Impulsive Plasma Research Articles

Hybrid Kinetic Modeling of the Magnetosheath Impulsive Plasma Cloud Penetration Through the Magnetopause and Comparison With MMS and Other Spacecraft Observations

AbstractThis research examines the plasma processes under penetration of the plasma clouds (plasmoids) across the magnetopause which is modeled as a tangential discontinuity (TD). Cases with the parallel magnetic field in both sides out of the TD are under investigation. Plasma parameters and magnetic field were chosen from the MMS mission and other spacecraft observations. The results are important for understanding the following basic space plasma physics problems: (a) plasma cloud deformation and strong phase mixing with magnetospheric plasma; (b) the transfer of mass, momentum and energy of magnetosheath and magnetic cloud plasma into magnetospheric plasmas; (c) necessary conditions for plasma cloud penetration via the magnetopause; (d) wave generation by plasma clouds inside the magnetopause.

Data-constrained Solar Modeling with GX Simulator

To facilitate the study of solar flares and active regions, we have created a modeling framework, the freely distributed GX Simulator IDL package, that combines 3D magnetic and plasma structures with thermal and nonthermal models of the chromosphere, transition region, and corona. Its object-based modular architecture, which runs on Windows, Mac, and Unix/Linux platforms, offers the ability to either import 3D density and temperature distribution models, or to assign numerically defined coronal or chromospheric temperatures and densities, or their distributions, to each individual voxel. GX Simulator can apply parametric heating models involving average properties of the magnetic field lines crossing a given voxel, as well as compute and investigate the spatial and spectral properties of radio, (sub)millimeter, EUV, and X-ray emissions calculated from the model, and quantitatively compare them with observations. The package includes a fully automatic model production pipeline that, based on minimal users input, downloads the required SDO/HMI vector magnetic field data, performs potential or nonlinear force-free field extrapolations, populates the magnetic field skeleton with parameterized heated plasma coronal models that assume either steady-state or impulsive plasma heating, and generates non-LTE density and temperature distribution models of the chromosphere that are constrained by photospheric measurements. The standardized models produced by this pipeline may be further customized through specialized IDL scripts, or a set of interactive tools provided by the graphical user interface. Here, we describe the GX Simulator framework and its applications.

RCM modeling of bubble injections into the inner magnetosphere: geosynchronous orbit and the ionospheric responses

Introduction: Accurate characterization of the plasma sheet source population in the ring current region and its outer boundary at geosynchronous orbit is crucial for understanding the dynamics of the Earth’s magnetosphere. The interaction between the ring current and plasma populations from the ionosphere is a focus of extensive research.Methods: We used the Rice Convection Model (RCM) to simulate the transient meso-scale injections of fast flows or plasma sheet bubbles from the outer boundary into the inner magnetosphere and the associated impacts on the ionosphere. We compared our simulation results of the average properties of bulk plasma access to geosynchronous orbit to a number of empirical models. We also examined the role of plasma sheet bubbles in forming field-aligned currents (FACs).Results: Our modeling results show that impulsive plasma sheet injections dramatically alter the average distribution of FACs in the ionosphere. We found both quantitative and qualitative agreements and disagreements when comparing our simulation results to empirical models. Furthermore, we demonstrated that several discrete auroral structures can be identified in the nightside ionosphere in accordance with theupward FACs.Discussion: The significance of plasma sheet bubbles in modifying the averageplasma properties at geosynchronous orbit and FACs in the ionosphere is highlighted by oursimulation findings, offering novel understandings into the dynamics of Earth's magnetosphere,and emphasizing the necessity for further research in this field.

3D MHD wave propagation near a coronal null point: New wave mode decomposition approach

Context. Ubiquitous vortex flows at the solar surface excite magnetohydrodynamic (MHD) waves that propagate to higher layers of the solar atmosphere. In the solar corona, these waves frequently encounter magnetic null points. The interaction of MHD waves with a coronal magnetic null in realistic 3D setups requires an appropriate wave identification method. Aims. We present a new MHD wave decomposition method that overcomes the limitations of existing wave identification methods. Our method allows for an investigation of the energy fluxes in different MHD modes at different locations of the solar atmosphere as waves generated by vortex flows travel through the solar atmosphere and pass near the magnetic null. Methods. We used the open-source MPI-AMRVAC code to simulate wave dynamics through a coronal null configuration. We applied a rotational wave driver at our bottom photospheric boundary to mimic vortex flows at the solar surface. To identify the wave energy fluxes associated with different MHD wave modes, we employed a wave decomposition method that is able to uniquely distinguish different MHD modes. Our proposed method utilizes the geometry of an individual magnetic field-line in the 3D space to separate the velocity perturbations associated with the three fundamental MHD waves. We compared our method with an existing wave decomposition method that uses magnetic flux surfaces instead. Over the selected flux surfaces, we calculated and analyzed the temporally averaged wave energy fluxes, as well as the acoustic and magnetic energy fluxes. Our wave decomposition method allowed us to estimate the relative strengths of individual MHD wave energy fluxes. Results. Our method for wave identification is consistent with previous flux-surface-based methods and provides the expected results in terms of the wave energy fluxes at various locations of the null configuration. We show that ubiquitous vortex flows excite MHD waves that contribute significantly to the Poynting flux in the solar corona. Alfvén wave energy flux accumulates on the fan surface and fast wave energy flux accumulates near the null point. There is a strong current density buildup at the spine and fan surface. Conclusions. The proposed method has advantages over previously utilized wave decomposition methods, since it may be employed in realistic simulations or magnetic extrapolations, as well as in real solar observations whenever the 3D fieldline shape is known. The essential characteristics of MHD wave propagation near a null – such as wave energy flux accumulation and current buildup at specific locations – translate to the more realistic setup presented here. The enhancement in energy flux associated with magneto-acoustic waves near nulls may have important implications in the formation of jets and impulsive plasma flows.

Evolution of Kelvin–Helmholtz Instability in the Fan-spine Topology

Abstract We use multiwavelength imaging observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory to study the evolution of the Kelvin–Helmholtz (K–H) instability in a fan-spine magnetic field configuration. This magnetic topology exists near an active region AR12297 and is rooted in a nearby sunspot. In this magnetic configuration, two layers of cool plasma flow in parallel and interact with each other inside an elongated spine. The slower plasma flow (5 km s−1) is the reflected stream along the spine’s field lines from the top, which interacts with the impulsive plasma upflows (114–144 km s−1) from below. This process generates a shear motion and subsequent evolution of the K–H instability. The amplitude and characteristic wavelength of the K–H unstable vortices increase, satisfying the criterion of the fastest-growing mode of this instability. We also describe how the velocity difference between two layers and the velocity of K–H unstable vortices are greater than the Alfvén speed in the second denser layer, which also satisfies the criterion of the growth of the K–H instability. In the presence of the magnetic field and sheared counterstreaming plasma as observed in the fan-spine topology, we estimate the parametric constant Λ ≥ 1, which confirms the dominance of velocity shear and the evolution of the linear phase of the K–H instability. This observation indicates that in the presence of complex magnetic field structuring and flows, the fan-spine configuration may evolve into rapid heating, while the connectivity changes due to the fragmentation via the K–H instability.

Particle Acceleration by Dense Impulsive Structures Moving in Ambient Magnetospheric Plasma. 3‐D Hybrid Kinetic Modeling and MMS Observations

AbstractHigh resolution observations of dense plasma impulsive structures moving through an ambient background magnetospheric flows were captured by the Magnetospheric Multiscale mission. The observations show particle heating and acceleration, shock‐like wave formation, and whistler wave excitation inside the interface between the dense impulsive plasma structures and the ambient plasma. A multiscale hybrid kinetic simulation provides an explanation of the observed wave‐particle interactions with the assumption that the dense plasma structures may be represented by plasma clouds which are formed at the magnetopause layer due to reconnection processes.

Origin of impulsive plasma outflows due to magnetoacoustic shocks

Origin of impulsive plasma outflows due to magnetoacoustic shocks

Oxidation and Biodecontamination Effects of Impulsive Discharges in Atmospheric Air

Chemical oxidation and the bactericidal capabilities of nonthermal plasma discharges can be used in different practical applications, such as biodecontamination, sterilisation of medical equipment, waste water treatment, syn-gas treatment, and others. In this paper, the oxidation and biodecontamination effects of impulsive plasma discharge, which propagate across a liquid sample/air interface (surface discharges), and through the bulk of a liquid sample (direct discharges), have been investigated. The oxidizing capability was analyzed by measuring the degree of decolorization of indigo carmine dye in water solutions. Gram-negative and gram-positive bacterias, E. coli and S. aureus , respectively, were used as model microorganisms in the investigation of the biocidal effects of plasma discharges. Surface and direct plasma discharges were generated by high-voltage impulses of both polarities, with the magnitudes of 20, 24, and 28 kV, and the chemical oxidation and biodecontamination capabilities of such discharges have been obtained and analyzed. It has been established that the defining factor in the chemical and biological effects of plasma discharges is the normalized delivered charge (dose). The results obtained in this paper show that surface discharges have greater biodecontamination capability as compared with direct transient plasma discharges. Also, it was shown that the decontamination rate of E. coli is more than double than that of S. aureus .

The role of ring current particle injections: Global simulations and Van Allen Probes observations during 17 March 2013 storm

We simulate substorm injections observed by the Van Allen Probes during the 17 March 2013 storm using a self‐consistent coupling between the ring current model RAM‐SCB and the global MHD model BATS‐R‐US. This is a significant advancement compared to previous studies that used artificially imposed electromagnetic field pulses to mimic substorm dipolarization and associated inductive electric field. Several substorm dipolarizations and injections are reproduced in the MHD model, in agreement with the timing of shape changes in the AE/AL index. The associated inductive electric field transports plasma sheet plasma to geostationary altitudes, providing the boundary plasma source to the ring current model. It is found that impulsive plasma sheet injections, together with a large‐scale convection electric field, are necessary to develop a strong ring current. Comparisons with Van Allen Probes observations show that our model reasonably well captures dispersed electron injections and the global Dst index.

Transient reconnection in the cusp during strongly negative IMFBy

We investigate transient magnetic reconnection (flux transfer events, FTEs) in the cusp and its ionospheric signatures. We present in situ observations by the Polar spacecraft of multiple impulsive plasma injections and related magnetopause crossings in the outer stagnant cusp of the northern hemisphere. At this time the interplanetary magnetic field (IMF) was northward, dominated by strongBy(−11 nT). Plasma injections are observed in the direction of the magnetic tension force due to the IMFByand resemble the “time of flight” energy‐latitude dispersion. Associated magnetopause crossings exhibit large magnetic field rotation (>150 degrees) and strong depression of the field magnitude (down to several percent of the value in the magnetosheath). We use conjugate observations from the Greenland magnetometer network and Sondrestrom incoherent scatter radar together with the Polar UV imager to show that the transient reconnection causes a direct response of cusp auroral brightness and ionospheric convection in the direction consistent with the IMFBypolarity. The observations, in space and on the ground, are consistent with a sequence of bulges launched by transient reconnection. We present a qualitative model of the bulge structure that is consistent with most of the Polar observations during the studied interval. Conjugate ground‐based observations provide additional evidence for transient reconnection and are consistent with the ground signature of FTEs.

Hybrid Simulation of Space Plasmas: Models with Massless Fluid Representation of Electrons. III. Shockless Discontinuities

This is the third article in a series of reviews on hybrid simulation of low-frequency processes in space plasmas. It deals with shockless (contact, tangential, and rotational) discontinuities. A hybrid model is described with ions represented by particles and electrons by a massless fluid. The Hamiltonian scheme for the numerical implementation of this model is discussed in detail. The first part of the article provides basic background information, which covers MHD models (ideal, resistive, and Hall models) as well as a classification of shockless discontinuities and their main properties. The review part of the article surveys the literature on simulation of the structure and properties of nonpropagating (contact and tangential) discontinuities and the structure of the magnetopause as a complex domain consisting of multiple discontinuities and waves. We also review the literature on hybrid simulation of rotational discontinuities and the structure of the reconnection layer—the configuration of the reconnecting magnetic forcelines in the dayside magnetopause and in the distant magnetotail. The concluding sections examine studies on hybrid simulation of the penetration of plasma inhomogeneities from the solar wind into the magnetosphere. The following issues are considered: the interaction of the bow shock with interplanetary discontinuities; the "hot flow anomaly"; the interaction of pressure pulses with the bow shock; impulsive plasma penetration through a tangential discontinuity (the magnetopause) as a result of a "collision" of a magnetosheath plasmoid (plasma current sheet) with the magnetopause.

Spectral-polarimetric measurements of the radiation of an impulsive plasma

This article presents the principles behind the recording of weak optical signals from an impulsive plasma with nanosecond time resolution. A detailed description is given of a method and equipment for high-speed recording and primary analysis of experimental data on the intensity of polarized radiation. A description is given of a spectral-polarimetric system designed for real-time diagnosis of impulsive and quasisteady plasmas. Results are presented from measurements of the radiation of a helium plasma from an impulsive high-voltage plasma-beam discharge. The performance characteristics of the diagnostic system are also evaluated.

Two‐dimensional hybrid simulations of impulsive plasma penetration through a tangential discontinuity

Two‐dimensional hybrid simulations with particle ions and fluid electrons are used to calculate the impulsive penetration process when a magnetosheath plasma irregularity interacts with the magnetopause. The irregularity is modeled as a field‐aligned filament with an excess density impinging on the magnetopause. Simulations with strictly parallel or antiparallel magnetic fields in the magnetosheath and in the magnetosphere are performed in order to investigate ion kinetic effects during the penetration of the plasma irregularity. The results show that a MHD approach is not appropriate when describing the impulsive penetration of small‐scale irregularities. If the fields in the magnetosheath and magnetosphere are antiparallel, the magnetic field gradient near the magnetopause boundary leads to an asymmetric propagation of the magnetosheath plasma filament. In contrast, for moderate field changes across the magnetopause the parallel case exhibits an almost straight‐line propagation of the filament, while its main part is focused into a small region. In both cases, twin vortices are set up in the magnetosphere due to the filament motion. In the antiparallel case the shape of the filament is totally distorted by these vortices; these fluidlike structures stretch the magnetopause boundary and thereby increase the line to surface ratio of the boundary layer. The filament breaks in the antiparallel as well as in the parallel case into smaller parts which leads to isolated islands of magnetosheath like plasma and field in the magnetosphere of the order of the ion gyroradius.

Signatures of transient boundary layer processes observed with Viking

Transient penetration of plasma with magnetosheath origin is frequently observed with the hot plasma experiment on board the Viking satellite at auroral latitudes in the dayside magnetosphere. The injected magnetosheath ions exhibit a characteristic pitch angle/energy dispersion pattern, earlier reported for solar wind ions accessing the magnetosphere in the cusp regions. In contrast to the continuous plasma entry in the cusp, the events discussed here show temporal features which suggest a connection to transient processes at or in the vicinity of the magnetospheric boundary. A single event study confirms previously published observations that the injected ions flow essentially tailward with a velocity comparable to the magnetosheath flow and that the energy spectra inferred for the source population resemble magnetosheath spectra. Those ion injection structures, which were resolved by the Viking mass spectrometer, consist of protons. Based on a statistical study, it is found that these events are predominantly observed around 0800 and 1600 MLT, in a region populated both by ring current/plasma sheet particles and by particles whose source is the magnetosheath plasma. Magnetic field line tracing based on the Tsyganenko magnetic field model yields a scatter of the source locations around the mid‐latitude region of the magnetospheric boundary. The probability for these events to occur is highest when the interplanetary magnetic field (IMF) is confined to the ecliptic plane. The event occurrence frequency shows a dawn‐dusk asymmetry depending on the azimuthal direction of the IMF. The occurrence frequency is independent of the solar wind velocity but increases with increasing solar wind pressure. For radially directed IMF the probability for observing the events is generally higher than for azimuthally directed IMF. The difference is especially pronounced during times when the solar wind pressure is comparatively low. Some of the most prominent events are obviously associated with significant changes in solar wind plasma density. The connection of the events to transient impulsive solar wind/magnetosphere interaction processes, such as transient reconnection (FTE), impulsive plasma transfer, Kelvin Helmholtz instabilities, and solar wind pressure pulses, is discussed. A relation with transient reconnection can be excluded.

Comment [on Owen and Cowley's “Analysis of impulsive plasma transport through the magnetopause”

Comment [on Owen and Cowley's “Analysis of impulsive plasma transport through the magnetopause”

Reply [to “Comment on Owen and Cowley's ‘Analysis of Impulsive plasma transport through the magnetopause’”

Reply [to “Comment on Owen and Cowley's ‘Analysis of Impulsive plasma transport through the magnetopause’”

Polarization of the impulsive signals observed in the nightside ionosphere of Venus

The impulsive plasma wave bursts detected by the Pioneer Venus Orbiter electric field detector in the nightside ionosphere of Venus have been attributed to atmospheric lightning. However, it has also been argued that the wave bursts are generated locally by plasma instabilities. The waves associated with local instabilities are most probably electrostatic in nature, while lightning‐generated waves should be whistler mode waves, at least at the lowest frequencies. It may be possible to identify the wave modes through analysis of the wave polarization. We show that for typical ionospheric parameters the whistler mode wave electric field should be polarized predominantly perpendicular to the ambient magnetic field. However, the signals are often impulsive in nature, with durations much less than the spacecraft spin period, and an individual wave event is likely to be aliased since the event may occur at arbitrary spin phase and arbitrary intensity. Statistical analysis of the wave polarization using data acquired in the third nightside periapsis season shows that the 100‐Hz data suffer from interference, which may be due to the interaction of the spacecraft with the ambient plasma. The interference is removed through visual inspection of the data, and we show that the 100‐Hz waves are polarized perpendicular to the ambient magnetic field provided we restrict the data to those intervals in which the magnetic field is sufficiently far from horizontal to allow vertical propagation within the whistler mode resonance cone. The 100‐Hz waves detected outside of the resonance cone are polarized parallel to the magnetic field, as are the waves at higher frequency. The waves consequently fall into two classes: whistler mode waves which are most likely due to atmospheric lightning, since the low phase speed of the whistler mode argues against an in situ instability, and a mode that is polarized parallel to the ambient field. This latter mode may be analogous to the anomalous parallel polarized wave fields detected in the terrestrial ionosphere above thunderstorms.

Heikkila's mechanism for impulsive plasma transport through the magnetopause: A reexamination

It has been proposed by Heikkila (1982) that the impact upon a magnetically “open” magnetopause current sheet of a “cloud” of magnetosheath plasma having excess momentum will result in the transport of the cloud through the sheet, forming a plasma boundary layer located on both open and closed flux tubes in the interior. A reexamination of Heikkila's work shows, however, that the argument which was used to arrive at that conclusion is not correct. The error arises from the assumption that the induction electric field which is associated with the perturbation of the current sheet will produce a flow which is just such as to cause the plasma to move with the sheet. This is not the case. The flow normal to the current sheet which is produced by the induction electric field alone will in general be less than the speed of the sheet itself, continuity being maintained by flows directed along the perturbed current layer. If we then assume, with Heikkila, that the induction electric field component which is parallel to the magnetic field component which threads the “open” magnetopause is cancelled to zero by a curl‐free charge‐separation electric field, then the tangential electric field and normal flow are indeed increased, as argued by Heikkila, but only to the point where the flow just matches the speed of the boundary, and not to a speed which is in excess of the latter, as claimed. Heikkila's mechanism does not therefore lead to “impulsive transport” of magnetosheath plasma through the boundary onto open and closed magnetospheric flux tubes in the interior. These statements concerning the relationship between the plasma flow and the motion of the boundary refer explicitly to a formulation of the problem, consistent with Heikkila's discussion, in which (1) E.B is taken to be zero everywhere, (2) the reconnection‐associated electric field is zero (or is transformed to zero by a deHoffman‐Teller transformation), (3) the plasma motion is taken to be the sum of a field‐aligned motion and E×B drift, and (4) the plasma flow streamlines are taken to lie in planes transverse to the magnetic field component which reverses across the current sheet. However, plasma motions directed along the magnetic field can be added arbitrarily to these flows, so that plasma can indeed cross the boundary in either direction, but only by flow along the open field lines. Consequently, magnetosheath plasma can indeed flow through the open magnetopause to form a boundary layer inside the magnetosphere, but this layer will be confined to open flux tubes adjacent to the boundary as in reconnection models. Boundary layers are not formed on adjacent closed flux tubes by these means. Our purpose here is not to dispute the experimental evidence which indicates that boundary layers are sometimes formed on closed flux tubes, but only to point out that Heikkila's argument does not provide a valid mechanism which leads to their formation.

Impulsive plasma waves observed by DE-1 in the magnetosphere

Impulsive plasma waves (1–9 kHz) with durations less than 100 msec have been found in DE-1 wide-band electric field data (650 Hz – 40 kHz) received at Kashima, Japan. The waves are associated with a strong narrow-band ELF hiss, and were observed at geocentric distances from 3.1 to 4.9 Re (earth's radius) in the low-latitude nightside magnetosphere. Local electron densities and plasmapause locations estimated suggest that the waves were observed outside the nightside plasmapause. The waves are discussed in terms of Landau resonant trapping of magnetospheric electrons by the associated whistler-mode ELF hiss.

Impulsive plasma waves observed by DE 1 in nightside magnetosphere

Impulsive plasma waves with a frequency range of 1–9 kHz were found in the wide‐band electric field data (650 Hz to 10 kHz) from the DE 1 satellite received at the Kashima station in Japan. The impulsive plasma waves were often accompanied by a strong hiss band at about 1 kHz, but not by a chorus. The frequency‐time spectra of these waves are very similar to those of electrostatic bursts associated with ELF chorus in the outer dayside magnetosphere, but these impulsive waves were observed at low geomagnetic latitudes in nightside magnetospheric regions much nearer the Earth for geomagnetic quiet and disturbed times. Local plasma densities (∼1 cm−3) obtained from the characteristic frequency of VLF emissions associated with the impulsive plasma waves agree with those observed simultaneously by the DE 1 retarding ion mass spectrometer. It is inferred from the local plasma density and the empirical relation of the plasmapause position with Kp that the impulsive plasma waves are occurring just outside the plasmapause. The impulsive plasma waves are discussed in terms of a resistive medium instability caused by Landau resonant trapping of thermal electrons by the associated hiss band at about 1 kHz, since this mechanism seems to be plausible from the available data and the frequency‐time spectra are similar to electrostatic bursts identified previously. Some of the events do not seem to have a strong ELF hiss band accompanying the impulsive plasma waves. It is suggested that these events may be due to electrons bunched by an ELF hiss band in a nearby region or may be caused by space discharges in the vicinity of the long‐wire antenna on the DE 1 spacecraft.