Current sheet acceleration of ions in the geomagnetic tail and the properties of ion bursts observed at the lunar distance

Cowley, S. W. H.; Shull, Peter

doi:10.1016/0032-0633(83)90058-2

Cited by 25 publications

(12 citation statements)

References 41 publications

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“…To complete the velocity calculation we take the parallel and perpendicular velocities in after the particle is ejected from the reversal region and transform back to the frame of the x‐line, which yields v = 2.0 b + + v E × B , where b = B / B and v E × B is the E × B drift velocity. This result differs from the well‐known acceleration of ions in a 1‐D current sheet [ Cowley and Shull , 1983] because of the nonadiabatic behavior at the exhaust boundary (see Figures 2 and 4). The reflected particles interpenetrate with particles that have already crossed the boundary of the exhaust but have not passed through the reversal region.…”

Section: Test Particle Trajectories In 1‐d Fieldscontrasting

confidence: 86%

Ion heating resulting from pickup in magnetic reconnection exhausts

et al. 2009

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[1] The heating of ions downstream of the x-line during magnetic reconnection is explored using full-particle simulations, test particle simulations, and analytic analysis. Large-scale particle simulations reveal that the ion temperature increases sharply across the boundary layer that separates the upstream plasma from the Alfvénic outflow. This boundary layer, however, does not take the form of a classical switch-off shock as discussed in the Petschek reconnection model, so the particle heating cannot be calculated from the magnetohydrodynamic, slow-shock prediction. Test particle trajectories in the fields from the simulations reveal that ions crossing the narrow boundary into the exhaust instead behave like pickup particles: they gain both a directed outflow and an effective thermal speed given by the flow speed v 0 of the exhaust. The detailed dynamics of these particles are explored by taking 1-D cuts of the simulation data across the exhaust, transforming to the deHoffman-Teller frame, and calculating explicitly the increment in the temperature, m i v 0 2 /3, with m i , the ion mass. We compare the model predictions with the temperature increment in solar wind exhausts measured by the ACE and Wind spacecraft, confirming that the temperature increment is proportional to the ion mass. The Wind data from 22 high-shear exhaust encounters confirm the scaling of the proton temperature increment with the square of the exhaust velocity. However, the temperature increments are consistently lower than the model prediction. Implications for understanding the production of high-energy ions in flares and the broader universe are discussed.

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Section: Test Particle Trajectories In 1‐d Fieldscontrasting

confidence: 86%

Ion heating resulting from pickup in magnetic reconnection exhausts

et al. 2009

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“…The maximum value of the gained energy for a single particle is ε = 2E Y R Y , where 2 · R Y is the spatial dimension of the magnetosphere in dawn-dusk direction. Particles accelerated in the central region of the CS (or near the X-line) form the distribution with typical "half-ring" structure in the velocity space (V ⊥ , V ) (Lyons and Speiser 1982;Cowley and Shull 1983;Owen and Mist 2001). The thermal velocity of such particles, V T , appears to be much smaller than the average bulk velocity,…”

Section: Modeling Of the Formation Of Type-ii Ion Distribution Functimentioning

confidence: 97%

Non-adiabatic Ion Acceleration in the Earth Magnetotail and Its Various Manifestations in the Plasma Sheet Boundary Layer

et al. 2011

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Many physical phenomena in space involve energy dissipation which generally leads to charged particle acceleration, often up to very high energies. In the Earth magnetosphere energy accumulation and release occur in the magnetotail, namely in its Current Sheet (CS). The kinetic analysis of non-adiabatic ion trajectories in the CS region with finite but positive normal component of the magnetic field demonstrated that this region is essentially non-uniform in terms of scattering characteristics of ion orbits and contains spatially localized, well-separated sites of enhanced and reduced chaotization. The latter represent sources from which accelerated and energy-collimated ions are ejected into Plasma Sheet 134 E.E. Grigorenko et al.Boundary Layer (PSBL) and stream towards the Earth. Numerical simulations performed as part of a Large-Scale Kinetic Model have shown the multiplet ion structure of the PSBL is formed by a set of ion beams (beamlets) localized both in physical and velocity space. This structure of the PSBL is quite different from the one produced by CS acceleration near a magnetic reconnection region in which more energetic ion beams are generated with a broad range of parallel velocities. Multi-point Cluster observations in the magnetotail PSBL not only showed that non-adiabatic ion acceleration occurs on closed magnetic field lines with at least two CS sources operating simultaneously, but also allowed an estimation of their spatial and temporal characteristics. In this paper we discuss and compare the PSBL manifestations of both mechanisms of CS particle acceleration: one based on the peculiar properties of non-adiabatic ion trajectories which operates on closed magnetic field lines and the other representing the well-explored mechanism of particle acceleration during the course of magnetic reconnection. We show that these two mechanisms supplement each other and the first operates mostly during quiescent magnetotail periods.

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“…30,41 The model accounts for two populations of ions in the exhaust, 42 one streaming in from the inflow region and the other already accelerated in the field reversal region at the exhaust's center. Such counter-streaming ion beams have been observed in association with solar wind reconnection.…”

Section: Ion Current Sheetmentioning

confidence: 99%

Current sheets and pressure anisotropy in the reconnection exhaust

Lê

Egedal

et al. 2014

Physics of Plasmas

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A particle-in-cell simulation shows that the exhaust during anti-parallel reconnection in the collisionless regime contains a current sheet extending 100 inertial lengths from the X line. The current sheet is supported by electron pressure anisotropy near the X line and ion anisotropy farther downstream. Field-aligned electron currents flowing outside the magnetic separatrices feed the exhaust current sheet and generate the out-of-plane, or Hall, magnetic field. Existing models based on different mechanisms for each particle species provide good estimates for the levels of pressure anisotropy. The ion anisotropy, which is strong enough to reach the firehose instability threshold, is also important for overall force balance. It reduces the outflow speed of the plasma. V C 2014 AIP Publishing LLC. [http://dx.

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Current sheet acceleration of ions in the geomagnetic tail and the properties of ion bursts observed at the lunar distance

Cited by 25 publications

References 41 publications

Ion heating resulting from pickup in magnetic reconnection exhausts

Ion heating resulting from pickup in magnetic reconnection exhausts

Non-adiabatic Ion Acceleration in the Earth Magnetotail and Its Various Manifestations in the Plasma Sheet Boundary Layer

Current sheets and pressure anisotropy in the reconnection exhaust

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