ABSTRACTS
Indian Journal of Radio & Space Physics
VOLUME 31
NUMBER 1
FEBRUARY 2002
CONTENTS
Off-axis large time scale polarization of polar stars
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
D S V V D Prasad & P V S Rama Rao
Electric fields due to lateral corona current
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
Arun Kr Upadhayaya & Vir Singh
7
15
21
28
Spatio-temporal variations of convection and rainfall over Indian Ocean warm pool
N V Panchawagh & P Seetaramayya
34
Composition of rain water in Agra city, a semi-arid area in India
Richa Mudgal, Rajeev Upadhyay & Ajay Taneja
49
Finite element analysis of rectangular waveguide with inclined corners
Ajay Chaudhari & P B Patil
56
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.