Dynamics of relativistic leptonic jets in low-density plasmas

低密度等离子体中相对论轻子射流的动力学

基本信息

批准号：
EP/L013975/1
负责人：
Gianluca Sarri
金额：
$ 12.54万
依托单位：
Queen's University Belfast
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FL013975%2F1
关键词：
Dynamics relativistic leptonic jets low

项目摘要

Astrophysical jets represent some of the most impressive and intriguing phenomena ever detected in the Universe. They are observed to being ejected from some of the most energetic phenomena ever identified in Nature, such as black holes and pulsars. These jets can propagate, in an extremely collimated way, for enormous distances of the order of kiloparsecs (1 parsec = 3.09 x 10^13 km, i.e. 3 millions of billions of km). Studying these jets is crucial for a thorough insight into the physics of these ultra-massive objects and might contribute towards the understanding of cosmic rays and ultra-high luminosity bursts of gamma-rays. Despite the fundamental interest that these structures excite, their key properties (such as composition, density, and energy) are still lacking a thorough understanding. This is due to the fact that, despite extensive theoretical modelling and observation, clear access to the in-situ relevant physical quantities is obviously impossible. There are only educated guesses around them: for instance, it is widely accepted that most of them should be predominantly constituted of electrons, positrons (the anti-particle of the electron), and gamma-ray photons even though their typical relative percentage and spectrum have not been fully determined yet. An indirect way of inferring their characteristics is by monitoring their interaction with the intergalactic space. Even though the intergalactic space represents the best approximation to a pure vacuum that has been ever observed in Nature (it has an average density of approximately one particle per cubic centimetre), its density is still not exactly zero; it has been observed that, over such enormous distances, even the presence of such a low density medium affects the dynamics of an astrophysical jet inducing filaments, discontinuous propagation and bending. By knowing under what conditions these instabilities can be triggered, it is thus possible to infer the characteristics of these jets.It is thus clear that an in-depth study of the propagation of electron-positron jets in low density gases will play a central role in the understanding of these phenomena. Fortunately, these impressively extended and energetic phenomena are scalable: in other words, by adopting the suitable experimental parameters, it is possible to produce much smaller scale replica (down to a few millimetre size) which will behave in a similar manner. This suggests that it is possible to study astrophysical jets exploiting controlled, smaller-scale reproductions in the laboratory.Our research group has recently demonstrated the possibility of generating controlled electron-positron jets, with characteristics similar to their astrophysical counterparts, using compact laser-driven setups. Moreover, we demonstrated the possibility of tuning, by simple changes in the setup, the relative percentage of electrons and positrons in the beam going from a purely electronic beam (highest charge and, therefore, highest magnetic field) to a neutral electron-positron beam (virtually no charge and, therefore, no magnetic field).The proposed research project is then thought as the natural extension of these promising results. We aim at probing the propagation of these laser-driven electron-positron jets through background plasmas of different density. We aim at studying the different instabilities triggered as a function of the density of the gas (i.e. denser, comparable to and more rarefied than the electron-positron jet) and the relative percentage of electrons and positrons in the beam. This will allow us to experimentally characterise the propagation properties of these jets and, by comparing our laboratory results with observation of astrophysical jets, to provide a set of data useful for understanding these enigmatic astrophysical phenomena.Not only these results will be of interest to the astrophysical community, but also to the plasma physics and particle physics community

天体物理喷气机代表了宇宙中发现的一些最令人印象深刻，最有趣的现象。观察到它们是从自然界中有史以来发现的一些最有能力的现象中弹出的，例如黑洞和脉冲星。这些喷气机可以以极为准直的方式传播，以占基尔帕克斯的巨大距离（1 parsec = 3.09 x 10^13 km，即3000亿公里）。研究这些喷气机对于对这些超质量物体的物理学的彻底了解至关重要，并且可能有助于理解宇宙射线和伽玛射线的超高光度爆发。尽管这些结构激发了基本的兴趣，但它们的关键特性（例如成分，密度和能量）仍然缺乏透彻的理解。这是由于以下事实：尽管有广泛的理论建模和观察，但显然不可能清楚地访问与原位相关的物理量。它们周围只有受过良好教育的猜测：例如，人们广泛接受的是，大多数应该主要由电子，正上子（电子的抗颗粒）和伽玛射线光子组成，即使它们的典型相对百分比和频谱尚未完全确定。一种间接推断其特征的方式是监测它们与星际空间的相互作用。即使播层间空间代表了在自然界中曾经观察到的纯真空的最佳近似值（其平均密度约为每立方厘米的粒子约一个粒子），但其密度仍然不完全零；已经观察到，在如此巨大的距离上，即使存在如此低密度培养基的存在也会影响诱导丝，不连续的繁殖和弯曲的天体物理射流的动力学。通过知道可以触发这些不稳定性的条件下，可以推断这些喷气机的特征。因此，很明显，对低密度气体中电子峰值喷气机的传播的深入研究将在理解这些现象的理解中起着核心作用。幸运的是，这些令人印象深刻的扩展和能量现象是可扩展的：换句话说，通过采用合适的实验参数，可以产生较小的规模复制品（降至几毫米大小），这将以类似的方式行为。这表明，可以研究实验室中利用受控的，较小的复制品的天体物理喷气机。我们的研究小组最近证明了使用紧凑的激光驱动的激光驱动的设置具有类似于其天体物理对应物的特征。此外，我们通过简单的设置，电子和正上音的相对百分比从纯电子束（最高电荷，因此，最高磁场）到中性电子峰值梁（实际上没有电荷，因此没有电荷，因此没有磁性研究项目），就认为这些令人放松的自然扩展结果。我们的目的是通过不同密度的背景等离子体探测这些激光驱动的电子旋速射流的传播。我们旨在研究触发的不同不稳定性，这是气体密度的函数（即，比电子峰值射流比电子和电子量更稀少）和梁中电子和正上音的相对百分比。这将使我们能够通过实验表征这些喷气机的传播特性，并通过将我们的实验室结果与观察天体物理喷气机进行比较，以提供一组有助于理解这些神秘的天体物理现象有用的数据。只有这些结果才能与天体物理学社区相关，还与血浆物理学和颗粒物理学群落有关