DICTIONARY OF GEOPHYSICS, ASTROPHYSICS, and ASTRONOMY

eccentricity
Magnitude
distance (km) Felt Intensity Damage
2 0 I Not felt
II Felt by a few people
3 15 III Hanging objects sway
IV Windows and doors rattle
4 80 V Sleepers awaken
5 150 VI Windows and glassware broken
VII Difficult to stand
6 220 VIII Branches broken from trees
7 400 IX Cracks in ground – general panic
X Large landslides – most masonry structures destroyed
8 600 XI Nearly total destruction
east-west effect An east-west anisotropy in
the arrival of cosmic ray particles. At equal inclinations
to the vertical, a higher flux of particles
is observed from the west than from the
east because of an asymmetry in the distribution
of trapped orbits (see cutoff energy). The direction
of the asymmetry (more from west than
from east) shows that primary cosmic ray particles
have a positive electric charge.
easy access region Prior to the observations
of the spacecraft Ulysses, the topology of the
heliosphere was assumed to be similar to the
one of the magnetosphere. In particular, above
the solar poles cusp-like regions were expected
where the cosmic radiation should have an easy
access to the inner heliosphere, leading to higher
fluxes over the poles compared to the ones at the
same radial distance in the equatorial plane. Although
Ulysses’ findings show an increase in the
intensity of the galactic cosmic radiation over
the sun’s poles, this increase is much smaller
than the one expected in the picture of an easy
access.
Two physical mechanisms seem to contribute
to this lack of easy access: (a) an unexpected
high level of magnetic field turbulence, leading
to an enhanced scattering and thus preventing
a relatively large number of particles from
penetrating deep into the heliosphere, and (b) a
more peanut-like shape of the heliosphere with
a wider extent over the poles owing to the fast
solarwindflowingoutofthepolarcoronalholes.
ebb current The tidal current that results
when the water in bays and estuaries is higher
© 2001 by CRC Press LLC
than that in the adjoining sea. The opposite is
referred to as a flood current.
ebb delta A deposit of sediments immediately
offshore a tidal inlet.
ebb shoal See ebb delta.
ebb tide Used essentially interchangeably
with ebb current.
eccentric Not centered, or not circular.
Refers to elliptical orbits, where eccentricity is
defined as the distance between the foci divided
by the major axis, or equivalently
ɛ 2 2 b
= 1 − ,
a
where ɛ is the eccentricity, a is the semimajor
axis, andb is the semiminor axis. The eccentricity
of a circle is zero. For parabolas eccentricity
= 1; for hyperbolic orbits, eccentricity exceeds
1. See eccentricity.
eccentric dipole An approximation to the
internal magnetic field of the Earth. It replaces
that field with the field of a magnetic dipole,
suitably oriented, but achieves additional accuracy
by displacing that dipole from the center
of the Earth in such a way that the quadrupole
harmonic terms (terms which diminish as 1/r 4 )
are reduced as much as possible.
eccentricity A characterization of conic sections,
which are also solutions to the Newtonian
equations of motion for a mass in the field of
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