Plasma Void Research Articles

Three‐Dimensional Electrostatic Hybrid Particle‐In‐Cell Simulations of the Plasma Mini‐Wake Near a Lunar Polar Crater

AbstractLunar polar region has become the focus of future explorations due to the possible ice reservoir in the permanently shadowed craters. However, the space environment near the polar crater is quite complicated, and a plasma mini‐wake can be caused by the topographic obstruction. So far, three‐dimensional (3D) numerical simulations of the mini‐wake around a crater far larger than the Debye length are still limited. Here we present a 3D electrostatic hybrid particle‐in‐cell model to study the plasma mini‐wake of a polar crater on scale of about 1 km. It is found that the mini‐wake can begin upstream from the crater with a cone angle of about 8.8°. There is a plasma void with extra electrons near the leeward crater wall, where the electric potential can be as low as −60 V. A part of solar wind ions can be diverted into the crater, and the ratio of the diverted flux is about 4% on the crater bottom and about 18% on the windward crater wall, which provide an important source for the surface sputtering. Further studies show that the mini‐wake can change with the solar wind parameters and the crater shapes. Our results are helpful to assess the space environment and the water loss rate of a polar crater, and have general implications in studying the plasma mini‐wake caused by a crater on the other airless bodies.

Nightside Ionospheric Structure and Composition on Mars Driven by Energetic Electron Precipitation

Ionospheric chemistry plays an unexpectedly important role in the evolution of planetary habitability. This study is dedicated to a detailed modeling of the nightside Martian ionospheric structure and composition, a topic that has been poorly explored due to the absence of relevant measurements, but now becomes tractable owing to the unprecedented measurements made by the Mars Atmosphere and Volatile Evolution. Two-stream kinetic calculations and time-dependent fluid calculations are coupled to derive the nightside density profiles at 100–300 km for a large number of ion species, assuming solar wind electron precipitation as the only viable ionizing source in the ideal nonmagnetized atmosphere. Our calculations indicate the presence of a well-defined ionospheric peak at 146 km with a peak density of 8500 cm−3, as driven by the strong atmospheric “absorption” of precipitating electrons at low altitudes. The distribution of nonterminal species is roughly under chemical equilibrium below 170 km, whereas for terminal species such as NO+ and HCO+, diffusion is effective at essentially all altitudes, in direct contrast to the dayside behavior. In the more realistic magnetized atmosphere, the ionospheric peak seldom exists due to the patchiness of electron precipitation. In particular, our model results agree fairly well with the MAVEN measurements, especially in view of the coincidence between electron depletion and thermal plasma void seen along many MAVEN orbits. Compared to the dayside, the nightside ionospheric composition has a much higher proportion of NO+ and lower proportion of CO2 +, likely indicative of nightside enhancement of atmospheric O and N.

Modeling the Lunar Wake Response to a CME Using a Hybrid PIC Model

Abstract In the solar wind, a low-density wake region forms downstream of the nightside lunar surface. In this study, we use a series of 3D hybrid particle-in-cell simulations to model the response of the lunar wake to a passing coronal mass ejection (CME). Average plasma parameters are derived from the Wind spacecraft located at 1 au during three distinct phases of a passing halo (Earth-directed) CME on 2015 June 22. Each set of plasma parameters, representing the shock/plasma sheath, a magnetic cloud, and plasma conditions we call the mid-CME phase, are used as the time-static upstream boundary conditions for three separate simulations. These simulation results are then compared with results that use nominal solar wind conditions. Results show a shortened plasma void compared to nominal conditions and a distinctive rarefaction cone originating from the terminator during the CME’s plasma sheath phase, while a highly elongated plasma void reforms during the magnetic cloud and mid-CME phases. Developments of electric and magnetic field intensification are also observed during the plasma sheath phase along the central wake, while electrostatic turbulence dominates along the plasma void boundaries and 2–3 lunar radii R M downstream in the central wake during the magnetic cloud and mid-CME phases. The simulations demonstrate that the lunar wake responds in a dynamic way with the changes in the upstream solar wind during a CME.

Distribution of charged lunar dust in the south polar region of the moon

Lunar dust is one of the most threatening problems confronting the return of human beings to the moon. In this work we studied the spatial distribution behavior of charged lunar dust in the solar wind plasma environment in the south polar region of the moon and considered the influence of a mini-crater using Spacecraft Plasma Interactions Software. The distribution of dust and plasma at low solar altitude angles of 20° and 0° was studied, and the spatial density of lunar dust was ∼ 1010.4 m−3 and ∼ 1011.5 m−3, respectively. This is because a higher surface potential will result in transportation of small dust particles and photoelectrons can also neutralize positively charged lunar dust. The dust density in the plasma void region created by a mini-crater with a 5 m high wall was studied. We obtained a quasi-neutral electric environment in the plasma void region of the mini-crater, and the dust density was about a magnitude lower than that in other regions. The dust risk to a spacesuit is much lower on the nightside than on the dayside, but there is severe charged lunar dust transport in the region between light and shade, which is dominated by the difference in surface and plasma potential caused by photoelectrons.

Thermodynamic Evolution of Solar Flare Supra-arcade Downflows

Abstract Solar flares are rapid energy release phenomena that appear as bright ribbons in the chromosphere and high temperature loops in the corona, respectively. Supra-arcade Downflows (SADs) are plasma voids that first come out above the flare loops and then move quickly toward the flare loop top during the decay phase of the flare. In our work, we study 20 SADs appearing in three flares. By differential emission measure (DEM) analysis, we calculate the DEM weighted average temperature and emission measure of the front region and the main body of SADs. It is found that the temperatures of the SAD front and body tend to increase during the course of SADs flowing downwards. The relationship between the pressure and temperature fits well with the adiabatic equation for both the SAD front and body, suggesting that the heating of SADs is mainly caused by adiabatic compression. Moreover, we also estimate the velocities of SADs via the Fourier Local Correlation Tracking method and find that increase of the temperature of the SAD front presents a correlation with the decrease of the SAD kinetic energy, while the SAD body does not, implying that the viscous process may also heat the SAD front in spite of a limited role.

Application of spatially hybrid fluid–kinetic neutral model on JET L-mode plasmas

Abstract We present a spatially hybrid fluid–kinetic neutral model that consists of a fluid model for the hydrogen atoms in the plasma grid region coupled to a kinetic model for atoms sampled at the plasma–void interfaces and a fully kinetic model for the hydrogen molecules. The atoms resulting from molecular dissociation are either treated kinetically (approach 1) or are incorporated in the fluid model (approach 2). For a low-density JET L-mode case, the hybrid method reduces the maximum fluid–kinetic discrepancies for the divertor strike-point electron densities and electron temperatures from approximately 150% to approximately 20% for approach 1 and to approximately 40% for approach 2. Although the simulations with purely fluid neutral model become more accurate for increasing upstream plasma density, we still observe a significant improvement by using the hybrid approach. When consuming the same CPU time in averaging the electron strike-point densities and temperatures over multiple iterations as for the simulations with fully kinetic neutrals, hybrid approach 1 reduces the statistical error with on average a factor 2.5. Hybrid approach 2 further increases this factor to approximately 3.3, at the expense of accuracy.

Multiscale electronic and thermomechanical dynamics in ultrafast nanoscale laser structuring of bulk fused silica

We describe the evolution of ultrafast-laser-excited bulk fused silica over the entire relaxation range in one-dimensional geometries fixed by non-diffractive beams. Irradiation drives local embedded modifications of the refractive index in the form of index increase in densified glass or in the form of nanoscale voids. A dual spectroscopic and imaging investigation procedure is proposed, coupling electronic excitation and thermodynamic relaxation. Specific sub-ps and ns plasma decay times are respectively correlated to these index-related electronic and thermomechanical transformations. For the void formation stages, based on time-resolved spectral imaging, we first observe a dense transient plasma phase that departs from the case of a rarefied gas, and we indicate achievable temperatures in the excited matter in the 4,000–5,500 K range, extending for tens of ns. High-resolution speckle-free microscopy is then used to image optical signatures associated to structural transformations until the evolution stops. Multiscale imaging indicates characteristic timescales for plasma decay, heat diffusion, and void cavitation, pointing out key mechanisms of material transformation on the nanoscale in a range of processing conditions. If glass densification is driven by sub-ps electronic decay, for nanoscale structuring we advocate the passage through a long-living dense ionized phase that decomposes on tens of ns, triggering cavitation.

Plasma creatinine and oxidative stress biomarkers in amyotrophic lateral sclerosis

Objective: To determine the associations between plasma creatinine (PCr), plasma uric acid (PUA), and urinary oxidative stress (OS) biomarkers with the ALSFRS-R at baseline and survival in a large epidemiological cohort study (ALS COSMOS) with a well-phenotyped patient population (N = 355).Methods: Fasting plasma and first void urine samples were obtained. PCr, PUA, urinary 8-oxo-deoxy guanosine (8-oxodG), and 15-F2t-isoprostane (IsoP) were analyzed at baseline, near the midpoint of follow-up, and at the final blood draw (before death or withdrawal from study). We estimated associations between these biomarkers and the ALSFRS-R at baseline and survival.Results: At baseline, PCr correlated with ALSFRS-R (Spearman r = 0.30), percent (%) FVC (r = 0.20), PUA (r = 0.37), and 8-oxodG (r = −0.13, all p < 0.05). Baseline PCr significantly predicted survival (adjusted hazard ratio 0.28, p < 0.001). Time to death from baseline was shortest for those in the lowest two PCr quartiles relative to the highest two quartiles. PCr and ALSFRS-R values were significantly correlated at all three time points (baseline: r = 0.29, midpoint: r = 0.23, final: r = 0.38, all p < 0.001). PCr and PUA significantly declined over time, whereas OS biomarkers significantly increased over time.Conclusions: To date, PCr predicted survival the best, compared to PUA, 8-oxodG, and IsoP. Although PCr represents the degree of muscle mass, it may also represent complex biochemical changes in ALS. Because the field has no reliable prognostic biomarkers, the importance of PCr warrants further investigation through clinical studies in ALS.

Modulation of plasma and urine metabolome in colorectal cancer survivors consuming rice bran.

Rice bran has bioactive phytochemicals with cancer protective actions that involve metabolism by the host and the gut microbiome. Globally, colorectal cancer (CRC) is the third leading cause of cancer-related death and the increased incidence is largely attributed to poor dietary patterns, including low daily fiber intake. A dietary intervention trial was performed to investigate the impact of rice bran consumption on the plasma and urine metabolome of CRC survivors. Nineteen CRC survivors participated in a randomized-controlled trial that included consumption of heat-stabilized rice bran (30 g/day) or a control diet without rice bran for 4 weeks. A fasting plasma and first void of the morning urine sample were analyzed by non-targeted metabolomics using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). After 4 weeks of either rice bran or control diets, 12 plasma and 16 urine metabolites were significantly different between the groups (p≤0.05). Rice bran intake increased relative abundance of plasma mannose (1.373-fold) and beta-citrylglutamate (BCG) (1.593-fold), as well as increased urine N-formylphenylalanine (2.191-fold) and dehydroisoandrosterone sulfate (DHEA-S) (4.488-fold). Diet affected metabolites, such as benzoate, mannose, eicosapentaenoate (20:5n3) (EPA), and N-formylphenylalanine have been previously reported for cancer protection and were identified from the rice bran food metabolome. Nutritional metabolome changes following increased consumption of whole grains such as rice bran warrants continued investigation for colon cancer control and prevention attributes as dietary biomarkers for positive effects are needed to reduce high risk for colorectal cancer recurrence.

Mars nightside electrons over strong crustal fields

AbstractWe investigated 7 years worth of data from the electron reflectometer and magnetometer aboard Mars Global Surveyor to quantify the deposition of photoelectron and solar wind electron populations on the nightside of Mars, over the strong crustal field region located in the southern hemisphere. Just under 600,000 observations, each including energy and pitch angle distributions, were examined. For solar zenith angles (SZA) less than 110°, photoelectrons have the highest occurrence rate; beyond that, plasma voids occur most often. In addition, for SZA &gt;110°, energy deposition of electrons mainly occurs on vertical field lines with median pitch angle averaged energy flux values on the order of 107–108 eV cm−2 s−1. The fraction of downward flux that is deposited at a given location was typically low (16% or smaller), implying that the majority of precipitated electrons are magnetically reflected or scattered back out. The average energy of the deposited electrons is found to be 20–30 eV, comparable to typical energies of photoelectrons and unaccelerated solar wind electrons. Median electron flux values, from near‐vertical magnetic field lines past solar zenith angle of 110°, calculated in this study produced a total electron content of 4.2 × 1014 m−2 and a corresponding peak density of 4.2 × 103 cm−3.

GLOBAL DISTRIBUTION OF THE KINETIC SCALE MAGNETIC TURBULENCE AROUND THE MOON

ABSTRACT The Moon–solar wind interaction results in the formation of a complicated lunar space plasma environment. Here, we investigate the solar wind turbulence around the Moon using the magnetic field observed by the dual-probe mission Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS). Structure functions in a time range on kinetic scales are computed to measure the scaling index ζ, the spatial distribution of which reveals the global aspects of the lunar space plasma and shows the dependence on the local instability. On the lunar nightside, in the plasma void, the dominating magnetic pressure over the thermal pressure restrains the turbulence, and a quiet zone is built with &zeta; &Lt; &zeta; 0 ?> , where &zeta; 0 = 0.36 ?> is the scaling index in the ambient solar wind. Downstream in the lunar wake, ζ is elevated gradually and goes above &zeta; 0 ?> at a radial distance of &sim; 3 R m ?> (lunar radius), which implies that the plasma refilling process in the lunar wake begins to generate the local turbulence. On the dayside around the subsolar point, ζ is enhanced at a low altitude of ∼200 km, where the solar wind turbulence might be strengthened due to interaction with the lunar source plasma. The largest scaling indices lie around the day–night terminator with &zeta; &gt; 0.65 ?> , and the observed dawn–dusk asymmetry could be an effect of the magnetic field not being parallel with the solar wind. The correspondence between the enhanced scaling index and the local instability also raises new questions about the description of solar wind turbulence.

Solar wind plasma interaction with Gerasimovich lunar magnetic anomaly

AbstractWe present the results of the first local hybrid simulations (particle ions and fluid electrons) for the solar wind plasma interaction with realistic lunar crustal fields. We use a three‐dimensional hybrid model of plasma and an empirical model of the Gerasimovich magnetic anomaly based on Lunar Prospector observations. We examine the effects of low and high solar wind dynamic pressures on this interaction when the Gerasimovich magnetic anomaly is located at nearly 20∘ solar zenith angle. We find that for low solar wind dynamic pressure, the crustal fields mostly deflect the solar wind plasma, form a plasma void at very close distances to the Moon (below 20 km above the surface), and reflect nearly 5% of the solar wind in charged form. In contrast, during high solar wind dynamic pressure, the crustal fields are more compressed, the solar wind is less deflected, and the lunar surface is less shielded from impinging solar wind flux, but the solar wind ion reflection is more locally intensified (up to 25%) compared to low dynamic pressures. The difference is associated with an electrostatic potential that forms over the Gerasimovich magnetic anomaly as well as the effects of solar wind plasma on the crustal fields during low and high dynamic pressures. Finally, we show that an antimoonward Hall electric field is the dominant electric field for ∼3 km altitude and higher, and an ambipolar electric field has a noticeable contribution to the electric field at close distances (&lt;3 km) to the Moon.

Nightside electron precipitation at Mars: Geographic variability and dependence on solar wind conditions

Electron precipitation is usually the dominant source of energy input to the nightside Martian atmosphere, with consequences for ionospheric densities, chemistry, electrodynamics, communications, and navigation. We examine downward‐traveling superthermal electron flux on the Martian nightside from May 1999 to November 2006 at 400 km altitude and 2 A.M. local time. Electron precipitation is geographically organized by crustal magnetic field strength and elevation angle, with higher fluxes occurring in regions of weak and/or primarily vertical crustal fields, while stronger and more horizontal fields retard electron access to the atmosphere. We investigate how these crustal field‐organized precipitation patterns vary with proxies for solar wind (SW) pressure and interplanetary magnetic field (IMF) direction. Generally, higher precipitating fluxes accompany higher SW pressures. Specifically, we identify four characteristic spectral behaviors: (1) “stable” regions where fluxes increase mildly with SW pressure, (2) “high‐flux” regions where accelerated (peaked) spectra are more common and where fluxes below ~500 eV are largely independent of SW pressure, (3) permanent plasma voids, and (4) intermittent plasma voids where fluxes depend strongly on SW pressure. The locations, sizes, shapes, and absence/existence of these plasma voids vary significantly with solar wind pressure proxy and moderately with IMF proxy direction; average precipitating fluxes are 40% lower in strong crustal field regions and 15% lower globally for approximately southwest proxy directions compared with approximately northeast directions. This variation of the strength and geographic pattern of the shielding effect of Mars' crustal fields exemplifies the complex interaction between those fields and the solar wind.

The lunar wake current systems

We present the lunar wake current systems when the Moon is assumed to be a non‐conductive body, absorbing the solar wind plasma. We show that in the transition regions between the plasma void, the expanding rarefaction region, and the interplanetary plasma, there are three main currents flowing around these regions in the lunar wake. The generated currents induce magnetic fields within these regions and perturb the field lines there. We use a three‐dimensional, self‐consistent hybrid model of plasma (particle ions and fluid electrons) to show the flow of these three currents. First, we identify the different plasma regions, separated by the currents, and then we show how the currents depend on the interplanetary magnetic field direction. Finally, we discuss the current closures in the lunar wake.

SIMULATION OF DESCENDING MULTIPLE SUPRA-ARCADE RECONNECTION OUTFLOWS IN SOLAR FLARES

After recent AIA observations by Savage, McKenzie and Reeves we revisit the scenario proposed by us in previous papers. We have shown that sunward, generally dark plasma features originated above posteruption flare arcades are consistent with a scenario where plasma voids (which we identify as supra--arcade reconnection outflows, SAROs) generate the bouncing and interfering of shocks and expansion waves upstream of an initial localized deposition of energy which is collimated in the magnetic field direction. In this paper we analyze the multiple production and interaction of SAROs and their individual structure that make them relatively stable features while moving. We compare our results with observations and with the scenarios proposed by other authors.

Analysis of Cassini magnetic field observations over the poles of Rhea

We analyze Cassini magnetic field observations from the only two polar flybys of Saturn's largest icy satellite Rhea (R2 on 02 March 2010 and R3 on 11 January 2011) which are scheduled between Saturn Orbit Insertion and the end of the mission in 2017. For the interpretation of these data, we apply estimations from simple analytical models as well as results from numerical hybrid simulations (kinetic ions, fluid electrons) of Rhea's interaction with the incident magnetospheric plasma. In‐situ observations of exospheric neutral gas and pick‐up ions suggest Rhea to be embedded in a tenuous gas envelope. However, the interaction of this gas with the magnetospheric flow does not make any measurable contributions to the magnetic field perturbations detected above the poles of the moon. Instead, the field perturbations observed in these regions mainly arise from the absorption of magnetospheric particles with large field‐aligned velocities, impinging on the north and south polar surface of Rhea. In addition to numerous interaction features known from preceding Cassini flybys of Saturn's plasma‐absorbing moons, the magnetic field data acquired above Rhea's poles reveal perturbations of the flow‐aligned field component, corresponding to a draping/Alfvén wing pattern. Based on our hybrid simulations, we suggest that these signatures arise from the finite extension of Rhea's wakeside plasma void along the corotational flow direction, yielding a density gradient in corotation direction, and thereby generating a diamagnetic current from the Saturn‐facing into the Saturn‐averted hemisphere of the moon. This transverse current is responsible for generating a weak Alfvén wing pattern at Rhea which has been detected by the Cassini spacecraft during the R2 and R3 flybys. Due to the large gyroradii of the incident magnetospheric ions, this structure features a pronounced asymmetry with respect to the direction of the convective electric field. Results of our simulation, considering only plasma absorption on the moon, are in good agreement with Cassini magnetometer data from both flybys. At Saturn's icy satellites Tethys and Dione, the low value of the magnetospheric plasma beta most likely prevents the formation of similar currents and measurable flow‐aligned magnetic field distortions.

RE-INTERPRETATION OF SUPRA-ARCADE DOWNFLOWS IN SOLAR FLARES

Following the eruption of a filament from a flaring active region, sunward-flowing voids are often seen above developing post-eruption arcades. First discovered using the soft X-ray telescope aboard Yohkoh, these supra-arcade downflows (SADs) are now an expected observation of extreme ultra-violet (EUV) and soft X-ray coronal imagers and spectrographs (e.g, TRACE, SOHO/SUMER, Hinode/XRT, SDO/AIA). Observations made prior to the operation of AIA suggested that these plasma voids (which are seen in contrast to bright, high-temperature plasma associated with current sheets) are the cross-sections of evacuated flux tubes retracting from reconnection sites high in the corona. The high temperature imaging afforded by AIA's 131, 94, and 193 Angstrom channels coupled with the fast temporal cadence allows for unprecedented scrutiny of the voids. For a flare occurring on 2011 October 22, we provide evidence suggesting that SADs, instead of being the cross-sections of relatively large, evacuated flux tubes, are actually wakes (i.e., trailing regions of low density) created by the retraction of much thinner tubes. This re-interpretation is a significant shift in the fundamental understanding of SADs, as the features once thought to be identifiable as the shrinking loops themselves now appear to be "side effects" of the passage of the loops through the supra-arcade plasma. In light of the fact that previous measurements have attributed to the shrinking loops characteristics that may instead belong to their wakes, we discuss the implications of this new interpretation on previous parameter estimations, and on reconnection theory.

Simulation of dark lanes in post-flare supra-arcades – II. A contribution to the remote sensing of the coronal magnetic field

Abstract We integrate the MHD ideal equations to simulate dark void sunwardly moving structures in post-flare supra-arcades. In Costa et al. we could numerically reproduce the observations described in Verwichte et al. We showed that the dark tracks are plasma vacuums generated by the bouncing and interfering of shocks and expansion waves, upstream an initial slow magnetoacoustic shock produced by a localized deposition of energy modelled as a pressure perturbation. The same pressure perturbation produces a transverse to the field or perpendicular magnetic shock giving rise to non-linear waves that compose the kink-like plasma void structures, with the same functional sunward decreasing phase speed and period's constancy with height, as those determined by the observations. In this Letter we accomplish a study of sensitivity to initial and background physical conditions of the phenomenon. With the aim of contributing to the remote sensing of the corona we describe the characteristics of different void structures in terms of physical conditions, i.e. magnetic field intensity and pressure perturbation, given a background density.

Anticipated electrical environment within permanently shadowed lunar craters

Shadowed locations near the lunar poles are almost certainly electrically complex regions. At these locations near the terminator, the local solar wind flows nearly tangential to the surface and interacts with large‐scale topographic features such as mountains and deep large craters. In this work, we study the solar wind orographic effects from topographic obstructions along a rough lunar surface. On the leeward side of large obstructions, plasma voids are formed in the solar wind because of the absorption of plasma on the upstream surface of these obstacles. Solar wind plasma expands into such voids, producing an ambipolar potential that diverts ion flow into the void region. A surface potential is established on these leeward surfaces in order to balance the currents from the expansion‐limited electron and ion populations. We find that there are regions near the leeward wall of the craters and leeward mountain faces where solar wind ions cannot access the surface, leaving an electron‐rich plasma previously identified as an “electron cloud.” In this case, some new current is required to complete the closure for current balance at the surface, and we propose herein that lofted negatively charged dust is one possible (nonunique) compensating current source. Given models for both ambipolar and surface plasma processes, we consider the electrical environment around the large topographic features of the south pole (including Shoemaker crater and the highly varied terrain near Nobile crater), as derived from Goldstone radar data. We also apply our model to moving and stationary objects of differing compositions located on the surface and consider the impact of the deflected ion flow on possible hydrogen resources within the craters.

Simulation of dark lanes in post-flare supra-arcade

Abstract We integrate the magnetohydrodynamics (MHD) ideal equations to simulate dark void sunwardly moving structures in post-flare supra-arcades. We study the onset and evolution of the internal plasma instability to compare with observations and to gain insight into physical processes and characteristic parameters of these phenomena. The numerical approach uses a finite-volume Harten–Yee total variation diminishing (TVD) scheme to integrate the 1D 1/2 MHD equations specially designed to capture supersonic flow discontinuities. The integration is performed in both directions, the sunward radial one and the transverse to the magnetic field. For the first time, we numerically reproduce observational dark voids described in Verwichte et al. We show that the dark tracks are plasma vacuums generated by the bouncing and interfering of shocks and expansion waves, upstream an initial slow magnetoacoustic shock produced by a localized deposition of energy modelled with a pressure perturbation. The same pressure perturbation produces a transverse to the field or perpendicular magnetic shock giving rise to non-linear waves that compose the kink-like plasma void structures, with the same functional sunward decreasing phase speed and constancy with height of the period, as those determined by the observations.