, KE is a
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period The amount of time for some
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the object to be viewed, as with th
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pheophytin A phytoplankton pigment
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The Planck length is the approximat
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these faint, fuzzy objects. At firs
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types across (now separated) contin
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plus the arc stretching across it
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displacement of air and water masse
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and fluid flow obeys Darcy’s law.
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eter) andζ is the vertical compone
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precipitation Any form of liquid or
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albedo of 0.064, and orbits Neptune
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Q Q “Quality”; a measure of att
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static equilibrium, air parcels hav
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R R 136 See 30 Doradus. Raadu-Kuper
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tive element is called the parent e
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Recently radon buildup in buildings
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where r is the distance from the ce
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General vectors can be written as a
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state of saturation, i.e., the rati
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plasma, for a wave of angular frequ
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γmnp, this equation is definitiona
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the position of the turning point,
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to (1), the ratio of accelerations
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evolved, the more massive component
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saturation Satellite ephemeris, r A
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scattering albedo perpendicular sho
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seafloor spreading curs at a rate o
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sedimentary sedimentary Referring t
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seismometer the body’s interior c
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sferic galactic nuclei, distinct fr
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shock spike The shock speed then ca
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silicon burning spacetime describes
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sky sky The apparent dome over the
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Snell’s law gases differ from tho
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solar eclipse solar eclipse The blo
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solar P-angle tors Mikheyev, Smirno
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solar year mic rays into the outer
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space-like infinity space-like infi
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specific storage (Ss) volume, e.g.,
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spectroradiometer diation and limit
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spiral galaxy more evolved stars. (
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spring tion and produces fluctuatio
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stable equilibrium stable equilibri
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star spots observable Stark effect,
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stiff fluid stiff fluid A fluid in
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strain Plateau and the Rockies, and
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St. Venant Equations St. Venant Equ
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sudden stratospheric warming the io
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super cloud cluster called supercel
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supernovae, 1991bg pergiant stars.
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supernovae, fallback In practice, t
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supernovae, Type Ib/Ic in the peak
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supersonic Typical supernovae light
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symmetry posite walls of the cube,
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T tachyon A hypothetical subatomic
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Tethys system. Calypso orbits at th
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TT+LG·(JD−2443144.5)·86400 sec,
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thermal conductivity The property o
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turbulence is not two-dimensional,
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tidal period The time between two p
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a precession of 2.0 ◦ yr −1 , a
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ular to the direction of the force.
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to the atmosphere, via absorption o
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orbit around the sun, are stable po
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correlated to the number of old dis
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only the fastest (speeds exceeding
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unified soil classification schemes
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V V471 Tauri stars Binary systems i
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variable star A star that changes i
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A drop with increasing distance, as
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in declination. Virgo (Latin for vi
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Located near Socorro, NM at 34 ◦
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volume scattering function (VSF) Th
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wash load the magnetopause are disp
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Weber- Davis Model physical instabi
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Wheeler- DeWitt equation The Weyl t
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Wien distribution law Wien distribu
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winter anomaly Scale Wind Condition
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X xenoliths Rocks carried to the su
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Y yardangs Streamlined elongated hi
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Z Zeeman effect The splitting of sp
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