In a recent article published in the journal Nature, scientists including a researcher from IRAP (Université Paul Sabatier de Toulouse & CNRS) discovered a new type of magnetic process, closely associating magnetic reconnection and turbulence, by studying data from NASA’s Magnetospheric MultiScale (MMS) space mission.
Magnetic reconnection is one of the most important processes in near-Earth space, filled with charged particles (called plasma). This fundamental process dissipates the magnetic energy and accelerates the particles, through an explosive reconfiguration of the magnetic field in the medium. The importance of this process stems from its predominance in all astrophysical plasmas, from the near-Earth environment to the galaxies, including the Sun of course. Magnetic reconnection is also one of the key processes for understanding and accurately modeling the Sun-Earth relationship, with the ultimate goal of forecasting space weather.
The discovery presented in this paper demonstrates the importance of magnetic reconnection at scales previously inaccessible, namely the electronic scale in a turbulent plasma. As stated by the main authors of the paper in their interventions with the media, this study also shows an unexpected connection between magnetic reconnection and turbulence, a second fundamental process in astrophysical plasmas.
Although magnetic reconnection has been observed many times, the event studied here takes place in the magnetogaine, an extremely turbulent solar wind compression zone just outside the Earth’s magnetosphere. Until now, scientists did not know whether magnetic reconnection could develop there when this region is very turbulent. MMS has demonstrated this at scales that no other mission could have probed.
Unlike “standard” magnetic reconnection, for which plasma jets are observed on large scales (thousands of km), the “turbulent” reconnection highlighted in this study ejects electron jets with thicknesses of the order of a few kilometres. The most irrefutable evidence comes from the observation, by two distinct MMS satellites, of electron jets in opposite directions coming from a reconnection site located between them. Moreover, only small-scale jets are observed during this event, suggesting that the turbulent nature of the magnetogaine does not allow the development of large-scale jets. These observations have strong implications for all astrophysical plasmas in which magnetic reconnection and turbulence are at work, and potentially associated.
About the MMS mission
NASA’s MMS mission consists of four satellites in a tetrahedral configuration, in line with ESA’s Cluster mission, but with very small inter-satellite distances (10 km compared to ~100-1000 km for Cluster) to study the process of magnetic reconnection at electronic scales. Thanks to an elliptical equatorial orbit of 1.2 x 12 Earth’s radii, MMS targets the key regions of the Earth’s magnetosphere where the process occurs, namely firstly the magnetopause on the day side and the plasma layer on the night side, but also the magnetogaine as in the case of this study.
IRAP has contributed to the MMS mission through the provision, testing and calibration of the set of microchannel detectors (32 for the flight models) for the Dual Ion Sensors (DIS) instruments that are part of the Fast Plasma Investigation (FPI) instrument suite.
- Scientific article : “Electron magnetic reconnection without ion coupling in Earth’s turbulent magnetosheath” par T.D. Phan et al, https://www.nature.com/articles/s41586-018-0091-5
- Other resources :
- Press Release : NASA Satellites Make Magnetic Discovery in Turbulent Space Near Earth
- Benoit Lavraud, firstname.lastname@example.org
- Other IRAP researchers : Jean-André Sauvaud, Iannis Dandouras, Sid Fadanelli, Gabriel Fruit, Vincent Génot, Christian Jacquey, Issaad Kacem, Philippe Louarn, Aurélie Marchaudon, Emmanuel Penou, Yoann Vernisse.