Penetration of the Ionosphere by Very-Low-Frequency Radio Signals-Interim Results of the LOFTI I Experiment

Leiphart, J. P.; Zeek, R. W.; Bearce, L. S.; Toth, Elena

doi:10.1109/jrproc.1962.288269

Cited by 31 publications

(18 citation statements)

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“…Although such ducts are seen at higher frequencies by Alouette I and Explorer 20, there is as yet no direct in situ evidence for ducted propagation at VLF. On the contrary, the reception of man-made signals from satellites indicates that propagation is not limited to such ducts, since VLF signals can be received over very large regions in space [Leiphart et al, 1962]. Direct evidence for the existence of diffuse whistlers not associated with ducts has also been obtained from rocket flights by Cartwright [1964b].…”

Section: Another New •Ype Of Whistler the Pro•on Whistler Has Been mentioning

confidence: 86%

Advances in ionospheric physics in the rocket and satellite era

Schmerling¹

1966

Reviews of Geophysics

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With the systematic use of rockets and satellites, a great deal of progress has been made in increasing our knowledge and understanding of the ionosphere and the interaction of radio waves with a magnetoplasma. This paper attempts to summarize the major results obtained during the last six years. During this period, helium was found to be an important atmospheric constituent; topside sounders produced the first survey of the electron distribution above the peak of the F region; several types of plasma resonance were discovered; electron temperatures were observed to be systematically in excess of neutral temperatures, even at night; and new types of whistlers were observed. Steady progress was made in establishing the sources of ionization, from the cosmic rays effective below 70 km to the particular regions in the solar X‐ray and UV emissions responsible for ionization at greater altitudes. Less progress has been made in understanding the mechanisms of electron loss, since uncertainties still exist about reaction rates, the role of minor constituents, and the contributions of electrodynamic transport. As a result of the observations made during the past six years, a new picture of the ionosphere is emerging which is very different from the old one of layers produced in an isothermal atmosphere by monochromatic radiation. Although the new picture is much more complicated, it is firmly based on observation, and it holds out a real hope that the solution of some outstanding problems is now within reach.

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Section: Another New •Ype Of Whistler the Pro•on Whistler Has Been mentioning

confidence: 86%

Advances in ionospheric physics in the rocket and satellite era

Schmerling¹

1966

Reviews of Geophysics

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“…These transionospheric experiments were studied by other researchers 5 , who interpreted the results graphically. Figure 3 below shows the minimum cumulative transmission loss of an 18KHz signal passing vertically upward, based on measurements by the US LOFTI-1 satellite orbiting above the ionosphere.…”

Section: Experimental Validation Of Propagation Below Plasma Frequencymentioning

confidence: 96%

Interplanetary radio transmission through serial ionospheric and material barriers

Fields

Kennedy²,

Roy³

et al. 2013

Acta Astronautica

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A usual first principle in planning radioastronomy observations is that monitoring must be carried out well above the ionospheric plasma cutoff frequency (~5 MHz). Before space probes existed, radioastronomy was almost entirely done above 6 MHz, and this value is considered a practical lower limit by most radioastronomers. Furthermore, daytime ionization (especially D-layer formation) places additional constraints on wave propagation, and waves of frequency below 10-20 MHz suffer additional significant attenuation. More careful calculations of wave propagation through the earth's ionosphere suggest that for certain conditions (primarily the presence of a magnetic field) there may be a transmission window well below this assumed limit. Indeed, for receiving extraterrestrial radiation below the ionospheric plasma cutoff frequency, a choice of VLF frequency appears optimal to minimize loss. The calculation, experimental validation, and conclusions are presented here. This work demonstrates the possibility of VLF transmission through the ionosphere and various subsequent material barriers. Implications include development of a new robust communications channel, communications with submerged or subterranean receivers / instruments on or offworld, and a new approach to CETI.

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“…Measurements of the impedance of electric dipole antennas in the low-voltage linear regime have been performed using both rocket and satellite probes [Leiphart et al, 1962;Shawhan and Gumerr, 1968;Grard and Tunaley, 1968;Gurnett et al, 1969;Koons et al, 1970]. These measurements showed that the impedance of the plasma sheath surrounding the antenna elements dominated the impedance at the antenna terminals.…”

Section: Introductionmentioning

confidence: 99%

Impedance measurements on a VLF multiturn loop antenna in a space plasma simulation chamber

Koons¹,

Dazey²,

Edgar³

1984

Radio Science

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The Space Sciences Laboratory of The Aerospace Corporation is presently defining an experiment to test a loop antenna configuration for a VLF transmitter in the ionosphere. The primary objectives of the experiment are to validate existing models for radiation by a loop antenna and to study the performance of the antenna in the ionospheric plasma. A one‐third scale model of the antenna has been constructed. Impedance measurements have been made on the model in a 5‐m diameter space plasma simulation chamber at NASA Lewis Research Center. The measurements confirm that the reactance of the antenna in an ionospheric plasma is essentially identical to its free space self‐inductance. The effective series resistance of the circuit increases with frequency. The losses are attributed to power transferred to plasma turbulence.

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Penetration of the Ionosphere by Very-Low-Frequency Radio Signals-Interim Results of the LOFTI I Experiment

Cited by 31 publications

References 1 publication

Advances in ionospheric physics in the rocket and satellite era

Advances in ionospheric physics in the rocket and satellite era

Interplanetary radio transmission through serial ionospheric and material barriers

Impedance measurements on a VLF multiturn loop antenna in a space plasma simulation chamber

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