We examine magnetic field variations within the frequency range of several millihertz (Pc5-6/Pi3 geomagnetic pulsations) in the near-Earth magnetotail and adjacent flank magnetosheath regions, using data from Cluster satellites for 2016. Dependence of spectral coherence on interval length is analyzed for a satellite pair Cluster-1 and Cluster-4 at different satellite positions relative to the magnetopause. It is shown that absolute coherence and the rate of its decline with increasing time interval length differ for the longitudinal and transverse magnetic field components, as well as for different satellite positions. We also present a case study of a coherent pulsation recorded in the magnetosheath at low solar wind velocity and weak fluctuations in front of the bow shock.

The Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observing Station (HSOS) has conducted continuous observations of solar vector magnetic fields for nearly four decades, and while the primary optical system remains unchanged, critical components—including filters, polarizers, and detectors—have undergone multiple upgrades and replacements. Maintaining data consistency is essential for reliable long-term studies of magnetic field evolution and solar activity, as well as current helicity. In this study, we systematically analyze background bias and noise levels in SMFT observations from 1988 to 2019. Our dataset comprises 12,281 vector magnetograms of 1484 active regions. To quantify background bias, we computed mean values of Stokes Q/I, U/I and V/I over each entire magnetogram. The background bias of Stokes V/I is small for the whole dataset. The background biases of Stokes Q/I and U/I fluctuate around zero during 1988–2000. From 2001 to 2011, however, the fluctuations in the background bias of both Q/I and U/I become significantly larger, exhibiting mixed positive and negative values. Between 2012 and 2019, the background biases shift to predominantly positive values for both Stokes Q/I and U/I parameters. To address this issue, we propose a potential method for removing the background bias and further discuss its impact on the estimation of current helicity. For each magnetogram, we quantify measurement noise by calculating the standard deviation (σ) of the longitudinal (Bl) and transverse (Bt) magnetic field components within a quiet-Sun region. The noise levels for Bl and Bt components were approximately 15 Gauss (G) and 87 G, respectively, during 1988–2011. Since 2012, these values decreased significantly to ∼6 G for Bl and ∼55 G for Bt, likely due to the installation of a new filter.

Abstract The critical need to study the magnetic field in the solar corona is highlighted by recent observational facilities, such as the Daniel K. Inouye Solar Telescope and Aditya-L1. A powerful tool for probing the magnetism of the solar corona is forward modeling of the intensity and polarization of coronal emission lines in three-dimensional (3D) magnetohydrodynamic models. Here we present P-CORONA, a new spectral synthesis code designed to calculate the intensity and polarization of coronal lines in 3D models of the solar corona, taking into account the symmetry breaking induced by magnetic and velocity fields. P-CORONA allows the calculation of the on-disk and off-limb intensity and polarization of forbidden and permitted coronal lines, thus facilitating a wide range of investigations. Applying the quantum theory of atom–photon interactions, P-CORONA accounts for the spectral line polarization caused by anisotropic radiation pumping and the Hanle and Zeeman effects, making it a valuable tool for investigating coronal magnetic fields. This paper details the code’s theoretical formulation, implementation, and illustrative results of calculations in different 3D coronal models (MURaM and Predictive Science Inc.), including the impact of the Zeeman effect from the transverse magnetic field component on selected coronal forbidden lines. P-CORONA is now accessible to the research community on GitLab and Zenodo, providing a resource to facilitate research aimed at advancing our understanding of coronal magnetism and dynamics.

In the paper, we examine the spatial structure of eigenharmonics of the poloidal Alfvén resonator recorded by the RBSP-B satellite on 23 October 2012 at 19:12–20:24 UT. We employ the method of phase portraits, which is a set of plots of magnetic/electric field components of oscillations as well as the phase shift between transverse components, to interpret the data. Based on the theoretical description of magnetospheric MHD waves, an analytical solution for eigenharmonics of the poloidal Alfvén resonator is framed. The phase shift of individual harmonics of the observed oscillations is shown to have a quasi-periodic structure, which allows us to confirm that they have resonator modes, and the magnetic field components analytically calculated along the satellite trajectory qualitatively coincide with the satellite data. From comparison of theoretical calculations of the structure of transverse magnetic field components with observational data, we put forward an assumption that the second and fourth harmonics of the poloidal resonator make the main contribution to the observed oscillations.

In the paper, we examine the spatial structure of eigenharmonics of the poloidal Alfvén resonator recorded by the RBSP-B satellite on 23 October 2012 at 19:12–20:24 UT. We employ the method of phase portraits, which is a set of plots of magnetic/electric field components of oscillations as well as the phase shift between transverse components, to interpret the data. Based on the theoretical description of magnetospheric MHD waves, an analytical solution for eigenharmonics of the poloidal Alfvén resonator is framed. The phase shift of individual harmonics of the observed oscillations is shown to have a quasi-periodic structure, which allows us to confirm that they have resonator modes, and the magnetic field components analytically calculated along the satellite trajectory qualitatively coincide with the satellite data. From comparison of theoretical calculations of the structure of transverse magnetic field components with observational data, we put forward an assumption that the second and fourth harmonics of the poloidal resonator make the main contribution to the observed oscillations.

Abstract Solar magnetic field measurements mainly use the Zeeman effect, but this method has two problems, namely, low accuracy of the transverse magnetic field components and a 180° ambiguity. Multi-perspective observations can increase the measurement accuracy and resolve the ambiguity. This study investigates how combined observations from the Sun-Earth L5 point, Sun-Earth line, and solar polar-orbiting satellites improve the accuracy of the transverse solar magnetic field under different satellite positional configurations. A three-satellite model is developed using spherical trigonometry to establish coordinate relationships, and the error propagation formulas are applied to correct transverse field measurement errors. The magnetic field measurement error distribution of the Helioseismic and Magnetic Imager is analyzed, and the magnetograms from the three satellites are simulated. The improvement to the transverse field accuracy under various satellite configurations is then assessed based on simulation results. The results show that multi-perspective measurements can reduce transverse component errors ΔB x to approximately 10% and ΔB y to about 15% compared to the error from a single satellite. An optimally designed polar orbit can decrease the transverse field error by nearly an order of magnitude for 80% of its operation time.

This paper introduces an analytical method for studying power transmission through an infinite array of helical-shaped metal particles in a lossy dielectric medium. While the assessment of composite slabs’ transmitted power has been extensively researched in the electromagnetic interference (EMI) shielding field, many studies lack an adequate problem description. The primary inadequacy of these studies is the need for an analytical framework. This study, besides presenting a new approach to designing a concrete composite that leverages the magnetoelectric properties of the particles, making it suitable for EMI shielding, also employs a theoretical method to analyze the composite. A circuit model of the array is introduced using a modal field decomposition, which justifies the impact of helix transmission modes and the transverse magnetic field component on the shielding properties of the array. It is also shown that the resonances of the array can be tuned by engineering the helix properties. Furthermore, to broaden the applicable bandwidth of the composite, a multi-layer structure is proposed. The computational load of the proposed method demonstrates exceptional speed due to its circuit model foundation. The model yields valuable results compared to experimental measurement, making it ideal for optimizing various shielding composite structures for EMI shielding applications.

Isotope selective photoionization of 67 Z n is demonstrated with broadband excitation light (∼3.4G H z), temporally separated laser pulses in the presence of a weak external magnetic field. Starting with natural zinc metal (∼4% 67 Z n), the ion sample was enriched to ∼90% 67 Z n. Efficient suppression of the ionization of the even-mass isotopes was achieved by intermediate state alignment in the excitation scheme 4s 2 1 S 0→4s4p 3 P 1→4s4d 3 D 1, followed by nonresonant photoionization. The first excitation pulse was linearly polarized parallel to the transverse component of the external magnetic field and the linear polarization of the second excitation pulse was rotated to compensate for Larmor precession of the quantization axis during the temporal delay between the two excitations. This is the first systematic study, in the context of resonance ionization, investigating the independent and continuous rotation of the polarizations of the excitation pulses and demonstrating efficient compensation for the presence of an external magnetic field that has an arbitrary direction. Experimental results are supported by a vector model combined with rate equations.

Context. Alfvénic fluctuations, as modelled by the non-linear interactions of Alfvén waves of various scales, are seen to dominate solar wind turbulence. However, there is also a non-negligible component of non-Alfvénic fluctuations. The Elsässer formalism, which is central to the study of Alfvénic turbulence due to its ability to differentiate between parallel and anti-parallel Alfvén waves, cannot strictly separate wavemodes in the presence of compressive magnetoacoustic waves. In this study, we analyse the deviations generated in the Elsässer formalism as density fluctuations are naturally generated through the propagation of a linearly polarised Alfvén wave. The study was performed in the context of a coronal mass ejection (CME) propagating through the solar wind, which enables the creation of two solar wind regimes, pristine wind and a shocked CME sheath, where the Elsässer formalism can be evaluated. Aims. We studied the deviations of the Elsässer formalism in separating parallel and anti-parallel components of Alfvénic solar wind perturbations generated by small-amplitude density fluctuations. Subsequently, we evaluated how the deviations cause a misinterpretation of the composition of waves through the parameters of cross helicity and reflection coefficient. Methods. We used an ideal 2.5D magnetohydrodynamic model with an adiabatic equation of state. An Alfvén pump wave was injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components. This wave subsequently generates density fluctuations through the ponderomotive force. A CME was injected by inserting a flux-rope modelled as a magnetic island into the quasi-steady solar wind. Results. The presence of density perturbations creates a ≈10% deviation in the Elsässer variables and reflection coefficient for the Alfvén waves as well as a deviation of ≈0.1 in the cross helicity in regions containing both parallel and anti-parallel fluctuations.

Study on the microspot splitting characteristics of pulsed cathodic vacuum arc

The nonlinear evolution of Alfvén waves in the solar corona leads to the generation of Alfvénic turbulence. This description of the Alfvén waves involves parametric instabilities where the parent wave decays into slow mode waves giving rise to density fluctuations. These density fluctuations, in turn, play a crucial role in the modulation of the dynamic spectrum of type III radio bursts, which are observed at the fundamental of local plasma frequency and are sensitive to the local density. During observations of such radio bursts, fine structures are detected across different temporal ranges. In this study, we examine density fluctuations generated through the parametric decay instability (PDI) of Alfvén waves as a mechanism to generate striations in the dynamic spectrum of type III radio bursts using magnetohydrodynamic simulations of the solar corona. An Alfvén wave is injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components, which subsequently undergo the PDI instability. The type III burst is modeled as a fast-moving radiation source that samples the background solar wind as it propagates to emit radio waves. We find the simulated dynamic spectrum to contain striations directly affected by the multiscale density fluctuations in the wind.

ABSTRACT Measurements of transverse magnetic field and velocity components from Parker Solar Probe have revealed a coherent quasi-periodic pattern in the near-Sun solar wind. As well as being Alfvénic and arc-polarized, these deflections were characterized by a consistent orientation and an increased proton core temperature, which was greater parallel to the magnetic field. We show that switchbacks represent the largest deflections within this underlying structure, which is itself consistent with the expected outflow from interchange reconnection simulations. Additionally, the spatial scale of the deflections was estimated to be around 1 Mm on the Sun, comparable to the jetting activity observed at coronal bright points within the base of coronal plumes. Therefore, our results could represent the in situ signature of interchange reconnection from coronal bright points within plumes, complementing recent numerical and observational studies. We also found a consistent relationship between the proton core temperature and magnetic field angle across the Parker Solar Probe encounters and discussed how such a persistent signature could be more indicative of an in situ mechanism creating a local increase in temperature. In future, observations of minor ions, radio bursts, and remote sensing images could help further establish the connection between reconnection events on the Sun and signatures in the solar wind.

Context.Alfvénic fluctuations of various scales are ubiquitous in the corona; their non-linear interactions and eventual turbulent cascade result in an important heating mechanism that accelerates the solar wind. These fluctuations may be processed by large-scale, transient, and coherent heliospheric structures such as coronal mass ejections (CMEs). In this study we investigate the interactions between Alfvénic solar wind fluctuations and CMEs using magnetohydrodynamic (MHD) simulations.Aims.We study the transmission of upstream solar wind fluctuations into the CME leading to the formation of CME sheath fluctuations. Additionally, we investigate the influence of the fluctuation frequencies on the extent of the CME sheath.Methods.We used an ideal MHD model with an adiabatic equation of state. An Alfvén pump wave is injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components, and a CME is injected by inserting a flux-rope modelled as a magnetic island into the quasi-steady solar wind.Results.The upstream Alfvén waves experience a decrease in wavelength and change in the wave vector direction due to the non-radial topology of the CME shock front. The CME sheath inhibits the transmission of long-wavelength fluctuations due to the presence of non-radial flows in this region. The frequency of the solar wind fluctuations also affects the steepening of MHD fast waves causing the CME shock propagation speed to vary with the solar wind fluctuation frequencies.

Nonequilibrium dynamics is a paramount scenario for studying quantum systems. The emergence of new features with no equilibrium counterpart, such as dynamical quantum phase transition (DQPT), has attracted wide attention. In this paper, we depart from the well-known Ising model and showcase an experimentally accessible configuration of a negatively charged nitrogen-vacancy center that interacts with nearby carbon-13 nuclear spins. We provide insights into this system in the context of DQPT. We show that nuclear spins undergo DQPT by appropriately choosing the relation between the transverse and longitudinal components of an external magnetic field. Furthermore, we can steer the DQPT via a time-dependent longitudinal magnetic field and apply this control to enhance the estimation of the coupling strength between the nuclear spins. Moreover, we propose a quenched dynamics that originates from the rotation of the central electron spin, which controls the DQPT relying on the anisotropy of the hyperfine coupling.

Context. Alfvén-wave turbulence has emerged as an important heating mechanism to accelerate the solar wind. The generation of this turbulent heating is dependent on the presence and subsequent interaction of counter-propagating Alfvén waves. This requires us to understand the propagation and evolution of Alfvén waves in the solar wind in order to develop an understanding of the relationship between turbulent heating and solar-wind parameters. Aims. We aim to study the response of the solar wind upon injecting monochromatic single-frequency Alfvén waves at the base of the corona for various magnetic flux-tube geometries. Methods. We used an ideal magnetohydrodynamic model using an adiabatic equation of state. An Alfvén pump wave was injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components. Results. Alfvén waves were found to be reflected due to the development of the parametric decay instability (PDI). Further investigation revealed that the PDI was suppressed both by efficient reflections at low frequencies as well as magnetic flux-tube geometries.

In principle, high-temperature superconducting (HTS) flux-pinning maglev has the advantage of self-stable levitation and is therefore a good development prospect as a new rail transit technology. The magnetic field intensity is one of the key factors affecting the levitation performance of single-grain bulk superconductors in the HTS maglev system. To date, however, most researchers have focused on the levitation performance of HTS bulk superconductors in magnetic fields within a permanent magnet guideway (PMG) configuration. The magnitude of the external working magnetic field provided by a PMG is limited to about 0.5 T at 77 K, given that the superconductor usually levitates at a typical working height of 10 mm above the PMG. Therefore, the weak magnetic fields generated by the PMG significantly limits the levitation performance of HTS maglev systems to that of the permanent magnet (PM). In this article, a superconducting magnet test bench was utilized to provide a 0–3 T external magnetic field (B) environment for the study of the levitation force in HTS single grains. The difference in levitation performance between YBaCuO (YBCO) and GdBaCuO-Ag (GdBCO-Ag) bulk superconductors under large, changing magnetic fields was studied systematically. The relationships between levitation force and magnetic field characteristics, including vertical magnetic field component (Bz), transverse magnetic field component (Br), and vertical magnetic field variation (ΔBz) were investigated. The result of variation curves about YBCO and GdBCO bulks' levitation forces under different ΔBz shows that the levitation force of the bulk, single-grain superconductors will reach saturation under a varying ΔBz environment (0.72 and 1.5 T). The values of ΔBz corresponding to the saturation positions are found to be independent of the sizes of the HTS samples. At the same time, GdBCO-Ag exhibits a levitation force that is 112.8% greater than YBCO in B = 3 T magnetic environment. As a result, it is demonstrated that the levitation potential of single-grain HTS bulks can be better exploited by optimizing the distribution of the magnetic field.

Vacuum switches have been extensively used in the field of medium voltage. Carrying out relevant research on vacuum arc is particularly important for improving the performance and reliability of vacuum switches. The vacuum arc cathode spots provide metal vapor and electrons, which determine the breaking capacity of the vacuum switches to some extent. Therefore, based on the simulation model of the cathode spots between the transverse magnetic field (TMF) contacts, the motion phenomenon and distribution of the cathode spot were simulated and the characteristics of the initial diffusion stage of cathode spots between TMF contacts were studied. The simulation results showed that the probability of generating a cathode spot in the direction of retrograde motion increased with the increase in the TMF component and the direction of motion varied with the angle between the magnetic field and the contact. The diffusion process of cathode spots under wan-shaped contacts, cup-shaped contacts, and spiral-shaped contacts was simulated. The ring-shaped distribution of the cathode spots between cup-shaped contacts with a large current in the initial diffusion stage was formed by the self-generated magnetic field of cathode spots, while the axial magnetic field component and the clustered cathode spots destroyed the ring-shaped distribution. Taking the distribution of cathode spots and current from experiments as initial conditions, the simulation results of cathode spot distribution in the initial diffusion stage and the arc root radius were consistent with the experimental results.

Full disk vector magnetic fields are used widely for developing better understanding of large-scale structure, morphology, and patterns of the solar magnetic field. The data are also important for modeling various solar phenomena. However, observations of vector magnetic fields have one important limitation that may affect the determination of the true magnetic field orientation. This limitation stems from our ability to interpret the differing character of the Zeeman polarization signals which arise from the photospheric line-of-sight vs. the transverse components of the solar vector magnetic field, and is likely exacerbated by unresolved structure (non-unity fill fraction) as well as the disambiguation of the 180° degeneracy in the transverse-field azimuth. Here we provide a description of this phenomenon, and discuss issues, which require additional investigation.

In this paper, we search for the relationship between the Vlin linear projection velocity and the Vss velocity in the 3D space of coronal mass ejections (CMEs) recorded by LASCO coronagraphs with an “n” decay rate of the transverse component of the Bt magnetic field above the polarity inversion line (PIL) of the photospheric magnetic field in the active region (AR) in which the CME appeared. The Bt decay rate at an altitude h measured from the photosphere was calculated with the formula n(h) = –(h/Bt)(dBt/dh). Three-dimensional calculations of the magnetic field were performed in the potential approximation. The positive trend of the dependences 〈n〉(Vlin) and 〈n〉(Vss), however, does not have sufficient statistical significance: on average, the larger is 〈n〉, the higher are the determined Vlin and Vss CME velocities. Here, 〈n〉 includes the averaging of n over both the altitude and along the extended section of the PIL identified within each studied AR. The relationship between the quality of 〈n〉(Vlin) and 〈n〉(Vss) is shown to depend on the PIL section in the AR within which n is averaged. Based on the example of a fast CME on March 7, 2012, and a slow CME on October 22, 2013, it is shown that the difference in 〈n〉 for CMEs with different velocities is greater if the averaging of n along the PIL is performed within the CME initiation region, not along the entire extended PIL section in the AR.

The drawn vacuum arc begins with a bridge column formed from the explosion of a liquid metal bridge after separating the contacts. The expansion process of the initial arc has an effect on arc motion or diffusion. In order to deeply study the influence of transverse magnetic field (TMF) and axial magnetic field (AMF) on the drawn arc characteristics in the initial expansion stage, in this article, arc ignition mode and appearance under two groups of contacts with different AMF and TMF components were experimentally studied. It was found that simultaneously reducing TMF and AMF components would end the expansion stage earlier, and the fluctuation of the arc column pressure during the expansion was larger. When TMF and AMF components were further reduced, the arc needs to take a longer time to extend across the slot gap due to insufficient Ampere force. When TMF was basically unchanged and AMF was reduced, the arc burned more intense, the diameter of the arc column was smaller, and the arc would merge earlier in multipoint ignition mode. The characteristics of arc voltage, pressure, and duration of expansion stage were analyzed, founding that the arc with a moderate TMF and AMF components had a smaller rising slope of arc voltage, a faster reducing speed of arc pressure, and a smaller range of the duration of expansion stage. In addition, the variation of magnetic field strength in different ignition modes and contact structures during the arc expansion stage was simulated to explain the mechanism of arc behavior.