VLF wave generation by amplitude-modulated HF heater waves at Gakona, Alaska

被引：10

作者：

Kuo, Spencer P. ^{[1
]}

Wu, Yen-Liang ^{[1
]}

Pradipta, R. ^{[2
]}

Cohen, J. A. ^{[2
]}

Lee, M. C. ^{[2
,3
]}

机构：

[1] Polytech Univ, Dept Elect & Comp Engn, Brooklyn, NY 11201 USA

[2] MIT, Plasma Sci & Fus Ctr, Cambridge, MA 02139 USA

[3] Boston Univ, Dept Elect & Comp Engn, Boston, MA 02215 USA

来源：

GEOPHYSICAL RESEARCH LETTERS | 2008年 / 35卷 / 13期

关键词：

D O I：

10.1029/2008GL034414

中图分类号：

P [天文学、地球科学];

学科分类号：

07 ;

摘要：

Experiments conducted at Gakona, Alaska, using the intensity-modulated HF heating waves to interact with electrojet currents for the generation of VLF waves, are reported. An unexpected large increasing rate from 4 to 8 kHz in the frequency dependency of the VLF radiation intensity was observed. The peak value at 8 kHz was intense ( about 7.5 dB above that of the 2 kHz signal used as a marker) and the wave intensity from 5 to 17 kHz appeared to be abnormally high (i.e., stronger than that at 2 kHz). In the experiments, we also observed the enhancement of spread-E irregularities at electrojet current altitudes due to the amplitude-modulated heater wave. These results and theoretical analyses suggest that temporally modulated electrojet currents mix with heater wave-excited density irregularities to form whistler mode currents, which generate VLF whistler waves directly with much larger intensities and better directivity than a Hertzian dipole can.

引用

页数：5

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