Use of fractal approach to investigate ionospheric conductivity in the auroral zone

2013 ◽  
Vol 118 (7) ◽  
pp. 4108-4118 ◽  
Author(s):  
A. A. Chernyshov ◽  
M. M. Mogilevsky ◽  
B. V. Kozelov
Keyword(s):  
Auroral Zone ◽  
Ionospheric Conductivity ◽  
Fractal Approach

The diurnal and latitudinal variation of auroral zone ionospheric conductivity

1981 ◽  
Vol 86 (A1) ◽  
pp. 65 ◽  
Author(s):  
James F. Vickrey ◽  
Richard R. Vondrak ◽  
Stephen J. Matthews
Keyword(s):  
Auroral Zone ◽  
Latitudinal Variation ◽  
Ionospheric Conductivity

scholarly journals Geomagnetic disturbances on ground associated with particle precipitation during SC

2010 ◽  
Vol 28 (1) ◽  
pp. 247-265 ◽  
Author(s):  
V. Safargaleev ◽  
A. Kozlovsky ◽  
F. Honary ◽  
A. Voronin ◽  
T. Turunen
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Current System ◽  
Auroral Zone ◽  
Ionospheric Irregularity ◽  
Wind Pressure ◽  
Geomagnetic Disturbances ◽  
Equatorial Station ◽  
Ionospheric Conductivity ◽  
The Impact

Abstract. We have examined several cases of magnetosphere compression by solar wind pressure pulses using a set of instruments located in the noon sector of auroral zone. We have found that the increase in riometric absorption (sudden commencement absorption, SCA) occurred simultaneously with the beginning of negative or positive magnetic variations and broadband enhancement of magnetic activity in the frequency range above 0.1 Hz. Since magnetic variations were observed before the step-like increase of magnetic field at equatorial station (main impulse, MI), the negative declinations resembled the so-called preliminary impulse, PI. In this paper a mechanism for the generation of PI is introduced whereby PI's generation is linked to SCA – associated precipitation and the local enhancement of ionospheric conductivity leading to the reconstruction of the ionospheric current system prior to MI. Calculation showed that PI polarity depends on orientation of the background electric field and location of the observation point relative to ionospheric irregularity. For one case of direct measurements of electric field in the place where the ionospheric irregularity was present, the sign of calculated disturbance corresponded to the observed one. High-resolution measurements on IRIS facility and meridional chain of the induction magnetometers are utilized for the accurate timing of the impact of solar wind irregularity on the magnetopause.

Heterogeneity of Cerebral Blood Flow: a Fractal Approach

2000 ◽  
Vol 39 (02) ◽  
pp. 37-42 ◽  
Author(s):  
P. Hartikainen ◽  
J. T. Kuikka
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Fractal Dimension ◽  
Frontal Lobe ◽  
Fractal Analysis ◽  
Relative Dispersion ◽  
Emission Computed Tomography ◽  
Brain Blood Flow ◽  
Healthy Controls ◽  
Fractal Approach

Summary Aim: We demonstrate the heterogeneity of regional cerebral blood flow using a fractal approach and singlephoton emission computed tomography (SPECT). Method: Tc-99m-labelled ethylcysteine dimer was injected intravenously in 10 healthy controls and in 10 patients with dementia of frontal lobe type. The head was imaged with a gamma camera and transaxial, sagittal and coronal slices were reconstructed. Two hundred fifty-six symmetrical regions of interest (ROIs) were drawn onto each hemisphere of functioning brain matter. Fractal analysis was used to examine the spatial heterogeneity of blood flow as a function of the number of ROIs. Results: Relative dispersion (= coefficient of variation of the regional flows) was fractal-like in healthy subjects and could be characterized by a fractal dimension of 1.17 ± 0.05 (mean ± SD) for the left hemisphere and 1.15 ± 0.04 for the right hemisphere, respectively. The fractal dimension of 1.0 reflects completely homogeneous blood flow and 1.5 indicates a random blood flow distribution. Patients with dementia of frontal lobe type had a significantly lower fractal dimension of 1.04 ± 0.03 than in healthy controls. Conclusion: Within the limits of spatial resolution of SPECT, the heterogeneity of brain blood flow is well characterized by a fractal dimension. Fractal analysis may help brain scientists to assess age-, sex- and laterality-related anatomic and physiological changes of brain blood flow and possibly to improve precision of diagnostic information available for patient care.

The Fractal Approach to Secondary Mechanisms in SEC

2007 ◽  
Vol 30 (9-10) ◽  
pp. 1227-1249
Author(s):  
R. García‐Lopera ◽  
Juan E. Figueruelo ◽  
Iolanda Porcar ◽  
Agustín Campos ◽  
Concepción Abad
Keyword(s):  
Fractal Approach

A Fractal Approach to the Modelling and Simulation of Heterogeneous and Anisotropic Reservoirs

2019 ◽  
Author(s):  
Paul W. J. Glover ◽  
Piroska Lorinczi ◽  
Saud Al-Zainaldin ◽  
Hassan Al-Ramadhan ◽  
Saddam Sinan ◽  
...  
Keyword(s):  
Modelling And Simulation ◽  
Fractal Approach ◽  
Anisotropic Reservoirs
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