Some theories for the observed anomalous radar backscatter during the summer (polar mesospheric summer echoes, or PMSE) and electron bite outs measured by rockets require the presence of charged dust. To investigate this, two dust probes have been launched in 1994 from Andøya Rocket Range and we here report the results from the dust and an electron probe on the two payloads. The dust probes were designed to block out the electron and ion components at the mesopause but to detect primary currents due to impacts of charged dust and also to detect secondary plasma production during dust impacts. The results indicate that both during PMSE and noctilucent cloud (NLC) conditions, large amounts of dust, with average sizes apparently of about 0.1 μm and less, were present. The number densities Nd can be up to many thousand per cubic centimeter, and the charge density NdZd likewise. Large local gradients in density and charge density of dust are detected. Dust carrying both positive and negative charges can apparently be present on different occasions. In some parts of the NLC/PMSE layers we find that the negative charge density locked in grains is so large that the number of free electrons is significantly reduced there because the dust acts like sinks for electrons, and an electron bite out results. We also find that in one case the presence of positive dust leads to an increase in the local electron density by photoionization. The main uncertainties in the data analysis are the structure of the dust and the secondary plasma production at the comparatively low dust impact velocities (1 km s−1) in the experiment.

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This paper describes the simulation, design and fabrication of acceleration switches for automotive applications. A simulation model is introduced which describes the dynamical behaviour of the sensor. The main focus of the development is on the specifications of the accelerometer, such as the switching time, the overload protection, the self-test feature and the damping behaviour. The simulated acceleration switches are fabricated with the use of a sacrificial layer technique and electroplated moulding of microforms. The 3D-UV Microform technology was preferred because it enables high aspect ratio patterning of commercially available thick photoresists. First devices of the microswitch sensors were characterized by means of optical measurement facilities for the determination of resonance frequencies and of the dynamical behaviour during test pulses. Measurements on a shaker were carried out to confirm the validity of the model.

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