Seasonal and solar cycle variations of thermally excited 630.0 nm emissions in the polar ionosphere
| Autor: | Norah Kaggwa Kwagala, Kjellmar Oksavik, Magnar Gullikstad Johnsen, Dag Arne Lorentzen, Karl Magnus Laundal |
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| Přispěvatelé: | Center for Space Science and Engineering Research (Space@VT) |
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
630.0 nm aurora
010504 meteorology & atmospheric sciences Astrophysics::High Energy Astrophysical Phenomena 0nm aurora thermal excitation Atmospheric sciences 01 natural sciences 0103 physical sciences VDP::Matematikk og Naturvitenskap: 400::Geofag: 450 Astrophysics::Solar and Stellar Astrophysics 010303 astronomy & astrophysics Physics::Atmospheric and Oceanic Physics 0105 earth and related environmental sciences ESR Physics VDP::Mathematics and natural science: 400::Geosciences: 450 thermally excited emissions Solar cycle Geophysics Space and Planetary Science polar ionosphere Excited state Physics::Space Physics Polar Astrophysics::Earth and Planetary Astrophysics Ionosphere |
| Zdroj: | Journal of Geophysical Research-Space Physics |
| Popis: | Solar cycle and seasonal variations have been found in the occurrence of strong thermally excited 630.0 nm emissions in the polar ionosphere. Measurements from the European Incoherent Scatter Svalbard Radar have been used to derive the thermal emission intensity. Thermally excited emissions have been found to maximize at solar maximum with peak occurrence rate of similar to 40% compared to similar to 2% at solar minimum. These emissions also have the highest occurrence in equinox and the lowest occurrence rate in summer and winter. There is an equinoctial asymmetry in the occurrence rate which reverses with the solar cycle. This equinoctial asymmetry is attributed to variations of the solar wind-magnetosphere coupling arising from the Russell-McPherron effect. The occurrence rate of thermal excitation emission on the dayside, at Svalbard, has been found to be higher in autumn than spring at solar maximum and the reverse at solar minimum. Enhanced electron temperatures characterize the strong thermal component for solar minimum and winter, whereas enhanced electron densities characterize the thermal component for solar maximum. The results point to solar wind-magnetosphere-ionosphere coupling as the dominant controlling process. China (CRIRP); Finland (SA); Japan (NIPR); Japan (STEL); Norway (NFR); Sweden (VR); United Kingdom (NERC); Norwegian Research Council [223252]; U.S.-Norway Fulbright Foundation The EISCAT data were accessed from https://www.eiscat.se and processed using GUISDAP. EISCAT is an international association supported by research organizations in China (CRIRP), Finland (SA), Japan (NIPR and STEL), Norway (NFR), Sweden (VR), and the United Kingdom (NERC). The interplanetary magnetic field and solar wind data were provided by the NASA OMNIWeb service (https: omniweb.gsfc.nasa.gov/). The NRLMSISE-00 Atmospheric model was accessed from https://ccmc.gsfc.nasa.gov/modelweb/models/nrlmsise00. php. Simulation results have been provided by the Community Coordinated Modeling Center at Goddard Space Flight Center through their public Runs on Request system (http://ccmc.gsfc.nasa.gov). The TIE-GCM Model was developed by the R.G. Roble et al. at the High Altitude Observatory, National Center for Atmospheric Research (HAO NCAR). The TIE-GCM is an open-source community model available at the HAO/NCAR web site. This project has been funded by the Norwegian Research Council under the contract 223252. Kjellmar Oksavik was also grateful for being selected as the 2017-2018 Fulbright Arctic Chair, and his sabbatical at Virginia Tech was sponsored by the U.S.-Norway Fulbright Foundation for Educational Exchange. |
| Databáze: | OpenAIRE |
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