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MAGNETIZED TURBULENT DYNAMOS IN PROTOGALAXIES

机译：原始星系中的磁化湍流动力

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The prevailing theory for the origin of cosmic magnetic fields is that they have been amplified to their present values by turbulent dynamo inductive action in the protogalactic and galactic medium. Up to now, in the calculation of the turbulent dynamo, it has been customary to assume that there is no back-reaction of the magnetic field on the turbulence, as long as the magnetic energy is less than the turbulent kinetic energy. This assumption leads to the kinematic dynamo theory. However, the applicability of this theory to protoga-laxies is rather limited. The reason is that in protogalaxies, the temperature is very high, and the viscosity is dominated by magnetized ions. As the magnetic field strength grows in time, the ion cyclotron time becomes shorter than the ion collision time, and the plasma becomes strongly magnetized. As a result, the ion viscosity becomes the Braginskii viscosity. Thus, in protogalaxies the back-reaction sets in much earlier, at field strengths much lower than those that correspond to field-turbulence energy equipartition, and the turbulent dynamo becomes what we call the magnetized turbulent dynamo. In this paper we lay the theoretical groundwork for the magnetized turbulent dynamo. In particular, we predict that the magnetic energy growth rate in magnetized dynamo theory is up to 10 times larger than that in kinematic dynamo theory. We also briefly discuss how the Braginskii viscosity can aid the development of the inverse cascade of magnetic energy after energy equipartition is reached.
机译：宇宙磁场起源的流行理论是，在原银河系和银河系介质中，湍流发电机的感应作用已将它们放大到当前值。到目前为止，在湍流发电机的计算中，通常假设磁场对湍流没有反作用，只要其磁能小于湍动能即可。这个假设导致了运动发电机理论。但是，该理论对原松弛症的适用性相当有限。原因是在原星系中，温度非常高，并且粘度主要由磁化离子控制。随着磁场强度的随时间增长，离子回旋加速器的时间变得比离子碰撞时间短，并且等离子体被强磁化。结果，离子粘度变为Braginskii粘度。因此，在原星系中，背向反应的发生时间要早得多，场强远低于对应于场湍流能量均分的场强，因此湍流发电机就变成了我们所说的磁化湍流发电机。在本文中，我们为磁化湍流发电机奠定了理论基础。尤其是，我们预测磁化发电机理论中的磁能增长率是运动发电机理论中的磁能增长率的10倍。我们还简要讨论了Braginskii粘度如何在达到能量均分后帮助磁能逆级联的发展。

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