G. Ganguli’s research while affiliated with United States Naval Research Laboratory and other places

... Third, laboratory experiments at NRL in the Space Physics Simulation chamber are being performed with only perpendicular flows, and yet, electrostatic soliton-like structures are seen propagating upstream. 31 Our analysis showed that this configuration does not produce solitons for kc s < X i (Fig. 10). Instead, vortex structures are generated. ...

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Orbital debris-generated ion acoustic solitons in isothermal magnetized plasma

... Recent progress toward this goal has been made by the use of a numerical "Green's function" (Omura, Miyashita, et al., 2015;Kubota & Omura, 2018) that gives the nonlinear test-particle response to a given subpacket of chorus and demonstrates that rapid acceleration to megaelectron volt energies is possible. A subpacket of chorus (Foster et al., 2017 andSantolík et al., 2014) is a burst of chorus power within a chorus element where the amplitude varies dramatically on a timescale of the order of 5-10 wave periods and may itself be due to a higher-order nonlinear resonance between the whistler mode wave and the electrons that generate the wave (Crabtree et al., 2017a(Crabtree et al., , 2017b. ...

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Particle Dynamics in the Earth's Radiation Belts: Review of Current Research and Open Questions

... The DuBois et al. experiment was a proof of principle of the theory which had posited that a compressed boundary layer can relax through the emission of a hierarchy of electric field-driven waves starting from above the electron gyrofrequency to much below the ion gyrofrequency and could be the primary source for the observed broadband electrostatic noise. Tejero et al. (2011) and Enloe et al. (2017) have subsequently shown that the plasma compression can also produce electromagnetic emissions but the wave power is primarily concentrated in the electrostatic regime , consistent with the in situ observations (Angelopoulos et al. 1989). These laboratory experiments have elucidated the subtler aspects of the magnetotail dynamics, which would be difficult to discern from in situ measurements alone. ...

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Behavior of compressed plasmas in magnetic fields

... The phase transition in a plasma offers the dusty (complex) plasma as an interesting and developing research field. In past few decades, dusty plasma has contributed a lot in plasma research and it became most significant dynamical process in astrophysical plasma, planetary rings, molecular clouds, interstellar media (ISM), comet tails, Q machine, tokamak, laboratory plasma, etc. [1][2][3][4]. The wave modes and instabilities in two fluid dusty plasma deal with exciting features in these complex systems [5,6]. ...

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Influence of dust charge fluctuation and polarization force on radiative condensation instability of magnetized gravitating dusty plasma

... Acceleration and transport mechanisms of relativistic particles in the geospace environment by nonlinear interaction with chorus emissions have attracted significant attention and have been intensively studied theoretically and numerically [11][12][13]16 , and through spacecraft observations 17,18 . Laboratory experiments [19][20][21][22][23] provide an opportunity for detailed measurements in a controlled environment, thereby helping the understanding of the whistler wave phenomena in space. A levitated superconducting ring coil creates a dipole magnetic field that is common to planetary magnetospheres. ...

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Experimental study on chorus emission in an artificial magnetosphere

... [3][4][5][6][7][8][9][10][11][12][13][14] Recently, the application of weak turbulence theory to the whistler and lower-hybrid frequency regimes has been discussed as an important dynamical process in the near-Earth environment. [15][16][17][18][19][20][21][22] Moreover, Ref. 23 reports circular polarizations for the type III radio bursts close to the Sun as measured using the contemporary Parker Solar Probe (PSP). This implies that the standard plasma emission theory, which is based on the weak turbulence theory for unmagnetized plasmas, should be extended to include the effects of the ambient magnetic field. ...

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Nonlinear susceptibilities for weakly turbulent magnetized plasma: Electromagnetic formalism

... 9 In turbulent plasmas, the excitation of whistler waves can also occur through nonlinear mechanisms such as scattering of electrostatic LH waves through particles, also known as nonlinear Landau damping or nonlinear induced scattering. [10][11][12] In particular, whistler wave generation by the nonlinear induced scattering mechanism has been studied theoretically, [12][13][14][15] experimentally, 16 and through simulations. 12,15,17,18 Studying the nonlinear generation of whistlers in turbulent plasmas is one of the main objectives of the Space Measurement of a Rocket Release Turbulence (SMART) experiment, which is based on previous active experiments. ...

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2D kinetic simulations of whistler wave generation by nonlinear scattering of lower-hybrid waves in turbulent plasmas

... Cumulatively the gradient in the parallel and perpendicular flows, which arises naturally as a consequence of the global compression, constitute a rich source for waves in a broad frequency and wave vector band and their emission is necessary to relax the stress, i.e. gradients, that builds up in the layer during the dipolarization process. In particular, the generation of both electrostatic and electromagnetic waves around the lower hybrid frequency by velocity gradient has been extensively studied 15,46,[49][50][51][52][53] . Simulations 37,38 indicate that these waves produce anomalous viscosity and relax the gradients to reach a steady state. ...

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Kinetic Equilibrium of Dipolarization Fronts

... The abrupt onset of these dynamic activities has been attributed to plasma instabilities such as the ion-tearing instability (Schindler, 1974), the ballooning instability (Cheng & Lui, 1998;Henderson, 2012;Liu, 1997;Samson, 1998), Kelvin-Helmholze instability (Rostoker, 1996;Rostoker, 2007;Samson, 1998). Further awareness of the shortcomings of the single-fluid approach also leads to the consideration of kinetic instabilities such as the cross-field current instability (Lui et al., 1991) and shear-flow instability (Ganguli et al., 2014(Ganguli et al., , 2018. ...

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Processes in the Current Disruption Region: From Turbulence to Dispersion Relation

... While we found that the effect of Lorentz force due to dust charging was negligible for the 30 -70 µm size tungsten dust for the orbital lifetime of interest to us, it may be important for smaller, nm scale, dust. We are investigating the possibility of exploiting dusty plasma properties by using nm scale dust [14]. ...

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Active Removal of Orbital Debris by Induced Hypervelocity Impact of Injected Dust Grains