Ignition by Electrical Discharges

The ignition of combustible/air mixtures by electrical discharges includes several physical and chemical processes. In process safety often the total available electrical energy is taken as a risk measure. However, to get a more detailed insight in the ignition process, also energy losses to the surrounding have to be considered. Additionally, for specific discharges not only the dissipation leading to thermal heating is of importance. Especially in the case of non-equilibrium plasma, a specific fractional amount of the discharge energy is used for electron impact dissociation, excitation, and ionization reactions, producing active radicals and ions during the discharge phase. While the electrical energy can be measured easily, it is difficult to determine energy losses. In this paper three different electrical discharges are examined experimentally and numerically to yield a better understanding of the ignition by electrical discharges.

Review on the solar spectral variability in the EUV for space weather purposes

The solar XUV-EUV flux is the main energy source in the terrestrial diurnal thermosphere: it produces ionization, dissociation, excitation and heating. Accurate knowledge of this flux is of prime importance for space weather. We first list the space weather applications that require nowcasting and forecasting of the solar XUV-EUV flux. We then review present models and discuss how they account for the variability of the solar spectrum. We show why the measurement of the full spectrum is difficult, and why it is illusory to retrieve it from its atmospheric effects. We then address the problem of determining a set of observations that are adapted for space weather purposes, in the frame of ionospheric studies. Finally, we review the existing and future space experiments that are devoted to the observation of the solar XUV-EUV spectrum.

Spectroscopic Investigations of Some Halide Reactions in Plasma-Generating Devices

The behaviors of some halides of carbon (CF4, CCl4, CF3Cl, and Teflon), silicon (SiF4 and SiCl4), and boron (BF3) in plasma reactors have been investigated by emission spectroscopy. The emission spectra from these compounds have been identified and arise from excited diatomic molecules SiF, SiO, BO, C2, and CN and excited atoms of Si, B, and C. On the basis of the observed spectra and energetic and thermodynamic arguments, it is concluded that dissociation, excitation, and/or ionization processes requiring 25–30 eV are predominant in the plasma reactors under the experimental conditions of these studies.