Phase Diagram For Magnetic Reconnection in Heliophysical, Astrophysical, and Laboratory Plasmas
Authors: Hantao Ji and William Daughton
Abstract:
Recent progress in understanding the physics of magnetic reconnection is conveniently summa-
rized in terms of a phase diagram which organizes the essential dynamics for a wide variety of
applications in heliophysics, laboratory and astrophysics. The two key dimensionless parameters
are the Lundquist number and the macrosopic system size in units of the ion sound gyroradius.
In addition to the conventional single X-line collisional and collisionless phases, multiple X-line
reconnection phases arise due to the presence of the plasmoid instability either in collisional and
collisionless current sheets. In particular, there exists a unique phase termed \multiple X-line
hybrid phase" where a hierarchy of collisional islands or plasmoids is terminated by a collision-
less current sheet, resulting in a rapid coupling between the macroscopic and kinetic scales and a
mixture of collisional and collisionless dynamics. The new phases involving multiple X-lines and
collisionless physics may be important for the emerging applications of magnetic reconnection to
accelerate charged particles beyond their thermal speeds. A large number of heliophysical and
astrophysical plasmas are surveyed and grouped in the phase diagram: Earth's magnetosphere,
solar plasmas (chromosphere, corona, wind and tachocline), galactic plasmas (molecular clouds,
interstellar media, accretion disks and their coronae, Crab nebula, Sgr A*, gamma ray bursts,
magnetars), extragalactic plasmas (Active Galactic Nuclei disks and their coronae, galaxy clus-
ters, radio lobes, and extragalactic jets). Signi cance of laboratory experiments, including a next
generation reconnection experiment, is also discussed.
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Submitted to: Physics of Plasmas (June 2011)
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Download PPPL-4712 (pdf 3.33 MB 27 pp)
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