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Following the survey Well-being in astrophysics that was sent out in March 2021, to establish how astrophysics researchers, primarily in France, experience their career, some of the results were published in Webb et al. (2021). Here we further analyse the data to determine if gender can cause different experiences in astrophysics. We also study the impact on the well-being of temporary staff (primarily PhD students and postdocs), compared to permanent staff. Whilst more temporary staff stated that they felt permanently overwhelmed than permanent staff, the experiences in astrophysics for the different genders were in general very similar, except in one area. More than three times more females than males experienced harassment or discrimination, rising sharply for gender discrimination and sexual harassment, where all of those having experienced sexual harassment and who had provided their gender in the survey, were female. Further, as previously reported (Webb et al. 2021), 20% of the respondents had suffered mental health issues before starting their career in astrophysics. We found that whilst this group was split approximately equally with regards to males and females, the number rose sharply to almost 45% of astronomers experiencing mental health issues since starting in astrophysics. Of this population, there were 50% more females than males. This excess of females was almost entirely made up of the population of women that had been harassed or discriminated against., 5 pages, 1 figure, published in the SF2A-2022: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics. Eds.: J. Richard, A. Siebert, E. Lagadec, N. Lagarde, O. Venot, J. Malzac, J.-B. Marquette, M. N'Diaye, D. Briot, pp.171-175

We consider a conventional $\alpha-\Omega$-dynamo model with meridional circulation that exhibits typical features of the solar dynamo, including a Hale cycle period of around 20 years and a reasonable shape of the butterfly diagram. With regard to recent ideas of a tidal synchronization of the solar cycle, we complement this model by an additional time-periodic $\alpha$-term that is localized in the tachocline region. It is shown that amplitudes of some dm/s are sufficient for this $\alpha$-term to become capable of entraining the underlying dynamo. We argue that such amplitudes of $\alpha$ may indeed be realistic, since velocities in the range of m/s are reachable, e.g., for tidally excited magneto-Rossby waves., Comment: 14 pages, 6 figures

We consider a conventional $α-Ω$-dynamo model with meridional circulation that exhibits typical features of the solar dynamo, including a Hale cycle period of around 20 years and a reasonable shape of the butterfly diagram. With regard to recent ideas of a tidal synchronization of the solar cycle, we complement this model by an additional time-periodic $α$-term that is localized in the tachocline region. It is shown that amplitudes of some dm/s are sufficient for this $α$-term to become capable of entraining the underlying dynamo. We argue that such amplitudes of $α$ may indeed be realistic, since velocities in the range of m/s are reachable, e.g., for tidally excited magneto-Rossby waves., 14 pages, 6 figures

It has become clear that early career astrophysics researchers (doctoral researchers, post-docs, etc) have a very diverse appreciation of their career, with some declaring it the best job that you can have and others suffering from overwork, harrassment and stress from the precarity of their job, and associated difficulties. In order to establish how astrophysics researchers, primarily in France, experience their career, we sent out a survey to understand the impact that their job has on their well-being. 276 people responded to the survey. Whilst around half of the respondents expressed pleasure derived from their career, it is clear that many (early career) researchers are suffering due to overwork, with more than a quarter saying that they work in excess of 50 hours per week and 2\% in excess of 90 h per week. Almost 30\% professed to having suffered harrassment or discrimination in the course of their work. Further, whilst only 20\% had suffered mental health issues before starting their career in astrophysics, $\sim$45\% said that they suffered with mental health problems since starting in astrophysics. Here we provide results from the survey as well as possible avenues to explore and a list of recommendations to improve (early) careers in astrophysics., 6 page conference proceedings on well-being in French astrophysics

Some contracting or expanding stars are thought to host a large-scale magnetic field in their radiative interior. By interacting with the contraction-induced flows, such fields may significantly alter the rotational history of the star. They thus constitute a promising way to address the problem of angular momentum transport during the rapid phases of stellar evolution. In this work, we aim at studying the interplay between flows and magnetic fields in a contracting radiative zone. We propose a scenario that may account for the post-main sequence evolution of solar-like stars, in which a quasi-solid rotation can be maintained by a large-scale magnetic field during a contraction timescale. Then, an axisymmetric instability would destroy this large-scale structure and enables the differential rotation to set in. Such a contraction driven instability could also be at the origin of the observed dichotomy between strongly and weakly magnetic intermediate-mass stars., 31 pages, 29 figures, 3 tables, accepted for publication in Astronomy & Astrophysics

This study aims at investigating the ability of strong interactions between magnetic field concentrations during their rise through the convection zone to produce complex active regions at the solar surface. To do so, we perform numerical simulations of buoyant magnetic structures evolving and interacting in a model solar convection zone. We first produce a 3D model of rotating convection and then introduce idealized magnetic structures close to the bottom of the computational domain. These structures possess a certain degree of field line twist and they are made buoyant on a particular extension in longitude. The resulting twisted $��$-loops will thus evolve inside a spherical convective shell possessing large-scale mean flows. We present results on the interaction between two such loops with various initial parameters (mainly buoyancy and twist) and on the complexity of the emerging magnetic field. In agreement with analytical predictions, we find that if the loops are introduced with opposite handedness and same axial field direction or same handedness but opposite axial field, they bounce against each other. The emerging region is then constituted of two separated bipolar structures. On the contrary, if the loops are introduced with the same direction of axial and peripheral magnetic fields and if sufficiently close, they merge while rising. This more interesting case produces complex magnetic structures, with a high degree of non-neutralized currents, especially when the convective motions act significantly on the magnetic field. This indicates that those interactions could be good candidates to produce eruptive events like flares or CMEs., 39 pages, 20 figures, accepted for publication in ApJ

In this talk, we will review some aspects of the stellar magnetism and in particular what numerical simulations tell us about the physical processes underlying the observations. In cool stars, a convective dynamo is thought to be responsible for the presence and evolution of magnetic fields. The question of the impact of the internal stellar structure on the magnetic field topology will be addressed. We will focus in particular on the role of differential rotation and of a tachocline. Another important aspect of stellar dynamos is the possible presence of magnetic cycles and how its period depends on the stellar parameters. Numerical simulations addressing this issue will be presented. Finally, one step of the dynamo process is the emergence of magnetic flux from the interior where it is created and organised to the exterior where it emerges as starspots. We will also show results of global 3D MHD numerical simulations of such a process.

An extremely weak circularly polarized signature was recently discovered in spectral lines of the chemically peculiar Am star Sirius A. A weak surface magnetic field was proposed to account for the observed polarized signal, but the shape of the phase-averaged signature, dominated by a prominent positive lobe, is not expected in the standard theory of the Zeeman effect. We aim at verifying the presence of weak circularly polarized signatures in two other bright Am stars, beta UMa and theta Leo, and investigating the physical origin of Sirius-like polarized signals further. We present here a set of deep spectropolarimetric observations of beta UMa and theta Leo, observed with the NARVAL spectropolarimeter. We analyzed all spectra with the Least Squares Deconvolution multiline procedure. To improve the signal-to-noise ratio and detect extremely weak signatures in Stokes V profiles, we co-added all available spectra of each star (around 150 observations each time). Finally, we ran several tests to evaluate whether the detected signatures are consistent with the behavior expected from the Zeeman effect. The line profiles of the two stars display circularly polarized signatures similar in shape and amplitude to the observations previously gathered for Sirius A. Our series of tests brings further evidence of a magnetic origin of the recorded signal. These new detections suggest that very weak magnetic fields may well be present in the photospheres of a significant fraction of intermediate-mass stars. The strongly asymmetric Zeeman signatures measured so far in Am stars (featuring a dominant single-sign lobe) are not expected in the standard theory of the Zeeman effect and may be linked to sharp vertical gradients in photospheric velocities and magnetic field strengths.

We here report calculations of magnetic buoyancy instabilities of a sheared magnetic layer where two separate zones are unstable. The idea is to study the possible generation of large-scale helical structures which could then rise through a stellar convection zone and emerge at the surface to create active regions. The calculations shown here are a follow-up of the work of Favier et al. (2012) where the instability developed in a weakly magnetized atmosphere, consisting of a uniform field oriented in a different direction from the unstable layer below. Here, the top layer representing the atmosphere is itself unstable to buoyancy instabilities and thus quickly creates a more complex magnetic configuration with which the layer below will interact. We also find in this case that the accumulation of magnetic tension between the two unstable layers favors the creation of large-scale helical structures., French Astrophysics Society Conference Proceedings, 4 pages, 4 figures

We have developed a variational data assimilation technique for the Sun using a toy {\alpha}{\Omega} dynamo model. The purpose of this work is to apply modern data assimilation techniques to solar data using a physically based model. This work represents the first step toward a complete variational model of solar magnetism. We derive the adjoint {\alpha}{\Omega} dynamo code and use a minimization procedure to invert the spatial dependence of key physical ingredients of the model. We find that the variational technique is very powerful and leads to encouraging results that will be applied to a more realistic model of the solar dynamo. We also note that the continuous adjoint mean-field induction equation is derived in the appendix., Comment: 16 pages, 14 figures, accepted for publication in ApJ

Plantlets of Populus euphratica (from Ein Avdat natural park, Israel) were obtained by in vitro culture, ex vitro acclimated, transferred and acclimated to Nancy's greenhouse conditions. They were transplanted into 7.5 L-pot filled with peat-sand mix (50/50 V/V). A moderate, increasing drought stress was applied and controlled for 6 weeks through soil volumetric water content (SWC). A predetermined batch of plantlets (including control and stressed trees) was harvested at 4 stress intensities (10, 7.5, 5, 4% SWC) and after 10 days back to fully available water, in order to analyse transcriptome in leaves and roots, and proteome and other biochemical compounds in leaves (pigments, soluble carbohydrates). Growth (height, diameter, root elongation), water potential, leaf relative water content, net CO2 assimilation rate and stomatal conductance were measured on another batch of plants following the same drought time course and recovery. The degree of sensitivity to drought of the measured physiological parameters was established. The most sensitive to the less sensitive were stem diameter growth, height diameter, stomatal conductance, leaf relative water content, mid-day leaf water potential, photosynthesis, root elongation and predawn leaf water potential. An EST database with the P. euphratica ESTs including annotative attributes can be viewed at http://sputnik.btk.fi. In common with other P. euphratica microarray experiments, very few genes (68 in leaves and 39 in roots of the 7400 present on the array) were regulated by drought. In leaves, the number of regulated genes which increased with stress intensity returned to almost zero after re-irrigation. By contrast, the number of proteins in which abundance was modified decreased with stress intensity and remained important after re-irrigation. Moreover, while the fold change of most up-regulated genes increased with stress intensity, the relative abundance of most proteins was diminished with increasing stress intensity. Nature of regulated genes, at the level of the transcript or of the protein, are analysed and discussed in relation to ecophysiological responses.

International audience

Etude de l'effet de l'abaissement de la température de 27¼C à 21, 12 et 4¼C et d'une diminution de la quantité d'oxygène par immersion sous de la paraffine liquide sur la conservation en culture in vitro de pousses feuillées issues de microboutures de C. arabica cv Moka de Tahiti. La durée de conservation est de 4 mois. Une température de 4¼C entraîne rapidement une mortalité totale, alors que la survie sur milieu standard est complète à partir de 12¼C. Sur milieu standard la croissance est d'autant plus ralentie que la température du stockage est basse. Sur milieu paraffine la survie est diminuée à 27¼C et la diminution de croissance est la même quelle que soit la température car c'est d'abord l'hypoxie qui est responsable du ralentissement observé. La reprise de croissance est plus faible chez les plants conservés sous paraffine, mais on note une bonne survie dans toutes les conditions