Indian Journal of Radio & Space Physics

 

VOLUME 31

NUMBER 2

APRIL 2002

 

CONTENTS

 

On the eastward geomagnetic field variations at electrojet stations

67           

  R G Rastogi & R J Stening

 

 

Resonance energy, growth rate and magnetic field intensity of the ELF emissions at low latitude

                 75

D K Singh & R P Singh

 

 

Solar eclipse induced changes in aerosol extinction profiles:A case study of 11 Aug. 1999 solar eclipse using lidar at a tropical station Trivandrum, India

              82

M Satyanarayana, S Veerabuthiran, D Ramakrishna Rao, B Presennakumar,

P Sreelatha & K S Appu

 

 

Measurements of dry deposition of gaseous and particulate sulphur on marble at a suburban site

 

88

Ranjit Kumar, Abha Rani, S P Singh, K Maharaj Kumari & S S Srivastava

 

Chemical composition of atmospheric aerosols at New Delhi

93

Ranu Gadi, A K Sarkar, B S Gera, A P Mitra & D C Parashar

 

 

Emission behaviour of foam covered water surface at microwave frequencies

98

O P N Calla & Ishwar Rajesh

 

 

 

Notes

 

Association between geomagnetic activity and surface temperature

104

Indira Joshi, Pricilla Paul & A D Tillu

 

 

Rain attenuation studies at 11.7 GHz over southern India

107

S Vijaya Bhaskara Rao, T Rama Rao, I V Subba Reddy, M V S N Prasad,

V Gunasekhara Reddy & B M Reddy

 

 

 

Commentary

 

Ozone depletion: Its consequences and recovery measures

110

N C Mondal

 

 

 


Indian Journal of Radio & Space Physics

Vol. 31, April 2002, pp. 67-74

 

 

On the eastward geomagnetic field variations at electrojet stations

R G Rastogi* & R J Stening

School of Physics, The University of New South Wales, Sydney, 2052, Australia

Received 8 May 2001; revised 18 October 2001; accepted 15 December 2001

The paper describes the daily and seasonal variations of declination (or eastward geomagnetic field) at five equatorial electrojet observatories operating during 1958. The daily variation of declination in Central Asian sectors (Addis-Ababa and Trivandrum) showed a completely opposite character between the two solstices. The daily variation of declination at Huancayo showed a strong daytime peak during any of the seasons and at Jarvis during March and December. These abnormalities are suggested to be due to the different ionospheric electric conductivity profiles and due to complex dynamics caused by varying interaction between geographic and magnetic equators at different longitudes.

 

Indian Journal of Radio & Space Physics

Vol. 31, April 2002, pp. 75-81

 

 

Resonance energy, growth rate and magnetic field intensity of the
ELF emissions at low latitude

 

D K Singh

Indian Institute of Tropical Meteorology, Pune 411 008

and

R P Singh

Department of Physics, Banaras Hindu University, Varanasi 221 005

Received 10 January 2001; revised 19 November 2001; accepted 9 January 2002

The extremely low frequency (ELF) emissions are very fascinating natural phenomena. Considering coherent cyclotron resonance mechanism for the generation of ELF emissions, the resonance energy, growth rate and magnetic field intensity at various frequencies of emissions corresponding to low latitude region have been computed. It is observed that both resonant energy and growth rate decrease with increasing frequency as well as L-values. The computed magnetic field intensity of the low latitude ELF emissions in the equatorial plane increases with frequency. These computed intensities have been compared with those observed onboard satellite, and a close agreement is found between them.

 

Indian Journal of Radio & Space Physics

Vol. 31, April 2002, pp. 82-87

 

 

Solar eclipse induced changes in aerosol extinction profiles: A case study of 11 Aug. 1999 solar eclipse
using lidar at a tropical station Trivandrum, India

 

M Satyanarayana, S Veerabuthiran, D Ramakrishna Rao, B Presennakumar & P Sreelatha

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

and

K S Appu

Meteorological Facility/TERLS, Vikram Sarabhai Space Centre, Trivandrum 695 022

Received 23 April 2001; revised 27 August 2001; accepted 9 November 2001

An experiment has been conducted to understand the 11 Aug. 1999 solar eclipse induced changes in the aerosol extinction coefficient in the troposphere and the lower stratosphere using the multiwavelength lidar system designed and developed in-house at a tropical station Trivandrum (8° 33˘N, 77° E). Results of the measurements reveal an increase in aerosol extinction coefficient in the troposphere and a decrease in the lower stratosphere compared to control day. Six high altitude balloon ascents with 1680 MHz radiosonde were conducted from Thumba to study the eclipse induced variations in winds and temperature of the lower atmosphere. The study clearly reveals the cooling of the entire tropospheric layers with maximum of 5° C occurring below 15 km altitude. The changes in the temperature and the relative humidity during the eclipse are the key factors contributed for the observed aerosol extinction coefficient.

 

Indian Journal of Radio & Space Physics

Vol. 31, April 2002, pp. 88-92

 

 

Measurements of dry deposition of gaseous and particulate sulphur on marble at a suburban site

Ranjit Kumar, Abha Rani, S P Singh, K Maharaj Kumari & S S Srivastava

Department of Chemistry, Faculty of Science, Dayalbagh Educational Institute, Dayalbagh, Agra 282 005

Received 9 April 2001; revised 3 September 2001; accepted 12 October 2001

Dry deposition of S (sulphur) as sulphate on white marble (natural surfaces) has been measured at Dayalbagh, a suburban site of semi-arid region of India, in winter season (December 1999-March 2000). Samples were collected by exposing the white marble for 24 h and analyzed by Dionex Dx-500 Ion Chromatograph system. Atmospheric concentration of SO2 was 7.8 ± 2.0 mg m-3 and particulate sulphate was 7.9 ± 1.8 mg m-3. The dry deposition of S as sulphate has been found to be 0.19 ± 0.12 mg m-2 h-1. The percentage contribution of the particulate sulphate (78.9) was higher than that of gas phase (21.1). The calculated dry deposition velocity (Vd) of particulate sulphate has been found to be 0.53 ± 0.27 cm s-1. The Vd calculated by present method is lower than that reported by throughfall method, while Vd range is comparable to other methods like foliar extraction, micrometeorological and surrogate methods

 

 

Indian Journal of Radio & Space Physics

Vol. 31, April 2002, pp. 93-97

 

 

Chemical composition of atmospheric aerosols at New Delhi

Ranu Gadi, A K Sarkar, B S Gera, A P Mitra & D C Parashar

National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012

Received 31 July 2001; revised 27 September 2001; accepted 9 November 2001

Size differentiated measurements of atmospheric aerosols have been done at New Delhi using Anderson sampler. Suspended particulate matter (average 363 mg/m3) is found to have a bimodal distribution with a major part of the aerosols in the fine mode which affects human health. Analysis of F, Cl, NO3, SO4, Na, K, Ca, Mg and NH4 shows that cations are, in general, dominating the anions. The ions NO3, Ca, Mg and Na have bimodal distribution, whereas the other ions are found to have unimodal distribution. Major fraction of Na, Ca and Mg is in the coarse mode showing their soil derived nature, while K, NH4, F, Cl, SO4 and NO3 are predominant in the fine modes due to the anthropogenic activities around the site. High K in the fine mode may be due to dense vegetation around the site and biomass burning in the nearby village.

 

Indian Journal of Radio & Space Physics

Vol. 31, April 2002, pp. 98-103

 

 

 

Emission behaviour of foam covered water surface at microwave frequencies

O P N Calla

International Centre for Radio Science, “OM NIWAS”, A – 23 Shastri Nagar, Jodhpur 342 003

and

Ishwar Rajesh

22, Sun Rise house (behind Arunoday Society), Vallabh Vidya Nagar (Gujrat) 388 120

Received 4 January 2001; revised 31 October 2001; accepted 28 December 2001

An estimation of emissivity of foam covered water surface has been proposed, based on the layered media approach applicable for horizontal and vertical polarization. The results show that the emissivity increases with vertical polarization and has higher value than the horizontal polarization.

 

 

Indian Journal of Radio & Space Physics

Vol. 31, April 2002, pp. 104-106

 

 

Notes

 

Association between geomagnetic activity and surface temperature

Indira Joshi & Pricilla Paul

Indian Institute of Tropical Meteorology, Pashan,

Pune 411 008

 

and

 

A D Tillu

Department of Physics, University of Pune, Pune 411 008

 

Received 29 January 2001; revised 16 January 2002; accepted

4 February 2002

 

The possible relationship between surface temperatures and geomagnetic field variations has been studied. Daily surface temperature data for Pune for 1998 and 1999 are used in the study. Geomagnetic field variations data were collected using Proton Precession Magnetometer (PPM). In this study May, June, July (representing summer) and December, January, February (representing winter) data are utilized. The increase in surface temperatures in association with increase in geomagnetic field is observed to be more in winter than in summer.

 

 

Indian Journal of Radio & Space Physics

Vol. 31, April 2002, pp. 107-109

 

 

 

Rain attenuation studies at 11.7GHz over southern India

S Vijaya Bhaskara Rao1, T Rama Rao1, I V Subba Reddy1, M V S N Prasad2, V Gunasekhara Reddy1
 
& B M Reddy3

1Department of Physics, S V University, Tirupati 517 502

2Radio & Atmospheric Science Division, National Physical Laboratory, New Delhi 110 012

3National Geophysical Research Institute, Hyderabad 500 007

Received 1 May 2001; revised 31 October 2001;

accepted 9 January 2002

 

Rain attenuation studies were made at 11.7 GHz utilizing INSAT-2C satellite signals over southern India during rain events. The observed cumulative distribution of rain attenuation is compared with prominent prediction models. These are the first results observed on an operational earth-satellite path in India.