title: Ion temperature anisotropy across a magnetotail reconnection jet.
abstract: A significant fraction of the energy released by magnetotail reconnection appears to go into ion heating, but this heating is generally anisotropic. We examine ARTEMIS dual-spacecraft observations of a long-duration magnetotail exhaust generated by antiparallel reconnection in conjunction with particle-in-cell simulations, showing spatial variations in the anisotropy across the outflow far (>100di) downstream of the X line. A consistent pattern is found in both the spacecraft data and the simulations: While the total temperature across the exhaust is rather constant, near the boundariesTi,||dominates. The plasma is well above the firehose threshold within patchy spatial regions at |BX|∈[0.1,0.5]B0, suggesting that the drive for the instability is strong and the instability is too weak to relax the anisotropy. At the midplane ( |BX|≲0.1B0),Ti,⊥>Ti,||and ions undergo Speiser-like motion despite the large distance from the X line.
authors.affiliation: The Blackett Laboratory Imperial College London UK.
authors.forename: H
authors.identifier: 0000-0002-3039-1255
authors.initials: H
authors.lastname: Hietala
authors.affiliation: Department of Physics, the Institute for Physical Science and Technology and the Joint Space Institute University of Maryland College Park Maryland USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Drake
authors.affiliation: Space Science Laboratory University of California Berkeley California USA.
authors.forename: T D
authors.initials: TD
authors.lastname: Phan
authors.affiliation: The Blackett Laboratory Imperial College London UK.
authors.forename: J P
authors.initials: JP
authors.lastname: Eastwood
authors.affiliation: Space Science Laboratory University of California Berkeley California USA.
authors.forename: J P
authors.initials: JP
authors.lastname: McFadden
keywords: ion heating; magnetic reconnection; magnetotail; temperature anisotropy