Artificial Auroras: The energy spectrum of accelerated electrons from wave-particle interactions

人造极光：波粒相互作用加速电子的能谱

• 批准号: ST/G00241X/1
• 负责人: Michael Kosch
• 金额: $ 40.41万
• 依托单位: Lancaster University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FG00241X%2F1
• 关键词: Artificial; Auroras; energy; spectrum; accelerated

Over 99% of the observable universe is in the plasma state, a charged tenuous gas of negative electrons and positive ions. The interplanetary space medium is permeated by plasma emanating from the Sun, the solar magnetic field, and electromagnetic waves of many different frequencies. It is a well-established fact that electromagnetic waves can transform into electrostatic plasma waves in a magnetized plasma, which can accelerate charged particles to high energies via several different mechanisms. Not only is it vital that we understand the behaviour of plasma in order to understand a fundamental building block of the universe, but we also need to understand how particles become accelerated to high enough energies to threaten human space travel as well satellite survival. Plasma is rare on Earth, but can be found in electrical discharges such as lightening. It can also be produced in vacuum chambers, but there are non-linear scale size issues and boundary wall constraints with such experiments. However, a natural unbounded plasma is freely available in the upper-atmosphere above 100 km altitude, the ionosphere. Despite being remote, there is a long and successful track record of remote sensing of the ionosphere by radars (e.g. SuperDARN and EISCAT) and optics. It is well established that beaming high-power (1 MW) high-frequency (4-8 MHz) electromagnetic waves into the ionosphere (e.g. from the EISCAT Heater facility) causes various wave-plasma interactions resulting in particle acceleration, which can be diagnosed remotely by radars and optics. For example, stimulating Langmuir turbulence accelerates electrons and produces electron-Langmuir and ion-acoustic plasma waves parallel to the magnetic field line which can be detected by an incoherent scatter radar (e.g. EISCAT); stimulating upper-hybrid resonance accelerates electrons and produces plasma density irregularities perpendicular to the magnetic field line which can be detected by a coherent scatter radar (e.g. SuperDARN CUTLASS); and stimulating lower-hybrid caviton collapse accelerates electrons and ions and produces plasma cavitons which can be detected by both types of radars. Some plasma waves, e.g. electron-Bernstein waves, do not produce particle acceleration. The different mechanisms can be preferentially stimulated by adjusting the Heater beam polarization, power, frequency, pointing direction and amplitude modulation cycle. In addition, different mechanisms have different growth rates, e.g. 10 s for upper-hybrid resonance and typically <1 s for the other mechanisms. A clear symptom of Heater-stimulated electron acceleration to high energies is the fact that such transmissions into the ionosphere produce artificial optical emissions identical to the natural auroras, i.e. the artificial auroras. These sub-visual emissions typically appear in the height range 200-300 km, where the Heater can efficiently stimulate various plasma resonances, with a typical dimension of ~20-50 km. These artificial auroras can only come from electron collisions with the dominant atomic oxygen and molecular nitrogen constituents in the upper-atmosphere, as is the case for natural auroras. However, for the artificial auroras, the accelerated electrons are produced locally by the artificially stimulated plasma resonances, whereas natural auroras are produced by electrons precipitating out of the magnetosphere. Of the many optical emissions detected, the 4 standard wavelengths most important for the proposed research are 630.0, 557.7, 844.6 and 427.8 nm, with energy thresholds of about 2, 4.2, 11 and 18.6 eV. By measuring the photon flux at each wavelength using calibrated optical detectors, and knowing the photon emission rate for each wavelength as a function of electron collision energy, the quantitative energy spectrum of the accelerated electrons can be uniquely determined. This can be done selectively for each mechanism and is the primary goal of this proposal.

超过99%的可观测宇宙处于等离子体状态，一种由负电子和正离子组成的带电稀薄气体。行星际空间介质中充满了来自太阳的等离子体、太阳磁场和许多不同频率的电磁波。电磁波可以在磁化等离子体中转化为静电等离子体波，这可以通过几种不同的机制将带电粒子加速到高能量，这是一个公认的事实。我们不仅必须了解等离子体的行为，以了解宇宙的基本组成部分，而且我们还需要了解粒子如何加速到足以威胁人类太空旅行和卫星生存的高能量。等离子体在地球上很罕见，但可以在放电中找到，如闪电。它也可以在真空室中生产，但这种实验存在非线性尺度尺寸问题和边界壁约束。然而，在100公里高度以上的高层大气中，即电离层中，可以自由地获得天然的无界等离子体。尽管距离遥远，但在利用雷达（如SuperDARN和EISCAT）和光学仪器对电离层进行遥感方面有着长期和成功的记录。众所周知，向电离层发射高功率（1兆瓦）高频（4-8兆赫）电磁波（例如从EISCAT加热器设施发射）会引起各种波-等离子体相互作用，从而导致粒子加速，这可以通过雷达和光学设备进行远程诊断。例如，刺激朗缪尔湍流加速电子并产生平行于磁场线的电子朗缪尔和离子声学等离子体波，其可以由非相干散射雷达检测到（例如EISCAT）;刺激上混合共振加速电子并产生垂直于磁场线的等离子体密度不规则性，其可由相干散射雷达检测到（例如，SuperDARN CUTLASS）;并且刺激低杂波空穴子崩溃加速电子和离子并产生等离子体空穴子，其可以被两种类型的雷达检测到。某些等离子体波，例如电子伯恩斯坦波，不产生粒子加速。通过调节加热器光束的偏振、功率、频率、指向方向和幅度调制周期，可以优先激发不同的机制。此外，不同的机制具有不同的增长速率，例如，对于上混合共振为10 s，而对于其他机制通常<1 s。加热器激发的电子加速到高能量的一个明显症状是，这种传输到电离层产生与自然极光相同的人工光发射，即人工极光。这些亚可见光发射通常出现在200-300 km的高度范围内，在那里加热器可以有效地激发各种等离子体共振，典型尺寸为~20-50 km。这些人造极光只能来自电子与高层大气中占主导地位的原子氧和分子氮成分的碰撞，就像自然极光的情况一样。然而，对于人造极光，加速电子是由人工激发的等离子体共振局部产生的，而天然极光是由磁层沉淀出的电子产生的。在检测到的许多光发射中，对拟议研究最重要的4个标准波长是630.0、557.7、844.6和427.8 nm，能量阈值约为2、4.2、11和18.6 eV。通过使用校准的光学检测器测量每个波长处的光子通量，并且知道每个波长的光子发射率作为电子碰撞能量的函数，可以唯一地确定加速电子的定量能谱。这可以有选择地为每一种机制进行，这是本建议的主要目标。

项目成果

DIY Northern Lights

DIY北极光

• DOI: 10.1093/astrogeo/att208
• 发表时间: 2013
• 期刊: Astronomy & Geophysics
• 影响因子: 0.8
• 作者: Bryers C

Phenomena in the high latitude F region of the ionosphere induced by a HF heater wave at frequencies near the fourth electron gyroharmonic

频率接近第四电子陀螺谐波的高频加热波在电离层高纬 F 区引起的现象

• 发表时间: 2014
• 期刊: Radio Physics and Quantum Electronics
• 作者: Borisova T.D.

A comparison between resonant and nonresonant heating at EISCAT

EISCAT 谐振和非谐振加热的比较

• DOI: 10.1002/jgra.50605
• 发表时间: 2013
• 期刊: Space Physics
• 作者: Bryers C

First observations of X-mode suppression of O-mode HF enhancements at 6300 Å

首次观察到 6300° 时 X 模式抑制 O 模式 HF 增强

• DOI: 10.1029/2009gl039421
• 发表时间: 2009
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Gustavsson B

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

EISCAT 电子陀螺谐波加热过程中的受激布里渊散射

• DOI: 10.5194/angeo-33-983-2015
• 发表时间: 2015-01-01
• 期刊: ANNALES GEOPHYSICAE
• 影响因子: 1.9
• 作者: Fu, H. Y.;Scales, W. A.;Ruohoniemi, J. M.
• 通讯作者: Ruohoniemi, J. M.