The auroral red line polarisation: modelling and measurements
In this work, we model the polarisation of the auroral red line using the electron impact theory developed by Bommier et al. (2011). This theory enables the computation of the distribution of the Degree of Linear Polarisation (DoLP) as a function of height if the flux of precipitated electrons is pr...
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ftdoajarticles:oai:doaj.org/article:c520a657c1a041ff9cc5734995a8709c 2023-05-15T18:29:51+02:00 The auroral red line polarisation: modelling and measurements Lilensten Jean Bommier Véronique Barthélemy Mathieu Lamy Hervé Bernard David Moen Joran Idar Johnsen Magnar Gullikstad Løvhaug Unni Pia Pitout Frédéric 2015-01-01T00:00:00Z https://doi.org/10.1051/swsc/2015027 https://doaj.org/article/c520a657c1a041ff9cc5734995a8709c EN eng EDP Sciences http://dx.doi.org/10.1051/swsc/2015027 https://doaj.org/toc/2115-7251 2115-7251 doi:10.1051/swsc/2015027 https://doaj.org/article/c520a657c1a041ff9cc5734995a8709c Journal of Space Weather and Space Climate, Vol 5, p A26 (2015) Thermosphere Auroral emissions Polarisation Meteorology. Climatology QC851-999 article 2015 ftdoajarticles https://doi.org/10.1051/swsc/2015027 2022-12-31T04:11:11Z In this work, we model the polarisation of the auroral red line using the electron impact theory developed by Bommier et al. (2011). This theory enables the computation of the distribution of the Degree of Linear Polarisation (DoLP) as a function of height if the flux of precipitated electrons is provided as input. An electron transport code is used to infer the stationary electron flux at each altitude in the ionosphere as a function of energy and pitch angle. Using adequate cross-sections, the integral of this electron flux over energy and pitch angle provides an anisotropy parameter from which the theoretical local DoLP can be computed at each altitude. The modelled DoLP is then derived by integrating along the line-of-sight. Depending on the integration length, the modelled DoLP ranges between 0.6% for a very long integration length and 1.8% for a very short integration length localised around an altitude of 210 km. A parametric study is performed to check how the characteristics of the local DoLP (maximum value, altitude of the maximum, integrated height profile) vary. It is found that the polarisation is highly sensitive to the scattering function of the electrons, to the electron precipitation and to the geomagnetic activity. We compare these values to measured ones obtained during an observational campaign performed in February 2012 from Svalbard. The measured DoLP during the campaign was 1.9% ± 0.1%. The comparison between this value and the theoretical one is discussed. Discrepancies may be due to the poor constraint of the input parameters (thermosphere and ionosphere), to the fact that only electron precipitation is considered in this approach (and not proton precipitation for instance) and to the difficulty in constraining the exact width of the emission layer in the thermosphere. Article in Journal/Newspaper Svalbard Directory of Open Access Journals: DOAJ Articles Svalbard Journal of Space Weather and Space Climate 5 A26 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Thermosphere Auroral emissions Polarisation Meteorology. Climatology QC851-999 |
spellingShingle |
Thermosphere Auroral emissions Polarisation Meteorology. Climatology QC851-999 Lilensten Jean Bommier Véronique Barthélemy Mathieu Lamy Hervé Bernard David Moen Joran Idar Johnsen Magnar Gullikstad Løvhaug Unni Pia Pitout Frédéric The auroral red line polarisation: modelling and measurements |
topic_facet |
Thermosphere Auroral emissions Polarisation Meteorology. Climatology QC851-999 |
description |
In this work, we model the polarisation of the auroral red line using the electron impact theory developed by Bommier et al. (2011). This theory enables the computation of the distribution of the Degree of Linear Polarisation (DoLP) as a function of height if the flux of precipitated electrons is provided as input. An electron transport code is used to infer the stationary electron flux at each altitude in the ionosphere as a function of energy and pitch angle. Using adequate cross-sections, the integral of this electron flux over energy and pitch angle provides an anisotropy parameter from which the theoretical local DoLP can be computed at each altitude. The modelled DoLP is then derived by integrating along the line-of-sight. Depending on the integration length, the modelled DoLP ranges between 0.6% for a very long integration length and 1.8% for a very short integration length localised around an altitude of 210 km. A parametric study is performed to check how the characteristics of the local DoLP (maximum value, altitude of the maximum, integrated height profile) vary. It is found that the polarisation is highly sensitive to the scattering function of the electrons, to the electron precipitation and to the geomagnetic activity. We compare these values to measured ones obtained during an observational campaign performed in February 2012 from Svalbard. The measured DoLP during the campaign was 1.9% ± 0.1%. The comparison between this value and the theoretical one is discussed. Discrepancies may be due to the poor constraint of the input parameters (thermosphere and ionosphere), to the fact that only electron precipitation is considered in this approach (and not proton precipitation for instance) and to the difficulty in constraining the exact width of the emission layer in the thermosphere. |
format |
Article in Journal/Newspaper |
author |
Lilensten Jean Bommier Véronique Barthélemy Mathieu Lamy Hervé Bernard David Moen Joran Idar Johnsen Magnar Gullikstad Løvhaug Unni Pia Pitout Frédéric |
author_facet |
Lilensten Jean Bommier Véronique Barthélemy Mathieu Lamy Hervé Bernard David Moen Joran Idar Johnsen Magnar Gullikstad Løvhaug Unni Pia Pitout Frédéric |
author_sort |
Lilensten Jean |
title |
The auroral red line polarisation: modelling and measurements |
title_short |
The auroral red line polarisation: modelling and measurements |
title_full |
The auroral red line polarisation: modelling and measurements |
title_fullStr |
The auroral red line polarisation: modelling and measurements |
title_full_unstemmed |
The auroral red line polarisation: modelling and measurements |
title_sort |
auroral red line polarisation: modelling and measurements |
publisher |
EDP Sciences |
publishDate |
2015 |
url |
https://doi.org/10.1051/swsc/2015027 https://doaj.org/article/c520a657c1a041ff9cc5734995a8709c |
geographic |
Svalbard |
geographic_facet |
Svalbard |
genre |
Svalbard |
genre_facet |
Svalbard |
op_source |
Journal of Space Weather and Space Climate, Vol 5, p A26 (2015) |
op_relation |
http://dx.doi.org/10.1051/swsc/2015027 https://doaj.org/toc/2115-7251 2115-7251 doi:10.1051/swsc/2015027 https://doaj.org/article/c520a657c1a041ff9cc5734995a8709c |
op_doi |
https://doi.org/10.1051/swsc/2015027 |
container_title |
Journal of Space Weather and Space Climate |
container_volume |
5 |
container_start_page |
A26 |
_version_ |
1766213272014422016 |