The results of comparative studies of the electrically conductive properties of Co69Fe4Cr4Si12B11 glass coated amorphous microwires obtained during their heat treatment in a conventional furnace and by the Joule heating method are presented. The fully crystallized microwire dramatically changes its electrically conductive properties. We found that the crystallized microwire has a temperature coefficient of resistance, alpha = 315*10(-6) 1/degrees C. The crystallized microwire was used as a reference resistance thermometer under Joule heating for determining the temperature of the microwire as a function of the applied thermal power T(P). This dependence obtained was used to determine the temperature dependence of the resistance R-M(T) of other microwire samples in an amorphous or partially crystallized state of the same series. The proposed method allows to select thermal modes during Joule annealing of microwires and to compare the resistive, magnetic and structural-phase properties of microwires after thermal effects.

The present work describes the investigation of electrical and magnetic properties of the glass-coated Co-rich amorphous ferromagnetic microwires, having typical metallic core diameters d = 13-20 mm and tailoring by the direct current Joule heating. During this treatment, a continuous monitoring of the microwire condition was carried out, measuring its resistance by means of a DC bridge circuit. The heating of the microwire sample was provided by a direct current in the range from 20 mA to 63 mA. In this heating currents range, the microwires show a slight change in their resistivity. After annealing the resistivity of microwires may increase of about 1% with respect to as-prepared one. Depends on the heating current, the hysteresis loops of annealed microwires demonstrated the transition from a quasi linear type to a bistable one and vice versa. The maximum of the giant magnetic impedance ratio was observed in such microwires, which had a hysteresis loops describable by a near-zero anisotropy field. (C) 2020 Elsevier B.V. All rights reserved.

In this paper, we present the resistance measurements of the amorphous ferromagnetic Co-rich microwires (metallic nucleus diameters 15-30 mu m) during Joule heating by direct current. The heating currents were provided by a programming power supply, which allowed setting up a different heating and cooling regimes. The Wheatstone bridge circuit was used for continuous resistance monitoring during the heating process. We observed the dependences of the microwire resistance versus the time and the applied power of heating for the samples having common composition Co69Fe4Cr4Si12B11 and different diameters. It was shown that the irreversible changes of the microwire resistance were occurred during heat treatment. The microwires have gone through a crystallization phase under linear varying power in the range between 0 and 4.5 W and their relative resistance reduced by up to 10% relative to the initial values. The one-time annealing run increases the relative resistance of the microwires samples from 0.1% to 1% at the various values of maximum power. The repeated heating processes result to the reversibility of the resistance values; in that case each value of maximum applied power provides finite rise of the microwire resistance value.

Influence of Technological Parameters on Magnetic Properties of Co-Rich Amorphous Ferromagnetic Microwires A. V. Popova1, V. I. Odintsov1, I. V. Kozlov2, G. N. Elmanov2, E. V. Kostitsyna3, E. S. Gorelikov3, and S. A. Gudoshnikov1,3 1Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, (IZMIRAN), Troitsk, Moscow, Russia 2National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe shosse 31, Moscow, 115409, Russia 3National University of Science and Technology “MISiS”, Moscow, Russia

The maximum achievable parameters of magnetometers based on optomechanical quartz variometers are studied in connection with the planned transition of the international network Intermagnet to 1-s recording and the need to provide the network of Russian geomagnetic observatories with domestic magnetometers that satisfy Intermagnet requirements. The mechanism of negative feedback effect on the sensitivity threshold of a variometer with an optoelectronic angle transducer is shown. The optimization criterion for the size and shape of the magnets made of different magnetic materials is defined by the maximum ratio of the magnetic moment to the inertial moment. Theoretical and experimental evaluation of the variometer noise level is based on vicalloy and samarium–cobalt. It is shown that the frequency range of magnetometers with variometers based on vicalloy and samarium–cobalt will be bounded from above by frequencies of 1.6 and 6.4 Hz, respectively, at a threshold sensitivity of about 1 pT. These ratios of the frequency and threshold sensitivity for the given magnetic materials are probably limited for quartz variometers with an optoelectronic angle transducer.

Extremely achievable parameters of quartz torsion variometer magnetometers are investigated. Influence of instability and noise of the opto-electronic converter on a threshold of sensitivity of a magnetometer with the negative feedback (NF) is considered and extreme values of a sensitivity threshold of the magnetometer are estimated for different magnetic materials used, depths of NF and the demanded frequency range of measurements. Criteria for optimization of the sizes and a form of the magnets are determined by a condition of a maximum relation of the magnetic moment to the moment of inertia. Theoretical and experimental estimates of noise level of magnetometers on a base of vicalloy and samarium-cobalt are given. It is shown that for threshold sensitivity of the magnetometer about 1 pT, the frequency range of the magnetometer with a sensor on a base of vicalloy is limited by a frequency about 1.6 Hz, samarium-cobalt - 6.4 Hz. The received values of a frequency and threshold sensitivity for the specified magnetic materials completely meet the requirements of Intermaget for one-second data and are probably the extreme values for quartz variometers with the opto-electronic converter of angular movements. KEYWORDS: Quartz magnetic variometer; sensitivity; frequency range.

The information about Russian Internet resources for Solar-Terrestrial Physics (STP) is reported. These resources are typically provided by the leading institutes of Russian Academy of Sciences. The references on professional resources of different institutes as well as on coordinated scientific programs are briefly presented. Such resources might be considered as the virtual library on STP.Solar-Terrestrial Physics play important role in the space exploration as the human society begun to use the outer space for practical purposes. Due to the public demands on STP information we discuss the possibility to build up the amalgamated Russian Internet resources for science and education in the format of public portal on STP. This portal will lead to spreading of knowledge on STP between public and professional organizations in such areas as the geophysics, meteorology, education, media and all individuals, which are interested in the outer space explorations.

Russian Space Weather Initiatives (RSWI) support different models for space weather forecastin (http://alpha.npi.msu.su/RSWI/rswi.html). The models give the long-time (months-years) and short-time (days) predictions of the solar activity, heliospheric conditions, and dynamics of the Earth's magnetic field and radiation. Many different parameters measured from the Sun to the Earth's magnetosphere are used as inputs to the space weather models. The paper is devoted to a short overview of these models.

The polar geomagnetic research laboratory of Izmiran carries out construction on the automated digital data collection platform for operation in the remote regions including Antarctica. In view of the experience with previous instruments such as CMVS-2, a new digital magnetometer CMVS-6 was designed. CMVS-6 consists of a few separate modules: quartz sensors unit, electronic unit with cassette tape recorder, control and adjustment unit and radioisotopic thermoelectric generator (RITEG). Data sample rate is 1, 10 or 60 s (selectable) and the system includes the measurement of D, H and Z components of the magnetic field and has three channels for additional sensors with electric output. Resolution is 0.5 nT for magnetic field and 1.25 mV for electric channels. The dynamic range is 4000 nT for a magnetometer and 10 V for electric channels, but CMVS-6 can operate properly in dynamic range 1.8 times greater. The data are stored on the cassette tape recorder. Control and adjustment are necessary only for initial installation of the platform and for the data flow checking. It is planned to use the riometer, d.c. electric meter and thermometer as additional sensors. The first platform is installed in the Antarctic for testing in 1987–1988 season.

The sector structure of interplanetary magnetic field (SS IMF) have a strong effect on the geomagnetic field variations in the polar cap. It was discovered by L. Svalgaard and S. Mansurov and used to estimate the effects of solar wind in the near earth space. The regular definition of SS IMF was done based on the data from Resolute Bay and Vostok stations and is displayed in the table format at http://www.izmiran.rssi.ru/magnetism/SSIMF/index.htm. The regular definition of SS IMF based on the computer routine which include the adaptive filtering spectral analysis of geomagnetic variations. The main features of SS IMF are the reflections of variations in the regular heliospheric current sheet. The changes in the signs of SS IMF are most pronounced in the variations of Z-component on the geomagnetic observatories near 80 degrees of corrected geomagnetic latitudes. The changes of SS IMF also might be inferred from the geomagnetic data of the observatories in middle and low latitudes. As a sample we analyze the data of Moscow and Kakioka observatories for some chosen periods and shown a good coincidence with SS IMF in high latitudes. These results also confirm that the changes of the SS IMF signs have the global effects in the geomagnetic variations.