Solar Terrestrial ObseRvations and Modeling Service


The origin of stellar winds, and here in particular the slow solar wind is still debated. To date no model of the solar atmosphere has yet explained at the same time the bulk and compositional properties of the fast and slow solar winds. We will develop the first 3-D model of coronal ions solving, along realistic magnetic field lines topologies, for the coupled transport of important major and minor constituents. The model will compute dynamically for the emissions and the plasma moments of the different particles. This new modeling framework will provide a wealth of new observational tests to evaluate the different theories for the origin of SSW exploiting readily available data.
SLOW_SOURCE will be unique in that it will link some detailed physics occurring at the top of the chromosphere with the global 3-D corona and the solar wind. We will compare our simulation results with in situ and remote-sensing data (ACE, Wind, STEREO, SoHO, SDO) as well as Parker Solar Probe (SWEAP, FIELDS, WISPR, first data in November 2018 at 35,7 solar radii from the Sun).

The fundamental questions that will be addressed during the project are:

Question 1: Can the SSW bulk properties and composition be explained by quasi steady-state processes?
Question 2: Can the remote observations of the SSW source region be explained by steady-state theories?
Question 3: What causes variations in He abundance and the strong FIP effect in the SSW in steady state?
Question 4: What causes the variability of the SSW?
Question 5: Can we produce a self-consistent model of the SSW?

The SLOW_SOURCE project is a 5-year project (2019-2024) selected and funded by the European Research Council (ERC Consolidator 2018 call)

Background Information

The solar winds measured in situ have been classified in at least two types based on their bulk properties: “fast” (>500 km/s) wind from coronal holes and the “slow” (`<`500 km/s) solar wind (SSW) of enigmatic origin. The winds originate in the solar corona, a multi-species, multi-temperature magnetised plasma heated by yet undetermined processes. The trace elements (minor heavy ions) transported in the winds exhibit peculiar properties that are suspected signatures of the fundamental plasma processes at play during the heating of the corona and the release process of the wind. For example, spectroscopic observations show that the abundance of a subset of these minor ions, those with low First Ionisation Potential (FIP) (such as Mg, Si, Fe), is much higher in the solar corona than in the photosphere.
Since the magnitude of this ‘FIP effect’ in closed field regions of the corona is similar to that measured in the SSW, it has been argued that the SSW forms by the release onto open magnetic field lines of plasma initially confined to closed field regions of the corona (dynamic theory of the SSW). An alternative theory (here termed ‘quasi-steady state’) suggests that the SSW exists regardless of these magnetic reconfigurations and is formed along open magnetic flux tubes that undergo strong expansion between the photosphere and the upper corona. The fractionation of elements according to their ionisation potential is also seen in other stellar coronae and the process reduces as one moves to later spectral types with measured inverse-FIP effects detected seldomly in the solar corona and frequently on M-type stars.

Team Members


IRAP Staff:

  • PI: Alexis Rouillard
  • PhD Student: Nicolas Poirier
  • Postdoc: Léa Griton
  • Web developper: Matthieu Alexandre

  • Pierre-Louis Blelly
  • Philippe Louarn
  • Benoit Lavraud
  • Laurène Jouve
  • Pascal Petit
  • Frédéric Paletou

External Collaborators:

  • Angelos Vourlidas (JHAPL)
  • Nour-Edine Raouafi (JHAPL)
  • Russ Howard (NRL)
  • Viviane Pierrard (UCL)
  • Christian Vocks (AIP)
  • Martin Laming (NRL)
  • Justin Kasper (Uni. Michigan)
  • Marco Velli (UCLA)