Indian Journal of Radio & Space Physics

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(CODEN : IJRSAK ISSN : 0367-8393)

VOLUME 37

NUMBER 5

OCTOBER 2008

 

CONTENTS

 

Limitations of the utility of CMEs for forecasting timings and magnitudes of geomagnetic Dst storms

303

R. P. Kane*

 

 

Solar cycle dependence of low amplitude anisotropic wave train events

312

Rajesh K. Mishra* & Rekha Agarwal Mishra

 

 

Effect of solar activity on ionospheric temperatures in F2 region

319

D K Sharma*, P K Sharma, Jagdish Rai & S C Garg

 

 

Effect of long term ozone trend on night airglow intensity of Li 6708 at Dumdum (22.5oN, 88.5oE) and Halley Bay (76oS, 27oW)

326

P K Jana*, D Sarkar & P Das

 

 

Vertical distribution of optical parameters of aerosols using Portable Automatic Lidar system of Gauhati University

333

M Devi *, A K Barbara, M Saikia & W Chen

 

 

Estimation of rain parameters from spectral moments of L-band wind profiler using Multi-Layer Perceptron Network model

341

Mahen Konwar, Diganta Kumar Sarma, Sanjay Sharma*, U. K. De, S. Pal & Jyotirmoy Das

 

 

Lower atmospheric water vapour measurement at coastal Trivandrum (8.33N, 77E) using a high resolution Raman lidar

353

S R Radhakrishnan, M Satyanarayana*, V P Mahadevan Pillai, B Presennakumar, D Ramakrishna Rao & V S Murthy

 

 

Thermal diffusivity of soils in iso-hyperthermic temperature regime by harmonic analysis

360

Chacko P Tessy * & G Renuka

 

 

Compact broadband stacked dual wide slit loaded rectangular microstrip antenna

366

Usha Kiran K, Ravi M Yadahalli, R M Vani & P V Hunagund*

 

 

__________

 

*Authors for correspondence

 

 


 

 

Indian Journal of Radio & Space Physics

Vol. 37, October 2008, pp. 303-311

 

Limitations of the utility of CMEs for forecasting timings and magnitudes of geomagnetic Dst storms

R P Kane

Instituto Nacional de Pesquisas Espaciais INPE, C.P. 515, 12245-970 So Jos dos Campos, SP, Brazil

kane@dge.inpe.br

Received 11 June 2007; revised 14 May 2008; accepted 14 August 2008

Results of the examination of data for about 100 events in solar cycle 23 (1996 onwards), when CMEs (Coronal Mass Ejections) and IP (Interplanetary) shocks could be matched, are presented. The CMEs had a large range of speed (200-4000 km/s), but the slow CMEs seemed to be accelerated and the fast ones decelerated during the transit from Sun to Earth. Hence, IP shock speed near the Earth was in a narrower range (350-2000 km/s). A regression equation can be established between the CME lateral expansion speed and the corresponding IP shock speed. But observed values have a considerable scatter and can have extreme deviations of ~ 35% from the predicted values. Similarly, the transit times from Sun to Earth can have extreme deviations of ~ 35% from the predicted values. The transit times can be as low as 25 h (extreme uncertainty ~ 5 h) to as high as 100 h (extreme uncertainty ~35 h) and have no one-to-one relationship with the magnitudes of the Dst storms that follow, or with the time intervals between the IP shock and the following maxima of negative Bz or negative Dst. The time intervals between maximum negative Bz and maximum negative Dst are mostly in the range of 0-5 h. The magnitudes of the maxima of negative Bz and the following negative Dst are highly correlated, indicating this as a major, overpowering relationship for determining the severeness of geomagnetic storms.

Keywords: Flares and mass ejections, Coronal mass ejections, Solar-planetary relationships, Geomagnetic storms

PACS No.: 96.60.ph; 96.60.qe

 

Indian Journal of Radio & Space Physics

Vol. 37, October 2008, pp. 312-318

 

Solar cycle dependence of low amplitude anisotropic wave train events

 

Rajesh K Mishra*1,a & Rekha Agarwal Mishra2,b

1Computer and IT Section, Tropical Forest Research Institute, P.O. RFRC, Mandla Road, Jabalpur (MP) 482 021, India

aE-mail rkm_30@yahoo.com; rajeshkmishra20@hotmail.com

2Department of Physics, Govt. Model Science College (Autonomous), Jabalpur (MP) 482 001, India

bE-mail: rm_jbp@yahoo.co.in

Received 30 April 2007; revised 22 July 2008; accepted 14 August 2008

A large number of low amplitude anisotropic wave train events (LAEs) of cosmic ray diurnal anisotropy have been studied during 1980-1994 as a function of solar activity represented by sunspot numbers using the hourly neutron monitor data of Deep River station. The amplitude as well as direction of the diurnal anisotropy is well correlated with solar cycle during low amplitude days. The time of maximum for all days lies along 1650 hrs LT direction and is mostly caused by depression of cosmic ray intensity along garden hose direction or the increase of the intensity along anti-garden hose direction similar to that of high amplitude events. However, the direction of anisotropy for LAEs shows a preferential direction along ~1250 hrs LT direction and this may be attributed to the increase in diffusion of particles perpendicular to interplanetary magnetic field lines. The shift of time of maximum along ~1250 hrs LT direction for LAEs may be attributed to the increase in diffusion of particles perpendicular to interplanetary field lines. However, the shift of time of maximum for LAEs along 1550 hrs LT direction is mainly caused by corotation of cosmic ray particles along with solar system magnetic fields similar to that of normal diurnal variation. The occurrence of LAEs is solar activity dependent. It may be concluded that interplanetary turbulences responsible for cosmic ray modulation effects do not reach the Earth during solar minimum and maximum, which results in the dominance of LAEs during these periods. The increase in diurnal amplitude of LAEs during solar minimum and maximum is contributed by the additional flow of cosmic ray particles due to corotating streams.

Keywords Cosmic ray, Solar cycle, Sunspot, Anisotropy

PACS No. 96.60.qd; 94.20.wq; 92.05.Fg

 

Indian Journal of Radio Space Physics

Vol. 37, October 2008, pp. 319-325

 

Effect of solar activity on ionospheric temperatures in F2 region

D K Sharma1, P K Sharma1, Jagdish Rai2 & S C Garg3

1Department of Applied Sciences, Manav Rachna College of Engineering, Faridabad 121 001, Haryana, India

E-mail: dksphdes@rediffmail.com

2Department of Physics, Indian Institute of Technology, Roorkee 247 667, Uttaranchal, India

3Radio & Atmospheric Sciences Division, National Physical Laboratory, New Delhi 110 012, India

Received 29 May 2007; revised 21 July 2008; accepted 28 July 2008

Ionospheric F-region is very dynamic and highly depends on the solar cycle. In the present study almost half of the solar cycle from January 1995 to December 2000 (from solar minimum to solar maximum) satellite data were used. The data were recorded with the help of Retarding Potential Analyzer (RPA) payload aboard Indian SROSS-C2 satellite at an average altitude of 500 km over the Indian region. The data analysis shows that the nighttime average ionospheric electron and ion temperatures show a positive correlation with solar activity. However, the sunrise peak values show anti-correlation with solar activity. Further the ratio of sunrise average peak value and nighttime average show a negative correlation with the solar activity, both for electron and ion temperatures. A sudden enhancement at sunrise has been observed during all seasons, in both electron and ion temperatures. Comparison of the measured ionospheric electron and ion temperatures with the predicted values from the international reference ionosphere (IRI) reveals that the peak during sunrise hours is slightly underestimated by the IRI model.

Keywords: F2 region, Ionospheric, temperature, Solar activity, RPA payload

PACS No.: 94.20.dj; 94.20.wq

 

Indian Journal of Radio Space Physics

Vol. 37, October 2008, pp. 326-332

 

Effect of long-term ozone trend on night airglow intensity of Li 6708 at Dumdum (22.5N, 88.5E) and Halley Bay (76S, 27W)

P K Jana1, D Sarkar1 & P Das2

1Department of Chemistry, Government College of Education, Banipur, North 24-Parganas 743 233 (WB), India

2Directorate of Technical Education, Bikash Bhavan, Saltlake, Kolkata 700 091, (WB), India

Received 17 April 2007; revised 18 June 2008; accepted 4 July 2008

The paper presents the effect of O3 depletion on night airglow emission of Li 6708 line at Dumdum (22.5N, 88.5E), India and Halley Bay (76S, 27W), a British Antarctic Service Station. Calculations based on chemical kinetics show that the airglow intensity of Li 6708 line will also be affected due to the depletion of O3 concentration. The nature of yearly variation and seasonal variation of intensity of Li 6708 line for the above two stations are shown and compared. It is shown that the rate of decrease of intensity of Li 6708 line is comparatively more at Halley Bay due to dramatic decrease of Antarctic O3 concentration.

Keywords: Ozone depletion, Airglow emission, Halley Bay, Dumdum

PACS No: 94.10. Fa, 94.10. Rk

 

Indian Journal of Radio & Space Physics

Vol. 37, October 2008, pp. 333-340

 

Vertical distribution of optical parameters of aerosols using Portable
Automatic Lidar system of Gauhati University

 

M Devi *,1, a, A K Barbara1, M Saikia1 & W Chen 2

1Department of Physics, Gauhati University, Guwahati 781014, Assam

2Iinstitute of Optics and Fine Mechanics, Chinese Academy of Sciences, China

aE-mail: md555@sify.com

Received 11 April 2007; revised 17 October 2007; accepted 7 July 2008

The features of a Portable Automated Lidar (PAL), operated at Guwahati (26N and 92E) are presented in this paper. The system has been used to determine vertical distribution of optical parameters of aerosols. The paper also describes a method adopted for profiling of aerosol extinction coefficient along with calibration of the lidar system. The extinction coefficient values of aerosols for dust-free and dusty situations are also presented.

Keywords: Lidar, Aerosols, Extinction coefficient

PACS No.: 92.60.Mt

 

 

Indian Journal of Radio & Space Physics

Vol. 37, October 2008, pp. 341-352

 

Estimation of rain parameters from spectral moments of L-band wind profiler using Multi-Layer Perceptron Network model

Mahen Konwar1, Diganta Kumar Sarma1, Sanjay Sharma*, 1, U. K. De2, S. Pal3 & Jyotirmoy Das4

1Department of Physics, Kohima Science College, Jotsoma, Kohima, Nagaland 797 002, India

2Department of Environmental Science, Jadavpur University, Kolkata, India

3ECSU, Indian Statistical Institute, Kolkata 700 108, India

4Institute of Technology and Marine Engineering, Jhinga 743368, India

Received 19 February 2007; revised 3 September 2007; accepted 11 July 2008

Two Multi-Layer Perceptron (MLP) models are developed to estimate the radar reflectivity factor (dBZ) and rain intensity (R) from the spectral moments of an L-band wind profiler. Out of the four spectral moment inputs of the MLP models, the backscattered power (P) and Doppler velocity (VD) were found to have better correlation with the rain parameters. The model results were validated with the Joss Waldvogel Disdrometer (JWD) observations. For the training and validation data sets of dBZ, the root mean square error (rmse) of estimated and observed data sets were found to be 5.05 and 5.32 dBZ with correlation coefficients of 0.90 and 0.86, respectively. Similarly, for the training and validation data sets of R, the rmse for estimated and observed values were found to be 4.27 and 7.74 mmh-1 respectively with correlation coefficients of 0.95 and 0.78. The developed models were validated with a rain event on 22 June 2000, that consisted of rain from both convective and stratiform regimes. The error between the estimated and observed rain accumulation was found to be ~ 5%. The height profiles of estimated dBZ were able to identify the bright band during stratiform rain by virtue of high values of reflectivity gradient at around 4.0 km height. Though ambiguity in the estimation of R was observed at bright band level, overall estimated parameters were in good agreement with general characteristics of convective and stratiform rain.

Keywords: L-band wind profiler, Spectral moments, Joss Waldovogel Disdrometer, Radar reflectivity factor, Rain intensity, Multi-Layer Perceptron network

PACS No.: 92.40.Ea; 92.40.eg; 92.60.gf

 

Indian Journal of Radio & Space Physics

Vol. 37, October 2008, pp. 353-359

 

Lower atmospheric water vapour measurement at coastal Trivandrum
(8.33N, 77E) using a high resolution Raman lidar

S R Radhakrishnan1, M Satyanarayana1,2, V P Mahadevan Pillai1, B Presennakumar2, D Ramakrishna Rao2 & V S Murthy3

1Department of Optoelectronics, University of Kerala, Trivandrum 695 581, Kerala, India

2Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695 022, India

3Indian Institute of Technology-Madras, Chennai 600 036, India

E-mail: drsatyanarayana.malladi@gmail.com

Received 24 May 2007; revised 2 June 2008; accepted 5 June 2008

Near simultaneous measurement of atmospheric aerosol and water vapour is described in this paper, making use of the Nd: YAG laser based multiwavelength lidar system, designed and developed in-house at Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum, India. In the present study, the vibrational Raman scattered signals of N2 and H2O were used for the measurement of atmospheric water vapour and aerosol extinction. Nighttime water vapour profiles are obtained in the 1-6 km altitude regions in the lower troposphere. Necessary aerosol corrections to water vapour profiles are also done. Lidar derived water vapour profiles are compared with the profiles calculated from High resolution Regional Weather Model (HRM) available during the same period.

Keywords: Laser remote sensing, Vibrational Raman lidar, Differential atmospheric transmission, Atmospheric water vapour, Atmospheric aerosols, High Resolution Regional Weather Model, Extinction coefficient

PACS No. 42.62.Ca, 42.68.Ge, 92.60.Jq, 42.68.Jg, 42.68.Wt, 92.60.Bh, 92.20.Bx, 92.60.Hf, 92.60.Mt, 92.60.Nv, 92.70.Cp, 96.15.H


 

Indian Journal of Radio & Space Physics

Vol. 37, October 2008, pp. 360-365

 

Thermal diffusivity of soils in iso-hyperthermic temperature regime by harmonic analysis

 

Chacko P Tessy1 & G Renuka2

1Department of Physics, St Xaviers College, Thumba 695 586, India

e-Mail: gitajose@hotmail.com

2Department of Physics, University of Kerala, Kriavattom 695 581, India

 

Received 3 October 2006; revised 8 June 2007; accepted 9 May 2008

 

Soil temperatures at various depths at three stations in Kerala were subjected to harmonic analysis for a period of seven years. The amplitude of soil temperature wave at various depths decreases with higher order of harmonics. The thermal diffusivity of various soil layers for the first three harmonics have been calculated using amplitudes and phase angles of the soil temperature wave. The combined effect of first three harmonics gives more reliable values for thermal diffusivity in different soil layers.

Keywords: Soil temperature, Harmonic analysis, Thermal diffusivity

PACS No.: 92.40.Lg

 

 

Indian Journal of Radio & Space Physics

Vol. 37, October 2008, pp. 366-369

 

Compact broadband stacked dual wide slit loaded rectangular microstrip antenna

K Usha Kiran1, Ravi M Yadahalli1, R M Vani2 & P V Hunagund*,1,a

1Department of Applied Electronics, Gulbarga University, Gulbarga 585 106, Karnataka

2Department of USIC, Gulbarga University, Gulbarga 585 106, Karnataka

aEmail: prabhakar_hunagund@yahoo.co.in

Received 6 February 2007; revised 31 July 2007; accepted 27 June 2008

Compact broadband stacked dual wide slit loaded rectangular microstrip antenna is designed, fabricated and studied experimentally. The design consists of stacking (h = 3.2 mm) of two dual wide slit loaded rectangular microstrip patches of the same size. The parametric analysis was carried out by varying slit width and slit length of dual wide slits. This stacked dual wide slit loaded rectangular microstrip antenna gives a broad bandwidth of 27% and 24% reduction in antenna size. The obtained bandwidth also covers the frequency range of wireless local area network applications.

Key words: Compact broadband antenna, Dual wide slits, Stacked antenna

PACS No.: 84.40.Ba