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The Solar Orbiter merged magnetic field
No full textInternational audienceContext. In situ studies of the solar wind require precise magnetic field measurements at all frequencies. The Solar Orbiter mission carries two magnetometers to measure the solar wind magnetic field: the fluxgate magnetometer (MAG), which is best suited for frequencies from DC to a few Hertz, and the search coil magnetometer (SCM), which is best suited for frequencies above a few Hertz.Aims: The aim of this paper is to produce a merged magnetic field data product that takes the best of both instruments and provides the community with high quality, easy to use magnetic field data over a wide range of frequencies.Methods: We first compared the two instruments in their overlapping frequency range, then we performed the merging in Fourier space using a weighted function determined by the sensitivity of the two sensors.Results: The two instruments are found to give consistent results in their overlapping frequency range. SCM has a lower gain than MAG by 14% around 1 Hz and MAG is delayed by about 20 ms with respect to SCM, and the merged magnetic field takes care of these discrepancies. It is basically identical to MAG data below 2 Hz and to SCM data above about 15 Hz (with amplitude increased by 14%). We show that the merged magnetic field is suitable to analyse waves and turbulence over a broad frequency range, in particular by confirming that ion cyclotron waves can lower the level of energy at the sub ionic scales. The merged magnetic field is distributed as daily files containing the magnetic field at either 256 or 4096 Hz, and either in the radial-tangential-normal co-ordinates or in the spacecraft reference frame co-ordinates
Locating the Earth's Magnetopause Through X-Ray Imaging
No full textInternational audienceDespite the development of several empirical magnetopause models based on statistical analyses of in-situ crossings, capturing the global dynamics of the magnetopause remains a significant challenge. Current work discusses new steps in the modeling of the X-ray emission produced in the Earth's magnetosheath due to the Solar Wind Charge eXchange (SWCX) processes. Initially discovered and explained for comets [1], this emission, produced by highly charged solar wind ions (e.g. O7+), has also been observed from interplanetary gas, planets, terrestrial magnetosheath, etc. [2]. SWCX emission in the Earth's magnetosheath will be the target of the future joint ESA and CAS space mission called SMILE (Solar wind Magnetosphere Ionosphere Link Explorer). The goal of the current study is to develop a methodology that will probe the global dynamics of the magnetopause, by utilizing the remote sensing capabilities of the Soft X-ray Imager (SXI) onboard. In this light, the team has developed the LATMOS Test Particle (LaTeP) model, a Test Particle (TP) model with input electric (E) and magnetic (B) fields from MHD (OpenGGCM) simulations, that is capable of estimating the levels of X-ray flux in the Earth's magnetosheath. In the LaTeP model, we follow numerical test-particles, representing O7+ ions, solving their motion equation as they propagate in the MHD-computed E and B fields, and calculate the probability of them charge exchanging with hydrogen atoms from the Earth's exosphere. The produced X-ray emission cubes are being projected and integrated over the imager's Field of View (FOV) cone, returning the synthetic images of the SXI instrument. We propose a methodology for retrieving the instantaneous location and topology of the magnetopause from single SXI images. This approach assumes that the magnetopause's tangent direction coincides with the curve of maximum intensity in the image [3], a hypothesis we test against simulation inputs. A processing pipeline is developed to fit the empirical model tangent curves to the image-derived tangent directions, and performance is benchmarked both against the intensity maxima and simulation input. Assuming a given empirical model, this technique enables the retrieval of optimal model parameters and provides a quantitative assessment of model performance. From the fitted parameters we can reconstruct the surface, providing information about the location and shape of the magnetopause
BEETROOTS: Spatially regularized Bayesian inference of physical parameter maps. Application to Orion
No full textInternational audienceContext. The current generation of millimeter (mm) receivers is capable of producing cubes of 800 000 pixels over 200 000 frequency channels to cover a number of square degrees over the 3 mm atmospheric window. Estimating the physical conditions of the interstellar medium (ISM) with an astrophysical model on the basis of such large datasets is challenging. Common approaches tend to converge to local minima and end up poorly reconstructing regions with a low signal-to-noise ratio (S/N) in most cases. This instrumental revolution thus calls for new scalable data analysis techniques with more advanced approaches to statistical modeling and methods.Aims. Our aim is to design a general method to reconstruct large maps of physical conditions from the rich datasets produced by new and future instruments. The requirements of the method include the ability to scale to very large maps, to be robust to varying S/N, and to escape from the local minima. In addition, we want to quantify the uncertainties associated with our reconstructions to produce reliable analyses.Methods. We present BEETROOTS, a PYTHON software that performs Bayesian reconstructions of maps of physical conditions based on observation maps and an astrophysical model. It relies on an accurate statistical model, exploits spatial regularization to guide estimations, and uses state-of-the-art algorithms. It can also assess the ability of the astrophysical model to explain the observations, providing feedback to improve ISM models. In this work, we demonstrate the power of BEETROOTS with the Meudon PDR code on synthetic data. We then apply it to estimate physical condition maps in the full Orion molecular cloud 1 (OMC-1) star-forming region based on Herschel molecular line emission maps.Results. The application to the synthetic case shows that BEETROOTS can currently analyze maps with up to ten thousand pixels, addressing large variations among the S/N values within the observations while escaping from local minima and providing consistent uncertainty quantifications. On a personal laptop, the inference runtime ranges from a few minutes for maps of 100 pixels to 28 hours for maps of 8100 pixels. Regarding OMC-1, our reconstructions of the incident UV radiation field intensity, G0, are consistent with those obtained from FIR luminosities. This demonstrates that the considered molecular tracers are able to constrain G0 over a wide range of environments. In addition, the obtained thermal pressures are high in all dense regions of OMC-1 and positively correlated with G0. Finally, the Meudon PDR code successfully explains the observations and the obtained G0 values are reasonable, which indicates that UV photons control the gas physics and chemistry across the rim of OMC-1.Conclusions. This work paves the way toward systematic and rigorous analyses of observations produced by current and future instruments. Subsequent efforts still need to be made in parallelizing the algorithm and thereby gaining two orders of magnitude for the map sizes
Il y a 30 ans (1995) entrait en opération la base de données solaires sol BASS2000 de l'INSU/CNRS
No full textNous présentons dans cet article la genèse de la base de données solaires sol BASS2000 fondée par l'INSU/CNRS et toujours active en 2025. Celle-ci était répartie initialement sur deux sites : l'un à Meudon (dit antenne meudonnaise) dont l'activité a démarré dès 1995, pour l'archivage et la distribution des spectrohéliogrammes du disque solaire complet (données de service d'une collection centenaire) ; et l'autre à Bagnères de Bigorre, pour l'archivage et la distribution des données de recherche sur campagne du télescope THEMIS de l'INSU/CNRS (petites régions de taille typique 2' x 2' en haute résolution), instrument qui fut livré aux astronomes en 1999
Optimizing NN reduction in an atom interferometer network for GW detection
No full textInternational audienceThe sensitivity of an atom gradiometer aiming to detect gravitational waves (GW) is impacted by fluctuations of Earth's gravity field also called Newtonian Noise (NN). Sensor arrays have proved to be a promising technique for NN reduction. In our study, we further investigate the benefits of Atom Interferometer (AI) networks by improving their geometry and the extraction of the GW signal. We focus on Seismic Newtonian Noise in the frequency band from 0.1 to 10 Hz. On one hand, we show that using a specific detector geometry, a better NN rejection can occur optimizing the number of gradiometers in the network. On the other hand, we show that carrying out optimization in sub frequency bands - which results in using various detector geometries from a common network - allows even higher NN rejection while keeping a similar number of interferometers
Euclid preparation. LXXII. Three-dimensional galaxy clustering in configuration space: Two-point correlation function estimation
No full textInternational audienceThe two-point correlation function of the galaxy spatial distribution is a major cosmological observable that enables constraints on the dynamics and geometry of the Universe. The Euclid mission is aimed at performing an extensive spectroscopic survey of approximately 20–30 million Hα-emitting galaxies up to a redshift of about 2. This ambitious project seeks to elucidate the nature of dark energy by mapping the three-dimensional clustering of galaxies over a significant portion of the sky. This paper presents the methodology and software developed for estimating the three-dimensional two-point correlation function within the Euclid Science Ground Segment. The software is designed to overcome the significant challenges posed by the large and complex Euclid dataset, which involves millions of galaxies. The key challenges include efficient pair counting, managing computational resources, and ensuring the accuracy of the correlation function estimation. The software leverages advanced algorithms, including k-d tree, octree, and linked-list data partitioning strategies, to optimise the pair-counting process. These methods are crucial for handling the massive volume of data efficiently. The implementation also includes parallel processing capabilities using shared-memory open multi-processing to further enhance performance and reduce computation times. Extensive validation and performance testing of the software are presented. Those have been performed by using various mock galaxy catalogues to ensure that it meets the stringent accuracy requirement of the Euclid mission. The results indicate that the software is robust and can reliably estimate the two-point correlation function, which is essential for deriving cosmological parameters with high precision. Furthermore, the paper discusses the expected performance of the software during different stages of Euclid Wide Survey observations and forecasts how the precision of the correlation function measurements will improve over the mission’s timeline, highlighting the software’s capability to handle large datasets efficiently
The brightest GRB ever detected: GRB 221009A as a highly luminous event at z = 0.151
No full textInternational audienceContext: The extreme luminosity of gamma-ray bursts (GRBs) makes them powerful beacons for studies of the distant Universe. The most luminous bursts are typically detected at moderate/high redshift, where the volume for seeing such rare events is maximized and the star-formation activity is greater than at z = 0. For distant events, not all observations are feasible, such as at TeV energies. Aims: Here we present a spectroscopic redshift measurement for the exceptional GRB 221009A, the brightest GRB observed to date with emission extending well into the TeV regime. Methods: We used the X-shooter spectrograph at the ESO Very Large Telescope (VLT) to obtain simultaneous optical to near-IR spectroscopy of the burst afterglow 0.5 days after the explosion. Results: The spectra exhibit both absorption and emission lines from material in a host galaxy at z = 0.151. Thus GRB 221009A was a relatively nearby burst with a luminosity distance of 745 Mpc. Its host galaxy properties (star-formation rate and metallicity) are consistent with those of LGRB hosts at low redshift. This redshift measurement yields information on the energy of the burst. The inferred isotropic energy release, E_{\rm iso} > 5 \times 10^{54} erg, lies at the high end of the distribution, making GRB 221009A one of the nearest and also most energetic GRBs observed to date. We estimate that such a combination (nearby as well as intrinsically bright) occurs between once every few decades to once per millennium
Constraints on neutrino-Majoron couplings using SN1987A data
No full textInternational audienceNeutrino decay to a lighter neutrino and a massless (pseudo)scalar Goldstone boson remains of wide interest, as in the search for ultralight dark matter or of neutrinoless double beta-decay, and for its implications in astrophysics and cosmology. Neutrino interactions with Majorons can affect the dynamics of supernovae and impact the emitted neutrino flux. Using a three-neutrino framework and detailed supernova simulations, we perform the first likelihood analysis of the 24 neutrino events from SN1987A, including nonradiative decay in matter to a massless (pseudo)scalar boson like a Majoron. Focusing on the induced spectral distortions, we present bounds on the neutrino-Majoron couplings, as a function of the lightest neutrino mass, that are either complementary or competitive with current ones
LHAASO detection of very-high-energy gamma-ray emission surrounding PSR J0248+6021
No full textInternational audienceWe report the detection of an extended very-high-energy (VHE) gamma-ray source coincident with the locations of middle-aged (62.4~\rm kyr) pulsar PSR J0248+6021, by using the LHAASO-WCDA data of live 796 days and LHAASO-KM2A data of live 1216 days. A significant excess of \gray induced showers is observed both by WCDA in energy bands of 1-25~\rm TeV and KM2A in energy bands of 25~\rm TeV with 7.3 and 13.5 , respectively. The best-fit position derived through WCDA data is R.A. = 42.06 0.12 and Dec. = 60.24 0.13 with an extension of 0.690.15 and that of the KM2A data is R.A.= 42.29 0.13 and Dec. = 60.38 0.07 with an extension of 0.370.07. No clear extended multiwavelength counterpart of this LHAASO source has been found from the radio band to the GeV band. The most plausible explanation of the VHE \gray emission is the inverse Compton process of highly relativistic electrons and positrons injected by the pulsar. These electrons/positrons are hypothesized to be either confined within the pulsar wind nebula or to have already escaped into the interstellar medium, forming a pulsar halo
Search for quantum decoherence in neutrino oscillations with six detection units of KM3NeT/ORCA
No full textInternational audienceNeutrinos described as an open quantum system may interact with the environment which introduces stochastic perturbations to their quantum phase. This mechanism leads to a loss of coherence along the propagation of the neutrino a phenomenon commonly referred to as decoherence and ultimately, to a modification of the oscillation probabilities. Fluctuations in space-time, as envisaged by various theories of quantum gravity, are a potential candidate for a decoherence-inducing environment. Consequently, the search for decoherence provides a rare opportunity to investigate quantum gravitational effects which are usually beyond the reach of current experiments. In this work, quantum decoherence effects are searched for in neutrino data collected by the KM3NeT/ORCA detector from January 2020 to November 2021. The analysis focuses on atmospheric neutrinos within the energy range of a few GeV to . Adopting the open quantum system framework, decoherence is described in a phenomenological manner with the strength of the effect given by the parameters and . Following previous studies, a dependence of the type on the neutrino energy is assumed and the cases are explored. No significant deviation with respect to the standard oscillation hypothesis is observed. Therefore, CL upper limits are estimated as \Gamma_{21} < 4.6\cdot 10^{-21}\,GeV and \Gamma_{31} < 8.4\cdot 10^{-21}\,GeV for , and \Gamma_{21} < 1.9\cdot 10^{-22}\,GeV and \Gamma_{31} < 2.7\cdot 10^{-22}\,GeV for , respectively