Large Mass Loading Research Articles

The effect of mass loading on the temperature of a flowing plasma

We have investigated how the addition of ions at rest (mass loading) affects the temperature of a flowing plasma in a magnetohydrodynamic (MHD) approximation, using analytic theory and time dependent, three‐dimensional MHD simulations of plasma flow past Io. The MHD equations show that the temperature can increase or decrease relative to the background, depending on the local sonic Mach number (MS) of the flow. For flows with MS > √9/5 ( when γ = 5/3), mass loading increases the plasma temperature. However, the simulations show a non‐linear response to the addition of mass. If the mass loading rate is large enough, the temperature increase may be smaller than expected, or the temperature may actually decrease, because a large mass loading rate slows the flow and decreases the thermal energy of the newly created plasma.

Lightning generation in planetary atmospheres

The possibilities of lightning generation on other planets are considered, and the basic conditions that exist in terrestrial clouds during lightning discharges and the various theories of charge separation are reviewed. Recent measurements of cloud structure and whistlers, as well as optical observation of lightning on Jupiter, suggest that charge separation and lightning discharges occur on other planets in ways similar to those in which they occur on Earth. Using these terrestrial ideas, it is concluded that lightning on Venus will probably be found in clouds that are located in regions of convection such as those observed downwind of the subsolar point. It is also possible that if volcanoes on Venus are erupting, they too can produce lightning discharges in their plumes although it seems unlikely that this process can account for the observed rate of discharge. Jovian lightning is most probably generated in the lower water-ice clouds. These clouds are of moderate temperatures and have strong convection and large mass loading, all important ingredients for electrical buildup. Lightning is all but ruled out for Mars, even though some electrification is possible owing to the large dust storms on that planet.

Rotated Y-cut quartz crystal with two different electrodes treated as a one-dimensional acoustic composite resonator

In this paper a quartz crystal coated with electrodes of different materials is considered as a one-dimensional composite acoustic resonator. The piezoelectric properties of quartz are incorporated in the model. The model leads to a transcendental equation from which the resonant frequencies can be calculated. It will be shown that earlier develolped models can be derived from this more general model by making the proper approximations. The difference between the theoretical resonant frequencies, as calculated from the various models, is discussed. To express this difference a systematic error is defined which proved to be negligable for small mass loading, corresponding to a relative frequency shift <1%, and in the case independent of the electrode material. In case there is a larger mass loading, the discrepancy between the previous models and the model presented in this paper can be of the order of 5%–10%, depending on the properties of the electrode material, i.e., the acoustic impedance and on the ratio of the thicknesses of the electrodes.