Ionospheric induced very low‐frequency electric field wavetilt changes

Geophysics ◽  
1982 ◽  
Vol 47 (1) ◽  
pp. 60-62 ◽  
Author(s):  
D. V. Thiel ◽  
I. J. Chant
Keyword(s):  
Electric Field ◽  
Low Frequency ◽  
Audio Frequency ◽  
Very Low Frequency ◽  
Modal Interference ◽  
Frequency Electric Field

Very low‐frequency (VLF) electric field wavetilt measurements were made continuously over a period of four months at a fixed location. Daytime and nighttime values of the wavetilt were found to be relatively constant. During sunrise and sunset the wavetilt decreased to 20 percent of the daytime value, making wavetilt measurements meaningless for two three‐hour intervals during a 24 hour period. A mechanism involving modal interference is postulated.This phenomenon may be a problem in other passive electromagnetic (EM) prospecting systems including audio‐frequency magnetic and audiomagnetotelluric.

On: “Ionospheric induced very low frequency electric field wavetilt changes” by D. V. Thiel and I. J. Chant (GEOPHYSICS, January, 1982, p. 60–62)

Geophysics ◽  
1983 ◽  
Vol 48 (12) ◽  
pp. 1697-1697
Author(s):  
Ramesh P. Singh ◽  
D. Rankin
Keyword(s):  
Electric Field ◽  
Free Space ◽  
Low Frequency ◽  
Magnetic Sensor ◽  
Numerical Constant ◽  
Very Low Frequency ◽  
The Earth ◽  
Frequency Electric Field

The paper by Thiel and Chant reports the well‐known sunrise and sunset effect which in micropulsation studies is referred to as the dawn and dusk “chorus.” However, we disagree with the interpretation of these authors. Their choice of wavetilt as the diagnostic function is slightly misleading since they are essentially measuring at the surface of the earth despite the unfortunate location of their magnetic sensor at a height of 4 m and presumably in a building. In this case the wavetilt [Formula: see text] according to their equation (1) is equivalent to [Formula: see text] where [Formula: see text] is the impedance of the earth and [Formula: see text] is the impedance of free space. This result is independent of the mode of propagation but certainly at their distance of 4000 km is predominantly the sky wave except during the dawn and dusk periods. The turbulence due to the formation or breakup of the D‐layer in the ionosphere virtually destroys the ionospheric reflected component which is the dominant contributor to the field incident on the earth. We suggest that during most of the day the authors are measuring the impedance of the earth scaled by a numerical constant.

Development of a Low Frequency Electric Field Probe Integrating Data Acquisition and Storage

2020 ◽  
Vol E103.C (8) ◽  
pp. 345-352
Author(s):  
Zhongyuan ZHOU ◽  
Mingjie SHENG ◽  
Peng LI ◽  
Peng HU ◽  
Qi ZHOU
Keyword(s):  
Electric Field ◽  
Data Acquisition ◽  
Low Frequency ◽  
Frequency Electric Field ◽  
Electric Field Probe ◽  
And Storage

Low-Frequency Electric Field Treatment of Twisted Smectic C* Liquid Crystals and Their Electrooptic Effects

2004 ◽  
Vol 313 (1) ◽  
pp. 55-62 ◽  
Author(s):  
MAKOTO MITANI ◽  
YUYA KURATA ◽  
KAZUNORI TAKAKURA ◽  
N. SHINICHI TAKAHASHI
Keyword(s):  
Liquid Crystals ◽  
Electric Field ◽  
Low Frequency ◽  
Smectic C ◽  
Electrooptic Effects ◽  
Frequency Electric Field ◽  
Electric Field Treatment
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