Periodic Reporting for period 2 - IMAGINE (Imprints of Magnetic fields in Exoplanets)
Reporting period: 2022-11-01 to 2024-04-30
The project focuses on the imprints of magnetic fields in exoplanets. This is undertaken by theoretical modeling of the long-term evolution and the dynamo active in the interior, and by comparing these models with the observables where magnetic fields are involved: the inflation of radius observed in some "hot Jupiters" (giant planets orbiting very close to their stars), and the radio emission at very low frequencies (sub-GHz).
The magnetism in exoplanets have been explored at a lesser extent, compared to the Solar system and other astrophysical contexts. We have now had a good characterization of the magnetism in Jupiter, our giant neighbour, whose properties can be a proxy for what we can expect from other stellar systems. Moreover, planets exhibit a huge diversity in terms of dimensions, masses, structure, composition, and distance to the host star.
Bottomline, there is a large space for improvement in the next decade in the context of exoplanetary magnetism.
The overall objectives are to answer the following questions:
How magnetic fields evolve over billions of years, depending on the type of exoplanet?
How the imprints of magnetic fields shape the characteristics of the observed gas giants’ population?
How can we identify the best target for detection of exoplanetary radio emissions?
How the magnetic shielding impacts the terrestrial planets’ habitability?
Besides the scientific aims, a part of the project is dedicated to outreach and teaching activities, with a concrete social impact. In particular, within a regional program, we are working with one of the many public school suffering social segregation, though the designing of activities and training to the teachers, in order to make such a school more attractive.
The magnetism in exoplanets have been explored at a lesser extent, compared to the Solar system and other astrophysical contexts. We have now had a good characterization of the magnetism in Jupiter, our giant neighbour, whose properties can be a proxy for what we can expect from other stellar systems. Moreover, planets exhibit a huge diversity in terms of dimensions, masses, structure, composition, and distance to the host star.
Bottomline, there is a large space for improvement in the next decade in the context of exoplanetary magnetism.
The overall objectives are to answer the following questions:
How magnetic fields evolve over billions of years, depending on the type of exoplanet?
How the imprints of magnetic fields shape the characteristics of the observed gas giants’ population?
How can we identify the best target for detection of exoplanetary radio emissions?
How the magnetic shielding impacts the terrestrial planets’ habitability?
Besides the scientific aims, a part of the project is dedicated to outreach and teaching activities, with a concrete social impact. In particular, within a regional program, we are working with one of the many public school suffering social segregation, though the designing of activities and training to the teachers, in order to make such a school more attractive.
The project is progressing on different lines of research. On one side, we have obtained tens of hours of observations with two of the most advanced radio interferometry facilities: the Giant Meter Radio Telescope (GMRT) and the Karl Jansky Very Large Array. We are analyzing the data, and so far we found a promising polarized radio emission, indicative of strong magnetic fields, in a low-mass binary system. Other observations targeted promising candidates, selected through building a database of the closest, not yet observed in radio exoplanetary systems, to which we associated an estimated magnetic field and radio emission. Such observations are providing so far upper limits which are useful to constrain the model. On the other side, a big part of the project lies on the theoretical side, approaching magnetism via different aspect. We study the fundamental magneto-hydrdynamic scenarios and the dynamo (which is the mechanism to generate and sustain the magnetic fields) in the internal region of giant planets, through the use of the MagIC public code. This is done by evaluating planets at different age and conditions (compositions, irradiation), given by the long-term 1D simulation of a modified version of the MESA public code. Such a code includes a quantitative estimation of the Ohmic dissipation in order to explain the inflation of Hot Jupiters, observed in data. These models rely in turn on the outcome of the dynamo simulations, and on the atmospheric contributions. The latter is related to other 3D simulations of small atmospheric columns representatives of different highly irradiated planets. In this direction, we have found important results, with very large magnetic fields that can be created and maintained via winding mechanism, with some contributions by turbulent effects. All these results represent an important quantitative advance to understand the Hot Jupiters' properties.
The results are recent and we are disseminating them via peer-reviewed articles and in conferences and schools. The team is also very active in outreach, with the participation to tens of events and the organization of several of them.
The results are recent and we are disseminating them via peer-reviewed articles and in conferences and schools. The team is also very active in outreach, with the participation to tens of events and the organization of several of them.
We will have a novel approach of the atmospheric contributions to the magnetic fields in giant exoplanets. What is relevant is that intense magnetic fields can be created due to the thermal winds that drag charged particles in the ionized atmosphere. On the other hand, this project proposes a new methodology to follow how the magnetic field of a planet evolve in the long-term (billions of years), by considering different thermal structures throughout their life, for different ages, masses, compositions and levels of irradiation. Finally, we are trying to connect the dots between the magnetism seen in planets, brown dwarfs and very low-mass stars via radio emission. We aim at constraining better the theoretical models, somehow probably too optimistic so far in terms of likelihood of detection of radio emission from the planets.