Effect of weak large-scale inhomogeneities of the auroral ionosphere on the propagation of radio waves in the shortwave range

1978 ◽  
Vol 21 (11) ◽  
pp. 1106-1110 ◽  
Author(s):  
M. G. Gel'berg ◽  
N. N. Volkov ◽  
R. S. Kukushkina
Keyword(s):  
Large Scale ◽  
Auroral Ionosphere ◽  
Radio Waves

Peculiarities of Excitation of Large-Scale Plasma Density Irregularities During Modification of the Ionospheric F 2 Region by High-Power HF Radio Waves

2016 ◽  
Vol 58 (10) ◽  
pp. 717-728 ◽  
Author(s):  
V. L. Frolov ◽  
E. A. Schorokhova ◽  
V. E. Kunitsyn ◽  
E. S. Andreeva ◽  
A. M. Padokhin
Keyword(s):  
Plasma Density ◽  
High Power ◽  
Large Scale ◽  
Radio Waves

scholarly journals Simulation study of the large-scale modification of the mid-latitude F-layer by HF radio waves with different powers

2012 ◽  
Vol 30 (8) ◽  
pp. 1213-1222 ◽  
Author(s):  
G. I. Mingaleva ◽  
V. S. Mingalev ◽  
O. V. Mingalev
Keyword(s):  
Mathematical Model ◽  
Simulation Study ◽  
High Power ◽  
Large Scale ◽  
Radio Waves ◽  
Effective Frequency ◽  
Heating Facility ◽  
Absorbed Power

Abstract. A mathematical model of the ionosphere, developed earlier, is applied to investigate the large-scale mid-latitude F-layer modification by HF radio waves with different powers. Simulations are performed for the point with geographic coordinates of the "Sura" heating facility (Nizhny Novgorod, Russia) for autumn conditions. The calculations are made for distinct cases, in which the effective absorbed power has different values belonging to the 5–100 MW range, both for nocturnal and daytime conditions. The frequency of powerful HF waves is chosen to be close to the most effective frequency for the large-scale F2-layer modification. The results of modeling indicate that the effective absorbed power can influence considerably the F-layer response to high-power radio waves in the mid-latitude ionosphere.

scholarly journals Magnetic Fields in the Spiral Galaxy NGC 6946

1993 ◽  
Vol 157 ◽  
pp. 311-312
Author(s):  
Matthias Ehle ◽  
Rainer Beck
Keyword(s):  
Magnetic Field ◽  
Spiral Galaxy ◽  
High Frequency ◽  
Uniform Magnetic Field ◽  
Large Scale ◽  
Dynamo Model ◽  
Model Parameters ◽  
Radio Waves ◽  
Spiral Pattern ◽  
Ngc 6946

High frequency polarization observations reveal the existence of a large-scale ordered magnetic field in the disk of the spiral galaxy NGC 6946. At lower frequencies the disk is no longer transparent to polarized radio waves due to Faraday depolarization. The spiral pattern of the uniform magnetic field and the distribution of polarized intensities are fairly well simulated by a dynamo model. The model parameters indicate that the dynamo does not only operate in the disk, but also in the halo.

Measurements of the direction of arrival of short radio waves reflected at the ionosphere

1951 ◽  
Vol 207 (1089) ◽  
pp. 251-267 ◽  
Keyword(s):  
Large Scale ◽  
Wave Length ◽  
Direction Of Arrival ◽  
Close Correlation ◽  
Comparison Method ◽  
Radio Waves ◽  
Frequency Range ◽  
Compressional Waves ◽  
First Order ◽  
Random Direction

Using a phase-comparison method described in another paper, measurements have been made of the direction of arrival of waves reflected at the ionosphere during normal daytime conditions, both over an oblique path corresponding to a range of 700 km. and at nearly vertical incidence. The frequency range covered was 4 to 15 Mc./see., and using pulsed signals the direction of arrival of discrete rays could be studied. The work so far carried out has been confined principally to first-order F -layer reflexions, but a few observations of second-order reflexions and of reflexions from the E region have also been made. The results show that a typical first-order F echo exhibits both rapid (second to second) fluctuations in direction and slow changes of a quasi-period of many minutes (ranging from a few up to more than 30 min.). These results confirm earlier deductions from direction-finding studies and are interpreted as indicating that large-scale and apparently random tilts occur in the ionosphere. The F layer at any point is to be regarded as usually tilted in a random direction, the r. m. s. magnitude of the tilt being of the order of 1·5 to 2° and the tilt changing at a rate corresponding to the slow directional changes observed. Some indication as to the extent of these tilts is given by experiments using two direction-measuring stations separated by 27 km. These two stations, operated simultaneously, exhibit extremely close correlation so far as the slowly changing directional deviations are concerned, both for oblique paths and at nearly vertical incidence. The results are consistent with others obtained in Australia by different methods which suggest that there are compressional waves in the atmosphere at the height of the F layer, and that these waves have a wave-length of several hundred kilometres and a velocity of some 5 to 10 km./min.

scholarly journals Fibre structure of decametric type II radio bursts as a manifestation of emission propagation effects in a disturbed near-solar plasma

2009 ◽  
Vol 27 (10) ◽  
pp. 3933-3940 ◽  
Author(s):  
A. N. Afanasiev
Keyword(s):  
Large Scale ◽  
Inhomogeneous Plasma ◽  
Density Fluctuations ◽  
Formation Mechanisms ◽  
Radio Bursts ◽  
Type Ii ◽  
Radio Waves ◽  
Propagation Effects ◽  
Type Ii Radio Bursts ◽  
Electron Density Fluctuations

Abstract. This paper addresses the fine structure of solar decametric type II radio bursts in the form of drifting narrowband fibres on the dynamic spectrum. Observations show that this structure appears in those events where there is a coronal mass ejection (CME) traveling in the near-solar space ahead of the shock wave responsible for the radio burst. The diversity in observed morphology of fibres and values of their parameters implies that the fibres may be caused by different formation mechanisms. The burst emission propagates through extremely inhomogeneous plasma of the CME, so one possible mechanism can be related to radio propagation effects. I suggest that the fibres in some events represent traces of radio emission caustics, which are formed due to regular refraction of radio waves on the large-scale inhomogeneous structure of the CME front. To support this hypothesis, I have modeled the propagation of radio waves through inhomogeneous plasma of the CME, taking into consideration the presence of electron density fluctuations in it. The calculations, which are based on the Monte Carlo technique, indicate that, in particular, the emission of the fibres should be harmonic. Moreover, the mechanism under consideration suggests that in solar observations from two different points in space, the observed sets of fibres can be shifted in frequency with respect to one another or can have a different structure. This potentially can be used for identifying fibres caused by the propagation effects.

scholarly journals Artificial optical emissions at HAARP for pump frequencies near the third and second electron gyro-harmonic

2005 ◽  
Vol 23 (5) ◽  
pp. 1585-1592 ◽  
Author(s):  
M. J. Kosch ◽  
T. Pedersen ◽  
J. Hughes ◽  
R. Marshall ◽  
E. Gerken ◽  
...  
Keyword(s):  
High Frequency ◽  
Optical Emission ◽  
Particle Interactions ◽  
Auroral Ionosphere ◽  
Radio Waves ◽  
Pump Frequency ◽  
Optical Emissions ◽  
The Third ◽  
Active Experiments ◽  
First Time

Abstract. High-power high-frequency radio waves beamed into the ionosphere cause plasma turbulence, which can accelerate electrons. These electrons collide with the F-layer neutral oxygen causing artificial optical emissions identical to natural aurora. Pumping at electron gyro-harmonic frequencies has special significance as many phenomena change their character. In particular, artificial optical emissions become strongly reduced for the third and higher gyro-harmonics. The High frequency Active Auroral Research Program (HAARP) facility is unique in that it can select a frequency near the second gyro-harmonic. On 25 February 2004, HAARP was operated near the third and passed through the second gyro-harmonic for the first time in a weakening ionosphere. Two novel observations are: firstly, a strong enhancement of the artificial optical emission intensity near the second gyro-harmonic, which is opposite to higher gyro-harmonics; secondly, the optical enhancement maximum occurs for frequencies just above the second gyro-harmonic. We provide the first experimental evidence for these effects, which have been predicted theoretically. In addition, irregular optical structures were created when the pump frequency was above the ionospheric critical frequency.Keywords. Active experiments – Auroral ionosphere – Wave-particle interactions

scholarly journals Anisotropy of ionospheric irregularities determined from the amplitude of satellite signals at a single receiver

1999 ◽  
Vol 17 (4) ◽  
pp. 508-518 ◽  
Author(s):  
E. D. Tereshchenko ◽  
B. Z. Khudukon ◽  
M. O. Kozlova ◽  
T. Nygrén
Keyword(s):  
Large Scale ◽  
Ground Level ◽  
Spatial Spectrum ◽  
Ionospheric Irregularities ◽  
Small Scale ◽  
Radio Waves ◽  
Large Scale Structures ◽  
F Region ◽  
Amplitude Fluctuations ◽  
A Chain

Abstract. A new method of determining the anisotropy parameters of small-scale irregularities in the ionospheric F region is presented and experimental results are shown. The method is based on observations of amplitude fluctuations of radio waves transmitted by satellites flying above the F region. In practice, Russian navigational satellites are used and both the amplitude and the phase of the received signal is measured on the ground level. The method determines both the field-aligned anisotropy and the field-perpendicular anisotropy and orientation of the spatial spectrum of the irregularities, assuming that the contours of constant power have an elliptic shape. A possibility of applying the method to amplitude tomography is also discussed. Using a chain of receivers on the ground level, one could locate the regions of small-scale irregularities as well as determine their relative intensities. Then the large-scale background structures could be mapped simultaneously by means of ordinary ray tomography using the phase observations, and therefore the relations of small-scale and large-scale structures could be investigated.Key words. Ionosphere (auroral ionosphere; ionospheric irregularities; instruments and techniques)

EISCAT observations of large scale electron temperture and electron density perturbations caused by high power HF radio waves

1992 ◽  
Vol 54 (11-12) ◽  
pp. 1555-1572 ◽  
Author(s):  
A.J. Stocker ◽  
F. Honary ◽  
T.R. Robinson ◽  
T.B. Jones ◽  
P. Stubbe ◽  
...  
Keyword(s):  
Electron Density ◽  
High Power ◽  
Large Scale ◽  
Radio Waves ◽  
Density Perturbations
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