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In the previous numerical study, we find the blob formation and ejection in the presence of magnetic reconnection in the environment of the hot flow of the accretion disc. Based on those encouraging results, in the present work, we calculate the energy and the spectrum of the emission in the different bands around sagittarius A* (Sgr A*). We assume the electrons in the magnetic reconnection region are non-thermal and emit synchrotron radiation. The electrons in the other region are thermal, which follows the thermal distribution, and the thermal electron emission mechanism is thermal synchrotron radiation. During the whole process of the magnetic evolution and reconnection, we find two peaks in the temporal light curve in the recently observed radio frequencies (230 and 43 GHz) and near-infrared (NIR) wavelengths (3.8 and 2.2 μm). Although the light curve of the NIR band is most prominent in a single peak. The first peak appears because of the blob in the plasma flow, which is formed due to the magnetic reconnection. The second peak appears due to the production of the non-thermal electrons with the evolution of the magnetic flux. Both peaks reach luminosity of more than 1026 erg s−1 for a single plasmoid/blob. For the NIR band, the highest luminosity can reach more than 1028 erg s−1. These luminosities can be high for the large simulation area and the stronger magnetic field with the multiple blobs. We infer that the observed flares are a group of magnetic reconnection phenomena, not a single one.

A microwave beam (wavelength 4 mm, power 150–300 kW) generates an ionization wave in air in the subthreshold field in the shape of a conglomerate of thread-like channels that moves toward the beam. The periphery of the beam refracts in the plasma of the non-self-sustained discharge in the UV halo of the thread-like discharges and self-focuses in the recombining plasma behind the front of the plasmoid that consists of thread-like channels. The self-focusing of the peripheral regions of the wave beam causes local bursts of ionization behind the front of the leading plasmoid.

Relativistic jets and disc-winds are typically observed in BH-XRBs and AGNs. However, many physical details of jet launching and the driving of disc winds from the underlying accretion disc are still not fully understood. In this study, we further investigate the role of the magnetic field strength and structure in launching jets and disc winds. In particular, we explore the connection between jet, wind, and the accretion disc around the central black hole. We perform axisymmetric GRMHD simulations of the accretion-ejection system using adaptive mesh refinement. Essentially, our simulations are initiated with a thin accretion disc in equilibrium. An extensive parametric study by choosing different combinations of magnetic field strength and initial magnetic field inclination is also performed. Our study finds relativistic jets driven by the Blandford \& Znajek (BZ) mechanism and the disc-wind driven by the Blandford \& Payne (BP) mechanism. We also find that plasmoids are formed due to the reconnection events, and these plasmoids advect with disc-winds. As a result, the tension force due to the poloidal magnetic field is enhanced in the inner part of the accretion disc, resulting in disc truncation and oscillation. These oscillations result in flaring activities in the jet mass flow rates. We find simulation runs with a lower value of the plasma-$��$, and lower inclination angle parameters are more prone to the formation of plasmoids and subsequent inner disc oscillations. Our models provide a possible template to understand spectral state transition phenomena in BH-XRBs., 21 pages, 20 figures, accepted for publication in MNRAS

The ultraviolet emission from the solar transition region is dominated by dynamic, low-lying magnetic loops. The enhanced spatial and temporal resolution of the solar observation satellite Interface Region Imaging Spectrograph (IRIS) has made it possible to study these structures in fine detail. IRIS has observed ‘transient brightenings’ in these loops, associated with strong excess line broadenings1,2 providing important clues to the mechanisms that heat the solar atmosphere. However, the physical origin of the brightenings is debated. The line broadenings have been variously interpreted as signatures of nanoflares3, magneto-hydrodynamic turbulence4, plasmoid instabilities5 and magneto-acoustic shocks6. Here we use IRIS slit-jaw images and spectral data, and the Atmospheric Imaging Assembly of the Solar Dynamics Observatory spacecraft, to show that the brightenings are consistent with magnetic-reconnection-mediated impulsive heating at field-line braiding sites in multi-stranded transition-region loops. The spectroscopic observations present evidence for preferential heating of heavy ions from the transition region and we show that this is consistent with ion cyclotron turbulence caused by strong currents at the reconnection sites. Time-dependent differential emission measure distributions are used to determine the heating frequency7–9 and to identify pockets of faintly emitting ‘super-hot’ plasma. The observations we present and the techniques we demonstrate open up a new avenue of diagnostics for reconnection-mediated energy release in solar plasma. Solar imaging and spectral data indicate that impulsive heating through magnetic reconnection in transition region loops is responsible for observed transient brightenings, consistent with ion cyclotron turbulence due to strong currents at the reconnection sites.

Formation of an elongated Sweet-Parker current sheet and a transition to plasmoid instability has for the first time been predicted by simulations in a large-scale toroidal fusion plasma in the absence of any pre-existing instability. Plasmoid instability is demonstrated through resistive MHD simulations of transient Coaxial Helicity Injection (CHI) experiments in the National Spherical Torus Experiment (NSTX).Consistent with the theory, fundamental characteristics of the plasmoid instability, including fast reconnection rate, have been observed in these realistic simulations. Motivated by the simulations, experimental camera images have been revisited and suggest the existence of reconnecting plasmoids in NSTX. Global, system-size plasmoid formation observed here should also have strong implications for astrophysical reconnection, such as rapid eruptive solar events., 5 pages, 5 figures

The partial eruption of a filament channel with bifurcated substructures is investigated using datasets obtained from both ground-based and space-borne facilities. Small-scale flux reconnection/cancellation events in the region triggered the pile-up of ambient magnetic field, observed as bright EUV loops in close proximity of the filament channel. This led to the formation of a V-shaped cusp structure at the site of interaction between the coalesced EUV loops and the filament channel, with the presence of distinct plasmoid structures and associated bidirectional flows. Analysis of imaging data from SDO/AIA further suggests the vertical split of the filament structure into two substructures. The perturbed upper branch of the filament structure rose up and erupted with the onset of an energetic GOES M1.4 flare at 04:30 UT on January 28, 2015. The estimated twist number and squashing factor obtained from nonlinear force free-field extrapolation of the magnetic field data support the vertical split in filament structure with high twist in upper substructure. The loss in equilibrium of the upper branch due to torus instability, implying this as a potential triggering mechanism of the observed partial eruption., Comment: Accepted for Publication in MNRAS

We present the results of 2D particle-in-cell (PIC) simulations of relativistic magnetic reconnection (RMR) in electron-positron plasma, including the dynamical influence of the synchrotron radiation process, and integrating the observable emission signatures. The simulations are initiated with a single Harris current layer with a central gap that triggers the RMR process. We achieve a steady-state reconnection with unrestricted outflows by means of open boundary conditions. The radiative cooling efficiency is regulated by the choice of initial plasma temperature Theta. We explore different values of Theta and of the background magnetisation sigma_0. Throughout the simulations, plasmoids are generated in the central region of the layer, and they evolve at different rates, achieving a wide range of sizes. The gaps between plasmoids are filled by smooth relativistic outflows called minijets, whose contribution to the observed radiation is very limited due to their low particle densities. Small-sized plasmoids are rapidly accelerated, however, they have lower contributions to the observed emission, despite stronger relativistic beaming. Large-sized plasmoids are slow, but produce most of the observed synchrotron emission, with major part of their radiation produced within the central cores, the density of which is enhanced by radiative cooling. Synchrotron lightcurves show rapid bright flares that can be identified as originating from mergers between small/fast plasmoids and large/slow targets moving in the same direction. In the high-magnetisation case, the accelerated particles form a broken power-law energy distribution with a soft tail produced by particles accelerated in the minijets., Comment: 17 pages, 15 images, Accepted for publication in MNRAS

We performed high-resolution three-dimensional global magnetohydrodynamic (MHD) simulations to study the interaction between the Earth’s magnetosphere and a prolonged steady southward interplanetary magnetic field (IMF) (Bz = –2nT) and slow solar wind. The simulation results show that dayside magnetic reconnection continuously occurs at the subsolar region where the magnetosheath magnetic field is antiparallel to the geomagnetic field. The plasmoid developed on closed plasma sheet field lines. We found that the vortex was generated at the magnetic equator such as (X, Y) = (7.6, 8.9) RE due to the viscous-like interaction, which was strengthened by dayside reconnection. The magnetic field and plasma properties clearly showed quasiperiodic variations with a period of 8–10 min across the vortex. Additionally, double twin parallel vorticity in the polar region was clearly seen. The peak value of the cross-polar cap potential fluctuated between 17 and 20 kV during the tail reconnection.

Fast radio bursts (FRBs) are bright, short-duration radio transients with very high brightness temperatures implying highly coherent emission. We suggest that the FRBs are caused by the self-focusing of an electron beam interacting with an ambient plasma right beyond the light cylinder radius of a neutron star. The magnetic field at the light cylinder radius is relatively high which can accommodate both young Crab-like systems and old millisecond pulsars addressing the diverse environments of FRBs. At the first stage, the intense pulsed-beam passing through the background plasma causes instabilities such that the trapped particles in local Buneman-type cavitons saturate the local field. The beam is then radially self-focused due to the circular electric field developed by the two-stream instability which leads to Weibel instability in the transverse direction. Finally, the non-linear saturation of the Weibel instability results in the self-modulational formation of solitons due to plasmoid instability. The resonant solitary waves are the breather-type solitons hosting relativistic particles with self-excited oscillations. The analytical solutions obtained for non-linear dispersion and solitons suggest that, near the current sheets, the relativistic bunches are accelerated/amplified by klystron-like structures due to self-excited oscillations by the induced local electric field. Boosted coherent radio emission propagates through a narrow cone with strong focusing due to radial electric field and magnetic pinching. The non-linear evolution of solitons and the stimulated emission are associated with the Buneman instability and the possibility of the presence of nanosecond shots in FRBs are investigated., Comment: MNRAS accepted

The results of experimental investigations of an electric discharge in an aqueous medium are presented. In the experiment, the formation of luminous balls, which sometimes exploded, is observed in the atmosphere. Spectroscopic investigations show the presence of an increased content of atomic hydrogen in the plasma, which confirms the assumption that the balls formed could be diffusely burning hydrogen clumps. The results obtained suggest that bead lightning is similar to diffusely burning hydrogen formations.

The necessity of monitoring the state of the environment is justified. Various methods of environmental monitoring were analyzed. The radar method for monitoring radioactive contamination in the atmosphere was considered in detail. The monitoring data using radar stations were processed and analyzed. The efficiency of this method was estimated. Recommendations were proposed to expand the monitoring capabilities using radars to assess the environmental situation., Обоснована необходимость контроля за состоянием окружающей среды. Проанализированы различные методы экологического мониторинга. Подробно рассмотрен радиолокационный метод для мониторинга радиоактивных загрязнений в атмосфере. Обработаны и проанализированы данные мониторинга с использованием радиолокационных станций. Оценена эффективность данного метода. Предложены рекомендации для расширения возможностей мониторинга с использованием радиолокационных станций для оценки экологической ситуации.

We have shown that diamagnetic structures (DSs), which form the basis of the slow quasi-stationary solar wind (SW), are observed in Earth’s orbit as a sequence of DSs of various scales. The analysis of this phenomenon indicates that diamagnetic plasmoids in SW, whose concept was introduced by Karlsson in 2015, are identical to small-scale DSs. We have found that the impact of a sequence of DSs in the slow SW on Earth’s magnetosphere causes an increase in geomagnetic activity. Isolated DSs generate short-term magnetic disturbances whose duration is approximately equal to the DS duration. Hence, a sequence of DSs can cause sawtooth substorms. We emphasize that the interaction of DS in the slow SW under northward interplanetary magnetic field can be associated with penetration of DS high-density plasma into the magnetosphere.

By using 2.5-dimensional resistive MHD simulations, dynamics of the plasmoid instability in a Harris current sheet has been studied with taking into account two main controlling parameters: the plasma-β in the range (0 < β < 1) and the amplitude ratio of magnetic guide field to the reconnection plane field in three different cases with zero, uniform, and non-uniform guide field. Varying the plasma-β changes the plasma compressibility which affects significantly on the linear and nonlinear growth rates of the plasmoid instability. For each of three cases, some associated scaling relations between the instability growth rate, the plasma-β and the magnitude of guide field are obtained.

The evolution of current sheets in accretion flows undergoing magnetorotational instability (MRI) is examined through two and three dimensional numerical modelling of the resistive MHD equations in global cylindrical geometry. With an initial uniform magnetic field aligned in the vertical ($z$) direction, MRI produces radially extended toroidal (azimuthal) current sheets. In both 2D and 3D when axisymmetric modes dominate, these current sheets attract each other and merge in the poloidal ($rz$) plane, driving magnetic reconnection when the Lundquist number $S > 3 \times 10^2$, making it a possible source of plasmoids (closed magnetic loops) in accretion disks. At high Lundquist numbers in the 2D regime, starting at $S = 5 \times 10^3$, self-consistent MRI-generated current sheets become thin and subject to plasmoid instability, and therefore spontaneous magnetic reconnection. When non-axisymmetric 3D modes dominate, turbulence makes the azimuthal current sheets further unstable, and stretch vertically. Toroidally extended vertical current sheets in the inner region, as well as larger 3D magnetic islands in the outer regions of the disks are also formed. These findings have strong ramifications for astrophysical disks as potential sources of plasmoids that could cause local heating, particle acceleration, and high energy EM radiation., 12 pages, 6 figures, Accepted for publication to ApJ Letters

The effect of a parallel velocity shear on the explosive phase of a double current sheet system is investigated within the 2D resistive magnetohydrodynamic (MHD) framework. We further explore the effect of this shear on acceleration of test particles. The general evolution pattern of the double current sheets is similar for all sub-Alfv\'enic shears with respect to the initial transient phase, the onset of the plasmoid instability and the final relaxation phase. We find that the theoretical scaling of the reconnection rate with shear holds if the rate is measured when the islands have a similar size. The larger island widths for lower shears greatly enhance the reconnection rate during the explosive phase. We have further examined the modification of the energy spectrum of the accelerated particles in the presence of a shear. Our results also show that the flow only modifies the high energy tail of the particle spectrum and has negligible effect on the power-law index. Individual particle trajectories help to explore the various mechanisms associated with the acceleration. Based on the location of the particles, the acceleration mechanisms are found to vary. We highlight the importance of the convective electric field in the inflow as well as the outflow region inside large magnetic islands in the acceleration of particles. The interaction and reflection of the particles with the reconnection exhausts inside the large scale primary magnetic islands is found to have a significant effect on the energization of the particles., Comment: 22 Pages, 14 Figures; The following article has been accepted by Physics of Plasmas (PoP). After it is published, it will be found at https://aip.scitation.org/journal/php

The physical mechanism for the production of fast gamma-ray variability in blazars remains debated. Plasmoids – magnetized quasi-circular structures of plasma formed self-consistently in reconnecting current sheets – are ideal candidates for the production of broadband variable non-thermal emission. Using state-of-the-art kinetic simulations of magnetic reconnection and radiative transfer calculations, we generate artificial gamma-ray light curves that would be observed with the Fermi Large Area Telescope (LAT). Our goal is to investigate if characteristic features of the theoretical light curves, such as the ultra-rapid gamma-ray flares predicted by the reconnection model, are detectable with the typical Fermi-LAT observations. A comparison with observed luminous and fast gamma-ray flares from flat spectrum radio quasars (FSRQs) reveals that magnetic reconnection events lead to comparable flux levels and variability patterns, especially when the reconnection layer is slightly misaligned with the line of sight. Emission from fast plasmoids moving close to the line of sight could explain fast variability on the time scales of minutes for which evidence has been found in observations of FSRQs. Our results motivate improvements in the existing reconnection model for blazars as well as dedicated searches for fast variability in LAT data as evidence for magnetic reconnection events.

We perform two-dimensional particle-in-cell simulations of reconnection in magnetically dominated electron-positron plasmas subject to strong Compton cooling. We vary the magnetization $\sigma\gg1$, defined as the ratio of magnetic tension to plasma inertia, and the strength of cooling losses. Magnetic reconnection under such conditions can operate in magnetically dominated coronae around accreting black holes, which produce hard X-rays through Comptonization of seed soft photons. We find that the particle energy spectrum is dominated by a peak at mildly relativistic energies, which results from bulk motions of cooled plasmoids. The peak has a quasi-Maxwellian shape with an effective temperature of $\sim 100$ keV, which depends only weakly on the flow magnetization and the strength of radiative cooling. The mean bulk energy of the reconnected plasma is roughly independent of $\sigma$, whereas the variance is larger for higher magnetizations. The spectra also display a high-energy tail, which receives $\sim 25$% of the dissipated reconnection power for $\sigma=10$ and $\sim 40$% for $\sigma=40$. We complement our particle-in-cell studies with a Monte-Carlo simulation of the transfer of seed soft photons through the reconnection layer, and find the escaping X-ray spectrum. The simulation demonstrates that Comptonization is dominated by the bulk motions in the chain of Compton-cooled plasmoids and, for $\sigma\sim 10$, yields a spectrum consistent with the typical hard state of accreting black holes., Comment: Accepted for publication in MNRAS. 17 pages, 11 figures, 4 appendices, 1 table

We perform force-free simulations for a neutron star orbiting a black hole, aiming at clarifying the main magnetosphere properties of such binaries towards their innermost stable circular orbits. Several configurations are explored, varying the orbital separation, the individual spins and misalignment angle among the magnetic and orbital axes. We find significant electromagnetic luminosities, $L\sim 10^{42-46} \, [B_{\rm pole}/ 10^{12}{\rm G}]^2 \, {\rm erg/s}$ (depending on the specific setting), primarily powered by the orbital kinetic energy, being about one order of magnitude higher than those expected from unipolar induction. The systems typically develop current sheets that extend to long distances following a spiral arm structure. The intense curvature of the black hole produces extreme bending on a particular set of magnetic field lines as it moves along the orbit, leading to magnetic reconnections in the vicinity of the horizon. For the most symmetric scenario (aligned cases), these reconnection events can release large-scale plasmoids that carry the majority of the Poynting fluxes. On the other hand, for misaligned cases, a larger fraction of the luminosity is instead carried outwards by large-amplitude Alfv{\'e}n waves disturbances. We estimate possible precursor electromagnetic emissions based on our numerical solutions, finding radio signals as the most promising candidates to be detectable within distances of $\lesssim 200$\,Mpc by forthcoming facilities like the Square Kilometer Array., Comment: 16 pages, 13 figures

Jupiter has a strong magnetic field, and a huge magnetosphere is formed through the solar wind-Jupiter interaction. The generated magnetosphere–ionosphere system is reproduced based on the 9-component Magnetohydrodynamics (MHD) and the current conservation in the ionosphere. Assuming Io plasma emission rate 1.4 t/sec, this paper reproduces self-consistently global magnetic configuration, generations of the field-aligned current (FAC) and aurora, formation of the Io plasma disk at 8–20 RJ, plasma corotation, instability in the plasma disk, transition from the Io plasma disk to the plasma sheet at 20–150 RJ, and the plasmoid ejection. The rotating Io plasma in the disk forms instabilities that promotes radial diffusion. H+ is supplied from the ionosphere along high-latitude magnetic field lines and mixed with heavy ions around 15–20 RJ. Beyond 20 RJ, mixed plasma diffuses further outward by the centrifugal force that can exceed magnetic tension. In the ionosphere, the main oval occurs at 13.7°–15.5° colatitude. The Io disk is inner side of magnetic field lines traced from the low-latitude edge of the main oval. Along magnetic field lines, the main oval is mapped from the outer edge of the Io disk to the entire plasma sheet accompanying rotation delay. Due to the corotation limit, convection is accompanied by plasmoid ejection. Back reaction of plasmoid ejection affects even transport process in the Io disk. The downward FAC occurs in the polar cap showing variability. The region of externally driven Dungey convection seems quite narrow.

A magnetosphere controls a planet's evolution by suppressing or enhancing atmospheric loss to space. In situ measurements of Uranus' magnetosphere from the Voyager 2 flyby in 1986 provide the only direct evidence of magnetospheric transport processes responsible for this atmospheric escape at Uranus. Analysis of high‐resolution Voyager 2 magnetic field data in Uranus' magnetotail reveals the presence of a loop‐like plasmoid filled with planetary plasma traveling away from the planet. This first plasmoid observation in an Ice Giant magnetosphere elucidates that (1) both internal and external forces play a role in Uranus' magnetospheric dynamics, (2) magnetic reconnection contributes to the circulation of plasma and magnetic flux at Uranus, and (3) plasmoids may be a dominant transport mechanism for mass loss through Uranus' magnetotail.

A periodic discharge in a liquid flow is an effective tool for modifying the surfaces of metal articles, which is aimed at increasing their durability, hardness, and corrosion resistance. Analysis of the discharge properties for determining limiting potentialities of this method and for optimizing technological regimes has revealed several formerly unknown physical phenomena. These factors must be considered for determining safety measures in implementation of industrial technologies. A new element in analysis is the inclusion of anomalous manifestations like bulbs, tracks, and filaments detected in ambient medium.

An electrodynamic model of ball lightning is proposed, according to which it is considered as a collection of plasmoids, consisting of electrons and protons, which rotate in closed orbits. Protons are retained in the orbit due to Coulomb attraction to the electron ring, while electrons are drifting in the crossed electric and the magnetic field, generated by the protons’ motion. This system has a non-compensated positive electric charge. These plasmoids placed inside a water shell serve to isolate a vacuum cavity from the atmosphere and to create a force, preventing expansion of proton rings. A mechanism of ball lightning creating near a loop of linear lightning channel is discussed. Ultraviolet radiation of the lightning discharge ionizes air, and due to the action of radio-frequency radiation with a non-uniform spatial distribution of intensity, a vacuum cavity is formed. The action on the plasma exerted by the crossed magnetic and eddy electric fields leads to separation and acceleration of charges. Losing a part of electrons, the system acquires a positive charge. Due to motion of water drops in the non-uniform field of this charge a dielectric shell around the ensemble of plasmoids is formed. A scheme of setup for ball lightning creation in laboratory is proposed.

Many rotating stars have magnetic fields that interact with the winds they produce. The Sun is no exception. The interaction between the Sun’s magnetic field and the solar wind gives rise to the heliospheric magnetic field—a spiralling magnetic structure, known as the Parker spiral, which pervades the Solar System. This magnetic field is critical for governing plasma processes that source the solar wind. Here, we report the creation of a laboratory model of the Parker spiral system based on a rapidly rotating plasma magnetosphere and the measurement of its global structure and dynamic behaviour. This laboratory system exhibits regions where the plasma flows evolve in a similar manner to many magnetized stellar winds. We observe the advection of the magnetic field into an Archimedean spiral and the ejection of quasi-periodic plasma blobs into the stellar outflow, which mimics the observed plasmoids that fuel the slow solar wind. This process involves magnetic reconnection and can be modelled numerically by the inclusion of two-fluid effects in the simulation. The Parker spiral system mimicked in the laboratory can be used for studying solar wind dynamics in a complementary fashion to conventional space missions such as NASA’s Parker Solar Probe mission. The Parker spiral—arising from the interaction between the Sun’s magnetic field with the solar wind—is recreated in the laboratory from a rapidly rotating plasma magnetosphere.

Kinetic effects of the dynamics of protons in plasmoids with a non-zero longitudinal (By) magnetic field component in a current sheet (CS) of a geomagnetic tail are considered. The results of modeling proton dynamics and a description of the mechanism of emergence of “north-south” density asymmetry are presented. The mechanism that is possibly responsible for maintaining the longitudinal magnetic field component is described. The obtained parameters are evaluated and the results are compared with observations of the Cluster mission.