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The present study provides an evidence for the generation of harmonics of magnetosonic waves in the Martian magnetosheath region. The wave signatures are manifested in the magnetic field measurements recorded by the fluxgate magnetometer instrument onboard the Mars Atmosphere and Volatile Evolution missioN (MAVEN) spacecraft in the dawn sector around 5–10 LT at an altitude of 4,000–6,000 kms. The wave that is observed continuously from 19.1 to 20.7 UT below the proton cyclotron frequency (fci ≈ 46 mHz) is identified as fundamental mode of the magnetosonic wave. Whereas harmonics of the magnetosonic wave are observed during 19.7–20.3 UT at frequencies that are multiple of fci. The ambient solar wind proton density and plasma flow velocity are found to vary with a fundamental mode frequency of 46 mHz. It is noticed that the fundamental mode is mainly associated with the left‐hand (LH), and higher frequency harmonics are associated with the right‐hand (RH) circular polarizations. A clear difference in the polarization and ellipticity is noticed during the time of occurrence of harmonics. The magnetosonic wave harmonics are found to propagate in the quasi‐perpendicular directions to the ambient magnetic field. The results of linear theory and Particle‐In‐Cell simulation performed here are in agreement with the observations. The present study provides a conclusive evidence for the occurrence of harmonics of magnetosonic wave in the close vicinity of the magnetosheath region of the unmagnetized planet Mars. Plain Language Summary: Mars is an unmagnetized planet. The solar wind particles that bombard Mars continuously, are responsible for the loss of its atmosphere. This scenario is opposite to that of the Earth, as its strong intrinsic magnetic field forms a protective shield around the planet, called the magnetosphere. Various electrostatic/electromagnetic waves are often generated in the Earth's magnetosphere, which are potential candidates for controlling the transfer of energy and momentum from one region to another. In case of Mars, it possesses a weakly induced magnetosphere, which is dynamic due to its continuous interactions with solar wind. The field measurements from the MAVEN spacecraft can be used to understand plasma waves in the vicinity of Mars. Here, we report the first observations of the harmonics of magnetosonic wave in the Martian magnetosheath region. The magnetosonic waves are low‐frequency compressive waves driven by the ions in the presence of magnetic field. These waves are known to play a role in the particle heating process in the Earth's magnetosphere. Therefore, its observation in the Martian plasma environment is of interest to the scientific community to understand their role in plasma heating in the Martian ionosphere‐magnetosphere system. Key Points: Harmonics of Magnetosonic wave are observed in the Martian magnetosphere in dawn sector (5–10 LT)Magnetosonic harmonics dominantly have right‐handed polarizationAmbient proton density and velocity found to vary with fundamental mode frequency of 46 mHz [ABSTRACT FROM AUTHOR]

The low latitude ionosphere and thermosphere are strongly disturbed during and shortly after geomagnetic storms. We use novel Jicamarca radar measurements, ACE satellite solar wind, and SuperMAG geomagnetic field observations to study the electrodynamic response of the equatorial ionosphere to the 23, 24 April 2023 geomagnetic storm. We also compare our data with results from previous experimental and modeling studies of equatorial storm-time electrodynamics. We show, for the first time, unusually large equatorial vertical and zonal plasma drift (zonal and meridional electric field) perturbations driven simultaneously by multi storm-time electric field mechanisms during both the storm main and recovery phases. These include daytime undershielding and overshielding prompt penetration electric fields driven by solar wind electric fields and dynamic pressure changes, substorms, as well as disturbance dynamo electric fields, which are not well reproduced by current empirical models. Our nighttime measurements, over an extended period of large and slowly decreasing southward IMF Bz, show very large, substorm-driven, vertical and zonal drift fluctuations superposed on large undershield driven upward and westward drifts up to about 01 LT, and the occurrence of equatorial spread F irregularities with very strong spatial and temporal structuring. These nighttime observations cannot be explained by present models of equatorial storm-time electrodynamics. [ABSTRACT FROM AUTHOR]

This study examines the variation of different energies linked with the Sun and the Earth’s magnetosphere-ionosphere systems for solar cycles (SCs) 22–24 for which the gradual decrease in the solar activity is noticed. Firstly, we investigated the variation of solar magnetic energy density (SMED) for SCs 21–24 and its relation to the solar activity. We observed distinct double peak structures in SMED for the past four SCs, 21–24. This feature is consistent with noticeable asymmetry in their two peaks. For SCs 22–24 a significant decrease is observed in the integrated SMED of each SC. This reduction is 37% from SCs 22 to 23 and 51% from SCs 23 to 24, which indicates substantial weakening of Sun’s magnetic field for SC 24. Also, the magnetic, kinetic, and thermal energy densities at the Earth’s bow-shock nose are found to be considerably low for the SC 24. We examined the solar wind Alfven speed, magnetosonic Mach number, solar wind-magnetosphere energy coupling parameter (ε), and the Chapman-Ferraro magnetopause distance (LCF) for the SCs 22–24. The estimated maximum stand-off magnetopause distance is larger for SC 24 (LCF ≤ 10.6 RE) as compared to SC 23 (LCF ≤ 10.2 RE) and SC 22 (LCF ≤ 9.8 RE). The solar wind Alfven speeds during SCs 22 and 23 are in the same range and do not exceed ≈73 km/s whereas, it is below 57 km/s for SC 24. A lower bound of solar wind magnetosonic Mach number for SC 24 is larger (M ≥ 6.9) as compared to SC 22 (M ≥ 5.9) and SC 23 (M ≥ 6). We noticed weakening in the energy coupling parameter for SC 24, which resulted in substantial (15%–38%) decrease in average strength of high latitude ionospheric (AE), low latitude magnetospheric (Dst) and equatorial ionospheric (EEJ) current systems in comparison with SC 23. Subsequently, a reduction of ≈30% is manifested in the high latitude Joule heating for SC 24. Overall this study indicates the significant step down in various energies at Sun, Earth’s bow-shock, and near Earth environment for current SC 24, which will have important implication on our Earth’s atmosphere-ionosphere-magnetosphere system.

Coherent bipolar electric field structures with negative unipolar potentials are widely observed in space plasmas. These bipolar structures are often found to be ion Bernstein Greene Kruskal (BGK) modes or ion holes. Most theoretical models of ion holes assume them to be stationary with respect to the background plasma that follows either Maxwellian or kappa-type distribution. In this paper, we present a new theoretical model of ion holes where the structures are non-stationary, and electrons follow flat-topped distribution. We use the classical BGK approach to derive the inequality separating allowed and forbidden simultaneous values of amplitude and spatial width of ion holes. The model reveals that the parametric space for the existence of ion holes decreases with their speed. We applied the developed model to the largest available dataset of ion holes obtained from the magnetospheric multiscale spacecraft observations in the Earth's bow shock region. [ABSTRACT FROM AUTHOR]

The prediction of an extended solar minimum is extremely important because of the severity of its impact on the near-earth space. Here, we present a new method for predicting the descent time of the forthcoming solar cycle (SC); the method is based on the estimation of the Shannon entropy. We use the daily and monthly smoothed international sunspot number. For each nth SC, we compute the parameter [Tpre]n by using information on the descent and ascent times of the n − 3th and nth SCs, respectively. We find that [Tpre] of nth SC and entropy can be effectively used to predict the descent time of the n + 2th SC. The correlation coefficient between [Td]n+2 − [Tpre]n and [E]n is found to be 0.95. Using these parameters the prediction model is developed. Solar magnetic field and F10.7 flux data are available for SCs 21–22 and 19–23, respectively, and they are also utilized to get estimates of the Shannon entropy. It is found that the Shannon entropy, a measure of randomness inherent in the SC, is reflected well in the various proxies of the solar activity (viz sunspot, magnetic field, F10.7 flux). The applicability and accuracy of the prediction model equation is verified by way of association of least entropy values with the Dalton minimum. The prediction model equation also provides possible criteria for the occurrence of unusually longer solar minima.

The modulation of electromagnetic ion cyclotron (EMIC) waves by different geomagnetic pulsations is known to us from both ground and satellite observations. However, their dependence on the EMIC wave characteristics is not well explored. We report a statistical analysis of modulation of EMIC waves by short and long periodicities at the Indian Antarctic station, Maitri (L ≈ 5). We have analyzed the induction coil magnetometer data for the period of 2011–2017 and identified 6,845 EMIC wave events, out of which 5,502 events (80%) clearly showed the presence of short period modulation. These short period modulations are associated with repetitive rising tone EMIC wave emissions. Among these 5,502 EMIC wave events only 2,413 events showed presence of long period modulation, in addition to the short period modulation. Next we have examined the characteristics like start time, end time, peak frequency, frequency extent, maximum power, and dominant short and long periodicities present in each EMIC wave event. Based on the statistical analysis, we found that the dominant short and long periodicities in the EMIC waves are in the range of 1.5–3 min and 10–60 min, respectively. These short period decreases with an increase in the peak frequency of the EMIC wave. It is attributed to the decrease in magnetic field line oscillation period at lower L‐shells. Additionally, we noticed that the stronger EMIC wave events are likely to have a higher peak frequency. All these observed tendencies are examined in light of nonlinear theory, and they are found to be in good agreement. Plain Language Summary: The electromagnetic ion cyclotron (EMIC) waves play an important role in the precipitation of relativistic electrons from the outer radiation belt to the upper atmosphere. Thus, it forms an important component of the magnetospheric research. The modulation of the EMIC waves by different geomagnetic pulsations is known to us from both ground and satellite observations. It is believed that the modulation of the EMIC wave is governed through the modulation of the source region ambient plasma parameters by the ULF geomagnetic pulsations. Therefore it is possible that the modulation periodicities are linked to the EMIC wave characteristics. We examined this aspect using long‐term EMIC wave observations from Indian Antarctic ground station and validated the observed trends using nonlinear theory. Such study is important to improve our understanding about the EMIC wave modulation. Key Points: Short and long periodicities in the electromagnetic ion cyclotron (EMIC) waves are in the range of 1.5–3 min and 10–60 min, respectivelyShort period modulation is common and dependent on EMIC wave frequency such that it has larger values at higher L‐shellsStronger EMIC waves likely to have higher frequency, which is in agreement with nonlinear theory [ABSTRACT FROM AUTHOR]

We have studied the evolution of ion acoustic solitary waves (IASWs) in pulsar wind. The pulsar wind is modelled by considering a weakly relativistic unmagnetized collisionless plasma comprised of relativistic ions and superthermal electrons and positrons. Through fluid simulations, we have demonstrated that the localized ion density perturbations generated in the polar wind plasma can evolve the relativistic IASW pulses. It is found that the concentration of positrons, relativistic factor, superthermality of electrons, and positrons have a significant influence on the dynamical evolution of IASW pulses. Our results may provide insight to understand the evolution of IASW pulses and their role in astrophysical plasmas, especially in the relativistic pulsar winds with supernova outflow, which is responsible for the production of superthermal particles and relativistic ions. [ABSTRACT FROM AUTHOR]

One-dimensional fluid simulation is used to investigate the generation of electron-acoustic solitary waves (EASWs) in three-species plasma. We consider an unmagnetized collisionless plasma consisting of cold electrons, hot electrons, and ions. The Gaussian perturbations in the equilibrium electron and ion densities are used to excite the waves in the plasma. This simulation demonstrates the generation of a series of EASW pulses in this three-species plasma through the process of wave breaking. We investigate the behavior of the ponderomotive potential, frequency, and force associated with electrons and ions during the process of the wave breaking. We observed that the ponderomotive potential of the hot electron, which is the driving species for the electron acoustic waves, peaks at the time of wave breaking. The variation of the maximum ponderomotive force acting spatially on the leading and trailing edges of the hump in the cold and hot electron and ion fluid densities shows the maximum imbalance in the magnitude of the ponderomotive force acting on both sides of the hot electron density hump at the time of wave breaking. This reveals that the imbalanced ponderomotive force acting on the hot electron fluid is responsible for the breaking of the electron acoustic wave in plasma. Furthermore, it is observed that the wave breaking process occurs at an earlier time if the hot electron temperature is increased. [ABSTRACT FROM AUTHOR]

The Van Allen Probes have observed both symmetric and asymmetric bipolar electric field structures in the Earth's inner magnetosphere. In general, the symmetric bipolar structures are identified as electron‐phase space holes, whereas the asymmetric structures are interpreted as electron acoustic double layers (EADLs). The generation mechanism of these EADLs is not entirely understood yet. We have modeled the EADLs observed on 13 November 2012 by Van Allen Probe‐B. We performed a fluid simulation of the EADLs and tracked their formation and evolution in the simulation. We found that the localized depletion and enhancement in the electron populations act as a perturbation to excite the symmetric bipolar electron acoustic solitary waves, which later evolve into the EADLs. The Ponderomotive force is found to be the main driver behind transformation of the symmetric electron acoustic solitary waves to EADLs via formation of the electron acoustic shocks. Key Points: Fluid simulation is performed to study the formation and evolution of asymmetric solitary waves in the Earth's inner magnetospherePonderomotive force modulates the symmetric solitary wave pulses into the asymmetric pulses of double layersElectron acoustic shock‐type waves play an important role in the formation of electron acoustic double layers [ABSTRACT FROM AUTHOR]

We perform fluid simulations to examine the effect of ion thermal velocity on the formation and dynamics of solitary waves in an unmagnetized two-component plasma consisting of ions and electrons. Based on the linear and nonlinear fluid theories, some of the previous studies have reported that the plasma with the electron temperature greater than the ion temperature (i.e., Te > Ti) supports ion acoustic solitary waves (IASWs), whereas the plasma with Te ≪ Ti supports electron acoustic waves (EASWs). In this paper, we have considered a wide range of ion temperatures (with fixed electron temperature) to examine the criteria of temperature and thermal velocities in the generation of EASWs and IASWs in plasmas. Our simulation shows that the plasma with Ti > Te possesses two wave modes depending on the ratio of its thermal velocities. When the ratio of electron to ion thermal velocities R = Vthe/Vthi > 1, the system supports the generation of IASWs, whereas for R < 1, it supports the generation of EASWs. The analysis of characteristics like the amplitude, width, and phase speed of these solitary waves implies that the EASWs have a negative potential, whereas the IASWs have the positive potential. The transition from IASWs to EASWs occurs when the phase speed of the solitary wave exceeds the limiting value of 3 V the . This simulation study presents the detailed investigation of the evolution of EASWs and IASWs generated in plasmas having Ti > Te, which will have implications in modeling such waves in space and laboratory plasmas. [ABSTRACT FROM AUTHOR]

We present a ground observation of modulations of strong electromagnetic ion cyclotron (EMIC) waves by short and long periodicities at Indian Antarctic station, Maitri. The signatures of these waves were evident in the magnetic field variations recorded by an induction coil magnetometer during the interval 4.7–7.2 UT on 17 September 2011, a moderately disturbed day. These waves were preceded by a gradual increase in the solar wind dynamic pressure, which started at 3.88 UT. The discrete rising tone EMIC waves were observed in the Pc1 frequency band (∼0.5–0.9 Hz). The investigation of the periodicities of the observed wave spectrogram shows the presence of short (≈2.4 min) and long (≈39–69 min) periodicities. Our analysis shows that the short periodicities are associated with the Pc5 Ultra Low Frequency (ULF) waves generated by magnetic field line oscillations, while long periodicities might be associated with the ring current drifting ions. A new method, based on the cross‐correlation technique, is adopted to determine sweep rates of the discrete rising tones. The average sweep rates estimated in the range of 0.44–1.9 mHz/s are relatively low as compared to the past reports of sweep rates derived from the satellite observations of EMIC waves. We found that the higher sweep rates are associated with the stronger EMIC waves on the ground, which is in agreement with the theoretical studies. This suggests that the theoretically proposed dependence of sweep rate on strength of EMIC wave in the generation region is retained even during the propagation of these waves to the ground. Key Points: Short‐ and long‐period modulations of EMIC waves are observed at Indian Antarctic station MaitriShort periodicities are linked with Pc5 waves generated due to field line oscillations, and long periodicities with ring current drifting ionsHigher sweep rates are associated with stronger EMIC rising tone emissions on ground [ABSTRACT FROM AUTHOR]

Observations from various interplanetary and other spacecraft missions evince that superthermal distributions are omnipresent in the solar wind and near Earth's plasma environment. These observations confirm the presence of coherent bipolar electric field pulses. In phase space, these electric field structures are observed as electron holes (EHs) or ion holes. Trapping of particles in a potential well causes the formation of such structures and is generally studied using the Bernstein-Greene-Kruskal approach. The literature on these structures encompasses the trapped electron distribution function and physically plausible regions. In this paper, we focus on the effects of the width and amplitude of wave potential on electron trapping in thermal and superthermal plasmas. It can be observed that both an increase in the width and the amplitude of wave potential cause an augmentation in the trapping of particles. The amplitude plays a dominant role in the trapping of maximum energetic particles, whereas the width plays a role in deciding the density of particles at the center of the EHs. We found that there exists an upper limit for the stability region of EHs defined by the width-amplitude relation. Additionally, it is noticed that the superthermal plasma does not impose restriction on the presence of electron holes with a width less than the electron Debye length. [ABSTRACT FROM AUTHOR]

Recent studies using satellite observations have reported that subpacket structures play an important role in determining the characteristics of electromagnetic ion cyclotron (EMIC) rising/falling tone emissions. The purpose of the present study is to investigate the subpacket structure characteristics in the ground observations of the EMIC waves. It will help us understand the effect of propagation on the EMIC subpacket structures. The induction coil magnetometer observations from Maitri, Antarctica (Geog. 70.77°S, 11.75°E, Geomag. 63.11°S, 53.59°E, L = 5), are used. Six quiet time EMIC events during 2015–2016 are analyzed and their details are presented. Based on their frequency extent in the power spectrum, four (two) events are speculated to be linked with proton (helium) band EMIC waves. For these events, the EMIC rising tone occurrence periods are estimated to be 1.9–6.7 min. Our analysis suggests that the amplitude‐frequency dependence of EMIC subpacket structures is less significantly affected during their prorogation to the ground. Overall, it is found that more than 70% of the time the EMIC waves are right‐handed elliptical polarized. An interesting feature is that the duration of the subpacket structure is found to be directly proportional to the EMIC wave amplitude. The observed characteristics and tendencies followed by EMIC subpacket structures on the ground are examined in the light of existing nonlinear wave theory and they are in good agreement. The EMIC wave amplitudes on the ground are found to be 16–80 times lower than the expected theoretical estimates of the wave amplitudes in the source region. Key Points: Amplitude‐frequency dependence of EMIC subpacket structures is unaltered during their propagation to the groundEMIC waves observed on the ground are mainly (>70%) associated with right‐handed elliptical polarizationDuration of subpacket structure is found to be proportional to its maximum amplitude [ABSTRACT FROM AUTHOR]

Several spacecraft missions have observed electron holes (EHs) in Earth's and other planetary magnetospheres. These EHs are modeled with the stationary solutions of Vlasov-Poisson equations, obtained by adopting the Bernstein-Greene-Kruskal (BGK) approach. Through the literature survey, we find that the BGK EHs are modelled by using either thermal distribution function or any statistical distribution derived from particular spacecraft observations. However, Maxwell distributions are quite rare in space plasmas; instead, most of these plasmas are superthermal in nature and generally described by kappa distribution. We have developed a one-dimensional BGK model of EHs for space plasma that follows superthermal kappa distribution. The analytical solution of trapped electron distribution function for such plasmas is derived. The trapped particle distribution function in plasma following kappa distribution is found to be steeper and denser as compared to that for Maxwellian distribution. The width-amplitude relation of perturbation for superthermal plasma is derived and allowed regions of stable BGK solutions are obtained. We find that the stable BGK solutions are better supported by superthermal plasmas compared to that of thermal plasmas for small amplitude perturbations. [ABSTRACT FROM AUTHOR]

Recent fluid simulations show that the ponderomotive potentials and ponderomotive frequencies of electrons and ions can be used as proxies to identify steepening and breaking of the ion acoustic solitary waves (IASWs) in plasmas. However, the behavior of these proxies may deviate in the presence of kinetic effects such as particle trapping. We performed one-dimensional particle-in-cell (PIC) simulations to examine the effects of kinetic processes on the behavior of these proxies at the breaking of IASWs in plasmas. The electron and ion equilibrium densities were superimposed by a long-wavelength Gaussian type perturbation, which initially evolves into two IASWs observed as two phase space vortices due to the trapping of electrons in the ion acoustic (IA) potentials. These IASW structures grow due to the steepening of their trailing edges, and later they break into a chain of IA phase space vortices. Each of these vortices is associated with a bipolar electric field resulting in a positive potential structure. We examined the amplitude, width, and phase velocity of the IASWs at their breaking process to clarify their link with the trapping velocity. In addition, we estimated electron and ion ponderomotive potentials and frequencies from the PIC simulations to verify their applicability in identifying wave breaking limit under the kinetic regime. The present study shows that the behavior of the ponderomotive potential during the IA wave breaking process is similar to the one, which is proposed through fluid simulations. We find that IA wave breaking occurs when the maximum trapping velocity of the electron (Vtrap + Vs) exceeds its thermal velocity. The present simulation study shows that both maximum electron trapping velocity and ponderomotive potential can be used to identify the IA wave breaking processes in plasmas. [ABSTRACT FROM AUTHOR]

Space plasmas provide abundant evidence of a highly energetic particle population that results in a long-tailed non-Maxwellian distribution. Such plasmas can be effectively modeled with kappa distribution. The superthermal population in the tail of kappa distribution can have significant effects on the wave dynamical processes. We perform the fluid simulations to examine the effects of superthermal populations on the breaking of the electrostatic ion-acoustic (IA) wave, which is the most fundamental mode, existing in the unmagnetized plasmas. We construct a fluid model for exciting IA waves by employing a kappa distribution function for the superthermal population of electrons along with inertial cold ions (protons). We focused on the nonlinear excitations; in the form of ion acoustic solitary wave (IASW) structures formed through the process of wave breaking, and investigated the role of superthermal electron population in the initiation of the steepening, wave breaking, and propagation characteristics of the IASWs in plasma. From the output of the simulation, we established the criteria for the steepening time based on the variations in the phase velocity of the IASWs. Furthermore, we examined the maximum ponderomotive potential and ponderomotive frequency during the wave breaking process. We found that the time corresponding to the peak in the maximum ponderomotive potential is the time of the initialization of the wave breaking process. We present a detailed investigation of the role of the ponderomotive forces acting on the plasma at each time step, which explains the physics of the wave breaking in nonthermal plasmas. [ABSTRACT FROM AUTHOR]

The head-on collision of multiple counter-propagating coherent phase space structures associated with the ion acoustic solitary waves (IASWs) in plasmas composed of hot electrons and cold ions is studied here by using one-dimensional Particle-in-Cell simulation. The chains of counterpropagating IASWs are generated in the plasma by injecting the Gaussian perturbations in the equilibrium electron and ion densities. The head-on collisions of the counter-propagating electron and ion phase space structures associated with IASWs are allowed by considering the periodic boundary condition in the simulation. Our simulation shows that the phase space structures are less significantly affected by their collision with each other. They emerge out from each other by retaining their characteristics, so that they follow soliton type behavior. We also find that the electrons trapped within these IASW potentials are accelerated, while the ions are decelerated during the course of their collisions. [ABSTRACT FROM AUTHOR]

Wave breaking is a ubiquitous nonlinear phenomenon in plasma that is followed by sudden drop of wave amplitude after a wave steepening. We perform fluid simulation of the ion acoustic solitary waves (IASWs) to investigate the start time of the wave steepening and breaking process. This simulation demonstrates that a long wavelength perturbation in the electron and ion equilibrium densities evolves into two long wavelength IASWs. These IASWs steepens and breaks into short wavelength solitary structures, which become stable ion acoustic solitons at later time. From the detailed analysis of simulation output, we accomplish the criteria for steepening and breaking of the IASWs based on the (a) acceleration of IASWs (b) balance between maximum potential energy and the maximum electron kinetic energy. Furthermore, we examined the ponderomotive potential and the ponderomotive frequency of the electrons and ions during the process of the generation, steepening and breaking of these IASWs. It is observed that the maximum ponderomotive potential of both electrons and ions enhances during the steepening and attains the maximum close to the breaking of the IASWs. The simulation shows that the electron (ion) average ponderomotive frequency is considerably higher than the electron plasma frequency in the initial phase of generation of IASWs, which rapidly oscillates and approaches to frequencies much smaller than electron (ion) plasma frequency. These ponderomotive frequencies remain unchanged until the start of steepening of the IASWs; however, both frequencies are found to increase during the steepening and breaking of these IASWs. Based on this information, we propose that the ponderomotive potential and ponderomotive frequencies of electrons and ions can be used as proxies to determine the steepening and breaking time of the IASWs. We find that the onset time of the wave breaking varies inversely with the thermal velocity of the electrons and the amplitude of the initial density perturbation (IDP), while it is directly proportional to the width of the IDP. It is also noted that the number of solitons formed in the system and their characteristics depends on the electron temperature, width, and amplitude of the IDP. [ABSTRACT FROM AUTHOR]

"Supersolitons," the structures associated with the stationary solitary solutions with the Mach number greater than those associated with the double layers, were introduced in 2012. Later, many researchers have reported the existence domain of the supersolitons in different plasma constituents. However, their evolutionary dynamical behavior and stability were main concerns and were not yet explored. We performed fluid simulation of ion acoustic supersolitons in a plasma containing two-temperature electrons having kappa distributions in the presence of cold fluid ions. Our simulation shows that a specific form of the initial perturbation in the equilibrium electron and ion densities can evolve into ion acoustic supersolitons, which maintain their shape and size during their propagation. This is first-ever simulation to confirm the stability of the supersolitons that opens a new era in the field of solitary wave structures in space and laboratory plasmas. [ABSTRACT FROM AUTHOR]

One-dimensional fluid simulation is performed for the unmagnetized plasma consisting of cold fluid ions and superthermal electrons. Such a plasma system supports the generation of ion acoustic (IA) waves. A standard Gaussian type perturbation is used in both electron and ion equilibrium densities to excite the IA waves. The evolutionary profiles of the IA waves are obtained by varying the superthermal index and the amplitude of the initial perturbation. This simulation demonstrates that the amplitude of the initial perturbation and the superthermal index play an important role in determining the time evolution and the characteristics of the generated IA waves. The initial density perturbation in the system creates charge separation that drives the finite electrostatic potential in the system. This electrostatic potential later evolves into the dispersive and nondispersive IA waves in the simulation system. The density perturbation with the amplitude smaller than 10% of the equilibrium plasma density evolves into the dispersive IA waves, whereas larger density perturbations evolve into both dispersive and nondispersive IA waves for lower and higher superthermal index. The dispersive IA waves are the IA oscillations that propagate with constant ion plasma frequency, whereas the nondispersive IA waves are the IA solitary pulses (termed as IA solitons in the stability region) that propagate with the constant wave speed. The characteristics of the stable nondispersive IA solitons are found to be consistent with the nonlinear fluid theory. To the best of our knowledge, this is the first fluid simulation study that has considered the superthermal distributions for the plasma species to model the electrostatic solitary waves. [ABSTRACT FROM AUTHOR]

We perform one-dimensional fluid simulation of ion acoustic (IA) solitons propagating parallel to the magnetic field in electron-ion plasmas by assuming a large system length. To model the initial density perturbations (IDP), we employ a KdV soliton type solution. Our simulation demonstrates that the generation mechanism of IA solitons depends on the wavelength of the IDP. The short wavelength IDP evolve into two oppositely propagating identical IA solitons, whereas the long wavelength IDP develop into two indistinguishable chains of multiple IA solitons through a wave breaking process. The wave breaking occurs close to the time when electrostatic energy exceeds half of the kinetic energy of the electron fluid. The wave breaking amplitude and time of its initiation are found to be dependent on characteristics of the IDP. The strength of the IDP controls the number of IA solitons in the solitary chains. The speed, width, and amplitude of IA solitons estimated during their stable propagation in the simulation are in good agreement with the nonlinear fluid theory. This fluid simulation is the first to confirm the validity of the general nonlinear fluid theory, which is widely used in the study of solitary waves in laboratory and space plasmas. [ABSTRACT FROM AUTHOR]