等离子和湍流研究

磁重联及其影响

The problem of what happens with magnetic fields in highly conductive astrophysical plasmas is of major importance. If magnetic fields are nearly perfectly frozen in the magnetized fluid, as it follows from the textbook Sweet-Parker solution, then magnetized fluids are very different from fluids and resemble more felt or Jello. Attempts to appeal to collisionless effects do not produce a good explanation, as, first of all, many astrophysical fluids (e.g. most phases of the ISM) do not satisfy the criterion of being collisionless. A promising solution for the problem of reconnection has been suggested in Lazarian & Vishniac (1999, henceforth LV99), where it was shown that magnetic reconnection gets fast, i.e. independent of resistivity, in the presence of turbulence. This potentially provides a universal solution of the magnetic reconnection in astrophysics as turbulence is really ubiquitous in astrophysical environment.

Analytical predictions of the LV99 model of magnetic reconnection have been tested successfully numerically in Kowal et al. (2009) (see also higher resolution runs in Lazarian et al. 2010). More recently, the LV99 model was related to the well-known concepts of Richardson diffusion in magnetized fluids. The corresponding paper by Eyink, Lazarian & Vishniac (2011) has attracted the attention of the community by showing how LV99 reconnection model fits within the modern understanding of properties of turbulent fluids.

这需要搜索的磁重联的后果。研究方向到目前为止,包括宇宙射线加速和恒星的形成。用于加速处理lv99重新连接诱导一阶费米重新连接,这可以解释由不同的天体物理学物体加速宇宙射线。恒星形成,所述lv99模型预测与基于双极扩散的可接受的范例快得多去除磁通量。

MHD动荡及其影响

磁动荡的性质是许多天体物理过程,包括恒星的形成,宇宙射线的加速,物质等的运输重要的是我们已经研究过这个特性相结合的分析和数值工具。

Important progress has been achieved in both understanding of the imbalanced and balanced MHD turbulence. Our simulations got results consistent with the Beresnyak & Lazarian (2008) model  of turbulence, at the same time providing gross inconsistency with the predictions of all other existing  models. In terms of the balanced MHD turbulence, we showed that the turbulence shows diffuse non-locality, meaning that it is less local than MHD turbulence. As a result, we proved that present-day numerical simulation can not reveal the true spectral slope of turbulence making meaningless the tests of MHD turbulence theories based on the deviations of the spectral index from the Kolmogorov one.

We used our kinetic MHD code to show that in the presence of collisionless instabilities the turbulence loses its self-similarity accummulating fluctuations at the small scales. This sends a signal of warning to naïve modeling of intracluster medium and gives additional support to the Brunetti & Lazarian (2011) model of turbulence-particle interaction in intracluster plasmas (see below).

与高能粒子MHD湍流的交互作用

Substantial improvement of understanding of turbulence-particle interactions has been achieved by Brunetti & Lazarian (2011a,b). In these papers, first of all, the constraints on the models of cosmic ray reacceleration were derived, more importantly, we argued that the damping of fast modes which were shown in Brunetti & Lazarian (2007) to dominate cosmic ray acceleration (see also Yan & Lazarian 2004), is much less than it follows from the naïve application of textbook plasma physics formulae. In fact, due to gyroresonance instability developing at the Larmor scale of plasma ions, the effective mean free path of particles decreases and the fluids become effectively collisional. We showed that as a result of this effect the efficiency of the acceleration of particles by turbulence increases.

从观测星际湍流统计研究

The major advance in this field has been a development of a new technique of studying magnetic turbulence from synchrotron fluctuations in Lazarian & Pogosyan (2011). There the description of synchrotron fluctuations for the arbitrary index of cosmic ray spectrum and models of axisymmetric turbulence corresponding to the models numerically proven in Cho & Lazarian (2003) has been performed. The former problem was a long standing one and cracking it opens new wide avenues for both better describing synchrotron fluctuations, including the fluctuations of synchrotrong polarization, which quantitative description is essential for studying illusive CMB B-modes and for bringing the studies of magnetic turbulence in our and nearby galaxies to a new stage. The achieved theoretical progress is very timely in view of the advancements in the SKA and LOFAR projects. 

Tsallis statistics to simulated maps of column desity, studies of ISM magnetization via studies of anisotropy of observer-measurable velocity centroids fluctuations. Important papers related to the studies of Big Power Law (in terms of electron density fluctuations) in the sky and velocity fluctuations for HI at high galactic altituted have been published. We also used our understanding of fluctuations arising from turbulence for proposing a new technique of separating foregrounds from CMB (see Cho & Lazarian 2010).

尘埃等离子体和影响的性质

天体物理环境有灰尘和粉尘效力于许多天体物理过程具有重要作用。我们的研究主要集中在三个方向:

  1. 的星际,拱和星际灰尘,它提供了一种对磁场和湍流的可靠研究对准。
  2. 与凝血和它们的碎片在不同的环境影响的灰尘颗粒的加速度。
  3. 从颗粒的最小群,其也被称为纺丝粉尘排放微波发射。

粉尘有关的研究所有这些方向的高天体物理意义,因为,举例来说,纺纱粉尘排放前景与中巴测量干扰的重要组成部分。

澳门现金赌场家