Research Article

On the nightglow polarisation for space weather exploration

¹ Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) CNRS – UGA, France
² Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France
³ GIPSA-lab, Dept. Images and Signals, UMR CNRS, France
⁴ Tromsø Geophysical Observatory, UiT – the Arctic University of Norway, Tromsø, Norway
⁵ Honorary Astronomer at Royal Observatory of Belgium, Brussels
⁶ Department of Physics and Technology, UiT – the Arctic University of Norway, Tromsø, Norway
⁷ University of Science and Technology Houari Boumediene – USTHB, Faculty of Physics,  
⁸ Univ. Lille, CNRS, UMR 8518 – LOA – Laboratoire d’Optique Atmosphérique, 59000 Lille, France
⁹ Laboratoire Cogitamus, France

^* Corresponding author: leo.bosse@univ-grenoble-alpes.fr

Received: 25 February 2020
Accepted: 30 June 2020

Abstract

We present here observations of the polarisation of four auroral lines in the auroral oval and in the polar cusp using a new ground polarimeter called Petit Cru. Our results confirm the already known polarisation of the red line, and show for the first time that the three other lines observed here (namely 557.7 nm, 391.4 nm and 427.8 nm) are polarised as well up to a few percent. We show that in several circumstances, this polarisation is linked to the local magnetic activity and to the state of the ionosphere through the electron density measured with EISCAT. However, we also show that the contribution of light pollution from nearby cities via scattering can not be ignored and can play an important role in polarisation measurements. This series of observations questions the geophysical origin of the polarisation. It also leaves open its relation to the magnetic field orientation and to the state of both the upper atmosphere and the troposphere.