Indian Journal of Radio & Space Physics

(Bimonthly)  

CONTENTS

Indian Journal of Radio & Space Physics

Vol. 32, June 2003, pp. 127-134

Destabilization of EIC waves and heating of HPT ions

C S Jayasree & G Renuka

and

C Venugopal

Department of Physics, University of Asmara, South Africa

Received 30 April 2002; revised 9 August 2002; accepted 31 October 2002

The electrostatic ion cyclotron (EIC) instability of hot plasma torus (HPT) particles in the auroral region due to field aligned current (FAC) has been studied. The value of FAC density J_|| is estimated from the high time resolution magnetic field data of DE-1 spacecraft at altitudes ranging from 600 km to 2500 km during the magnetic storm of 21 Mar.1990 during 0001-2000 hrs UT. The FAC destabilizes the EIC wave and the resultant electrostatic turbulence creates an anomalous resistivity. The current driven resistivity produces parallel electric field and high power dissipation. The growth rate of EIC wave decreases as the electron to ion temperature ratio T_e/T_i increases for weak current density. The anomalous resistivity h, parallel electric field E_||, power dissipation P and ion heating rate have been computed. It is found that these parameters decrease as T_e/T_i increases. When the instability is almost shut off, the ion heating and transversely accelerated ions (TAI) are sharply reduced.

Indian Journal of Radio & Space Physics

Vol. 32, June 2003, pp. 135-141

Statistical study on the temporal correlation of different solar parameters with OI 6300 Å line intensity over Calcutta

and its implications

R Chattopadhyay

Haripal G.D. Institution, Khamarchandi, Hooghly (WB) 712 405

and

S K Midya*

Department of Physics, Serampore College, Serampore, Hooghly (WB) 712 201

and

U K De

Atmospheric Science Section, Department of Physics, Jadavpur University, Calcutta 700 032

Received 16 April 2002; revised 4 March 2003; accepted 25 March 2003

The statistical analysis for the correlation between each of three solar parameters (i.e 10.7 cm solar flux, relative sunspot number and solar flare number) and the airglow OI 6300 Å line intensity at Calcutta is presented. As strong correlations amongst the running averages of monthly mean values of all four parameters are found to exist, both in the descending and peak phases of the 21st solar cycle, empirical equations connecting annual running averages of the OI 6300 Å line intensity with annual running averages of the various solar parameters have been found out. The variable parts of the parameters, which are defined here as the original values (raw data) minus the running average value for a particular year, show their periodicity, particularly, in airglow OI 6300 Å line intensity.

Indian Journal of Radio & Space Physics

Vol. 32, June 2003, pp. 142-147

Effect of IMF parameters on F-region drift velocity over low latitude

 B M Vyas & R Pandey

Department of Physics, M L Sukhadia University, Udaipur 313 001

Received 29 April 2002; revised 30 September 2002; accepted 26 December 2002

The effects of various interplanetary magnetic field (IMF) parameters on midnight values of N-S and E-W drift velocity of F-region are studied using the spaced receivers ionospheric drift data collected over a low latitude station, Udaipur (geomagn. lat. 14.5° N), during different seasons of high solar activity period. It is found that both N-S and E-W drift speeds are strongly influenced by the N-S component of IMF. However, the total IMF showed more effect on N-S drift speed as compared to E-W drift. The control of sunward and E-W components on the drift parameters is found to be insignificant. The control of IMF parameters on drift velocity was more prominent in winter compared to other seasons. The present findings have been interpreted in terms of generation of additional electric field at magnetospheric height and its transmission to equatorial ionosphere via polar latitude through a parallel plane transmission line made up of the earth and ionosphere waveguide.

Indian Journal of Radio & Space Physics

Vol. 32, June 2003, pp. 148-153

An ionospheric time delay model based on IRI-90 for space-bound objects within 300 km altitude

A D Sarma, T Madhu & N S Murthy Sarma

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

Received 26 June 2002; revised 6 August 2002; accepted 18 March 2003

A new time delay model is proposed based on International Reference Ionosphere-1990 (IRI-90) electron density model for space-bound objects for any altitude up to 300 km. When limited portion of the ionosphere is considered, Klobuchar’s time delay algorithm is not suitable. The procedure used for developing the a and b coefficients is outlined. Important steps of the proposed algorithm are presented. The predicted and theoretical models compare well. An example estimation is given and the results are found to be encouraging.

Indian Journal of Radio & Space Physics

Vol. 32, June 2003, pp. 154-157

Measurement of atmospheric radio noise field strength during severe meteorological disturbances

R Bhattacharya

Krishnath College, Berhampur, Murshidabad (W B) 742 101

Received 11 March 2002; revised 8 July 2002; accepted 13 November 2002

Atmospheric radio noise field strength in the tropical station Calcutta have been analysed with a special emphasis on its types and forms. Some typical records of its variations during disturbed weather conditions due to monsoon depression and cyclonic storm associated with torrential rainfall are presented.

Indian Journal of Radio & Space Physics

Vol. 32, June 2003, pp. 158-165

Lidar observations on atmospheric dust transported from south-west
Asia to Indian west coast region: A case study of colour rain
event occurred during July 2001

S Veerabuthiran & M Satyanarayana

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

Received 26 April 2002; revised 12 November 2002; accepted 2 December 2002

A dust storm, which originated in the dust bowl of Arabia, Iran, Afghanistan, Pakistan and north-western of parts of India during the month of July 2001, had lifted large quantities of dust into the atmosphere and got transported over long distances. The region on the west coast of India had experienced the interesting phenomenon of “colour rain” due to this dust loading. A typical dust layer had been detected in the lower troposphere using a lidar system located at Trivandrum (8° 33¢N, 77°E) during the night of 24 July 2001 prior to the occurrence of colour rain. The lidar measurements indicated that the dust cloud was present in the 4-5 km altitude range with thickness of a few hundred metres. Air back trajectory computed by the HYSPLIT-4 model using NCEP wind data at the 4500 m level clearly indicated that the dust probably had its origin in the south-west Asia, nine days before the event.

Indian Journal of Radio & Space Physics

Vol. 32, June 2003, pp. 166-171

Some investigations on annular ring microstrip antenna

Binod K Kanaujia & Babau R Vishvakarma

Department of Electronics Engineering, Institute of Technology,

Banaras Hindu University, Varanasi 221 005

Received 19 February 2002; revised 7 May 2002; accepted 11 October 2002

The various parameters of annular ring microstrip antenna such as input impedance, VSWR, return loss, radiation pattern have been theoretically investigated as a function of frequency for different feed locations. It has been observed that resonance occurs at 3.285 GHz which is invariant with feed locations. The antenna behaves as RL network below resonance and as RC network above resonance and shows perfect matching at 3.35 cm feed location from the centre. The percentage bandwidth is found decreasing and the radiated power increasing with increasing b/a ratio.

Indian Journal of Radio & Space Physics

Vol. 32, June 2003, pp. 172-176

Design and fabrication of a low noise amplifier for a microwave receiver

 M K Raina & S S Inamdar

Department of Electronics & Communication, Bharati Vidyapeeth College of Engineering, A-4 Paschim Vihar,
New Delhi 110 063

and

Sushil Raina

Microwave Tube Research and Development Center, DRDO, Bangalore 560 013

Received 12 July 2002; revised 17 January 2003; accepted 7 March 2003

A low noise amplifier employed in the microwave/mm-wave radiometers is used to amplify a signal to overcome the inherent drift in the synchronous detector to achieve a higher degree of stability. A low noise amplifier designed and fabricated is described. The amplifier has been designed for a gain of 60 dB with noise less than 10 mV peak-to-peak, having an output impedance of 100 Ω and an input impedance of 1.5 MΩ. The supply used for design consideration was 24 V DC.

Indian Journal of Radio & Space Physics

Vol. 32, June 2003, pp. 177-181

Study of antenna directivity

 Surendra Kumar Roy

Department of Physics, Government Polytechnic, Darbhanga 846 004

Received 7 November 2001; revised 11 September 2002; accepted 23 January 2003

Although more rigorous treatments have been developed for the antenna directivity, the directivity, including phase shift factors, for several types of uniformly excited planar arraysis obtained. The agreement between the theory and experimental result is found to be excellent.