Glossary - Rock Magnetic Cyclostratigraphy - page 159

Insolation The amount of incoming solar radiation received on a given
surface area during a given time period.
Isothermal remanent magnetization (IRM) The magnetization that
results from the application of a DC magnetic field to a sample.
J rs Saturation remanence, also known as an SIRM. This is the greatest mag-
netization acquired by a sample after a sample has reached J sat , but it is
measured when the field that caused it has been turned off.
Low-pass filter A filter that only passes low frequencies and suppresses or
attenuates all higher frequencies.
Magnetostratigraphy The polarity sequence recorded by either a section of
sedimentary or igneous rocks. Typically, sedimentary rock sequences record
the most complete and continuous records of geomagnetic field reversals. A
local magnetostratigraphy of a rock sequence is then tied to the geomagnetic
polarity time scale to assign absolute ages to the polarity interval boundaries.
Milankovitch cycles Changes in insolation caused by Earth's precession,
obliquity, and orbital eccentricity.
Multidomain (MD) Magnetic mineral grains or particles which are large
enough to have divided into several magnetic domains, i.e., regions which
are uniformly magnetized.
Multitaper method (MTM) A modification of Fourier spectral analysis in
which multiple spectral estimates are calculated from the same sample,
each time the data series being multiplied by a different orthogonal taper
function. The technique was developed by D.J. Thomson.
Natural remanent magnetization (NRM) A blanket term used to indicate
all remanent magnetizations that are naturally acquired by a rock. It usu-
ally refers to the magnetization measured before a rock sample is demag-
netized or before it has had a laboratory remanence applied to it.
Nyquist frequency The highest frequency (shortest period) cycle detect-
able by a spectral estimator for the given sampling interval. A cycle must
be sampled at least twice. The Nyquist frequency is given by: f Nyq = 1/
(2*SI) where SI is the sampling interval.
Obliquity The tilt of the Earth's rotation axis to the plane of the ecliptic, the
orbital plane of the Earth around the Sun. It is currently about 23.4° and
varies from about 22° to 24.5° with a 41 kyr period.
Paramagnetism The induced magnetization acquired parallel to the
applied field by non-ferromagnetic particles.
Precession or precession of the equinoxes or axial precession The slow,
continuous “wobble” of the Earth's rotation axis with respect to the stars.
The precession of the Earth's rotation axis is caused by the gravitational
pull of the Moon and the Sun on the Earth's equatorial bulge and causes
a slow ~26 kyr precession of the Earth's rotation axis in space.
Precession index or precession parameter or climatic precession or
precession-eccentricity syndrome The drift of the seasons and
changes in Earth-Sun distance during the year is due to the Earth's
precession and the precession of the orbital perihelion (“apsidal
precession”). These motions produce a ~21 kyr cycle that is modulated by
the orbital eccentricity and is a strong interannual insolation signal.