NISCAIR Online Periodicals Repository Collection: IJRSP Vol.41(5) [October 2012]

Assessment of electromagnetic radiation from base station antennas

Title: Assessment of electromagnetic radiation from base station antennas

Authors: Singh, R K

Abstract: There is a strong perception relating to existence of a high level of non-ionizing electromagnetic radiation in the vicinity of base station antennas. In the present paper, electromagnetic radiation from base station antennas installed for various wireless communication purposes has been investigated based on equivalent isotropically radiated power calculations. For this purpose, a typical wireless communication site has been selected where GSM, CDMA, 3G/UMTS, and WiMAX antennas are installed. The overall ratio of equivalent isotropically radiated power (EIRP) and threshold EIRP combining all services at this particular site has been calculated at ground level and nearby buildings. It has been found that the ratio of EIRP and threshold EIRP is less than unity and thus, the particular site is normally compliant and does not impose any adverse health effects. For general public, the exclusion zone (compliance distance) from GSM, CDMA, 3G/UMTS, and WiMAX antennas have been found at 7.30, 6.076, 7.436, and 6.861 m, respectively.

Page(s): 557-565

A search for precursors of earthquakes from multi-station ULF observations and TEC measurements in India

Title: A search for precursors of earthquakes from multi-station ULF observations and TEC measurements in India

Authors: Chauhan, Vishal; Singh, O P; Pandey, Uma; Singh, Birbal; Arrora, B R; Rawat, Gautam; Pathan, B M; Sinha, A K; Sharma, A K; Patil, A V

Abstract: Ground based observations have been carried out for ultra low frequency (ULF) precursors of earthquakes at four different stations in India, namely Agra (geographic lat 27°N, long 78°E), Guttu (lat 31.53°N, long 78.75°E), Shillong (lat 25.92°N, long 91.88°E) and Kolhapur (lat 16.40°N, long 74.15°E) using identical 3-component search coil magnetometers (f = 0.01-30 Hz) obtained from Lviv Centre of Space Research, Ukraine. An offline analysis of the combined data has been carried out in relation to a major earthquake of magnitude M=7.9 occurred in the neighbouring country China (lat 31°N, long 103.32°E, depth=19 km) under the National Program of Earthquakes Precursors (NPEP) launched in India since May 2009. The results of the analysis show occurrence of amplitude anomalies as precursors whose amplitudes decrease with distance. The precursor periods range between 2 and 5 days and are large for the stations nearer to epicenter. A graphical determination of location of the epicenter has been found to be satisfactory with errors within 20.5%. Further, the total electron content (TEC) data obtained from a dual frequency GPS receiver at Agra station and global ionospheric maps (GIMs) of TEC corresponding to the Wenchuan earthquake have also been analysed. The GIM TEC data have been analysed for five different locations which lie between Agra and the epicenter of the earthquake. The anomalies in TEC data are investigated by using quartile based statistical process. It has been found that GPS and GIM TEC data show anomalous depletions of 02 - 13 days before and anomalous enhancements of 03 - 10 days prior to the occurrence of earthquake.

Page(s): 543-556

Variability of the vertical extent of ionospheric E-layer over a station within equatorial anomaly region

Title: Variability of the vertical extent of ionospheric E-layer over a station within equatorial anomaly region

Authors: Rabiu, A B; Abe, O E; Adeniyi, J O

Abstract: The variability of the vertical extent of the E-layer of the ionosphere (V_E) has been examined within the equatorial ionospheric anomaly region, taken as the difference between 90 km which is the assumed lower boundary of the layer and the virtual height values measured with an ionosonde at Ouagadougou in Burkina Faso, West Africa (geographic lat 12.4°N, long 1.5°W and magnetic dip 5.9°N) for low solar activity year 1985 and high solar activity year 1990. The vertical extent is a measure of the vertical altitude of E-region of the ionosphere. The vertical extent of the E-layer was observed to be high (36-40 km) at sunrise and sunset while low (18-22 km) at noon for both years. Seasonal variation shows that vertical extent of E-layer during the solar minimum (maximum) is higher in September (March) equinox and lower in March (September) equinox. The vertical extent of E-layer has been found to be an unstable membrane as it varied from hour to hour, day to day, month to month and season to season in response to the solar activity. The V_E is thicker in the low solar activity (26.30 ± 3.47 km) than the high solar activity (23.01 ± 2.62 km), which implies that increase/decrease in the solar activity results in decrease/increase in vertical extent of E-layer. Precisely, 5.4% (35.9%) variation in low (high) solar activity is accounted for by the variability in solar activity while the remaining percentage may be due to other factors.

Page(s): 536-542

Response of equatorial electrojet during the super geomagnetic storm of April 2000

Title: Response of equatorial electrojet during the super geomagnetic storm of April 2000

Authors: Rastogi, R G; Chandra, H

Abstract: A major geomagnetic storm associated with coronal mass ejection (CME) occurred with sudden commencement at 1636 hrs UT on 6 April 2000 and a minimum Sym/H index of -300 nT at 0000 hrs UT on 7 April 2000. The event is unique with IMF Bz remaining southward from around 1630 hrs UT till almost midnight. The event is studied from data at a chain of ground magnetometers in the Indian and Pacific longitude sectors and other low latitude stations. The amplitude of SC (H) at low latitude stations was highest at Huancayo (around local mid-day) with a value of about 150 nT and about 45 nT at Tirunelveli in the Indian sector (nighttime). The amplitude of SC in H in the night side Indian sector showed an increase with latitude with a value of about 45 nT near dip equator and increased to about 85 nT near Sq focus. Counter electrojet was seen from 0400 to 1100 hrs UT (maximum value of -70 nT) in the Indian sector and the ionograms at Thumba showed disappearance of Es-q at 1130 hrs LT (0630 hrs UT) and its reappearance at 1630 hrs LT (1130 hrs UT). The long duration counter electrojet in the Indian sector is likely due to disturbance dynamo fields. Strong counter electrojet event from 0000 to 0300 hrs UT (maximum value of about -300 nT) in the far-east sector is probably due to prompt penetration electric field (over shielding) associated with the sudden northward turning of IMF Bz around midnight.

Page(s): 524-535