Measurement of the polarisation in the auroral N2+ 427.8 nm band

• Published in: Journal of Space Weather and Space Climate
• Main Authors: Barthelemy, Mathieu, Lamy, Hervé, Vialatte, Anne, Johnsen, Magnar Gullikstad, Cessateur, Gaël, Zaourar, Naïma
• Other Authors: Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Royal Belgian Inst Space Aeron, Ave Circulaire 3, B-1180 Brussels, Belgium, Tromsø Geophysical Observatory (TGO), The Arctic University of Norway Tromsø, Norway (UiT), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: polarisation; aurora; space weather-ionosphere-instrumentation; [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]; Skibotn
• Online Access: https://hal.science/hal-02924302; https://hal.science/hal-02924302/document; https://hal.science/hal-02924302/file/swsc180018.pdf; https://doi.org/10.1051/swsc/2019024

International audience In this paper, we provide for the first time polarisation measurements of the N+2 band at 427.8 nm performed with Premier Cru, a dedicated spectropolarimeter to investigate the polarisation of auroral emission lines between 400 and 700 nm. Details about the instrument, the observing conditions and the data analysis procedure are provided. Results obtained during three nights in March 2017 in Skibotn, Norway, indicate that the auroral blue line is polarised with a degree of linear polarisation of a few %. Due to weak Signal-to-Noise Ratios (SNR), these measurements still need to be taken with caution since none of the individual data set has a detection with a 3σ confidence level. However, results integrated over the entire observing period each night do show a 3σ detection but due to the long integration period, the origin of this polarisation cannot be linked to a specific type of aurora (diffuse vs structured arc) or specific ionospheric or geomagnetic conditions. These observations need to be confirmed with an improved design to increase the SNR and decrease the exposure time. When available, these improved measurements of the blue line polarisation will be important to better understand the physics of auroral processes at altitudes below 100 km where the N2+ emission occurs and possibly for space weather applications if the polarisation varies with ionospheric/geomagnetic conditions.