E-Print Archive

There are 3897 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
Electron plasma wake field acceleration in solar coronal and chromospheric plasmas  

David Tsiklauri   Submitted: 2017-06-19 08:01

Three dimensional, particle-in-cell, fully electromagnetic simulations of electron plasma wake field acceleration applicable to solar atmosphere are presented. It is established that injecting driving and trailing electron bunches into solar coronal and chromospheric plasmas, results in electric fields (-(20-5)?106 V/m), leading to acceleration of the trailing bunch up to 52 MeV, starting from initial 36 MeV. The results provide one of potentially important mechanisms for the extreme energetic solar flare electrons, invoking plasma wake field acceleration.

Authors: David Tsiklauri
Projects: None

Publication Status: accepted for publication in Phys. Plasmas (July 2017 issue)
Last Modified: 2017-06-20 16:12
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Collisionless, phase-mixed, dispersive, Gaussian Alfvén pulse in transversely inhomogeneous plasma  

David Tsiklauri   Submitted: 2016-12-22 10:19

In the previous works harmonic, phase-mixed, Alfvén wave dynamics was considered both in the kinetic and magnetohydrodynamic regimes. Up today only magnetohydrodynamic, phase-mixed, Gaussian Alfvén pulses were investigated. In the present work we extend this into kinetic regime. Here phase-mixed, Gaussian Alfvén pulses are studied, which are more appropriate for solar flares, than harmonic waves, as the flares are impulsive in nature. Collisionless, phase-mixed, dispersive, Gaussian Alfvén pulse in transversely inhomogeneous plasma is investigated by particle-in-cell (PIC) simulations and by an analytical model. The pulse is in inertial regime with plasma beta less than electron-to-ion mass ratio and has a spatial width of 12 ion inertial length. The linear analytical model predicts that the pulse amplitude decrease is described by the linear Korteweg de Vries (KdV) equation. The numerical and analytical solution of the linear KdV equation produces the pulse amplitude decrease in time as t-1. The latter scaling law is corroborated by full PIC simulations. It is shown that the pulse amplitude decrease is due to dispersive effects, while electron acceleration is due to Landau damping of the phase-mixed waves. The established amplitude decrease in time as t-1 is different from the MHD scaling of t-3/2. This can be attributed to the dispersive effects resulting in the different scaling compared to MHD, where the resistive effects cause the damping, in turn, enhanced by the inhomogeneity. Reducing background plasma temperature and increase in ion mass yields more efficient particle acceleration.

Authors: D. Tsiklauri
Projects:

Publication Status: Phys. Plasmas 23, 122906 (2016) doi: 10.1063/1.4972574
Last Modified: 2017-01-04 12:18
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The effect of longitudinal density gradient on electron plasma wake field acceleration  

David Tsiklauri   Submitted: 2016-11-18 05:51

3-, 2- and 1-dimensional, particle-in-cell, fully electromagnetic simulations of electron plasma wake field acceleration in the blow out regime are presented. Earlier results are extended by (i) studying the effect of longitudinal density gradient; (ii) avoiding use of co-moving simulation box; (iii) inclusion of ion motion; and (iv) studying fully electromagnetic plasma wake fields. It is established that injecting driving and trailing electron bunches into a positive density gradient of ten-fold increasing density over 10 cm long Lithium vapor plasma, results in spatially more compact and three times larger, compared to the uniform density case, electric fields (-6.4 x 1010 V/m), leading to acceleration of the trailing bunch up to 24.4 GeV (starting from initial 20.4 GeV), with an energy transfer efficiencies from leading to trailing bunch of 75 percent. In the uniform density case -2.5 x 1010 V/m wake is created leading to acceleration of the trailing bunch up to 22.4 GeV, with an energy transfer efficiencies of 65 percent. It is also established that injecting the electron bunches into a negative density gradient of ten-fold decreasing density over 10 cm long plasma, results in spatially more spread and 2.5 smaller electric fields (-1.0 x 1010 V/m), leading to a weaker acceleration of the trailing bunch up to 21.4 GeV, with an energy transfer efficiencies of 45 percent. It is shown that two-dimensional simulation results are substantially different from the three-dimensional ones, showing only 10 percent efficiency of trailing bunch acceleration, while in one-dimensional case no acceleration is seen. Inclusion of ion motions into consideration shows that in the plasma wake ion number density can increase over few times the background value. We also show that transverse electromagnetic fields in plasma wake are of the same order as the longitudinal (electrostatic) ones. Applications of this mechanism to solar coronal flare MeV electron re-acceleration will be also explored.

Authors: David Tsiklauri
Projects:

Publication Status: Proc. Roy. Soc. A, 472, 20160630 (2016), DOI:10.1098/rspa.2016.0630
Last Modified: 2016-12-28 11:40
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Particle-in-cell simulations of the relaxation of electron beams in inhomogeneous solar wind plasmas  

David Tsiklauri   Submitted: 2016-11-18 05:42

Previous theoretical considerations of electron beam relaxation in inhomogeneous plasmas have indicated that the effects of the irregular solar wind may account for the poor agreement of homogeneous modelling with the observations. Quasi-linear theory and Hamiltonian models based on Zakharov?s equations have indicated that when the level of density fluctuations is above a given threshold, density irregularities act to de-resonate the beam?plasma interaction, restricting Langmuir wave growth on the expense of beam energy. This work presents the first fully kinetic particle-in-cell (PIC) simulations of beam relaxation under the influence of density irregularities. We aim to independently determine the influence of background inhomogeneity on the beam?plasma system, and to test theoretical predictions and alternative models using a fully kinetic treatment. We carry out one-dimensional (1-D) PIC simulations of a bump-on-tail unstable electron beam in the presence of increasing levels of background inhomogeneity using the fully electromagnetic, relativistic EPOCH PIC code. We find that in the case of homogeneous background plasma density, Langmuir wave packets are generated at the resonant condition and then quasi-linear relaxation leads to a dynamic increase of wavenumbers generated. No electron acceleration is seen ? unlike in the inhomogeneous experiments, all of which produce high-energy electrons. For the inhomogeneous experiments we also observe the generation of backwards-propagating Langmuir waves, which is shown directly to be due to the refraction of the packets off the density gradients. In the case of higher-amplitude density fluctuations, similar features to the weaker cases are found, but also packets can also deviate from the expected dispersion curve in (omega,k)-space due to nonlinearity. Our fully kinetic PIC simulations broadly confirm the findings of quasi-linear theory and the Hamiltonian model based on Zakharov?s equations. Strong density fluctuations modify properties of excited Langmuir waves altering their dispersion properties.

Authors: J.O. Thurgood, D. Tsiklauri
Projects:

Publication Status: J. Plasma Phys. 82, 905820604 (2016), doi:10.1017/S0022377816000970
Last Modified: 2016-12-28 11:40
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Role of electron inertia and reconnection dynamics in a stressed X-point collapse with a guide-field  

David Tsiklauri   Submitted: 2016-11-18 05:30

Aims. In previous simulations of collisionless 2D magnetic reconnection it was consistently found that the term in the generalised Ohm?s law that breaks the frozen-in condition is the divergence of the electron pressure tensor?s non-gyrotropic components. The motivation for this study is to investigate the effect of the variation of the guide-field on the reconnection mechanism in simulations of X-point collapse, and the related changes in reconnection dynamics. Methods. A fully relativistic particle-in-cell (PIC) code was used to model X-point collapse with a guide-field in two and three spatial dimensions. Results. We show that in a 2D X-point collapse with a guide-field close to the strength of the in-plane field, the increased induced shear flows along the diffusion region lead to a new reconnection regime in which electron inertial terms play a dominant role at the X-point. This transition is marked by the emergence of a magnetic island ? and hence a second reconnection site ? as well as electron flow vortices moving along the current sheet. The reconnection electric field at the X-point is shown to exceed all lower guide-field cases for a brief period, indicating a strong burst in reconnection. By extending the simulation to three spatial dimensions it is shown that the locations of vortices along the current sheet (visualised by their Q-value) vary in the out-of-plane direction, producing tilted vortex tubes. The vortex tubes on opposite sides of the diffusion region are tilted in opposite directions, similarly to bifurcated current sheets in oblique tearing-mode reconnection. The tilt angles of vortex tubes were compared to a theoretical estimation and were found to be a good match. Particle velocity distribution functions for different guide-field runs, for 2.5D and 3D simulations, are analysed and compared.

Authors: J. Graf von der Pahlen and D. Tsiklauri
Projects: None

Publication Status: A&A 595, A84 (2016) http://dx.doi.org/10.1051/0004-6361/201628071
Last Modified: 2016-11-21 12:34
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Self-consistent particle-in-cell simulations of fundamental and harmonic plasma radio emission mechanisms  

David Tsiklauri   Submitted: 2015-11-24 07:11

Aims. The simulation of three-wave interaction based plasma emission, thought to be the underlying mechanism for Type III solar radio bursts, is a challenging task requiring fully-kinetic, multi-dimensional models. This paper aims to resolve a contradiction in past attempts, whereby some studies indicate that no such processes occur. Methods. We self-consistently simulate three-waved based plasma emission through all stages by using 2D, fully kinetic, electromagnetic particle-in-cell simulations of relaxing electron beams using the EPOCH2D code. Results. Here we present the results of two simulations; Run 1 (nb/n0 = 0.0057, vb/{Delta}vb = vb/Ve = 16) and Run 2 (nb/n0 = 0.05, vb/{Delta}vb = vb/Ve = 8), which we find to permit and prohibit plasma emission respectively. We show that the possibility of plasma emission is contingent upon the frequency of the initial electrostatic waves generated by the bump-in-tail instability, and that these waves may be prohibited from participating in the necessary three-wave interactions due to frequency conservation requirements. In resolving this apparent contradiction through a comprehensive analysis, in this paper we present the first self-consistent demonstration of fundamental and harmonic plasma emission from a single-beam system via fully kinetic numerical simulation. We caution against simulating astrophysical radio bursts using unrealistically dense beams (a common approach which reduces run time), as the resulting non-Langmiur characteristics of the initial wave modes significantly suppresses emission. Comparison of our results also indicates that, contrary to the suggestions of previous authors, an alternative plasma emission mechanism based on two counter-propagating beams is unnecessary in an astrophysical context.

Authors: J.O. Thurgood, D. Tsiklauri
Projects:

Publication Status: A&A 584, A83 (2015) DOI http://dx.doi.org/10.1051/0004-6361/201527079
Last Modified: 2016-11-30 11:25
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Alfvén wave phase mixing in flows - why over-dense solar coronal open magnetic field structures are cool?  

David Tsiklauri   Submitted: 2015-07-21 15:27

Our magnetohydrodynamic (MHD) simulations and analytical calculations show that, when a background flow is present, mathematical expressions for the Alfvén wave (AW) damping via phase mixing are modified by a following substitution C′A(x)→C′A(x)+V′0(x), where CA and V0 are AW phase and the flow speeds and prime denotes derivative in the direction across the background magnetic field. In uniform magnetic field and over-dense plasma structures, in which CA is smaller compared to surrounding plasma, the flow, that is confined to the structure, in the same direction as the AW, reduces the effect of phase mixing, because on the edges of the structure C′A and V′0 have opposite sign. Thus, the wave damps via phase mixing {it slower} compared to the case without the flow. This is the consequence of the co-directional flow reducing the wave front stretching in the transverse direction. Although, the result is generic and is applicable to different laboratory or astrophysical plasma systems, we apply our finding to address the question why over-dense solar coronal open magnetic field structures (OMFS) are cooler than the background plasma. Observations show that the over-dense OMFS (e.g. solar coronal polar plumes) are cooler than surrounding plasma and that in these structures Doppler broadening of lines is consistent with bulk plasma motions, such as Alfvén waves (AW). If over-dense solar coronal OMFS are heated by AW damping via phase mixing, we conjecture that, co-directional with AW, plasma flow in them, reduces the phase mixing induced heating, thus providing an explanation why they appear cooler than the background.

Authors: D. Tsiklauri
Projects: None

Publication Status: Astron. Astrophys. 586, A95 (2016) DOI http://dx.doi.org/10.1051/0004-6361/201527105
Last Modified: 2016-11-30 11:15
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The effects of ion mass variation and domain size on octupolar out-of-plane magnetic field generation in collisionless magnetic reconnection  

David Tsiklauri   Submitted: 2015-03-19 05:29

J. Graf von der Pahlen and D. Tsiklauri, Phys. Plas. 21, 060705 (2014), established that the generation of octupolar out-of-plane magnetic field structure in a stressed X-point collapse is due to ion currents. The field has a central region, comprising of the well-known qaudrupolar field (quadrupolar components), as well as four additional poles of reversed polarity closer to the corners of the domain (octupolar components). In this extended work, the dependence of the octupolar structure on domain size and ion mass variation is investigated. Simulations show that the strength and spatial structure of the generated octupolar magnetic field is independent of ion to electron mass ratio. Thus showing that ion currents play a significant role in out-of-plane magnetic structure generation in physically realistic scenarios. Simulations of different system sizes show that the width of the octupolar structure remains the same and has a spacial extent of the order of the ion inertial length. The width of the structure thus appears to be independent on boundary condition effects. The length of the octupolar structure however increases for greater domain sizes, prescribed by the external system size. This was found to be a consequence of the structure of the in-plane magnetic field in the outflow region halting the particle flow and thus terminating the in-plane currents that generate the out-of-plane field. The generation of octupolar magnetic field structure is also established in a tearing-mode reconnection scenario. The differences in the generation of the octupolar field and resulting qualitative differences between X-point collapse and tearing-mode are discussed.

Authors: Jan Graf von der Pahlen, David Tsiklauri
Projects:

Publication Status: Phys. Plasmas 22, 032905 (2015) DOI http://dx.doi.org/10.1063/1.4916128
Last Modified: 2016-11-30 11:09
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Octupolar out-of-plane magnetic field structure generation during collisionless magnetic reconnection in a stressed X-point collapse  

David Tsiklauri   Submitted: 2014-06-17 03:19

The out-of-plane magnetic field, generated by fast magnetic reconnection, during collisionless, stressed X-point collapse, was studied with a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code, using both closed (flux conserving) and open boundary conditions on a square grid. It was discovered that the well known quadrupolar structure in the out-of-plane magnetic field gains four additional regions of opposite magnetic polarity, emerging near the corners of the simulation box, moving towards the X-point. The emerging, outer, magnetic field structure has opposite polarity to the inner quadrupolar structure, leading to an overall octupolar structure. Using Ampere's law and integrating electron and ion currents, defined at grid cells, over the simulation domain, contributions to the out-of-plane magnetic field from electron and ion currents were determined. The emerging regions of opposite magnetic polarity were shown to be the result of ion currents. Magnetic octupolar structure is found to be a signature of X-point collapse, rather than tearing mode, and factors relating to potential discoveries in experimental scenarios or space-craft observations are discussed.

Authors: J. Graf von der Pahlen, D. Tsiklauri
Projects:

Publication Status: Phys. Plasmas 21, 060705 (2014); DOI: 10.1063/1.4885378
Last Modified: 2014-07-02 12:59
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The effect of guide-field and boundary conditions on collisionless magnetic reconnection in a stressed X-point collapse  

David Tsiklauri   Submitted: 2014-05-09 07:49

Works of D. Tsiklauri, T. Haruki, Phys. of Plasmas, 15, 102902 (2008) and D. Tsiklauri and T. Haruki, Phys. of Plasmas, 14, 112905, (2007) are extended by inclusion of the out-of-plane magnetic (guide) field. In particular, magnetic reconnection during collisionless, stressed X-point collapse for varying out-of-plane guide-fields is studied using a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code. Cases for both open and closed boundary conditions are investigated, where magnetic flux and particles are lost and conserved respectively. It is found that reconnection rates and out-of-plane currents in the X-point increase more rapidly and peak sooner in the closed boundary case, but higher values are reached in the open boundary case. The normalized reconnection rate is fast: 0.10-0.25. In the open boundary case an increase of guide-field yields later onsets in the reconnection peak rates, while in the closed boundary case initial peak rates occur sooner but are suppressed. The reconnection current increases for low guide-fields but then decreases similarly. In the open boundary case, for guide-fields of the order of the in-plane magnetic field, the generation of electron vortices occurs. Possible causes of the vortex generation, based on the flow of particles in the diffusion region and localized plasma heating, are discussed. Before peak reconnection onset, oscillations in the out-of-plane electric field at the X-point are found, ranging in frequency from approximately 1 to 2 ωpe and coinciding with oscillatory reconnection. These oscillations are found to be part of a larger wave pattern. Mapping the out-of-plane electric field over time and applying 2D Fourier transforms reveals that the waves predominantly correspond to the ordinary mode and may correspond to observable radio waves such as solar radio burst fine structure spikes.

Authors: J. Graf von der Pahlen, D. Tsiklauri
Projects: None

Publication Status: Phys. Plasmas 21, 012901 (2014)
Last Modified: 2014-05-09 17:06
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

3D particle-in-cell simulation of electron acceleration by Langmuir waves in an inhomogeneous plasma  

David Tsiklauri   Submitted: 2014-05-09 07:42

A possible solution to the unexplained high intensity hard x-ray (HXR) emission observable during solar flares was investigated via 3D fully relativistic, electromagnetic particle-in-cell (PIC) simulations with realistic ion to electron mass ratio. A beam of accelerated electrons was injected into a magnetised, Maxwellian, homogeneous and inhomogeneous background plasma. The electron distribution function was unstable to the beam-plasma instability and was shown to generate Langmuir waves, while relaxing to plateau formation. In order to estimate the role of the background density gradient on an unbound (infinite spatial extent) beam, three different scenarios were investigated: a) a uniform density background; b) a weak density gradient, n_R/n_L=3; c) a strong gradient case, n_R/n_L=10, where n_R and n_L denote background electron densities on the left and right edges of the simulation box respectively. The strong gradient case produced the largest fraction of electrons beyond 15 v_th. Further, two cases (uniform and strong gradient background) with spatially localized beam injections were performed aiming to show drifts of the generated Langmuir wave wavenumbers, as suggested in previous studies. For the strong gradient case, the Langmuir wave power is shown to drift to smaller wavenumbers, as found in previous quasi-linear simulations.

Authors: R. Pechhacker, D. Tsiklauri
Projects: None

Publication Status: Phys. Plasmas 21, 012903 (2014)
Last Modified: 2014-05-09 17:06
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Whistler wave generation by non-gyrotropic, relativistic, electron beams  

David Tsiklauri   Submitted: 2014-05-09 07:36

Particle-in-cell code, EPOCH, is used for studying features of the wave component evident to propagate backwards from the front of the non-gyrotropic, relativistic beam of electrons injected in the Maxwellian, magnetised background plasma with decreasing density profile. According to recent findings presented in Tsiklauri (2011), Schmitz & Tsiklauri (2013) and Pechhacker & Tsiklauri (2012), in a 1.5-dimensional magnetised plasma system, the non-gyrotropic beam generates freely escaping electromagnetic radiation with properties similar to the Type-III solar radio bursts. In this study the backwards propagating wave component evident in the perpendicular components of the elecromagnetic field in such a system is presented for the first time. Background magnetic field strength in the system is varied in order to prove that the backwards propagating wave's frequency, prescribed by the whistler wave dispersion relation, is proportional to the specified magnetic field. Moreover, the identified whistlers are shown to be generated by the normal Doppler-shifted relativistic resonance. Large fraction of the energy of the perpendicular electromagnetic field components is found to be carried away by the whistler waves, while a small but sufficient fraction is going into L- and R- electromagnetic modes.

Authors: Marina Skender, David Tsiklauri
Projects: None

Publication Status: Phys. Plasmas 21, 042904 (2014)
Last Modified: 2014-05-09 17:06
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

3D MHD simulation of linearly polarised Alfvén wave dynamics in Arnold-Beltrami-Childress magnetic field  

David Tsiklauri   Submitted: 2014-05-09 07:30

Previous studies [Malara et al ApJ, 533, 523 (2000)] considered small-amplitude Alfvén wave (AW) packets in Arnold-Beltrami-Childress (ABC) magnetic field using WKB approximation. In this work linearly polarised Alfvén wave dynamics in ABC magnetic field via direct 3D MHD numerical simulation is studied for the first time. Gaussian AW pulse with length-scale much shorter than ABC domain length and harmonic AW with wavelength equal to ABC domain length are studied for four different resistivities. While it is found that AWs dissipate quickly in the ABC field, surprisingly, AW perturbation energy increases in time. In the case of the harmonic AW perturbation energy growth is transient in time, attaining peaks in both velocity and magnetic perturbation energies within timescales much smaller than resistive time. In the case of the Gaussian AW pulse velocity perturbation energy growth is still transient in time, attaining a peak within few resistive times, while magnetic perturbation energy continues to grow. It is also shown that the total magnetic energy decreases in time and this is governed by the resistive evolution of the background ABC magnetic field rather than AW damping. On contrary, when background magnetic field is uniform, the total magnetic energy decrease is prescribed by AW damping, because there is no resistive evolution of the background. By considering runs with different amplitudes and by analysing perturbation spectra, possible dynamo action by AW perturbation-induced peristaltic flow and inverse cascade of magnetic energy have been excluded. Therefore, the perturbation energy growth is attributed to a new instability. The growth rate appears to be dependent on the value of the resistivity and spatial scale of the AW disturbance. Thus, when going beyond WKB approximation, AW damping, described by full MHD equations, does not guarantee decrease of perturbation energy.

Authors: D. Tsiklauri
Projects:

Publication Status: Phys. Plasmas 21, 052902 (2014) http://scitation.aip.org/content/aip/journal/pop/21/5/10.1063/1.4875920
Last Modified: 2014-05-14 13:10
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The effect of initial conditions on the electromagnetic radiation generation in type III solar radio bursts  

David Tsiklauri   Submitted: 2013-05-28 01:51

Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [D. Tsiklauri, Phys. Plasmas, 18, 052903 (2011)]. The numerical simulations were carried out using different density profiles and fast electron distribution functions. It is shown that electromagnetic L and R modes are excited by the transverse current, initially imposed on the system. In the course of the simulations no further interaction of the electron beam with the background plasma could be observed.

Authors: H. Schmitz, D. Tsiklauri
Projects: Nobeyama Radioheliograph,Owens Valley Solar Array

Publication Status: Phys. Plasmas 20, 062903 (2013); http://dx.doi.org/10.1063/1.4812453
Last Modified: 2013-07-18 18:45
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The effect of initial conditions on the electromagnetic radiation generation in type III solar radio bursts  

David Tsiklauri   Submitted: 2013-05-28 01:51

Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [D. Tsiklauri, Phys. Plasmas, 18, 052903 (2011)]. The numerical simulations were carried out using different density profiles and fast electron distribution functions. It is shown that electromagnetic L and R modes are excited by the transverse current, initially imposed on the system. In the course of the simulations no further interaction of the electron beam with the background plasma could be observed.

Authors: H. Schmitz, D. Tsiklauri
Projects: Nobeyama Radioheliograph,Owens Valley Solar Array

Publication Status: Phys. Plasmas 20, 062903 (2013)
Last Modified: 2016-11-30 11:12
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Three dimensional particle-in-cell simulation of particle acceleration by circularly polarised inertial Alfvén waves in a transversely inhomogeneous plasma  

David Tsiklauri   Submitted: 2012-08-08 10:03

The process of particle acceleration by left-hand, circularly polarised inertial Alfvén waves (IAW) in a transversely inhomogeneous plasma is studied using 3D particle-in-cell simulation. A cylindrical tube with, transverse to the background magnetic field, inhomogeneity scale of the order of ion inertial length is considered on which IAWs with frequency 0.3 omegaci are launched that are allowed to develop three wavelength. As a result time-varying parallel electric fields are generated in the density gradient regions which accelerate electrons in the parallel to magnetic field direction. Driven perpendicular electric field of IAWs also heats ions in the transverse direction. Such numerical setup is relevant for solar flaring loops and earth auroral zone. This first, 3D, fully-kinetic simulation demonstrates electron acceleration efficiency in the density inhomogeneity regions, along the magnetic field, of the order of 45% and ion heating, in the transverse to the magnetic field direction, of 75%. The latter is a factor of two times higher than the previous 2.5D analogous study and is in accordance with solar flare particle acceleration observations. We find that the generated parallel electric field is localised in the density inhomogeneity region and rotates in the same direction and with the same angular frequency as the initially launched IAW. Our numerical simulations seem also to suggest that the ''knee'' often found in the solar flare electron spectra can alternatively be interpreted as the Landau damping (Cerenkov resonance effect) of IAWs due to the wave-particle interactions.

Authors: D. Tsiklauri
Projects:

Publication Status: Phys. Plasmas 19, 082903 (2012)
Last Modified: 2012-08-15 06:41
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Particle acceleration by circularly and elliptically polarised dispersive Alfvén waves in a transversely inhomogeneous plasma in the inertial and kinetic regimes  

David Tsiklauri   Submitted: 2011-07-07 04:40

Dispersive Alfvén waves (DAWs) offer, an alternative to magnetic reconnection, opportunity to accelerate solar flare particles. We study the effect of DAW polarisation, L-, R-, circular and elliptical, in different regimes inertial and kinetic on the efficiency of particle acceleration. We use 2.5D PIC simulations to study how particles are accelerated when DAW, triggered by a solar flare, propagates in transversely inhomogeneous plasma that mimics solar coronal loop. (i) In inertial regime, fraction of accelerated electrons (along the magnetic field), in density gradient regions is ~20% by the time when DAW develops 3 wavelengths and is increasing to ~30% by the time DAW develops 13 wavelengths. In all considered cases ions are heated in transverse to the magnetic field direction and fraction of the heated particles is ~35%. (ii) The case of R-circular, L- and R- elliptical polarisation DAWs, with the electric field in the non-ignorable transverse direction exceeding several times that of in the ignorable direction, produce more pronounced parallel electron beams and transverse ion beams in the ignorable direction. In the inertial regime such polarisations yield the fraction of accelerated electrons ~20%. In the kinetic regime this increases to ~35%. (iii) The parallel electric field that is generated in the density inhomogeneity regions is independent of m_i/m_e and exceeds the Dreicer value by 8 orders of magnitude. (iv) Electron beam velocity has the phase velocity of the DAW. Thus electron acceleration is via Landau damping of DAWs. For the Alfvén speeds of 0.3c the considered mechanism can accelerate electrons to energies circa 20 keV. (v) The increase of mass ratio from m_i/m_e=16 to 73.44 increases the fraction of accelerated electrons from 20% to 30-35% (depending on DAW polarisation). For the mass ratio m_i/m_e=1836 the fraction of accelerated electrons would be >35%.

Authors: David Tsiklauri
Projects: None

Publication Status: Phys. Plasmas 18, 092903 (2011)
Last Modified: 2011-09-26 07:36
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Heating of solar chromosphere by electromagnetic wave absorption in a plasma slab model  

David Tsiklauri   Submitted: 2010-12-22 04:24

Heating of solar chromosphere by electromagnetic wave absorption in a plasma slab model | The heating of chromospheric inter-network regions by means of the absorption of electromagnetic (EM) waves that originate from the photospheric blackbody radiation is studied in the framework of a plasma slab model. The absorption is provided by the electron-neutral collisions. Given the uncertain nature of the collision cross-section due to the plasma micro-turbulence, it is shown that for plausible physical parameters, the heating flux produced by the absorption of EM waves in the chromosphere is between 20-45% of the chromospheric radiative loss flux requirement. It is also established that there is an optimal value for the collision cross-section, 5x10-18 m2, that produces the maximal heating flux of 1990 W m-2.

Authors: D. Tsiklauri, R. Pechhacker
Projects:

Publication Status: Physics of Plasmas, in press, April 2011 issue
Last Modified: 2011-04-01 09:27
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Heating of solar chromosphere by electromagnetic wave absorption in a plasma slab model  

David Tsiklauri   Submitted: 2010-12-22 04:24

The heating of solar chromospheric inter-network regions by means of theabsorption of electromagnetic (EM) waves that originate from the photosphericblackbody radiation is studied in the framework of a plasma slab model. Theabsorption is provided by the electron-neutral collisions in which electronsoscillate in the EM wave field and electron-neutral collisions damp the EMwave. Given the uncertain nature of the collision cross-section due to theplasma micro-turbulence, it is shown that for plausible physical parameters,the heating flux produced by the absorption of EM waves in the chromosphere isbetween 20 - 45 % of the chromospheric radiative loss flux requirement. It isalso established that there is an optimal value for the collisioncross-section, 5 imes 10-18 m2, that produces the maximal heatingflux of 1990 W m-2.

Authors: D. Tsiklauri, R. Pechhacker
Projects: None

Publication Status: Phys. Plasmas 18, 042901 (2011)
Last Modified: 2011-07-07 04:49
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

An alternative to the plasma emission model: Particle-In-Cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts  

David Tsiklauri   Submitted: 2010-11-26 11:09

1.5D PIC, relativistic, fully electromagnetic (EM) simulations are used tomodel EM wave emission generation in the context of solar type III radiobursts. The model studies generation of EM waves by a super-thermal, hot beamof electrons injected into a plasma thread that contains uniform longitudinalmagnetic field and a parabolic density gradient. In effect, a single magneticline connecting Sun to earth is considered, for which several cases arestudied. (i) We find that the physical system without a beam is stable and onlylow amplitude level EM drift waves (noise) are excited. (ii) The beam injectiondirection is controlled by setting either longitudinal or oblique electroninitial drift speed, i.e. by setting the beam pitch angle. In the case of zeropitch angle, the beam excites only electrostatic, standing waves, oscillatingat plasma frequency, in the beam injection spatial location, and only low levelEM drift wave noise is also generated. (iii) In the case of oblique beam pitchangles, again electrostatic waves with same properties are excited. However,now the beam also generates EM waves with the properties commensurate to typeIII radio bursts. The latter is evidenced by the wavelet analysis of transverseelectric field component, which shows that as the beam moves to the regions oflower density, frequency of the EM waves drops accordingly. (iv) When thedensity gradient is removed, electron beam with an oblique pitch angle stillgenerates the EM radiation. However, in the latter case no frequency decreaseis seen. Within the limitations of the model, the study presents the firstattempt to produce simulated dynamical spectrum of type III radio bursts infully kinetic plasma model. The latter is based on 1.5D non-zero pitch angle(non-gyrotropic) electron beam, that is an alternative to the plasma emissionclassical mechanism.

Authors: David Tsiklauri
Projects: None

Publication Status: Physics of Plasmas 18, 052903 (2011)
Last Modified: 2011-07-07 04:47
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 


[Older Entries]
Key
Go to main E-Print pageGo to main E-Print page.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
Delete AbstractDelete abstract.

Abstracts by Author
Electron plasma wake field acceleration in solar coronal and chromospheric plasmas
Collisionless, phase-mixed, dispersive, Gaussian Alfven pulse in transversely inhomogeneous plasma
The effect of longitudinal density gradient on electron plasma wake field acceleration
Particle-in-cell simulations of the relaxation of electron beams in inhomogeneous solar wind plasmas
Role of electron inertia and reconnection dynamics in a stressed X-point collapse with a guide-field
Self-consistent particle-in-cell simulations of fundamental and harmonic plasma radio emission mechanisms
Alfven wave phase mixing in flows -- why over-dense solar coronal open magnetic field structures are cool?
The effects of ion mass variation and domain size on octupolar out-of-plane magnetic field generation in collisionless magnetic reconnection
Octupolar out-of-plane magnetic field structure generation during collisionless magnetic reconnection in a stressed X-point collapse
The effect of guide-field and boundary conditions on collisionless magnetic reconnection in a stressed X-point collapse
3D particle-in-cell simulation of electron acceleration by Langmuir waves in an inhomogeneous plasma
Whistler wave generation by non-gyrotropic, relativistic, electron beams
3D MHD simulation of linearly polarised Alfven wave dynamics in Arnold-Beltrami-Childress magnetic field
The effect of initial conditions on the electromagnetic radiation generation in type III solar radio bursts
The effect of initial conditions on the electromagnetic radiation generation in type III solar radio bursts
Three dimensional particle-in-cell simulation of particle acceleration by circularly polarised inertial Alfven waves in a transversely inhomogeneous plasma
Particle acceleration by circularly and elliptically polarised dispersive Alfven waves in a transversely inhomogeneous plasma in the inertial and kinetic regimes
Heating of solar chromosphere by electromagnetic wave absorption in a plasma slab model
Heating of solar chromosphere by electromagnetic wave absorption in a plasma slab model
An alternative to the plasma emission model: Particle-In-Cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts
An alternative to the plasma emission model: Particle-in-cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts
Missing bits of the solar jigsaw puzzle: small-scale, kinetic effects in coronal studies
Physics of collisionless reconnection in a stressed X-point collapse
Physics of collisionless phase mixing
A new fast reconnection model in a collisionless regime
Physics of collisionless reconnection in a stressed X-point collapse
Magnetic reconnection during collionless, stressed, X-point collapse using Particle-in-Cell simulation
A minimal model of parallel electric field generation in a transversely inhomogeneous plasma
A fresh look at the heating mechanisms of the solar corona
Phase mixing of shear Alfvén waves as a new mechanism for electron acceleration in collisionless, kinetic plasmas
The Sun as a MHD generator: application of a new heating mechanism for the coronal loops and closed magnetic structures
Particle-In-Cell simulations of circularly polarised Alfven wave phase mixing: a new mechanism for electron acceleration in collisionless plasmas
Phase mixing of a three dimensional magnetohydrodynamic pulse
Phase mixing of a three dimensional magnetohydrodynamic pulse
A Three Dimensional Magnetohydrodynamic Pulse in a Transversely Inhomogeneous Medium
Line-of-sight Effects on Observability of Kink and Sausage Modes in Coronal Structures with Imaging Telescopes
A Weakly Nonlinear Alfv'enic Pulse in a Transversely InhomogeneousMedium
Wide-Spectrum Slow Magnetoacoustic Waves in Coronal Loops

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University