Magnetic Reconnection

Magnetic reconnection is a phenomenon that develops in plasmas when a group of magnetic field lines oriented in one direction approaches another group of magnetic field lines antiparallel to them (same direction, opposite way). In between both groups, a current sheet perpendicular to the magnetic field lines is generated. In this set-up, magnetic field lines at both sides of the current sheet can “break” and “reconnect” in the middle with the lines that were originally antiparallel to them. This process can take place in a plasma at the encounter of magnetic field lines from two large scale sources, like in the region where the Sun's and Earth's magnetic fields meet. But magnetic reconnection can also occur between the magnetic field lines generated by the movement of charged particles in a plasma, specially in turbulent ones.

Figure 1: Schematics of the magnetic reconnection process. Credit: Genestreti et al. 2012

Figure 2: Reconnecting current sheet detected in Solar Orbiter data

The change of magnetic field lines topology is not the only sign of magnetic reconnection. The reconnected lines are initially highly curved, but the system tends to decrease this magnetic tension moving these lines away from the reconnection site, so they can straighten. While moving away, the reconnected lines carry particles that entered the reconnection region. These particles are therefore accelerated by the reconnected magnetic field lines and form two opposite plasma jets. Thus, magnetic reconnection is a mechanism that can convert magnetic field energy into kinetic energy.

In our group, we study the reconnection process using data collected in-situ by spacecrafts embedded in the plasma of the heliosphere and the magnetosheath. We have developed an algorithm that permits to detect the presence of thin current sheets and reconnection sites. Our method is the first one to find these structures at small plasma scales, where reconnection might play a major role in the development of turbulence and the dissipation of energy. For the time being, we are using high cadence measurements of Solar Orbiter (SolO) mission, but we are extending our work to other datasets, like the Magnetospheric Multiscale (MMS) mission. By analyzing datasets from different plasma environments we aim to understand the plasma conditions that triggers magnetic reconnection at small scales in a astrophysical plasmas.