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The Singular Spectrum Analysis technique has been applied to the amplitude of the first Schumann resonance measured at the Sierra Nevada station (Spain) in order to obtain the principal components of its time evolution. The results of this study confirm the appearance of the annual and semiannual components that have been pointed out for this resonance and also reveal other components corresponding to 45 to 120 days variations, which matches the variations of athmospheric waves like the Madden-Julian oscillation and the Kelvin waves. A preprocessing of the measurements is required since the station has experienced some technical failures and there are thus some gaps in the measured data. The application of the technique has been made taking one data per month and one data per day, and the results have been compared.

This work proposes and illustrates a graphical approach aimed at studying a wide range of features of the ELF horizontal magnetic field signal recorded at the Sierra Nevada station (Spain). In addition to the traditional long-term variations in the parameters of the first three Schumann resonances (their amplitudes, central frequencies and widths), many other properties such as the saturations of the magnetometers, anomalous values for the parameters or spectra with any kind of particularities are taken into consideration in this work. These features can provide us with complementary information about the long-term variation of Schumann resonances, give an estimation of the extent up to which the results obtained are reliable and be correlated with the occurrence of lightning events or with changes in the electrical properties of the ionosphere. The scheme proposed in this work allows to instantaneously display the variations of all these features within a desired period of time.

The paper studies a parallel resonant converter with a capacitor as output filter to generate and maintain a glow discharge in air. The application requires a high output voltage for air breakdown and much lower values to maintain discharge operation. Attention is payed to converter steady state and dynamic aspects.

This contribution is aimed at separating the anthropogenic noise from the natural magnetic field in the measurements recorded in a Extremely Low Frequency band station located in Sierra Nevada, Spain, to experimentally study Schu-mann resonances. First, we use a scheme based on Independent Component Analysis that provides unsatisfactory results. In order to achieve a better separation, we develop a new method by exploiting the information that statistical moments give us, under the assumption that the statistical distributions of the anthropogenic noise and of the natural magnetic field are different. This method consists of finding the rotation of the two original directions of the magnetometers (North-South and East-West) that maximizes or, equivalently, minimizes, the value of a certain statistical parameter. Our purpose is that this rotation is equal to that rotation which makes the anthropogenic noise completely disappear from one of the outputs, which we will show that always exists.

Intentional jamming and spoofing are growing concerns for communication and positioning systems based on Global Navigation Satellite System (GNSS). In the maritime sector, intentional interfering signals might induce poor performance of the GNSS receivers, that, in severe cases, are unable to provide reliable measurements. On board of vessels, the failure of the GNSS receiver propagates to multiple systems, like the Automatic Information System (AIS) transponder, the ship's gyro calibration system and the digital selective calling system. The AIS itself can suffer from failures due to interference in the VHF band, and the lack of bandwidth makes it difficult to introduce security any security mechanisms. The vulnerability to intentional interference as well as the availability of personal privacy devices easily sold over the Internet motivate attackers who intend to fraud services and get direct benefits.