Angular Momentum Transport and Proton–Alpha‐Particle Differential Streaming in the Solar Wind

Li, Bo; Habbal, Shadia Rifai; Li, Xing

doi:10.1086/513866

Cited by 10 publications

(6 citation statements)

References 21 publications

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“…Due to the bending of the magnetic field lines, however, the azimuthal velocity of the alpha particles changes sign at some point between r eff and r 0 . These results for the azimuthal flow are in agreement with previous studies of angular-momentum transport in the solar wind and show the importance of the differential streaming for the azimuthal-flow components and angular-momentum transport in the solar wind Li et al 2007). Our model, however, extends these previous treatments by including the interplay of micro-instabilities and the rotational force.…”

Section: Zero Heliographic Latitudesupporting

confidence: 92%

“…The rotational force is another collisionless mechanism that reduces the relative drift speed between protons and alpha particles Li et al 2007;McKenzie et al 1979). Roughly speaking, alpha particles and minor ions can be viewed as beads sliding on a wire, where the wire is the spiral interplanetary magnetic field, which is anchored to and rotates with the Sun.…”

Section: Introductionmentioning

confidence: 99%

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Deceleration of Alpha Particles in the Solar Wind by Instabilities and the Rotational Force: Implications for Heating, Azimuthal Flow, and the Parker Spiral Magnetic Field

Verscharen

Chandran

Bourouaine

et al. 2015

ApJ

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Protons and alpha particles in the fast solar wind are only weakly collisional and exhibit a number of nonequilibrium features, including relative drifts between particle species. Two non-collisional mechanisms have been proposed for limiting differential flow between alpha particles and protons: plasma instabilities and the rotational force. Both mechanisms decelerate the alpha particles. In this paper, we derive an analytic expression for the rate Q flow at which energy is released by alpha-particle deceleration, accounting for azimuthal flow and conservation of total momentum. We show that instabilities control the deceleration of alpha particles at r < r crit , and the rotational force controls the deceleration of alpha particles at r > r crit , where r crit ≃ 2.5 AU in the fast solar wind in the ecliptic plane. We find that Q flow is positive at r < r crit and Q flow = 0 at r ≥ r crit , consistent with the previous finding that the rotational force does not lead to a release of energy. We compare the value of Q flow at r < r crit with empirical heating rates for protons and alpha particles, denoted Q p and Q α , deduced from in-situ measurements of fast-wind streams from the Helios and Ulysses spacecraft. We find that Q flow exceeds Q α at r < 1 AU, and that Q flow /Q p decreases with increasing distance from the Sun from a value of about one at r = 0.29 − 0.42 AU to about 1/4 at 1 AU. We conclude that the continuous energy input from alpha-particle deceleration at r < r crit makes an important contribution to the heating of the fast solar wind. We also discuss the implications of the alpha-particle drift for the azimuthal flow velocities of the ions and for the Parker spiral magnetic field.

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Section: Zero Heliographic Latitudesupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Deceleration of Alpha Particles in the Solar Wind by Instabilities and the Rotational Force: Implications for Heating, Azimuthal Flow, and the Parker Spiral Magnetic Field

Verscharen

Chandran

Bourouaine

et al. 2015

ApJ

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“…The solar wind rotation influences the differential ion‒ion velocities [ McKenzie et al , ; Hollweg and Isenberg , ]. The azimuthal (transverse) particle velocity components importantly affect the radial momentum transport in the solar wind leading to the relative deceleration between alpha particles and protons [ Li et al , ]; this effect, however, does not seem to account for the observed relative deceleration in the fast solar wind between 0.3 and 1 AU but may be relevant for the Ulysses observations [ Li et al , ].…”

Section: Introductionmentioning

confidence: 99%

Protons and alpha particles in the expanding solar wind: Hybrid simulations

Hellinger

Trávníček

2013

JGR Space Physics

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[1] We present results of a two-dimensional hybrid expanding box simulation of a plasma system with three ion populations, beam and core protons, and alpha particles (and fluid electrons), drifting with respect to each other. The expansion with a strictly radial magnetic field leads to a decrease of the ion perpendicular to parallel temperature ratios as well as to an increase of the ratio between the ion relative velocities and the local Alfvén velocity creating a free energy for many different instabilities. The system is most of the time marginally stable with respect to kinetic instabilities mainly due to the ion relative velocities; these instabilities determine the system evolution counteracting some effects of the expansion. Nonlinear evolution of these instabilities leads to large modifications of the ion velocity distribution functions. The beam protons and alpha particles are decelerated with respect to the core protons and all the populations are cooled in the parallel direction and heated in the perpendicular one. On the macroscopic level, the kinetic instabilities cause large departures of the system evolution from the double adiabatic prediction and lead to perpendicular heating and parallel cooling rates which are comparable to the heating rates estimated from the Helios observations. Citation: Hellinger, P., and P. M. Trávníček (2013), Protons and alpha particles in the expanding solar wind: Hybrid simulations,

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“…One of the greatest concerns within the current space science community has been increasingly focused on the Sun‐Earth system, which is intimately linked by the solar wind. The solar wind originates from the chromospheric network [ Xia et al , 2003; Xia , 2003; Xia et al , 2004], according to the measurements of ultraviolet emission and Doppler shifting speed in the inner corona, carries non‐Wentzel‐Kramers‐Brillouin Alfvén Waves in the differential flow of multiple ion species [ Li and Li , 2007, 2008], is very likely driven by an ion cyclotron resonance mechanism via the Kolmogorov turbulent cascade [ Li et al , 2004], and transports the angular momentum from the Sun [ Li and Li , 2006; Li et al , 2007; Li and Li , 2009]. The ubiquitous interplanetary solar wind highly fluctuates, owing to outward emanating disturbances from solar activities.…”

Section: Introductionmentioning

confidence: 99%

Magnetohydrodynamic simulation of the interaction between two interplanetary magnetic clouds and its consequent geoeffectiveness: 2. Oblique collision

2009

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[1] The numerical studies of the interplanetary coupling between multiple magnetic clouds (MCs) are continued by a 2.5-dimensional ideal magnetohydrodynamic (MHD) model in the heliospheric meridional plane. The interplanetary direct collision (DC)/oblique collision (OC) between both MCs results from their same/different initial propagation orientations. Here the OC is explored in contrast to the results of the DC. Both the slow MC1 and fast MC2 are consequently injected from the different heliospheric latitudes to form a compound stream during the interplanetary propagation. The MC1 and MC2 undergo contrary deflections during the process of oblique collision. Their deflection angles of jdq 1 j and jdq 2 j continuously increase until both MC-driven shock fronts are merged into a stronger compound one. The jdq 1 j, jdq 2 j, and total deflection angle Dq (Dq = jdq 1 j + jdq 2 j) reach their corresponding maxima when the initial eruptions of both MCs are at an appropriate angular difference. Moreover, with the increase of MC2's initial speed, the OC becomes more intense, and the enhancement of dq 1 is much more sensitive to dq 2 . The jdq 1 j is generally far less than the jdq 2 j, and the unusual case of jdq 1 j ' jdq 2 j only occurs for an extremely violent OC. But because of the elasticity of the MC body to buffer the collision, this deflection would gradually approach an asymptotic degree. As a result, the opposite deflection between the two MCs, together with the inherent magnetic elasticity of each MC, could efficiently relieve the external compression for the OC in the interplanetary space. Such a deflection effect for the OC case is essentially absent for the DC case. Therefore, besides the magnetic elasticity, magnetic helicity, and reciprocal compression, the deflection due to the OC should be considered for the evolution and ensuing geoeffectiveness of interplanetary interaction among successive coronal mass ejections.Citation: Xiong, M., H. Zheng, and S. Wang (2009), Magnetohydrodynamic simulation of the interaction between two interplanetary magnetic clouds and its consequent geoeffectiveness: 2.

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Angular Momentum Transport and Proton–Alpha‐Particle Differential Streaming in the Solar Wind

Cited by 10 publications

References 21 publications

Deceleration of Alpha Particles in the Solar Wind by Instabilities and the Rotational Force: Implications for Heating, Azimuthal Flow, and the Parker Spiral Magnetic Field

Deceleration of Alpha Particles in the Solar Wind by Instabilities and the Rotational Force: Implications for Heating, Azimuthal Flow, and the Parker Spiral Magnetic Field

Protons and alpha particles in the expanding solar wind: Hybrid simulations

Magnetohydrodynamic simulation of the interaction between two interplanetary magnetic clouds and its consequent geoeffectiveness: 2. Oblique collision

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