Analysis of the geomagnetic activity of the D(st) index and self-affine fractals using wavelet transforms

The geomagnetic activity of the D(st) index is analyzed using wavelet transforms and it is shown that the D(st) index possesses properties associated with self-affine fractals. For example, the power spectral density obeys a power-law dependence on frequency, and therefore the D(st) index can be viewed as a self-affine fractal dynamic process. In fact, the behaviour of the D(st) index, with a Hurst exponent H≈0.5 (power-law exponent β≈2) at high frequency, is similar to that of Brownian motion. Therefore, the dynamical invariants of the D(st) index may be described by a potential Brownian motion model. Characterization of the geomagnetic activity has been studied by analysing the geomagnetic field using a wavelet covariance technique. The wavelet covariance exponent provides a direct effective measure of the strength of persistence of the D(st) index. One of the advantages of wavelet analysis is that many inherent problems encountered in Fourier transform methods, such as windowing and detrending, are not necessary

Efficient electron heating in relativistic shocks and gamma ray burst afterglow

Electrons in shocks are efficiently energized due to the cross-shock potential, which develops because of differential deflection of electrons and ions by the magnetic field in the shock front. The electron energization is necessarily accompanied by scattering and thermalization. The mechanism is efficient in both magnetized and non-magnetized relativistic electron-ion shocks. It is proposed that the synchrotron emission from the heated electrons in a layer of strongly enhanced magnetic field is responsible for gamma ray burst afterglows.Comment: revtex

Forecasting the geomagnetic activity of the Dst Index using radial basis function networks

The Dst index is a key parameter which characterises the disturbance of the geomagnetic field in magnetic storms. Modelling of the Dst index is thus very important for the analysis of the geomagnetic field. A data-based modelling approach, aimed at obtaining efficient models based on limited input-output observational data, provides a powerful tool for analysing and forecasting geomagnetic activities including the prediction of the Dst index. Radial basis function (RBF) networks are an important and popular network model for nonlinear system identification and dynamical modelling. A novel generalised multiscale RBF (MSRBF) network is introduced for Dst index modelling. The proposed MSRBF network can easily be converted into a linear-in-the-parameters form and the training of the linear network model can easily be implemented using an orthogonal least squares (OLS) type algorithm. One advantage of the new MSRBF network, compared with traditional single scale RBF networks, is that the new network is more flexible for describing complex nonlinear dynamical systems

Multiscale time series modelling with an application to the relativistic electron intensity at the geosynchronous orbit

In this paper, a Bayesian system identification approach to multiscale time series modelling is proposed, where multiscale means that the output of the system is observed at one(coarse) resolution while the input of the system is observed at another (One) resolution. The proposed method identifies linear models at different levels of resolution where the link between the two resolutions is realised via non-overlapping averaging process. This averaged time series at the coarse level of resolution is assumed to be a set of observations from an implied process so that the implied process and the output of the system result in an errors-in-variables ARMAX model at the coarse level of resolution. By using a Bayesian inference and Markov Chain Monte Carlo (MCMC) method, such a modelling framework results in different dynamical models at different levels of resolution at the same time. The new method is also shown to have the ability to combine information across different levels of resolution. An application to the analysis of the relativistic electron intensity at the geosynchronous orbit is used to illustrate the new method

Validation of single spacecraft methods for collisionless shock velocity estimation

The velocity of a collisionless shock (CS) is an important parameter in the determination of the spatial scales of the shock. The spatial scales of the shock determine the processes that guide the energy dissipation, which is related to the nature of the shock. During the pre-ISEE era, estimations of relative shock-spacecraft velocity (VSh) were based on spatial scales of the shock front regions, in particularly the foot. Multispacecraft missions allow more reliable identification of VSh. The main objective of this study is to examine the accuracy of two single spacecraft methods, which use the foot region of quasi-perpendicular shocks in order determine VSh. This is important for observational shock studies based on a single spacecraft data such as Venus Express (VEX) and THOR, a proposed single spacecraft mission of European Space Agency. It is shown that neither method provides estimates with an accuracy comparable to multipoint measurements of VSh. In the absence of alternative techniques to identify the VSh and therefore the spatial scales of the shocks, the methods can be used to provided order of magnitude estimations for the spatial scales of the shock front. Observations of the Venusian bow shock from VEX data have been used as an illustrative example for the application of these methods to estimate the shock spatial scale and the corresponding errors of this estimation. It is shown that the spatial width of the ramp of the observed shock is L ∼ 3.4 ± 1.4c/ωpe

Simulation model of sphygmographic signal for systems of peripheral circulation diagnostic.

Проект виконано на кафедрі біотехнічних систем Тернопільського національного технічного університету імені Івана Пулюя.Роботу присвячено питанням розроблення імітаційної моделі сфігмографічних сигналів для задачі тестування програмного забезпечення систем діагностики периферійного кровообігу. Розглянуто природу сфігмографічних сигналів, їхні параметри, та сформульовано вимоги до імітаційної моделі. Розроблено імітаційну модель у вигляді вектора значень сигналу в межах періоду з періодичним його повторенням та у вигляді суміші заникних синусоїд.The work is devoted to the development of a simulation model of sphygmographic signals for the task of testing the software of systems of diagnostics of peripheral circulation. The nature of sphygmographic signals, their parameters, and requirements for the simulation model are considered. A simulation model is developed as a vector of signal values within a period with its periodic repetition and as a mixture of stagnant sinusoids.ЗМІСТ ВСТУП 9 РОЗДІЛ 1. ЗАДАЧА ДІАГНОСТИКИ ЗА СФІГМОГРАФІЧНИМ СИГНАЛОМ 11 1.1 Природа та особливості породження сфігмографічного сигналу 11 1.2 Методика проведення сфігмографічного дослідження 12 1.3 Структура сфігмограми в нормі 14 1.4 Типи сфігмограм в нормі і при порушеннях 20 1.5 Непрямі способи відбору сфігмографічних сигналів 23 1.6 Висновки до розділу 1 27 РОЗДІЛ 2. СПОСОБИ ОТРИМАННЯ СФІГМОГРАФІЧНИХ СИГНАЛІВ 28 2.1 Апаратні методи одержання сигналів пульсової хвилі 28 2.2 Технічні особливості роботи пульсоксиметрів 29 2.3 Математичне моделювання сфігмографічних сигналів 33 2.4 Висновки до розділу 2 38 РОЗДІЛ 3. ВІДБІР СФІГМОГРАФІЧНОГО СИГНАЛУ 39 3.1 Оптичні чутливі елементи 39 3.2 Відомі схемотехнічні рішення 41 3.3 Висновки до розділу 3 43 РОЗДІЛ 4. КОМП’ЮТЕРНЕ ІМІТАЦІЙНЕ МОДЕЛЮВАННЯ СФІГМОГРАФІЧНОГО СИГНАЛУ 44 4.1 Імітаційне моделювання сигналу пульсової хвилі 44 4.2 Імітаційна модель у вигляді вектора значень сфігмографічного сигналу 45 4.3 Імітаційна модель сфігмографічного сигналу у вигляді суміші заникних синусоїд 50 4.4 Висновки до розділу 4 51 РОЗДІЛ 5. СПЕЦАЛЬНА ЧАСТИНА 53 5.1 Методика проведення медико-біологічних досліджень 53 5.2 Обґрунтування вибору УДК напряму наукового дослідження 55 РОЗДІЛ 6. ОБГРУНТУВАННЯ ЕКОНОМІЧНОЇ ЕФЕКТИВНОСТІ 58 6.1 Науково-технічна актуальність науково-дослідної роботи 58 6.2 Розрахунок витрат на проведення науково-дослідної роботи 59 6.3. Науково-технічна ефективність науково-дослідної роботи 65 6.4 Висновки до розділу 6 69 РОЗДІЛ 7. ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ 70 7.1 Охорона праці 70 7.2 Безпека в надзвичайних ситуаціях 71 РОЗДІЛ 8. ЕКОЛОГІЯ 80 8.1 Актуальність екологічних проблем 80 8.2 Шкідливий вплив на довкілля при виготовленні свігмометра 82 8.3 Заходи по охороні навколишнього середовища при промислових процесах виготовлення даного сфігмометра 83 ЗАГАЛЬНІ ВИСНОВКИ 85 Бібліографія 86 ДОДАТКИ 8

Nonzero electron temperature effects in nonlinear mirror modes

The nonlinear theory of the magnetic mirror instability (MI) accounting for nonzero electron temperature effects is developed. Based on our previous low-frequency approach to the analysis of this instability and including nonzero electron temperature effects a set of equations describing nonlinear dynamics of mirror modes is derived. In the linear limit a Fourier transform of these equations recovers the linear MI growth rate in which the finite ion Larmor radius and nonzero electron temperature effects are taken into account. When the electron temperature T-e becomes of the same order as the parallel ion temperature T the growth rate of the MI is reduced by the presence of a parallel electric field. The latter arises because the electrons are dragged by nonresonant ions which are mirror accelerated from regions of high to low parallel magnetic flux. The nonzero electron temperature effect also substantially modifies the mirror mode nonlinear dynamics. When T-e similar or equal to T the transition from the linear to nonlinear regime occurred for wave amplitudes that are only half that which was inherent to the cold electron temperature limit. Further nonlinear dynamics developed with the explosive formation of magnetic holes, ending with a saturated state in the form of solitary structures or cnoidal waves. This shows that the incorporation of nonzero temperature results in a weak decrease in their spatial dimensions of the holes and increase in their depth

Whistler Mode Waves Below Lower Hybrid Resonance Frequency: Generation and Spectral Features

Equatorial noise in the frequency range below the lower hybrid resonance frequency, whose structure is shaped by high proton cyclotron harmonics, has been observed by the Cluster spacecraft. We develop a model of this wave phenomenon which assumes (as, in general, has been suggested long ago) that the observed spectrum is excited due to loss-cone instability of energetic ions in the equatorial region of the magnetosphere. The wave field is represented as a sum of constant frequency wave packets which cross a number of cyclotron resonances while propagating in a highly oblique mode along quite specific trajectories. The growth (damping) rate of these wave packets varies both in sign and magnitude along the ray path, making the wave net amplification, but not the growth rate, the main characteristic of the wave generation process. The growth rates and the wave amplitudes along the ray paths, determined by the equations of geometrical optics, have been calculated for a 3D set of wave packets with various frequencies, initial L-shells, and initial wave normal angles at the equator. It is shown that the dynamical spectrum resulting from the proposed model qualitatively matches observations

Mirror modes: Nonmaxwellian distributions

We perform direct analysis of mirror mode instabilities from the general dielectric tensor for several model distributions, in the longwavelength limit. The growth rate at the instability threshold depends on the derivative of the distribution for zero parallel energy. The maximum growth rate is always $\sim k_\parallel v_{T\parallel}$ and the instability is of nonresonant kind. The instability growth rate and its dependence on the propagation angle depend on the shape of the ion and electron distribution functions.Comment: 18 pages, 15 figures, revtex4, amsmath, amssymb,amsfonts,times, graphicx, float,verbatim,psfra

Electron Flux Dropouts at L ∼ 4.2 From Global Positioning System Satellites: Occurrences, Magnitudes, and Main Driving Factors

Dropouts in electron fluxes at L ∼ 4.2 were investigated for a broad range of energies from 120 keV to 10 MeV, using 16 years of electron flux data from Combined X-ray Dosimeter on board Global Positioning System (GPS) satellites. Dropouts were defined as flux decreases by at least a factor 4 in 12 h, or 24 h during which a decrease by at least a factor of 1.5 must occur during each 12 h time bin. Such fast and strong dropouts were automatically identified from the GPS electron flux data and statistics of dropout magnitudes, and occurrences were compiled as a function of electron energy. Moreover, the Error Reduction Ratio analysis was employed to search for nonlinear relationships between electron flux dropouts and various solar wind and geomagnetic activity indices, in order to identify potential external causes of dropouts. At L ∼ 4.2, the main driving factor for the more numerous and stronger 1-10 MeV electron dropouts turns out to be the southward interplanetary magnetic field B s , suggesting an important effect from precipitation loss due to combined electromagnetic ion cyclotron and whistler mode waves in a significant fraction of these events, supplementing magnetopause shadowing and outward radial diffusion which are also effective at lower energies