Abstract An observation of altitude descents in high-frequency enhanced ion line (HFIL) and plasma line (HFPL) are examined, and an alternative explanation are presented. The HFIL and HFPL altitudes should be governed by the dispersion relations of ion acoustic and Langmuir waves respectively, and those altitude descents in HFIL and HFPL may be in consequence of the significantly enhanced electron temperature and the thermal conduction. When heating the ionosphere, the HFIL should be observed at a lower altitude, at which a larger mass of ion may match the enhanced electron temperature so that the enhanced ion acoustic wave may meet the Bragg condition. Similarly, the enhanced electron temperature should match a smaller electron density at a lower altitude, where the enhanced Langmuir wave may meet the Bragg condition and the HFPL is observed. Some previously observed altitude descents in the HFIL and HFPL demonstrate the consistency with the suggested theory.

中文翻译：

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EISCAT 电离层加热期间高频增强等离子体和离子线的下降

摘要 研究了对高频增强离子线 (HFIL) 和等离子线 (HFPL) 高度下降的观察，并提出了另一种解释。HFIL和HFPL高度分别受离子声波和Langmuir波的色散关系支配，HFIL和HFPL高度下降可能是电子温度和热传导显着增强的结果。加热电离层时，应在较低的高度观察HFIL，在该高度处可能有较大质量的离子与增强的电子温度相匹配，使增强的离子声波满足布拉格条件。类似地，增强的电子温度应与较低高度处较小的电子密度相匹配，在该处增强的朗缪尔波可能满足布拉格条件并观察到 ​​HFPL。