The numerical simulation of the generation of lower-band VLF chorus using a quasi-broadband Vlasov Hybrid Simulation code

AbstractIn this paper, we perform the numerical modelling of lower-band VLF chorus in the earth’s magnetosphere. Assuming parallel propagation the 1d3v code has one spatial dimension z along the ambient magnetic field, which has a parabolic z dependence about the equator. The method used is Vlasov Hybrid Simulation (VHS) also known in the literature as the method of Kinetic Phase Point Trajectories (Nunn in Computer Physics Comms 60:1–25, 1990, J Computational Phys 108(1):180–196, 1993; Kazeminezhad et al. in Phys Rev E67:026704, 2003). The method is straightforward and easy to program, and robust against distribution function filamentation. Importantly, VHS does not invoke unphysical smoothing of the distribution function. Previous versions of the VLF/VHS code had a narrow bandwidth ~ 100 Hz, which enabled simulation of a wide variety of discrete triggered emissions. The present quasi-broadband VHS code has a bandwidth of ~ 3000 Hz, which is far more realistic for the simulation of chorus in its entirety. Further, the quasi-broadband code does not require artificial saturation, and does not need to employ matched filtering to accommodate large spatial frequency gradients. The aim of this paper which has been achieved is to produce VLF chorus Vlasov simulations employing a systematic variety of triggering input signals, namely key down, single pulse, PLHR, and broadband hiss. Graphical Abstract

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The Numerical Simulation of the Generation of Lower Band VLF Chorus Using a Quasi-Broadband Vlasov Hybrid Simulation Code

10.21203/rs.3.rs-783485/v1 ◽

2021 ◽

Author(s):

David Nunn

Keyword(s):

Distribution Function ◽

Hybrid Simulation ◽

Single Pulse ◽

Spatial Dimension ◽

Phase Point ◽

Simulation Code ◽

Lower Band ◽

Parallel Propagation ◽

Narrow Bandwidth ◽

Point Trajectories

Abstract In this paper we perform the numerical modelling of lower band VLF chorus in the earth’s magnetosphere. Assuming parallel propagation the 1d3v code has one spatial dimension z along the ambient magnetic field, which has a parabolic z dependence about the equator. The method used is Vlasov Hybrid Simulation (VHS) also known in the literature as the method of Kinetic Phase Point Trajectories (Nunn 1990,1993; Kazeminezhad et al. 2003). The method is straightforward and easy to program, and robust against distribution function filamentation. Importantly VHS does not invoke unphysical smoothing of the distribution function. Previous versions of the VLF/VHS code had a narrow bandwidth ~100Hz, which enabled simulation of a wide variety of discrete triggered emissions. The present quasi-broadband VHS code has a bandwidth of ~3000Hz, which is far more realistic for the simulation of chorus in its entirety. Further the quasi-broadband code does not require artificial saturation, and does not need to employ matched filtering to accommodate large spatial frequency gradients. The aim of this paper which has been achieved is to produce VLF chorus Vlasov simulations employing a systematic variety of triggering input signals, namely key down, single pulse, PLHR, and broadband hiss.

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Three-dimensional multispecies hybrid simulation of Titan's highly variable plasma environment

Annales Geophysicae ◽

10.5194/angeo-25-117-2007 ◽

2007 ◽

Vol 25 (1) ◽

pp. 117-144 ◽

Cited By ~ 35

Author(s):

S. Simon ◽

A. Boesswetter ◽

T. Bagdonat ◽

U. Motschmann ◽

J. Schuele

Keyword(s):

Plasma Flow ◽

Flow Direction ◽

Three Dimensional ◽

Hybrid Simulation ◽

Slight Modification ◽

Magnetospheric Plasma ◽

Particle Model ◽

Tail Region ◽

Simulation Code ◽

Ion Species

Abstract. The interaction between Titan's ionosphere and the Saturnian magnetospheric plasma flow has been studied by means of a three-dimensional (3-D) hybrid simulation code. In the hybrid model, the electrons form a mass-less, charge-neutralizing fluid, whereas a completely kinetic approach is retained to describe ion dynamics. The model includes up to three ionospheric and two magnetospheric ion species. The interaction gives rise to a pronounced magnetic draping pattern and an ionospheric tail that is highly asymmetric with respect to the direction of the convective electric field. Due to the dependence of the ion gyroradii on the ion mass, ions of different masses become spatially dispersed in the tail region. Therefore, Titan's ionospheric tail may be considered a mass-spectrometer, allowing to distinguish between ion species of different masses. The kinetic nature of this effect is emphasized by comparing the simulation with the results obtained from a simple analytical test-particle model of the pick-up process. Besides, the results clearly illustrate the necessity of taking into account the multi-species nature of the magnetospheric plasma flow in the vicinity of Titan. On the one hand, heavy magnetospheric particles, such as atomic Nitrogen or Oxygen, experience only a slight modification of their flow pattern. On the other hand, light ionospheric ions, e.g. atomic Hydrogen, are clearly deflected around the obstacle, yielding a widening of the magnetic draping pattern perpendicular to the flow direction. The simulation results clearly indicate that the nature of this interaction process, especially the formation of sharply pronounced plasma boundaries in the vicinity of Titan, is extremely sensitive to both the temperature of the magnetospheric ions and the orientation of Titan's dayside ionosphere with respect to the corotating magnetospheric plasma flow.

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Plasma environment of magnetized asteroids: a 3-D hybrid simulation study

Annales Geophysicae ◽

10.5194/angeo-24-407-2006 ◽

2006 ◽

Vol 24 (1) ◽

pp. 407-414 ◽

Cited By ~ 24

Author(s):

S. Simon ◽

T. Bagdonat ◽

U. Motschmann ◽

K.-H. Glassmeier

Keyword(s):

Solar Wind ◽

Three Dimensional ◽

Hybrid Simulation ◽

Interaction Region ◽

Bow Shock ◽

The Other ◽

Simulation Code ◽

Kinetic Effects ◽

Intrinsic Magnetic Moment ◽

The One

Abstract. The interaction of a magnetized asteroid with the solar wind is studied by using a three-dimensional hybrid simulation code (fluid electrons, kinetic ions). When the obstacle's intrinsic magnetic moment is sufficiently strong, the interaction region develops signs of magnetospheric structures. On the one hand, an area from which the solar wind is excluded forms downstream of the obstacle. On the other hand, the interaction region is surrounded by a boundary layer which indicates the presence of a bow shock. By analyzing the trajectories of individual ions, it is demonstrated that kinetic effects have global consequences for the structure of the interaction region.

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Plasma environment of Titan: a 3-D hybrid simulation study

Annales Geophysicae ◽

10.5194/angeo-24-1113-2006 ◽

2006 ◽

Vol 24 (3) ◽

pp. 1113-1135 ◽

Cited By ~ 48

Author(s):

S. Simon ◽

A. Bößwetter ◽

T. Bagdonat ◽

U. Motschmann ◽

K.-H. Glassmeier

Keyword(s):

Plasma Flow ◽

Molecular Nitrogen ◽

Hybrid Simulation ◽

Spherical Geometry ◽

Magnetospheric Plasma ◽

Simulation Code ◽

Plasma Environment ◽

Ion Production ◽

Solar Uv ◽

Magnetohydrodynamic Models

Abstract. Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

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Absorption of ultra-short laser pulses and particle transport in dense targets

Laser and Particle Beams ◽

10.1017/s0263034606060332 ◽

2006 ◽

Vol 24 (2) ◽

pp. 231-234 ◽

Cited By ~ 8

Author(s):

M. SHERLOCK ◽

A. R. BELL ◽

W. ROZMUS

Keyword(s):

Distribution Function ◽

Electron Distribution ◽

Energy Transport ◽

Electron Distribution Function ◽

Planck Equation ◽

Front Surface ◽

Normal Incidence ◽

Laser Pulses ◽

Spatial Dimension ◽

Numerical Code

A new version of the numerical code KALOS has been developed to solve the Vlasov-Fokker-Planck equation for electrons as well as EM wave propagation. KALOS represents the electron distribution function in momentum space by an expansion in spherical harmonics. Its unique features make possible simultaneous investigations of fast electron generation and transport and the collisional evolution of thermal particles, including the return current of cold electrons. We report here on results obtained in one spatial dimension. Absorption of 100fs, 1015W/cm2laser pulses has been studied at normal incidence in sharp-edged dense plasmas. We have studied the effect on absorption of energy transport into the target as well as the deviation of the electron distribution function from Maxwellian. It is shown that it is necessary to take into account collisional heat transport into the target in order to correctly model the absorption rate at the front surface.

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