New tools to study the magnetic field of the Sun

 The Astrophysical Spectropolarimetry research project, conducted by Renzo Ramelli of the Aldo and Cele Daccò Solar Research Institute (IRSOL) affiliated to USI, has been approved by the Swiss National Science Foundation (SNSF). The aim of the project is to study the evolution and structure of the solar magnetic field, with particular attention to the formation of solar flares, thanks to modern instruments and innovative observation techniques. Researchers from SUPSI, FHNW (Fachhochschule Nordwestschweiz) and KIS (Leibnitz-Institut für Sonnenphysik) also participate as partners in the project.

Renzo Ramelli, what does the project consist of?

The research project will be conducted by the IRSOL observational research group, in collaboration with the other two groups dedicated to theory and numerical simulations. The solar magnetic field will be studied through high-precision spectro-polarimetric observations which make it possible to trace the structure of the solar magnetic field in detail, to establish its evolution and to validate the theoretical models of the solar atmosphere that are being developed in current research .

This provides a better understanding of manifestations of solar activity, such as the eleven-year solar cycle, flares or coronal mass ejections, in which magnetism plays a major role. The phenomena studied can lead to the formation of solar storms which, if particularly intense, can have a strong impact on the functioning of our technologies, interrupting radio telecommunications, damaging exposed electronic equipment and creating blackouts in the electricity distribution networks.

What are the objectives of the study?

The main objective of the research is to study with modern instruments and innovative observational techniques the evolution and structure of the solar magnetic field on scales corresponding to the limit of capabilities in terms of spatial resolution of modern solar telescopes. This will allow to address the debated question of the solar dynamo, whose existence and characteristics have a huge impact on solar and stellar physics, such as energy transport and the energy balance of the Sun.

The results of the study will lead to a better understanding of solar magnetism providing useful knowledge to improve the predictive capabilities of solar storms.

The acquired knowledge can also be reinvested in stellar astrophysics research. The spectropolarimetric instrumentation that will be perfected may also have applications in other research fields, such as an in-depth study of solar flares, taking advantage of the recent improvements in the IRSOL instrumentation and the greater efficiency of the ZIMPOL high-precision polarimeter.

What tools will be used?

The spectro-polarimetric observations will be performed with the high precision ZIMPOL polarimeter which can reach an accuracy of 10-5 in fractional polarization units. The observations will be carried out with the Gregory Coudé Telescope (GCT) at IRSOL in Locarno and with the largest European telescope GREGOR in Tenerife, where the permanent installation of the ZIMPOL system is planned. Measurements with GREGOR are especially important when high spatial resolution plays an essential role in addressing scientific questions. The observations will also benefit from a new observation technique, based on the combination of slow and fast modulation, just developed and implemented at IRSOL within the SOLARNET H-2020 project. The technique drastically reduces systematic effects in polarization measurements and allows for unprecedented accuracy in absolute polarization which is a major advantage over other solar observatories. This technique has been successfully tested by our group in collaboration with KIS also at GREGOR, pushing IRSOL to a leading role in this research sector.

For observations of solar flares, the project involves joint observations with the GCT, GREGOR and the Spectrometer/ Telescope for Imaging X-rays (STIX) aboard the Solar Orbiter.

The project also envisages an improvement of the ZIMPOL spectropolarimeter in collaboration with the Department of Innovative Technologies (DTI) of SUPSI (Institute for Systems and Applied Electronics).

What could be the implications of this research at national and international level?

This project will contribute to the development of new techniques that can be exploited by the new generation of telescopes, such as the European Solar Telescope (EST), giving Switzerland the opportunity to play an important role on the world scientific scene and fostering collaborations within the growing solar physics community in Switzerland.

Among the various objectives is to improve magnetic field diagnostic techniques that could increase the ability to predict space weather events that impact the Earth, and to produce a new version of the Second Atlas of the Solar Spectrum, which includes the change from center to edge and which will become a new reference in the field.

With this project we intend to maintain a world leadership role in solar spectropolarimetry. The observing techniques we are developing are of interest to the new generation of solar telescopes such as the European Solar Telescope (EST). IRSOL already participates with its know-how in polarimetry in the preparatory activities of the EST project (for example in the context of H2020-SOLARNET with the development of the observation technique which combines fast and slow modulation to obtain absolute polarimetric precision without earlier). Thanks to IRSOL, Swiss institutions and companies can access these important projects.

The joint flare-observing program with the FHNW will open up new synergies within the growing Swiss solar science community. It will also increase the scientific output of the Solar Orbiter mission in Switzerland.

We are also convinced that this project offers interesting training opportunities. A doctoral student and a post-doctoral student will have the opportunity to carry out a fascinating and original research project. Based on what has been experienced in past years, the topics covered also attract university students for the creation of small, well-defined sub-projects. Interesting technical projects can also be awarded to students of universities of applied sciences. Many stimulating topics related to the project also lend themselves to promoting dissemination activities and will be included in the dissemination project Agorà "Il Sole", recently approved for funding by the SNSF. This Agorà dissemination project provides in particular for the setting up of an exhibition at USI's L'ideatorio.

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