ENERGY SPECTRUM OF ENERGETIC PARTICLES ACCELERATED BY SHOCK WAVES: FROM FOCUSED TRANSPORT TO DIFFUSIVE ACCELERATION

2011 ◽  
Vol 738 (2) ◽  
pp. 168 ◽  
Author(s):  
Pingbing Zuo ◽  
Ming Zhang ◽  
Konstantin Gamayunov ◽  
Hamid Rassoul ◽  
Xi Luo
Keyword(s):  
Energy Spectrum ◽  
Shock Waves ◽  
Energetic Particles ◽  
Diffusive Acceleration

scholarly journals Revisiting the theory of the evolution of pick-up ion distributions: magnetic or adiabatic cooling?

2007 ◽  
Vol 25 (12) ◽  
pp. 2649-2659 ◽  
Author(s):  
H. J. Fahr
Keyword(s):  
Solar Wind ◽  
Particle Interaction ◽  
Distribution Functions ◽  
Particle Interactions ◽  
Ion Distribution ◽  
Ion Distributions ◽  
Magnetic Cooling ◽  
Adiabatic Cooling ◽  
Diffusive Acceleration ◽  
Nonlinear Energy

Abstract. We study the phasespace behaviour of heliospheric pick-up ions after the time of their injection as newly created ions into the solar wind bulk flow from either charge exchange or photoionization of interplanetary neutral atoms. As interaction with the ambient MHD wave fields we allow for rapid pitch angle diffusion, but for the beginning of this paper we shall neglect the effect of quasilinear or nonlinear energy diffusion (Fermi-2 acceleration) induced by counterflowing ambient waves. In the up-to-now literature connected with the convection of pick-up ions by the solar wind only adiabatic cooling of these ions is considered which in the solar wind frame takes care of filling the gap between the injection energy and energies of the thermal bulk of solar wind ions. Here we reinvestigate the basics of the theory behind this assumption of adiabatic pick-up ion reactions and correlated predictions derived from it. We then compare it with the new assumption of a pure magnetic cooling of pick-up ions simply resulting from their being convected in an interplanetary magnetic field which decreases in magnitude with increase of solar distance. We compare the results for pick-up ion distribution functions derived along both ways and can point out essential differences of observational and diagnostic relevance. Furthermore we then include stochastic acceleration processes by wave-particle interactions. As we can show, magnetic cooling in conjunction with diffusive acceleration by wave-particle interaction allows for an unbroken power law with the unique power index γ=−5 beginning from lowest velocities up to highest energy particles of about 100 KeV which just marginally can be in resonance with magnetoacoustic turbulences. Consequences for the resulting pick-up ion pressures are also analysed.

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