Plasma Flow Speed Research Articles

#503 The influence of the degree of liver cell failure on the functional state of the kidneys in patients with liver cirrhosis

Abstract Background and Aims Studying the influence of the severity of liver cirrhosis on the functional ability of the kidneys in patients without concomitant diseases (without diabetes mellitus and hypertension). Method The study included 38 patients with liver cirrhosis who were treated in the gastroenterology department of the Republican Scientific and Practical Center for Therapy and Medical Rehabilitation in Tashkent. The average age of patients was 54 ± 3.4 (from 33 to 65). The examined patients were divided into two groups, depending on the degree of hepatic cellular failure (according to the Child-Pugh classification) and the development of ascitic syndrome. In group 1 Liver cirrhosis without ascites (P-P class A) the number of patients was 20. In group 2 Liver cirrhosis with ascites (P-P class B) the number of patients was 18. When examining patients, we used: Clinical blood test; blood chemistry; determination of electrolytes, creatinine; general urine analysis; glomerular filtration level; Functional renal reserve (defined as the increase in glomerular filtration expressed as a percentage after the administration of Dopamine at a dose of 2-3 μg/kg/min. To assess portal hypertension, all patients underwent ultrasound examination of the organs abdominal cavity and duplex scanning of portal system vessels. Results The examined patients were analyzed for the functional state of the kidneys and its relationship with the main parameters of portal hypertension and hepatic cell failure. Comparative characteristics of the main indicators of renal function significant differences in functional parameters were revealed depending on degree of hepatic cell failure. In the group of patients with cirrhosis with ascites, there was a significant decrease in renal GFR to 77.5 ± 1.4 ml/min, in contrast to the unchanged level of GFR in the group of patients with cirrhosis without ascites—99.3 ml/min. In patients with cirrhosis without ascites, the glomerular filtration rate increases by against the background of dopamine administration was 13.5 ± 4.7% (which corresponds to the norm), in contrast to patients in the second group, where the average Renal Functional Reserve was 8.4 ± 2.8%. Changes in renal function were also characterized by a decrease in Fractional Excretion of Sodium (FENa). The reduction in FENa in the group of patients with persistent ascites. During a detailed assessment of the RFR in patients of the first group, the RFR was below normal only in 2.6 ± 2.5%, while in the second group the number of patients with the decrease in the RFR was 69.7 ± 8.1%. Study of functional renal reserve in a group of patients with cirrhosis with ascites revealed unchanged this indicator in only 10 (30.3 ± 8%). U 19 (57.5 ± 8.6%) of patients in this group, the RFR was less than 10%, and in 12.2 ± 5.7% cases of RFR was below 5%, which indicated pronounced intraglomerular hypertension and the risk of developing resistant ascites. Conclusion The present study indicates that Renal Functional Reserve (RFR) in patients with liver cirrhosis reflects the speed of effective renal plasma flow. A decrease in FPR in Child-Pugh class A liver cirrhosis was detected in 2.6% of cases, with hepatic cell failure, Child-Pugh class B in 69.7%.

Variation in the Pedersen Conductance Near Jupiter's Main Emission Aurora: Comparison of Hubble Space Telescope and Galileo Measurements

AbstractWe present the first large‐scale statistical survey of the Jovian main emission (ME) to map auroral properties from their ionospheric locations out into the equatorial plane of the magnetosphere, where they are compared directly to in‐situ spacecraft measurements. We use magnetosphere‐ionosphere (MI) coupling theory to calculate currents from the auroral brightness as measured with the Hubble Space Telescope and from plasma flow speeds measured in‐situ with the Galileo spacecraft. The effective Pedersen conductance of the ionosphere remains a free parameter in this comparison. We calculate the Pedersen conductance from the combined data sets, and find it ranges from mho overall with averages of mho in the north and mho in the south. Considering the HST‐derived field‐aligned currents per radian of azimuth only, we find values of MA rad−1 and MA rad−1 in the north and south, respectively, in general agreement with previous results. Taking the currents and effective Pedersen conductance together, we find that the average ME intensity and plasma flow speed in the middle magnetosphere (10–30 RJ) are broadly consistent with one another under MI coupling theory. We find evidence for peaks in the distribution of near dawn, then again near 12 and 14 hr magnetic local time (MLT). This variation in Pedersen conductance with MLT may indicate the importance of conductance in modulating MLT‐ and local‐time‐asymmetries in the ME, including the apparent subcorotation of some auroral features within the ME.

A new mechanism for internal kink stabilization by plasma flow and anisotropic thermal transport

Stability of the internal kink (IK) mode is numerically investigated with inclusion of the anisotropic thermal transport effect and the toroidal plasma flow. It is found that anisotropic thermal transport, in combination with plasma flow, stabilizes the IK in two ways. One is direct stabilization of the mode synergistically with plasma flow. The other, indirect stabilization involves generation of a finite mode frequency in static plasmas by thermal transport, which in turn invokes wave-wave resonance damping of the mode via interaction with stable shear Alfvén waves. This second IK stabilization mechanism is further corroborated by examining the eigenmode structure, which peaks at the radial locations where the mode frequency matches that of the shear Alfvén wave. Finally, two branches of unstable IK are identified, with mode conversion occurring at certain plasma flow speed and thermal transport level. These findings provide new physics insights in the IK stability in tokamak fusion plasmas.

Prediction of ionospheric total electron content data using spatio-temporal residual network

Since the ionospheric total electron content (TEC) exhibits complex spatial and temporal behaviour including the seasonal and solar activity dependencies, resulting in large scale differences across different regions of the world, developing an effective deep-learning-based predictive model, capturing the complex behaviour of TEC is much needed. We present a novel deep learning-based model to predict the TEC using the spatio-temporal residual network (ST-ResNet). The TEC data used in the study were obtained from 185 GPS receiver locations, covering the latitude region from 10° N to 80° N and the longitude region from 110° W to 34° E. We considered TEC data of 154 days each corresponding to the solar maximum (2014) and the solar minimum (2020) years for training the network together with the exogeneous interplanetary magnetic field (IMF) data, including the magnetic field components By, Bz, plasma flow speed (Vp), and proton density (Np). A total of 44,352 maps (collected at the rate of 288 maps per day) were pre-processed by grouping them into closeness, period, and trend channels, which associate with the near-time, short-term, and long-term trends in the TEC data, respectively. After training, the model was tested for one day. The objectives of the study are: i) To develop and evaluate the performance of the ST-ResNet model, ii) to assess its performance on TEC data corresponding to mid-latitude region, under different solar conditions and iii) to compare the ST-ResNet model with other predicted models. For the entire study region, the root mean squared error (RMSE) was found to be 3.13 TECU for the solar maximum year and 1.23 TECU for the solar minimum year. Similar trends were observed in the mid-latitude region (30° N-60° N), with RMSE values of 2.31 TECU and 1.58 TECU for the solar maximum and solar minimum years, respectively. ST-ResNet model showed an improved accuracy over the long short-term memory (LSTM) deep learning network by about 23% and 31% for the entire study region and by 49% and 19% for only mid-latitude region, during the solar maximum and minimum years respectively, suggesting the superior performance of ST-ResNet over the LSTM network. A comparative observation of results of ST-ResNet model with those of back propagation and international reference ionosphere-2016 (IRI-2016) model also showed the superiority of the former. Results confirm the suitability of the ST-ResNet model for predicting the spatial and temporal behavior of TEC across different locations during various solar conditions.

X-ray transmission effects in a high-density dynamic-dusty plasma environment

X-ray communication (XCOM), which employs modulated X-ray photons as the carrier for signal transmission, is a promising wireless optical technology for space applications, particularly during spacecraft blackout re-entry. Currently, several challenges related to XCOM require solutions, including incomplete transmission attenuation models and a lack of experimental verification of the dynamic-dusty communication effects. This study improved the XCOM transmission characteristics in high-density dynamic-dusty plasma based on a collision model. A dynamic-dusty plasma XCOM was built to verify a modulated X-ray tube and an alkali-metal plasma source. The results show that with an increase in photon energy and flow, the X-ray carrier achieves a higher transmission speed, which is sharper than that of photon energy under the influence of flow. When the average electron density of the dusty plasma is 1012–1013 cm−2, the plasma flow speed is 550–650 m/s, the macro temperature exceeds 1500 K, and the communication demonstration system achieves a stable data rate of 50 kbps at a bit error (BER) of 1.7 × 10−5 with a carrier amplitude and frequency of approximately 20 kV and 4.8 Mcps, respectively. This experiment yielded theoretical and actual values for the development of XCOM technology in space applications during re-entry blackouts.

Evidence of persistence of weak magnetic cycles driven by meridional plasma flows during solar grand minima phases

ABSTRACT Long-term sunspot observations and solar activity reconstructions reveal that the Sun occasionally slips into quiescent phases known as solar grand minima, the dynamics during which is not well understood. We use a flux transport dynamo model with stochastic fluctuations in the mean-field and Babcock–Leighton poloidal field source terms to simulate solar cycle variability. Our long-term simulations detect a gradual decay of the polar field during solar grand minima episodes. Although regular active region emergence stops, compromising the Babcock–Leighton mechanism, weak magnetic activity continues during minima phases sustained by a mean-field α-effect; surprisingly, periodic polar field amplitude modulation persists during these phases. A spectral analysis of the simulated polar flux time series shows that the 11-yr cycle becomes less prominent while high frequency periods and periods around 22 yr manifest during grand minima episodes. Analysis of long-term solar open flux observations appears to be consistent with this finding. Through numerical experimentation, we demonstrate that the persistence of periodic amplitude modulation in the polar field and the dominant frequencies during grand minima episodes are governed by the speed of the meridional plasma flow – which appears to act as a clock.

Generic profile of a long-lived corotating interaction region and associated recurrent Forbush decrease

Context.Corotating interaction regions (CIRs), formed by the interaction of slow solar wind and fast streams that originate from coronal holes (CHs), produce recurrent Forbush decreases, which are short-term depressions in the galactic cosmic ray (GCR) flux.Aims.Our aim is to prepare a reliable set of CIR measurements to be used as a textbook for modeling efforts. For that purpose, we observe and analyse a long-lived CIR, originating from a single CH, recurring in 27 consecutive Carrington rotations 2057–2083 in the time period from June 2007–May 2009.Methods.We studied the in situ measurements of this long-lived CIR as well as the corresponding depression in the cosmic ray (CR) count observed by SOHO/EPHIN throughout different rotations. We performed a statistical analysis, as well as the superposed epoch analysis, using relative values of the key parameters: the total magnetic field strength,B, the magnetic field fluctuations,dBrms, plasma flow speed,v, plasma density,n, plasma temperature,T, and the SOHO/EPHIN F-detector particle count, and CR count.Results.We find that the mirrored CR count-time profile is correlated with that of the flow speed, ranging from moderate to strong correlation, depending on the rotation. In addition, we find that the CR count dip amplitude is correlated to the peak in the magnetic field and flow speed of the CIR. These results are in agreement with previous statistical studies. Finally, using the superposed epoch analysis, we obtain a generic CIR example, which reflects the in situ properties of a typical CIR well.Conclusions.Our results are better explained based on the combined convection-diffusion approach of the CIR-related GCR modulation. Furthermore, qualitatively, our results do not differ from those based on different CHs samples. This indicates that the change of the physical properties of the recurring CIR from one rotation to another is not qualitatively different from the change of the physical properties of CIRs originating from different CHs. Finally, the obtained generic CIR example, analyzed on the basis of superposed epoch analysis, can be used as a reference for testing future models.

Plasma Flows in Solar Filaments as Electromagnetically Driven Vortical Flows

Electromagnetic expulsion acts on a body suspended in a conducting fluid or plasma, which is subject to the influence of electric and magnetic fields. Physically, the effect is a magnetohydrodynamic analogue of the buoyancy (Archimedean) force, which is caused by the nonequal electric conductivities inside and outside the body. It is suggested that electromagnetic expulsion can drive the observed plasma counter-streaming flows in solar filaments. Exact analytical solutions and scaling arguments for a characteristic plasma flow speed are reviewed, and their applicability in the limit of large magnetic Reynolds numbers, relevant in the solar corona, is discussed.

Anomalous Reconnection Layer at Earth's Dayside Magnetopause

AbstractObservations by the Magnetospheric Multiscale spacecraft (MMS) of an unusual layer, located between the dayside magnetosheath and the magnetosphere, alternating with encounters with the magnetosheath during an extended time period between December 31, 2015 and January 01, 2016, when the interplanetary magnetic field was strongly southward and the Earth's dipole tilt large and negative, are presented. It appears to have been magnetically connected to both magnetosphere and magnetosheath. The layer appears to be located mostly on closed field lines and was bounded by a rotational discontinuity (RD) at its magnetosheath edge and by the magnetosphere on its earthward side. A separatrix layer, with heated magnetosheath electrons streaming unidirectionally along the field lines, was present sunward of the RD. We infer that the layer was started by a dominant reconnection site well north of the spacecraft and that it may have gained additional width, from a large drop in solar wind density and ram pressure, which preceded the beginning of the event by more than an hour. Relative to the magnetosheath, in which the magnetic field was strongly southward, this unusual layer was characterized by a less southward, more dawnward magnetic field of lower magnitude. The plasma density and flow speed in the region were lower than in the magnetosheath, albeit with Alfvénic jetting occurring at the magnetosheath edge as well as at the magnetospheric edge of the layer. The closing of the magnetic field lines requires the existence of another reconnection site, located southward/tailward of MMS.

Analytical Assessment of Kelvin‐Helmholtz Instability Growth at Ganymede's Upstream Magnetopause

AbstractGanymede is the only Solar System moon that generates a permanent magnetic field. Dynamics within the Ganymedean magnetosphere is thought to be driven by energy‐transfer interactions on its upstream magnetopause. Previously in Kaweeyanun et al. (2020), https://doi.org/10.1029/2019GL086228 we created a steady‐state analytical model of Ganymede's magnetopause and predicted global‐scale magnetic reconnection to occur frequently throughout the surface. This paper subsequently provides the first assessment of Kelvin‐Helmholtz (K‐H) instability growth on the magnetopause. Using the same analytical model, we find that linear K‐H waves are expected on both Ganymedean magnetopause flanks. Once formed, the waves propagate downstream at roughly half the speed of the external Jovian plasma flow. The Ganymedean K‐H instability growth is asymmetric between magnetopause flanks due to the finite Larmor radius effect arising from large gyroradii of Jovian plasma ions. A small but notable enhancement is expected on the sub‐Jovian flank according to the physical understanding of bulk plasma and local ion flows alongside comparisons to the well‐observed magnetopause of Mercury. Further evaluation shows that nonlinear K‐H vortices should be strongly suppressed by concurring global‐scale magnetic reconnection at Ganymede. Reconnection is therefore the dominant cross‐magnetopause energy‐transfer mechanism and driver of global‐scale plasma convection within Ganymede's magnetosphere.

Simulation Inference of Plasma Parameters From Langmuir Probe Measurements

AbstractA novel approach is presented to infer plasma parameters from Langmuir probe measurements. Three‐dimensional kinetic simulations capable of accounting for multiple physical processes and realistic measurement conditions, are used to construct synthetic data sets, or solution libraries, consisting of computed probe collected currents, with corresponding plasma environment parameters. Applying the Swarm standard data analysis procedure to infer density and temperatures, and comparing them with values used in the simulations, provides an assessment of the uncertainties resulting from these procedures. A significant source of discrepancy is found to come from the neglect of minority light ions, and the effect of the sheath of the nearby satellite. An empirical relation is constructed, which reproduces the plasma density within 5%, given probe voltages and collected currents, and known temperatures, effective masses, plasma flow speeds, and the satellite floating potential. This relation is presented as a useful constraint between these several variables; not all of which being measured or estimated accurately in situ.

X-Ray through Very High Energy Intrabinary Shock Emission from Black Widows and Redbacks

Abstract Black widow and redback systems are compact binaries in which a millisecond pulsar heats and may even ablate its low-mass companion by its intense wind of relativistic particles and radiation. In such systems, an intrabinary shock can form as a site of particle acceleration and associated nonthermal emission. We model the X-ray and gamma-ray synchrotron and inverse Compton spectral components for select spider binaries, including diffusion, convection, and radiative energy losses in an axially symmetric, steady-state approach. Our new multizone code simultaneously yields energy-dependent light curves and orbital-phase-resolved spectra. Using parameter studies and matching the observed X-ray spectra and light curves, as well as Fermi Large Area Telescope spectra where available, with a synchrotron component, we can constrain certain model parameters. For PSR J1723–2837 these are notably the magnetic field and bulk flow speed of plasma moving along the shock tangent, the shock acceleration efficiency, and the multiplicity and spectrum of pairs accelerated by the pulsar. This affords a more robust prediction of the expected high-energy and very high energy gamma-ray flux. We find that nearby pulsars with hot or flaring companions may be promising targets for the future Cerenkov Telescope Array. Moreover, many spiders are likely to be of significant interest to future MeV-band missions such as AMEGO and e-ASTROGAM.

Magnetic Helicity Flux across Solar Active Region Photospheres. I. Hemispheric Sign Preference in Solar Cycle 24

Abstract A hemispheric preference in the dominant sign of magnetic helicity has been observed in numerous features in the solar atmosphere, i.e., left-handed/right-handed helicity in the northern/southern hemisphere. The relative importance of different physical processes that may contribute to the observed hemispheric sign preference (HSP) of magnetic helicity is still under debate. Here, we estimate magnetic helicity flux (dH/dt) across the photospheric surface for 4802 samples of 1105 unique active regions (ARs) that appeared over an 8 yr period from 2010 to 2017 during solar cycle 24, using photospheric vector magnetic field observations by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The estimates of dH/dt show that 63% and 65% of the investigated AR samples in the northern and southern hemispheres, respectively, follow the HSP. We also find a trend that the HSP of dH/dt increases from ∼50%–60% up to ∼70%–80% as ARs (1) appear at the earlier inclining phase of the solar cycle or higher latitudes and (2) have larger values of , the total unsigned magnetic flux, and the average plasma-flow speed. These observational findings support the enhancement of the HSP mainly by the Coriolis force acting on a buoyantly rising and expanding flux tube through the turbulent convection zone. In addition, the differential rotation on the solar surface as well as the tachocline α-effect of a flux-transport dynamo may reinforce the HSP for ARs at higher latitudes.

Mathematical analysis of the 09 March 2012 intense storm

The in-depth investigation of the parameters of the solar wind, the zonal geomagnetic indices and the interplanetary magnetic field (IMF) is the key to furthering space weather researches. The investigations got meaning through modeling various interplanetary parameters and geomagnetic indices. These models, built on the basis of the correlations between solar wind parameters and zonal geomagnetic indices, and that must strictly obey physical principles, will not only reveal the properties of geomagnetic activity but also allow estimates of their formations. This study focuses on the 2012 March 09 phenomenon, the first intense geomagnetic storm of the 24th solar cycle. The deeper understanding of the storm depends on a correct interpretation and visualization of the relationship between solar wind plasma parameters (solar wind dynamic pressure (P), flow speed (v), electric field (E), magnetic field (Bz), proton density (N), temperature (T)) and zonal geomagnetic indices (AE, ap, Kp, Dst). The study investigates, visualizes and interprets the solar wind plasma parameters and zonal geomagnetic indices themselves. The storm variables set included of observations of ten variables from NASA are described. By this investigation a covariance matrix indicates the strength of bivariate relationships, a dendrogram indicates hierarchical clustering into groups, and factor analysis indicates three distinct eigenvectors. In addition, linear and nonlinear models about the problem are introduced to readers. The author discuses mathematically what happened in the storm on 2012 March 09 at the beginning of the 24th solar cycle. The aim of this work is to help the reader understand the storm by providing the models that the representatives of parameters and indices coexist.

Effects of Solar Wind Plasma Flow and Interplanetary Magnetic Field on the Spatial Structure of Earth's Radiation Belts

AbstractBased on the statistical data measured by Van Allen Probes from 2012 to 2016, we analyzed the effects of solar wind plasma flow and interplanetary magnetic field (IMF) on the spatial distribution of Earth's radiation belt electrons (>100 keV). The statistical results indicate that the increases in solar wind plasma density and flow speed can exert different effects on the spatial structure of the radiation belts. The high solar wind plasma density (≥6 cm−3)/flow pressure (≥2.5 nPa) and a large southward IMF (Bz < −6 nT) usually appear in the front of high‐speed solar wind streams (≥450 km/s), and they tend to narrow the outer radiation belt but broaden the slot region. In contrast, the increase in solar wind flow speed can broaden the outer radiation belt but narrows the slot region. When the solar wind speed exceeds 500 km/s, the outer radiation belt electrons can penetrate into the slot region (L < 3) and even enter the inner radiation belt (L < 2). The lower‐energy electrons penetrate into the deeper (smaller‐L) region than the higher‐energy electrons.

Pressure Gradients Driving Ion Transport in the Topside Martian Atmosphere

AbstractMagnetic and thermal pressure gradient forces drive plasma flow in the topside ionosphere of Mars. Some of this flow can contribute to ion loss from the planet and thus affect atmospheric evolution. MAVEN measurements of the magnetic field, electron density, and electron temperature, taken over a 3‐year time period, are used to obtain averaged magnetic and thermal pressures in the topside ionosphere versus altitude, solar zenith angle, and latitude. Magnetic pressures are several times greater than thermal pressures for altitudes greater than about 300 km; that is, the plasma beta is less than one. The total pressure increases with altitude in the ionosphere and decreases with increasing solar zenith angle. Using these pressure patterns in the dayside ionosphere to estimate the pressure gradient force in the fluid momentum equation, we estimate horizontal day‐to‐night plasma flow speeds of a few kilometers per second near 400 km.

Ion Charge States in a Time-Dependent Wave-Turbulence-Driven Model of the Solar Wind

Ion fractional charge states, measured in situ in the heliosphere, depend on the properties of the plasma in the inner corona. As the ions travel outward in the solar wind and the electron density drops, the charge states remain essentially unaltered or "frozen in". Thus they can provide a powerful constraint on heating models of the corona and acceleration of the solar wind. We have implemented non-equilibrium ionization calculations into a 1D wave-turbulence-driven (WTD) hydrodynamic solar wind model and compared modeled charge states with the Ulysses 1994-5 in situ measurements. We have found that modeled charge state ratios of $C^{6+}/C^{5+}$ and $O^{7+}/O^{6+}$, among others, were too low compared with Ulysses measurements. However, a heuristic reduction of the plasma flow speed has been able to bring the modeled results in line with observations, though other ideas have been proposed to address this discrepancy. We discuss implications of our results and the prospect of including ion charge state calculations into our 3D MHD model of the inner heliosphere.

Long-Term Independence of Solar Wind Polytropic Index on Plasma Flow Speed.

The paper derives the polytropic indices over the last two solar cycles (years 1995–2017) for the solar wind proton plasma near Earth (~1 AU). We use ~92-s datasets of proton plasma moments (speed, density, and temperature), measured from the Solar Wind Experiment instrument onboard Wind spacecraft, to estimate the moving averages of the polytropic index, as well as their weighted means and standard errors as a function of the solar wind speed and the year of measurements. The derived long-term behavior of the polytropic index agrees with the results of other previous methods. In particular, we find that the polytropic index remains quasi-constant with respect to the plasma flow speed, in agreement with earlier analyses of solar wind plasma. It is shown that most of the fluctuations of the polytropic index appear in the fast solar wind. The polytropic index remains quasi-constant, despite the frequent entropic variations. Therefore, on an annual basis, the polytropic index of the solar wind proton plasma near ~1 AU can be considered independent of the plasma flow speed. The estimated all-year weighted mean and its standard error is γ = 1.86 ± 0.09.

Structure and Variability of the Martian Ion Composition Boundary Layer

AbstractA complex boundary layer with a variety of charged particle and electromagnetic field signatures, including a transition between plasma predominantly of solar wind origin and plasma of planetary origin, lies between the Martian bow shock and the ionosphere. In this paper, we develop and utilize algorithms to autonomously identify and characterize this ion composition boundary (ICB), using data from the Mars Atmosphere and Volatile EvolutioN mission. We find an asymmetric ICB with a larger average thickness, lower altitude, and lower velocity shear in the hemisphere where the solar wind motional electric field points outward, as a result of the asymmetry of the mass loading process. The ICB thickness scales with the magnetosheath proton gyroradius at the top of the boundary layer but does not clearly vary with external drivers. The ICB location varies with solar wind ram pressure and crustal magnetic field strength, but does not clearly respond to solar wind Mach number or extreme ultraviolet irradiance. The ICB represents a distinct boundary for ion density and flow speed, but the magnetic field strength and direction typically do not vary significantly across the ICB. The plasma density and flow speed at the ICB vary seasonally, likely in response to variations in the neutral exosphere and/or atmosphere. However, the ICB on average remains at or below the altitude where pressure balance is achieved between the piled up magnetic field and the solar wind ram pressure, regardless of season or crustal magnetic field strength.

Toroidal modeling of interaction between internal kink mode and plasma flow

Non-linear interaction between the internal kink mode and toroidal plasma rotation is numerically studied using the MARS-Q code [Liu et al., Phys. Plasmas 20, 042503 (2013)]. Simulation results show core plasma flow damping due to various toroidal torques, generated by a weakly stable internal kink mode. The 3-D field perturbation induced torques, including the neoclassical toroidal viscous (NTV) torque, as well as that produced by the Maxwell and Reynolds stresses, act as sink terms in the toroidal momentum balance model. The NTV torque is found to play a dominant role in the flow damping in all cases considered in this study. The modification to the internal kink mode structure is observed during the flow damping. Whilst a steady state can be achieved in the coupled mode-flow evolution with a uniform initial flow, a sheared initial flow affects the linear stability of the mode and consequently changes the non-linear evolution. For cases where the steady state solution is achieved, the saturated plasma flow speed critically depends on the initial flow condition as well as the initial amplitude of the internal kink mode but is less sensitive to the on-axis safety factor q0, as long as the latter stays above 1.