...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Planetary and space science >Specular refection at a non-stationary shock: A simple model
【24h】

Specular refection at a non-stationary shock: A simple model

机译：非平稳冲击下的镜面反射：一个简单的模型

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Analytic treatments of a particle encountering a collisionless shock have commonly been based on the assumption that the shock surface is quasi-planar with length scales larger than the particle gyroradius. Within this framework, the particle distribution function width is supposed to be conserved in any shock reflection process. It is well known, however, that the thermal energy associated with backstreaming ions upstream of Earth's bow shock is significantly larger than the incident solar wind thermal energy. In a previous study, we found that non-thermal features of ions reflected quasi-adiabatically can be accounted for by considering the effect of small, normally distributed fluctuations of the shock normal over short temporal or spatial scales. The strong dependence of the particle acceleration on shock geometry leads to an increase in the temperature and to a non-thermal tail. Here, we conduct a similar analysis to investigate the effects of small, normally distributed fluctuations in the shock normal direction for specularly reflected ions. This later mechanism is considered of first importance in the dissipation process occurring at quasi-perpendicular shocks. We have derived the probability distribution functions f(v_11 and/(v_⊥) of ions issued from a specular reflection of incident solar wind in the presence of normal direction fluctuations. These distributions deviate weakly from a Maxwellian, in agreement with the observations. In particular, a qualitative agreement with the ion thermal energy is obtained for fluctuations of the normal orientation in the 5-8° range about the nominal direction. Also, we have found that the shock θBn has a weak effect on the shape of the distribution. While, not a strong determinant of the reflected distribution characteristics, the dynamical shock structure at ion scales cannot be ignored when accounting for the shock-accelerated particle thermal energy.
机译：遇到无碰撞冲击的粒子的解析处理通常基于以下假设：冲击表面是准平面的，其长度尺度大于粒子陀螺半径。在此框架内，粒子分布函数的宽度在任何震动反射过程中都应保持不变。但是，众所周知，与地球弓激波上游的回流离子相关的热能明显大于入射的太阳风热能。在先前的研究中，我们发现准绝热反射的离子的非热特征可以通过考虑在短时空或空间尺度上较小，正态分布的冲击法线波动的影响来解决。粒子加速度对冲击几何形状的强烈依赖性导致温度升高并导致非热尾。在这里，我们进行了类似的分析，以研究镜面反射离子在冲击法线方向上的小正态分布波动的影响。在准垂直冲击下发生的耗散过程中，后一种机制被认为是最重要的。我们已经推导了在法线方向波动的情况下，入射太阳风的镜面反射所产生的离子的概率分布函数f（v_11和/（v_⊥），与观察值一致，这些分布与麦克斯韦略微偏离。特别是，关于正常方向在标称方向上5-8°范围内的波动，与离子热能的定性一致，而且，我们发现冲击θBn对分布的形状影响很小。尽管不是反射分布特性的强力决定因素，但是在考虑激振加速的粒子热能时，不能忽略离子级的动态激振结构。

著录项

  • 来源
    《Planetary and space science》 |2011年第7期|p.495-501|共7页
  • 作者

    K. Meziane; A.M. Hamza; M. Wilber; MA Lee; C. Mazelle; E.A. Lucek; T. Hada;

  • 作者单位

    Physics Department, University of New Brunswick, Fredericton, Canada;

    Physics Department, University of New Brunswick, Fredericton, Canada;

    Space Sciences Laboratory, University of California, Berkeley, United States;

    Space Science Center, University of New Hampshire, Durham, United States;

    Centre d'Etudes Spatiales des Rayonnements, Toulouse, France;

    Space and Atmospheric Physics, The Blackett Laboratory, Imperial College, London, United Kingdom;

    ESST, Kyushu University, Fukuoka, Japan;

  • 收录信息
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    magnetic field; solar wind; bow shock; acceleration; distribution function;

    机译：磁场;太阳风;弓形冲击;加速度;分布函数;

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号