Aurora (astronomy) in the context of "Electron precipitation"

Hannes Olof Gösta Alfvén (Swedish: [alˈveːn]; 30 May 1908 – 2 April 1995) was a Swedish electrical engineer, plasma physicist and winner of the 1970 Nobel Prize in Physics for his work on magnetohydrodynamics (MHD). He described the class of MHD waves now known as Alfvén waves. He was originally trained as an electrical power engineer and later moved to research and teaching in the fields of plasma physics and electrical engineering. Alfvén made many contributions to plasma physics, including theories describing the behavior of aurorae, the Van Allen radiation belts, the effect of magnetic storms on the Earth's magnetic field, the terrestrial magnetosphere, and the dynamics of plasmas in the Milky Way galaxy.

Northern Norway (Bokmål: Nord-Norge, Urban East Norwegian: [ˈnûːrˌnɔrɡə], Nynorsk: Nord-Noreg; Northern Sami: Davvi-Norga) is a geographical region of Norway, consisting of the three northernmost counties Nordland, Troms and Finnmark, in total about 35% of the Norwegian mainland. Some of the largest towns in Northern Norway (from south to north) are Mo i Rana, Bodø, Narvik, Harstad, Tromsø and Alta. Northern Norway is often described as the land of the midnight sun and the land of the northern lights. Farther north, halfway to the North Pole, is the Arctic archipelago of Svalbard, traditionally not regarded as part of Northern Norway.

The region is multi-cultural, housing not just Norwegians but also the indigenous Sami people, Norwegian Finns (known as Kvens, distinct from the "Forest Finns" of Southern Norway) and Russian populations (mostly in Kirkenes). The Norwegian language dominates in most of the area; Sami speakers are mainly found inland and in some of the fjord areas of Nordland, Troms and particularly Finnmark – though ethnic Sámi who do not speak the language are found more or less everywhere in the region. Finnish is spoken in only a few communities in the east of Finnmark.

Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission began in February 2007 as a constellation of five NASA satellites (THEMIS-A through THEMIS-E) to study energy releases from Earth's magnetosphere known as substorms, magnetic phenomena that intensify auroras near Earth's poles. The name of the mission is an acronym alluding to the Titan Themis.

Three of the satellites orbit the Earth within the magnetosphere, while two have been moved into orbit around the Moon. Those two were renamed ARTEMIS for Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun. THEMIS-B became ARTEMIS-P1 and THEMIS-C became ARTEMIS-P2. ARTEMIS-P1 and -P2 together comprise the THEMIS–ARTEMIS mission.

The magnetosphere of Jupiter is the cavity created in the solar wind by Jupiter's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosphere is the largest and most powerful of any planetary magnetosphere in the Solar System, and by volume the largest known continuous structure in the Solar System after the heliosphere. Wider and flatter than the Earth's magnetosphere, Jupiter's is stronger by an order of magnitude, while its magnetic moment is roughly 18,000 times larger. The existence of Jupiter's magnetic field was first inferred from observations of radio emissions at the end of the 1950s and was directly observed by the Pioneer 10 spacecraft in 1973.

Jupiter's internal magnetic field is generated by electrical currents in the planet's outer core, which is theorized to be composed of liquid metallic hydrogen. Volcanic eruptions on Jupiter's moon Io eject large amounts of sulfur dioxide gas into space, forming a large torus around the planet. Jupiter's magnetic field forces the torus to rotate with the same angular velocity and direction as the planet. The torus in turn loads the magnetic field with plasma, in the process stretching it into a pancake-like structure called a magnetodisk. In effect, Jupiter's magnetosphere is internally driven, shaped primarily by Io's plasma and its own rotation, rather than by the solar wind as at Earth's magnetosphere. Strong currents in the magnetosphere generate permanent aurorae around the planet's poles and intense variable radio emissions, which means that Jupiter can be thought of as a very weak radio pulsar. Jupiter's aurorae have been observed in almost all parts of the electromagnetic spectrum, including infrared, visible, ultraviolet and soft X-rays.