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Surfactant-containing water droplets were produced using a 75-Vrms pondermotive force operating at 10 kHz. Heat from a 30-V direct-current source, applied to a 2 × 0.1-mm region of the fluid, was instrumental in rupturing a low-surface-energy liquid membrane and forming the droplet. The low voltage allows quick and accurate dispensing of droplets without dielectric breakdown. Nanoliter-sized (~7.6-nL) butanol-styrene droplets were formed using 133 Vrms at 900 Hz. Microliter-sized oil droplets (~0.6 to 10.5 μL) were formed using high voltage (460 to 672 Vrms at 100 Hz). Oil-water emulsions were formed and moved horizontally, overcoming frictional and surface tension forces. Large oil droplets were also moved to a wider electrode spacing, where the emulsion can take the spherical shape of a target. This was only achieved by transporting the emulsion down an inclined slope (45 deg) using gravity to augment the electric force. All the steps are in place to form targets from oil-water-oil and water-oil...

The electric-field–assembly technique proposed for making fusion targets uses the electrical force from dielectrophoresis and electrowetting-on-dielectric phenomena to form droplets of oil and wate...

Experimental results are presented from ionospheric tomography, the EISCAT Svalbard radar and the CUTLASS HF radar. Tomographic measurements on 10 October 1996, showing a narrow, field-aligned enhancement in electron density in the post-noon sector of the dayside auroral zone, are related to a temporal increase in the plasma concentration observed by the incoherent scatter radar in the region where the HF radar indicated a low velocity sunwards convection. The results demonstrate the complementary nature of these three instruments for polar-cap ionospheric studies.Key words. Ionosphere · Auroral ionosphere · Polar ionosphere · Radio science (ionospheric physics)

Ultra low frequency (ULF) wave activity in the high-latitude ionosphere has been observed by a high frequency (HF) Doppler sounder located at Tromsø, Norway (69.7°N, 19.2°E geographic coordinates). A statistical study of the occurrence of these waves has been undertaken from data collected between 1979 and 1984. The diurnal, seasonal, solar cycle and geomagnetic activity variations in occurrence have been investigated. The findings demonstrate that the ability of the sounder to detect ULF wave signatures maximises at the equinoxes and that there is a peak in occurrence in the morning sector. The occurrence rate is fairly insensitive to changes associated with the solar cycle but increases with the level of geomagnetic activity. As a result, it has been possible to characterise the way in which prevailing ionospheric and magnetospheric conditions affect such observations of ULF waves.Key words. Ionosphere (auroral ionosphere; ionosphere -magnetosphere interactions) · Magnetospheric physics (MHD waves and instabilities)