Variations in the geomagnetic cutoff rigidity of CR in the period of magnetospheric disturbances of May 2005: Their correlation with interplanetary parameters

The correlation between the rigidities of a geomagnetic cutoff, obtained using the global spectrographic survey method, and by trajectory tracing of CR particles in the magnetic field of the Ts03 Tsyganenko magnetosphere model (2001–2003) and the Dst variation and interplanetary parameters, was studied for the May 15–19, 2005, period of interplanetary and geomagnetic disturbances.     

Variations in the Geomagnetic Cutoff Rigidity during the Magnetic Storm in March 2015

Variations in the planetary system of the geomagnetic cutoff rigidity during the moderate geomagnetic storm in March 2015 are calculated on the basis of data from cosmic-ray measurements at the world network of stations. The distance to the subsolar point and the radius of the ring current are calculated on the basis of the axisymmetric restricted Earth’smagnetosphere model that takes into account currents at the magnetopause and the ring current. The contribution of the ring current to variations in the geomagnetic cutoff rigidity and to the disturbance storm time (Dst) index is also determined within this model.     

Effect of strongly perturbed magnetosphere on the cosmic-ray cutoff rigidity

Comprehensive determination of the cosmic-ray cutoff rigidity in strongly perturbed periods has been performed for a number of stations located at different latitudes. To calculate the geomagnetic cutoffs by tracing the trajectories of cosmic-ray particles in the magnetic field of the magnetosphere, the model of strongly perturbed magnetosphere was used [1–3]. The diurnal anisotropy of the geomagnetic cutoff rigidity in the minimum of D _st variation in the geomagnetic field has been estimated.     

Comparing the geomagnetic thresholds of cosmic rays for two empirical models of the magnetosphere during the period of an extreme geomagnetic storm in November 2003

The accuracy of determining the geomagnetic cutoff rigidity (the geomagnetic threshold) is closely related to that of describing the magnetic field of the magnetosphere with the model used for calculations. Geomagnetic thresholds are calculated for two empirical models of the magnetosphere, Ts0l and Ts04, constructed on the basis of the same initial experimental data. The Ts01 model describes the average magnetosphere for certain conditions in the solar wind and interplanetary field. The Ts01 model focuses on describing the large-scale evolution of magnetospheric currents during a storm. A comparison of the geomagnetic thresholds for Ts0l and Ts04 with experimental thresholds calculated by the Spectrographic Global Survey from data of the CR global network stations shows that the Ts01 model describes the magnetic field of the magnetosphere more realistically. Our study was conducted for the period of a strong geomagnetic storm in November 2003.     

Poynting flux impulses and the ionospheric switching of geomagnetic substorms

Observations were made of impulse events in Poynting flux calculated from electric and magnetic disturbances encountered by the Polar satellite when on high-latitude field-lines in the magnetotail. These were found to be coincident within±6 min with impulsive spikes in cosmic radio background absorption in the D region of the ionosphere as detected by the Imaging Riometer for Ionospheric Studies riometer in Finland. They were also coincident with substorm onset at the same geomagnetic latitude as determined by a change of gradient in International Monitor for Auroral Geomagnetic Effects’ X-component magnetograms. The interpretation of the observations was that magnetospheric compression waves from the geomagnetic equator region of the magnetotail were coupling to progressively initiate field-guided Alfvén shear waves towards higher geomagnetic latitudes over a large volume of the magnetosphere. The study suggested that they were then able either directly or indirectly to ionise the D region of the ionosphere and in the process to cut deep electrically conducting channels between the magnetosphere and the ionosphere through which currents could flow and initiate the characteristic signature of geomagnetic substorms in ground magnetograms.     

Geomagnetic Control of the Spectrum of Traveling Ionospheric Disturbances Based on Data from a Global GPS Network

An attempt is made to verify the hypothesis on the role of geomagnetic disturbances as a factor determining the intensity of traveling ionospheric disturbances (TIDs). To improve the statistical validity of the data, we used the method of global spatial averaging of disturbance spectra of the total electron content (TEC), which is based on the new GLOBDET technology. To characterize the TID intensity quantitatively, we propose using a new global index of the degree of disturbance, which is equal to the mean value of the r.m.s. TEC variations within the chosen range of TID periods (20-60 min in the present case). The analysis was made for a set of 100 to 300 GPS stations, and for 10 days with different levels of geomagnetic activity (the Dst index varied from -13 to -321 nT and the Kp index, from 3 to 9). It was found that as the magnetic disturbance increases, the total intensity of TIDs also increases monotonically; however, the latter correlates not with the absolute value of Dst but with the value of the time derivative of Dst (the maximum correlation coefficient reaches -0.94). The delay about 2 h in the TID response is consistent with the viewpoint that TIDs are generated in auroral regions and propagate toward the equator with a velocity of about 300-400 m/s.     

Detailed comparison of observed dose-time profile of October 19-20, 1989 SPE on Mir with model calculations.

The dose rate dynamics of the October 19-20, 1989 solar energetic particle (SPE) event as observed by the Liulin instrument onboard the Mir orbital station was analyzed in light of new calculations of the geomagnetic cutoff and improved estimates of the >100 MeV energy spectra from the GOES satellite instrument. The new calculations were performed using the as-flown Mir orbital trajectory and includes time variations of the cutoff rigidity due to changes in the Kp index. Although the agreement of total event integrated calculated dose to the measured dose is good, it results from some measured dose-time profile being higher and some lower than model calculations. They point to the need to include the diurnal variation of the geomagnetic cutoff and modifications of the cutoffs to variations in Kp in model calculations. Understanding of such events in light of the upcoming construction of the International Space Station during the period of maximum solar activity needs to be vigorously pursued.     

Diurnal variations in cosmic ray intensity caused by high latitude magnetospheric-ionospheric current systems

Cosmic ray intensity measurements obtained with the neutron monitors at Thule (geomagnetic latitude, 84.8°) and McMurdo (geomagnetic latitude, −79.9°) in 2007–2009 were used to test the effect of the magnetic field generated by magnetospheric currents flowing along geomagnetic field lines in the high latitude region on cosmic ray intensity. The existence of such a relation in a region where the geomagnetic field lines are virtually radial should revise our concept of the unimpeded access that cosmic ray particles have to the Earth’s atmosphere.     

Effect of change in large and fast solar wind dynamic pressure on geosynchronous magnetic field

We present a comparison of changes in large and sharp solar wind dynamic pressure, observed by several spacecraft, with fast disturbances in the magnetospheric magnetic field, measured by the geosynchronous satellites. More than 260 changes in solar wind pressure during the period 1996--2003 are selected for this study. Large statistics show that an increase (a decrease) in dynamic pressure always results in an increase (a decrease) in the magnitude of geosynchronous magnetic field. The amplitude of response to the geomagnetic field strongly depends on the location of observer relative to the noon meridian, the value of pressure before disturbance, and the change in amplitude of pressure.     

Effects of long-range interactions on the dynamics of ions in aqueous solution

Molecular dynamics simulations have been carried out for a Br⁻ ion in aqueous solution in order to establish the effect of truncation of long-range interactions on the dynamical properties of the ion. Simulations using smooth truncation of the potential at different cutoff radii were carried out and compared to results using the Ewald summation method. It is shown that when small cutoffs are applied (i.e. R_c = 8Å), the calculations yield low ionic diffusion coefficients relative to experiment, as well as short-time dynamical behavior which is inconsistent with the Ewald calculations. As the cutoff is increased, the results approach both the Ewald and the experimental results. In contrast to the results with the truncated potential, the short-time dynamical behavior of the hydrated bromide ion obtained with the Ewald method can be described by simple Langevin dynamics.     

Excitation of a magnetospheric maser through modification of the Earth’s ionosphere by high-power HF radio emission from a ground-based transmitter

A method for controlled excitation of a magnetospheric maser through the production of artificial density ducts by high-power HF radio emission from the Earth’s surface has been proposed and implemented in an in-situ experiment. Artificial density ducts allow one to affect the maser resonator system and the excitation and propagation of low-frequency electromagnetic waves in a disturbed magnetic flux tube. The experimental data presented here were obtained at the mid-latitude Sura heating facility. The characteristics of electromagnetic and plasma disturbances at outer-ionosphere altitudes were measured using the onboard equipment of the DEMETER satellite as it passed through the magnetic flux tube rested on the region of intense generation of artificial ionospheric turbulence.     

Cutoff frequencies in planar optical waveguides with arbitrary index profiles: An efficient numerical method

A numerical method for obtaining mode cutoffs for planar waveguides with arbitrary index profiles is developed. The method is based on the Galerkin method in which the wave equation for modes at cutoff is converted to a matrix eigenvalue equation using a set of orthogonal basis functions. Due to different boundary conditions, we have identified two separate cases; one, in which the cover and the substrate indices are identical leading to same behavior of the field at cutoff in these two regions and, the other, in which the two indices are different and hence, the field behaves differently. We have accordingly chosen different basis functions for the two cases. The method results in a generalized matrix eigenvalue problem which has been converted to a standard symmetric matrix eigenvalue analytically. The method has been used to obtain mode cutoffs for waveguides with a variety of index profiles. Comparisons with available exact results show that very good accuracies can be obtained with moderate matrix sizes.     

Variations of cut-off rigidity in Irkutsk

According to the ground-based measurements of cosmic ray intensity on the worldwide network of stations and GOES spacecrafts, variations in cut-off rigidity in Irkutsk for the period 2004–2005 have been calculated. The calculated variations in cut-off rigidity are presented along with the Dst variations of the geomagnetic field.     

Time fluctuations of charged and neutral cosmic-ray component fluxes as measured in the region of the brazilian magnetic anomaly

Summary Measurements of charged particles, gamma emission and neutrons were fulfilled on balloon in the region of the Brazilian magnetic anomaly on 8 November 1991. The flight lasted approximately 18 hours, including 15 hours on the ceiling at the height of 32 km just during the beginning of the recovery phase of the moderate geomagnetic storm. The main conclusion from the analysis of the obtained experimental data is the following:a) the fluxes of charged and neutral particles were measured and are in agreement with the data of previous works for the close values of geomagnetic cut-off rigidity;b) no sporadic increases of charged- and neutral-particle fluxes were recorded;c) the pulsations of charged particles, gamma-rays and neutrons with characteristic time of ≈ 30 min were found. The sporadic pulsations of charged particles and gamma-rays with shorter periods were observed too. But later pulsations were absent in the neutron flux data. This points to the magnetospheric origin of the observed phenomenon.     

First and second order non-equilibrium phase transition and evidence for non-extensive Tsallis statistics in Earth’s magnetosphere

In this paper strong evidence is provided for significant far from equilibrium phase transition processes in the Earth’s magnetosphere as revealed by the nonlinear analysis of in situ observations. These results constitute the solid base for the solution of the durable controversy about the chaotic or non-chaotic character of the magnetospheric dynamics. During the last two decades the concept of low dimensional chaos was supported by theoretical and experimental methods by our group in Thrace and others scientists, as an explicative paradigm of the magnetospheric dynamics including substorm processes. In parallel, the concept of self-organized criticality (SOC) and space-time intermittency was introduced as new and opposing to low dimensional chaos concepts for modeling the magnetospheric dynamics. Novel results concerning the nonlinear analysis of in situ space plasma data (magnetic-electric field, energetic particles and bulk plasma flow time series) obtained by the Geotail spacecraft presented in this paper for the first time reveal the following: (a) Coexistence of SOC and chaos states in the magnetospheric system and global phase transition from one state to the other during substorms. (b) Strong intermittent turbulent character of the magnetospheric system at the SOC or the low dimensional chaos states. (c) Clear indications for non-extensivity and q-Gaussian statistics during periods of low dimensional and chaotic dynamics of the magnetosphere. (d) Low dimensional and nonlinear space plasma dynamics in the day side magnetopause and bow shock dynamics. The dual character of the magnetospheric dynamics including low dimensional chaotic (coherent) and high dimensional turbulent states, as supported in this paper, is in agreement and verifies previous theoretical and experimental studies.     

Cutoff dependence of vacuum properties for nucleon-meson quantum field theories

Pure vacuum effects for renormalizable nucleon-meson field theories are studied using a variant of the Pauli-Villars regularization scheme with finite cutoffs. In particular, the renormalized vacuum contribution to the one-nucleon-loop effective potential and scalar density are studied. It is found that one must use cutoffs of many GeV in order for these quantities to approximate well the infinite cutoff results and that a cutoff of two GeV or less yields the opposite sign from the infinite cutoff limit. This suggests that important contributions to these one-nucleon-loop vacuum quantities come from scales of order five GeV - a scale at which degrees of freedom other than nucleons and mesons may well be relevant.     

Study of Cross-Correlation between Information Matrixes of Observation of the URAGAN Hodoscope and Dst Index

Cross-correlation between observation matrixes of the URAGAN muon hodoscope and the Dst index was studied. Functions of total intensity and anomaly were introduced. The results of calculations of cross-correlations on 2D diagrams were considered. It was shown that time periods with increased geomagnetic activity were almost always preceded by time periods with increased values of the modulus of the Pearson correlation coefficient.

     

A simple 2D SOC model for one of the main sources of geomagnetic disturbances: Flares

We introduce a simple model for solar flares, one of the main sources of geomagnetic disturbances. We have obtained power-laws for the probability distribution functions of some relevant physical characteristics of flares which could serve as the fingerprint of a critical state at the base of such phenomena and, given that we have not introduced a fine tune mechanism, of self-organized criticality. We compare our results with some recent experimental work on the statistics of flares and analyze the possible connection of these power laws with others already found by our group in geomagnetic disturbances distributions. We also present some limitations of our model as well as possible extensions and corrections to be taken into account in future works.     

Magnetospheric dynamics during the storm of February 14, 2009

The structure of the magnetic field in the magnetospheric during the storm of February 14, 2009 is studied. The model parameters that characterize the magnetospheric magnetic field are calculated every hour on the basis of solar wind data and the evolution of the magnetic field during the storm is reproduced using the A2000 model of the Earth’s magnetosphere. It is shown that extremely quiet geomagnetic conditions in 2009 promoted the expansion of the magnetosphere and were favorable for the formation of magnetic-island-like structures (plasmoids) in the geomagnetic tail. It is ascertained that negative variations in the B_z component could occur in the nightside magnetosphere in situations where the magnetic flux through the tail lobes exceeded certain thresholds, which depend on the parameters of the magnetospheric current systems. It is shown that the formation of magnetic islands decreases the magnetic flux through the tail lobes and prevents excessively strong development of the magnetic field in the tail.     

Precise numerical results for limit cycles in the quantum three-body problem

The study of the three-body problem with short-range attractive two-body forces has a rich history going back to the 1930s. Recent applications of effective field theory methods to atomic and nuclear physics have produced a much improved understanding of this problem, and we elucidate some of the issues using renormalization group ideas applied to precise nonperturbative calculations. These calculations provide 11-12 digits of precision for the binding energies in the infinite cutoff limit. The method starts with this limit as an approximation to an effective theory and allows cutoff dependence to be systematically computed as an expansion in powers of inverse cutoffs and logarithms of the cutoff. Renormalization of three-body bound states requires a short range three-body interaction, with a coupling that is governed by a precisely mapped limit cycle of the renormalization group. Additional three-body irrelevant interactions must be determined to control subleading dependence on the cutoff and this control is essential for an effective field theory since the continuum limit is not likely to match physical systems (e.g., few-nucleon bound and scattering states at low energy). Leading order calculations precise to 11-12 digits allow clear identification of subleading corrections, but these corrections have not been computed.