Plasma Outflow Research Articles

SynCOM: An Empirical Model for High-resolution Simulations of Transient Solar Wind Flows

The Synthetic Corona Outflow Model (SynCOM), an empirical model, simulates the solar corona’s dynamics to match high-resolution observations, providing a useful resource for testing velocity measurement algorithms. SynCOM generates synthetic images depicting radial variability in total brightness and includes stochastic elements for plasma outflows and instrumental noise. It employs a predefined probability distribution for flow velocity and an adjustable signal-to-noise ratio to evaluate different data analysis methods for coronal flows. By adjusting parameters to match specific coronal and instrumental conditions, SynCOM offers a platform to assess these methods for determining coronal velocity and acceleration. Validating these measurements would help us to understand the origins of the solar wind and support missions such as the Polarimeter to Unify the Corona and Heliosphere (PUNCH). In this study, we demonstrate how SynCOM can be employed to assess the precision and performance of two different flow-tracking methods. By providing a ground truth based on observational data, we highlight the importance of SynCOM in confirming observational standards for detecting coronal flows.

Investigation of the poloidal magnetic flux at the PF-3 plasma focus within the framework of the program of laboratory simulation of astrophysical jets

Astrophysical jets are collimated plasma outflows observed in diverse astrophysical settings covering seven decades of spatial scale and twenty decades of power, which, nevertheless, share many common features. This similarity over wide range of scales indicates a common core of physics underlying this phenomenon, leading to considerable interest in observational, theoretical and numerical studies. Laboratory astrophysics experiments for simulating astrophysical jets are premised on this common core of physics responsible for multi-scale similarity of jets remaining valid down to laboratory spatial scales of millimeters. Jets formed after the disassembly of the non-cylindrical z-pinch formed in a plasma focus installation have recently been subjects of observational studies. They offer an important complementarity to the main lines of investigations in two respects. Firstly, the multi-faceted role of gravity, radiation, nuclear reactions and related astrophysics is eliminated retaining only a rapid implosion of a compact plasma object in a magnetohydrodynamic environment as a common feature. Secondly, observations can be made using techniques of laboratory plasma diagnostics. In this paper, we report preliminary results regarding presence of poloidal magnetic flux associated with the jets lasting long after the pinch disassembly. This is significant in the context of uncertainty regarding the origin of poloidal magnetic field postulated in several MHD models of astrophysical jet phenomena. Evidence indicating presence of a radial component of electric field suggests existence of plasma rotation as well. These results suggest that more refined experiments can provide insights into the astrophysical jetting phenomena not available from observational astronomy techniques.

Numerical Experiment on the Influence of Granulation-induced Waves on Solar Chromosphere Heating and Plasma Outflows in a Magnetic Arcade

This paper offers a fresh perspective on solar chromosphere heating and plasma outflows, focusing on the contribution of waves generated by solar granulation. Utilizing a 2.5D numerical experiment for the partially ionized lower solar atmosphere, we investigate the dissipation of these waves and their impact on plasma outflows and chromospheric heating via ion-neutral collisions. Employing the JOint ANalytical and Numerical Approach code, we adopt two-fluid model equations, examining partially ionized hydrogen plasma dynamics, including protons+electrons and neutrals, treated as two separate fluids that are coupled through ion-neutral collisions. Our investigation focuses on a quiet solar chromosphere region characterized by gravitational stratification and magnetic confinement by an initially set single magnetic arcade. The primary source of the waves is the solar convection beneath the photosphere. Our results demonstrate that ion-neutral collisions result in the dissipation of such waves, releasing thermal energy that heats the chromosphere plasma. Notably, this is accompanied by upward-directed plasma flows. Finally, we conclude that wave dissipation due to ion-neutral collisions in the two-fluid plasma model induces chromosphere heating and plasma outflows.

Galactic outflows in different geometries

In the gravitational potential well of a galaxy, the behavior of outflows has been studied in different geometries i.e. constant flux tube, divergent and extreme divergent environments. First of all, we describe the hydrodynamic model by which we approach the outflows system. This model treats all the waves as fluids and applies fluid mechanics to them(cosmic rays, thermal plasma & Alfvén wave). Whereas outflows mean the gas regime above and below the center of the galactic disk, and we have taken it as a system where interaction between cosmic rays and plasma occurs. After discussing the hydrodynamic three-fluid model, we define three geometrical structures which can be acquired by outflows and relate these structures with thermal plasma, cosmic and Alfvén waves pressures, thus seeking for its behavior. The solution of the system is categorically divided into three branches, supersonic, subsonic and unphysical solutions.The most interesting of all is the transonic solution, a solution that evolves from subsonic to supersonic. First of all, we discuss only thermal plasma outflows and explain their evolution in three cases of outflows environments, followed by the addition of cosmic waves and Alfvén waves. After discussing three fluid outflows in different structures, we compared the results of thermal outflows with three fluid outflows and see how the addition of waves in the system affects the dynamics of the system. At last, the findings of this paper are discussed.

Direct Imaging of a Prolonged Plasma/Current Sheet and Quasiperiodic Magnetic Reconnection on the Sun

Magnetic reconnection is widely believed to be the fundamental process in the solar atmosphere that underlies magnetic energy release and particle acceleration. This process is responsible for the onset of solar flares, coronal mass ejections, and other explosive events (e.g., jets). Here, we report direct imaging of a prolonged plasma/current sheet along with quasiperiodic magnetic reconnection in the solar corona using ultra-high-resolution observations from the 1.6 m Goode Solar Telescope at the Big Bear Solar Observatory and the Solar Dynamics Observatory/Atmospheric Imaging Assembly. The current sheet appeared near a null point in the fan–spine topology and persisted over an extended period (≈20 hr). The length and apparent width of the current sheet were about 6″ and 2″, respectively, and the plasma temperature was ≈10–20 MK. We observed quasiperiodic plasma inflows and outflows (bidirectional jets with plasmoids) at the reconnection site/current sheet. Furthermore, quasiperiodic reconnection at the long-lasting current sheet produced recurrent eruptions (small flares and jets) and contributed significantly to the recurrent impulsive heating of the active region. Direct imaging of a plasma/current sheet and recurrent null-point reconnection for such an extended period has not been reported previously. These unprecedented observations provide compelling evidence that supports the universal model for solar eruptions (i.e., the breakout model) and have implications for impulsive heating of active regions by recurrent reconnection near null points. The prolonged and sustained reconnection for about 20 hr at the breakout current sheet provides new insights into the dynamics and energy release processes in the solar corona.

Influence of electrons on granulation-generated solar chromosphere heating and plasma outflows

Context. It is known that the solar atmosphere exhibits a varying degree of ionization through its different layers. The ionization degree directly depends on plasma temperature, that is, the lower the temperature, the lower the ionization degree. As a result, the plasma in the lower atmospheric layers (the photosphere and the chromosphere) is only partially ionized, which motivates the use of a three-fluid model. Aims. We consider, for the first time, the influence of electrons on granulation-generated solar chromosphere heating and plasma outflows. We attempt to detect variations in the ion temperature and plasma up- and downflows. Methods. We performed 2.5D numerical simulations of the generation and evolution of granulation-generated waves, flows, and other granulation-associated phenomena with an adapted JOANNA code. This code solves the simplified three-fluid equations for ions (protons) and electrons and neutrals (hydrogen atoms) that are coupled by collision forces. Results. Electron-neutral and electron–ion collisions provide extra heat in the low chromosphere and enhance plasma outflows in this region. The effect of electrons is small compared to ion–neutral collisions, which have a significantly greater effect on the heating process and the production of outflows. Ion–neutral collisions involve higher energy exchanges, making them the dominant mechanism over collisions with electrons. Conclusions. Electrons do not play a major role in heating and producing outflows, primarily because their mass is much lower compared to that of neutrals and ions, resulting in lower energy transfer during collisions.

Periods and Frequency Drifts of Groups of the Decimetric Spikes in Two Solar Flares

We studied the radio emission occurring as narrowband decimetric spikes observed during the 10 May 2022 and 26 August 2022 flares. In the radio spectra, these spikes were distributed in groups that occurred quasi-periodically with the periods 5.1 s in the 10 May 2022 flare and 9.1 s in the 26 August 2022 flare. In some parts of these groups, even subgroups of spikes distributed with the quasi-periods of 0.19 s (10 May 2022 flare), and 0.17 s and 0.21 s (26 August 2022 flare) were found. Some of these subgroups even drifted to higher or lower frequencies, which was observed for the first time. At the time of the dm-spikes observation, a pair of reconnecting loops are identified in the SDO/AIA EUV observations of the 10 May 2022 flare, one of which is interpreted as belonging to a small erupting filament. We propose that these loops reconnect in the dynamic quasi-periodic regime (the period 0.19 s) and this reconnection is modulated by an oscillation of one of the interacting loops (the period 5.1 s). Accelerated electrons from this process are trapped in reconnecting plasma outflows, and thus the drifting groups of spikes are generated. The 26 August 2022 flare is a complex event with several systems of bright loops; nevertheless, it also shows a disintegrating erupting filament similar to the 10 May 2022 flare, meaning that the dm-spikes are likely generated by similar reconnection processes.

The role of an in-plane electric field during the merging formation of spherical tokamak plasmas

Axial merging of two torus plasmas is utilized as a center-solenoid free start-up scheme for a high-beta spherical tokamak (ST) plasma, in which magnetic reconnection under a strong guide field plays dominant roles in energy conversion and equilibrium formation. The ion heating source in magnetic reconnection is the plasma outflow with E×B drift velocity in the downstream region where the reconnected field lines flow out. Since the inductive reconnection electric field is almost parallel to the magnetic field, particularly in the inboard-side downstream region of magnetic reconnection under a strong guide field, a large electrostatic field in the poloidal plane is spontaneously formed to sustain steady plasma outflow motion in the downstream region. In ST plasma merging experiments, the self-generated electrostatic field in the downstream region does not always balance with the inductive electric field to make the total electric field strictly perpendicular to the total magnetic field. The excess electrostatic field will provide an even faster outflow plasma velocity than the magnetic field line motion and a quick reversal of the toroidal plasma current to form convex flux surfaces.

Decoding the Nature of Coherent Radio Emission in Pulsars I: Observational Constraints

Radio observations from normal pulsars indicate that the coherent radio emission is excited by curvature radiation from charge bunches. In this review, we provide a systematic description of the various observational constraints on the radio emission mechanism. We have discussed the presence of highly polarized time samples where the polarization position angle follow two orthogonal well-defined tracks across the profile that closely match the rotating vector model in an identical manner. The observations also show the presence of circular polarization, with both the right and left handed circular polarization seen across the profile. Other constraints on the emission mechanism are provided by the detailed measurements of the spectral index variation across the profile window, where the central part of the profile, corresponding to the core component, has a steeper spectrum than the surrounding cones. Finally, the detailed measurements of the subpulse drifting behaviour can be explained by considering the presence of non-dipolar field on the stellar surface and the formation of the partially screened gap (PSG) above the polar cap region. The PSG gives rise to a non-stationary plasma flow that has a multi-component nature, consisting of highly energetic primary particles, secondary pair plasma, and iron ions discharged from the surface, with large fragmentation resulting in dense plasma clouds and lower-density inter-cloud regions. The physical properties of the outflowing plasma and the observational constraints lead us to consider coherent curvature radiation as the most viable explanation for the emission mechanism in normal pulsars, where propagation effects due to adiabatic walking and refraction are largely inconsequential.

X-Rays from a Central “Exhaust Vent” of the Galactic Center Chimney

Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of linear X-ray-emitting features located within the southern portion of the Galactic center chimney and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.°08, b = −1.°42. The surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology, which may have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma components, possibly a sign of shock compression or heating of the interstellar medium by outflowing material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a sequence of accretion events onto the Galactic black hole may be a plausible quasi-continuous energy source to sustain the observed morphology.

Formation of Fan-spine Magnetic Topology through Flux Emergence and Subsequent Jet Production

Fan-spine magnetic structure, as a fundamental three-dimensional topology in magnetic reconnection theory, plays a crucial role in producing solar jets. However, how fan-spine configurations form in the solar atmosphere remains elusive. Using the Chinese Hα Solar Explorer (CHASE) and the Solar Dynamics Observatory, we present a case study on the complete buildup of fan-spine topology driven by flux emergence and the subsequent jet production. Two fan-spine structures and the two associated null points are present. Variations in null-point heights and locations were tracked over time during flux emergence. The north fan-spine structure is found to be created through magnetic reconnection between the newly emerged flux and the background field. Gentle reconnection persistently occurs after formation of the north fan-spine structure, resulting in weak plasma outflows. Subsequently, as flux emergence and magnetic helicity injection continue, the formation and eruption of minifilaments after reconnection at the quasi-separatrix layer between the two nulls trigger three homologous jets. The CHASE observations reveal that the circular flare ribbon, inner bright patch, and remote brightening all exhibit redshifted signatures during these jet ejections. This work unveils the key role of flux emergence in the formation of fan-spine topology, and highlights the importance of minifilaments for subsequent jet production.

Impulsively generated waves in two-fluid plasma in the solar chromosphere: Heating and generation of plasma outflows

Context. We present new insights into impulsively generated Alfvén and magneto-acoustic waves in the partially ionized two-fluid plasma of the solar atmosphere and their contribution to chromospheric heating and plasma outflows. Aims. Our study attempts to elucidate the mechanisms responsible for chromospheric heating and excitation of plasma outflows that may contribute to the generation of the solar wind in the upper atmospheric layers. The main aim of this work is to investigate the impulsively generated waves by taking into account two-fluid effects. These effects may alter the wave propagation leading to attenuation and collisional plasma heating. Methods. The two-fluid equations were solved by the JOint ANalytical Numerical Approach (JOANNA) code in a 2.5-dimensional (2.5D) framework to simulate the dynamics of the solar atmosphere. Here, electrons + ions (protons) and neutrals (hydrogen atoms) are treated as separate fluids, which are coupled via ion-neutral collisions. The latter acts as a dissipation mechanism for the energy carried by the waves in two-fluid plasma and may ultimately lead to the frictional heating of the partially ionized plasma. The waves in two-fluid plasma, which are launched from the top of the photosphere, are excited by perturbations induced by localized Gaussian pulses in the horizontal components of the ion and neutral velocities. Results. In the middle and upper chromosphere, a substantial fraction of the energy carried by large amplitude waves in the two-fluid plasma is dissipated in ion-neutral collisions, resulting in the thermalization of wave energy and generation of plasma outflows. We find that coupled Alfvén and magneto-acoustic waves are more effective in heating the chromosphere than magneto-acoustic waves. Conclusions. Large-amplitude waves in the two-fluid plasma may be responsible for heating the chromosphere. The net flow of ions is directed outward, leading to plasma outflows in the lower solar corona, which may contribute to the solar wind at higher altitudes The primary source of wave energy dissipation in the current paradigm comes from collisions between ions and neutrals.

Relativistic shocks in conductive media

Context. Relativistic shocks are present in all high-energy astrophysical processes involving relativistic plasma outflows interacting with their ambient medium. While they are well understood in the context of relativistic hydrodynamics and ideal magnetohydrodynamics (MHD), there is a limited understanding of the properties related to their propagation in media characterized by finite electrical conductivity. Aims. This work presents a systematic method for the derivation and solution of the jump conditions for relativistic shocks propagating in MHD media with finite electrical conductivity. This method is applied to the numerical solution of the Riemann problem and the determination of the conditions inside the blastwave that is formed when ultrarelativistic magnetized ejecta interact with the circumburst medium during a gamma-ray burst. Methods. We derived the covariant relations expressing the jump conditions in a frame-independent manner. The resulting algebraic equations expressing the Rankine-Hugoniot conditions in the propagation medium’s frame were then solved numerically. A variable adiabatic index equation of state was used in order to obtain a realistic description of the post-shock fluid’s thermodynamics. This method was then employed for the solution of the Riemann problem for the case of a forward and a reverse shock, both of which form during the interaction of a gamma-ray burst ejecta with the circumburst medium. This allowed us to determine the kinematics of the resulting blastwave and the dynamical conditions in its interior. Results. Our solutions clearly depict the impact of the plasma’s electrical conductivity in the properties of the post-shock medium. Two characteristic regimes are identified with respect to the value of a dimensionless parameter that has a linear dependence on the conductivity. For small values of this parameter, the shock affects only the hydrodynamic properties of the propagation medium and leaves its electromagnetic field unaffected. No current layer forms in the shock front; thus, we refer to this as the current-free regime. For large values of this parameter, the ideal MHD regime has been retrieved. We also show that the assumption of a finite electrical conductivity can lead to higher efficiencies in the conversion of the ejecta energy into thermal energy of the blastwave through the reverse shock. The theory developed in this work can be applied to the construction of Riemann solvers for resistive relativistic MHD (RR4MHD).

Observation of Interchange Reconnection on Mars

Without a global dipole magnetic field, Mars has magnetic anomalies, i.e., crustal fields, in the southern hemisphere and interesting flexible magnetic fields in the magnetotail. The magnetic field topology is complex and flexible in the Martian magnetotail, especially over regions of strong crustal fields. However, the answer to how the magnetic field topology within crustal field regions transitions is elusive. Here we report the first case of interchange reconnection between open and closed crustal fields in the near-Mars magnetotail, using Mars Atmosphere and Volatile Evolution (MAVEN) observations. While MAVEN crossed from a region of closed crustal field to one of open crustal field, several characteristics of reconnection, such as the Hall magnetic field and plasma outflow, were observed. And plasmas are exchanged in the reconnection region. Our observations demonstrate that interchange reconnection can occur between open and closed crustal fields in the Martian near-magnetotail. Interchange reconnection occurring on the nightside changes the magnetic field topology within the crustal field regions and contributes to the escape of heavy ions.

Jovian Magnetospheric Injections Observed by the Hubble Space Telescope and Juno

AbstractWe compare Hubble Space Telescope observations of Jupiter's FUV auroras with contemporaneous conjugate Juno in situ observations in the equatorial middle magnetosphere of Jupiter. We show that bright patches on and equatorward of the main emission are associated with hot plasma injections driven by ongoing active magnetospheric convection. During the interval that Juno crossed the magnetic field lines threading the complex of auroral patches, a series of energetic particle injection signatures were observed, and immediately prior, the plasma data exhibited flux tube interchange events indicating ongoing convection. This presents the first direct evidence that auroral morphology previously termed “strong injections” is indeed a manifestation of magnetospheric injections, and that this morphology indicates that Jupiter's magnetosphere is undergoing an interval of active iogenic plasma outflow.

Ensemble Forecasts of Solar Wind Connectivity to 1 Rs Using ADAPT‐WSA

AbstractThe solar wind which arrives at any location in the solar system is, in principle, relatable to the outflow of solar plasma from a single source location. This source location, itself usually being part of a larger coronal hole, is traceable to 1 RS along the Sun's magnetic field, in which the entire path from 1 RS to a location in the heliosphere is referred to as the solar wind connectivity. While not directly measurable, the connectivity between the near‐Earth solar wind is of particular importance to space weather. The solar wind solar source region can be obtained by leveraging near‐sun magnetic field models and a model of the interplanetary solar wind. In this article, we present a method for making an ensemble forecast of the connectivity presented as a probability distribution obtained from a weighted collection of individual forecasts from the combined Air Force Data Assimilative Photospheric Flux Transport‐Wang Sheeley Arge (ADAPT‐WSA) model. The ADAPT model derives the photospheric magnetic field from synchronic magnetogram data, using flux transport physics and ongoing data assimilation processes. The WSA model uses a coupled set of potential field type models to derive the coronal magnetic field, and an empirical relationship to derive the terminal solar wind speed observed at Earth. Our method produces an arbitrary 2D probability distribution capable of reflecting complex source configurations with minimal assumptions about the distribution structure, prepared in a computationally efficient manner.

Self-similar Outflows at the Source of the Fast Solar Wind: A Smoking Gun of Multiscale Impulsive Reconnection?

We present results of a quantitative analysis of structured plasma outflows above a polar coronal hole observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) spacecraft. In a 6 hr interval of continuous high-cadence SDO/AIA images, we identified more than 2300 episodes of small-scale plasma flows in the polar corona. The mean upward flow speed measured by the surfing transform technique is estimated to be 122 ± 34 km s−1, which is comparable to the local sound speed. The typical recurrence period of the flow episodes is 10–30 minutes, and the mean duration and transverse size of each episode are about 3–5 minutes and 3–4 Mm, respectively. The largest identifiable episodes last for tens of minutes and reach widths up to 40 Mm. For the first time, we demonstrate that the polar coronal-hole outflows obey a family of power-law probability distributions characteristic of impulsive interchange magnetic reconnection. Turbulent photospheric driving may play a crucial role in releasing magnetically confined plasma onto open field. The estimated occurrence rate of the detected self-similar coronal outflows is sufficient for them to make a dominant contribution to the fast-wind mass and energy fluxes and to account for the wind’s small-scale structure.

On the triple pulsar profiles generated by ordinary mode

ABSTRACT A detailed study of the refraction of an ordinary wave in the magnetosphere of radio pulsars was carried out. For this, a consistent theory of the generation of secondary particles was constructed, which essentially takes into account the dependence of the number density and the energy spectrum of secondary particles on the distance from the magnetic axis. This made it possible to determine with high accuracy the refraction of the ordinary O-mode in the central region of the outflowing plasma, which makes it possible to explain the central peak of three-humped mean radio profiles. As shown by detailed numerical calculations, in most cases it is possible to reproduce quite well the observed mean profiles of radio pulsars.

Turbulence in Sources of Decimetric Flare Continua

Decimetric continua are commonly observed during long-lasting solar flares. Their frequency boundaries vary with time. We studied frequency boundary variations using the power spectrum analysis. Analyzing five decimetric continua, we found that their power spectra have a power-law form with the power-law index close to the Kolmogorov turbulence index −5/3. The same power index was also found in the power spectra of radio flux variations at frequencies in the range of the frequency boundary variations. Moreover, these frequency boundary variations were highly correlated with the radio flux ones. We interpret these results to be due to turbulent density variations in the reconnection plasma outflow to the termination shock formed above flare loops. In three cases of decimetric continua, we estimated the level of the plasma density turbulence to be 7.6 – 11.2% of the mean plasma density. We think that the analysis of variations of decimetric continua can be used in studies of the plasma turbulence in solar flares.

The Outflow and Recirculation of Ionospheric Plasma

The Outflow and Recirculation of Ionospheric Plasma