arXiv subjects

Mridusmita Das

Publications and source records attributed to Mridusmita Das.

3 recordsLinked to original sources

arXiv2025

External charge perturbation in a flowing plasma and electrostatic turbulence

In this work, an 1D electrostatic hybrid-Particle-in-Cell-Monte-Carlo-Collisionh-PIC-MCC) code is used to study the response of a plasma to a moving, external, charged perturbation (debris). We show that the so-called pinned solitons can form only under certain specific conditions through a turbulent regime of the ion-ion counter-streaming electrostatic instability (IICSI). In fact, the pinned solitons are manifestation of the ion phase-space vortices formed around the debris. The simulation shows that the pinned solitons can form only when the debris charge density exceeds a certain value causing the counter-streaming ion velocity to exceed a critical velocity, pushing the instability to a turbulent regime. The effect of debris velocity is also essential for the appearance of pinned soliton as when the debris velocity increases, it causes the widening of the phase space vortices causing well-separated pinned solitons, which merge to form one single soliton when debris velocity reduces to zero. In the opposite extreme, when debris velocity becomes highly supersonic, the vortices are widened up to a limit causing the pinned solitons to disappear altogether. We further show the existence of a Kolmogorov-type energy cascade scaling for this electrostatic turbulence.

physics.plasm-ph↗

arXiv2023

Fast-moving electrostatic solitons in a plasma with turbulence heating

In this work, it is shown that electrostatic solitons in a plasma with turbulent heating of the electrons through an accelerating electric field can form with very high velocities, reaching up to several order of magnitudes larger than the equilibrium ion-sound speed. The possible parameter regime, where this work may be relevant, can be found in the so-called "dead zones" of a protoplanetary disk. Though these zones are stable to magnetorotational instability, the resultant turbulence can in fact heat the electrons making them follow a highly non- Maxwellian velocity distribution. We show that these fast-moving solitons can reach very high velocities. With electron velocity distribution described by the Davydov distribution function, we argue that these solitons can be an effective mechanism for energy equilibration in such a situation through soliton decay and radiation.

physics.plasm-ph↗

arXiv2022

Driven dust-charge fluctuation and chaotic ion dynamics in the plasma sheath and pre-sheath regions

Possible existence of chaotic oscillations in ion dynamics in the sheath and pre-sheath regions of a dusty plasma, induced by externally driven dust-charge fluctuation, is presented in this work. In a complex plasma, dust charge fluctuation occurs continuously with time due to the variation of electron and ions current flowing into the dust particles. In most of the works related to dust-charge fluctuation, theoretically it is assumed that the average dust-charge fluctuation follows the the plasma perturbation, while in reality, the dust-charge fluctuation is a semi-random phenomena, fluctuating about some average value. The very cause of dust-charge fluctuation in a dusty plasma also points to the fact that these fluctuations can be driven externally by changing electron and ion currents to the dust particles. With the help of a \emph{hybrid}-Particle in Cell-Monte Carlo (\emph{h}-PIC-MCC) code in this work, we use the plasma sheath as a candidate for driving the dust-charge fluctuation by periodically exposing the sheath-side wall to UV radiation, causing photoemission of electrons, which in turn drive the dust-charge fluctuation. We show that this \emph{driven} dust-charge fluctuation can induce a chaotic response in the ion dynamics in the sheath and the pre-sheath regions.

physics.plasm-ph↗