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Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece
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- PublicationOpen AccessWithin-the-hour variability: levels and their probabilities(2006-08)
; ; ; ; ; ;Kouris, S. S.; Division of Telecommunications, Department of Electrical Engineering, Faculty of Engineering, Aristotle University of Thessaloniki, Greece ;Polimeris, K. V.; Division of Telecommunications, Department of Electrical Engineering, Faculty of Engineering, Aristotle University of Thessaloniki, Greece ;Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Zolesi, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cander, L. R.; Radio Communication Research Unit, Rutherford Appleton Laboratory, Chilton, Oxon, U.K.; ; ; ; The study of foF2 data measured every 5-min and of TEC measurements made every 10-min shows that the within-the-hour variability is different in the two parameters. Deciles of this variability for foF2 and for TEC are determined together with the probabilities of exceeding a given level of variability. Furthermore, considering hourly values, it is found that the variability in TEC is like an «intrinsic noise» throughout the day of the order of less than 5% of the hourly value; but at sunrise and often at sunset large values take place. A seasonal dependence is evident. Besides, a within-the-hour variability in foF2 is always present with large values at sunrise or sunset depending on the season, and also during disturbed ionospheric conditions.172 163 - PublicationOpen AccessTen years analysis of Tropospheric refractivity variations(2004)
; ; ;Isaakidis, S. A.; Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece ;Xenos, T. D.; Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece; The refractivity variations of the troposphere are responsible for various effects on radio wave propagation, such as refraction, bending, radio-station interference, etc. In this work, the refractivity variations of the Hellenic troposphere are studied using data from Helliniko airport of Athens/Greece. The data were analyzed using various interpolation procedures, i.e. in a day-by-day manner for temperature and relative humidity, to transform the data according to a reference height common for the whole dataset and finally for the refractivity N with respect to time, using piece-wise hermite interpolation polynomials for the low and medium altitudes and linear interpolation factors for the high altitudes. Since refractivity varies with time and height, two height independent basic parameters were computed and analyzed: the refractivity at station height N0 and scale height Hs. These parameters can be used to calculate the refractivity profile. Using statistical tools as the moving average, the ß0 parameter and the monthly mean values, together with the corresponding standard deviations, useful results were obtained for the variations of the refractivity with respect to observation hour, height, season, month, day and level.137 392 - PublicationOpen AccessTEC and foF2 variations: preliminary results(2004)
; ; ; ; ;Kouris, S. S.; Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece ;Xenos, T. D.; Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece ;Polimeris, K. V.; Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece ;Stergiou, D.; Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece; ; ; Investigation of the relationship between TEC and (foF2)2 shows that although they are highly correlated, a «hysteresis» effect exists between them. The slab thickness is greater before than after mid-day for equal cos ?values. Moreover, a comparison of the calculated upper and lower quartiles of variability in TEC, foF2 and Nmax, respectively shows that the variability of TEC lies between those of foF2 and Nmax depending on the level of solar activity.328 575