Observations and theory of the formation of stable auroral red arcs

摘要: A population of protons with energy some tens keV, called the ring current, is found near equatorial region magnetosphere at several earth radii. During main phase geomagnetic storms current shifts toward lower L values into plasmapause, which characterized by steep gradients in plasma density. This interaction together an anisotropic pitch angle distribution leads to instability and growth ion cyclotron wave turbulence. As dissipated ambient electron gas Landau damping, plasmapause temperature raised a few volts, substantial gradient created respect ionosphere. The transferred ionosphere scattering low collision frequency heat conduction collision-dominated regime raises ionospheric thousand degrees. Therefore appreciable number electrons high-energy tail Maxwellian distribution, i.e., greater than 2 eV, exist F about 400 km, where atomic oxygen dominant neutral constituent. Two eV threshold for excitation atoms metastable ¹D level, these O(¹D) emit 6300-A radiation, signature stable auroral red (SAR) arcs. Although input rate required produce temperatures sufficient cause average SAR arcs less 0.1 erg cm−2 s−1, radiated line only 0.003 s−1. Thus arc optical manifestation slow release from during storm. Energetically it small comparison high-latitude processes.