scholarly journals Spectral features of stimulated electromagnetic emission, measured in the 4.3-9.5 MHz pump wave frequency range

2001 ◽  
Vol 28 (16) ◽  
pp. 3103-3106 ◽  
Author(s):  
V. L. Frolov ◽  
E. N. Sergeev ◽  
E. N. Ermakova ◽  
G. P. Komrakov ◽  
P. Stubbe
Keyword(s):  
Pump Wave ◽  
Electromagnetic Emission ◽  
Wave Frequency ◽  
Spectral Features ◽  
Frequency Range ◽  
Pump Wave Frequency ◽  
Stimulated Electromagnetic Emission

scholarly journals Directional features of the downshifted peak observed in HF-induced stimulated electromagnetic emission spectra obtained using an interferometer

2006 ◽  
Vol 24 (7) ◽  
pp. 1819-1827 ◽  
Author(s):  
E. D. Tereshchenko ◽  
R. Yu. Yurik ◽  
B. Z. Khudukon ◽  
M. T. Rietveld ◽  
B. Isham ◽  
...  
Keyword(s):  
High Frequency ◽  
Source Region ◽  
Emission Spectra ◽  
Electromagnetic Emission ◽  
Spectral Features ◽  
Frequency Range ◽  
Pump Frequency ◽  
Ionospheric Modification ◽  
Stimulated Electromagnetic Emission ◽  
Magnetic Zenith

Abstract. A high frequency (HF) ionospheric modification experiment was carried out between 25 September and 8 October 2004, using the EISCAT HF transmitter located near Tromsø, Norway. During this experiment the spectra of the stimulated HF sideband waves (stimulated electromagnetic emission or SEE) induced by the HF pump were observed using an interferometer consisting of three spaced receiving antennas with baselines both along and perpendicular to the meridian, and a multi-channel coherent receiver, installed in the vicinity of the HF facility. The transmitter operated at 4040kHz and its antenna beam was scanned to angles of 0°, 7°, 14°, and 21° south from vertical, pausing 4min at each position. This paper focuses on features of the downshifted peak (DP) emission, which has not been as thoroughly studied as many of the other SEE spectral features observable within the EISCAT pump frequency range. It was found that the signal-weighted direction of the DP source region remained within 5° of magnetic zenith as the HF beam was tilted between 0 and 21° south of vertical.

Dependence of stimulated electromagnetic emission on the ionosphere and pump wave

1990 ◽  
Vol 95 (A10) ◽  
pp. 17233 ◽  
Author(s):  
T. B. Leyser ◽  
B. Thidé ◽  
H. Derblom ◽  
Å. Hedberg ◽  
B. Lundborg ◽  
...  
Keyword(s):  
Pump Wave ◽  
Electromagnetic Emission ◽  
Stimulated Electromagnetic Emission

scholarly journals An interferometer experiment to explore the aspect angle dependence of stimulated electromagnetic emission spectra

2005 ◽  
Vol 23 (1) ◽  
pp. 55-74 ◽  
Author(s):  
◽  
Yu. Yurik ◽  
La Hoz ◽  
◽  
◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Electromagnetic Emission ◽  
Density Fluctuations ◽  
Spectral Features ◽  
Langmuir Turbulence ◽  
Angular Structure ◽  
Frequency Spectra ◽  
Aspect Angle ◽  
Angle Dependence ◽  
Stimulated Electromagnetic Emission

Abstract. When the Earth's ionosphere is irradiated by a radiofrequency (RF) electromagnetic wave of sufficiently high power density and tuned to match a natural E- or F-region plasma frequency, ionospheric magnetoionic wave modes may be excited and may generate RF electromagnetic sideband waves via nonlinear interactions. These secondary emissions, which may then escape from the ionosphere, have been termed stimulated electromagnetic emission or SEE. The frequency spectra of this radiation has been studied extensively, and a number of characteristic spectral features have been identified and in some cases related to particular plasma processes. The separation in frequency between the RF pump and the harmonics of the local electron gyrofrequency is critical in determining the amount of anomalous absorption suffered by the pump wave and the spectral properties of the stimulated sidebands. The pump can excite electrostatic waves which do not propagate away but can in some cases be observed via radio-wave scattering from the electron density fluctuations associated with them. These enhanced density fluctuations are created by processes commonly referred to as upper-hybrid and Langmuir turbulence. Langmuir turbulence has been the subject of 930-MHz scattering observations with antenna scanning through several pre-selected angles between the geographic and geomagnetic zenith directions, and a preference for pointing angles between the Spitze angle and geomagnetic field-aligned was identified. Other phenomena, such as the generation of enhanced electron temperatures and artificial aurora, have more recently been shown to have special behavior at similar angles, near but apparently not quite at field-aligned. In view of this evidence for angular structure in several pump-induced effects, in light of the rich variety of SEE phenomena strongly dependent on the geomagnetic field via the frequency interval between the pump and the gyrofrequency harmonics, and in view of the not yet understood but complex relationship between electrostatic fluctuations and SEE, it is of interest to investigate experimentally whether a similar angular structure is present in the various spectral features of the SEE signals and to compare the results with radar and other observations of RF-pump-induced effects. To this end we describe a simple two-element radio interferometer designed to search for aspect angle dependence of SEE features. We present an example of the initial data produced by this system, and draw preliminary conclusions based on the example data.

Theory of stimulated scattering of large-amplitude waves

1995 ◽  
Vol 53 (2) ◽  
pp. 213-222 ◽  
Author(s):  
L. Stenflo
Keyword(s):  
Dispersion Relation ◽  
Large Amplitude ◽  
Pump Wave ◽  
Low Frequency ◽  
Wave Frequency ◽  
Nonlinear Coupling ◽  
Stimulated Scattering ◽  
Pump Wave Frequency ◽  
General Dispersion ◽  
Electron Gyrofrequency

By means of the standard fluid equations, we consider the nonlinear coupling between a large-amplitude pump wave and the low-frequency modes in a collisional plasma. We derive the general dispersion relation in order to discuss the case where the pump-wave frequency is not much larger than the electron gyrofrequency.

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