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Glossary of Scientific Terms
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A medium-sized solar flare; they can cause brief radio blackouts that affect Earth's polar regions. Minor radiation storms sometimes follow an M-class flare. It have a particular range of energy output of X-ray radiation of 1E-5 minor or equal to I minor 1E-4.
It is an increase in current and brightness of the channel of a lightning flash. It occurs during the continuing current phase.
The square vertical wave number of gravity waves. It has an important hole to study the vertical gravity waves propagation.
Solar matter ejected permanently between the supergranules, in the form of proton and electron tongues.
A geomagnetic and/or cosmic storm has been associated with this flare.
A magnetic cloud is a transient event observed in the solar wind, corresponding to a region of enhanced magnetic field strength, smooth rotation of the magnetic field vector and low proton density and temperature. Magnetic clouds are a possible manifestation of an ICME.
Sudden increase in the Earth’s magnetic field caused by increase of the ionospheric electric currents, which are due to increase of the ionization in the D and E ionospheric layers. Ionization’s increase is caused by sudden increase in the X-rays flux emitted during a solar flare.
The angle between magnetic north and geographic north at a particular location.
It is a physic entity capable to move charges. It is generated by electric currents.
Magnetic field lines are a representation of the magnetic field and are also a good qualitative tool for visualizing magnetic forces.
In physics, it is term used to describe the total amount of magnetic field lines in a given region.
The amount of magnetic flux (in Webers) transferred every second by solar wind coupling at the magnetopause from the dayside magnetosphere to the tail; in a steady state this is equal to the flux transferred every second from the tail back toward the dayside through the central part of the magnetosphere.
It is analogous to geographic local time.
It is a magnetic field configuration where the field strength changes when moving along a field line. The mirror effect results in a tendency for charged particles to bounce back from the high field region.
It is a change of the Earth's magnetic field to the opposite polarity. This has occurred at irregular intervals during geologic time. Polarity reversals can be preserved in sequences of magnetized rocks and compared with standard polarity-change time scales to estimate geologic ages of the rocks.
Region on a body where magnetic inclination is at a maximum.
Increase the plasma pressure in directions perpendicular to the magnetic field line due presence of the own magnetic field.
SEE Reconnection.
A descriptive term for the changes in the global magnetic field as a result of the solar wind (in terms of energy, particles, magnetic field and pressure variations). Storms often begin with a sudden enhancement in the horizontal field strength followed over a number of hours by a decline in this field strength before recovery to normal levels over few days.
A descriptive term for the changes over few hours in the local magnetic field, at high latitudes, as a result of input from the solar wind and current flows in the magnetotail. Can cause GIC at high latitudes.
In solar-terrestrial terms, magnetograms are graphic representations of magnetic field strength and polarity.
In solar-terrestrial terms, it is the boundary layer between the solar wind and the magnetosphere.
Current created by the separation of solar wind charges on the magnetopause.
The region between the bow shock and the magnetopause of a planet's magnetosphere.
The outer magnetic field of the Earth. The magnetosphere is buffeted by the solar wind. In this region, charged particles motions are controlled by terrestrial magnetic field.
Motion induced in the plasma of the outer magnetosphere by interaction with the solar wind. Magnetospheric convection in turn induces motions in the high-latitude ionosphere through linkage along the direction of the geomagnetic field.
The long magnetic tail of a magnetosphere drawn out by the flow of the solar wind. Earth’s magnetotail is located on its night side. There is observational evidence for traces of Earth's magnetotail as far as 1000 Earth radii downstream.
It is the current from dawn to dusk in the same direction as the ring current on the nightside of the Earth. It begins at approximately 10 Earth radii and extends beyond 200 Earth radii.
It was period when sunspots became exceedingly rare, as noted by solar observers of the time. Prolonged sunspot minimum occurred between 1645 and 1715.
This is a statistical prediction of the highest frequency for HF sky wave propagation. If the prediction is correct, this frequency should be refracted by the ionosphere 50% of the time.
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In fluids terms, it is the average depth of fluid in a stream channel or conduit. It is equal to the cross-sectional area divided by the surface width.
The middle value of an ordered distribution. When there is an even number of values, it is the mean of the two middle values. .
That portion of the radio frequency spectrum from 0.3 to 3 MHz.
In forecasting, (generally) three to seven days in advance.
Gravity waves with periods of dickers of minutes and wavelengths longer some hundreds of kilometers.
It is a prefix of units denoting a factor of 1E6.
An imaginary line on the Earth's surface passing through both geographic poles and through any given point on the planet, also called a line of longitude.
Refers to North-South direction.
The top of the mesosphere, corresponding to the level of minimum temperature in the atmosphere found around 80 kilometers.
Size scale referring to weather systems smaller than synoptic-scale systems but larger than storm-scale systems. Horizontal dimensions generally range from around 80 kilometers to several hundred kilometers.
The intermediary layer of Earth’s atmosphere where the temperature decrease with height and reaches the minimum in the atmosphere. Its approximate height range is 50-85 kilometers.
It is a wavelike structure observed with airglow images with a well defined front, a large horizontal extension, lager amplitude compared with the others structures on the view field, and not necessarily an undulatory structure.
It is a structure like a step function observed by airglow images. It does not have a followed wave train.
A body that enters the Earth's atmosphere and becomes incandescent by friction. A 'shooting star'.
The Meteor Radar is a scientific instrument used for observing meteors and man-made re-entrant objects as they enter the Earth's atmosphere.
A meteorite is a meteoroid that reaches the surface of the Earth without being completely vaporized. This typically occurs at heights of 70 to 110 kilometers above Earth's surface.
Mega electronvolt. A unit of energy used to describe the total energy carried by a particle or photon
That portion of the radio frequency spectrum from 0.3 to 3 MHz.
It is a prefix of units denoting a factor of 1E-6.
A band of decreased ionization around 60 degrees geomagnetic latitude, occurring during night hours. It appears to be related to the auroral oval since an equatorward expansion of the oval results in a decrease in width and movement of the trough towards the equator. Similarly, a poleward movement of the oval sees a corresponding expansion and movement of the trough towards the pole. Possibly the result of plasma rising in this area. The region poleward of the trough is most likely replenished by ionization due to precipitating particles.
Corresponds to the regions between 23° 26' 39'' (tropic) and 66° 33' 39'' (polar circle) latitude degrees on each hemisphere of Earth. These bands of latitude coincide with the temperate zones, which can have fast wind streams and quick change of weather due to the entrance of polar cold air masses.
That geographic region of the Earth that lies between the tropics and the polar circles.
Any scattering produced by spherical particles whose diameters are greater than 1/10 the wavelength of the scattered radiation. This type of scattering causes the clouds to appear white in the sky. Often, hail exhibits in this type of scattering.
A spiral galaxy with a central bulge, of about 1000 pc in extent, a disk component of order 1000 pc in thickness and extending about 15 to 20 kpc from the center, and a roughly spherical halo extending 50000 kpc. In airglow studies, the Milk Way is the disk of this galaxy seen from the inside.
It is a PRefix of units denoting a factor of 1E-3.
It is a pressure unit denoting 1E-3 bar.
A mirror point is a particle reflection point. This is the point when a particle's motion along a field reverses, also known as the point where the projection of the velocity vector in the direction of the geomagnetic field vector is equal to zero.
Sometimes more than one mode of propagation is possible on an HF circuit. There will be small time delays between the different modes which may cause multipath fading. It may be possible to resolve the different modes by careful design of the antennas used.
Mesosphere and lower thermosphere. Region between 60 and 180 km above on the Earth surface.
The path followed by a radio wave between transmitter and receiver. The so-called first propagation mode is the mode with the least number of hops for a circuit. The second propagation mode for a circuit will have one extra hop.
Smallest part of an element or compound that exhibits the properties of the specific element or compound. A molecule is normally considered a group of atoms chemically bonded together.
A model to neutral Earth’ atmosphere.
Density fluctuations of the ionospheric plasma that propagate as wavelike structures with periods of about 6-10 min up to 40-60 min.
Small time delays can occur in radio signals travelling by a single mode (due to irregularities in the ionosphere) or by mixed modes. The superposition of these multiple echoes will degrade the quality of the received signal and cause the signal level to fluctuate.