极光千米辐射--电子回旋脉塞范例
Auroral Kilometric Radiation -- the Electron Cyclotron Maser Paradigm
摘要:
极光千米辐射(AKR)是来自行星磁层的强射电辐射的范例。它的观测结果接近电子陀螺频率和/或其低次谐波,表明源等离子体的非热状态。当等离子体进入高能激发状态时产生发射,这导致电子分布函数的变形。在某些条件下,这导致"准相干"发射。我们认为,弱相对论性电子回旋脉塞不稳定性是产生这种辐射的原因。由于大力无线电辐射通常不是{主要}的重要性,在大尺度磁层现象,AKR等,为大尺度磁层物理学的目的,成为被认为是一个边缘问题。在这里,这一概念受到质疑。AKR虽然主要在磁层扰动时期应用于极光区,但只携带总亚暴能量的一小部分。然而,它在极光电离层上层物理学和空间天气研究中具有诊断能力。作为非热等离子体中辐射产生的基本物理问题,它仍然没有得到解决。即使只研究电子回旋脉塞,许多问题仍然悬而未决。在磁层中,通过观测和理论都可以很好地研究这些现象,因为磁层是空间中唯一可以连续进入的地方。最重要的是在这里没有暗示他们应该如何被攻击。它的价值在于它在应用于其他磁化行星、太阳系外行星和强磁化天体时所应发挥的作用,它是一种重要的工具,可以诊断在热、冲击或同步辐射之外的射频范围内产生辐射的物质状态。
英文摘要:
Auroral kilometric radiation (AKR) is the paradigm of intense radio emission from planetary magnetospheres. Being close to the electron gyro frequency and/or its lower harmonics, its observation indicates the non-thermal state of the source plasma. Emission is produced when the plasma enters a state of energetic excitation which results in deformation of the electron distribution function. Under certain conditions this leads to "quasi-coherent" emission. It is believed that the weakly-relativistic electron-cyclotron-maser instability is responsible for this kind of radiation. Since energetically radio radiation normally is not of {primary} importance in the large-scale magnetospheric phenomena, AKR as such has, for the purposes of large-scale magnetospheric physics, become considered a marginal problem. Here this notion is questioned. AKR while applying to the auroral region mainly during magnetospherically disturbed times {carries just a fraction of the total substorm energy. It is, however, of diagnostic power in the physics of the upper auroral ionosphere and Space Weather research}. As a fundamental physical problem of generation of radiation in non-thermal plasmas {it remains not resolved yet. Many questions have been left open even when dealing only with the electron-cyclotron-maser. These can advantageously be studied in the magnetosphere proper both by observation and theory, the only continuously accessible place in space. The most important are listet here with hint on how they should be attacked. Its value is to be sought in the role it should play in application to the other magnetized planets, extra-solar planets, and to strongly magnetized astronomical objects} as an important {tool to diagnose the matter state responsible for radiation in the radio frequency range beyond thermal, shock or synchrotron radiation.
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