Pickup ion energization by shock surfing

Lee, Martin A.; Shapiro, V. D.; Sagdeev, R. Z.

doi:10.1029/95ja03570

Cited by 259 publications

(247 citation statements)

References 63 publications

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“…Particles for which 1/2mv• < e(I) are reflected, retumed to the front by the Lorenz force, and repeat the process several times until they have acquired sufficient downstream kinetic energy to breach the potential barrier [Lee et al, 1996;Zank, et al, 1996]. One can qualitatively view the orbit displacement as a series of 'kicks', or treat the surf'rag ion as being temporarily retarded at the front and accelerated during its sojoum while it 'feels' the convective electric field.…”

Section: Mechanismsmentioning

confidence: 99%

Shock surfing vs. shock drift acceleration

Lever¹,

Quest²,

Shapiro³

2001

Geophysical Research Letters

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Abstract. We numerically investigate the pre-injection mechanism by which pickup ions approaching quasiperpendicular shocks may be accelerated above the threshold velocity required to begin diffusive shock acceleration. We demonstrate that three distinct mechanisms contribute to the acceleration and that they operate on disjoint subsets of the pickup ion population. We quantitatively compare the efficiency of each mechanism as a function of shock Mach number, pickup ion mass and shock ramp width and show that shock surfing predominates below a critical ramp width.

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Section: Mechanismsmentioning

confidence: 99%

Shock surfing vs. shock drift acceleration

Lever¹,

Quest²,

Shapiro³

2001

Geophysical Research Letters

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“…Therefore, an additional process such as direct acceleration at the shock may be required for the bulk solar wind ions. On the other hand, direct acceleration of ions at interplanetary shocks is again more efficient for pick-up ions because part of the pick-up ions has the same velocity as the shock, which, for instance, is necessary for shock surfing to operate (Lee et al 1996).…”

Section: Solutions Of the Fokker-planck Equationmentioning

confidence: 99%

“…In fact, the ions with v xL ≈ −V q and v yL ≈ −V 2 S / 2V q R belong to the minority of ions which undergo the process of shock surfing or multiple reflections and gain substantial energy in the motional electric field of the shock. We refer to (Lee et al 1996) for a full treatment of the dynamics of this minority population.…”

Section: The Effect Of the Shock Potentialmentioning

confidence: 99%

On the “injection problem” at the solar wind termination shock

Kallenbach

Hilchenbach

Chalov

et al. 2005

A&A

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Abstract. This article presents an integrated analytical model on the injection efficiencies of the different ion species of the Anomalous component of the Cosmic Rays (ACRs) at the solar wind termination shock. We find that the injection into diffusive (first-order Fermi) acceleration is dominated by parallel ion diffusion and not by perpendicular diffusion unless the angle Ψ between the shock normal and the heliospheric magnetic field is almost exactly 90 • (89.3 • < Ψ ≈ 90 • ). In steady state the threshold speed for injection into first-order Fermi acceleration at a not exactly perpendicular solar wind termination shock -with the Parker shock angle Ψ ≈ 89.3 • -adjusts itself self-consistently. Increased anisotropic ACR flux amplifies Alfvénic turbulence which in turn suppresses parallel diffusion. It therefore increases the injection threshold and decreases the ACR flux until equilibrium is reached. For this equilibrium situation, we estimate the injection efficiencies of different species of suprathermal ions at the termination shock. We consider the following pre-acceleration processes: 1) momentum diffusion in compressional (ion-acoustic and magnetosonic) turbulence in the upstream supersonic solar wind and adiabatic cooling during convection to the termination shock; 2) reflection, transmission, and acceleration in the electric potential of the termination shock; and 3) momentum diffusion (stochastic or second-order Fermi acceleration) in the subsonic solar wind downstream of the termination shock in the inner heliosheath region. Our model results are compared to data from instruments on board the SOHO, ACE, Ulysses, and Voyager spacecraft.

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“…Another way for particles to encounter the shock several times is by being trapped between the electrostatic potential and the upstream Lorentz force. The latter mechanism (shock surfing) has been proposed for acceleration of pickup ions at quasi-perpendicular shocks [Lee et al, 1996;Zank et al, 1996;Lipatoy et al, 1998]. This mechanism can work for pickup ions but not easily for thermal solar wind ions, since it requites that the ions have in the shock frame a velocity normal to the shock which is much smaller than the solar wind bulk velocity.…”

Section: Introductionmentioning

confidence: 99%

Cross‐field diffusion of charged particles and the problem of ion injection and acceleration at quasi‐perpendicular shocks

2000

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Abstract.It is an open question how charged particles are injected at quasiperpendicular shocks into a first-order Fermi acceleration mechanism. Crossfield diffusion of solar wind ions is a possible injection process. However, in a system with at least one ignorable spatial dimension, charged particles moving in fluctuating fields are tied to the magnetic field lines. We have therefore determined the cross-field diffusion coefficient of charged particles in self-consistently generated turbulence by three-dimensional hybrid simulations. The initial setup consists of a homogeneous magnetic field with an isotropic core plasma plus a second, nongyrotropic ion distribution. The combined distributions resemble the distribution found immediately downstream of the quasi-perpendicular Earth bow shock: Part of the solar wind is transmitted (core) and part is specularly reflected and subsequently convected downstream (nongyrotropic part). Such a particle distribution excites the Alfv•n ion cyclotron and mirror mode instability. The turbulence scatters the nongyrotropic ions both parallel and perpendicular to the field. The perpendicular and the parallel diffusion coefficients have been determined for two values of the density of the nongyrotropic distributions, nb. The ratio of the two diffusion coefficients is smaller than the value predicted by hard sphere scattering theory, i.e., parallel scattering is considerably stronger than scattering perpendicular to the field. The power in the magnetic field fluctuations in the high n•, case is comparable to the power obtained in a two-dimensional quasiperpendicular shock simulation immediately behind the shock ramp. On the basis of perpendicular scattering time it is suggested that cross-field diffusion in the turbulent wave field generated by the specularly reflected ions is sufficient to inject and accelerate these ions efficiently at quasi-perpendicular shocks.

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Pickup ion energization by shock surfing

Cited by 259 publications

References 63 publications

Shock surfing vs. shock drift acceleration

Shock surfing vs. shock drift acceleration

On the “injection problem” at the solar wind termination shock

Cross‐field diffusion of charged particles and the problem of ion injection and acceleration at quasi‐perpendicular shocks

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