Jovo Vranjes - Academia.edu (original) (raw)
Papers by Jovo Vranjes
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2002
Astronomy and Astrophysics, 1999
The problem of nonlinear self-organization of perturbations in differentially rotating, nonunifor... more The problem of nonlinear self-organization of perturbations in differentially rotating, nonuniform, gravitating systems is studied. Two types of stationary nonlinear solutions, in the form of tripolar vortices and vortex chains of gravitational potential and density, dependent on the spatial profiles of the basic state quantities, are found. They propagate with a constant velocity perpendicularly to the basic state gradients, and characteristic time scales for the creation of such vortical structures are shown to be much shorter than the corresponding intervals for gravitational contraction.
AIP Conference Proceedings, 2004
ABSTRACT
Physics Letters A, 2004
A quantitative analysis of the image charge effects in dusty plasmas is presented. It is emphasiz... more A quantitative analysis of the image charge effects in dusty plasmas is presented. It is emphasized that the electrostatic interaction caused by the induced charge on grains can play an important role in dusty plasmas even in the case when in the equilibrium dust grains are not charged. As an example, the behavior of the ion electrostatic perturbations propagating in a plasma containing static and neutral (i.e., uncharged) dust grains is examined. A dispersion equation describing a dispersive and always unstable ion wave is obtained. Both the wave dispersion and the instability are a direct consequence of the image charge effect.
Physica Scripta, 2002
The pulsational mode of gravitational collapse of a dusty plasma is studied in the present work.W... more The pulsational mode of gravitational collapse of a dusty plasma is studied in the present work.We ¢nd that the grain charge £uctuation de¢nes a parameter regime in which pulsational mode of gravitational collapse (PMGC), which is a consequence of the gravito-electrostatic coupling, is permitted, and outside such a parameter regime, usual Jeans mode ensues. Therefore, grain charge £uctuations may play an important role in deciding which of the two modes, namely PMGC or usual Jeans instability of a collapsing cloud will be important.We ¢nd that the growth rate of Jeans instability is not very sensitive to the grain charge £uctuations.
AIP Conference Proceedings, 2004
Perturbations propagating obliquely to the magnetic field lines are studied in a cylindric magnet... more Perturbations propagating obliquely to the magnetic field lines are studied in a cylindric magnetized dusty plasma configuration. A set of two coupled equations describing the perturbed electrostatic and gravity potentials in a radially nonuniform plasma is derived. The equations are discussed and solved in two limits, without and with the self-gravity effects included. Without the gravity the corresponding equation for
Physical Review E, 2015
It is shown that the universally unstable kinetic drift wave in an electron-ion plasma can very e... more It is shown that the universally unstable kinetic drift wave in an electron-ion plasma can very effectively be suppressed by adding an extra flowing ion (or plasma) population. The effect of the flow of the added ions is essential, their response is of the type (v ph − v f 0) exp[−(v ph − v f 0) 2 ], where v f 0 is the flow speed and v ph phase speed parallel to the magnetic field vector. The damping is strong and it is mainly due to this ion exponential term, and this remains so for v f 0 < v ph .
Monthly Notices of the Royal Astronomical Society, 2014
Viscosity is discussed in multicomponent partially and fully ionized plasma, and its effects on t... more Viscosity is discussed in multicomponent partially and fully ionized plasma, and its effects on two very different waves (Alfvén and Langmuir) in solar atmosphere. A full set of viscosity coefficients is presented which includes coefficients for electrons, protons and hydrogen atoms. These are applied to layers with mostly magnetized protons in solar chromosphere where the Alfvén wave could in principle be expected. The viscosity coefficients are calculated and presented graphically for the altitudes between 700 and 2200 km, and required corresponding cross-sections for various types of collisions are given in terms of altitude. It is shown that in chromosphere the viscosity plays no role for the Alfvén wave, which is only strongly affected by ion friction with neutrals. In corona, assuming the magnetic field of a few Gauss, the Alfvén wave is more affected by ion viscosity than by ion-electron friction only for wavelengths shorter that 1-30 km, dependent on parameters and assuming the perturbed magnetic field of 1 per cent of its equilibrium value. For the Langmuir wave the viscosity-friction interplay in chromosphere is shown to be dependent on altitude and on wavelengths. In corona, the viscosity is the main dissipative mechanism acting on the Langmuir mode.
Physical Review E, 2003
It is suggested that low-frequency drift waves can play an important role in the dynamics of elec... more It is suggested that low-frequency drift waves can play an important role in the dynamics of electronpositron plasmas comprising some concentration of ions. In the electromagnetic case the drift wave couples with the shear Alfvén wave in an electron-positron-ion plasma. The drift wave frequency can be very low in such plasmas depending on the concentration and density scale lengths of the plasma components. In the nonlinear regime these waves can give rise to dipolar vortices in both electrostatic and electromagnetic limits. The velocity of the nonlinear structure turns out to be different compared to the case of an electron-ion plasma.
AIP Conference Proceedings, 2008
Laboratory plasma-some examples Space plasma Streaming bounded plasma Plasma with radial and axia... more Laboratory plasma-some examples Space plasma Streaming bounded plasma Plasma with radial and axial density gradient Concluding remarks • The structures observed in helium plasmas evolving in time and rotating in the poloidal cross-section with a period of about 100μs. • Monopolar vortices + dipolar vortices. • Dipole: two components rotate around their centers in opposite directions. The whole structure rotates in poloidal direction. • Generated mainly in the region where the magnetic field curvature is opposite to the density gradient, that is in most of the region outside the centre of the cross-section. i Large bursty flux events occur at the vortex separatrices whenever a double vortex in the potential is formed. i When they occur, they cover most of the plasma cross-section.
AIP Conference Proceedings, 2009
ABSTRACT The heating of the solar corona is discussed within both frameworks of kinetic and fluid... more ABSTRACT The heating of the solar corona is discussed within both frameworks of kinetic and fluid drift wave theory. It is shown that the basic ingredient necessary for the heating is the presence of the background density gradients in the direction perpendicular to the magnetic field vector. These gradients are a source of free energy for the electrostatic instabilities. Strongly growing modes are found for some typical coronal plasma parameters. The instabilities a) imply the presence of electric fields that can accelerate the plasma particles in both the perpendicular and the parallel direction with respect to the magnetic field vector, and b) can stochastically heat ions. The stochastic heating i) is due to the electrostatic nature of the waves, ii) is more effective on ions than on electrons, iii) acts predominantly in the perpendicular direction, iv) heats heavier ions more efficiently than lighter ions, and v) may easily provide a drift wave heating rate that is orders of magnitude above the value that is presently believed to be sufficient for heating the solar corona.
AIP Conference Proceedings, 2008
... Pandey, BP [Department of Physics, Macquarie University, Sydney, NSW 2109 (Australia)] ; Vran... more ... Pandey, BP [Department of Physics, Macquarie University, Sydney, NSW 2109 (Australia)] ; Vranjes, J. [Center for Plasma Astrophysics, Celestijnenlaan 200B, 3001 Leuven (Belgium) and Faculte des Sciences Appliquees, avenue FD Roosevelt 50, 1050 Bruxelles (Belgium)]. ...
AIP Conference Proceedings, 2008
1 page(s
Physics of Plasmas, 2015
The kinetic instability of the obliquely propagating drift magnetosonic wave for temperature anis... more The kinetic instability of the obliquely propagating drift magnetosonic wave for temperature anisotropic low beta plasmas is studied by using the gyro-kinetic model. The interplay between the temperature anisotropy and the density inhomogeneity free energy sources is discussed in order to provide stabilization of drift instability by the temperature anisotropy effect. It is shown that the anisotropy suppresses the growth rate when the anisotropy ratio A e;i ð¼ T ?ðe;iÞ =T kðe;iÞ Þ is greater than unity, whereas it enhances the growth rate for A e;i < 1. Comparison of kinetic instability with reactive instability [Naim et al., Phys. Plasmas 21, 102112 (2014)] and the scaling of growth time with the diffusion and the anisotropy relaxation times are presented. Additionally, the stability analysis applicable to a wide range of plasma parameters is also performed.
New Aspects of Plasma Physics, 2008
ABSTRACT
Physics of Plasmas, 2001
Nonlinear electromagnetic perturbations in a nonuniform plasma are studied in the presence of non... more Nonlinear electromagnetic perturbations in a nonuniform plasma are studied in the presence of nonuniform flows that are aligned either perpendicular or parallel to the ambient magnetic field lines. Coherent structures with typical spatial scales of the order of the electron skin depth are found in the form of a stationary tripolar vortex, and for spatial scales of the order of the electron Larmor radius at the ion temperature in the form of a vortex chain. In both cases, the structures are driven and carried by the plasma flow. In the case of a parallel flow, the dipolar vortex propagates perpendicular to the field lines. For plasma in the Earth’s magnetotail, the solutions presented here should be expected at spatial scales of the order of about 10–20 km.
The 30th International Conference on Plasma Science, 2003. ICOPS 2003. IEEE Conference Record - Abstracts.
ABSTRACT
Meeting Abstracts of the Physical Society of Japan (Nihon Butsuri Gakkai koen gaiyoshu), 2002
Astronomy and Astrophysics, 1999
The problem of nonlinear self-organization of perturbations in differentially rotating, nonunifor... more The problem of nonlinear self-organization of perturbations in differentially rotating, nonuniform, gravitating systems is studied. Two types of stationary nonlinear solutions, in the form of tripolar vortices and vortex chains of gravitational potential and density, dependent on the spatial profiles of the basic state quantities, are found. They propagate with a constant velocity perpendicularly to the basic state gradients, and characteristic time scales for the creation of such vortical structures are shown to be much shorter than the corresponding intervals for gravitational contraction.
AIP Conference Proceedings, 2004
ABSTRACT
Physics Letters A, 2004
A quantitative analysis of the image charge effects in dusty plasmas is presented. It is emphasiz... more A quantitative analysis of the image charge effects in dusty plasmas is presented. It is emphasized that the electrostatic interaction caused by the induced charge on grains can play an important role in dusty plasmas even in the case when in the equilibrium dust grains are not charged. As an example, the behavior of the ion electrostatic perturbations propagating in a plasma containing static and neutral (i.e., uncharged) dust grains is examined. A dispersion equation describing a dispersive and always unstable ion wave is obtained. Both the wave dispersion and the instability are a direct consequence of the image charge effect.
Physica Scripta, 2002
The pulsational mode of gravitational collapse of a dusty plasma is studied in the present work.W... more The pulsational mode of gravitational collapse of a dusty plasma is studied in the present work.We ¢nd that the grain charge £uctuation de¢nes a parameter regime in which pulsational mode of gravitational collapse (PMGC), which is a consequence of the gravito-electrostatic coupling, is permitted, and outside such a parameter regime, usual Jeans mode ensues. Therefore, grain charge £uctuations may play an important role in deciding which of the two modes, namely PMGC or usual Jeans instability of a collapsing cloud will be important.We ¢nd that the growth rate of Jeans instability is not very sensitive to the grain charge £uctuations.
AIP Conference Proceedings, 2004
Perturbations propagating obliquely to the magnetic field lines are studied in a cylindric magnet... more Perturbations propagating obliquely to the magnetic field lines are studied in a cylindric magnetized dusty plasma configuration. A set of two coupled equations describing the perturbed electrostatic and gravity potentials in a radially nonuniform plasma is derived. The equations are discussed and solved in two limits, without and with the self-gravity effects included. Without the gravity the corresponding equation for
Physical Review E, 2015
It is shown that the universally unstable kinetic drift wave in an electron-ion plasma can very e... more It is shown that the universally unstable kinetic drift wave in an electron-ion plasma can very effectively be suppressed by adding an extra flowing ion (or plasma) population. The effect of the flow of the added ions is essential, their response is of the type (v ph − v f 0) exp[−(v ph − v f 0) 2 ], where v f 0 is the flow speed and v ph phase speed parallel to the magnetic field vector. The damping is strong and it is mainly due to this ion exponential term, and this remains so for v f 0 < v ph .
Monthly Notices of the Royal Astronomical Society, 2014
Viscosity is discussed in multicomponent partially and fully ionized plasma, and its effects on t... more Viscosity is discussed in multicomponent partially and fully ionized plasma, and its effects on two very different waves (Alfvén and Langmuir) in solar atmosphere. A full set of viscosity coefficients is presented which includes coefficients for electrons, protons and hydrogen atoms. These are applied to layers with mostly magnetized protons in solar chromosphere where the Alfvén wave could in principle be expected. The viscosity coefficients are calculated and presented graphically for the altitudes between 700 and 2200 km, and required corresponding cross-sections for various types of collisions are given in terms of altitude. It is shown that in chromosphere the viscosity plays no role for the Alfvén wave, which is only strongly affected by ion friction with neutrals. In corona, assuming the magnetic field of a few Gauss, the Alfvén wave is more affected by ion viscosity than by ion-electron friction only for wavelengths shorter that 1-30 km, dependent on parameters and assuming the perturbed magnetic field of 1 per cent of its equilibrium value. For the Langmuir wave the viscosity-friction interplay in chromosphere is shown to be dependent on altitude and on wavelengths. In corona, the viscosity is the main dissipative mechanism acting on the Langmuir mode.
Physical Review E, 2003
It is suggested that low-frequency drift waves can play an important role in the dynamics of elec... more It is suggested that low-frequency drift waves can play an important role in the dynamics of electronpositron plasmas comprising some concentration of ions. In the electromagnetic case the drift wave couples with the shear Alfvén wave in an electron-positron-ion plasma. The drift wave frequency can be very low in such plasmas depending on the concentration and density scale lengths of the plasma components. In the nonlinear regime these waves can give rise to dipolar vortices in both electrostatic and electromagnetic limits. The velocity of the nonlinear structure turns out to be different compared to the case of an electron-ion plasma.
AIP Conference Proceedings, 2008
Laboratory plasma-some examples Space plasma Streaming bounded plasma Plasma with radial and axia... more Laboratory plasma-some examples Space plasma Streaming bounded plasma Plasma with radial and axial density gradient Concluding remarks • The structures observed in helium plasmas evolving in time and rotating in the poloidal cross-section with a period of about 100μs. • Monopolar vortices + dipolar vortices. • Dipole: two components rotate around their centers in opposite directions. The whole structure rotates in poloidal direction. • Generated mainly in the region where the magnetic field curvature is opposite to the density gradient, that is in most of the region outside the centre of the cross-section. i Large bursty flux events occur at the vortex separatrices whenever a double vortex in the potential is formed. i When they occur, they cover most of the plasma cross-section.
AIP Conference Proceedings, 2009
ABSTRACT The heating of the solar corona is discussed within both frameworks of kinetic and fluid... more ABSTRACT The heating of the solar corona is discussed within both frameworks of kinetic and fluid drift wave theory. It is shown that the basic ingredient necessary for the heating is the presence of the background density gradients in the direction perpendicular to the magnetic field vector. These gradients are a source of free energy for the electrostatic instabilities. Strongly growing modes are found for some typical coronal plasma parameters. The instabilities a) imply the presence of electric fields that can accelerate the plasma particles in both the perpendicular and the parallel direction with respect to the magnetic field vector, and b) can stochastically heat ions. The stochastic heating i) is due to the electrostatic nature of the waves, ii) is more effective on ions than on electrons, iii) acts predominantly in the perpendicular direction, iv) heats heavier ions more efficiently than lighter ions, and v) may easily provide a drift wave heating rate that is orders of magnitude above the value that is presently believed to be sufficient for heating the solar corona.
AIP Conference Proceedings, 2008
... Pandey, BP [Department of Physics, Macquarie University, Sydney, NSW 2109 (Australia)] ; Vran... more ... Pandey, BP [Department of Physics, Macquarie University, Sydney, NSW 2109 (Australia)] ; Vranjes, J. [Center for Plasma Astrophysics, Celestijnenlaan 200B, 3001 Leuven (Belgium) and Faculte des Sciences Appliquees, avenue FD Roosevelt 50, 1050 Bruxelles (Belgium)]. ...
AIP Conference Proceedings, 2008
1 page(s
Physics of Plasmas, 2015
The kinetic instability of the obliquely propagating drift magnetosonic wave for temperature anis... more The kinetic instability of the obliquely propagating drift magnetosonic wave for temperature anisotropic low beta plasmas is studied by using the gyro-kinetic model. The interplay between the temperature anisotropy and the density inhomogeneity free energy sources is discussed in order to provide stabilization of drift instability by the temperature anisotropy effect. It is shown that the anisotropy suppresses the growth rate when the anisotropy ratio A e;i ð¼ T ?ðe;iÞ =T kðe;iÞ Þ is greater than unity, whereas it enhances the growth rate for A e;i < 1. Comparison of kinetic instability with reactive instability [Naim et al., Phys. Plasmas 21, 102112 (2014)] and the scaling of growth time with the diffusion and the anisotropy relaxation times are presented. Additionally, the stability analysis applicable to a wide range of plasma parameters is also performed.
New Aspects of Plasma Physics, 2008
ABSTRACT
Physics of Plasmas, 2001
Nonlinear electromagnetic perturbations in a nonuniform plasma are studied in the presence of non... more Nonlinear electromagnetic perturbations in a nonuniform plasma are studied in the presence of nonuniform flows that are aligned either perpendicular or parallel to the ambient magnetic field lines. Coherent structures with typical spatial scales of the order of the electron skin depth are found in the form of a stationary tripolar vortex, and for spatial scales of the order of the electron Larmor radius at the ion temperature in the form of a vortex chain. In both cases, the structures are driven and carried by the plasma flow. In the case of a parallel flow, the dipolar vortex propagates perpendicular to the field lines. For plasma in the Earth’s magnetotail, the solutions presented here should be expected at spatial scales of the order of about 10–20 km.
The 30th International Conference on Plasma Science, 2003. ICOPS 2003. IEEE Conference Record - Abstracts.
ABSTRACT