The COROSHOCK project will address one of the remaining unsolved fundamental problems in solar physics: how are solar particles accelerated to high energies? The origin(s) of Solar Energetic Particles (SEPs) and of high-energy electromagnetic radiations such as ? rays are still highly debated. Two main particle-energisation mechanisms proposed are diffusive-shock acceleration ahead of expanding Coronal Mass Ejection (CMEs) and reconnection occurring in solar flares situated below CMEs and likely involved in the formation process of magnetic flux ropes. Comparison of in-situ measurements near 1AU and remote-sensing observations of the corona show that particle acceleration to high energies (> 1 GeV) occurs in the first tens of minutes of the initiation of a CME in the solar corona somewhere below 5 solar radii (Rs), a region that is not yet accessible to in-situ measurements. The onset of solar ?-ray events also occurs during these first minutes and are measured near Earth by the Fermi satellite. ?-rays are produced by the highest energy ions and electrons accelerated at the Sun and they provide our only direct (albeit secondary) knowledge about the properties of the accelerator(s). ?-rays measured from Earth’s perspective could be produced by shock-accelerated particles propagating sunwards and impacting the solar chromosphere visible from Earth (Cliver et al. 1996) or else from particles trapped on coronal loops. Another puzzle relates to the origin of Long Duration Gamma Ray Flares that can last several hours to several days well after the impulsive phase of solar flares and at times when the associated CME is already far away from the Sun. Long duration flares suggest that a particle-acceleration mechanism operates over many hours to produce energetic protons that stream continually towards the solar surface. The COROSHOCK project focuses mostly on evaluating the role of coronal shocks as strong accelerators of the energetic particles that form the SEPs measured in situ near 1AU and the high-energy electromagnetic radiations observed near the Sun. The fundamental questions to be addressed are: Q1: Is the variability and long-duration of gamma ray events controlled by the 3-D evolution of shock waves? Q2: Can particle acceleration at coronal shocks explain simultaneously the properties of SEPs and LDGRFs? We will test the shock hypothesis as the prime particle accelerator by adapting existing advanced numerical models and exploiting remote-sensing and in-situ data in an integrated manner. The COROSHOCK projects aims at combining our advanced coronal shock models with models that account for the physical processes known to operate in the corona and interplanetary medium during the transport of particles and the conversion of energised beams of particles into electromagnetic radiations. The project will not develop new models of the microphysics of particle acceleration but instead exploit existing diffusive-shock acceleration models to derive a parameterisation of particle production based on the properties of coronal shocks. The ultimate aim of the project is to determine how well we can reproduce the spectra and time-varying fluxes of particles and electromagnetic particles measured near 1AU. Our ambitions are technically challenging and require to connect widely different datasets and develop new techniques that go well beyond the current state-of-the-art. COROSHOCK will take full advantage of spaceborne and ground-based remote-sensing observations of the solar corona and integrates in a comprehensive way in-situ measurements of the thermal and non-thermal particles transported in the solar wind. COROSHOCK is tailored to exploit currently available missions if the planned NASA Solar Probe Plus, ESA PROBA-3 and ESA Solar Orbiter instrumentation provide as scheduled new data, these will be directly integrated in the analysis during the later phase of the project (2019-2021).

The Parker Solar Probe (PSP), launched in 2018, has unraveled a much more dynamic solar wind than expected by previous theories and observations. In particular, it has observed many magnetic field reversals, associated with velocity jets, during its perihelia. These so-called ‘switchbacks’, have been studied extensively since their discovery, but their origin remains unknown. They could be related to the two main theories of coronal heating and solar wind acceleration. They are indeed fully part of the solar wind turbulence spectra. Turbulence creates dissipation at small scales and is believed to be the main source of energy for the expanding solar wind. Interestingly, PSP data has also revealed characteristic scales close to the Sun’s surface motions, which suggests that switchbacks' origin could be related to reconnection in the low corona. This eruptive events are the main alternative theory to turbulence, to explain coronal heating. This project aims at studying the emergence and evolution of these structures, using numerical simulations and observations from PSP and the European solar mission Solar Orbiter. We will model the reconnection process in the low corona and study, through MHD simulations, the propagation of these structures in realistic solar wind solutions. We will use in-situ and remote sensing observations to study the sources of the switchbacks and their properties. The project relies on the numerical expertise of the PI and on the ideal position of IRAP on both missions, which is heavily involved in several instruments: co-I PSP/SWEAP and PSP/WISPR, PI of SO/PAS, co-I of SO/MAG and SO/HIS. The project plans at hiring one PhD student for 3 years and one postdoc for 2 years.

This project tackles the problem of the transport of angular momentum (AM) in stellar interiors, which is one of the most challenging issues faced today by stellar physics. Our poor understanding of the AM redistribution inside stars is a barrier to the modeling of stellar formation and evolution. The seismology of red giants has recently demonstrated that it can spectacularly contribute to making progress on this issue. The detection in the oscillation spectra of red giants of so-called mixed modes, which probe both the stellar core and the envelope, has made it possible to seismically measure their internal rotation. This has brought clear evidence that an additional mechanism of AM transport takes place in subgiants and red giants, the origin of which is unknown. In this project, we will thoroughly investigate whether this AM redistribution has a magnetic origin, which is one of the main scenarios that have been proposed. For this purpose, we will combine asteroseismology, spectropolarimetric observations, and state-of-the-art multidimensional MHD simulations. We will exploit the exquisite seismic data from the Kepler satellite to bring tight constraints on the time during the evolution and the timescale over which the episodes of AM redistribution occur. The cases of low-mass and intermediate-mass stars, which have qualitatively different evolution in the post-main-sequence, will both be addressed. By improving seismic inversion methods, we will also obtain constraints as localized as possible on the shape of the internal rotation profiles that result from this transport. These observations will yield key information to discriminate between the potential transport mechanisms. To test more particularly the hypothesis of a magnetically-induced transport of AM, we will seismically measure the rotation profiles of Kepler red giants for which an internal magnetic field can be detected and characterized (strength and topology). Using spectropolarimetric observations, we will identify among Kepler targets the descendants of so-called Ap stars, which harbor strong internal magnetic fields during the main sequence. We will also search for the seismic signature of internal magnetic fields in red giants, by attempting to measure the magnetic splitting of oscillation mode. Through numerical simulations, we will investigate the interaction between differential rotation and magnetic fields in red giants. We will first study the differential rotation produced by the core contraction and envelope expansion alone. By introducing magnetic fields, we will then determine the conditions under which different types of MHD instabilities could occur in the radiative interior of red giants and we will precisely estimate their efficiency at transporting AM. This will enable us to provide prescriptions for magnetically-induced AM transport with strong physical basis to be used in a new generation of 1D stellar evolution models. Direct comparisons will be performed between the predictions of these models and seismic inferences on the rotation of red giants. The Kepler targets for which we will have measured the topology and amplitude of the internal magnetic field will yield the most critical tests of the magnetic origin of AM transport in red giants.

With more than 5300 exoplanets detected so far, it is clear that planet formation is a robust and efficient process. The current population of known exoplanets exhibits a wide diversity, both in nature (mass, radius) and in architecture: while giant planets can be found at large separations, the most common type of exoplanetary systems revealed by Kepler transits consist of chains of low-mass planets, super-Earths and mini-Neptunes, located close to their host stars. To understand the origin of this diversity, we need to explore the birth environment of the planets, namely the planet-forming protoplanetary disks, and to investigate their structure and evolution on both local and global scales. While considerable progress has recently been made in probing the disks on large scales (a few tens of astronomical units, au), little is known about the innermost regions (less than a few au). The IRYSS (Innermost Regions of Young Stellar Systems) project aims at deciphering the processes at play in the innermost regions of protoplanetary disks (PPDs). For the first time, we will provide a statistical view of the inner parts of a large sample of PPDs, thus bringing to light the main missing piece in our understanding of planet formation. The project builds on the unique synergy between the observational approaches developed by the partners, IPAG and IRAP, on national Research Infrastructures such as ESO/VLTI (with the PIONIER and GRAVITY interferometric instruments, largely developed at IPAG) and CFHT (with the ESPaDOnS and SPIRou spectropolarimeters, both developed at IRAP), in combination with the development of advanced physical models of the inner disk edge and of the accretion flows onto the central star. Benefiting from these world-class facilities, which are at the heart of the orientations of the call, we will conduct a multi-wavelength, multi-technique, and multi-scale investigation of the inner disk regions in a few tens of young stellar systems. We will explore the initial and environmental conditions that prevail at the time of planet formation by addressing three intrinsically interconnected pillars: 1) the morphological (asymmetry, vortex, dead zone) and physical (temperature, density) properties of the innermost scales of the protoplanetary disk, by spatially resolving at the sub-au level the near- and mid-infrared continuum emission with interferometry; 2) the magnetic star-disk interaction region, extending over a few stellar radii, and whose outer edge is thought to be the place where inwards migrating planets pile up, with spectropolarimetric observations and Zeeman-Doppler Imaging to derive the magnetic field topology and strength; 3) the dynamical timescales of the physical processes from a few days to months, by monitoring the variability of both the magnetic topology and the small-scale disk features. The combined analysis of these data sets arising from these two state-of-the-art observational techniques will put the world-leading French experts in a unique position to provide the stellar and exoplanet communities with legacy databases of magnetic maps, line profiles, inner rim positions and disk substructures. These are the key ingredients to relate the magnetic properties of young stars to the structure of their inner disk, and to investigate their evolution over periods as long as 10 years for some emblematic objects. As such, this legacy will provide access to a detailed overview of the innermost regions of nascent stellar systems and their disks where close-in planets form. Our team has access to all the ESO and CFHT Large Program and Guarantee Time observations to be exploited in the IRYSS project, and has developed during previous ERC-funded grants cutting-edge analysis and modeling tools required for their interpretation. We therefore gather the optimal expertise to yield major advances in this competitive field, supported by the appropriate workforce provided by this specific and quite timely ANR call.

Magnetic reconnection is a universal phenomenon enabling large scale transfer of magnetic energy to plasma kinetic energy and affecting its macroscopic transport by changing its magnetic connectivity. Among many systems in the universe, the Earth magnetopause, being close and “easily” targeted by spacecraft missions, is a fantastic laboratory to study the reconnection process in great details, besides being, by itself, an important space weather actor, as reconnection there critically couples the solar wind to our magnetosphere, leading to geomagnetic activity. The magnetopause is a three-dimensional collisionless asymmetric magnetic boundary separating the solar wind from the magnetospheric plasma, and through which the magnetic field is sheared between the interplanetary magnetic field (IMF) and the Earth dipole. Although we know magnetopause reconnection is overall greatly influenced by the IMF orientation, we do not understand how the magnetic shear affects the microphysics resulting in this large scale perspective. Besides the asymmetrical magnetopause configuration distinguishes it from the majority of reconnection models, mostly focused on magnetotail-like, symmetric current sheets, which guide our intuition although, strictly speaking, are quite singular. This three year project proposes to tackle the crucial issue of the impact of mesoscale environmental properties on collisionless magnetic reconnection, focusing on the impact of i) varying the magnetic shear angle in a fixed, asymmetric, reconnecting current sheet ii) the impact of a slowly varying degree of asymmetry of the current sheet on the reconnection process with a fixed magnetic shear and iii) the three-dimensional aspect of the problem. Such a systematic survey will lead to much clearer results than the simulation of a unique and arbitrary shear angle and high degree of asymmetry. We will use state-of-the-art 2D fully and hybrid kinetic simulations, later confronted to 3D kinetic and fluid simulations, and always in a close relationship with multi-mission space observations, at the magnetopause and in the solar wind, making an heavy use of innovative tools developed at the Institute for Research in Astrophysics and Planetology (IRAP), improving them and developing new ones. In october 2014, NASA will launch the major mission Magnetospheric MultiScale (MMS) to study the reconnection microphysics down to electron scales, and will explore the dayside magnetopause during its first phase. Our ambitious objectives are highly relevant to the MMS science priorities and very competitive. They will be reached by the gathering of the complementary strengths of the French space plasma community in theory, numerical modeling and space observations, together with the world leading experts in reconnection physics and its kinetic modeling, in a new and strong international collaboration, on a cross-disciplinary topic that is widely recognized as one of the most important and challenging one in experimental, spatial and astrophysical plasma communities. The project will be mainly performed at IRAP, but will also involve researchers from the Laboratory of Plasma Physics (LPP) and NASA Goddard Space Flight Center (GSFC). If the latter, building the MMS four satellites is obviously deeply engaged in the mission, IRAP and LPP are also strongly involved, as they both contribute to the spacecraft instrumentation. This project is at the heart of the IRAP Geophysical and Space Plasma group’s scientific activities, to which it will bring, as well as to the French astrophysical plasma community as a whole, a highly desirable expertise on numerical modeling of collisionless magnetic reconnection. It will be decomposed in five tasks, among which the coordination one and four scientific tasks based on a very strong theory/observation/simulation synergy and designed to deliver key results on reconnection physics, original databases, codes and innovative observational tools for the community.