| Home | [21–30] << 31 32 33 34 35 36 37 38 39 40 >> [41–50] |
|
| Records | |||||
|---|---|---|---|---|---|
| Author | Barthelemy M, Lystrup M B, Menager H, Miller S, Lilensten J, | ||||
| Title | First detection of polarization in jovian auroral H+3 emissions | Type | Journal Article | ||
| Year | 2011 | Publication | A&A | Abbreviated Journal | |
| Volume | 530 | Issue | Pages | ||
| Keywords | polarization / molecular data / planets and satellites: aurorae / planets and satellites: individual: Jupiter | ||||
| Abstract | Context. The recent measurement of linear polarization in the Earth thermospheric oxygen red line shows that it can be a useful observable quantity to characterise the upper atmospheres conditions. Therefore, polarimetry measurements are extended to other planets. Considering that FUV emissions are not observable from the ground, the best candidates for Jupiter auroral emissions are
H3+ infrared emissions around 4µm. This ion is created after a chemical process in the jovian upper atmosphere. Then, the anisotropy responsible of the polarization cannot be the particle impact as in the Earth case Aims. The goal of this study is to detect some potential linear polarisation in the H3+ emissions of the jovian auroral oval. Methods. Measurements of the H3+ emissions from the south auroral oval have been performed at the UKIRT during the beginning of August 2008, using the UIST-IRPOL spectro-polarimeter. The slit have been positioned perpendicularly to the jovian rotation axis. Data were processed by dividing the slit in 24 bins. Stokes parameters u and q, polarization degree and direction are extracted for each bin and debiased. Results. Polarization up to 8% is detected. More than 7 bins show polarization with confidence level above 3σ. The better signal to noise ratio appears in the main auroral oval but no clear link appears between the polarization degrees and angles and the local known anisotropies. The angles are a bit higher than 90° in the West part of the oval and mostly around 90° for the East part. Conclusions. This study shows that polarization is detectable in the jovian infrared auroras. However, it is impossible to link it with electric or magnetic field for the moment due to the lack of theoretical work and laboratory experiments concerning the polarization of H3+. |
||||
Programme  |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 1895-6572 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 220 | |||
| Permanent link to this record | |||||
| Author | Barthélémy, M.; Lilensten, J.; Pitout, F.; Simon Wedlund, C.; Thissen, R.; Lorentzen, D.; Sigernes, F.; Moen, J.; Gronoff, G.; McCrea, I.; Rothkael, H.; Ménager, H.; Aruliah, A. | ||||
| Title | Polarisation in the auroral red line during coordinated EISCAT Svalbard Radar/optical experiments | Type | Journal Article | ||
| Year | 2011 | Publication | Ann. Geophys. | Abbreviated Journal | ANGEO |
| Volume | 29 | Issue | 6 | Pages | 1101-1112 |
| Keywords | |||||
| 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. | ||||
| Programme |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Copernicus Publications | Place of Publication | Editor | ||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 1432-0576 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | IPEV @ Thierry.Lemaire @ | Serial | 6063 | ||
| Permanent link to this record | |||||
| Author | Gronoff G, Lilensten J, Desorgher L, Flückiger E, | ||||
| Title | Ionization processes in the atmosphere of Titan | Type | Journal Article | ||
| Year | 2009 | Publication | A&A | Abbreviated Journal | |
| Volume | 506 | Issue | 2 | Pages | 955 -964 |
| Keywords | planets and satellites: individual: Titan -- atmospheric effects -- Sun: UV radiation -- space vehicles: instruments -- methods: numerical | ||||
| 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. |
||||
| Programme |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 0004-6361 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 1973 | |||
| Permanent link to this record | |||||
| Author | Lilensten Jean, Bommier Véronique, Barthélemy Mathieu, Lamy Hervé, Bernard David, Moen Joran Idar, Johnsen Magnar Gullikstad, Løvhaug Unni Pia, Pitout Frédéric, | ||||
| Title | The auroral red line polarisation: modelling and measurements | Type | Journal Article | ||
| Year | 2015 | Publication | Journal of Space Weather and Space Climate | Abbreviated Journal | |
| Volume | 5 | Issue | Pages | A26-A26 | |
| Keywords | |||||
| 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. |
||||
| Programme |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | EDP Sciences | Place of Publication | Editor | ||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 2115-7251 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 6237 | |||
| Permanent link to this record | |||||
| Author | J. Lilensten, M. Barthélemy, G. Besson, H. Lamy, M.G. Johnsen, J. Moen | ||||
| Title | The thermospheric auroral red line Angle of Linear Polarisation | Type | Journal Article | ||
| Year | 2016 | Publication | Journal of geophysical research-space physics | Abbreviated Journal | J. Geophys. Res. |
| Volume | 121 | Issue | 7 | Pages | 2016JA022941 |
| Keywords | |||||
| 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. | ||||
| Programme |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 0148-0227 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 6541 | |||
| Permanent link to this record | |||||
| Author | Jean Lilensten, Mathieu Barthélemy, Gérard Besson, Hervé Lamy, Magnar G. Johnsen, Jøran Moen | ||||
| Title | The thermospheric auroral red line Angle of Linear Polarization | Type | Journal | ||
| Year | 2016 | Publication | Journal of Geophysical Research: Space Physics | Abbreviated Journal | |
| Volume | 121 | Issue | 7 | Pages | 7125-7134 |
| Keywords | ionosphere polarization | ||||
| 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. | ||||
| Programme |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 2169-9402 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 7644 | |||
| Permanent link to this record | |||||
| Author | Hanane Marif, Jean Lilensten | ||||
| Title | Suprathermal electron moments in the ionosphere | Type | Journal | ||
| Year | 2020 | Publication | Journal of Space Weather and Space Climate | Abbreviated Journal | |
| Volume | 10 | Issue | Pages | 22 | |
| Keywords | |||||
| Abstract | The ionospheric electron population is divided into two groups. The ambient electrons are thermalized. Their energy is usually smaller than one electron volt. Their densities and temperatures are the usual ones measured by incoherent scatter radars, or modeled by international codes such as International Reference Ionosphere (IRI). There is however a second population called the suprathermal electrons. This one is either due to photoionization or to electron impact between the thermosphere and the precipitation in the high latitude zone. In the frame of space weather, it may be the source of scintillations, plasma bulks and other physical phenomena. The suprathermal electron population can only indirectly be measured through the plasmaline and had never been modeled. Its modeling requires the computation of the electron stationary flux by solving the Boltzmann transport equation. This flux is multiplied by various powers of the velocity v and integrated to obtain the different order moments. By integrating f over v0dv, one deduces the suprathermal electron density. An integration of v1fdv allows the computation of their mean velocity. Higher moments give access to their temperature and finally to their heat flux. In this work, we demonstrate for the first time the full and rigorous calculation of the ionospheric electron moments up to three. As two case studies, we focus on high latitude in the auroral oval and low magnetic latitude over Algiers for different solar and geophysical conditions. We compare the suprathermal densities and temperatures to the thermal electron parameters. Our results highlight that – as expected – the suprathermal density is small compared to the thermal one. Although it is close to 3 × 103 m−3 at 180 km during the day, it drops drastically at night, to hardly reach 3 m−3. Contrarily to the density, the velocity is about 10 times more important during the nighttime when precipitation occurs than during the daytime under the electromagnetic solar flux. At 400 km, it varies during the day between 700,000 m s−1 (active solar conditions) and 900,000 m s−1 (quiet Sun). At night, the velocity varies between 3 × 106 m s−1 (low mean energy precipitation) and 3 × 107 m s−1 (high mean energy precipitation) at 400 km. The suprathermal temperature increases as the solar activity decreases or as the mean energy of the electron precipitation increases. It may reach values close to 3 × 108 K. The heat flux may be fully oriented downward or experiences a reversal with some flux going up depending on the forcing. | ||||
| Programme |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | Bachelor's thesis | |||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 2115-7251 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 7679 | |||
| Permanent link to this record | |||||
| Author | Léo Bosse, Jean Lilensten, Nicolas Gillet, Sylvain Rochat, Alain Delboulbé, Stephane Curaba, Alain Roux, Yves Magnard, Magnar G. Johnsen, Unni-Pia Løvhaug, Pierre-Olivier Amblard, Nicolas Le Bihan, Maxime Nabon, Hanane Marif, Frédérique Auriol, Camille Noûs | ||||
| Title | On the nightglow polarisation for space weather exploration | Type | Journal | ||
| Year | 2020 | Publication | Journal of Space Weather and Space Climate | Abbreviated Journal | |
| Volume | 10 | Issue | Pages | 35 | |
| Keywords | polarisation / aurora | ||||
| 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. | ||||
| Programme |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 2115-7251 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 7796 | |||
| Permanent link to this record | |||||
| Author | Jean Lilensten, Mathieu Barthélémy, Pierre-Olivier Amblard, Hervé Lamy, Cyril Simon Wedlund, Véronique Bommier, Joran Moen, Hanna Rothkaehl, Julien Eymard, Jocelyn Ribot | ||||
| Title | The thermospheric auroral red line polarization: confirmation of detection and first quantitative analysis | Type | Journal | ||
| Year | 2013 | Publication | Journal of Space Weather and Space Climate | Abbreviated Journal | |
| Volume | 3 | Issue | Pages | A01 | |
| Keywords | |||||
| Abstract | The thermospheric atomic oxygen red line is among the brightest in the auroral spectrum. Previous observations in Longyearbyen, Svalbard, indicated that it may be intrinsically polarized, but a possible contamination by light pollution could not be ruled out. During the winter 2010/2011, the polarization of the red line was measured for the first time at the Polish Hornsund polar base without contamination. Two methods of data analysis are presented to compute the degree of linear polarization (DoLP) and angle of linear polarization (AoLP): one is based on averaging and the other one on filtering. Results are compared and are in qualitative agreement. For solar zenith angles (SZA) larger than 108° (with no contribution from Rayleigh scattering), the DoLP ranges between 2 and 7%. The AoLP is more or less aligned with the direction of the magnetic field line, in agreement with the theoretical predictions of . However, the AoLP values range between ±20° around this direction, depending on the auroral conditions. Correlations between the polarization parameters and the red line intensity I were considered. The DoLP decreases when I increases, confirming a trend observed during the observations in Longyearbyen. However, for small values of I, DoLP varies within a large range of values, while for large values of I, DoLP is always small. The AoLP also varies with the red line intensity, slightly rotating around the magnetic field line. | ||||
| Programme |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | Bachelor's thesis | |||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 2115-7251 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 7962 | |||
| Permanent link to this record | |||||
| Author | Mathieu Barthelemy, Hervé Lamy, Anne Vialatte, Magnar Gullikstad Johnsen, Gaël Cessateur, Naïma Zaourar | ||||
| Title | Measurement of the polarisation in the auroral N2+ 427.8 nm band | Type | Journal | ||
| Year | 2019 | Publication | Journal of Space Weather and Space Climate | Abbreviated Journal | |
| Volume | 9 | Issue | Pages | A26 | |
| Keywords | |||||
| 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 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. | ||||
| Programme |
1026 | ||||
| Campaign | |||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 2115-7251 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 8172 | |||
| Permanent link to this record | |||||