Ayman Mahrous

Energy determination in the Akeno Giant Air Shower Array experiment

Abstract Using data from more than 10 years of observations with the Akeno Giant Air Shower Array (AGASA), we published a result that the energy spectrum of ultra-high energy cosmic rays extends beyond the cutoff energy predicted by Greisen [Rhys. Rev. Lett. 16 (1966) 748] and Zatsepin and Kuzmin [Zh. Eksp. Teor. Fiz. 4 (1966) 114]. In this paper, we reevaluate the energy determination method used for AGASA events with respect to the lateral distribution of shower particles, their attenuation with zenith angle, shower front structure, delayed particles observed far from the core and other factors. The currently assigned energies of AGASA events have an accuracy of ±25% in event-reconstruction resolution and ±18% in systematic errors around 10 20 eV. This systematic uncertainty is independent of primary energy above 10 19 eV. Based on the energy spectrum from 10 14.5 eV to a few times 10 20 eV determined at Akeno, there are surely events above 10 20 eV and the energy spectrum extends up to a few times 10 20 eV without a GZK cutoff.

Multiple ionospheric perturbations during the Saint Patrick's Day storm 2015 in the European-African sector

Strong ionospheric perturbations were generated by the intense geomagnetic storm on 17 March 2015. In this article, we are studying perturbations in the European-African sector observed in the total electron content (TEC). Focal points are wavelike phenomena considered as large-scale traveling ionospheric disturbances (LSTIDs). In the European-African sector, the storm produced three different types of LSTIDs: (1) a concurrent TEC perturbation at all latitudes simultaneously; (2) one LSTID propagating toward the equator, having very large wave parameters (wavelength: ≈3600 km, period: ≈120 min, and speed: ≈500 m/s); and (3) several LSTIDs propagating toward the equator with typical wave parameters (wavelength: ≈2100 km, period: ≈60 min, and speed ≈600 m/s). The third type of LSTIDs is considered to be exited as most LSTIDs either due to variations in the Joule heating or variations in the Lorentz force, whereas the first two perturbation types are rather unusual in their appearance. They occurred during the partial recovery phase when the geomagnetic perturbations were minor and the interplanetary magnetic field turned northward. A westward prompt penetration electric field is considered to excite the first perturbation signature, which indicates a sudden TEC depletion. For the second LSTID type, variations in the Lorentz force because of perturbed electric fields and a minor particle precipitation effect are extracted as possible excitation mechanisms.

Annual and semi-annual Sq variations at 96° MM MAGDAS I and II stations in Africa

The quiet daily variations of the geomagnetic field (Sq) have been studied by using the geomagnetic data of the 10 International Quietest Days. Geomagnetic data from MAGDAS I and II stations—ten stations were selected around the 96° magnetic meridian (MM)—over Africa have been analyzed from September 2008 to August 2009. The analysis of this unique data set clarifies the characteristics of the Sq variations over the African sector for the first time by observational geomagnetic data. In this paper, we found that Sq(H) and Sq(D) show a predominantly annual variation. The most interesting result, and a new finding in the African sector, is the appearance of two vortices in the day lit southern hemisphere during spring. Further data analysis also revealed many other interesting characteristics for the Sq over the African sector.

Signature of the coronal hole near the north crest equatorial anomaly over Egypt during the strong geomagnetic storm 5 April 2010

In this paper we study the ionospheric-magnetic disturbance during a strong magnetic storm on 5 April 2010 associated to a coronal hole. The Earth was under the influence of a high speed solar wind stream during four days, and IMF was southward during a very long period. The variation of the disturbed magnetic observations and GPS-TEC are compared with the variation of quiet days during the same month in order to obtain the characteristics of GPS-TEC and magnetic disturbances due to the coronal hole effect. We use multi-instruments as SCINDA-GPS station at Helwan, Egypt (29.86 N, 31.32 E) and ASW-MAGDAS station at Aswan, Egypt (23.59 N, 32.51 E) in the equatorial region. At the beginning of the storm our data highlights the effect of the prompt penetration of the magnetosphere electric field which strongly increases the TEC. During the recovery phase of the storm, we observe on TEC and magnetic data, the signature of the ionospheric disturbance dynamo due to wind produced by Joule heating in the auroral zone. It is the first time that we observe an anti-Sq circulation on magnetic data during four consecutive days associated to the high speed solar wind streams.

Determination of suitable types of solar cells for optimal outdoor performance in desert climate

To choose the most suitable solar cell for desert climate, measurements and analysis of the integrated spectral response (ISR) and the electrical power over 32 spectral bands for monocrystalline, polycrystalline and amorphous solar cells have been carried out in Helwan during several seasons under different environmental conditions. The results of ISR show that while the amorphous silicon solar cell is sensitive in the visible part of the spectrum with maximum sensitivity at wavelength (λ=0.522 μm), the polycrystalline silicon solar cell shows remarkable sensitivity in the infra-red region with maximum sensitivity at (λ=0.922 μm) and the monocrystalline silicon solar cell is more sensitive in the near infra-red spectrum with maximum value of sensitivity at (λ=0.704 μm). Deviations were found in the behavior between the ISR and the electrical output power in the measured bands.

Ionospheric imaging in Africa

Accurate ionospheric specification is necessary for improving human activities such as radar detection, navigation, and Earth observation. This is of particular importance in Africa, where strong plasma density gradients exist due to the equatorial ionization anomaly. In this paper the accuracy of three-dimensional ionospheric images is assessed over a 2 week test period (2-16 December 2012). These images are produced using differential Global Positioning System (GPS) slant total electron content observations and a time-dependent tomography algorithm. The test period is selected to coincide with a period of increased GPS data availability from the African Geodetic Reference Frame (AFREF) project. A simulation approach that includes the addition of realistic errors is employed in order to provide a ground truth. Results show that the inclusion of observations from the AFREF archive significantly reduces ionospheric specification errors across the African sector, especially in regions that are poorly served by the permanent network of GPS receivers. The permanent network could be improved by adding extra sites and by reducing the number of service outages that affect the existing sites. Key Points Ionospheric image quality in Africa is assessed Simulated and real data are both used An extended receiver network greatly improves accuracy

Signatures of the low-latitude Pi 2 pulsations in Egypt

Abstract To study the activities and the physics of the Earth’s magnetosphere, several types of measurements are made with different kinds of instruments both on earth and in space. Ground based data represent the properties of the solar wind, the Earth’s magnetic field and currents in the magnetosphere. Many of the activities occurring in the magnetosphere are a result of changes in the solar wind. It has been known since the 1860s that the Earth’s magnetic field is fluctuating and during that times the fluctuations are periodical. In this study, a special type of magnetic pulsations in the Earth’s magnetic field called Pi 2 (from MAGDAS stations in Egypt) is investigated and analyzed statistically. We carried out our analysis through two different methods: (i) Fourier transformations and (ii) wavelet power spectrum. The result shows that the Pi 2 observed in the main phase of the geomagnetic storm have larger frequency than those observed in the recovery phase. These results excluded the field line resonance and the plasmapause surface as a possible generation mechanism, and suggest the cavity resonance as a possible generation mechanism of the Pi 2 pulsations at low latitude stations in Egypt.

Analysis of propagation delays of compressional Pi 2 waves between geosynchronous altitude and low latitudes

The propagation of compressional Pi 2 waves in the inner magnetosphere is investigated by analyzing the onset delay times between the ground and the geosynchronous altitude. We use the compressional component (northward) of magnetic data from low-latitude stations and the geosynchronous satellite ETS-VIII (GMLat. = -10.8°, GMLon. = 217.5°). The onset delays are determined by a cross-correlation analysis, and we analyzed the events with high waveform correlations (correlation coefficient greater than 0.75). Some of these high-correlation events have the properties of propagating waves; Pi 2 waveforms at the ground stations and the satellite were synchronized with each other when the data were shifted by onset delays. The results of the statistical analysis show that 87% of the Pi 2 onsets at a ground station (Kuju, GMLat. = 26.13°, GMLon. = 202.96°) were delayed from the Pi 2 onsets at ETS-VIII, and the average of the delay times was 29 sec. This clearly shows Pi 2 onsets (initial perturbations of Pi 2) propagated from the geosynchronous altitude to the low-latitude ground. The delay times tended to be larger around the midnight sector than around the dawn and dusk sectors. These results are consistent with two-dimensional propagation of fast waves estimated by the model of Uozumi et al. (J Geophys Res 114:A11207, 2009). The delay times are nearly identical to the travel time of fast waves from geosynchronous altitude to the low-latitude ground, and the local time variation of the delay shows the azimuthal propagation along the geosynchronous orbit. We conclude that the initial compressional perturbations of Pi 2 waves propagate radially and longitudinally as a fast wave in the inner magnetosphere.

PHOTOVOLTAIC PERFORMANCE UNDER REAL DESERT CONDITIONS NEAR CAIRO

A photovoltaic panel of polycrystalline silicon solar cells from Solarex was installed with a tilt angle of 30°. The temperatures of the centre and side of the panel were measured by two thermocouples, in addition to the global radiation and ambient temperature measurements. The measurements were analyzed to determine empirical models for the temperature effect and the resultant power. It was found that there is a drop in the voltage and power of the photovoltaic panel at noon during the spring and summer seasons.

Development of electromagnetic cascading in the Sun's magnetic field

The study of particle cascading initiated by Extremely High Energy (EHE) photons in the Suns magnetic field offers us an opportunity to study some processes of astrophysical importance in space. This opportunity has beenparticularly useful in investigating the photon content in the EHE cosmic ray spectrum. The processes of magnetic pair creation and photon splitting are the basic mechanisms taken into account in our Monte Carlo simulation code. Such processes have been simulated for primary photons in the magnetic field near the Sun to study the characteristics of the cascading of these extraordinary showers. Upon simulation, such cascading particles produced by primary photons with an energy ≥10 1 9 eV could be detected on the Earths surface within a solid angle of 6.12 x 10 - 4 sr from the Suns position. The characteristics of cascading initiated by photons in such a strong magnetic field near the Sun are discussed.