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Author |
Barthelemy M, Lystrup M B, Menager H, Miller S, Lilensten J, |
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Title |
First detection of polarization in jovian auroral H+3 emissions |
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Journal Article |
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Year |
2011 |
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A&A |
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Volume |
530 |
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Keywords |
polarization / molecular data / planets and satellites: aurorae / planets and satellites: individual: Jupiter |
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1026 |
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1895-6572 |
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yes |
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Serial |
220 |
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Title |
Polarisation in the auroral red line during coordinated EISCAT Svalbard Radar/optical experiments |
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Journal Article |
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Year |
2011 |
Publication |
Ann. Geophys. |
Abbreviated Journal |
ANGEO |
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Volume |
29 |
Issue |
6 |
Pages |
1101-1112 |
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Abstract |
The polarisation of the atomic oxygen red line in the Earth's thermosphere is observed in different configurations with respect to the magnetic field line at high latitude during several coordinated Incoherent Scatter radar/optical experiment campaigns. When pointing northward with a line-of-sight nearly perpendicular to the magnetic field, we show that, as expected, the polarisation is due to precipitated electrons with characteristic energies of a few hundreds of electron Volts. When pointing toward the zenith or southward with a line-of-sight more parallel to the magnetic field, we show that the polarisation practically disappears. This confirms experimentally the predictions deduced from the recent discovery of the red line polarisation. We show that the polarisation direction is parallel to the magnetic field line during geomagnetic activity intensification and that these results are in agreement with theoretical work. |
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1026 |
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Copernicus Publications |
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ISSN |
1432-0576 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
6063 |
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Title |
Ionization processes in the atmosphere of Titan
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Journal Article |
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Year |
2009 |
Publication |
A&A |
Abbreviated Journal |
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Volume |
506 |
Issue |
2 |
Pages |
955 -964 |
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Keywords |
planets and satellites: individual: Titan -- atmospheric effects -- Sun: UV radiation -- space vehicles: instruments -- methods: numerical |
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Abstract |
Context. The Cassini probe regularly passes in the vicinity of Titan, revealing new insights into particle precipitation thanks to the electron and proton spectrometer. Moreover, the Huygens probe has revealed an ionized layer at 65 km induced by cosmic rays. The impact of these different particles on the chemistry of Titan is probably very strong.
Aims. In this article, we compute the whole ionization in the atmosphere of Titan: from the cosmic rays near the ground to the EUV in the upper atmosphere. The meteoritic layer is not taken into account.
Methods. We used the transTitan model to compute the electron and EUV impact, and the planetocosmics code to compute the influence of protons and oxygen ions. We coupled the two models to study the influence of the secondary electrons obtained by planetocosmics through the transTitan code. The resulting model improves the accuracy of the calculation through the transport of electrons in the atmosphere.
Results. The whole ionization is computed and studied in details. During the day, the cosmic ray ionization peak is as strong as the UV-EUV one. Electrons and protons are very important depending the precipitation conditions. Protons can create a layer at 500 km, while electrons tend to ionize near 800 km. The oxygen ion impact is near 900 km. The results shows few differences to precedent models for the nightside T5 fly-by of Cassini, and can highlight the sources of the different ion layers detected by radio measurements.
Conclusions. The new model successfully computes the ion production in the atmosphere of Titan. For the first time, a full electron and ion profile has been computed from 0 to 1600 km, which compares qualitatively with measurements. This result can be used by chemical models. |
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1026 |
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ISSN |
0004-6361 |
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yes |
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Serial |
1973 |
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Title |
The auroral red line polarisation: modelling and measurements
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Journal Article |
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Year |
2015 |
Publication |
Journal of Space Weather and Space Climate |
Abbreviated Journal |
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Volume |
5 |
Issue |
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Pages |
A26-A26 |
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Abstract |
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 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 localized 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 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\% $\pm$ 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. |
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1026 |
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Publisher |
EDP Sciences |
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ISSN |
2115-7251 |
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yes |
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Call Number |
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Serial |
6237 |
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Author |
J. Lilensten, M. Barthélemy, G. Besson, H. Lamy, M.G. Johnsen, J. Moen |
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Title |
The thermospheric auroral red line Angle of Linear Polarisation |
Type |
Journal Article |
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Year |
2016 |
Publication |
Journal of geophysical research-space physics |
Abbreviated Journal |
J. Geophys. Res. |
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Volume |
121 |
Issue |
7 |
Pages |
2016JA022941 |
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Keywords |
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Abstract |
The auroral red line at 630 nm is linearly polarized. Up to now, only its Degree of LinearPolarization had been studied. In this article, we examine for the first time the Angle of Linear Polarization(AoLP) and we compare the measurements to the apparent angle of the magnetic field at the location ofthe red line emission. We show that the AoLP is a tracer of the magnetic field configuration. This opens newperspectives, both in the frame of space weather and in the field of planetology. |
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1026 |
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ISSN |
0148-0227 |
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Approved |
yes |
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Call Number |
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Serial |
6541 |
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Author |
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Title |
The thermospheric auroral red line Angle of Linear Polarization |
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Journal |
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Year |
2016 |
Publication |
Journal of Geophysical Research: Space Physics |
Abbreviated Journal |
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Volume |
121 |
Issue |
7 |
Pages |
7125-7134 |
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Keywords |
ionosphere polarization |
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Abstract |
The auroral red line at 630 nm is linearly polarized. Up to now, only its Degree of Linear Polarization had been studied. In this article, we examine for the first time the Angle of Linear Polarization (AoLP) and we compare the measurements to the apparent angle of the magnetic field at the location of the red line emission. We show that the AoLP is a tracer of the magnetic field configuration. This opens new perspectives, both in the frame of space weather and in the field of planetology. |
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Programme |
1026 |
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ISSN |
2169-9402 |
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yes |
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Call Number |
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Serial |
7644 |
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Author |
Hanane Marif, Jean Lilensten |
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Title |
Suprathermal electron moments in the ionosphere |
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Journal |
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Year |
2020 |
Publication |
Journal of Space Weather and Space Climate |
Abbreviated Journal |
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Volume |
10 |
Issue |
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Pages |
22 |
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Programme |
1026 |
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Thesis |
Bachelor's thesis |
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ISSN |
2115-7251 |
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yes |
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Serial |
7679 |
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Title |
On the nightglow polarisation for space weather exploration |
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Journal |
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2020 |
Publication |
Journal of Space Weather and Space Climate |
Abbreviated Journal |
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Volume |
10 |
Issue |
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Pages |
35 |
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Keywords |
polarisation / aurora |
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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. |
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1026 |
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ISSN |
2115-7251 |
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Approved |
yes |
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Call Number |
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Serial |
7796 |
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Author |
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Title |
The thermospheric auroral red line polarization: confirmation of detection and first quantitative analysis |
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Journal |
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Year |
2013 |
Publication |
Journal of Space Weather and Space Climate |
Abbreviated Journal |
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Volume |
3 |
Issue |
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Pages |
A01 |
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Programme |
1026 |
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Thesis |
Bachelor's thesis |
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2115-7251 |
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yes |
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Call Number |
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Serial |
7962 |
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Title |
Measurement of the polarisation in the auroral N2+ 427.8 nm band |
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Journal |
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Year |
2019 |
Publication |
Journal of Space Weather and Space Climate |
Abbreviated Journal |
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Volume |
9 |
Issue |
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Pages |
A26 |
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Abstract |
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 3? confidence level. However, results integrated over the entire observing period each night do show a 3? 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. |
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1026 |
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2115-7251 |
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Approved |
yes |
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Call Number |
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Serial |
8172 |
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