Wavelength measurement of auroral hiss
Wavelength measurement of auroral hiss
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极光嘶嘶声的波长测量
DOI：
10.1029/91ja01863
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发表时间：
1991
影响因子：
--
通讯作者：
J. Clemmons
中科院分区：
文献类型：
--
作者：
R. Ergun;E. M. Klementis;C. Carlson;J. Mcfadden;J. Clemmons
利用正交天线技术测量了极光电离层中甚低频发射的平均波长随频率的变化。这些测量是由极光探测火箭进行的，对波长在20赫兹至10千赫之间、波长在150米至1300米之间的波的频率敏感。在许多情况下，刚好高于较低混合频率的发射具有12 m或更短的波长，随着频率的增加而增加。测得的波长是这样的，即VLF发射与能量为几百eV的电子共振，而倒V电子的能量为1020 keV。在飞行过程中经常观测到低能（<300 eV ~ 103 keV）的场向电子流爆发，但未发现场向电子流强度与VLF谱强度或波长的直接相关性，不同类型的VLF谱中发现了短于预期的波长。稳态VLF频谱一般显示出一个典型的尖锐的截止下的较低的混合频率与最大值在几倍的较低的混合频率。这些光谱也有结构在氢回旋谐波以上的较低的混合频率。在其他时间，观察到25秒至50秒的低混合辐射爆发。在最强烈的发射期间，光谱峰非常接近较低的混合频率，而氢伯恩斯坦发射低于较低的混合频率。
The average wavelengths of VLF emissions in the auroral ionosphere were measured as a function of frequency using an orthogonal antenna technique. The measurements, made by an auroral sounding rocket, were sensitive to wavelengths between ∼5 m and ∼300 m for wave frequencies from 20 Hz to 10 kHz. The emissions just above the lower hybrid frequency had wavelengths of 12 m or less in many cases, increasing with increasing frequency. The measured wavelengths were such that the VLF emissions were resonant with electrons whose energies were a few hundred eV, whereas the inverted-V electrons had energies of ∼20 keV. Bursts of low-energy (<300 eV to ∼3 keV), field-aligned electron fluxes were observed often during the flight, but no direct correlation between the flux intensity and the VLF intensity or wavelength could be found. The shorter-than-expected wavelengths were found in different types of VLF spectra. The steady state VLF spectra generally displayed a typical sharp cutoff below the lower hybrid frequency with a maximum at several times the lower hybrid frequency. These spectra also had structure at hydrogen cyclotron harmonics above the lower hybrid frequency. At other times, 25-s to 50-s bursts of lower hybrid emissions were observed. During the periods of the most intense emissions, the spectral peak was very near the lower hybrid frequency while hydrogen Bernstein emissions were seen below the lower hybrid frequency.