A computational study of nonresonant cross-field diffusion of energetic particles due to their interaction with interplanetary magnetic decreases

Costa, Edio da; Echer, E.; Alves, M. V.; Tsurutani, B. T.; Simões, F.J.R.; Cardoso, F. R.; Lakhina, G. S.

doi:10.1016/j.jastp.2011.01.022

Cited by 5 publications

(5 citation statements)

References 31 publications

(26 reference statements)

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“…The interaction will not be the typical “cyclotron resonant” ones, but charged particles will also be scattered perpendicular to the magnetic field. We refer the interested reader to Tsurutani et al [1999b], Tsurutani and Lakhina [2004], and Costa et al [2011]. This “cross‐field diffusion” could have significant implications for particle circulation in our heliosphere.…”

Section: Discussionmentioning

confidence: 99%

Magnetosheath and heliosheath mirror mode structures, interplanetary magnetic decreases, and linear magnetic decreases: Differences and distinguishing features

et al. 2011

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[1] There has been considerable confusion in the literature about what mirror mode (MM), magnetic decrease (MD), and linear magnetic decrease (LMD) structures are and are not. We will reexamine past spacecraft observations to demonstrate the observational similarities and differences between these magnetic and plasma structures. MM structures in planetary magnetosheaths, cometary sheaths, and the heliosheath have the following characteristics: (1) the structures have little or no changes in the magnetic field direction across the magnetic dips; (2) the structures have quasiperiodic spacings, varying from ∼20 proton gyroradii (r p ) in the Earth's magnetosheath to ∼57 r p in the heliosheath; and (3) the magnetic dips have smooth edges. Magnetosheath MM structures are generated by the mirror instability where b ? /b k > 1 + 1/b ? (b is the plasma thermal pressure divided by the magnetic pressure). In general, the sources of free energy for the mirror instability are reasonably well understood: shock compression, field line draping, and, in the cases of comets and the heliosheath, also ion pickup. The observational properties of interplanetary MDs are as follows: (1) there is a broad range of magnetic field angular changes across them; (2) their thicknesses can range from as little as 2-3 r p to thousands of r p , with no "characteristic" size; and (3) they typically are bounded by discontinuities. The mechanism(s) for interplanetary MD generation is (are) currently unresolved, although at least five different mechanisms have been proposed in the literature.

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Section: Discussionmentioning

confidence: 99%

Magnetosheath and heliosheath mirror mode structures, interplanetary magnetic decreases, and linear magnetic decreases: Differences and distinguishing features

et al. 2011

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“…In particular the propagation of energetic particles through the anisotropic plasma will be influenced strongly Tsurutani and Lakhina, 2004;Costa et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

Magnetic Decreases (MDs) and mirror modes: two different plasma β changing mechanisms

Tsurutani

Lakhina

Verkhoglyadova

et al. 2010

Nonlin. Processes Geophys.

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Abstract.We discuss two different physical processes that create localized high β plasma regions. One is nonlinear wave-steepening, generating magnetic decreases (MDs) by a ponderomotive force. The other is the mirror instability generating alternating high and low β plasma regions. It is demonstrated that MDs and mirror modes are observationally quite different structures. MDs spatially occur in interplanetary space and mirror modes primarily in planetary magnetosheaths. MDs are characterized by: 1) variable (exponentially decreasing number with increasing) angular changes, 2) variable (exponentially decreasing) thicknesses, and 3) no characteristic inter-event spacings. In sharp contrast, mirror modes are characterized by: 1) little or no angular changes across the structures, 2) a characteristic scale size, and 3) are quasiperiodic in nature.Arguments are presented for the recently observed magnetic dips in the heliosheath being mirror mode structures. The sources of free energy for instability are discussed. Both structures are important for energetic particle transport in astrophysical and heliospheric plasmas.

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“… Fisk and Jokipii [1999] and Giacalone [1999] argued that latitudinal transport of CIR energetic particles can be accounted for by direct magnetic connection [ Fisk , 1996] or cross‐field diffusion in the random walk of field lines [ Jokipii and Parker , 1968]. With regard to cross‐field diffusion, Tsurutani et al [1999] and Costa et al [2011] proposed that particle interaction with MDs is also a contributing factor owing to displacement of the particle guiding center, which is a nonresonant type of diffusion. We should emphasize that the present one‐dimensional simulation artificially suppresses the oblique wave propagation as well as cross‐field diffusion of particles.…”

Section: Summary and Discussionmentioning

confidence: 99%

Generation process of magnetic decreases and the resulting kinetic effects on energetic particles within corotating interaction regions

Tsubouchi¹

2012

J. Geophys. Res.

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[1] One-dimensional hybrid simulations are performed to examine the formation mechanism of magnetic decrease (MD) structures within corotating interaction regions (CIRs) and their effect on the energetic particle profiles associated with the shock acceleration at the CIR boundaries. As the source of MD formation, Alfvén wave structures propagating in the fast solar wind, which make depressions in the magnetic field magnitude after passing through the CIR reverse shock, are taken into account. The observed MD properties of the simultaneous density and pressure enhancement are confirmed. The key process of reducing the field intensity is the incidence of Alfvénic field variations in the anisotropic plasma (P ? > P k ) of the reverse shock downstream. Directional changes in the magnetic field induce energy exchange between parallel and perpendicular components, leading to isotropization and adiabatic field reduction. Magnetic mirror points consequently form, where field-aligned streams further intensify and particles accumulate in MDs. The capture of particles by MDs delays the reverse shock evolution. Therefore, it is expected that MDs will reduce the CIR dimension and lower the efficiency of particle acceleration at CIR shocks.Citation: Tsubouchi, K. (2012), Generation process of magnetic decreases and the resulting kinetic effects on energetic particles within corotating interaction regions,

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A computational study of nonresonant cross-field diffusion of energetic particles due to their interaction with interplanetary magnetic decreases

Cited by 5 publications

References 31 publications

Magnetosheath and heliosheath mirror mode structures, interplanetary magnetic decreases, and linear magnetic decreases: Differences and distinguishing features

Magnetosheath and heliosheath mirror mode structures, interplanetary magnetic decreases, and linear magnetic decreases: Differences and distinguishing features

Magnetic Decreases (MDs) and mirror modes: two different plasma β changing mechanisms

Generation process of magnetic decreases and the resulting kinetic effects on energetic particles within corotating interaction regions

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