How Often Do Thermally Excited 630.0 nm Emissions Occur in the Polar Ionosphere?
| Autor: | Magnar Gullikstad Johnsen, Kjellmar Oksavik, Dag Arne Lorentzen, Norah Kaggwa Kwagala |
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| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Physics
010504 meteorology & atmospheric sciences VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430 VDP::Mathematics and natural science: 400::Geosciences: 450::Petroleum geology and petroleum geophysics: 464 01 natural sciences VDP::Mathematics and natural science: 400::Physics: 430 Geophysics Space and Planetary Science Excited state 0103 physical sciences Physics::Space Physics Cusp (anatomy) Polar Atomic physics Ionosphere 010303 astronomy & astrophysics VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Petroleumsgeologi og -geofysikk: 464 0105 earth and related environmental sciences |
| Zdroj: | Journal of Geophysical Research-Space Physics |
| Popis: | Source at: http://doi.org/10.1002/2017JA024744 This paper studies thermally excited emissions in the polar ionosphere derived from European Incoherent Scatter Svalbard radar measurements from the years 2000–2015. The peak occurrence is found around magnetic noon, where the radar observations show cusp-like characteristics. The ionospheric, interplanetary magnetic field and solar wind conditions favor dayside magnetic reconnection as the dominant driving process. The thermal emissions occur 10 times more frequently on the dayside than on the nightside, with an average intensity of 1–5 kR. For typical electron densities in the polar ionosphere (2 × 1011 m−3), we find the peak occurrence rate to occur for extreme electron temperatures (>3000 K), which is consistent with assumptions in literature. However, for extreme electron densities (>5 × 1011 m−3), we can now report on a completely new population of thermal emissions that may occur at much lower electron temperatures (∼2300 K). The empirical atmospheric model (NRLMSISE-00) suggests that the latter population is associated with enhanced neutral atomic oxygen densities. |
| Databáze: | OpenAIRE |
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