Indian Journal of Radio & Space Physics

Total visitors: 1,138  since 25-08-05

ISSN : 0367-8393

 

       CODEN : IJRSAK

VOLUME 34

NUMBER 4

AUGUST 2005

 

CONTENTS

Editorial: Antarctica: A fascinating continent for global science

219

        P C Pandey* 

 

Simultaneous ULF/VLF amplitude anomalies observed during moderate earthquakes in Indian region

221 

        Birbal Singh*, Vinod Kushwah, Vikram Singh, Manoj Tomar & M Hayakawa

 

Multi-frequency HF Doppler radar observations of vertical plasma drift—Preliminary results

233 

        S R Prabhakaran Nayar*, C V Sreehari, S Shibu, C V Devassia, K S V Subba Rao & S V Mohankumar  

 

 

Investigation of scattering characteristics for a conducting sphere moving at high velocity

243

        P Yang* & Y Li 

 

Lightning produced nitrogen oxides in the lower atmosphere—An overview

248

        R P Singh*, R P Patel, Rajesh Singh & R N Singh 

 

Methane emission from the rice fields of West Bengal over a decade

255

        N N Purkait, M K Sengupta, Sanghamitra De & D K Chakrabarty* 

 

Comparison of total column water vapour measured at New Delhi, Maitri (Antarctica), Leh and Hanle

264

        Sachin D Ghude, S L Jain*, B C Arya & M M Bajaj 

 

Estimation of sub-soil temperature using air temperature

269

        P Tessy Chacko* & G Renuka 

 

Heat storage at sub-surface soil and microclimate at Thiruvananthapuram, India

274

        S Abraham Thambi Raja* & G Renuka 

 

Shorting pin loaded microstrip antenna for dual-band operation

281

        Rajesh K Vishwakarma & Babau R Vishvakarma* 

 

Higher order mode analysis of circular coaxial waveguides using finite difference

285

        Anil Kumar Pandey, Kartik Adinarayanan, S B Chakrabarty*, Arun Kumar & S B Sharma 

 

__________

 

*Corresponding authors

 

 


Indian Journal of Radio & Space Physics

Vol. 34, August 2005, pp. 221-232

 

Simultaneous ULF/VLF amplitude anomalies observed during moderate earthquakes in Indian region*

 

Birbal Singh

Department of Electronics & Communication Engineering, Faculty of Engineering  & Technology,
R B S College, Bichpuri, Agra 283 105, India

and

Vinod Kushwah, Vikram Singh & Manoj Tomar

Department of Physics, R B S College, Bichpuri, Agra 283 105, India

and

M Hayakawa

Department of Electronics Engineering, The University of Electro-Communications, Chofu, Tokyo 182, Japan

Received 1 June 2004; revised 18 January 2005; accepted 3 February 2005

A three-component search coil magnetometer to monitor ultra low frequency (ULF) magnetic field emissions (frequency = 0.01-30 Hz) and an Absolute phase and amplitude data logger (AbsPAL) to monitor the phase and amplitude variation of very low frequency (VLF) 19.8 kHz fixed frequency NWC (Australia) transmitter signals have been installed at Bichpuri, Agra (Geograph Lat. 27.2°N, Long. 78°E) in India and regular simultaneous observations have been taken since 1 Aug. 2002. The analysis of the nighttime VLF amplitude data has been carried out for the initial period of nine months between 1 Aug. 2002 and 30 Apr. 2003 and it is seen that the amplitude decreased abnormally by 1-10 dB from normal nighttime daily averages on six days during the whole period under consideration. The results of ULF data analysis show that the background magnetic field amplitudes of the three components, which are usually low, in the range of 0.03-0.30 nT are enhanced to the range of 0.26-0.96 nT, either on the same days or within ± 2 days of the decrease in amplitude of the VLF signal. The possible causes for the observed ULF/VLF amplitude anomalies are examined and it is found that they are caused by moderate seismic activities that occurred along the VLF propagation path in the region. The statistical analysis of the data using mean and standard deviation around the mean is carried out, which supports the results satisfactorily.

Keywords: ULF/VLF amplitude, Magnetic field emission, Ionosphere, Earthquakes

PACS No: 91.30 Px; 94.20 Yx

 


Indian Journal of Radio & Space Physics

Vol. 34, August 2005, pp. 233-242

 

 

Multi-frequency HF Doppler radar observations of vertical plasma drift—Preliminary results

S R Prabhakaran Nayar, C V Sreehari & S Shibu

Department of Physics, University of Kerala, Trivandrum 695 581

e-mail: srp@md2.vsnl.net.in

and

C V Devassia, K S V Subba Rao & S V Mohankumar

Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695 022

Received 23 April 2004; revised 9 August 2004; accepted 3 January 2005

A multi-frequency HF Doppler radar system suitable for ionospheric F-region vertical drift studies has been installed at the magnetic equatorial station, Trivandrum, India (8.33° N, 77° E, dip 0.4° N). The speciality of the system is the usage of three frequencies (2.5 MHz, 3.5 MHz and 4.5 MHz) in a nearly simultaneous manner, which gives F-region vertical plasma drifts at three successively higher altitudes over the sounding station. The radar is mainly used to study the nocturnal vertical drift characteristics such as pre-reversal enhancement, onset of spread-F, short-period fluctuations, etc. An equinoctial maximum in pre-reversal enhancement of vertical drift is noted. Characteristics of short-period fluctuations are studied. Preliminary results of multi-frequency sounding are presented.

Keywords: Equatorial ionosphere, HF Doppler radar, Vertical drift, Pre-reversal enhancement

PACS No.: 94.20 Gg; 94.20 Ji;  94.20Tt

IPC Code: G01S13/02; G01S13/12; G01S13/53

 

Indian Journal of Radio & Space Physics

Vol. 34, August 2005, pp. 243-247

 

Investigation of scattering characteristics for a conducting
sphere moving at high velocity

 

P Yang & Y Li

Box 106, School of Telecommunications Engineering, Xidian University, Xi’an, 710071, China

E-mail: ypbest@yahoo.com.cn

Received 10 November 2004; revised 18 May 2005; accepted 4 July 2005

The scattered field of a conducting sphere moving at high velocity is investigated, when the incident wave is of arbitrary frequency. First the transformation of coordinates, transformation of vectors and the electromagnetic transformation are derived in detail, when one system of coordinates moves to another one along their Z-axis. The transformation of trigonometric function and that of the components of vector in spherical coordinates are presented for the first time. These transformations establish a theoretic basis for studying the scattered field by a target moving in high velocity. Utilizing the reference, the scattering characteristics of a conducting sphere moving in high velocity are investigated in detail. The expression of scattering section is obtained and simulations of that are presented. Results show that the forward scattered field is larger than that of the backward, as the sphere moves at a high velocity. The forward and backward scattered fields are not much influenced by the operating frequency and the Doppler effect plays the main role. The second radiation on the surface of the target is mainly electric dipole radiation.

Keywords: Electromagnetic scattering, trigonometric function transformation

PACS No.: 47.85 Gj

 


Indian Journal of Radio & Space Physics

Vol. 34, August 2005, pp. 248-254

 

 

Lightning produced nitrogen oxides in the lower atmosphere – An overview

R P Singh & R P Patel

Atmospheric Research Lab., Physics Department, Banaras Hindu University, Varanasi 221 005

and

Rajesh Singh

Indian Institute of Geomagnetism, New Panvel, Navi Mumbai 410 218

and

R N Singh

Ex-Emeritus Scientist, CSIR and AICTE, Banaras Hindu University, Varanasi 221 005

Received 17 November 2003; revised 30 March 2005; accepted 21 April 2005

Nitrogen oxides are dominant constituents of the atmospheric lower regions namely, troposphere and stratosphere. Lightning phenomenon plays an important role in governing the odd nitrogen oxides in the lower atmosphere and hence in global change process. In this paper, studies made by different workers on the lightning produced nitrogen oxides and other related phenomena have been reviewed. Studies in this direction are very sparse in India. Besides the ground based, balloon-borne and satellite-borne measurements, aircraft measurements in India and elsewhere are essential for providing global information. In order to make reliable measurements the experimental site should be in remote areas free from heavy industrial pollution, so that the contaminations due to direct influence of anthropogenic activities are avoided.

Keywords: Lightning, Nitrogen oxides, Atmospheric chemistry, Industrial pollution

PACS NO: 92.60Pw; 92.60.Hp; 92.70.Cp

IPC Code: G 01W1/08

 

 

Indian Journal of Radio & Space Physics

Vol. 34, August 2005, pp. 255-263

 

 

Methane emission from the rice fields of West Bengal over a decade

 

N N Purkait, M K Sengupta & Sanghamitra De

S K Mitra Centre for Research in Space Environment, Institute of Radiophysics and Electronics, University of Kolkata,
92, Acharya Prafulla Chandra Road, Kolkata 700 009

and

D K Chakrabarty

Centre for Environment Survey, Vidyanagar Society 29/251, Ahmedabad 380 015

Received 29 April 2004; revised 14 September 2004; accepted 16 December 2004

The results of methane emission measurements from the farmer’s paddy fields in West Bengal during 1990-2001 are presented. Measurements were made by static chamber technique. The mean yearly value from 1990 to 2001 is found to be 1.09 Tg. There is almost no change in the methane emission although there has been increase in harvested area during this period. Data obtained in this work will be a valuable input for making a reliable methane inventory for the Indian sub-continent.

Keywords: Methane emission, Rice paddy field, West Bengal State

PACS No.: 89.60.Fe; 92.60.Sz; 92.70.Cp


Indian Journal of Radio & Space Physics

Vol. 34, August 2005, pp. 264-268

 

 

Comparison of total column water vapour measured at New Delhi,
Maitri (Antarctica), Leh and Hanle

 

Sachin D Ghude, S L Jain & B C Arya

Radio and Atmospheric Sciences Division, National Physical Laboratory, New Delhi 110 012 (India)

Email: sachinghude@mail.nplindia.ernet.in

and

M M Bajaj

Department of Physics and Astrophysics, University of Delhi, Delhi 110 007

Received 27 May 2004; accepted 6 April 2005

Measurement of total column water vapour made over Maitri (70.44°S, 11.45°E), Antarctica, using MICROTOPS-II sun-photometer during 2002 showed that the monthly average concentration of water vapour varied from 0.67 cm to 0.18 cm. Water vapour concentration was found varying significantly with season and time of the day. The measurements carried out during 1997, 2002 and 2003 during voyage from Delhi to Antarctica revealed that the concentration of water vapour decreases with increasing latitudes. Water vapour concentration was also found to be in correlation with corresponding temperature. The water vapour over Antarctica was also compared with that over Delhi as well as with high altitude stations, Leh (34°15¢N, 77°56¢E, 3.311 km amsl), and Hanle (32°47¢N, 78°58¢E, 4.50 km amsl), which showed that the concentration of water vapour at Leh, Hanle and Maitri is of same order and very low compared to that over Delhi.

Keywords: Water vapour, Greenhouse gases, Antarctica, Climate and global change, Hydrological cycle

PACS No.: 92.60.Jq; 92.60.Ek

IPC Code : G 0 1 W ½

 

Indian Journal of Radio & Space Physics

Vol. 34, August 2005, pp. 269-273

 

 

Estimation of sub-soil temperature using air temperature

 

P Tessy Chacko & G Renuka

Department of Physics, University of Kerala, Kariavattom 695 581, India

Received 2 December 2004, accepted 3 June 2005

Extreme variability in the temperature of soil and air affects plant life. An attempt has been made to develop regression models to estimate the soil temperature at 5 and 10 cm depth using air temperature. Soil and air temperature data for the period 1998-2002 were collected from Vellanikara and Vellayani stations in central and south of Kerala state, respectively. A close resemblance in the weekly observed and computed sub-soil temperatures has been established.

Keywords: Sub-soil temperature, Air temperature, Regression analysis

PACS No.: 92.40.Lg; 94.40.Je

IPC Code: G 01 S 17/00


Indian Journal of Radio & Space Physics

Vol. 34, August  2005, pp. 274-280

 

 

Heat storage at sub-surface soil and microclimate at Thiruvananthapuram, India

S Abraham Thambi Raja

Department of Physics, Lekshmipuram College of Arts and Science, Neyyoor 629 802, Tamil Nadu

and

G Renuka

Department of Physics, University of Kerala, Kariavattom 695 581, Kerala

Received 3 October 2003; revised 8 November 2004; accepted 14 January 2005

During heat flux study at Thiruvananthapuram, in order to attain an accurate value for ground heat flux G, heat storage term DS of the energy balance equation was estimated and found to vary between 40 and 70% of ground heat flux, and 4 and 6% of the net radiation. Also, value of DS was found to have a maximum of 117 W/m2 and a minimum of 0.4 W/m2. An empirical relation between G* (G +DS) and R, net radiation, is deduced and compared with available results. From a detailed picture of microclimate near soil-air interface, it was found that the surface energy budget was governed by the surface condition and evaporation was the most important factor in the energy balance during humid conditions. Also intense solar heating and wetness of surfaces were factors influencing ground heat flux.

Keywords: Ground heat flux, Heat storage term, Microclimate, Soil-air interface

PACS No: 92.40. Lg; 92.60.Ry

 

 

Indian Journal of Radio & Space Physics

Vol. 34, August 2005, pp. 281-284

 

 

Shorting pin loaded microstrip antenna for dual-band operation

 

Rajesh K Vishwakarma & Babau R Vishvakarma*

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

*E-mail: brvish@bhu.ac.in

Received 24 May 2004; revised 11 August 2004; accepted 2 November 2004

The series and shunt inductivity introduced by the probe and shorting pin respectively, in a single-feed shorted rectangular microstrip antenna has been evaluated theoretically using transmission line method. The proposed structure provides compact dual band operation using single feed mechanism. The input impedance, VSWR, is calculated theoretically. It is found that the ratio of the resonant frequencies highly depends on the position of shorting pin.

Keywords: Microstrip antenna, Shorting pins, Dual band antenna, Transmission line

PACS No: 84.40. Ba


 

 

Indian Journal of Radio & Space Physics

Vol. 34, August 2005, pp. 285-288

 

 

Higher order mode analysis of circular coaxial waveguides
using finite difference

 

Anil Kumar Pandey, Kartik Adinarayanan, S B Chakrabarty, Arun Kumar & S B Sharma

Antenna System Group, Space Applications Center, Ahmedabad 380 015, India

Received 26 May 2004; revised 13 October 2004; accepted 15 February 2005

This paper presents a simple technique to evaluate the cut-off wavelengths of circular coaxial waveguides employing the method of finite difference. Curvilinear rectangular meshing has been employed to subdivide the cross-sectional region between the two conductors. Helmholtz equation in polar form is solved with the appropriate boundary condition to evaluate the cut-off wavenumbers and correspondingly the cut-off wavelengths for TE and TM modes. Plots of cut-off wavelengths of few modes for various ratios of outer-to-inner radii are depicted. The data obtained from analytical expressions are compared to justify the validity of the analysis.

Keywords: Circular coaxial waveguide, Finite difference, Cut-off wavelengths

PACS No: 84.40Az

IPC Code: H01P3/00