Indian Journal of Radio & Space Physics

(CODEN:IJRSAK        ISSN : 0367-8393)

VOLUME 34

NUMBER 6

DECEMBER 2005

 

CONTENTS

 

Guest Editorial: GPS – A unique facility for positioning and timing as well as an interesting tool for research

 

385

        P Banerjee*

 

 

Sprites and elves-associated sferics produced by quasi-electrostatic thundercloud fields – A review

 

387

        T Datta, A Bhattacharya, R Bhattacharya, R Das, S De & A B Bhattacharya*

 

 

Ionospheric total electron content measurement in Malaysian region during high solar activity using GPS receiver

 

399

        Rashmi Wahi*, Smita Dubey & A K Gwal

 

 

Study of amplitude and phase scintillation at GPS frequency

402

        Smita Dubey*, Rashmi Wahi, Ekkaphon Mingkhwan & A K Gwal

 

 

Studies on the integrated field intensity of ELF-VLF sferics at Tripura, India

408

        B K De, M Pal, S S De*, R Bera, S K Adhikari, A Guha & S K Sarkar

 

 

Studies on non-linear heating of the lower ionosphere during interaction between HF and ELF signals

 

413

        S S De*, S K Adhikari, A Debnath, P Das & B K De

 

 

Effect of air gap on the performance of circular sector antennas

417

        V K Tiwari*, Aradhana Kimothi, D Bhatnagar, J S Saini, V K Saxena &
P Kumar

 

 

Analysis of slot-loaded rectangular microstrip patch antenna

424

        Shivnarayan, Shasank Sharma & Babau R Vishvakarma*

 

 

Effect of environmental changes on the performance of ILS located at Hyderabad airport

 

431

        K Ramalingam, G Sashibhushana Rao, K Ramakrishna & A D Sarma*

 

 

Influence of nationwide truck strike on black carbon aerosols over urban environment of Hyderabad, India

 

435

        K Madhavi Latha*, K V S Badarinath

 

 

Theoretical modeling of a dielectric-loaded box-horn applicator for hyperthermia treatment of tumors in thorax region

 

438

        Ramesh Chandra Gupta* & S P Singh

 

 

 

 

Annual Index

447

 

 

Referees of the year

451

 

 

__________

 

*Corresponding authors

 

 

Indian Journal of Radio & Space Physics

Vol. 34, December 2005, pp. 387-398

 

 

Sprites and elves-associated sferics produced by quasi-electrostatic

thundercloud fields—A review

 

T Datta1, A Bhattacharya2, R Bhattacharya3, R Das, S De & A B Bhattacharya

Department of Physics, Kalyani University, Kalyani 741 235, West Bengal, India

1Department of Physics, Serampore College, Serampore 712 201 (WB), India

2Panighata U.D.M High School, Nadia 741 181 (WB), India

3Department of Environmental science, Kalyani University, Kalyani 741 235 (WB), India

Received 14 May 2004; revised 13 December 2004; accepted 15 March 2005

Investigations on sprites and elves glow and a comparison of the observational work obtained at various locations by different workers are reported in this review. As the characteristic of these extraordinary phenomena is not yet well understood, an interpretation of the results is attempted from both experimental and theoretical points of view. The paper critically considers the latitudinal variations of lightning characteristics, as lightning flashes have a reported good relationship with the concerned unusual sprites and elves glow. It also discusses temporal variations of electron density, which is highly relevant as the extraordinary glow experienced between the cloud tops and the ionosphere. Subsequently, the sprites and elves associated sferics data in conjunction with electric and magnetic fields have been studied and the role of quasi-electrostatic thundercloud fields have been critically examined to focus this mysterious mesospheric glow.

Keywords: Sprites, Elves, Thunderclouds, Sferics

PACS No.: 92.60.Nv; 92.60.Pw

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, December 2005, pp. 399-401

 

 

Ionospheric total electron content measurement in Malaysian region

during high solar activity using GPS receiver

 

Rashmi Wahi, Smita Dubey & A K Gwal

Space Science Laboratory, Department of Physics, Barkatullah University, Bhopal 462 024 (M.P), India

Email: rashmiwahi@yahoo.com

Received 3 September 2004; revised 15 April 2005; accepted 3 May 2005

The ionospheric total electron content (TEC) in Malaysian region is examined using Global Positioning System (GPS) receiver. The TEC data of solar maximum (2000-2001) from Marak Parak, Sabah, Malaysia are used. In this paper we study the diurnal, seasonal and annual behaviour of ionospheric total electron content. Purpose of this study is to investigate the variation of TEC during high solar active period in this region.

Key words: Total electron content, Solar activity, Global positioning system

PACS No.: 94.20. -y; 94.20. Bb

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, December 2005, pp. 402-407

 

 

 

Study of amplitude and phase scintillation at GPS frequency

 

Smita Dubey1, Rashmi Wahi1, Ekkaphon Mingkhwan2 & A K Gwal1

1Space Science Laboratory, Department of Physics, Barkatullah University, Bhopal 462 026, India

2Military Research and Development Centre, Bangkok, Thailand

Email: smitadubey@yahoo.com

Received 3 September 2004; revised 23 February 2005; accepted 29 July 2005

When a radio wave at L-band frequency passes through the entire ionospheric region, it is affected by the electron density irregularities, which are present in the ionosphere and generate amplitude and phase scintillation of GPS signals. This is especially true during the nighttime. The magnitude of amplitude and phase scintillation and the temporal structure of scintillations need to be specified and predicted to provide support to operational communication and navigation system. Amplitude and phase fluctuation at the GPS frequency at Chiang Rai (19.57°N, 99.52°E), Thailand is described in this paper. It was found that higher amplitude fluctuation level could be observed only in equinox and winter, while S4 is less than 0.4 in summer months.

Keywords: Ionosphere, F-region, GPS frequency, GPS

PACS No: 94.20.S; 94.20.J

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, December 2005, pp. 408-412

 

 

Studies on the integrated field intensity of ELF-VLF sferics at Tripura*, India

B K De & M Pal

Tripura University, Suryamaninagar 799 130, Tripura West, India

and

S S De, R Bera, S K Adhikari & A Guha

Centre of Advanced Study in Radio Physics and Electronics, University of Calcutta, Kolkata 700 009, India

and

S K Sarkar

Department of Physics, University of Calcutta, Kolkata 700 009, India

Received 14 June 2004; revised 13 December 2004; accepted 29 July 2005

The results of observation of the Integrated Field Intensity of Sferics (IFIS) at 0.9, 3, 6, 9 and 12 kHz at Tripura (latitude: 23 oN) are reported here. Some specific characteristics of ELF-VLF atmospherics found from this hilly place are presented, along with a brief description of the experimental set-up for their detection.

Key word: Atmospheric noise, ELF-VLF sferics, Sferics

PACS No: 92.60.Ta; 92.60.Pw

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, December 2005, pp. 413-416

 

 

 

Studies on non-linear heating of the lower ionosphere during
interaction between HF and ELF signals

 

S S De, S K Adhikari, A Debnath & P Das

Centre of Advanced Study in Radio Physics and Electronics, University of Calcutta, Kolkata 700 009, India

and

B K De

Tripura University, Suryamaninagar 799 130, Tripura West, India

Received 18 June 2004; revised 19 November 2004; accepted 29 July 2005

Non-linear interaction between Schumann resonances (SR) and high frequency round-the-world signals (RWS) in the lower ionosphere yields the ELF spectra that correspond to the three first modes of Schumann resonances. The phenomenon resembles Luxembourg effect between Schumann resonances and HF signals. The intensity of natural electromagnetic field (SR field) produced by thunderstorm activity is strong enough to give rise to non-linear effects in the D-layer. As a result, there will be heating of electrons by the ELF oscillations of SR fields (Es). The fair-weather electric field (E0) also initiates the process of heating in the D-layer. The influence of this field gives a linear dependence of electron temperature fluctuations on the field strength on SR. These lead to non-linear effects comprising the variations of electron temperature, effective collision frequency and conductivity of the medium. Also, there will be modulation of HF waves by ELF signals.

Keywords: Lower ionospheric heating, HF Signal, ELF Signal, Ionospheric heating

PACS No: 92.60.Ta; 92.70-j

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, December 2005, pp. 417-423

 

 

Effect of air gap on the performance of circular sector antennas

V K Tiwari, Aradhana Kimothi, D Bhatnagar, J S Saini & V K Saxena

Microwave Laboratory, Department of Physics, University of Rajasthan, Jaipur 302 004

and

P Kumar

Communication System Group, ISRO Satellite Center, Banglore560 017, India

Received 21 March 2005; revised 14 June 2005; accepted 9 August 2005

Theoretical analysis of a circular sector microstrip antenna having sector angle (a) and an air gap (ha) between substrate material and ground plane is carried out by applying cavity-model-based modal expansion technique. Expressions for different antenna parameters are derived in TM11 mode of excitation and the theoretical results are compared with simulated results. Average differences in computed and simulated resonance frequency, input impedance, directivity and bandwidth values for the sector geometry with air gap are found to be1.3%, 10.25%, 0.75% and 1.9%, respectively. This validates the accuracy in proposed analysis technique for the present geometry.

Keywords: Microstrip antenna, Cavity model and radiation patterns, Input impedance

PACS No.: 84.40 Ba, 75.50 Gg

IPC Code: H01 Q9/00; H01 Q21/00; H01 Q23/00

 

 

Indian Journal of Radio & Space Physics

Vol. 34, December 2005, pp. 424-430

 

 

Analysis of slot-loaded rectangular microstrip patch antenna

 

Shivnarayan, Shashank Sharma & Babau R Vishvakarma

Department of Electronics Engineering, Institute of Technology, Banaras Hindu University, Varanasi 221 005, India

E-mail: brvish@bhu.ac.in

Received 23 November 2004; revised 17 February 2005; accepted 21 April 2005

In the present paper, the analysis of a slot-loaded rectangular microstrip patch antenna using equivalent circuit concept is presented. The slot is taken as a capacitive reactance on the patch. It is found that the resonance frequency decreases with increasing slot width for a given slot length. The decrease in the resonance frequency is in the higher side for longer slot length, whereas it is on the minimum side for the lower slot length. It is found that VSWR remains almost invariant with slot width and slot length. The impedance increases almost linearly with the slot width, but inversely with the slot length.

Keywords: Slot-loaded patch, Rectangular microstrip antenna, Microstrip antenna

PACS No.: 84.40 Ba

IPC Code: H01Q9/00; H01Q21/00; H01Q23/00

 

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, December 2005, pp. 431-434

 

 

Effect of environmental changes on the performance of ILS

located at Hyderabad airport

 

K Ramalingam, G Sasibhushana Rao & K Ramakrishna

Airports Authority of India, Hyderabad Airport, Hyderabad 500 016

and

A D Sarma

R & T Unit for Navigational Electronics, Osmania University, Hyderabad 500 007

E-mail: ad_sarma@yahoo.com

Received 27 July 2004; revised 14 September 2005; accepted 7 October 2005

In civil aviation, the existing precision approach (PA) landing system equipment has certain limitations due to ground environment, which affects the performance of the equipment. The effect of changes in the environment conditions surrounding the airport on Instrumental Landing System (ILS) course structure has been presented by comparing the calibrated and measured data at Hyderabad airport (India). The field strength data are acquired using the NORMAC ILS signal field test receiver and compared with the calibration aircraft (AVRO HS-748) data. Performance of the existing ILS is analyzed and the results confirm the effect of environmental changes on the ILS course structure.

Keywords: CNS, Precision approach, ILS signal, DDM, Localizer, Multipath, GPS

PACS No: 07.87.+V, 07.89.+b,

IPC Code: G01S1/08; G01S1/12; G01S5/00

 

Indian Journal of Radio Space Physics

Vol. 34, December, 2005, pp. 435-437

 

 

Influence of nationwide truck strike on black carbon aerosols over urban environment of Hyderabad, India

K Madhavi Latha & K V S Badarinath

Forestry & Ecology Division, National Remote Sensing Agency, Balanagar, Hyderabad  500 037, India

Received 8 September 2004; revised 13 May 2005; accepted 19 October 2005

Black carbon (BC) aerosols have a major impact on human health besides global and regional climate. Measurements on spatial distribution of BC remains poor and severely hampers attempts to assess its radiative effects and the situation can be improved by more measurements of BC aerosols across the globe. A study has been carried out in the urban area, Hyderabad to assess the impact of nation-wide truck strike in August 2004 on ambient BC concentrations. The results indicate significant reduction in the BC loading associated with the withdrawal of the trucks. The decrease in BC concentrations has been observed to be gradual while the recovery was almost immediate after the strike was called off. The study provides information on influence of anthropogenic activities such as absence of diesel trucks on BC aerosols in urban areas.

Keywords: Black carbon, Trucks strike, Fossil fuel combustion, Vehicular exhausts

PACS No: 90.60.Sz

 

Indian Journal of Radio & Space Physics

Vol. 34, December 2005, pp. 438-445

 

 

Theoretical modeling of a dielectric-loaded box-horn applicator for hyperthermia treatment of tumors in thorax region

Ramesh Chandra Gupta

Department of Electronics Engineering
Institute of Technology, Banaras Hindu University Varanasi (UP) 221 005, India

and

S P Singh

Department of Electronics Engineering
Institute of Technology, Banaras Hindu University, Varanasi (UP) 221 005, India

Received 10 January 2005; revised 10 August 2005; accepted 21 October 2005

This paper presents theoretical analysis of the specific absorption rate (SAR) distribution in three-layered tissue (fat, muscle and lung layers as in thorax region) in direct contact with a box-horn applicator for hyperthermia treatment of cancerous tumor. The box-horn is assumed to be filled with dielectric (ceramic NPOT-96) to provide a better impedance match to bio-media. The present analysis is based on plane wave spectral technique. The spatial distribution of SAR in fat, muscle and lung layers are computed and reported at 433 and 2450 MHz. Wider SAR-distribution in each of the bio-layers in cross-sectional area and higher penetration depth in lung are observed at 433 MHz in comparison to those at 2450 MHz for dielectric-loaded box-horn. The normalized SAR distributions are also reported for various tissues (fat/muscle/lung layers) at the same depth in order to make a comparative study in these tissues. A modified box-horn, in which the horn is flared in both E- and H-planes is also considered. The effect of substituting pyramidal horn in place of H-plane sectoral horn in the design of box-horn on the SAR distribution is also examined. The results have been validated against available published results in the literature.

Keywords: Bio-media, cancer, dielectric-loaded box-horn, hyperthermia, plane wave spectra, specific absorption rate (SAR)

PACS No.: 84.40.Ba, 84.40.Az