Concept
Aurora
Related concepts (51)
Dynamo theory
In physics, the dynamo theory proposes a mechanism by which a celestial body such as Earth or a star generates a magnetic field. The dynamo theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time scales. A dynamo is thought to be the source of the Earth's magnetic field and the magnetic fields of Mercury and the Jovian planets.
Birkeland current
A Birkeland current (also known as field-aligned current) is a set of electrical currents that flow along geomagnetic field lines connecting the Earth's magnetosphere to the Earth's high latitude ionosphere. In the Earth's magnetosphere, the currents are driven by the solar wind and interplanetary magnetic field and by bulk motions of plasma through the magnetosphere (convection indirectly driven by the interplanetary environment). The strength of the Birkeland currents changes with activity in the magnetosphere (e.
South magnetic pole
The south magnetic pole, also known as the magnetic south pole, is the point on Earth's Southern Hemisphere where the geomagnetic field lines are directed perpendicular to the nominal surface. The Geomagnetic South Pole, a related point, is the south pole of an ideal dipole model of the Earth's magnetic field that most closely fits the Earth's actual magnetic field. For historical reasons, the "end" of a freely hanging magnet that points (roughly) north is itself called the "north pole" of the magnet, and the other end, pointing south, is called the magnet's "south pole".
Halo (optical phenomenon)
A halo () is an optical phenomenon produced by light (typically from the Sun or Moon) interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky. Many of these appear near the Sun or Moon, but others occur elsewhere or even in the opposite part of the sky. Among the best known halo types are the circular halo (properly called the 22° halo), light pillars, and sun dogs, but many others occur; some are fairly common while others are extremely rare.
Geomagnetically induced current
Geomagnetically induced currents (GIC) are electrical currents induced at the Earth's surface by rapid changes in the geomagnetic field caused by space weather events. GICs can affect the normal operation of long electrical conductor systems such as electric transmission grids and buried pipelines. The geomagnetic disturbances which induce GICs include geomagnetic storms and substorms where the most severe disturbances occur at high geomagnetic latitudes. The Earth's magnetic field varies over a wide range of timescales.
Heliospheric current sheet
The heliospheric current sheet, or interplanetary current sheet, is a surface separating regions of the heliosphere where the interplanetary magnetic field points toward and away from the Sun. A small electrical current with a current density of about 10−10 A/m2 flows within this surface, forming a current sheet confined to this surface. The shape of the current sheet results from the influence of the Sun's rotating magnetic field on the plasma in the interplanetary medium.
Pitch angle (particle motion)
The pitch angle of a charged particle is the angle between the particle's velocity vector and the local magnetic field. This is a common measurement and topic when studying the magnetosphere, magnetic mirrors, biconic cusps and polywells. See Aurora and Ring current It is customary to discuss the direction a particle is heading by its pitch angle. A pitch angle of 0 degrees is a particle whose parallel motion is perfectly along the local magnetic field.
Plasma parameters
Plasma parameters define various characteristics of a plasma, an electrically conductive collection of charged particles that responds collectively to electromagnetic forces. Plasma typically takes the form of neutral gas-like clouds or charged ion beams, but may also include dust and grains. The behaviour of such particle systems can be studied statistically. All quantities are in Gaussian (cgs) units except energy and temperature which are in electronvolts.
Heliophysics
Heliophysics (from the prefix "helio", from Attic Greek hḗlios, meaning Sun, and the noun "physics": the science of matter and energy and their interactions) is the physics of the Sun and its connection with the Solar System. NASA defines heliophysics as "(1) the comprehensive new term for the science of the Sun - Solar System Connection, (2) the exploration, discovery, and understanding of Earth's space environment, and (3) the system science that unites all of the linked phenomena in the region of the cosmos influenced by a star like our Sun.
Terrella
A terrella (Latin for "little earth") is a small magnetised model ball representing the Earth, that is thought to have been invented by the English physician William Gilbert while investigating magnetism, and further developed 300 years later by the Norwegian scientist and explorer Kristian Birkeland, while investigating the aurora. Terrellas have been used until the late 20th century to attempt to simulate the Earth's magnetosphere, but have now been replaced by computer simulations.