Unipolar Magnetic Field Research Articles

Thermal and magnetic field structure of near-equatorial coronal holes

Coronal holes are low-density and unipolar magnetic field structures in the solar corona that trigger geomagnetic disturbances on the Earth. Hence, it is important to understand the genesis and evolutionary behavior of these coronal activity features during their passage across the solar disk. We study the day-to-day latitudinal variations of thermal and magnetic field structures of near-equatorial coronal holes. For this purpose, eight years of full-disk SOHO/EIT 195 calibrated images were used. Using the response curves of the SOHO/EIT channels and assuming thermodynamic equilibrium, we estimated the temperature structure of coronal holes. From the latitudinal variation in the magnetic pressure, we inferred the magnitude of the magnetic field structure of coronal holes. Except for the temperature T, we find that the variations in the average photon flux F, in the radiative energy E, in the area A, and in the magnitude of the magnetic field structure B of coronal holes depend on latitude. The typical average values of the estimated physical parameters are $A cm^ $, $F $, $E sec^ $, $T K$ and $ B 0.001) \, G$. When coronal holes are anchored in the convection zone, these activity features would be expected to rotate differentially. The thermal wind balance and isorotation of coronal holes with the solar plasma therefore implies a measurable temperature difference between the equator and the two poles. Contrary to this fact, the variation in the thermal structure of near-equatorial coronal holes is independent of latitude, which leads to the conclusion that coronal holes must rotate rigidly and are likely to be initially anchored below the tachocline. This confirms our previous study.

Magnetic Fields and Plasma Heating in the Sun’s Atmosphere

We use the first publicly available data from the Daniel K. Inouye Solar Telescope to track magnetic connections from the solar photosphere into the corona. We scrutinize relationships between chromospheric magnetism and bright chromospheric, transition region, and coronal plasmas. In 2022 June, the Visible Spectro-Polarimeter (ViSP) instrument targeted unipolar network within a decaying active region. ViSP acquired rastered scans with longitudinal Zeeman sensitivities of 0.25 Mx cm−2 (Fe i, 630.2 nm) and 0.5 Mx cm−2 (Ca ii, 854.2 nm). ViSP was operated in a “low” resolution mode (0.″214 slit width, spectral resolution R≈70,000 ) to produce polarization maps over a common area of 105″ × 50″. Data from the Solar Dynamics Observatory and Interface Region Imaging Spectrograph are combined to ask: Why is only a fraction of emerging flux filled with heated plasma? What is the elemental nature of the plasmas? No correlations were found between heated plasma and the properties of chromospheric magnetic fields derived from the weak field approximation, on scales below supergranules. Processes hidden from our observations control plasma heating. While improved magnetic measurements are needed, these data indicate that “the corona is a self-regulating forced system.” Heating depends on the state of the corona, not simply on boundary conditions. Heating models based upon identifiable bipolar fields, including cool loops, tectonics, and observable magnetic reconnection, are refuted for these regions with unipolar chromospheric magnetic fields.

Effect of unipolar magnetic fields on UV absorption and evaporation of water

We investigated the effects of unipolar magnetic fields (N or S polarity) on the physical properties of deionized water. Long-term experiments (15 and 25 days) revealed significant pole-dependent changes in water absorption in the UV range (186 – 230 nm), and in water evaporation. The order of absorption magnitudes was C-N-S. That is, control (C) water absorbed the most, N-pole-influenced water absorbed less, and S pole the least. The differences in absorption between N and S waters were substantial. A correlation between UV absorption values and evaporation rates was also found. The relative order of evaporation rates was the same as the order of the absorption values, also C-N-S. The evaporation rates of N and S waters were less than C water evaporation. The effects of magnetic fields were long term. The interaction of magnetic fields with water is of interest not only from a physical sciences perspective, but also in the context of the significant applications in biophysics and medicine.

Mechanism of domain walls drift in pulsed magnetic fields in iron garnet crystals

Conditions for the drift of domain walls in pulsed magnetic fields of various organization (bipolar and unipolar pulsed magnetic fields, pulse packets) are established. Dependences of domain walls drift velocity on the parameters of pulsed magnetic fields (frequency, amplitude, pulse duration) are obtained. As a result of numerical simulation of domain walls drift in a uniaxial sample, an experimentally confirmed mechanism of domain walls drift in pulsed magnetic fields is proposed. Keywords: pulsed magnetic fields, iron garnets, domain walls, dynamic domain structures, drift of domain walls.

単極磁界を用いた5軸能動位置制御型アキシャルフラックスセルフベアリングモータの開発

This paper introduces a five-axis active-controlled axial-flux self-bearing motor that uses unipolar and four-pole magnetic fields to control radial force and tilt moment of the two-pole permanent magnet rotor. The proposed method controls the only one-axis radial force and tilt moment by a unit of the rotor and stator, therefore two units are necessary for radial motion control. The stators can be placed on the double-side and single-side of the rotor. In this paper, the principle of the proposed motor is introduced, and the radial force and tilt moment are analyzed theoretically. Then two experimental devices with double-side and single-side stators are made and levitation and rotation tests are carried out. The results confirm that the proposed motor achieved stable rotation up to 900 rpm in a double-side stator and 440 rpm in a single-side stator.

Effect of Unipolar Magnetic Fields on Uv Absorption and Evaporation of Water

Effect of Unipolar Magnetic Fields on Uv Absorption and Evaporation of Water

A morphological study of unipolar magnetic fields and the relationship with sunspots

A morphological examination of the Kitt Peak photospheric magnetic maps has been made over three sunspot cycles in order to study the morphology of unipolar magnetic regions and sunspots. Unipolar magnetic regions (positive and negative) are a series of weak, large-scale longitudinal bands, extending from 0° to 60° in latitude and alternatively aligned in longitude. The first finding is that unipolar regions grow and decay with the sunspot cycle and thus are likely to be a part of the basic solar (dipolar) magnetism, not old active regions located below 30° in latitude (as have long been considered). The second finding is that positive pores and single spots (coalesced pores, often called ‘isolated’ spots or ‘independent’ spots) occur in a positive unipolar region (vice vera). Thus, the unipolar regions could be the source of single spots. The third finding is that a pair (positive and negative) of dense clusters of pores, single spots and large spots (a coalesced single spots) occur at each side of the boundary of neighboring (positive and negative) unipolar regions, forming pairs of spots across the boundary; in fact, pairs of spots do not occur in the middle of a unipolar region. The boundaries of unipolar regions are tentatively identified as the Hale boundary, where solar activities (including solar flares) occur). Thus, it is suggested that the presently accepted magnetic tube theory may need a new consideration.

A Morphological Study of Unipolar Magnetic Fields and the Relationship with Sunspots

A Morphological Study of Unipolar Magnetic Fields and the Relationship with Sunspots

Unidirectional motion of magnetic domain walls: the experiment and numerical simulation

The results of study of unidirectional motion of topologically different domain structures under the influence of periodic bipolar and unipolar magnetic field pulses applied perpendicular to the sample plane of (111) iron garnet single crystal plate are presented. The response of the domain structure to the field pulses was studied by direct observations utilizing the stroboscopic technique. Experimentally obtained dependences of the speed of unidirectional motion of stripe domains on the parameters of external bipolar pulsed magnetic field are compared with the results of numerical simulations.

One- and Two-Qubit Gates: Rabi Technique and Single Unipolar Pulses

Methods for controlling states of interacting superconducting flux qubits using power-efficient devices of fast single-quantum logic (Josephson nonlinearity cavities) are studied. One- and two-qubit quantum logical operations performed within the conventional control technique using Rabi pulses and using picosecond single unipolar magnetic field pulses are comparatively analyzed. It is shown that all main operations can be implemented with an accuracy of better than 97% due to optimization of the shape and parameters of unipolar control pulses (associated with, e.g., propagation of fluxons in transmission lines). The efficiency of the developed technique for programming a two-qubit quantum processor implementing the simplest Deutsch–Jozsa algorithm is demonstrated.

Unipolar magnetic field pulses as an advantageous tool for ultrafast operations in superconducting Josephson "atoms".

A theoretical approach to the consistent full quantum description of the ultrafast population transfer and magnetization reversal in superconducting meta-atoms induced by picosecond unipolar pulses of a magnetic field is developed. A promising scheme based on the regime of stimulated Raman Λ-type transitions between qubit states via upper-lying levels is suggested in order to provide ultrafast quantum operations on the picosecond time scale. The experimental realization of a circuit-on-chip for the discussed ultrafast control is presented.

Examining the optical intensity and magnetic field expansion factor in the open magnetic field regions associated with coronal holes

AbstractCoronal holes can be identified as the darkest regions in EUV or soft X-ray images with predominantly unipolar magnetic fields (LIRs) or as the regions with open magnetic fields (OMF). Our study reveals that only 12% of OMF regions are coincident with LIRs. The aim of this study is to investigate the conditions that affect the EUV intensity of OMF regions. Our results indicate that the EUV intensity and the magnetic field expansion factor of the OMF regions are weakly positively correlated when plotted in logarithmic scale, and that the bright OMF regions are likely to locate inside or next to the regions with closed field lines. We empirically determined a linear relationship between the expansion factor and the EUV intensity. The relationship is demonstrated to improve the consistency from 12% to 23%. The results have been published in Astrophysical Journal (Huang et al. 2019).

Spatial power spectrum of the photospheric magnetic field during solar minimum

Context. During solar minima the spatial power spectrum of the photospheric magnetic field is dominated by the low-degree zonal (axisymmetric; m = 0) harmonic components, reflecting the large polar coronal holes of unipolar magnetic field. However, measuring polar fields is difficult because of the unequal visibility of the two poles during most of the year and the small line-of-sight component of the roughly radial field at high solar latitudes. Aims. In this paper we derive the spatial power spectrum of the photospheric magnetic field in terms of the harmonic coefficients of the radial component (Br) as well as in terms of the harmonic coefficients of the internal potential (known as Gauss coefficients). We calculate the zonal spatial power spectrum using Mount Wilson Observatory synoptic maps from 1995–1996, during the solar minimum between solar cycles 22 and 23, and investigate how filling or not filling the polar data gaps affects the zonal harmonic coefficients. Methods. We eliminated the vantage point effect by removing the highest 5° of the measured magnetic field and calculating the latitudinal profile of the zonal median field over the two years, which ensured equal latitudinal data coverage of both solar hemispheres. We then derived the zonal harmonic coefficients using this latitudinal profile of Br. Results. We find that when the polar data gaps are left unfilled, a strong artificial power above l = 8 is produced. Only the first five zonal harmonic coefficients can be considered reliable in this case. Therefore polar filling is essential to obtain a realistic spatial power spectrum. Filling the polar gap with a constant (non-zero) value yields zonal harmonics that are reliable up to l = 9. We find that the zonal octupole component contributes most to the total spatial power, more than the zonal dipole, even during the solar minimum conditions. This difference is seen more clearly in the case of polar filling. We also prove that the asymmetry of the polar fields during this solar minimum is statistically significant. Conclusions. Our results emphasize the importance of filling the polar data gaps in order to obtain a correct estimate of the spatial power spectrum of the photospheric field. This helps in estimating the reliability of polar fields and the large-scale structure in synoptic maps of different origin. Our results also verify the asymmetric nature of the polar fields, which is important for the heliospheric magnetic field and for solar dynamo modeling.

A multi-module energy-saving pulsed magnetic field generator.

In order to generate the unipolar and bipolar pulsed magnetic fields and improve the energy efficiency of the magnetic field generator, a multi-module energy-saving (MMES) pulsed magnetic field generator is designed. The circuit topology of the MMES pulsed magnetic field generator is presented and the experimental data are measured by experiments. The results show that the peak current values of unipolar and bipolar pulsed magnetic fields are 156 A and 154 A by discharging two capacitors, and the intensities are 87.6 mT and 86.5 mT, respectively. The energy-saving rates of unipolar and bipolar pulsed magnetic fields can be up to 17.64% and 19.36%, respectively. Therefore, it has very high application and research value in the field of biological magnetism therapy.

Одно- и двухкубитные гейты: техника Раби и одиночные униполярные импульсы

In this paper we discuss methods for controlling the states of interacting superconducting flux qubits using energy-efficient devices of rapid single flux quantum logic (the resonators with Josephson nonlinearity). A comparative analysis for one - and two-qubit quantum logical operations performed both within the traditional control technique using Rabi pulses and using picosecond single unipolar magnetic field pulses is carried out. It is shown that by optimizing the shape and parameters of unipolar control pulses (associated, for example, with the propagation of fluxons in the transmission lines) it is possible to implement all the basic operations with the fidelity of more than 97 %. The efficiency of the developed technique was demonstrated for programming a two-bit quantum processor that implements the simplest Deutsch-Joza algorithm.

Three-phase Evolution of a Coronal Hole. II. The Magnetic Field

Abstract We investigate the magnetic characteristics of a persistent coronal hole (CH) extracted from EUV imagery using Heliospheric and Magnetic Imager filtergrams over the period 2012 February–October. The magnetic field, its distribution, and the magnetic fine structure in the form of flux tubes (FTs) are analyzed in different evolutionary states of the CH. We find a strong linear correlation between the magnetic properties (e.g., signed/unsigned magnetic field strength) and the area of the CH. As such, the evolutionary pattern in the magnetic field clearly follows a three-phase evolution (growing, maximum, and decaying) as found from EUV data (Part I). This evolutionary process is most likely driven by strong FTs with a mean magnetic field strength exceeding 50 G. During the maximum phase they entail up to 72% of the total signed magnetic flux of the CH, but only cover up to 3.9% of the total CH area, whereas during the growing and decaying phases, strong FTs entail 54%–60% of the signed magnetic flux and cover around 1%–2% of the CH’s total area. We conclude that small-scale structures of strong unipolar magnetic field are the fundamental building blocks of a CH and govern its evolution.

Underground current impulses as a possible source of unipolar magnetic pulses

Recently several cases of observations of unipolar magnetic field pulses associated with earthquakes at different points (California, Italy, Peru) have been recorded. The paper attempts to model unipolar magnetic field pulses based on one mechanism that should be omnipresent for all measurement points, namely, the magnetic field diffusion through a conductive medium. The structure of magnetic fields supported by electric current sources is thoroughly modelled. The source of electric current is considered as an elongated volume of finite cross-section being immersed in a conductive medium. To model the unipolarity feature of the observed pulses prior to and at the earthquake main shock, the electric current of the source is of impulse form. Special attention is paid to the differences in the pulse structure (as amplitude envelope and the pulse width) that are measured by various magnetometers (fluxgate or search-coil). An analysis and comparison with recorded magnetic field pulse characteristics reveal that the observed unipolar pulses may have a common genesis, an electric current source within a conductive medium such as the earth crust.

The Formation and Maintenance of the Dominant Southern Polar Crown Cavity of Cycle 24

Abstract In this article, we report a study of the longest-lived polar crown cavity of Solar Cycle 24, using an observation from 2013, and propose a physical mechanism to explain its sustained existence. We used high temporal and spatial resolution observations from the Atmospheric Imaging Assembly (AIA) and the Helioseismic Magnetic Imager (HMI) instruments on board the Solar Dynamics Observatory (SDO) to explore the structure and evolution of the cavity. Although it existed for more than a year, we examined the circumpolar cavity in great detail from 2013 March 21 to 2013 October 31. Our study reinforces the existing theory of formation of polar crown filaments that involves two basic processes to form any polar crown cavity as well as the long-lived cavity that we studied here. First, the underlying polarity inversion line (PIL) of the circumpolar cavity is formed between (1) the trailing part of dozens of decayed active regions distributed in different longitudes and (2) the unipolar magnetic field in the polar coronal hole. Second, the long life of the cavity is sustained by the continuing flux cancellation along the PIL. The flux is persistently transported toward the polar region through surface meridional flow and diffusion. The continuing flux cancellation leads to the shrinking of the polar coronal hole.

Effect of Unipolar Magnetic Field on Macroscopic Properties of Distilled Water

Effect of Unipolar Magnetic Field on Macroscopic Properties of Distilled Water

Coronal Hole and Solar Global Magnetic Field Evolution in 1976 – 2012

Coronal hole spatial-temporal evolution is studied and comparison made with that of the solar global magnetic field in cycles 21-23 (1976-2012). The latitude-longitude distribution dynamics of coronal holes and the regularities in the global magnetic field associated with the solar polar field reversal are analyzed. Polar and non-polar coronal hole populations are considered. The investigation reveals some temporal and spatial regularities in coronal hole distributions that match well the global magnetic-field cycle evolution. The results show that the non-polar coronal hole longitudinal distribution follows all configuration changes in the global magnetic-field structure. Reorganizations of the global magnetic-field and coronal hole distributions occur simultaneously during a time interval of a few solar rotations. The cycle evolution of the non-polar coronal holes reflects the transition of the solar global magnetic field from the zonal structure to sectorial andvice versa. Two different type waves of non-polar coronal holes are revealed from their latitudinal distribution. The first one is short poleward waves. They trace the poleward motion of the unipolar photospheric magnetic fields from approximately 35 deg to the associated pole in each hemisphere and the redevelopment of a new-polarity polar CH. Although they start the poleward movement before the change of the polar magnetic field in the associated hemisphere, they reach the pole after the polar reversal. The other type of non-polar CH wave forms two sinusoidal branches associated with the positive- and negative-polarity magnetic fields. The complete period of the wave was equal to approximately 268 CRs (22 years). These wave CHs arrive at high latitudes during declining phases when the new polarity polar CHs are already completely formed.