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The auroral ionosphere

Entry in the atmosphere and production of an aurora

Between 500 and 100 kilometers of altitude, i.e. with altitudes of flight of the space shuttle or satellites in low Earth orbit, the precipitated particles will run up against the mixture of gas. Certain collisions are simply elastic, which return part of flow entering towards the other hemisphere along the local line of the magnetic field. Other collisions can heat the ambient electrons: under the effect of strong precipitations, the temperature of the electrons can reach 9000 K to 300 km (...)

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The auroral ionosphere

Entry in the magnetosphere

With regard to the dawns, the Earth has one second important characteristic: it is a magnetized planet. In the absence of solar wind, the shape of the magnetic shield of the Earth would be about that of a dipole, extending in any direction towards the infinite one. The interaction of the geomagnetic shield and the solar wind can be compared with that of a supersonic wind (Mach 8) on a car: a shock wave is formed with before (with 15 terrestrial rays approximately) and forces the particles (...)

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The auroral ionosphere

Solar wind and eruptions

To look at the Sun with various wavelengths makes it possible to see its surface at various altitudes under the chromosphere. To 575 nm for example, we can see his granulations, i.e. surfaces it convective layer.
To imagine what occurs, we can proceed by analogy, while looking at boiling a thick soup in a pan. The hottest soup bubbles go up since the bottom to surface and explode. The flame of the cooker represents the nuclear core of the Sun. Although the scale is not respected, the (...)

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The diurnal ionosphere

Creation of the ionosphere

The Earth has a first important characteristic : it has an atmosphere, whose main components are molecular oxygen and the nitrogen (i.e. two atoms of oxygens or nitrogen dependant between them chemically) between 80 and 105 km. Above 200 km and until around 600 km, atomic oxygen becomes the component majority one, the minority ones being hydrogen, helium, argon and the atomic nitrogen. The typical total concentrations are a million billion particles per cubic meter to 400 km and hundred (...)

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The diurnal ionosphere

Solar spectrum

The solar spectrum extends on a broad range wavelengths, since the tenth of nanometer (nm) until the meter. In the visible one - with 390 to 760 Nm, it radiates with a maximum around 450 Nm, i.e. in blue. Let us not mistake! The Sun is not blue for as much! The mixture of all the colors, the absorption of the light by the terrestrial atmosphere, as well as the sensitivity of our eyes show it to us yellow (and red with sleeping). This part of the spectrum was studied since the 19th century. (...)

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Institut de Planétologie et d'Astrophysique de Grenoble (IPAG)