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Centrifugal acceleration of astroparticles to relativistic energies might take place in rotating astrophysical objects (see also Fermi acceleration). It is strongly believed that AGN and Pulsars have rotating magnetospheres, therefore, they potentially can drive charged particles to high and ultra high energies. == Acceleration to high energies == It is well known that the magnetospheres of AGN and Pulsars are characterized by strong magnetic fields, which in turn, might force the charged particles follow the field lines. On the other hand, if the magnetic field lines are rotating (which is the case for the above-mentioned astrophysical objects) the particles will inevitably undergo centrifugal acceleration. In the pioneering work by Machabeli & Rogava 〔(Machabeli G. Z. & Rogava A. D. Centrifugal force: A gedanken experiment. Physical Review A, Volume 50, Issue 1, pp.98-103 (1994) )〕 was considered a gedanken experiment: a bead moving inside a straight rotating pipe. Dynamics of a particle was analyzed as analytically as numerically and it has been shown that if the rigid rotation is maintained for a sufficiently long time energy of the bead will asymptotically increase. In particular, Rieger & Mannheim,〔(Rieger F. M. & Mannheim K. Particle acceleration by rotating magnetospheres in active galactic nuclei. Astronomy and Astrophysics, v.353, p.473-478 (2000) )〕 based on the theory developed by Machabeli & Rogava have shown that the Lorentz factor of the bead behaves as where is the initial Lorentz factor, Ω is the angular velocity of rotation, is the radial coordinate of the particle and is the speed of light. From this behavior it is evident that radial motion will exhibit a nontrivial character. In due course of motion the particle will reach the light cylinder surface (a hypothetical area where the linear velocity of rotation exactly equals the speed of light), leading to the increase of the poloidal component of velocity. On the other hand, the total velocity cannot exceed the speed of light, therefore, the radial component must decrease. This means that the centrifugal force changes its sign. As is seen from (), the Lorentz factor of the particle tends to infinity if the rigid rotation is maintained. This means that in reality the energy has to be limited by certain processes. Generally speaking, there are two major mechanisms: The inverse Compton scattering (ICS) and the so-called breakdown of the bead on the wire (BBW) mechanism.〔(Osmanov Z., Rogava A. & Bodo, G. On the efficiency of particle acceleration by rotating magnetospheres in AGN. Astronomy and Astrophysics, Volume 470, Issue 2, pp.395-400 (2007) )〕 Considering jet-like structures in AGN it has been shown that for a wide range of inclination angles of field lines with respect to the rotation axis, the ICS is the dominant mechanism efficiently limiting the maximum attainable Lorentz factors of electrons . On the other hand, it was shown that the BBW becomes dominant for relatively low luminosity AGN , leading to . The centrifugal effects are more efficient in millisecond Pulsars, since the rotation rate is quite high. Osmanov & Rieger 〔(Osmanov Z. & Rieger F. M. On particle acceleration and very high energy γ-ray emissionin Crab-like pulsars. Astronomy and Astrophysics, Volume 502, Issue 1, pp.15-20 (2009) )〕 considered the centrifugal acceleration of charged particles in the light cylinder area of the Crab-like Pulsars. It has been shown that electrons might achieve the Lorentz factors via the inverse Compton Klein-Nishina up-scattering. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Centrifugal mechanism of acceleration」の詳細全文を読む スポンサード リンク
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