This Letter presents a first step towards a substorm model including particle heating and transport in the plasma sheet boundary layer (PSBL). The heating mechanism discussed is resonant absorption of Alfven waves. For some assumed MHD perturbation incident from the tail lobes onto the plasma sheet, the local heating rate in the PSBL has the form of a resonance function of the one‐fluid plasma temperature. Balancing the local heating by convective transport of the heated plasma toward the central plasma sheet, an "equation of state" is found for the steady‐state PSBL whose solution has the form of a mathematical catastrophe: at a critical value of a parameter containing the incident power flux, the local density, and the convection velocity, the equilibrium temperature jumps discontinuously. Associating this temperature increase with the abrupt onset of the substorm expansion phase, the catastrophe model indicates at least three ways in which the onset may be triggered. Several other consequences related to substorm dynamics are suggested by the simple catastrophe model

Miniature diode-pumped acousto-optically Q-switched solid-state lasers deliver pulse durations as short as 600 ps at wavelengths near 1 µm. Specifically, Nd:YVO(4) lasers operating at 1.064 µm produce 600-ps/5-kW pulses at 1 kHz, 1.0-ns/2-kW pulses at 20 kHz, and 1.9-ns/0.5-kW pulses at 100 kHz. A Nd:YLF laser at 1.047 µm generates 700-ps/15-kW pulses at 1 kHz, and 1.2-ns/4-kW pulses at 10 kHz. At 1.342 µm, a Nd:YVO(4) laser produces 3.3-ns/0.8-0.6-kW pulses at 1-10 kHz.

It has been experimentally observed for some time that certain tearing modes in plasmas may be suppressed if the plasma rotates in a preferred direction. In this paper we treat the m = 0, finite-wavelength tearing mode in cylindrical geometry for a reversed-field plasma equilibrium and show that by generalizing Ohm's law to include Hall current terms, we are able to explain this effect of rotation on tearing modes. Our results agree qualitatively with earlier analysis and numerical simulations. We also show that our results are sensitive to the position of the outer conducting wall, and for wall positions sufficiently close to the plasma-vacuum interface, tearing modes may be quenched when the rotation reaches a critical value. These results follow from a boundary-layer analysis and numerical integration of the boundary-layer equations.