Ring currentA ring current is an electric current carried by charged particles trapped in a planet's magnetosphere. It is caused by the longitudinal drift of energetic (10–200 keV) particles. Earth's ring current is responsible for shielding the lower latitudes of the Earth from magnetospheric electric fields. It therefore has a large effect on the electrodynamics of geomagnetic storms. The ring current system consists of a band, at a distance of 3 to 8 RE, which lies in the equatorial plane and circulates clockwise around the Earth (when viewed from the north).
Polar motionPolar motion of the Earth is the motion of the Earth's rotational axis relative to its crust. This is measured with respect to a reference frame in which the solid Earth is fixed (a so-called Earth-centered, Earth-fixed or ECEF reference frame). This variation is a few meters on the surface of the Earth. Polar motion is defined relative to a conventionally defined reference axis, the CIO (Conventional International Origin), being the pole's average location over the year 1900.
BarycenterIn astronomy, the barycenter (or barycentre; ) is the center of mass of two or more bodies that orbit one another and is the point about which the bodies orbit. A barycenter is a dynamical point, not a physical object. It is an important concept in fields such as astronomy and astrophysics. The distance from a body's center of mass to the barycenter can be calculated as a two-body problem. If one of the two orbiting bodies is much more massive than the other and the bodies are relatively close to one another, the barycenter will typically be located within the more massive object.
NutationNutation () is a rocking, swaying, or nodding motion in the axis of rotation of a largely axially symmetric object, such as a gyroscope, planet, or bullet in flight, or as an intended behaviour of a mechanism. In an appropriate reference frame it can be defined as a change in the second Euler angle. If it is not caused by forces external to the body, it is called free nutation or Euler nutation. A pure nutation is a movement of a rotational axis such that the first Euler angle is constant.
Diurnal cycleA diurnal cycle (or diel cycle) is any pattern that recurs every 24 hours as a result of one full rotation of the planet Earth around its axis. Earth's rotation causes surface temperature fluctuations throughout the day and night, as well as weather changes throughout the year. The diurnal cycle depends mainly on incoming solar radiation. In climatology, the diurnal cycle is one of the most basic forms of climate patterns, including variations in diurnal temperature and rainfall.
TideTides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables can be used for any given locale to find the predicted times and amplitude (or "tidal range"). The predictions are influenced by many factors including the alignment of the Sun and Moon, the phase and amplitude of the tide (pattern of tides in the deep ocean), the amphidromic systems of the oceans, and the shape of the coastline and near-shore bathymetry (see Timing).
AfterglowAn afterglow in meteorology consists of several atmospheric optical phenomena, with a general definition as a broad arch of whitish or pinkish sunlight in the twilight sky, consisting of the bright segment and the purple light. Purple light mainly occurs when the Sun is 2–6° below the horizon, from civil to nautical twilight, while the bright segment lasts until the end of the nautical twilight. Afterglow is often in cases of volcanic eruptions discussed, while its purple light is discussed as a different particular volcanic purple light.
Milankovitch cyclesMilankovitch cycles describe the collective effects of changes in the Earth's movements on its climate over thousands of years. The term was coined and named after Serbian geophysicist and astronomer Milutin Milanković. In the 1920s, he hypothesized that variations in eccentricity, axial tilt, and precession combined to result in cyclical variations in the intra-annual and latitudinal distribution of solar radiation at the Earth's surface, and that this orbital forcing strongly influenced the Earth's climatic patterns.
Julian dayThe Julian day is the continuous count of days since the beginning of the Julian period, and is used primarily by astronomers, and in software for easily calculating elapsed days between two events (e.g. food production date and sell by date). The Julian period is a chronological interval of 7980 years; year 1 of the Julian Period was 4713 BC (−4712). The Julian calendar year is year of the current Julian Period. The next Julian Period begins in the year AD 3268.
Standard atmosphere (unit)The standard atmosphere (symbol: atm) is a unit of pressure defined as 101325 Pa. It is sometimes used as a reference pressure or standard pressure. It is approximately equal to Earth's average atmospheric pressure at sea level. The standard atmosphere was originally defined as the pressure exerted by a 760 mm column of mercury at and standard gravity (gn = 9.80665m/s2). It was used as a reference condition for physical and chemical properties, and was implicit in the definition of the Celsius temperature scale, which defined as the boiling point of water at this pressure.
