Indian Journal of Radio & Space Physics

(CODEN: IJRSAK        ISSN: 0367-8393)

VOLUME 38

NUMBER 2

APRIL 2009

 

                                                                               CONTENTS

 

Effect of temperature dependent rate coefficient of reaction N(A3) + O on proton heating efficiency in auroral region

 

71

        Vir Singh* & M V Sunil Krishna

 

 

Role of VLF power line harmonic radiation in precipitating energetic electrons at high latitude

74

        Ram Prakash*, D D Gupta & Manoj Kumar Singh

 

 

Raindrop size distribution profiling by laser distrometer and rain attenuation of centimeter radio waves

 

80

        M Saikia*, M Devi, A K Barbara & H K Sarmah

 

 

Surface ozone and its precursors at two sites in the northeast coast of India

86

        N N Purkait, S De, S Sen & D K Chakrabarty*

 

 

Particle associated polycyclic aromatic hydrocarbons in urban air of Agra

98

        Nirat Rajput & Anita Lakhani*

 

 

Space disturbance effect on equatorial sporadic-E during sunrise

105

R G Rastogi & H Chandra*

 

 

Dielectric properties of black soil with organic and inorganic matters at microwave frequency

112

V V Navarkhele*, A A Shaikh & R S Ramshetti

 

 

Gunn loaded microstrip antenna with parasitic elements

116

J A Ansari*, Satya Kesh Dubey, Prabhakar Singh, Babau R Vishvakarma & R U Khan

 

 

*Authors for correspondence

 

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 38, April 2009, pp. 71-73

 

 

Effect of temperature dependent rate coefficient of reaction N2(A3) + O on proton heating efficiency in auroral region

Vir Singh†,* & M V Sunil Krishna

Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247 667, Uttrakhand, India

†Email: virphfph@iitr.ernet.in

Received 9 June 2008; accepted 24 October 2008

The proton heating efficiency in polar thermosphere is revisited in the light of new findings of the temperature dependence of rate coefficient of the reaction N2(A3) + O. This reaction is considered as one of the most significant source of proton heating in auroral region. The present results show that the heating rate due to this reaction above 110 km is 1.4 to 2.3 times higher than the earlier results. The proton heating efficiency is found eight to ten percent higher than the earlier results in the peak energy deposition region (110-130 km). These results would be very useful in the study of heat budget in the polar thermosphere particularly during solar proton events.

Keywords: Proton heating efficiency, Auroral region, Rate coefficient, Heat budget, Polar thermosphere

          PACS No.: 92.60.hb

 

 

Indian Journal of Radio & Space Physics

Vol. 38, April 2009, pp. 74-79

 

 

Role of VLF power line harmonic radiation in precipitating energetic electrons at high latitude

Ram Prakash*, D D Gupta & Manoj Kumar Singh

Department of Physics, Bipin Bihari (PG) College, Jhansi 284 001, UP, India

Received 29 January 2008; revised received 6 October 2008; accepted 11 November 2008

A study is carried out on energetic electron precipitation at high latitude (L = 4.3) by VLF power line harmonic radiation. The life-time of energetic electrons interacting with coherent VLF line radiation has been found to be 5.56 days only. This indicates a significant precipitation of energetic electrons (energy ~ a few keV) at high latitudes (L=4.3). The average flux of precipitating electrons by VLF line radiation has been estimated to be 3.47x10-3 ergs cm-2 s-1 which is almost the same as caused due to coherent whistler-mode waves of 1 pT intensity at 5 kHz and is found to be consistent with energy flux deposited in the lower ionosphere at L ~ 2.4 caused by lightning induced precipitation [Inan et al., J Geophys Res (USA), 92 (1987) 3293].

   Keywords: Energetic electron, VLF power line harmonic radiation, Electron precipitation

           PACS No.: 94.20.Qq

 

 

Indian Journal of Radio & Space Physics

Vol. 38, April 2009, pp. 80-85

 

 

Raindrop size distribution profiling by laser distrometer and rain attenuation of centimeter radio waves

M Saikia$,*, M Devi, A K Barbara & H K Sarmah

Department of Physics, Gauhati University, Guwahati, Assam 781014

$E-mail: manojksaikia@gmail.com

Received 10 August 2007; revised 21 September 2008; accepted 10 December 2008

The paper describes system design of laser distrometer, its calibration process and profiling of raindrop size distribution (RSD). Here, raindrop signature is extracted by allowing the drops to pass through a controlled field of view of a sensor. A laser beam works as signal source, phototransistor as detector-cum-amplifier and optical fibers as trans-receiving ports. RSD profiles and rain rate at different weather conditions have been presented. Specific raindrop attenuation of line of sight radio signals at 10 - 30 GHz of various drop diameters is then calculated by using standard attenuation equations and model values of scattering functions. Finally, the rain attenuation magnitudes are compared with those given by a model framed earlier [Timothy K I, Sharma S, Devi M & Barbara A K, Model for estimating rain attenuation in frequencies range 5-30 GHz, Electron Lett (UK), 31 (17) (1995)].

Keywords: Raindrop size distribution (RSD), Rain attenuation, Rain rate, Centimeter radio wave

          PACS No.: 92.40.eg

 

 

Indian Journal of Radio & Space Physics

Vol. 38, April 2009, pp. 86-97

 

 

Surface ozone and its precursors at two sites in the northeast coast of India

N N Purkait1, S De1, S Sen1 & D K Chakrabarty2,*,$

1S K Mitra Center, Institute of Radio Physics & Electronics, University of Calcutta, Kolkata 700 009, India

2Centre for Environment Survey, Ahmedabad 380 015, India

$E-mail: dkchakrabarty@rediffmail.com

Received 17 March 2008; revised 14 August 2008; accepted 22 August 2008

Diurnal and seasonal behavior of surface ozone (O3) at Kolkata (22.36°N, 88.24°E) and Haldia (22.05°N, 88.03°E), two tropical urban sites situated on the northeast coast of India, has been studied. The main sources of pollution at these two sites are a large number of small industries, oil refineries and thermal power plant in addition to heavy vehicular traffic. Along with O3, the behavior of its precursors, viz. CO, NOx (oxides of nitrogen) and non-methane hydrocarbons (NMHCs) have also been studied. Diurnal and seasonal behavior of these species has been found to be different at different times of the year. During monsoon months, O3 and its precursors do not show any diurnal variation. Distinct diurnal variation of O3 is found only during October - March with maximum value around 1500 hrs LT. The minimum value of ozone is found around midnight. For CO and NOx, distinct diurnal variations are found during October – February for Kolkata only, with minimum value around 1500 hrs LT and maximum value around midnight. The diurnal variation of these two species appears to be nearly identical. At Haldia, CO has a weak diurnal variation during November - February with maximum value at midnight and minimum value around 1500 hrs LT. At Haldia, for NOx no diurnal variation is observed. NMHC does not show any distinct diurnal variation at any site but its value is highest during winter. Using a simplified 1D steady state photochemical scheme, an attempt has been made to reproduce the daytime winter ozone values for both the sites. While O3 values at Kolkata could be reproduced to some extent, those at Haldia are very much underestimated. The effect of wind appears to be insignificant.

Keywords: Surface ozone, Diurnal variation, Non-methane hydrocarbons, Air pollutants

          PACS No.: 92.60.Sz

 

 

Indian Journal of Radio & Space Physics

Vol. 38, April 2009, pp. 98-104

 

 

Particle associated polycyclic aromatic hydrocarbons in urban air of Agra

Nirat Rajput & Anita Lakhani*,$

Department of Chemistry, Dayalbagh Educational Institute, Agra 282 110

$E-mail: anitasaran2003@yahoo.co.in

Received 25 September 2007; revised 25 November 2008; accepted 1 December 2008

Total suspended particulate matter (TSPM) samples were collected at Nunhai, Agra from May 2006 to September 2006. Since polycyclic aromatic hydrocarbons (PAHs) are known carcinogenic and mutagenic, concentrations of 16 PAHs in aerosols were quantified in the present paper. The dominating PAHs in TSPM include high molecular weight Benzo(ghi)Perylene, dibenzo(b)anthracene, indeno(123cd) pyrene, benzo(a)pyrene. Naphthalene and acenapthylene being more volatile were not detected in any of the samples. The sum of 14 PAHs ranged 150 - 480 ng m-3 with a mean value of 269 ± 121 ng m-3. The results indicate that PAH concentrations are higher than other industrial sites but are comparable to those measured in several urban Chinese cities, however, less than the industrial locations of China. Higher PAH concentrations are attributed to higher rates of emissions as well as greater scavenging and adsorption of vapor phase PAH on available TSPM. The potential sources of PAHs in aerosols were identified using the diagnostic ratios between PAHs. The vehicular emissions were the main contributors of particulate-associated PAHs and stationary combustion sources also contribute to the particulate PAHs. PAHs in aerosols were predominantly from gasoline and diesel engines.

  Keywords: Polycyclic aromatic hydrocarbons (PAHs), Toxic compounds, Aerosols, Particulate matter

          PACS No.: 92.60.Mt, 92.60.Sz

 

 

Indian Journal of Radio & Space Physics

Vol. 38, April 2009, pp. 105-111

 

 

Space disturbance effect on equatorial sporadic-E during sunrise

R G Rastogi & H Chandra*

Physical Research Laboratory, Ahmedabad 380 009, India

Received 25 September 2007; revised 29 February 2008; accepted 6 October 2008

The space weather event of 25 September 1998 and its effect in the E-region near magnetic equator has been studied. The geomagnetic H field variations recorded at low latitudes was normal on 24 and 26 September 1998 but there was a geomagnetic storm on 25 September with sudden commencement at 0445 hrs LT (75o EMT). There was a strong counter electrojet after sunrise associated with the magnetic storm. Solar wind speed and ion density and the interplanetary magnetic field (IMF) data show the IMF BZ turning towards south in the morning on 25 September 1998 and solar wind velocity was 850 kms-1. Quarter hourly ionograms at Thumba, located close to the dip equator were examined during morning hours on 24-26 September 1998. On 24 and 26 September 1998, E-region irregularities (Es-q) were first generated about an hour after the appearance of fresh E-region ionization following sunrise and by the time DH at Trivandrum started increasing above the corresponding value at Alibag. On the disturbed day, 25 September 1998, Es-q appeared later due to occurrence of counter electrojet after sunrise. This is caused by electric field changes associated with the magnetic storm rather than the late reversal of the electric field in the morning.

           Keywords: Equatorial electrojet, Equatorial sporadic-E, Magnetic disturbance

           PACS No.: 94.20.dg; 94.20.dt; 96.60.Vg

 

 

Indian Journal of Radio & Space Physics

Vol. 38, April 2009, pp. 112-115

 

 

Dielectric properties of black soil with organic and inorganic matters at microwave frequency

V V Navar khele1,$,*, A A Shaikh1 & R S Ramshetti2

1Dept. of Physics, Dr.Babasaheb Ambedkar Marathwada University, Aurangabad 431 004, India.

2Adarsh Mahavidyalaya, Omerga

$Email: vvn_bamu@yahoo.co.in

Received 11 May 2007; accepted 5 December 2008

The dielectric properties of black soil have been studied with addition of organic (vermi compost) and inorganic (calcium carbonate) matter. Microwave transmission line waveguide technique has been used for this purpose. The dielectric properties [dielectric permittivity (e¢) and dielectric loss (e¢¢)] have been measured for four different frequencies at room temperature. The experimental observations show that e¢ and e¢¢ decrease with increasing frequency of oscillation, and increases with increasing percentage volume of organic and inorganic matter. The results show that dielectric values obtained with organic matter are higher than that of inorganic matter.

Keywords: Black soil, Dielectric properties, Transmission line waveguide method

          PACS No.: 77.22.Gm, 92.40.Lg

 

 

Indian Journal of Radio & Space Physics

Vol. 38, April 2009, pp. 116-121

 

 

Gunn loaded microstrip antenna with parasitic elements

 

J A Ansari1,#,*, Satya Kesh Dubey1, Prabhakar Singh1, Babau R Vishvakarma2,$ & R U Khan2

1Department of Electronics and Communication, University of Allahabad, Allahabad

2Department of Electronics Engineering, I. T. BHU, Varanasi 221 005

E-mail: #jaansari@rediffmail.com; $brvish@bhu.ac.in

Received 19 July 2007; revised 22 September 2008; accepted 1 December 2008

An analysis of Gunn loaded patch with parasitic elements at radiating edges of the patch has been carried out using equivalent circuit concept for different values of bias voltage and threshold voltage. It is observed that addition of parasitic elements improves the band of operation to 400 MHz (bandwidth 4.48%, center frequency 8.95 GHz) as compared to 297 MHz (bandwidth 3.06%, center frequency 8.90 GHz) for Gunn loaded patch. Antenna also shows tunability of 50 MHz for bias voltage from 8 to 15 V for a given threshold voltage of 4.4 V and exhibits enhanced radiation by 0.5833 dB as compared to patch alone. Various parameters of the antenna are compared with simulated data using IE3D.

   Keywords: Microstrip antenna, Gunn diode integrated microstrip antenna, Active antenna,   Parasitic elements

PACS No.: 84.40.Ba