Indian Journal of Radio & Space Physics

 

VOLUME 31

NUMBER 1

FEBRUARY 2002

 

CONTENTS

 

Off-axis large time scale polarization of polar stars

7

  Hussain Y Rashed Omari, Eqab M Rabei & Abdulaziz A Almulhem

 

 

 

Diurnal, seasonal and solar cycle variations of ionospheric electron content over an Indian low latitude station, Waltair

 

15

  D S V V D Prasad & P V S Rama Rao

 

 

 

Electric fields due to lateral corona current

21

  M P Singh, Jagdish Rai & J S Tomar

 

 

 

Correction to daytime mesospheric atomic oxygen density in MSIS-90 obtained from WINDII measurements of O(1S) dayglow emissions

 

28

  Arun Kr Upadhayaya & Vir Singh

 

 

 

Spatio-temporal variations of convection and rainfall over Indian Ocean warm pool

34

  N V Panchawagh & P Seetaramayya

 

 

 

Composition of rain water in Agra city, a semi-arid area in India

49

  Richa Mudgal, Rajeev Upadhyay & Ajay Taneja

 

 

 

Finite element analysis of rectangular waveguide with inclined corners

56

  Ajay Chaudhari & P B Patil

 

 

 

Papers accepted for publication

60

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 31, February 2002, pp. 7-14

 

 

Off-axis large time scale polarization of polar stars

 

Hussain Y Rashed Omari, Eqab M Rabei and Abdulaziz A Almulhem

The defining observational characteristics of AM Her polars are their intense polarization. One specifies their magnetic fields from the measured polarizations. Here, the relationship between polarization and the properties of the magnetic field for time-dependent oscillating shocks is investigated. The properties of the polarization on time scales large compared to the oscillation period are discussed.

 

Indian Journal of Radio & Space Physics

Vol. 31, February 2002, pp. 15-20

 

 

Diurnal, seasonal and solar cycle variations of ionospheric electron content over an Indian low latitude station, Waltair

D S V V D Prasad & P V S Rama Rao

The diurnal, seasonal and solar cycle variations of the ionospheric electron content (IEC) during both high (1979-80) and low (1984-85) sunspot activity periods at a low latitude station, Waltair (17.7° N, 83.3°E) have been studied. The diurnal variation shows noon bite-out and post-sunset enhancement in IEC during equinoctial and winter months of high sunspot activity period. The seasonal variation shows minimum IEC during each of the local hours of the day of low sunspot activity period compared to those in the corresponding hours of high sunspot activity period. The results on the diurnal variation of IEC, particularly, during the post-sunset hours of high sunspot activity period are discussed in relation to the effect of E ´ B drift at the equator.

 

Indian Journal of Radio & Space Physics

Vol. 31, February 2002, pp. 21-27

 

 

 

 

Electric fields due to lateral corona current

M P Singh, Jagdish Rai and  J S Tomar

 

In this paper calculations have been made for the electric fields due to lightning lateral corona currents. The electrostatic, induction and radiation fields have been found to be highly dependent on ground conductivity. It has been found that the cut-off distances for electrostatic and induction fields increase with the increasing conductivity of the soil. The ratio of horizontal to vertical field components becomes independent of time after a distance of above 5 km and is only a function of ground conductivity.

 

Indian Journal of Radio & Space Physics

Vol. 31, February 2002, pp. 28-33

 

Correction to daytime mesospheric atomic oxygen density in MSIS-90
obtained from WINDII measurements of O(1S) dayglow emissions

Arun Kr Upadhayaya & Vir Singh

The greenline dayglow emission measurements of Wind Imaging Interferometer (WINDII) between 92 and 100 km are analyzed by using the greenline emission model. It has been found that the model underestimates, quite significantly, greenline dayglow emissions rates between 92 and 100 km when the atomic oxygen density is used from the MSIS-90 model. In this altitude region the recombination of atomic oxygen via two steps mechanism as proposed by Barth is the main source of the production of greenline emission. Since the oxygen recombination basically scales with the square of the oxygen atom density, it is quite likely that the MSIS-90 model provides smaller values of atomic oxygen densities between 92 and 100 km. A simple global correction factor to atomic oxygen density is obtained by fitting the measured O(1S) emission rate using atomic oxygen density as a variable parameter in the model for a number of cases at different geographical locations and local times in both hemispheres. This factor can be incorporated in MSIS-90 model quite easily to obtain more precise values of atomic oxygen density between 92 and 100 km

 

 

Indian Journal of Radio & Space Physics

Vol. 31, February 2002, pp. 34-48

 

Spatio-temporal variations of convection and rainfall over Indian
Ocean warm pool

 

N V Panchawagh & P Seetaramayya

An attempt has been made to examine the spatio-temporal variability of rainfall and cloud cover in relation to the sea surface temperature distribution over the Indian Ocean warm pool (IOWP : 10°N-15°S; 60°-100°E) based on the NOAA Polar Orbiting Satellite outgoing longwave radiation (OLR) and WMO/WCRP Global Precipitation Climatological Project (GPCP) precipitation data at 2.5°´2.5° latitude/longitude grid for the period 1979-1990 and 1986-1993, respectively. The above data were subjected to empirical orthogonal functions (EOFs) analysis and it was found that the first four modes (EOF 1-4) show strong variability in both the above parameters in the region. In general, the isopleths patterns of the EOF-1 for both the elements show more or less similar trend of fair flatness of positive maximum loading in relation to warm pool area and, generally, oriented in an east-west direction depending upon the orientation of the warm sea surface temperature isotherms. The other three modes (EOF 2-4) showed distribution slightly different from first mode (EOF-1). The isopleths of these later three modes showed an inclination from the isopleths of EOF-1 in the region, which implies that the processes which are operating during these modes differ from those of EOF-1

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 31, February 2002, pp. 49-55

 

 

Composition of rain water in Agra city, a semi-arid area in India

 

Richa Mudgal, Rajeev Upadhyay & Ajay Taneja

Rainwater samples were collected at St. John’s crossing during the monsoon period of 2000. The cations (Ca2+, Mg2+, Na+, K+ and NH4+) and anions (F-, Cl-, HCO3-, NO3- and SO42-) along with pH were measured. The percentage contribution of soil components (Ca2+, Mg2+, Na+ and K+) and NH4+ are observed to be higher than the acidic substances. The ratio of F-/Ca2+, Mg2+/Ca2+, Na+/Ca2+ and NO3-/Ca2+ in rainwater samples indicates that local soil plays a significant role in precipitation chemistry. Hence, soil dust is responsible for neutralization of wet deposition. The data were also subjected to factor analysis based on principal component analysis using the SPSS software. Factor analysis also indicates that the soil as well as dust emission is the major contributor to rainwater composition.

 

Indian Journal of Radio & Space Physics

Vol. 31, February 2002, pp. 56-59

 

Finite element analysis of rectangular waveguide
with inclined corners

Ajay Chaudhari & P B Patil

Rectangular waveguide with inclined corners is analyzed using finite element method (FEM). The effect of inclination of two, three and four corners on bandwidth and cut-off frequency for TE10 and TE20 modes is studied. The variations in bandwidth and cut-off frequency for TE10 and TE20 modes are also observed. The bandwidth and cut-off frequencies are found to be increased as compared to those of normal rectangular waveguide.