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首页> 外文期刊>Physics of plasmas >Particle acceleration by circularly and elliptically polarised dispersive Alfven waves in a transversely inhomogeneous plasma in the inertial and kinetic regimes
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Particle acceleration by circularly and elliptically polarised dispersive Alfven waves in a transversely inhomogeneous plasma in the inertial and kinetic regimes

机译：在惯性和动力学状态下，横向非均匀等离子体中圆和椭圆偏振色散Alfven波对粒子的加速作用

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Dispersive Alfven waves (DAWs) offer, an alternative to magnetic reconnection, opportunity to accelerate solar flare particles in order to alleviate the problem of delivering flare energy to denser parts of the solar atmosphere to match x-ray observations. Here, we focus on the effect of DAW polarisation, left, right, circular and elliptical, in the different regimes inertial and kinetic, aiming to study these effects on the efficiency of particle acceleration. We use 2.5D particle-in-cell simulations to study how the particles are accelerated when DAW, triggered by a solar flare, propagates in the transversely inhomogeneous plasma that mimics solar coronal loop. (1) In the inertial regime, fraction of accelerated electrons (along the magnetic field) in the density gradient regions is ≈20 by the time when DAW develops three wavelengths and is increasing to ≈30 by the time when DAW develops thirteen wavelengths. In all considered cases, ions are heated in the transverse to the magnetic field direction and fraction of heated particles is ≈35. (2) The case of right circular, left and right elliptical polarisation DAWs, with the electric field in the non-ignorable transverse direction exceeding several times that of in the ignorable direction, produce more pronounced parallel electron beams (with larger maximal electron velocities) and transverse ion beams in the ignorable direction. In the inertial regime, such polarisations yield the fraction of accelerated electrons 20. In the kinetic regime, this increases to 35. (3) The parallel electric field that is generated in the density inhomogeneity regions is independent of the electron-ion mass ratio and stays of the order 0.03 ω_(pe)cm_e/e which for solar flaring plasma parameters exceeds Dreicer electric field by eight orders of magnitude. (4) Electron beam velocity has the phase velocity of the DAW. Thus, electron acceleration is via Landau damping of DAWs. For the Alfven speeds of V _A 0.3c, the considered mechanism can accelerate electrons to energies circa 20 keV. (5) The increase of mass ratio from m_i/m_e 16 to 73.44 increases fraction of accelerated electrons from 20 to 30-35 (depending on DAW polarisation). For the mass ratio m_i/m_e 1836, the fraction of accelerated electrons would be >35. (6) DAWs generate significant density and temperature perturbations that are located in the density gradient regions. DAWs propagating in the transversely inhomogeneous plasma can effectively accelerate electrons along the magnetic field and heat ions across it.
机译：分散的Alfven波（DAW）提供了替代磁重连的一种机会，它可以加速太阳耀斑粒子，从而缓解将耀斑能量传递到太阳大气的较密部分以匹配X射线观测的问题。在这里，我们重点关注惯性和动力学不同情况下DAW极化（左，右，圆形和椭圆形）的影响，旨在研究这些对粒子加速效率的影响。我们使用2.5D细胞内粒子模拟研究当太阳耀斑触发的DAW在模拟太阳日冕环的横向非均匀等离子体中传播时粒子是如何加速的。 （1）在惯性状态下，当DAW产生三个波长时，密度梯度区中的加速电子（沿磁场）的比例约为≈20，而当DAW产生13个波长时，其约为≈30。在所有考虑的情况下，离子都在垂直于磁场方向的方向上加热，并且加热的粒子的比例约为≈35。 （2）右圆，左和右椭圆极化DAW的情况，不可忽略横向上的电场超过可忽略方向上的电场的几倍，会产生更明显的平行电子束（具有更大的最大电子速度）和可忽略方向的横向离子束。在惯性状态下，这种极化产生加速电子20的一部分。在动力学状态下，该比率增加到35。（3）在密度不均匀区域中产生的平行电场独立于电子离子质量比，并且保持约0.03ω_（pe）cm_e / e，对于太阳耀斑等离子体参数而言，其超过Dreicer电场达八个数量级。 （4）电子束速度具有DAW的相速度。因此，电子加速是通过DAW的Landau阻尼实现的。对于V_A 0.3c的Alfven速度，所考虑的机制可以使电子加速到大约20 keV的能量。 （5）质量比从m_i / m_e 16增加到73.44，加速电子的比例从20增加到30-35（取决于DAW极化）。对于质量比m_i / m_e 1836，加速电子的分数将> 35。 （6）DAW会在密度梯度区域产生明显的密度和温度扰动。在横向不均匀等离子体中传播的DAW可以有效地沿磁场加速电子，并使热离子穿过该磁场。

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