Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines
Effect of suprathermal electrons on the intensity and Doppler frequency of electron plasma lines
复制标题
超热电子对电子等离子体线强度和多普勒频率的影响
DOI：
--
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
J. Lilensten
中科院分区：
文献类型：
--
作者：
Patrick Guio;J. Lilensten
在非相干散射雷达实验中，对所谓的上移和下移电子等离子体线的光谱测量提供了有关其强度和多普勒频率的信息。这两条谱线对应于后向散射几何形状中的两个朗缪尔波，其朝向和远离雷达行进。在白天的电离层中，太阳极紫外线产生的光电子占总电子数的一小部分，可以在热平衡以上激发或抑制这些朗缪尔波，从而增强热水平以上的谱线强度。光电子的存在也改变了麦克斯韦等离子体的介电响应函数，从而影响等离子体线的多普勒频率。在本文中，我们提出了一个高时间分辨率的等离子体线数据集收集的EISCAT VHF雷达。分析的数据进行了比较，包括超热电子人口的影响，由运输代码计算的模型。通过比较分析的等离子体线的数据，我们的模型的强度，我们表明，在电子超热分布在能量范围20-30 eV的两个尖锐的峰导致增加的朗道阻尼约24.25 eV和26.25 eV。我们已经确定了这两个尖锐的峰值的影响，光电离的N2和O的单色HeII辐射的波长为30.378 nm（40.812 eV）的强烈通量的色球网络和冕洞。此外，我们还看到，麦克斯韦等离子体的平均多普勒漂移速度实际上是超热电子引起的等离子体线多普勒频率的偏移。
In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geometry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced by the solar EUV of the total electron population can excite or damp these Langmuir waves above the thermal equilibrium, resulting in an enhancement of the intensity of the lines above the thermal level. The presence of photo-electrons also modifies the dielectric response function of the plasma from the Maxwellian and thus influences the Doppler frequency of the plasma lines. In this paper, we present a high time-resolution plasma-line data set collected on the EISCAT VHF radar. The analysed data are compared with a model that includes the effect of a suprathermal electron population calculated by a transport code. By comparing the intensity of the analysed plasma lines data to our model, we show that two sharp peaks in the electron suprathermal distribution in the energy range 20–30 eV causes an increased Landau damping around 24.25 eV and 26.25 eV. We have identified these two sharp peaks as the effect of the photoionisation of N2 and O by the intense flux of monochromatic HeII radiation of wavelength 30.378 nm (40.812 eV) created in the chromospheric network and coronal holes. Furthermore, we see that what would have been interpreted as a mean Doppler drift veloCity for a Maxwellian plasma is actually a shift of the Doppler frequency of the plasma lines due to suprathermal electrons.