Sun – Earth Relations

The three main issues we are working on are :

1) How is the solar wind heated and accelerated?

2) How to better predict the impact of solar irradiance on our atmosphere?

3) How to better quantify the role of the Sun in climate variations?

1) How is the solar wind heated and accelerated?

The solar wind that flows pas the Earth is a formidable laboratory of astrophysics, which reproduces on small scales physical processes that occur elsewhere in the universe on much larger scales. The study of the solar wind confronts us with one of the major questions of contemporary physics: how is this wind that emanates from the Sun (whose surface is around 6000º C) accelerated and heated to temperatures exceeding one million degrees C?

With the upcoming launch of the Solar Orbiter (ESA, 2020), Parker Solar Probe (NASA, 2018) and BepiColombo (ESA / JAXA, 2018) satellites, we are expecting a rich harvest of in situ measurements in the solar wind with our magnetic sensors (on Solar Orbiter and Parker Solar Probe) and a mutual impedance probe (on BepiColombo). In particular, Parker Solar Probe will be the first satellite to dive into the solar atmosphere, in the region where the solar wind is accelerating.

These solar wind observations will be compared with outputs from theoretical models, and in particular with simulations of beam-plasma interactions that describe how waves associated with the propagation of electron beams are generated in inhomogeneous plasmas.

 

Simulation of the electric field (in nondimensional units) associated with the encounter of a modulated Langmuir wave in the solar wind.

One of our fields of expertise is the development of data analysis techniques involving  wavelet transforms and blind source separation. These techniques allow us to better understand the role of coherent structures within the turbulence of the solar wind.

2) How to better predict the impact of solar irradiance on our atmosphere?

The Earth’s space environment is constantly exposed to variations in solar activity, some of which may have a direct impact on us and on technological devices: satellite malfunction, outages in radio communications, loss of GPS location, etc. An emerging discipline, called space weather, aims at better understanding and predicting these variations of solar activity.

Thanks to several European collaborative projects (SOTERIA, ATMOP, SOLID), we have developed new skills in studying the variability of solar irradiance (especially in the ultraviolet) and its impact on the Earth’s upper atmosphere. In particular, we have highlighted the systematic and dominant character of visible light radiation in the total energy of solar flares.

We are now using this expertise to develop operational products for space weather, and in particular new solar activity tracers to improve satellite orbit forecasting. These studies are done in partnership with CNES (http://spaceweather.cls.fr) and as part of the Space Situational Awareness programme.

3) How to better quantify the role of the Sun in climate variations?

By analogy with classical meteorology, space climate aims at better understanding the conditions of space environment on time scales of years and beyond. One of the big issues is the contribution of solar variability to recent global warming.

To address this controversial but also complex question, we coordinated from 2011 to 2015 an European network (TOSCA COST Action) to evaluate the role of all known mechanisms. In particular, we contributed to the reconstruction of solar activity from 1850 to today; these data will serve as a reference for the next IPCC assessment report.

 

Comparison between several reconstructions of solar radiative forcing (total irradiance). The black curve is the new reference.

Contact LPC2E: Thierry Dudok de Wit (ddwit@cnrs-orleans.fr)