Europa’s interaction with the jovian plasma from hybrid simulation

<p>Galilean moons are embedded in Jupiter’s giant magnetosphere. The jovian plasma particles interact with the atmosphere of the moons, exchanging momentum and energy, and generate different phenoma such as aurora, electric current, etc.</p> <p>The exploration of the Galilean moons, and in particular Ganymede and Europa considered as potential habitats, are listed among the main objectives of the ESA JUpiter ICy moon Explorer mission. In preparation of future observations, a simulation effort is conducted to describe the Europa moon-magnetosphere system as well as a study of radio wave propagation in the environments of Ganymede and Europa using a ray tracing code.</p> <p>LatHyS is a hybrid 3D, multi-species and parallel simulation model which is based on a kinetic description of ions and a fluid description of electrons. The model is based on the CAM-CL algorithm that Alan Matthews¹ outlined in 1994. It allows to describe the interaction between the jovian plasma and the moon environments. As Ganymede's environment has already been implemented, we propose to enrich the model by completing it with Europa's – jovian plasma interaction and to optimize it in order to improve the accuracy of the results.</p> <p>Artemis-P, developed by Gautier² in 2013, is a ray tracing code that calculates the trajectory of waves through a given environment. Planetary environments are anisotropic and inhomogeneous, so that radio waves can undergo refraction, reflection, scattering, diffraction, interference, etc. between the source and the detector. The ray tracing methods allow to treat the refraction and reflection phenomena at large scales compared to the wavelength. The proposed work is to adjust this program to the environments of Ganymede and Europa using data from LatHyS simulations.</p> <p> </p> <p align="left">Références :</p> <p align="left"><sup>1</sup> Alan P. Matthews, Current Advance Method and Cyclic Leapfrog for 2D Multispecies Hybrid Plasma Simulations, Journal of Computational Physics, Volume 112, Issue 1, 1994, Pages 102-116, ISSN 0021-9991, https://doi.org/10.1006/jcph.1994.1084.</p> <p align="left">² Anne-Lise Gautier. Étude de la propagation des ondes radio dans les environnements planétaires. Planétologie et astrophysique de la terre [astro-ph.EP]. Observatoire de Paris, 2013. Français. tel-01145651v2</p>

The rotation of Ganymede and Callisto

<p>The rotation rates of Ganymede and Callisto, the two largest satellites of Jupiter, are on average equal to their orbital mean motion but cannot be constant as a result of the varying gravitational torque exerted by Jupiter on the satellites. For a Keplerian orbit, the period of the torque and of the rotation variations is equal to the orbital period. Gravitational interaction with the other Galilean satellites and the Sun induces deviations from a purely Keplerian orbital motion, leading to changes in the gravitational torque of Jupiter on the satellites with respect to the mean Keplerian orbital motion and therefore to additional rotation variations. Here we discuss small variations from the average rotation on different time scales and assess the potential of using rotation as a probe of the interior structure.</p> <p>The ESA JUICE (JUpiter ICy moons Explorer) mission will measure the rotation and tides of Ganymede and Callisto in the early 30s, and will in particular very accurately determine those quantities for Ganymede during the orbital phase of the spacecraft around that satellite starting in 2032. We report on different theoretical aspects of the rotation for realistic models of the interior of the satellites, include tidal deformations and take into account the low-degree gravity field and topography of Ganymede and Callisto. We assess the advantages of a joint use of rotation and tides to constrain the satellite's interior structure, in particular its ice shell and ocean.</p>

Ganymede’s interaction with the jovian plasma from hybrid simulation

<p>The JUICE (JUpiter ICy moon Explorer) mission, selected by the European Space Agency in May 2012 to be the first large mission within the Cosmic Vision Program 2015–2025, will provide the most comprehensive exploration to date of the Jovian system in all its complexity, with particular emphasis on Ganymede as a planetary body and potential habitat (JUICE Red Book, 2014). The Galilean satellites are known to have thin atmospheres, technically exospheres (McGrath et al., 2004), produced by ion-induced sputtering and sublimation of the surface materials. These moons and tenuous atmosphere are embedded in the flowing plasma of the jovian. The interaction between the neutral environments of the Galilean satellites and the jovian plasma changes the plasma momentum, the temperature and generates strong electrical currents. In order to prepare the scientific return of the mission and the optimization of operation modes of plasma instruments, a modeling effort has been carried out at LATMOS (PhD R. Allioux, IRAP, 2012; L. Leclercq, LATMOS, 2015; O. Apurva, LATMOS, 2017). A 3D parallel multi-species hybrid model (Latmos Hybrid Simulation, LatHyS) has been developed to model and characterize the plasma environment of Ganymede (Leclercq et al, 2016; Modolo et al, 2016) and a 3D parallel multi-species exospheric model (Exospheric Global Model, EGM) to pattern the dynamic of the neutral envelopes of Ganymede (Turc et al, 2014; Leblanc et al, 2017). The presentation will examine the global structure of the interaction with the jovian plasma, to describe the formation of Alfvén wings, and to emphasize the phenomena related to the multi-species nature of the plasma. The simulation model supports the preparation of the JUICE mission and its Ganymede phase by characterizing boundary crossings.</p>

MHD simulations of magnetospheric response to a strong solar wind density pulse

<p>On 16-17 June 2012, an interplanetary coronal mass ejection with an extremely high solar wind density (~100 cm<sup>-3</sup>) and mostly strong northward (or eastward) interplanetary magnetic field (IMF) interacted with the Earth’s magnetosphere. We have simulated this event using global MHD models. We study the magnetospheric response to two solar wind discontinuities. The first is characterized by a fast drop of the solar wind dynamic pressure resulting in rapid magnetospheric expansion. The second is a northward IMF turning which causes reconfiguration of the magnetospheric-ionospheric currents. We discuss variations of the magnetopause position and locations of the magnetopause reconnection in response to the solar wind variations. In the second part of our presentation, we present simulation results for the forthcoming SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) mission. SMILE is scheduled for launch in 2024. We produce two-dimensional images that derive from the MHD results of the expected X-ray emission as observed by the SMILE Soft X-ray Imager (SXI). We discuss how SMILE observations may help to study events like the one presented in this work.</p>

Uncertainty estimation of Sentinel-3B tandem data for OLCI-B in the FLEX configuration

<p>During the tandem phase of Sentinel-3A and B the channels of the spectrometer of the Ocean and Land Imager (OLCI) on Sentinel 3-B were reprogrammed to imitate measurements of ESA’s 8<sup>th</sup> Earth Explorer mission FLEX [1]. FLEX is designed to retrieve the complete fluorescence spectrum from the high resolutive visible spectrum and to quantify the contribution of the two photocycles in green plants [2]. Fluorescence is a valuable proxy of plant photosynthesis activity [3], [4]. By measuring the emitted light of plants on satellites, plant distribution and state can be monitored on a global scale.</p><p>The reprogrammed OLCI-B measurements consist of 45 bands between 500 and 800 nm with a bandwidth of about 1.8 nm (FWHM). The spectral and radiometric calibration of the 45 bands has not the same level of maturity as the one for the nominal setting, thus their radiometric uncertainty needs to be quantified. This is done by comparing the 45 FLEX-like bands with the co-located nominal 21 bands of OLCI on Sentinel-3A. The comparison is realised using a transfer function based on radiative transfer simulations. In a first step surface and atmosphere parameters are estimated from the OLCI-B FLEX-like measurements, that explain the measurements. The second step simulates the according OLCI-A measurements at nominal band settings and compares them with the real measurements made by OLCI-A.</p><p>This study serves also as a precursor experiment for the FLEX mission, where the radiometric calibration of FLEX will be verified using co-registered OLCI-A (or B) measurements. Based on this study the strategy for the uncertainty of the FLEX intensity measurements will be developed and tested.</p><p>The uncertainty estimation is a key factor of the Fluorescence retrieval as the Fluorescence contribution to the top of atmosphere signal is very small. To distinguish between signal and noise, the uncertainty must be kept as small as possible. Additionally, the uncertainty serves as input parameter for subsequent retrieval algorithms.</p><p>[1]          M. Celesti et al., ‘In prep.: Sentinel-3B OLCI in “FLEX mode” during the tandem phase: a novel dataset towards the future synergistic FLEX/Sentinel-3 mission’, p. 20, 2020.</p><p>[2]          M. Drusch et al., ‘The FLuorescence EXplorer Mission Concept—ESA’s Earth Explorer 8’, IEEE Trans. Geosci. Remote Sensing, vol. 55, no. 3, pp. 1273–1284, Mar. 2017, doi: 10.1109/TGRS.2016.2621820.</p><p>[3]          W. Verhoef, C. van der Tol, and E. M. Middleton, ‘Hyperspectral radiative transfer modeling to explore the combined retrieval of biophysical parameters and canopy fluorescence from FLEX – Sentinel-3 tandem mission multi-sensor data’, Remote Sensing of Environment, vol. 204, pp. 942–963, Jan. 2018, doi: 10.1016/j.rse.2017.08.006.</p><p>[4]          L. Guanter, L. Alonso, L. Gómez‐Chova, J. Amorós‐López, J. Vila, and J. Moreno, ‘Estimation of solar-induced vegetation fluorescence from space measurements’, Geophysical Research Letters, vol. 34, no. 8, 2007, doi: https://doi.org/10.1029/2007GL029289.</p>

VirES for Aeolus - Virtual Research Environment (VRE)

<p><span>The VirES for Aeolus service (https://aeolus.services) has been successfully running </span><span>by EOX </span><span>since August 2018. The service </span><span>provides</span><span> easy access </span><span>and</span><span> analysis functions for the entire data archive of ESA's Aeolus Earth Explorer mission </span><span>through a web browser</span><span>.</span></p><p><span>This </span>free and open service <span>is being extended with a Virtual Research Environment (VRE). </span><span>The VRE </span><span>builds on the available data access capabilities of the service and provides </span><span>a </span><span>data access Application Programming Interface (API) a</span><span>s part of a </span><span>developing environment </span><span>i</span><span>n the cloud </span><span>using </span><span>JupyterHub and </span><span>JupyterLab</span><span> for processing and exploitation of the Aeolus data. </span>In collaboration with Aeolus DISC user requirements are being collected, implemented and validated.</p><p>Jupyter Notebook templates, an extensive set of tutorials, and documentation are being made available to enable a quick start on how to use VRE in projects. <span>The VRE is intended to support and simplify </span><span>the </span><span>work of (citizen-) scientists </span><span>interested in</span><span> Aeolus data by being able to </span><span>quickly develop processes or algorithms that can be </span><span>shar</span><span>ed or used to create </span><span>visualizations</span><span> for publications. Having a unified constant platform could potentially also be very helpful for calibration and validation activities </span><span>by </span><span>allowing easier result comparisons. </span></p>

Validation of Aeolus winds using radiosonde observations and NWP model equivalents

<p>Aeolus is a European Space Agency (ESA) Earth Explorer mission, launched on 22 August 2018 as part of the Living Planet Programme. Providing atmospheric wind profiles on a global basis, the Earth Explorer mission is expected to demonstrate improvements in the quality of numerical weather prediction (NWP). A crucial prerequisite for the use of meteorological observations in NWP data assimilation systems is a detailed characterization of the quality to minimize systematic observation errors. As part of the German initiative EVAA (Experimental Validation and Assimilation of Aeolus Observations) validation and monitoring activities for Aeolus are performed using collocated radiosonde measurements and NWP forecast equivalents from two different global models, the ICOsahedral Nonhydrostatic model (ICON) of DeutscherWetterdienst (DWD) and the European Centre for Medium-Range Weather Forecast (ECMWF) Integrated Forecast System(IFS) model, as reference data. Systematic differences and bias dependencies are investigated and estimates for the Aeolus instrumental error are determined. Furthermore, impact experiments using the global ICON model are analyzed.    </p><p><br><br></p>

Sulfur Ice Astrochemistry: A Review of Laboratory Studies

Sulfur is the tenth most abundant element in the universe and is known to play a significant role in biological systems. Accordingly, in recent years there has been increased interest in the role of sulfur in astrochemical reactions and planetary geology and geochemistry. Among the many avenues of research currently being explored is the laboratory processing of astrophysical ice analogues. Such research involves the synthesis of an ice of specific morphology and chemical composition at temperatures and pressures relevant to a selected astrophysical setting (such as the interstellar medium or the surfaces of icy moons). Subsequent processing of the ice under conditions that simulate the selected astrophysical setting commonly involves radiolysis, photolysis, thermal processing, neutral-neutral fragment chemistry, or any combination of these, and has been the subject of several studies. The in-situ changes in ice morphology and chemistry occurring during such processing are often monitored via spectroscopic or spectrometric techniques. In this paper, we have reviewed the results of laboratory investigations concerned with sulfur chemistry in several astrophysical ice analogues. Specifically, we review (i) the spectroscopy of sulfur-containing astrochemical molecules in the condensed phase, (ii) atom and radical addition reactions, (iii) the thermal processing of sulfur-bearing ices, (iv) photochemical experiments, (v) the non-reactive charged particle radiolysis of sulfur-bearing ices, and (vi) sulfur ion bombardment of and implantation in ice analogues. Potential future studies in the field of solid phase sulfur astrochemistry are also discussed in the context of forthcoming space missions, such as the NASA James Webb Space Telescope and the ESA Jupiter Icy Moons Explorer mission.