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Magnetic fields get reconnected in turbulent plasma too, Cluster reveals

27 March 2007

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This image provides a model of magnetic fields at the Sun's surface using SOHO data, showing irregular magnetic fields (the ‘magnetic carpet’) in the solar corona (top layer of the Sun's atmosphere). Small-scale current sheets are likely to form in such turbulent environment and reconnection may occur in similar fashion as in Earth's magnetosheath. This can be relevant to a better understanding of the heating of solar corona.

Credits: Stanford-Lockheed Inst. for Space Research/NASA GSFC

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Small-scale magnetic reconnection seen by Cluster

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Top: this illustration shows the Earth’s magnetosphere with the orbit of the Cluster flotilla depicted by a red line. The bow shock is seen compressed on the day-side by the solar wind. The magnetosheath is the boundary layer between the bow-shock and the magnetosphere.

Bottom: Schematic diagram of the current-sheet formation between magnetic islands and of magnetic reconnection in the current sheet.

On 27 March 2002, the constellation of Cluster spacecraft (maintaining an inter-spacecraft distance of only 100 kilometres) have observed reconnection within a very thin current ‘sheet’ embedded in the turbulent plasma in the magnetosheath. The observations show that the turbulent plasma is accelerated and heated during the reconnection process. This newly discovered type of small-scale reconnection seems to be associated with the acceleration of particles to energies much higher than the average, which could explain, in part, the creation of high energy particles by the Sun.

Cluster’s observations provided the first direct measurements of small-scale plasma turbulence, opening up new perspectives to help us better understand the behaviour of turbulent plasma.

Credits: Courtesy of Alessandro Retinò (image modified by ESA)

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Schematic of magnetic field lines during reconnection

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In a plasma (a gas of charged particles), during magnetic reconnection, magnetic field lines of opposite direction break and then reconnect, forming an X-line magnetic topology. The newly reconnected field lines accelerate the plasma away from the X-line.

Credits: Center for Visual computing, Univ. of California Riverside

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This animation shows an active region with loops and an X-type solar flare on the solar surface as imaged by ESA/NASA’s SOHO satellite in November 1997.

Credits: ESA/NASA, SOHO/EIT

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Cluster overview Double Star overview SOHO overview Solar Orbiter Space weather

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