Artigos de revistas: "Plasmoidi"

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Honkonen, I., M. Palmroth, T. I. Pulkkinen, P. Janhunen e A. Aikio. "On large plasmoid formation in a global magnetohydrodynamic simulation". Annales Geophysicae 29, n.º 1 (14 de janeiro de 2011): 167–79. http://dx.doi.org/10.5194/angeo-29-167-2011.

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Abstract. We investigate plasmoid formation in the magnetotail using the global magnetohydrodynamic (MHD) simulation GUMICS-4. Here a plasmoid implies a major reconfiguration of the magnetotail where a part of the tail plasma sheet is ejected downstream, in contrast to small Earthward-propagating plasmoids. We define a plasmoid based solely on the structure of the closed (connected to the Earth at both ends) magnetic field line region. In this definition a plasmoid is partly separated from the ordinary closed field line region by lobe field lines or interplanetary field lines resulting from lobe reconnection. We simulate an event that occurred on 18 February 2004 during which four intensifications of the auroral electroject (AE) index occurred in 8 h. Plasmoids form in the simulation for two of the four AE intensifications. Each plasmoid forms as a result of two consecutive large and fast rotations of the interplanetary magnetic field (IMF). In both cases the IMF rotates 180 degrees at 10 degrees per minute, first from southward to northward and some 15 min later from northward to southward. The other two AE intencifications however are not associated with a plasmoid formation. A plasmoid does not form if either the IMF rotation speed or the angular change of the rotation are small. We also present an operational definition for these fully connected plasmoids that enables their automatic detection in simulations. Finally, we show mappings of the plasmoid footpoints in the ionosphere, where they perturb the polar cap boundary in both hemispheres.

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Suzuki, Y., T. H. Watanabe, A. Kageyama, T. Sato e T. Hayashi. "Three-Dimensional Simulation Study of Plasmoid Injection into Magnetized Plasma". Symposium - International Astronomical Union 188 (1998): 209–10. http://dx.doi.org/10.1017/s0074180900114780.

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Resent observations suggest that, during solar flares, plasmoids are injected into the interplanetary medium (Stewart et al., 1982). It has also been pointed out that solar wind irregularities modeled as plasmoids are penetrated into the magnetosphere (Lemaire, 1977). These plasmoid injections are considered to be an important process because they transfer mass, momentum, and energy into such magnetized plasma regions. Our objective is to investigate the dynamics of a plasmoid, which is injected into a magnetized plasma region and to reveal mechanisms to transfer them. To achieve this, we carried out three-dimensional magnetohydrodynamic (MHD) simulations.

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Christie, I. M., M. Petropoulou, L. Sironi e D. Giannios. "Interplasmoid Compton scattering and the Compton dominance of BL Lacs". Monthly Notices of the Royal Astronomical Society 492, n.º 1 (9 de dezembro de 2019): 549–55. http://dx.doi.org/10.1093/mnras/stz3265.

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ABSTRACT Blazar emission models based on magnetic reconnection succeed in reproducing many observed spectral and temporal features, including the short-duration luminous flaring events. Plasmoids, a self-consistent by-product of the tearing instability in the reconnection layer, can be the main source of blazar emission. Kinetic simulations of relativistic reconnection have demonstrated that plasmoids are characterized by rough energy equipartition between their radiating particles and magnetic fields. This is the main reason behind the apparent shortcoming of plasmoid-dominated emission models to explain the observed Compton ratios of BL Lac objects. Here, we demonstrate that the radiative interactions among plasmoids, which have been neglected so far, can assist in alleviating this contradiction. We show that photons emitted by large, slow-moving plasmoids can be a potentially important source of soft photons to be then upscattered, via inverse Compton, by small fast-moving, neighbouring plasmoids. This interplasmoid Compton scattering process can naturally occur throughout the reconnection layer, imprinting itself as an increase in the observed Compton ratios from those short and luminous plasmoid-powered flares within BL Lac sources, while maintaining energy equipartition between radiating particles and magnetic fields.

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Lemaire, J. "Plasmoid motion across a tangential discontinuity (with application to the magnetopause)". Journal of Plasma Physics 33, n.º 3 (junho de 1985): 425–36. http://dx.doi.org/10.1017/s0022377800002592.

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The motion of a plasmoid (plasma-field entity) across an inhomogeneous magnetic field distribution of which the direction and strength change along the penetration trajectory has been studied. The bulk velocity decreases when the plasma element penetrates into a region of increasing magnetic field. The critical magnetic field intensity where a plasmoid is stopped or deflected is found to be the same critical field as that which has been observed in laboratory experiments for a non-rotating B-field distribution. The polarization electric field induced inside a moving plasma element has been determined for both low-β and high-β plasmoids. The momentum density vector of a plasmoid is deflected in the – B × ∇B and – B × (B. ∇)B directions as it penetrates into an inhomogeneous B-field distribution. This kinetic model has been applied to the impulsive penetration of solar wind plasma irregularities impinging on the earth's geomagnetic field with an excess momentum density. As a consequence of impulsive penetration, a plasma boundary layer is formed where the intruding plasmoids are deflected eastward. Magnetospheric plasma is dragged in the direction parallel to the flanks of the average magnetopause surface. Diamagnetic effects of these impulsively penetrating plasmoids into the magnetosphere are also briefly discussed.

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Markidis, S., P. Henri, G. Lapenta, A. Divin, M. V. Goldman, D. Newman e S. Eriksson. "Collisionless magnetic reconnection in a plasmoid chain". Nonlinear Processes in Geophysics 19, n.º 1 (27 de fevereiro de 2012): 145–53. http://dx.doi.org/10.5194/npg-19-145-2012.

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Abstract. The kinetic features of plasmoid chain formation and evolution are investigated by two dimensional Particle-in-Cell simulations. Magnetic reconnection is initiated in multiple X points by the tearing instability. Plasmoids form and grow in size by continuously coalescing. Each chain plasmoid exhibits a strong out-of plane core magnetic field and an out-of-plane electron current that drives the coalescing process. The disappearance of the X points in the coalescence process are due to anti-reconnection, a magnetic reconnection where the plasma inflow and outflow are reversed with respect to the original reconnection flow pattern. Anti-reconnection is characterized by the Hall magnetic field quadrupole signature. Two new kinetic features, not reported by previous studies of plasmoid chain evolution, are here revealed. First, intense electric fields develop in-plane normally to the separatrices and drive the ion dynamics in the plasmoids. Second, several bipolar electric field structures are localized in proximity of the plasmoid chain. The analysis of the electron distribution function and phase space reveals the presence of counter-streaming electron beams, unstable to the two stream instability, and phase space electron holes along the reconnection separatrices.

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AHMAD, Nisar, Ping ZHU, Ahmad ALI e Shiyong ZENG. "Viscous effects on plasmoid formation from nonlinear resistive tearing growth in a Harris sheet". Plasma Science and Technology 24, n.º 1 (23 de novembro de 2021): 015103. http://dx.doi.org/10.1088/2058-6272/ac3563.

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Abstract In this work, the evolution of a highly unstable m = 1 resistive tearing mode, leading to plasmoid formation in a Harris sheet, is studied in the framework of full MHD model using the Non-Ideal Magnetohydrodynamics with Rotation, Open Discussion simulation. Following the initial nonlinear growth of the primary m = 1 island, the X-point develops into a secondary elongated current sheet that eventually breaks into plasmoids. Two distinctive viscous regimes are found for the plasmoid formation and saturation. In the low viscosity regime (i.e. P r ≲ 1), the plasmoid width increases sharply with viscosity, whereas in the viscosity dominant regime (i.e. P r ≳ 1), the plasmoid size gradually decreases with viscosity. Such a finding quantifies the role of viscosity in modulating the plasmoid formation process through its effects on the plasma flow and the reconnection itself.

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Dubowsky, Scott E., Amber N. Rose, Nick G. Glumac e Benjamin J. McCall. "Electrical Properties of Reversed-Polarity Ball Plasmoid Discharges". Plasma 3, n.º 3 (29 de junho de 2020): 92–102. http://dx.doi.org/10.3390/plasma3030008.

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Ball plasmoid discharges are a unique type of atmospheric-pressure plasma discharge with a lifetime on the order of a hundred milliseconds without attachment to a power source. These discharges are generated by a moderate current pulse over the surface of an aqueous electrolyte, and some consider the spherical plasmoid that results to bear some resemblance to ball lightning. This article presents the first analysis of the electrical properties of ball plasmoid discharges in a reversed-polarity configuration, i.e., with the central electrode serving as the anode rather than as the cathode. These experiments demonstrate that ball plasmoids can indeed be generated with either electrode polarity with similar observable properties. These results are contrary to what has previously been discussed in the literature and raise additional questions regarding formation mechanisms of ball plasmoids. Analysis of images and electrical measurements collected at various discharge energies show that two distinct processes occur during discharges with our circuitry and in this reversed-polarity configuration: the formation of spark channels between the anode and electrolyte, and the generation of streamers and a jet from the surface of the anode.

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Belehaki, A., R. W. McEntire, S. Kokubun e T. Yamamoto. "Magnetotail response during a strong substorm as observed by GEOTAIL in the distant tail". Annales Geophysicae 16, n.º 5 (31 de maio de 1998): 528–41. http://dx.doi.org/10.1007/s00585-998-0528-5.

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Abstract. Simultaneous energetic particle and magnetic field observations from the GEOTAIL spacecraft in the distant tail (XGSM≈ –150 Re) have been analysed to study the response of the Earth's magnetotail during a strong substorm (AE ≤ 680 nT). At geosynchronous altitude, LANL spacecraft recorded three electron injections between 0030 UT and 0130 UT, which correspond to onsets observed on the ground at Kiruna Ground Observatory. The Earth's magnetotail responded to this substorm with the ejection of five plasmoids, whose size decreases from one plasmoid to the next. Since the type of magnetic structure detected by a spacecraft residing the lobes, depends on the Z extent of the structure passing underneath the spacecraft, GEOTAIL is first engulfed by a plasmoid structure; six minutes later it detects a boundary layer plasmoid (BLP) and finally at the recovery phase of the substorm GEOTAIL observes three travelling compression regions (TCRs). The time-of-flight (TOF) speed of these magnetic structures was estimated to range between 510 km/s and 620 km/s. The length of these individual plasmoids was calculated to be between 28 Re and 56 Re. The principal axis analysis performed on the magnetic field during the TCR encountered, has confirmed that GEOTAIL observed a 2-D perturbation in the X-Z plane due to the passage of a plasmoid underneath. The first large plasmoid that engulfed GEOTAIL was much more complicated in nature probably due to the external, variable draped field lines associated with high beta plasma sheet and the PSBL flux tubes surrounding the plasmoid. From the analysis of the energetic particle angular distribution, evidence was found that ions were accelerated from the distant X-line at the onset of the burst associated with the first magnetic structure. Key words. Magnetospheric physics (magnetospheric configuration and dynamics; magnetotail).

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Cerutti, Benoît, e Gwenael Giacinti. "Formation of giant plasmoids at the pulsar wind termination shock: A possible origin of the inner-ring knots in the Crab Nebula". Astronomy & Astrophysics 656 (dezembro de 2021): A91. http://dx.doi.org/10.1051/0004-6361/202142178.

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Context. Nearby pulsar wind nebulae exhibit complex morphological features: jets, torus, arcs, and knots. These structures are well captured and understood in the scope of global magnetohydrodynamic models. However, the origin of knots in the inner radius of the Crab Nebula remains elusive. Aims. In this work, we investigate the dynamics of the shock front and downstream flow with a special emphasis on the reconnecting equatorial current sheet. We examine whether giant plasmoids produced in the reconnection process could be good candidates for the knots. Methods. To this end, we perform large semi-global three-dimensional particle-in-cell simulations in a spherical geometry. The hierarchical merging plasmoid model is used to extrapolate numerical results to pulsar wind nebula scales. Results. The shocked material collapses into the midplane, forming and feeding a large-scale, but thin, ring-like current layer. The sheet breaks up into a dynamical chain of merging plasmoids, reminiscent of three-dimensional reconnection. Plasmoids grow to a macroscopic size. The final number of plasmoids predicted is solely governed by the inverse of the dimensionless reconnection rate. Conclusions. The formation of giant plasmoids is a robust feature of pulsar wind termination shocks. They provide a natural explanation for the inner-ring knots in the Crab Nebula, provided that the nebula is highly magnetized.

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Ugai, M. "Virtual satellite observations of plasmoids generated by fast reconnection in the geomagnetic tail". Annales Geophysicae 29, n.º 8 (23 de agosto de 2011): 1411–22. http://dx.doi.org/10.5194/angeo-29-1411-2011.

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Abstract. The present paper studies fundamental features of plasmoid propagation by virtual satellite observations in the simulation box. The plasmoid domain is divided into the plasmoid reconnection region P, where magnetized plasmas with reconnected field lines, heated by dissipation mechanisms of fast reconnection, are accumulated, and the plasmoid core region C, where magnetized plasmas with sheared field lines, initially embedded in the current sheet, is adiabatically compressed. When the virtual satellite is located in a position through which the plasmoid core region passes, it detects distinct changes in quantities at the interface between the regions P and C, where the north-south field component Bz has the bipolar profile and the sheared field component By has the peak value. The observed magnetic field profile is, both quantitatively and qualitatively, in good agreement with the standard one detected by actual satellite observations, although when the satellite location is very close to the X neutral line, where reconnection occurs, the Bz field profile becomes dipolarization-like rather than bipolar. If the satellite detects only the plasmoid region P outside region C, the standard magnetic field profile becomes obscure even if notable plasmoid signatures, such as enhanced plasma temperature and plasma flow, are observed. Unlike the traditional flux rope model based on multiple reconnections, it is demonstrated that the standard magnetic field profile, observed for plasmoids propagating in the geomagnetic tail, is the direct outcome of the single fast reconnection evolution.

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Dvornikov, M. "Stable Langmuir solitons in plasma with diatomic ions". Nonlinear Processes in Geophysics 20, n.º 4 (13 de agosto de 2013): 581–88. http://dx.doi.org/10.5194/npg-20-581-2013.

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Abstract. We study stable axially and spherically symmetric spatial solitons in plasma with diatomic ions. The stability of a soliton against collapse is provided by the interaction of induced electric dipole moments of ions with the rapidly oscillating electric field of a plasmoid. We derive the new cubic-quintic nonlinear Schrödinger equation, which governs the soliton dynamics and numerically solve it. Then we discuss the possibility of implementation of such plasmoids in realistic atmospheric plasma. In particular, we suggest that spherically symmetric Langmuir solitons, described in the present work, can be excited at the formation stage of long-lived atmospheric plasma structures. The implication of our model for the interpretation of the results of experiments for the plasmoids generation is discussed.

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Nagai, T., H. Tsunakawa, H. Shibuya, F. Takahashi, H. Shimizu, M. Matsushima, M. N. Nishino et al. "Plasmoid formation for multiple onset substorms: observations of the Japanese Lunar Mission "Kaguya"". Annales Geophysicae 27, n.º 1 (6 de janeiro de 2009): 59–64. http://dx.doi.org/10.5194/angeo-27-59-2009.

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Abstract. The Japanese Lunar Mission "Kaguya" carried out its first magnetic field and plasma measurements in the Earth's magnetotail on 22 December 2007. Fortuitously, three well-defined multiple onset substoms took place. Kaguya was located in the premidnight magnetotail at radial distances of 56 RE and observed plasmoids and/or traveling compression regions (TCRs). Although the present study is based on limited data sets, important issues on multiple onset substorms can be examined. Each onset in a series of onsets releases a plasmoid, and magnetic reconnection likely proceeds to tail lobe field lines for each onset. Since the duration of each plasmoid is less than 5 min, these observations imply that magnetic reconnection for each onset can develop fully to the tail lobe field lines and be quenched within this timescale.

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Gou, Tingyu, Rui Liu, Bernhard Kliem, Yuming Wang e Astrid M. Veronig. "The birth of a coronal mass ejection". Science Advances 5, n.º 3 (março de 2019): eaau7004. http://dx.doi.org/10.1126/sciadv.aau7004.

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The Sun’s atmosphere is frequently disrupted by coronal mass ejections (CMEs), coupled with flares and energetic particles. The coupling is usually attributed to magnetic reconnection at a vertical current sheet connecting the flare and CME, with the latter embedding a helical magnetic structure known as flux rope. However, both the origin of flux ropes and their nascent paths toward eruption remain elusive. Here, we present an observation of how a stellar-sized CME bubble evolves continuously from plasmoids, mini flux ropes that are barely resolved, within half an hour. The eruption initiates when plasmoids springing from a vertical current sheet merge into a leading plasmoid, which rises at increasing speeds and expands impulsively into the CME bubble, producing hard x-ray bursts simultaneously. This observation illuminates a complete CME evolutionary path capable of accommodating a wide variety of plasma phenomena by bridging the gap between microscale and macroscale dynamics.

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Patel, Ritesh, Vaibhav Pant, Kalugodu Chandrashekhar e Dipankar Banerjee. "A statistical study of plasmoids associated with a post-CME current sheet". Astronomy & Astrophysics 644 (dezembro de 2020): A158. http://dx.doi.org/10.1051/0004-6361/202039000.

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Context. Coronal mass ejections (CMEs) are often observed to be accompanied by flare, current sheets, and plasmoids/plasma blobs. 2D and 3D numerical simulations and observations reported plasmoids moving upward as well as downward along the current sheet. Aims. We aim to investigate the properties of plasmoids observed in the current sheet formed after an X-8.3 flare and followed by a fast CME eruption on September 10, 2017 using extreme-ultraviolet (EUV) and white-light coronagraph images. The main goal is to understand the evolution of plasmoids in different spatio-temporal scales using existing ground- and space-based instruments. Methods. We identified the plasmoids manually and tracked them along the current sheet in the successive images of Atmospheric Imaging Assembly (AIA) taken at the 131 Å pass band and in running difference images of the white-light coronagraphs, K-Cor and LASCO/C2. The location and size of the plasmoids in each image were recorded and analyzed, covering the current sheet from the inner to outer corona. Results. We find that the observed current sheet has an Alfvén Mach number of 0.018−0.35. The fast reconnection is also accompanied by plasmoids moving upward and downward. We identified 20 downward-moving and 16 upward-moving plasmoids using AIA 131 Å images. In white-light coronagraph images, only upward-moving plasmoids are observed. Our analysis shows that the downward-moving plasmoids have an average width of 5.92 Mm, whereas upward-moving blobs have an average size of 5.65 Mm in the AIA field of view (FOV). The upward-moving plasmoids, when observed in the white-light images, have an average width of 64 Mm in the K-Cor, which evolves to a mean width of 510 Mm in the LASCO/C2 FOV. Upon tracking the plasmoids in successive images, we find that downward- and upward-moving plasmoids have average speeds of ∼272 km s−1 and ∼191 km s−1, respectively in the EUV channels of observation. The average speed of plasmoids increases to ∼671 km s−1 and ∼1080 km s−1 in the K-Cor and LASCO/C2 FOVs, respectively, implying that the plasmoids become super-Alfvénic when they propagate outward. The downward-moving plasmoids show an acceleration in the range of −11 km s−1 to over 8 km s−1. We also find that the null point of the current sheet is located at ≈1.15 R⊙, where bidirectional plasmoid motion is observed. Conclusions. The width distribution of plasmoids formed during the reconnection process is governed by a power law with an index of −1.12. Unlike previous studies, there is no difference in trend for small- and large-scale plasmoids. The evolution of width W of the plasmoids moving at an average speed V along the current sheet is governed by an empirical relation: V = 115.69W0.37. The presence of accelerating plasmoids near the neutral point indicates a longer diffusion region as predicted by MHD models.

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Nathanail, Antonios, Christian M. Fromm, Oliver Porth, Hector Olivares, Ziri Younsi, Yosuke Mizuno e Luciano Rezzolla. "Plasmoid formation in global GRMHD simulations and AGN flares". Monthly Notices of the Royal Astronomical Society 495, n.º 2 (23 de maio de 2020): 1549–65. http://dx.doi.org/10.1093/mnras/staa1165.

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ABSTRACT One of the main dissipation processes acting on all scales in relativistic jets is thought to be governed by magnetic reconnection. Such dissipation processes have been studied in idealized environments, such as reconnection layers, which evolve in merging islands and lead to the production of ‘plasmoids’, ultimately resulting in efficient particle acceleration. In accretion flows on to black holes, reconnection layers can be developed and destroyed rapidly during the turbulent evolution of the flow. We present a series of two-dimensional general-relativistic magnetohydrodynamic simulations of tori accreting on to rotating black holes focusing our attention on the formation and evolution of current sheets. Initially, the tori are endowed with a poloidal magnetic field having a multiloop structure along the radial direction and with an alternating polarity. During reconnection processes, plasmoids and plasmoid chains are developed leading to a flaring activity and hence to a variable electromagnetic luminosity. We describe the methods developed to track automatically the plasmoids that are generated and ejected during the simulation, contrasting the behaviour of multiloop initial data with that encountered in typical simulations of accreting black holes having initial dipolar field composed of one loop only. Finally, we discuss the implications that our results have on the variability to be expected in accreting supermassive black holes.

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Hoshino, M. "Small scale plasmoids in the post-plasmoid plasma sheet: Origin of MHD turbulence?" Advances in Space Research 25, n.º 7-8 (janeiro de 2000): 1685–88. http://dx.doi.org/10.1016/s0273-1177(99)00684-5.

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Xie, Xiaoyan, Zhixing Mei, Chengcai Shen, Qiangwei Cai, Jing Ye, Katharine K. Reeves, Ilia I. Roussev e Jun Lin. "Numerical experiments on dynamic evolution of a CME-flare current sheet". Monthly Notices of the Royal Astronomical Society 509, n.º 1 (19 de outubro de 2021): 406–20. http://dx.doi.org/10.1093/mnras/stab2954.

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ABSTRACT In this paper, we performed magnetohydrodynamics numerical experiments to look into the dynamic behaviour of the current sheet (CS) between the coronal mass ejection (CME) and the associated solar flare, especially the CS oscillation and plasmoid motions in coronal conditions. During the evolution, the disrupting magnetic configuration becomes asymmetric first in the buffer region at the bottom of the CME bubble. The Rayleigh−Taylor instability in the buffer region and the deflected motion of the plasma driven by the termination shock at the bottom of the CME bubble cause the buffer region to oscillate around the y-axis. The local oscillation propagates downwards through the CS, prompting an overall CS oscillation. As the buffer region grows, the oscillation period becomes longer, increasing from about 30 s to about 16 min. Meanwhile, there is another separated oscillation with a period between 0.25 and 1.5 min in the cusp region of the flare generated by velocity shearing. The tearing mode instability yields formations of plasmoids inside the CS. The motions of all the plasmoids observed in the experiment accelerate, which implies that the large-scale CME/flare CS itself in the true eruptive event is filled with the diffusion region according the the standard theory of magnetic reconnection.

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Moldwin, Mark B., e W. Jeffrey Hughes. "Observations of earthward and tailward propagating flux rope plasmoids: Expanding the plasmoid model of geomagnetic substorms". Journal of Geophysical Research 99, A1 (1994): 183. http://dx.doi.org/10.1029/93ja02102.

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W Hones Jr, Edward. "Magnetic Reconnection in the Earth's Magnetotail". Australian Journal of Physics 38, n.º 6 (1985): 981. http://dx.doi.org/10.1071/ph850981.

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Over the past few years satellite observations of the plasma sheet in the Earth's magnetotail during magnetospheric substorms have established beyond reasonable doubt that magnetic reconnection occurs in the magnetotail and that it plays a central role in the substorm process. The features seen at Earth by which substorms were originally identified (e.g. the auroras and geomagnetic disturbances) are simply superficial manifestations of a more fundamental physical process-the magnetosphere divesting itself of stored energy and plasma that was acquired earlier from the solar wind. It does so by shedding a part of its plasma sheet. This is accomplished by magnetic reconnection near the Earth that severs the plasma sheet, forming a plasmoid that flows out of the tail and that is lost to the solar wind. Recognition of the existence of plasmoids and our developing understanding of them have been important elements in confirming the occurrence of reconnection in the magnetosphere. In an analogous way, the best evidence for the occurrence of reconnection on the Sun has come from observations of closed magnetic configurations (plasmoids) in the solar wind and in the corona. But while magnetic reconnection is certainly the key ingredient in solar flares and substorms, analogies between them should not be carried too far, because there are basic differences in the environments in which they prevail and in the physical procesSes that lead to their occurrence.

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Richardson, I. G., S. W. H. Cowley, E. W. Hones e S. J. Bame. "Plasmoid-associated energetic ion bursts in the deep geomagnetic tail: Properties of plasmoids and the postplasmoid plasma sheet". Journal of Geophysical Research 92, A9 (1987): 9997. http://dx.doi.org/10.1029/ja092ia09p09997.

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Baker, D. N., T. A. Fritz e P. A. Bernhardt. "Plasmoid Velocity". Science 243, n.º 4892 (10 de fevereiro de 1989): 713. http://dx.doi.org/10.1126/science.243.4892.713.d.

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Baker, D. N., T. A. Fritz e P. A. Bernhardt. "Plasmoid Velocity". Science 243, n.º 4892 (10 de fevereiro de 1989): 713. http://dx.doi.org/10.1126/science.243.4892.713-c.

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Peter, H., Y. M. Huang, L. P. Chitta e P. R. Young. "Plasmoid-mediated reconnection in solar UV bursts". Astronomy & Astrophysics 628 (25 de julho de 2019): A8. http://dx.doi.org/10.1051/0004-6361/201935820.

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Context. Ultraviolet bursts are transients in the solar atmosphere with an increased impulsive emission in the extreme UV lasting for one to several tens of minutes. They often show spectral profiles indicative of a bi-directional outflow in response to magnetic reconnection. Aims. To understand UV bursts, we study how motions of magnetic elements at the surface can drive the self-consistent formation of a current sheet resulting in plasmoid-mediated reconnection. In particular, we want to study the role of the height of the reconnection in the atmosphere. Methods. We conducted numerical experiments solving the 2D magnetohydrodynamic equations from the solar surface to the upper atmosphere. Motivated by observations, we drove a small magnetic patch embedded in a larger system of magnetic field of opposite polarity. This type of configuration creates an X-type neutral point in the initial potential field. The models are characterized by the (average) plasma-β at the height of this X point. Results. The driving at the surface stretches the X-point into a thin current sheet, where plasmoids appear, accelerating the reconnection, and a bi-directional jet forms. This is consistent with what is expected for UV bursts or explosive events, and we provide a self-consistent model of the formation of the reconnection region in such events. The gravitational stratification gives a natural explanation for why explosive events are restricted to a temperature range around a few 0.1 MK, and the presence of plasmoids in the reconnection process provides an understanding of the observed variability during the transient events on a timescale of minutes. Conclusions. Our numerical experiments provide a comprehensive understanding of UV bursts and explosive events, in particular of how the atmospheric response changes if the reconnection happens at different plasma-β, that is, at different heights in the atmosphere. This analysis also gives new insight into how UV bursts might be related to the photospheric Ellerman bombs.

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Gao, Guannan, Qiangwei Cai, Shaojie Guo e Min Wang. "Decimetric Type-U Solar Radio Bursts and Associated EUV Phenomena on 2011 February 9". Astrophysical Journal 923, n.º 2 (1 de dezembro de 2021): 268. http://dx.doi.org/10.3847/1538-4357/ac3135.

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Abstract A GOES M1.9 flare took place in active region AR 11153 on 2011 February 9. With a resolution of 200 kHz and a time cadence of 80 ms, the reverse-drifting (RS) type-III bursts, intermittent sequence of type-U bursts, drifting pulsation structure (DPS), and fine structures were observed by the Yunnan Observatories Solar Radio Spectrometer (YNSRS). Combined information revealed by the multiwavelength data indicated that after the DPS was observed by YNSRS, the generation rate of type-U bursts suddenly increased to 5 times what it had been. In this event, the generation rate of type-U bursts may depend on the magnetic-reconnection rate. Our observations are consistent with previous numerical simulation results. After the first plasmoid produced (plasma instability occurred), the magnetic-reconnection rate suddenly increased by 5 to 8 times. Furthermore, after the DPS, the frequency range of the turnover frequency of type-U bursts was obviously broadened to thrice what it was before, which indicates a fluctuation amplitude of the density in the loop top. Our observations also support numerical simulations during the flare-impulsive phase. Turbulence occurs at the top of the flare loop and the plasmoids can trap nonthermal particles, causing density fluctuation at the loop top. The observations are generally consistent with the results of numerical simulations, helping us to better understand the characteristics of the whole physical process of eruption.

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Agarwal, S., B. Banerjee, A. Shukla, J. Roy, S. Acharya, B. Vaidya, V. R. Chitnis, S. M. Wagner, K. Mannheim e M. Branchesi. "Flaring activity from magnetic reconnection in BL Lacertae". Monthly Notices of the Royal Astronomical Society: Letters 521, n.º 1 (14 de fevereiro de 2023): L53—L58. http://dx.doi.org/10.1093/mnrasl/slad023.

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ABSTRACT The evolution of the spectral energy distribution during flares constrains models of particle acceleration in blazar jets. The archetypical blazar BL Lacertae provided a unique opportunity to study spectral variations during an extended strong flaring episode from 2020 to 2021. During its brightest γ-ray state, the observed flux (0.1–300 GeV) reached up to $2.15\, \times \, 10^{-5}\, \rm {ph\, cm^{-2}\, s^{-1}}$, with sub-hour-scale variability. The synchrotron hump extended into the X-ray regime showing a minute-scale flare with an associated peak shift of inverse-Compton hump in γ-rays. In shock acceleration models, a high Doppler factor value >100 is required to explain the observed rapid variability, change of state, and γ-ray peak shift. Assuming particle acceleration in minijets produced by magnetic reconnection during flares, on the other hand, alleviates the constraint on required bulk Doppler factor. In such jet-in-jet models, observed spectral shift to higher energies (towards TeV regime) and simultaneous rapid variability arises from the accidental alignment of a magnetic plasmoid with the direction of the line of sight. We infer a magnetic field of ∼0.6 G in a reconnection region located at the edge of broad-line region (∼0.02 pc). The scenario is further supported by lognormal flux distribution arising from merging of plasmoids in reconnection region.

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26

Ugai, M. "Magnetic field structure of large-scale plasmoid generated by the fast reconnection mechanism in a sheared current sheet". Annales Geophysicae 28, n.º 8 (11 de agosto de 2010): 1511–21. http://dx.doi.org/10.5194/angeo-28-1511-2010.

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Abstract. On the basis of the spontaneous fast reconnection model, three-dimensional magnetic field profiles associated with a large-scale plasmoid propagating along the antiparallel magnetic fields are studied in the general sheared current sheet system. The plasmoid is generated ahead of the fast reconnection jet as a result of distinct compression of the magnetized plasma. Inside the plasmoid, the sheared (east-west) field component has the peak value at the plasmoid center located at x=XC, where the north-south field component changes its sign. The plasmoid center corresponds to the so-called contact discontinuity that bounds the reconnected field lines in x<XC and the field lines without reconnection in x>XC. Hence, contray to the conventional prediction, the reconnected sheared field lines in x<XC are not spiral or helical, since they cannot be topologically connected to the field lines in x>XC. It is demonstrated that the resulting profiles of magnetic field components inside the plasmoid are, in principle, consistent with satellite observations. In the ambient magnetic field region outside the plasmoid too, the magnetic field profiles are in good agreement with the well-known observations of traveling compression regions (TCRs).

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27

Delannée, C., S. Koutchmy, A. Zhukov e I. Veselovsky. "Coronal Plasmoid Dynamics". International Astronomical Union Colloquium 167 (1998): 388–92. http://dx.doi.org/10.1017/s0252921100047977.

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AbstractA possible acceleration mechanism by the magnetic force is suggested for a plasmoid, modeled as a spherical body with a magnetic dipole situated in its center of mass. The governing equations of the motion of a dipole in an inhomogeneous magnetic field are solved analytically and numerically. Both methods show the possibility for the plasmoid to be accelerated in the direction of the external field gradient.

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28

Gunell, H., G. Stenberg Wieser, M. Mella, R. Maggiolo, H. Nilsson, F. Darrouzet, M. Hamrin et al. "Waves in high-speed plasmoids in the magnetosheath and at the magnetopause". Annales Geophysicae 32, n.º 8 (22 de agosto de 2014): 991–1009. http://dx.doi.org/10.5194/angeo-32-991-2014.

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Abstract. Plasmoids, defined here as plasma entities with a higher anti-sunward velocity component than the surrounding plasma, have been observed in the magnetosheath in recent years. During the month of March 2007 the Cluster spacecraft crossed the magnetopause near the subsolar point 13 times. Plasmoids with larger velocities than the surrounding magnetosheath were found on seven of these 13 occasions. The plasmoids approach the magnetopause and interact with it. Both whistler mode waves and waves in the lower hybrid frequency range appear in these plasmoids, and the energy density of the waves inside the plasmoids is higher than the average wave energy density in the magnetosheath. When the spacecraft are in the magnetosphere, Alfvénic waves are observed. Cold ions of ionospheric origin are seen in connection with these waves, when the wave electric and magnetic fields combine with the Earth's dc magnetic field to yield an E × B/B2 drift speed that is large enough to give the ions energies above the detection threshold.

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29

Lu, Lei, Li Feng, Alexander Warmuth, Astrid M. Veronig, Jing Huang, Siming Liu, Weiqun Gan, Zongjun Ning, Beili Ying e Guannan Gao. "Observational Signatures of Tearing Instability in the Current Sheet of a Solar Flare". Astrophysical Journal Letters 924, n.º 1 (1 de janeiro de 2022): L7. http://dx.doi.org/10.3847/2041-8213/ac42c6.

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Abstract Magnetic reconnection is a fundamental physical process converting magnetic energy into not only plasma energy but also particle energy in various astrophysical phenomena. In this Letter, we show a unique data set of a solar flare where various plasmoids were formed by a continually stretched current sheet. Extreme ultraviolet images captured reconnection inflows, outflows, and particularly the recurring plasma blobs (plasmoids). X-ray images reveal nonthermal emission sources at the lower end of the current sheet, presumably as large plasmoids with a sufficiently amount of energetic electrons trapped in them. In the radio domain, an upward, slowly drifting pulsation structure, followed by a rare pair of oppositely drifting structures, was observed. These structures are supposed to map the evolution of the primary and the secondary plasmoids formed in the current sheet. Our results on plasmoids at different locations and scales shed important light on the dynamics, plasma heating, particle acceleration, and transport processes in the turbulent current sheet and provide observational evidence for the cascading magnetic reconnection process.

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30

Hill, T. W., M. F. Thomsen, M. G. Henderson, R. L. Tokar, A. J. Coates, H. J. McAndrews, G. R. Lewis et al. "Plasmoids in Saturn's magnetotail". Journal of Geophysical Research: Space Physics 113, A1 (janeiro de 2008): n/a. http://dx.doi.org/10.1029/2007ja012626.

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31

Borgogno, Dario, Daniela Grasso, Beatrice Achilli, Massimiliano Romé e Luca Comisso. "Coexistence of Plasmoid and Kelvin–Helmholtz Instabilities in Collisionless Plasma Turbulence". Astrophysical Journal 929, n.º 1 (1 de abril de 2022): 62. http://dx.doi.org/10.3847/1538-4357/ac582f.

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Abstract The plasmoid formation in collisionless plasmas, where magnetic reconnection within turbulence may take place driven by the electron inertia, is analyzed. We find a complex situation in which, due to the presence of strong velocity shears, the typical plasmoid formation, observed to influence the energy cascade in the magnetohydrodynamic context, has to coexist with the Kelvin–Helmholtz (KH) instability. We find that the current density layers may undergo the plasmoid or the KH instability depending on the local values of the magnetic and velocity fields. The competition among these instabilities affects not only the evolution of the current sheets, that may generate plasmoid chains or KH-driven vortices, but also the energy cascade, that is different for the magnetic and kinetic spectra.

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32

Comisso, Luca, e Daniela Grasso. "Visco-resistive plasmoid instability". Physics of Plasmas 23, n.º 3 (março de 2016): 032111. http://dx.doi.org/10.1063/1.4942940.

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Ugai, M. "The structure and dynamics of a large-scale plasmoid generated by fast reconnection in the geomagnetic tail". Annales Geophysicae 29, n.º 1 (13 de janeiro de 2011): 147–56. http://dx.doi.org/10.5194/angeo-29-147-2011.

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Abstract. As a sequence of Ugai (2010b), the present paper studies in detail the structure and dynamics of large-scale (principal) plasmoid, generated by the fast reconnection evolution in a sheared current sheet with no initial northward field component. The overall plasmoid domain is divided into the plasmoid reconnection region P and the plasmoid core region C. In the region P, the magnetized plasma with reconnected field lines are accumulated, whereas in the region C, the plasma, which was intially embedded in the current sheet and has been ejected away by the reconnection jet, is compressed and accumulated. In the presence of the sheared magnetic field in the east-west direction in the current sheet, the upper and lower parts of the reconnection region P are inversely shifted in the east-west directions. Accordingly, the plasmoid core region C with the accumulated sheared field lines is bent in the north-south direction just ahead of the plasmoid center x=XC, causing the magnetic field component in the north-south direction, whose sign is always opposite to that of the reconnected field lines. Therefore, independently of the sign of the initial sheared field, the magnetic field component Bz in the north-south direction has the definite bipolar profile around XC along the x-axis. At x=XC, the sheared field component has the peak value, and as the sheared fields accumulated in the region C become larger, the bipolar field profile becomes more distinct.

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34

Nitta, Shin-ya, e Koji Kondoh. "Effects of Magnetic Shear and Thermodynamic Asymmetry on Spontaneous Magnetohydrodynamic Reconnection". Astrophysical Journal 936, n.º 2 (1 de setembro de 2022): 125. http://dx.doi.org/10.3847/1538-4357/ac729f.

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Abstract The spontaneous evolution of magnetic reconnection in generalized situations (with thermodynamic asymmetry regarding the current sheet and magnetic shear) is investigated using a two-dimensional magnetohydrodynamic simulation. We focus on the asymptotic state of temporal evolution, i.e., the self-similarly expanding phase. (1) A long fast-mode shock is generated in front of the shorter plasmoid as in the shear-less thermodynamically asymmetric case; however, the sheared magnetic component weakens the shock. This fast shock may work as a particle acceleration site. (2) The shorter plasmoid-side plasma infiltrates the longer plasmoid across the current sheet. Then, the plasmas from both sides of the current sheet coexist on the same magnetic field lines in the longer plasmoid. This may result in efficient plasma mixing. (3) The thermodynamic asymmetry and magnetic shear drastically decrease the reconnection rate in many orders of magnitude.

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35

TAKAMOTO, MAKOTO. "EVOLUTION OF PLASMOID-CHAIN IN POYNTING-DOMINATED PLASMA". International Journal of Modern Physics: Conference Series 28 (janeiro de 2014): 1460170. http://dx.doi.org/10.1142/s2010194514601707.

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We present our recent results of the evolution of the plasmoid-chain in a Poynting dominated plasma. We model the relativistic current sheet with cold background plasma using the relativistic resistive magnetohydrodynamic approximation, and solve its temporal evolution numerically. Numerical results show that the initially induced plasmoid triggers a secondary tearing instability. We find the plasmoid-chain greatly enhances the reconnection rate, which becomes independent of the Lundquist number, when this exceeds a critical value. Since magnetic reconnection is expected to play an important role in various high energy astrophysical phenomena, our results can be used for explaining the physical mechanism of them.

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36

McFadden, Geoffrey Ian. "Plasmodia – don’t". Trends in Parasitology 28, n.º 8 (agosto de 2012): 306. http://dx.doi.org/10.1016/j.pt.2012.05.006.

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37

Moldwin, Mark B., e W. Jeffrey Hughes. "Geomagnetic substorm association of plasmoids". Journal of Geophysical Research: Space Physics 98, A1 (1 de janeiro de 1993): 81–88. http://dx.doi.org/10.1029/92ja02153.

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Moldwin, Mark B., e W. Jeffrey Hughes. "Plasmoids as magnetic flux ropes". Journal of Geophysical Research: Space Physics 96, A8 (1 de agosto de 1991): 14051–64. http://dx.doi.org/10.1029/91ja01167.

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39

Nagai, T., R. Nakamura, T. Mukai, T. Yamamoto, A. Nishida e S. Kokubun. "Substorms, tail flows and plasmoids". Advances in Space Research 20, n.º 4-5 (janeiro de 1997): 961–71. http://dx.doi.org/10.1016/s0273-1177(97)00504-8.

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40

Pothiraja, Ramasamy, Nikita Bibinov e Peter Awakowicz. "Plasmoids for etching and deposition". Journal of Physics D: Applied Physics 47, n.º 45 (23 de outubro de 2014): 455203. http://dx.doi.org/10.1088/0022-3727/47/45/455203.

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Ortuño-Macías, José, e Krzysztof Nalewajko. "Radiative kinetic simulations of steady-state relativistic plasmoid magnetic reconnection". Monthly Notices of the Royal Astronomical Society 497, n.º 2 (3 de julho de 2020): 1365–81. http://dx.doi.org/10.1093/mnras/staa1899.

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ABSTRACT We present the results of two-dimensional 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 Θ. We explore different values of Θ and of the background magnetization σ0. 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 light curves 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-magnetization case, the accelerated particles form a broken power-law energy distribution with a soft tail produced by particles accelerated in the minijets.

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42

Zhang, W., Z. W. Ma, H. W. Zhang, W. J. Chen e X. Wang. "Influence of aspect ratio, plasma viscosity, and radial position of the resonant surfaces on the plasmoid formation in the low resistivity plasma in Tokamak". Nuclear Fusion 62, n.º 3 (20 de janeiro de 2022): 036007. http://dx.doi.org/10.1088/1741-4326/ac46f8.

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Abstract In the present paper, we systematically investigate the nonlinear evolution of the resistive kink mode in the low resistivity plasma in Tokamak geometry. We find that the aspect ratio of the initial equilibrium can significantly influence the critical resistivity for plasmoid formation. With the aspect ratio of 3/1, the critical resistivity can be one magnitude larger than that in cylindrical geometry due to the strong mode–mode coupling. We also find that the critical resistivity for plasmoid formation η crit decreases with increasing plasma viscosity in the moderately low resistivity regime. Due to the geometry of Tokamaks, the critical resistivity for plasmoid formation increases with the increasing radial location of the resonant surface.

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43

ISHIZAKI, Ryuichi, e Noriyoshi NAKAJIMA. "Plasmoid Motion in Helical Plasmas". Plasma and Fusion Research 5 (2010): S2060. http://dx.doi.org/10.1585/pfr.5.s2060.

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Abe, Shu A., e M. Hoshino. "Nonlinear evolution of plasmoid structure". Earth, Planets and Space 53, n.º 6 (junho de 2001): 663–71. http://dx.doi.org/10.1186/bf03353286.

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Stepanov, S. I. "Ultrasonic sensing of a plasmoid". Technical Physics 59, n.º 1 (janeiro de 2014): 107–12. http://dx.doi.org/10.1134/s1063784214010198.

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46

Ieda, A., D. H. Fairfield, T. Mukai, Y. Saito, S. Kokubun, K. Liou, C. I. Meng, G. K. Parks e M. J. Brittnacher. "Plasmoid ejection and auroral brightenings". Journal of Geophysical Research: Space Physics 106, A3 (1 de março de 2001): 3845–57. http://dx.doi.org/10.1029/1999ja000451.

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47

Yang, W. H. "Expanding force-free magnetized plasmoid". Astrophysical Journal 348 (janeiro de 1990): L73. http://dx.doi.org/10.1086/185634.

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48

Saunders, Mark. "The birth of a plasmoid". Nature 339, n.º 6227 (junho de 1989): 659–60. http://dx.doi.org/10.1038/339659a0.

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Magara, T., e K. Shibata. "Plasmoid formation in eruptive flares". Advances in Space Research 19, n.º 12 (janeiro de 1997): 1903–6. http://dx.doi.org/10.1016/s0273-1177(97)00098-7.

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Ripperda, B., M. Liska, K. Chatterjee, G. Musoke, A. A. Philippov, S. B. Markoff, A. Tchekhovskoy e Z. Younsi. "Black Hole Flares: Ejection of Accreted Magnetic Flux through 3D Plasmoid-mediated Reconnection". Astrophysical Journal Letters 924, n.º 2 (1 de janeiro de 2022): L32. http://dx.doi.org/10.3847/2041-8213/ac46a1.

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Abstract Magnetic reconnection can power bright, rapid flares originating from the inner magnetosphere of accreting black holes. We conduct extremely high-resolution (5376 × 2304 × 2304 cells) general-relativistic magnetohydrodynamics simulations, capturing plasmoid-mediated reconnection in a 3D magnetically arrested disk for the first time. We show that an equatorial, plasmoid-unstable current sheet forms in a transient, nonaxisymmetric, low-density magnetosphere within the inner few Schwarzschild radii. Magnetic flux bundles escape from the event horizon through reconnection at the universal plasmoid-mediated rate in this current sheet. The reconnection feeds on the highly magnetized plasma in the jets and heats the plasma that ends up trapped in flux bundles to temperatures proportional to the jet’s magnetization. The escaped flux bundles can complete a full orbit as low-density hot spots, consistent with Sgr A* observations by the GRAVITY interferometer. Reconnection near the horizon produces sufficiently energetic plasma to explain flares from accreting black holes, such as the TeV emission observed from M87. The drop in the mass accretion rate during the flare and the resulting low-density magnetosphere make it easier for very-high-energy photons produced by reconnection-accelerated particles to escape. The extreme-resolution results in a converged plasmoid-mediated reconnection rate that directly determines the timescales and properties of the flare.

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