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Strong kinetic heating of grains is frequently associated with a melting transition in plasma crystals. At high pressures, above 100 mTorr, the melting transition is preceded by a vibrational phase whereas at low pressures, below 50 mTorr, observed large amplitude self-excited oscillations can lead to lattice disruption. At such low background gas pressures, only single layer crystals are formed. This work focuses on the low pressure regime and provides a theory of the self-excited oscillations which explains both the pressure and the power dependence of these oscillations as well as their threshold behavior. The implications for the melting transition are pointed out.

It is shown that the resonant streaming energy associated with cross-field motions (due to the cross product of dc electric and magnetic fields) of the plasma particles can be coupled to low-frequency electrostatic waves. Conditions under which unstable waves appear are obtained for both collisionless and collisional dusty magnetoplasmas. The relevance of the present investigation to understanding the origin of nonthermal fluctuations in laboratory and space plasmas is pointed out.

A large number of laboratory observations reveal the formation of ordered linear chains and sheets composed of charged dust grains levitated in the sheath region of radio-frequency or dc plasma discharges at very low pressures. At higher pressures, three-dimensional structures are typically formed. Recently, a number of low gas pressure experiments have explored the generation of large amplitude vertical oscillations by lowering either the background pressure or the plasma power below a threshold value, or by imposing an external force that arises from a low-frequency sinusoidal voltage in the sheath region. A theoretical model is presented that successfully describes the phenomenology in various experiments, including the observed self-excited oscillations, nonlinear resonance and parametric oscillations. A new forcing mechanism, namely the modulational forcing, for exciting nonlinear resonances is proposed.

Large Amplitude Oscillations Sustained by Stochastic Plasma Density Fluctuations in Plasma Sheaths

In a recent paper, Takamura et al. [Phys. Plasmas 8, 1886 (2001)] described a variety of dynamic behaviors of dust grains in a dusty plasma device under conditions of a weak friction with gas molecules, that is, at low neutral background gas pressures. When the gas pressure is decreased below a critical value, an instability leading to large amplitude dust oscillations is observed in a single horizontal layer of dust grains trapped near the plasma–sheath boundary above a negatively biased mesh electrode. The instability mechanism has been identified as delayed charging of a dust grain in a plasma sheath. Our objective here is to indicate that the delayed charging mechanism cannot account for stochastic dust oscillations, and to point out a new mechanism that can explain the observed features of large amplitude self-excited dust oscillations.

Summary form only given. Powerful electric currents and transient luminous events (sprites, blue jets and gigantic jets) have been detected in discharges between thunderclouds and the lower ionosphere. The occurrence of such phenomena is strongly related to the occurrence of ultra low frequency (ULF~3-50 Hz) waves and to the occurrence of positive polarity cloud-to-ground flashes. We present a novel mechanism that shed light on the origin and propagation of the observed ULF waves. Ionospheric clouds are composed of charged ice/smoke particulates, protons, electrons and neutrals. Our objective here is to show that such partially ionized dusty plasmas with streaming electrons in ionospheric clouds may support unstable dust acoustic waves (DAWs~3-12 Hz). For our purposes, we employ a multifluid dusty plasma model and derive the dispersion relation for modified DAWs in a magnetized, collisional plasma. The dispersion relation is analyzed numerically to obtain the growth rate and threshold

The kinetic theory of collisionless electrostatic shocks resulting from the collision of plasma slabs with different temperatures and densities is presented. The theoretical results are confirmed by self-consistent particle-in-cell simulations, revealing the formation and stable propagation of electrostatic shocks with very high Mach numbers ($M \gg 10$), well above the predictions of the classical theories for electrostatic shocks., Comment: 6 pages, submitted to Phys. Rev. Lett

[1] Powerful electric currents and transient luminous events (sprites, blue jets and gigantic jets) have been detected in discharges between thunderclouds and the lower Ionosphere. The occurrence of such phenomena is strongly related to the occurrence of Ultra Low Frequency (ULF ∼ 6–50 Hz) waves and to the occurrence of positive polarity cloud-to-ground flashes. In the present letter, we present a novel mechanism to explain the origin and propagation of the observed ULF waves. Ionospheric clouds are composed of charged ice/smoke particulates, protons, electrons and neutrals. Our objective here is to show that such partially ionized dusty plasmas with streaming electrons in ionospheric clouds may support unstable ULF dust acoustic waves (DAWs). For our purposes, we employ a multifluid dusty plasma model and derive the dispersion relation for modified DAWs in a magnetized collisional plasma. The dispersion relation is analyzed numerically to obtain the growth rate and threshold.

0654 Electromagnetics: Plasmas; 2471 Ionosphere:Plasma waves and instabilities; 2487 Ionosphere: Wavepropagation(6934);3304MeteorologyandAtmosphericDynamics:Atmospheric electricity; 3324 Meteorology and AtmosphericDynamics: Lightning; 9900 Corrections. Citation: Sorasio, G.,P. K. Shukla, D. P. Resendes, and J. T. Mendonc¸a (2004),Correction to ‘‘Origin of ELF/ULF waves triggered by positivecloud to ground lightning above mesoscale connective systems,’’Geophys. Res. Lett., 31, L14112, doi:10.1029/2004GL020874.

[1] It is shown that charged dust grains can be accelerated by the nonuniform space charge electric fields that are created by the ponderomotive force of circularly polarized electromagnetic cyclotron waves. The relevance of our investigation to dust energization in the Earth's mesospheric plasma is stressed.

A kinetic theory for the equilibrium of an unmagnetized plasma consisting of electrons and ions surrounding a spherical body emitting electrons (due to thermionic emission, photoemission, or secondary emission) is presented. The theory is valid for positively charged bodies, neglects collisions of the plasma particles, and is formulated for profiles of the shielding potential presenting an attractive well. Particle-in-cell simulations are shown to be in good agreement with the theory. An approximated criterion is derived to determine the presence of the potential well.

Recently the dynamics of dust grains trapped in the sheath region of radio-frequency (rf) or dc plasma discharges under low pressure conditions has attracted the attention of the dusty plasma community. Several experiments have been performed in order to explore the dynamics of dust grains levitating above the negatively biased electrode. Under very low pressures, several experimental groups have observed the generation of self excited large amplitude vertical oscillations which arise by lowering either the background pressure or the plasma number density. In other experiments, the vertical oscillations have been driven by an external sinusoidal voltage applied to a wire in the sheath region. A theoretical model is presented that successfully describes the phenomenology in these various experiments including the observed self excited oscillations and nonlinear resonance oscillations.