Magnetism

Dayside and Polar Cap Aurora (Astrophysics and Space Science by Per Even Sandholt, H.C. Carlson, A. Egeland

By Per Even Sandholt, H.C. Carlson, A. Egeland

The auroral emissions within the higher surroundings of the polar areas of the Earth are proof of the seize of full of life debris from the sunlight, streaming through the Earth because the sun wind. those auroral emissions, then, are a window to outer area, and will offer us with precious information regarding electrodynamic coupling approaches among the sun wind and the Earth's ionosphere and higher surroundings. learning the physics of those phenomena extends our knowing of our plasma universe. Ground-based remote-sensing ideas, capable of computer screen consistently the differences within the signatures of aurorae, together with in-situ satellite tv for pc and rocket measurements, promise to strengthen dramatically our knowing of the actual procedures occurring on the interface of the atmospheres of the Earth and the sunlight. interpreting their complexity brings us toward trustworthy prediction of conversation environments, in particular at excessive latitudes. This figuring out, in flip, might help us unravel difficulties of conversation and navigation throughout polar areas.

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Extra resources for Dayside and Polar Cap Aurora (Astrophysics and Space Science Library)

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In IMF clock angle regime III (south) the aurora appears in the form of the type 1 emis­ sion band with equatorward boundary intensifications (EBIs), typically located within 70°– 75° MLAT. The polar cap is void of auroral arcs. When the IMF is in clock angle regime II (45° –135°; IMF orientation) we often observe the presence of both type 1 and 2 cusp auroral forms. This configuration is referred to as the bifurcated cusp aurora. The southernmost form is characterized by a series of EBIs, followed by PMAFs.

The neutral pressure is that pressure which supports the net weight of all the gas above it. The difference between pressure level and geo-potential altitude is small at E-region heights, but by an altitude of 300 km in the F-region can be 15 km for a 1000 K difference in exospheric temperature. 1 keV) electrons, such as from the magnetosheath. F-region emissions are typical of dayside cusp au­ rora and polar cap aurora, particularly sun-aligned arcs. E-region emissions are, in contrast, characteristic of hard, that is, more energetic (~1– 10 keV) electrons.

1 Altitude Profiles Particles penetrate in the atmosphere to a depth dependent on the particle energy. Even for a stream of single energy (mono-energetic) particles, this penetration is not a single height. The collision process involves random-walk energy loss, so each identical precipitating particle can stop at a different altitude within a range of altitudes. The altitude of greatest particle absorption is called the altitude of unity optical depth. Most particles are stopped within a and and ~60 km for atomic oxygen) neutral scale height (at F-region heights ~30 km for of the unity optical depth altitude.

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