On fractal properties of small-scale ionospheric irregularities

2007 ◽  
Vol 50 (4) ◽  
pp. 274-280 ◽  
Author(s):  
V. A. Alimov ◽  
F. I. Vybornov ◽  
A. V. Rakhlin
Keyword(s):  
Ionospheric Irregularities ◽  
Small Scale ◽  
Fractal Properties

Non-Linear Interaction of MHD Waves with Small-Scale Ionospheric Irregularities

2004 ◽  
Vol 61 (7-12) ◽  
pp. 1055-1071
Author(s):  
N. N. Gerasimova ◽  
V. G. Sinitsin ◽  
Yu. M. Yampolski
Keyword(s):  
Ionospheric Irregularities ◽  
Mhd Waves ◽  
Small Scale ◽  
Linear Interaction ◽  
Non Linear

scholarly journals Fractal properties of forest fires in Amazonia as a basis for modelling pan-tropical burnt area

2014 ◽  
Vol 11 (6) ◽  
pp. 1449-1459 ◽  
Author(s):  
I. N. Fletcher ◽  
L. E. O. C. Aragão ◽  
A. Lima ◽  
Y. Shimabukuro ◽  
P. Friedlingstein
Keyword(s):  
Forest Fires ◽  
Large Scale ◽  
Fire Spread ◽  
Small Scale ◽  
Burnt Area ◽  
Active Fire ◽  
Fractal Properties ◽  
Dynamic Global Vegetation Models ◽  
Vegetation Models ◽  
Global Vegetation

Abstract. Current methods for modelling burnt area in dynamic global vegetation models (DGVMs) involve complex fire spread calculations, which rely on many inputs, including fuel characteristics, wind speed and countless parameters. They are therefore susceptible to large uncertainties through error propagation, but undeniably useful for modelling specific, small-scale burns. Using observed fractal distributions of fire scars in Brazilian Amazonia in 2005, we propose an alternative burnt area model for tropical forests, with fire counts as sole input and few parameters. This model is intended for predicting large-scale burnt area rather than looking at individual fire events. A simple parameterization of a tapered fractal distribution is calibrated at multiple spatial resolutions using a satellite-derived burnt area map. The model is capable of accurately reproducing the total area burnt (16 387 km2) and its spatial distribution. When tested pan-tropically using the MODIS MCD14ML active fire product, the model accurately predicts temporal and spatial fire trends, but the magnitude of the differences between these estimates and the GFED3.1 burnt area products varies per continent.

scholarly journals Modelling the Gravitational Effects of Random Underground Density Variations

2019 ◽  
Vol 52 (6) ◽  
pp. 759-781
Author(s):  
Kevin Ridley
Keyword(s):  
Random Process ◽  
Vertical Component ◽  
Vertical Gradient ◽  
Fractal Model ◽  
Small Scale ◽  
Underground Structures ◽  
Gaussian Random Process ◽  
Tunnel Detection ◽  
Fractal Properties ◽  
Gravity Variations

Abstract A mathematical model for small-scale spatial variations in gravity above the Earth’s surface is presented. Gravity variations are treated as a Gaussian random process arising from underground density variations which are assumed to be a Gaussian random process. Expressions for two-point spatial statistics are calculated for both the vertical component of gravity and the vertical gradient of the vertical component. Results are given for two models of density variations: a delta-correlated model and a fractal model. The effect of an outer scale in the fractal model is investigated. It is shown how the results can be used to numerically generate realisations of gravity variations with fractal properties. Such numerical modelling could be useful for investigating the feasibility of using gravity surveys to locate and characterise underground structures; this is explored through the simple example of a tunnel detection scenario.

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)

scholarly journals Refined method for determining the spatial correlation interval of the fading in a single-beam decameter radio link.

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
V.P. Pashintsev ◽  
◽  
S.A. Koval ◽  
D.A. Potyagov ◽  
A.D. Skorik ◽  
...  
Keyword(s):  
Spatial Correlation ◽  
Ionospheric Irregularities ◽  
Small Scale ◽  
Radio Link ◽  
Phase Front ◽  
Single Beam ◽  
Radio Line ◽  
Refined Method ◽  
Correlation Interval ◽  
Decameter Radio

In this articlea a refined method have been developed for determining the spatial correlation interval for fading in a decameter radio link with one discrete beam (mode), which are caused by wave diffraction on small-scale ionospheric irregularities. A refined dependence of the spatial correlation interval of fading in a single-beam decameter radio line on the parameters of small-scale ionospheric irregularities, the equivalent length of the radio line and the choice of the operating signal frequency through the value of the root-mean-square deviation of fluctuations of the wave phase front at the output of the inhomogeneous ionosphere is obtained. It is shown that under conditions of disturbances (diffuseness) of the ionosphere, as well as the approach of the operating frequency of the radio line to the maximum applicable frequency, when fluctuations of the phase front of the wave at the output of the ionosphere exceed 1.25 radians, the well-known simplified expression for estimating the interval of spatial correlation of fading can be used in a single-beam decameter radio links with an error of no more than 5%.

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