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| 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 | |
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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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| Programme | 1026 | ||||
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| 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 | 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 | |
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| 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 | ||||
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| 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 | ||||
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| 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 | |
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| 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 | Mike Lockwood, Carl Haines, Luke A. Barnard, Mathew J. Owens, Chris J. Scott, Aude Chambodut, Kathryn A. McWilliams | ||||
| Title | Semi-annual, annual and Universal Time variations in the magnetosphere and in geomagnetic activity: 4. Polar Cap motions and origins of the Universal Time effect | Type | Journal | ||
| Year | 2021 | Publication | Journal of Space Weather and Space Climate | Abbreviated Journal | |
| Volume | 11 | Issue | Pages | 15 | |
| Keywords | |||||
| Abstract | We use the am, an, as and the aσ geomagnetic indices to the explore a previously overlooked factor in magnetospheric electrodynamics, namely the inductive effect of diurnal motions of the Earth’s magnetic poles toward and away from the Sun caused by Earth’s rotation. Because the offset of the (eccentric dipole) geomagnetic pole from the rotational axis is roughly twice as large in the southern hemisphere compared to the northern, the effects there are predicted to be roughly twice the amplitude of those in the northern hemisphere. Hemispheric differences have previously been discussed in terms of polar ionospheric conductivities generated by solar photoionization, effects which we allow for by looking at the dipole tilt effect on the time-of-year variations of the indices. The electric field induced in a geocentric frame is shown to also be a significant factor and gives a modulation of the voltage applied by the solar wind flow in the southern hemisphere that is typically a ±30% diurnal modulation for disturbed intervals rising to ±76% in quiet times. For the northern hemisphere these are 15% and 38% modulations. Motion away from/towards the Sun reduces/enhances the directly-driven ionospheric voltages and reduces/enhances the magnetic energy stored in the tail and we estimate that approximately 10% of the effect appears in directly driven ionospheric voltages and 90% in changes of the rate of energy storage or release in the near-Earth tail. The hemispheric asymmetry in the geomagnetic pole offsets from the rotational axis is shown to be the dominant factor in driving Universal Time (UT) variations and hemispheric differences in geomagnetic activity. Combined with the effect of solar wind dynamic pressure and dipole tilt on the pressure balance in the near-Earth tail, the effect provides an excellent explanation of how the observed Russell-McPherron pattern with time-of-year F and UT in the driving power input into the magnetosphere is converted into the equinoctial F-UT pattern in average geomagnetic activity (after correction is made for dipole tilt effects on ionospheric conductivity), added to a pronounced UT variation with minimum at 02–10 UT. In addition, we show that the predicted and observed UT variations in average geomagnetic activity has implications for the occurrence of the largest events that also show the nett UT variation. | ||||
| Programme | 139 | ||||
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| 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 | 8076 | |||
| 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 | |
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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 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 | ||||
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| 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 | |||||
| Author | Sophie Musset, Karl-Ludwig Klein, Nicolas Fuller, Gaelle Khreich, Antonin Wargnier | ||||
| Title | The time profile of relativistic solar particle events as observed by neutron monitors | Type | Journal | ||
| Year | 2023 | Publication | Journal of Space Weather and Space Climate | Abbreviated Journal | |
| Volume | 13 | Issue | Pages | 15 | |
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| Abstract | The most energetic particles accelerated in solar eruptive events are protons and nuclei with energies that may reach a few tens of GeV. They can be detected on the Earth through the secondaries they produce when interacting with the atmosphere. Solar energetic particle events where this happens are called Ground-Level Enhancements (GLEs). Their study is relevant on the one hand because the high particle energies pose particularly strong challenges to the understanding of the acceleration processes. On the other hand, the secondary particles constitute a source of radiation in the atmosphere that may temporarily exceed the permanent dose rate from galactic cosmic rays. This makes the monitoring of radiation doses received by aircrew from GLEs one issue of space weather services for civil aviation. This study addresses the time profiles of GLEs, in the search for commonalities that can be used to constrain models of acceleration and propagation and to forecast the evolution of an ongoing event. We investigate historical GLEs (1971–2012) with the worldwide network of neutron monitors, comparing the rise and the decay as observed by the neutron monitor with the strongest response. The sample comprises 23 events. We evaluate statistical correlations between rise time and decay time inferred from fits to the time profiles and compute a normalised median GLE time profile. An empirical correlation reported in earlier work between the observed rise times and decay times of the neutron monitor count rate profiles is confirmed. We find indications of a statistical relationship between the rise times and the parent eruptive activity. We discuss ideas on the mechanisms behind the correlation of rise and decay times and on its usefulness for space weather services. | ||||
| Programme | 227 | ||||
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| 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 | 8555 | |||
| Permanent link to this record | |||||
| Author | Héloïg Barbel Le Page, Dominique Todisco, James Woollett | ||||
| Title | (Re)penser la relation au territoire : vers une archéologie de l’habiter | Type | Journal | ||
| Year | 2022 | Publication | Palethnologie. Archéologie et sciences humaines | Abbreviated Journal | |
| Volume | Issue | 11 | Pages | ||
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| Abstract | La posture endossée par les chercheur.es structure les problématiques qu’il.elle.s abordent et leurs choix quant aux approches employées pour les étudier. Cet article offre une réflexion sur l’importance de questionner nos postures paradigmatiques, qui structurent notre rapport à la recherche. Elle a émergé de recherches menées en collaboration avec le Gouvernement du Nunatsiavut et la communauté de Nain (Nunatsiavut, Labrador, Canada). Celles-ci contribuent à pluraliser les narrations historiques sur la période coloniale, en s’intéressant à la diversité des choix des Nunatsiavummiut concernant leurs relations avec le système missionnaire. Cette discussion, articulant archéologie et géographie, développe une approche relationnelle du territoire par l’habiter et questionne la trace laissée par les systèmes d’activités quotidiennes à travers le temps et l’espace. Une réflexion sur les façons d’appréhender la complexité des relations aux lieux, au paysage et aux artefacts nous amène à aborder la diversité des vestiges mis au jour, et la nécessité d’une mise en dialogue des disciplines pour étudier les systèmes d’activités passés à partir de leurs traces. | ||||
| Programme | 1080 | ||||
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| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN |
2108-6532 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 8705 | |||
| Permanent link to this record | |||||
| Author | MAJ Emilie | ||||
| Title | Des tournants spatiaux : approche diachronique de la sémiotique du paysage en Sibérie, l’exemple de la République Sakha (Iakoutie)] | Type | Journal Article | ||
| Year | 2009 | Publication | GéoCité | Abbreviated Journal | |
| Volume | 1 | Issue | Pages | ||
| Keywords | Landscape, Siberia, Republic Sakha (Yakutia), Sakha, Yakut, Siberian minoritites,Turkic people, semiotic, temporality, space, history, place, taiga, domestication | ||||
| Abstract | About the evolution of worlddview and conception of landscape in Yakut culture:
Based on geographical and anthropological litterature and on the field data collected during the missions Ethnoequid 2003-2006 and Festivethno 2009. |
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| Programme | 1024 | ||||
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| 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 |
2105-0724 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 1890 | |||
| Permanent link to this record | |||||
| Author | Chattova B., Van de Vijver B., Lebouvier M., De Smet W., Uher B. | ||||
| Title | Freshwater diatoms of Ile Amsterdam (TAAF, Southern Indian Ocean) | Type | Poster | ||
| Year | 2011 | Publication | European journal of phycology, fifth european phycological congress, rhodes, greece, 4–9 september 2011 submit an article journal homepage 2011 | Abbreviated Journal | |
| Volume | 46 | Issue | Sup1 | Pages | |
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| Abstract | |||||
| Programme | 136 | ||||
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| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN |
20967-0262 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | yes | |||
| Call Number | Serial | 8715 | |||
| Permanent link to this record | |||||