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Low‐frequency transverse electric atmospheric noise: Measurement and theory
Author(s) -
Turtle John P.,
Field Edward C.,
Warber Chris R.,
McGill Paul R.
Publication year - 1989
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs024i003p00325
Subject(s) - lightning (connector) , noise (video) , atmospheric noise , transverse plane , physics , altitude (triangle) , very low frequency , meteorology , computational physics , environmental science , geology , geometry , power (physics) , mathematics , structural engineering , quantum mechanics , astronomy , artificial intelligence , computer science , image (mathematics) , engineering
This paper presents measurements of both transverse electric (TE) and transverse magnetic (TM) LF atmospheric noise made aboard a free‐floating balloon at altitudes up to 20 km. Data are given for rms noise level, TE/TM noise ratio, amplitude probability distribution, and impulsiveness parameter V D . The TE/TM noise ratio was greater than reported by other authors and implies major contributions from horizontally polarized sources. Calculations of the fields generated by lightning discharges as a function of altitude and orientation show that horizontal discharges are weak TE radiators at VLF/LF unless their altitude exceeds a few kilometers. Above several kilometers, however, horizontal discharges can radiate TE noise almost as efficiently as vertical ones radiate TM noise. Most horizontal lightning channels do, in fact, occur above 3 km and are more frequent than vertical channels. Moreover, the horizontal component of lightning is often two or three times greater in extent than the vertical component, even for cloud‐to‐ground discharges. It therefore appears that TE noise might well be caused primarily by direct radiation from horizontal lightning rather than by geomagnetically converted radiation from vertical lightning.