A. Geranios

Having high-resolution UV spectra produced from EAS fluorescence, one can determine in a more accurate way the effects of atmospheric attenuation of these signals by including Rayleigh, Mie-scattering as well as resonance absorption inside the atmosphere. For this reason, we developed an experimental setup for emulating the air-fluorescence using high-resolution spectroscopy in the UV range from 300 to 400 nm. We used low pressure electrical discharges in air , as light source, and registered the spectra with high resolution spectrometers of 0.25, 1, 2 and 3 m focal lengths. These pressure and temperature conditions, existing in the low pressure lamp used, are far from the ones existing during EAS fluorescence but such data might be useful for better understanding of the fluorescence emission, and also in allowing to adapt such spectrometers in dedicated fluorescence yield experiments in accelerators, since in the relevant literature there are not available data with such high resol...

The Linsley standard atmospheric model is used to simulate the atmospheric EAS due to the passage of an Ultra High Energy Cosmic Ray (UHECR, Linsley, 1977). Adopting the AIR shower Extended Simulation (AIRES) program we derived the longitudinal and lateral distribution of the secondary particles produced in the atmosphere along the path of the primary. From these distributions one can distinguish between protons and ions as an UHECR. Energy Spectrum of C.R. One of the primary purposes of the Pierre Auger Project and Observatory is to study the masses of ionizing radiation, cosmic rays, which are constantly striking the earth. Due to the high occurrence of low-energy cosmic rays, they have become relatively well understood in the 80 years since the discovery of cosmic rays. However, cosmic rays at higher energies are much rarer. Also, primary cosmic rays can never be directly observed, and must be studied through the properties of the air showers which they cause in the upper atmosph...

A preliminary indoor radon survey in Greece based on about 250 passive detectors, to test the technique and the statistics, is presented. The majority of the detectors were placed in schoolrooms and dwellings for a year. The measurements conceming the northem part of Greece indicate a higher radon concentration than the rest of the country. The radon concentrations are well fitted to the theoretically expected log-normal distribution. In the attached map three concentration categories are marked: (0-99 Bq.m -3 , 100-200 Bq.m -3 and >200 Bq.m -3 ). Due to the small sample of detectors, one should not interpret this map as characterising whole geographic areas, but simply indicating the radon concentrations at the particular sites. In order to complete a national radon survey, a much more dense sample is needed.

The detection efficiency of a pixel detector of an EAS telescope using optical UV filters is determined in this work. Based on the Auger Fluorescence Detector geometry, we have calculated the overall efficiency of the pixel detector using an appropriate method which takes into account the particular spectral functions and the dependence on the angle of incidence of the optical

Multilayer notch optical filters, designed to reject the optical noise emitted in the range between the main UV spectral lines of the atmospheric N2 fluorescence, induced by UHECR via the effect of EAS, are combined in order to have a complementary selectivity in detecting Cherenkov radiation as well. Thus, the detection of the two components is possible at the same

SummaryThe dynamical characteristics of α-particles in the solar wind between 0.3 and 1.0 AU are studied. It has been found that the connections between alpha temperature and speed, normalized at 1AU, as well as radial temperature exponents significantly differ from those found for protons. Between α and proton temperature, generally, the α temperature depends stronger on flow speed. Nevertheless, the flow characteristics of alphas and protons concerning their speeds are similar. For example, the dependence ofTα onVα is stronger also for slow than for fast alpha flows. The alpha radial temperature decreases much slower than proton temperature away from the Sun, according to the relationTα/T0=(r/r0)−k withk varying from very low (0.10) to moderate values (0.60).Tα,T0 are the alpha temperatures at distancesr,r0(=1 AU), respectively. These findings strongly suggest an additional heating of alphas, for example by Alfven waves or Coulomb collisions.RiassuntoSi studiano le caratteristiche delle particelle α nel vento solare tra 0.3 e 1.0 AU. Si è trovato che la connessione tra temperatura e velocità normalizzate a 1AU delle particelle α e esponenti di temperatura radiale differiscono in modo significativo da quelle trovate per i protoni. Tra le temperature delle particelle α e dei protoni la temperatura delle prime generalmente dipende più fortemente dalla velocità del flusso. Nonostante ciò le caratteristiche del flusso delle particelle α e dei protoni riguardo le loro velocità sono simili. Per esempio anche la dipendenza diTα daVα è più forte per flussi di particelle alfa lenti che per quelli veloci. La temperatura radiale di alfa diminuisce molto più lentamente che la temperatura dei protoni lontano dal Sole secondo la relazione,Tα/T0=(r/r0)−k, conk che varia da valori molto bassi (0.10) a valori moderati (0.60).Tα,T0 sono rispettivamente le temperature di α a distanzer,r0(=1AU). Ciò suggerisce fortemente un riscaldamento addizionale delle particelle α, per esempio, da parte di onde Alfven o collisioni di Coulomb.РезюмеИсследуются динамические характеристики альфа-частиц в солнечном ветре в области между 0.3 и 1.0 а.е.д. Обнаружено, что связь между альфатемпературой и скоростью, нормированная при 1 а.е.д., а также показатели альфатемпературы существенно отличаются от результатов, полученных для протонов. Альфа-температура сильнее зависит от скорости потока. Однако характерестики потока для алфа-частиц и для протонов, касающиеся их скоростей, оказываются одинаковыми. Например, зависимостьTα огvα оказывается сильнее для медленных, чем для быстрых потоков альфа-частиц. Радиальная альфа-температура уменьшается медленнее, чем протонная температура, при удалении от Солнца, согласно соотношениюTα/T0=(r/r0)−k, гдеk изменяется от очень малой (0.10) до средней величины (0.60),Tα иT0 представляют альфа-температуры на расстоянияхr иr0 (=1 а.е.д.), соответственно. Полученные результаты указывают на дополнительное нагревание альфа-частиц за счет волн Альфвена или кулоновских соударений.

... References Fokitis, E., Drakaki, E., Maltezos, S., Moyssides, P., Papantonopoulos, L., Patrinos, K., Vlastou, R., Geranios, A., Vassiliou, M., Petridis, A. Pro-ceedings of 27th ICRC, Hamburg, p. 667, 2001. Greisen, K., Annual Review of Nuclear Science, 10, 63, 1960. ...

ABSTRACT During November 17-18, 1975, a magnetic cloud was observed by the IMP 8 satellite. The cloud was analyzed in several papers. It draws attention because it is the most clear example where the magnetic field components behave differently from the current single flux rope model. Various models and fits have been presented to explain the magnetic field measurements for this particular event: single-polarity cylindrical flux rope, spheromak, toroidal flux rope, and two subsequent flux ropes (flux rope twins). We critically examine these models and fits and stress that not only magnetic field data but also plasma data must be taken into account. There is a remarkably sharp drop in the density inside the magnetic cloud. The most consistent explanation of the behavior of magnetic field and plasma data for this event is that the magnetic cloud consists of a dual-polarity flux rope with a low density and strong magnetic field core surrounded by an annular region of the same chirality but opposite polarity. An implication of this possibility to explain other magnetic cloud observations is discussed.

Energy is among the characteristics of Ultra High Energy Cosmic Rays (E > 5 ×1019 eV ) which could be estimated experimentally based on simulations. This paper attempts to estimate the energy of an UHECR proton by applying a Monte Carlo simulation code. A number of extensive air showers, vertical and inclined, are simulated to derive the lateral distribution functions of the shower particles. The scenario of simulations is adapted to the P. Auger Observatory site.

Hourly interplanetary plasma data measured by Helios-1 satellite over the period 10 December 1974–31 December 1977 are analysed. This analysis showed that the slow solar wind first increases its speed with heliocentric distance and then becomes more or less constant; the mean speed in the range 0.3 to 1.0 AU is 350 km s−1 for the slow solar plasma, while for the fast the mean value is between 650 and 700 km s−1.It seems, particularly in the neighbourhood of the earth, that except for the two dominated types of solar wind (fast and slow) an additional (intermediate) appears at 450 km s−1.During the phase of enhanced solar activity (11-yr solar cycle) the slow solar wind only is present, while at solar minimum all three types of the solar wind are equally represented.The dependence of the proton temperature on the solar wind speed, in the general solar wind, is the same irrespectively of the phase of solar activity. But, the same dependence is stronger during the ‘compression’ at the leading edge than during the ‘expansion’ at the trailing edge of a solar wind stream.

We present unique observations obtained by the Magnetospheric Imaging Instrument (MIMI) on the Cassini spacecraft, of the energetic ion population in the environment upstream from the dawn-to-noon sector of the Kronian magnetosphere during the approach phase and subsequent several orbits of the Cassini spacecraft around the planet. High sensitivity observations of energetic ion directional intensities, energy spectra, and ion composition were obtained by the Ion and Neutral Camera (INCA) of the MIMI instrument complement with a geometry factor of ~2.5cm2sr. Charge state information was provided by the Charge-Energy-Mass-Spectrometer (CHEMS) over the range ~3 to 220 keV per charge. The observations revealed the presence of distinct upstream bursts of energetic hydrogen and oxygen ions up to distances of ~135RS. The observations are presented and their theoretical implications are addressed.

The aim of the Pythagoras project is the development and assessment of Greek national training material in the sector of indoor environmental quality. The need for education in this specific sector is dictated by the significant indoor environment deterioration and associated health hazards, which are caused by low ventilation levels, combined with the use of many modern building materials that aggravate pollutants emissions. Early in the project, a review is undertaken of the international literature and the syllabuses of foreign research and ...

In order to estimate the N-S anisotropy latitude gradient, the time variation of the direction of the N-S anisotropy during the August 1972 cosmic ray storms is measured using polar (Alert-Mc Murdo) and equatorial (Athens-Potchefstroom, S. Africa) neutron monitor stations. A maximum value of (43 ± 2)%/50° and a linear correlation between the measured polar and equatorial N-S anisotropies is

The extremely high cost of motor-vehicle accidents in public health leads to the necessity of a better injury data collection in the Accident and Emergency Hospital Departments. The ‘Asclepeion’ of Voula Hospital covers the southeastern suburban areas of the greater Athens area (1 000 000 population). The aim of this study is to present information on the pattern of injuries

Among the most interesting tasks for the identification of Ultra High Energy Cosmic Rays (origin, mechanisms of acceleration, top down model, direction, and maximum energy) is their isotopic composition. For example, if they are protons, heavier nuclei, gammas or even exotic. Air Shower Extended Simulation code (AIRES) is used to simulate the Extended Atmospheric Showers. This code gives, among others, the maximum number of secondary particles within the atmosphere along the longitudinal direction of the showers. From the distribution of the depths of maximum number of shower particles and their content in muons, we can distinguish between proton and gamma primary cosmic rays, both of energy of 100 EeV. The results show a maximum at lower atmospheric depths for protons and at higher for gammas, respectively. Due to the bremsstrahlung and pair production effects, the muon content of gamma showers is much poorer than of protons. Both facts enable the distinction between proton and gamma cosmic rays. For the simulation of the atmospheric EAS due to the passage of an Ultra High Energy Cosmic Ray, the Linsley standard atmospheric model is used.

ABSTRACT Three dimensional magnetohydrodynamic numerical simulations of propagating interplanetary flux ropes are presented and compared with ``in-situ'' spacecraft measurements. Flux ropes are injected near the Sun with various inclinations. Specific features followed from simulations, as double-peak magnetic field profiles or a possibility to observe one flux rope two times by the same spacecraft, are searched in observational data.

Solar energetic particles are utilized as diagnostic tracers of the large-scale structure and topology of the Interplanetary Magnetic Field embedded within two Interplanetary Coronal Mass Ejections detected in late October and early November 2003 at 1 AU by the ACE spacecraft. Two candidate scenarios to account for the observations in terms of open and closed magnetic field configurations are examined. We also use ACE/EPAM observations to reassess the boundaries of the ICMEs with respect to those previously proposed.

ABSTRACT The magnetic cloud of January 10–11, 1997, was observed by SOHO and WIND spacecraft ahead of the Earth's magnetosphere. Plasma parameters registered by their instrumentation show remarkable differences in the solar wind speed, proton density and tempersture that is difficult to explain taking into account simply their distance. The interplanetary magnetic field (measured on board WIND only), would be fitted nearly equivalently by both cylindrical and spherical models. In order to explain observed divergences we speculate on possible model of a poloidal spheromak that develops into a toroid during its propagation.

ABSTRACT Several advances expected in energetic particle research in the context of possible observations with the Solar Orbiter (SOLO) and the Inner Heliospheric Sentinels (IHS) are presented. Since propagation effects are expected to have a much smaller influence on particle profiles closer to the Sun compared to an observer at the Earth, energetic particle observations obtained with Solar Orbiter (that will spend roughly half of its time inside 0.5 AU) and IHS will provide a more accurate estimation of the onset times of solar energetic particle events and make multiple particle injections detectable. Furthermore, fine-time resolution energetic particle measurements obtained by SOLO along with the more detailed information on solar activity (CMEs, electromagnetic radiation) available from SOLO, from other spacecraft, and from ground-based instruments, compared e.g. to Helios, will make possible valuable investigations in much better observed events of the relative timing of injection between energetic electrons and ions in close linkage with the plasma and radiation conditions in their source regions on the Sun. We will also demonstrate how the intensities and angular distributions of near-relativistic electrons which are ideal field line tracers - can be used as a diagnostic tool to monitor, through SOLO and IHS measurements, the connectivity of Interplanetary Magnetic field lines threading through Interplanetary Coronal Mass Ejections (ICMEs) in the inner heliosphere.

ABSTRACT The determination of energy of Ultra High Energy Cosmic Rays (E >= 5×1019 eV) is one of the important issues concerning these particles. For this purpose, Monte Carlo simulations are used to create a large number of vertical and inclined extensive air showers in order to estimate the primary energy based on the lateral distribution function of recorded electrons and muons. This methodology could be applied to all cosmic ray experiments using a surface array of Cerenkov detectors, like, for example, the P. Auger Observatory.

ABSTRACT For more precise energy determination of UHECR, the fluctuations of the lateral distribution function play a significant role. We present a series of AIRES EAS simulations for gamma primaries of 100 EeV energy and different primary zenith angles. Due to the fact that electrons and positrons carry the 90% of the UHECR energy, we use these components to derive the lateral distribution functions and determine the distance which does not depend on the zenith angle of the primary gamma ray. The atmosphere with which cosmic particles interact plays the role of a huge detector within which a large number of elementary particles is created and which develops the structure of an EAS. These particles, which 90% consist of electrons, positrons and photons, form a disc of particles which is propagated with nearly the speed of light forming the base of the EAS front. Upon arrival at the earth surface its radius increases with energy, up to several kilometres. The longitudinal and lateral structure of the showers can give us valuable information of the energy, origin and chemical composition of the cosmic particle. The dynamics of the behaviour of the lateral distribution of particles in EAS is well understood and is used to determine primarily the energy of the cosmic particle.

An experimental setup and procedure for accurate transmittance measurements of candidate filters for the Auger Fluorescence Detector is presented. For this check, we used the Hitachi U-2000 double-beam spectrophotometer (Sph) of the Chemical Department of the University of Athens (UoA). After the calibration of the Sph, we are able to observe transmittance deviations over the area of the filter under study within a sensitivity better than 0.2%. A set of candidate filters is measured to identify their spectral transmittance in response to different angles of incidence. Also, the use of the Sph for few layers developmental multilayer can be studied for their spectral transmittance. In addition, the performance of the optical filter as well as the phototube has an angular dependence. Taking all these effects into account, we come to the conclusion that it may be very difficult, in fact it is a challenge to achieve an error control in the measurement of EAS signal in each photomultiplie...

The Linsley standard atmospheric model is used to simulate the atmospheric EAS due to the passage of an UHECR. Adopting the AIRES shower simulation program we derived the longitudinal distribution of electrons and positrons produced. These particles exciting the nitrogen molecules in the atmosphere play a dominant role in the amount of fluorescence light coming from nitrogen deexcitation within the wavelength range of 300 - 400 nm. The fluorescence triggers efficiently the array of photomultiplier tubes (PMT) of the Fluorescence Detector of the Auger Observatory, provided that the signal to noise ratio at each pixel taking part in the trigger decision for counting the photoelectrons is typically greater than 5. Results of simulation for typical events expected to be registered by the AUGER FD prototypes are presented. The relative counting rate of the PMT array is obtained for a typical shower triggered by a cosmic ray proton for different inclinations. Future perspectives for simul...

Various investigators are involved with radon research in Greece. Numerous measurements have been reported for different regions around the country. In this study we focus on the city of Loutra Edipsou, a spa centre of about 4000 inhabitants in the northern part of the island of Evia (Greece). This city is built on an area of high geothermal activity, a fact that served as a guide to our study. The aim was to estimate the dose delivered to inhabitants, the potential alpha energy exposure of bathers and spa personnel and to investigate the radon background in this area. The detectors used were of active type. Measurements are reported for dwellings, which were grouped into two different sets: one representing typical summer periods (July and August 2002) and the other typical winter periods (October and November 2002) The Potential Alpha Energy Exposure (PAEE) of the bathers during treatment lies in the range between (45 +/- 3) and (110 +/- 5) mWLM (1 WLM = 12.97 J s m(-3)). The PAEE of the working personnel lies in the range between (34 +/- 3) and (100 +/- 20) mWLM.