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Indian Journal of Radio & Space Physics

 

 

 

 ISSN : 0367-8393

 

CODEN:IJRSAK  

VOLUME 32

NUMBER 6

DECEMBER 2003

 

CONTENTS

An improved data reduction technique for the retrieval of the Doppler parameters from interference fringes obtained by a high resolution Fabry-Perot spectrometer

329

Tarun Kumar Pant, R Suhasini, S Gurubaran & R Sridharan

 

Quasi-linear pitch angle diffusion and storm-time energetic electron precipitation from inner radiation belt

337

Ram Prakash, A P Singh, B M Agrawal & D D Gupta

 

Day-to-day variability of quiet-time ionospheric foF2

344

R P Kane

 

A critical review of turbulence models

349

A P Roychowdhury, Pradeep Kumar & R Balu

 

Monitoring  of boundary layer winds using a lower atmospheric wind profiler

360

K Krishna Reddy & Yuichi Ohno

 

Mixed layer height over Bay of Bengal during Indian summer monsoon using MONTBLEX observations

373

M N Patil & S S Parasnis

 

Equivalence between external electric field with temperature and supersaturation in nucleation process

379

N Singh & Anand Kumar

 

Beam shaping of V-slot waveguide antenna using corner reflector

382

B S Makal, R M Vani, P M Hadalgi, S N Mulgi & P V Hunagund

 

 
Notes
 

On the relationship between the magnetic field variations and meteor showers

385

V H Kulkarni & R P Kane

 

ANNUAL INDEX

387

 

 

Referees of the year

392

 

 

 

Indian Journal of Radio & Space Physics

Vol. 32, December 2003, pp. 329-336

 

An improved data reduction technique for the retrieval of the Doppler parameters from interference fringes obtained by a high resolution Fabry-Perot spectrometer

Tarun Kumar Pant1, R Suhasini 2, S Gurubaran3 & R Sridharan1

 

A new data analysis scheme for retrieving Doppler temperatures from high resolution Fabry-Perot spectrometer fringes is described. Important aspects of parametric representation of the instrument function, convolution and the various instrument-broadening functions are discussed in detail. Complete theoretical background highlighting the method for recovering Doppler parameters and involved errors using the instrument-broadened airglow emission profile are provided. Further, a criterion is set to select proper airglow line profiles for the analysis.

 

Keywords: Doppler parameter, Interference fringes, Fabry-Perot spectrometer, Airglow emission

 

 

 

Indian Journal of Radio & Space Physics

Vol. 32, December 2003, pp. 337-343

 
Quasi-linear pitch angle diffusion and storm-time energetic electron precipitation from inner radiation belt

Ram Prakash, A P Singh, B M Agrawal & D D Gupta

 

Pitch angle scattering and diffusion of inner belt electrons, interacting gyro-resonantly with wide-band whistler-mode ELF/VLF waves, are evaluated using quasi-linear theory in order to study the storm-time precipitation of energetic electrons from inner radiation belt. The calculated pitch angle scattering (being ~ 102-103 deg near the edge of loss cone) and life-times (hours and days only) indicate a significant electron precipitation into the lower atmosphere from the inner radiation zone. The results further hint that the calculated quasi-linear diffusion coefficients and pitch angle scattering both decrease with increasing equatorial pitch angle and approach a zero value at 90. This provides a plausible explanation of the fact that farther the pitch angles from the loss cone, less efficient will be the diffusion of electrons into the loss cone and that the electrons with large pitch angle near 90 are stably trapped in the inner zone.

 

Keywords: ELF/VLF hiss, Pitch angle diffusion, Scattering, Whistlers, Electron precipitation

 

 

 

Indian Journal of Radio & Space Physics

Vol. 32, December 2003, pp. 344-348

 

Day-to-day variability of quiet-time ionospheric fo F2

R P Kane

 

The period 14 May-7 June 1996 was geomagnetically very quiet, with daily sunspot number mostly zero and geomagnetic Kp index of ~2.0 or less. The day-to-day variations of foF2 near noon at several locations showed oscillations with peak spacings of ~7 days at several locations, indicating that in the absence of solar or geomagnetic effects, planetary waves dominate the day-to-day variability. The results are in rough agreement with earlier results of other workers.

Keywords: Geomagnetic activity, Sunspot, F-region

 

 

 

Indian Journal of Radio & Space Physics

Vol. 32, December 2003, pp. 349-359

 

A critical review of turbulence models

A P Roychowdhury, Pradeep Kumar & R Balu

 

A comparative study of turbulence modelling principles has been made and drawbacks are highlighted with a proposal for the use of large eddy simulations and k-ε turbulence models with compressibility corrections for the use in aerodynamic applications. Explicit algebraic models are able to capture curvature effects and are based on the rapid distortion theory and are recommended for high convective Mach number flow applications.

 

Keywords: Turbulence model, Aerodynamics, Mach number

 

 

 

Indian Journal of Radio & Space Physics

Vol. 32, December 2003, pp. 360-372

 

Monitoring of boundary layer winds using a lower
atmospheric wind profiler

 K Krishna Reddy and Yuichi Ohno

 

An L-band (1357.5 MHz) lower atmospheric wind profiler (LAWP) has been installed and successfully operated at Gadanki, India, since September 1997. First results of the accuracy can be given on the basis of about 24 days intercomparisons between LAWP and Indian MST radar data. The root mean square differences (r.m.s. deviation) have been found to range between 1.18 m/s and 1.6 m/s for the wind speed. The two wind profilers compliment each other quite well, considering both the availability and the reliability of the wind measurements. Statistics of the data availability are shown based on 342-days data both in low mode and high mode. The 80% availability of the LAWP was determined with wind measurements of 3.6 km in low mode and 5 km in high mode. It means that the Gadanki-LAWP is also capable of yielding quality data to support the study of severe weather. The presence of abundant amount of moisture in the lower and middle troposphere during summer monsoon enabled good measurements up to about 6 km height, a range much greater than the dry season. The results indicate that the LAWP could help improve the understanding of the atmospheric processes involved in severe weather (mesoscale convective systems, tropical cyclone and storms) in the tropical region.

 

Keywords: Wind profiler, MST radar, Tropospheric weather, Weather prediction

 

 

 

Indian Journal of Radio & Space Physics

Vol. 32, December 2003, pp. 373-378

 

Mixed layer height over Bay of Bengal during
Indian summer monsoon using MONTBLEX observations

M N Patil & S S Parasnis

 

The height of mixed layer and cloud base is studied in relation to surface meteorological parameters, surface fluxes of heat and momentum and synoptic weather disturbances. For this study, surface as well as upper air meteorological observations collected over north Bay of Bengal (20oN, 89oE) during the summer monsoon of 1990 as a part of Monsoon Trough Boundary Layer Experiment (MONTBLEX), were utilized. Empirical relation between the cloud base height and the surface meteorological observations has been verified for its validity over Bay of Bengal. This height is further compared with aerological observations. A simple relation based on surface air temperature, pressure and wind speed has been suggested to estimate the cloud base height. Influence of the turbulent surface fluxes of heat and momentum on evolution of mixed layer over Bay of Bengal has been brought out.

 

Keywords: MONTBLEX, Bay of Bengal, Virtual potential temperature, Mixed layer height, Cloud base height, Surface fluxes.

 

 

 

Indian Journal of Radio & Space Physics

Vol. 32, December 2003, pp. 379-381

 

Equivalence between external electric field with
temperature and supersaturation in nucleation process

N Singh & Anand Kumar

 

The equivalence between critical temperature corresponding to unit nucleation rate per unit volume has been studied with external electric field applied to water vapours. It has been found that an external electric field of 1 e.s.u. with different supersaturation ratio is equivalent to several orders of temperature. The high electric field is found to correspond with lower temperatures for critical nucleation. The theory of droplet growth in presence of external electric field has been applied to water vapour condensation. The radius of critical nucleus is found to depend on electric field and relaxation time. Further in presence of electric field, Gibbs free energy of formation of water molecule changes for a critical nucleus and is found to be much less than that in absence of the electric field, but equilibrium concentration of nuclei is very much larger.

 

Keywords: Nucleation process, Supersaturation, Electric field, Drop growth

 

 

 

Indian Journal of Radio & Space Physics

Vol. 32, December 2003, pp. 382-384

 

Beam shaping of V-slot waveguide antenna
using corner reflector

B S Makal, R M Vani, P M Hadalgi, S N Mulgi and  P V Hunagund

 

This paper presents the experimental investigations of the variation of on-axis power, half-power beam width and VSWR of V-slot waveguide antenna (V-SWGA) for different parameters of corner reflector (CR). Experimental study reveals that the CR has very predominant effect in improving the antenna parameters of V-SWGA.

 

Keywords: Beam, Waveguide, Antenna, Corner reflector

 

 

 

Indian Journal of Radio & Space Physics

Vol. 32, December 2003, pp. 385-386

 

On the relationship between the magnetic field
variations and meteor showers

V H Kulkarni  and R P Kane

 

The magnetic Z field variation for the period 9-25 Dec. 1996, recorded at the stations Sodankyla (67.37N, 26.63E), Tromso (69.67N, 18.95E), Abisko (68.30N, 18.82E), and Hornsund (77.00N, 26.63E) (http://swdcwww.kugi.kyoto-u.ac.jp) are compared with the Geminids (12-15 Dec. 1996) and Ursids (20-23 Dec. 1996) showers as reported by Yrjola (http://www.rmob.org). The correlation studies show that it is difficult to prove conclusively that the magnetic field fluctuations observed at Sodankyla are due to the dust particles in the meteor showers and the associated changes in the ionospheric currents due to them.

 

Keywords: Magnetic field, Meteor showers, Ionospheric current