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The composite image groups two images of a hot corona and coronal rain. Image adjusted from Salome et al. 2006.

Published: 27 February 2025

International Team 545 report

by Joana CarvalhoPatrick Antolin

From the Teams

Solar Wind

Coronal Mass Ejection

Solar Physics

Space Plasma

Towards a deeper understanding of multiphase plasma across astrophysical scales

An international collaboration hosted at ISSI examined the inner workings of multiphase plasma to answer fundamental questions in physics from the Sun to the medium inside galaxy clusters. Their observations of the solar corona, the outermost part of the Sun’s atmosphere, expand our knowledge of the physics of multiphase plasma, and might help us understand the role this phenomenon plays across the universe.

Project Vision

The ISSI International Team #545, led by Dr. Patrick Antolin and Dr. Clara Froment, brought together a multidisciplinary group of experts from eight countries to study multiphase plasmas, and deepen our understanding of the stars.

Multiphase plasma is a type of plasma (super-hot ionized gas) that consists of cool plasmas embedded in a larger, much hotter medium. It exists in the atmospheres of stars and in the space between stars and galaxies, being a key player in energy and mass cycles that characterize these places. This is a type of plasma that affects, for example, the cycles that drive galaxy and star formation, how stars regulate their surface temperature, and how fast they lose mass through their stellar winds.

The properties of multiphase plasmas are very similar between the different places where they occur in the universe, suggesting that the same physics may govern their formation. This similarity is an advantage for researchers. It makes the Sun, the closest star to our planet, a valuable source of information to resolve the physics of multiphase plasma, and help us understand how it works in other stars and at much larger scales in the universe.

Team 545’s two meetings, made possible by ISSI’s International Teams program, were driven by the curiosity to answer three main questions: does multiphase plasma occur in other stars like it does in the Sun? Is the creation of multiphase plasma across astrophysical scales indeed governed by the same physics? What can we learn from the solar corona about thermal non-equilibrium and instability, which produce coronal rain, prominences and long-period EUV pulsations?

Achievements

The team achieved the first simulation of multiphase plasmas in a stellar atmosphere and a demonstration of how these plasmas feed into the stellar wind to create centrifugal atmospheres in the stars.

These findings show that multiphase plasmas can contribute to stellar mass loss, possibly explaining the open question of how stars spin down as they age (slowdown of their rotation over time). The team also detected long-period intensity pulsations at the sources of solar wind, as backed up by numerical modelling, contributing to the idea that multiphase plasma has an important effect on solar and stellar winds.

The team’s findings go further and suggest that the cause of the deceleration of solar multiphase plasma is plasma accumulation (compression) due to the strong magnetic field, different to the pressure drag (the resistive force experienced by an object moving through a fluid due to the differential pressure in the fluid flow around that object) invoked in the intra-cluster medium.

By measuring the mass and energy of multiphase plasma driven by solar flares, the team also showed that they are as energetic as the elusive hot counterpart resulting from the flaring process. This enables multiphase plasmas to be used as proxy for the mechanics of energy transfer during solar flares.

Additionally, the team developed new methods, named RFit/Deep filter, that unlock the possibility of quantifying multiphase plasma over the solar corona and over a solar cycle.

As a result of this project, the team has published 14 papers, one white paper and an editorial collection on the topic.

The instruments on the left correspond to IRIS/NASA and AIA/NASA. Those on the right correspond to Chandra telescope VLA array (top panel from Fabian et al. 2003) and WIYN telescope (bottom panel from Conselice et al., 2001). The middle panel corresponds to Daley-Yates & Jardine (2024).

The instruments on the left correspond to IRIS/NASA and SDO/AIA/NASA. Those on the right correspond to Chandra telescope VLA array (top panel from Fabian et al. 2003) and WIYN telescope (bottom panel from Conselice et al., 2001). The middle panel corresponds to Daley-Yates & Jardine (2024).

Impact

Team 545 combined expertise across fields to investigate the role of multiphase plasma at multiple scales, from the Sun to the regions across galaxy clusters. The understanding gained from the observed processes governing multiphase plasmas in the solar atmosphere allow us to discriminate between competing theories of stellar evolution, and star and galaxy formation.

For more details and a publication list, go to the ISSI Team 545 Webpage.

Credits ESA/Webb, NASA & CSA, A. Martel