IZMIRAN

Troitsk, Russia
Troitsk, Russia
SEARCH FILTERS
Time filter
Source Type

Shibalova A.S.,Moscow State University | Obridko V.N.,IZMIRAN | Sokoloff D.D.,Moscow State University
Solar Physics | Year: 2017

Small-scale solar magnetic fields demonstrate features of fractal intermittent behavior, which requires quantification. For this purpose we investigate how the observational estimate of the solar magnetic flux density B depends on resolution D in order to obtain the scaling ln BD= − kln D+ a in a reasonably wide range. The quantity k demonstrates cyclic variations typical of a solar activity cycle. In addition, k depends on the magnetic flux density, i.e. the ratio of the magnetic flux to the area over which the flux is calculated, at a given instant. The quantity a demonstrates some cyclic variation, but it is much weaker than in the case of k. The scaling obtained generalizes previous scalings found for the particular cycle phases. The scaling is typical of fractal structures. In our opinion, the results obtained trace small-scale action in the solar convective zone and its coexistence with the conventional large-scale solar dynamo based on differential rotation and mirror-asymmetric convection. © 2017, Springer Science+Business Media Dordrecht.


Ptuskin V.,IZMIRAN
EPJ Web of Conferences | Year: 2017

Brief discussion on the origin of cosmic rays at energies from 106 to 1020 eV. © The Authors, published by EDP Sciences 2016.


Puchkov V.A.,IZMIRAN
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2016

Aspect sensitive scattering of multi-frequency probe signals by artificial, magnetic field aligned density irregularities (with transverse size ∼1–10 m) generated in the ionosphere by powerful radio waves is considered. Fluctuations of received signals depending on stochastic properties of the irregularities are calculated. It is shown that in the case of HF probe waves two mechanisms may contribute to the scattered signal fluctuations. The first one is due to the propagation of probe waves in the ionospheric plasma as in a randomly inhomogeneous medium. The second one lies in non-stationary stochastic behavior of irregularities which satisfy the Bragg conditions for the scattering geometry and therefore constitute centers of scattering. In the probe wave frequency band of the order of 10–100 MHz the second mechanism dominates which delivers opportunity to recover some properties of artificial irregularities from received signals. Correlation function of backscattered probe waves with close frequencies is calculated, and it is shown that detailed spatial distribution of irregularities along the scattering vector can be found experimentally from observations of this correlation function. © 2016 Elsevier B.V.


Gulyaeva T.L.,IZMIRAN
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2017

A statistical analysis is undertaken on ICME's efficiency in producing the geomagnetic and ionospheric storms. The mutually-consistent thresholds for the intense, moderate and weak space weather storms and quiet conditions are introduced with an analytical model based on relations between the equatorial Dst index and geomagnetic indices AE, aa, ap, ap(τ) and the ionospheric Vσ indices. The ionosphere variability Vσ index is expressed in terms of the total electron content (TEC) deviation from the −15-day sliding median normalized by the standard deviation for the 15 preceding days. The intensity of global positive ionospheric storm, Vσp, and negative storm, Vσn, is represented by the relative density of anomalous ±Vσ index occurrence derived from the global ionospheric maps GIM-TEC for 1999–2016. An impact of total 421 ICME events for 1999–2016 on the geomagnetic and ionospheric storms expressed by AE, Dst, aa, ap, ap(τ), Vσp, Vσn indices and their superposition is analyzed using ICME catalogue by Richardson and Cane (2010) during 24 h after the ICME start time t0. Hierarchy of efficiency of ICME → storm relation is established. The ICMEs have a higher probability (22–25%) to be followed by the intense ionospheric and auroral electrojet storms at global and high latitudes as compared to the intense storms at middle and low latitudes (18–20%) and to moderate and weak storms at high latitudes (5–17%). At the same time ICMEs are more effective in producing the moderate storms (24–28%) at the middle and low latitudes as compared to the intense and weak storms at these latitudes (13–22%) and to moderate storms at high latitudes (8–17%). The remaining cases when quiet conditions are observed after ICMEs present higher chance for a false alarm. The risk factor for a false alarm can vary from 18% if the superposition of all indices is considered, to 51–64% for individual AE, Vσp and Vσn indices. The analysis indicates that the mutually-consistent thresholds can be successfully applied to the external sources of the geomagnetic and ionospheric storms other than ICME which present challenge for the further investigation. © 2017 Elsevier Ltd


Cliver E.W.,Air Force Research Lab | Ling A.G.,Atmospheric Environmental Research | Belov A.,IZMIRAN | Yashiro S.,NASA | Yashiro S.,Catholic University of America
Astrophysical Journal Letters | Year: 2012

We suggest that the flatter size distribution of solar energetic proton (SEP) events relative to that of flare soft X-ray (SXR) events is primarily due to the fact that SEP flares are an energetic subset of all flares. Flares associated with gradual SEP events are characteristically accompanied by fast (≥1000kms-1) coronal mass ejections (CMEs) that drive coronal/interplanetary shock waves. For the 1996-2005 interval, the slopes (α values) of power-law size distributions of the peak 1-8 Å fluxes of SXR flares associated with (a) >10MeV SEP events (with peak fluxes ≥1prcm-2s-1sr-1) and (b) fast CMEs were 1.3-1.4 compared to 1.2 for the peak proton fluxes of >10MeV SEP events and 2 for the peak 1-8 Å fluxes of all SXR flares. The difference of 0.15 between the slopes of the distributions of SEP events and SEP SXR flares is consistent with the observed variation of SEP event peak flux with SXR peak flux. © 2012 The American Astronomical Society. All rights reserved.


Scaling laws for hydromagnetic dynamo in planets initially express the characteristic strength of the magnetic field through the primary values, such as the size of the conductive core of the planet, the angular rotation rate, electrical conductivity and energy flows. Most of the earlier proposed scaling laws based only on observations and assumptions about force balances. Recent and my new approaches to fully take into account the energy and induction balance has additionally expressed here in terms of primary values such important characteristics as forces, magnitudes, energies, scales and orientations of hydromagnetic fields. The direct numerical simulation of the hydromagnetic dynamo and modeling ability in a fairly wide range of parameters for the first time allowed direct test such laws. The obtained numerical geodynamo-like results for the Earth, Jupiter and partially Saturn postulated previously not identified analytically simplest law that predicts the field strength is only depended on the specific energy density of convection and the size of the dynamo area. This simplest and already widely used law was original way analytically grounded here along with other previously known and new laws. This analytic identifies the physics determining geomagnetic periodicities for jerk, secular variations and inversions. Mean period between the inversions is found to be roughly proportional to the intensity of the geomagnetic field that is confirmed by some paleomagnetic researches. Possible dynamos in Mercury, Ganymede, Uranus and Neptune are also discussed. © Pleiades Publishing, Ltd., 2014.


Gudoshnikov S.A.,Magnetic and Cryoelectronic Systems Ltd. | Liubimov B.Ya.,IZMIRAN | Usov N.A.,Magnetic and Cryoelectronic Systems Ltd.
AIP Advances | Year: 2012

The hysteresis losses of a dense assembly of magnetite nanoparticles with an average diameter D = 25 nm are measured in the frequency range f = 10 - 200 kHz for magnetic field amplitudes up to H0 = 400 Oe. The low frequency hysteresis loops of the assembly are obtained by means of integration of the electro-motive force signal arising in a small pick-up coil wrapped around a sample which contains 1 - 5 mg of a magnetite powder. It is proved experimentally that the specific absorption rate diminishes approximately 4.5 times when the sample aspect ratio decreases from 11.4 to 1. Theoretical estimate shows that experimentally measured hysteresis loops can be approximately described only by taking into account appreciable contributions of magnetic nanoparticles of both very small, D < 10 - 12 nm, and rather large, D > 30 nm, diameters. Thus the wide particle size distribution has to be assumed. © 2012 Author(s).


Akhmet'ev P.M.,IZMIRAN
Journal of Physics: Conference Series | Year: 2014

We investigate combinatorial properties of a higher invariant of magnetic lines, which is defined in the paper Akhmet'ev-1 (2013). Assume that a 3-component link L is modeled by a magnetic field B, which is represented by 3 closed magnetic lines. Main Theorem relates the integral invariant M(B) and a combinatorial invariant , defined from the Conway polynomial. As a corollary of Main Theorem, asymptotic properties for combinatorial links are proposed. The combinatorial invariant satisfies these asymptotic properties. © Published under licence by IOP Publishing Ltd.


Akhmet'ev P.M.,IZMIRAN
Journal of Geometry and Physics | Year: 2013

A particular result towards a positive solution of a problem by V.I. Arnol'd about a higher analog of the ergodic asymptotic invariant of magnetic fields is presented. © 2013 Elsevier B.V.


Gulyaeva T.L.,IZMIRAN | Arikan F.,Hacettepe University | Hernandez-Pajares M.,Polytechnic University of Catalonia | Stanislawska I.,Polish Academy of Sciences
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

The Ionospheric Weather Assessment and Forecast (IWAF) system is a computer software package designed to assess and predict the world-wide representation of 3-D electron density profiles from the Global Ionospheric Maps of Total Electron Content (GIM-TEC). The unique system products include daily-hourly numerical global maps of the F2 layer critical frequency (foF2) and the peak height (hmF2) generated with the International Reference Ionosphere extended to the plasmasphere, IRI-Plas, upgraded by importing the daily-hourly GIM-TEC as a new model driving parameter. Since GIM-TEC maps are provided with 1- or 2-days latency, the global maps forecast for 1 day and 2 days ahead are derived using an harmonic analysis applied to the temporal changes of TEC, foF2 and hmF2 at 5112 grid points of a map encapsulated in IONEX format (-87.5°:2.5°:87.5°N in latitude, -180°:5°:180°E in longitude). The system provides online the ionospheric disturbance warnings in the global W-index map establishing categories of the ionospheric weather from the quiet state (W=±1) to intense storm (W=±4) according to the thresholds set for instant TEC perturbations regarding quiet reference median for the preceding 7 days. The accuracy of IWAF system predictions of TEC, foF2 and hmF2 maps is superior to the standard persistence model with prediction equal to the most recent 'true' map. The paper presents outcomes of the new service expressed by the global ionospheric foF2, hmF2 and W-index maps demonstrating the process of origin and propagation of positive and negative ionosphere disturbances in space and time and their forecast under different scenarios. © 2013 Elsevier Ltd.

Loading IZMIRAN collaborators
Loading IZMIRAN collaborators