Indian Journal of Radio & Space Physics

CODEN: IJRSAK ISSN: 0367-8393 (print); 0975-105X (online)

http://www.niscair.res.in; http://nopr.niscair.res.in

 

VOLUME 38

NUMBER 5

OCTOBER 2009

 

CONTENTS

 

Variations of geomagnetic Dst, auroral indices and cosmic ray intensity during 28-31 Oct 2003 Halloween events

245

R P Kane

 

 

Relative effectiveness of plasmaspheric hiss and VLF hiss in the inner belt energetic electron precipitation

254

Ram Prakash*, Manoj Kumar Singh & D D Gupta

 

 

Some studies of solar flare effects on the propagation of sferics and a transmitted signal

260

B K De, S S De*, B Bandyopadhyay, Suman Paul, S Barui & D K Haldar

 

 

Ionospheric time delay variations in the equatorial anomaly region during low solar activity using GPS

266

Soumi Bhattacharya*, P K Purohit & A K Gwal

 

 

Reduction of number of parameters and forecasting convective developments at Kolkata (22.53N, 88.33E), India during pre-monsoon season: An application of multivariate techniques

275

Subhra Chatterjee, S Ghosh & U K De*

 

 

ANN technique for the evaluation of soil moisture over bare and vegetated fields from microwave radiometer data

283

G Dharanibai & Z C Alex*

 

 

Development of microstrip array antenna for wide band and multi band applications

289

S L Mallikarjun, R G Madhuri, S A Malipatil & P M Hadalgi*

 

 

*Authors for correspondence

 

 

 


Indian Journal of Radio & Space Physics

Vol. 38, October 2009, pp. 245-253

 

Variations of geomagnetic Dst, auroral indices and cosmic ray intensity during
28-31 Oct 2003 Halloween events

R P Kane

Instituto Nacional de Pesquisas Espacias INPE, Caixa Postal 515, 12201-970 - So Jos dos Campos, SP, Brazil

E-mail: kane@dge.inpe.br

Received 11 May 2009; revised 3 September 2009; accepted 7 September 2009

During 28-31 Oct 2003, there was intense interplanetary storm activity (Halloween events). A major storm started at about 0400-0600 hrs UT on 29 Oct 2003, reflected in extreme values of interplanetary parameters and geomagnetic index Dst. While few hours preceding 0400 hrs UT, it was essentially quiet but the auroral indices AL, AU, AE were not quiet and showed moderate increases. Thus, at least for this gigantic super fast storm (velocity of the solar wind disturbance exceeding 2000 kms-1), auroral indices seemed to be precursors with an antecedence of a few hours. This needs to be checked for very strong storms in future, probably after 2010, when cycle 24 sunspot activity will be in full swing.

Keywords: Geomagnetic index variations, Interplanetary storm, Halloween event, Auroral indices, Geomagnetic storm, Cosmic ray intensity

PACS Nos: 91.25.Rt; 96.50.sh; 94.30.Lr

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 38, October 2009, pp. 254-259

 

Relative effectiveness of plasmaspheric hiss and VLF hiss in the inner belt energetic electron precipitation

Ram Prakash*, Manoj Kumar Singh & D D Gupta

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

Received 11 May 2009; revised received and accepted 26 August 2009

Relative effectiveness of plasmaspheric hiss and VLF hiss in the inner belt energetic electron precipitation has been studied. The results show that plasmaspheric hiss can induce significant precipitation of electrons by causing small changes in their energy whereas in case of VLF hiss, nearly ten times higher energy changes are required for similar precipitation. The minimum pitch angle am corresponding to peak energy change varies with L-value in the same fashion as the minimum wave length (lm) corresponding to peak energy emission varies with temperature T in case of black body radiation. The results, further, hint that the plasmaspheric hiss is more effective in energetic electron precipitation towards the inner edge (L ~ 1.2) of inner radiation belt, which is in good agreement with the findings of earlier studies.

Keywords: Plasmaspheric hiss, VLF hiss, Energetic electron precipitation

PACS Nos.: 94.30.cv; 94.30.Ny

 

 

 


 

Indian Journal of Radio & Space Physics

Vol. 38, October 2009, pp. 260-265

 

Some studies of solar flare effects on the propagation of sferics and
a transmitted signal

B K De1, S S De2,*, B Bandyopadhyay2, Suman Paul2, S Barui2 & D K Haldar2

1Department of Physics, Tripura University, Tripura (West), Suryamaninagar 799 130, India

2Centre of Advanced Study in Radio Physics and Electronics, University of Calcutta, Kolkata 700 009, India

*Email: de_syam_sundar@yahoo.co.in

Received 19 May 2009; revised received and accepted 15 September 2009

Apart from diurnal and seasonal variations, integrated field intensity of sferics (IFIS) exhibits characteristic variations in relation to various geophysical and solar events like geomagnetic storms, meteor showers, solar X-ray flares and solar radio emission. Continuous monitoring of IFIS at frequencies 1, 3, 6, 9 and 12 kHz from Agartala (latitude 23N) are being made over the last several years. The analyses of some preliminary observations in relation to solar flares are reported in the paper. Solar flare effects on the propagation of transmitted signals at 16.3 kHz recorded in Kolkata (latitude 22.56N) during November 2004 have also been presented.

Keywords: Ionosphere, Geomagnetic storms, Solar flare, Sunspots, Sferics

PACS Nos.: 94.20.wg; 94.20.Vv; 96.60.qe

 

 

 

Indian Journal of Radio & Space Physics

Vol. 38, Octobrt 2009, pp. 266-274

 

Ionospheric time delay variations in the equatorial anomaly region during low solar activity using GPS

Soumi Bhattacharya1,$,*, P K Purohit2 & A K Gwal1

1Space Science Laboratory, Department of Physics, Barkatullah University, Bhopal 462 026, India

2National Institute of Technical Teachers Training and Research, Shamla Hill, Bhopal 462 026, India

$E-mail: sbhattacharya_82@yahoo.co.in

Received 17 June 2008; revised 9 March 2009; re-revised received and accepted 3 July 2009

Ionosphere can be a greatest variable source of error in precise time transfer using GPS satellites. The proposed navigation concept requires that a user measures the time-delay that satellite emitted signals experience in traversing the distance between satellite and user. The difference between the apparent range and the true range, or the free space velocity and the true velocity, is the quantity of interest. This quantity is directly proportional to the total electron content along the path of propagating signal. Thus, if the total electron content is known or is measured, a perfect correction to ranging could be performed. The equatorial anomaly region, Bhopal (geographic latitude. 23.2N, longitude 77.6E), India with dual frequency from the GSV4004A GPS Ionospheric Scintillation and TEC Monitor (GISTM) receiver have demonstrated a high degree of accuracy in measuring the ionospheric group delay. The diurnal and seasonal variations of ionospheric time delay have been studied during the solar minimum period January to December 2005. It was found that diurnal variation of ionospheric time delay is maximum in the month of April and minimum in the month of December. The study reveals that during low solar activity, equinox season shows the maximum delay while summer gives the moderate and winter shows the minimum delay. The ionospheric time delay was also studied during magnetic storm conditions for the same period and the occurrence of daily maximum ionospheric time delay as a function of day during this period.

Keywords: Time delay variation, Equatorial anomaly region, Scintillation, Total electron content, Ionospheric time delay

PACS Nos: 94.20.dt; 92.70.Qr

Indian Journal of Radio & Space Physics

Vol. 38, October 2009, pp. 275-282

 

Reduction of number of parameters and forecasting convective developments at Kolkata (22.53N, 88.33E), India during pre-monsoon season: An application of multivariate techniques

Subhra Chatterjee1, S Ghosh2 & U K De1,$,*

1Atmospheric Science Research Group, School of Environmental Studies, Jadavpur University, Kolkata 700 032, India

2Department of Mathematics, Barrackpore Rastraguru Surendranath College, Kolkata 700 120, India

$E-mail: deutpal2003@yahoo.com

The present work aims at the formation of a statistical index using the most effective parameters out of primarily selected 20 parameters to predict the convective development at Kolkata (22.53N, 88.33E), India during the pre-monsoon season along with a multivariate statistical analysis of 20 different thermodynamic and dynamic parameters. In the first phase, linear discriminant functions formed with the help of linear discriminant analysis (LDA) of 20 parameters derived from the radiosonde observations at 0000 and 1200 hrs GMT during 1985-1996 at Kolkata produced 42.8 and 72.7% correct prediction for fair weather and convective development in next 12 hrs for the years 1997 to 1999 whereas in the evening the respective correct results are 50.8 and 56.6%. In the second phase, an attempt has been made to reduce the number of parameters using eigenvector analysis and correlation study between 20 original parameters and significant principal components. Here, again LDA has been performed with the parameters thus selected. The study reveals that for morning and afternoon, the number of parameters can be reduced to 6 and 7, respectively. The accuracy of predictions is also found to improve as compared to the first phase. However, it may be mentioned that total number of days involved in the present study is much less than the total number of days in the entire pre-monsoon season from 1985 to 1999 due to the unavailability of basic data needed to compute the required parameters.

Keywords: Linear discriminant analysis (LDA), Principal component analysis (PCA), Convective development (CD), Fair weather (FW)

PACS Nos.: 92.60.Ox; 92.60.Qx; 92.60.Wc

 

 

 

Indian Journal of Radio & Space Physics

Vol. 38, October 2009, pp. 283-288

 

ANN technique for the evaluation of soil moisture over bare and vegetated fields from microwave radiometer data

G Dharanibai & Z C Alex$,*

School of Electrical Sciences, VIT University, Vellore 632 014, India

$Email: zachariahcalex@vit.ac.in

Received 21 May 2008; revised 20 February 2009; re-revised received and accepted 29 May 2009

Retrieving information from remotely sensed data is an important task. In the present work, data of L band microwave radiometer has been used to collect the brightness temperature over bare and vegetated fields in two polarizations at different moisture levels. Artificial neural network (ANN) trained with Levenberg-Marquardt algorithm has been used to determine soil moisture from brightness temperatures measured by microwave radiometry. ANN are trained to evaluate the moisture content in the range 0 - 36% from different sets of data of bare and vegetated fields. Properly trained feed-forward neural network with Levenberg-Marquardt algorithm predicted soil moisture content with less mean absolute error.

Keywords: Remote sensing, L-band microwave radiometry, Dielectric permittivity, Artificial neural network, Multi layer perceptron, Feed-forward neural network, Soil moisture

PACS Nos: 92.40.Lg; 84.40.-x

 

 

 

Indian Journal of Radio & Space Physics

Vol. 38, October 2009, pp. 289-294

 

Development of microstrip array antenna for wide band and multiband applications

S L Mallikarjun$, R G Madhuri, S A Malipatil & P M Hadalgi#,*

Department of PG Studies and Research in Applied Electronics, Gulbarga University, Gulbarga 585 106, Karnataka, India

E-mail: $mslakshetty@rediffmail.com, #pm_hadalgi@rediffmail.com

Received 23 February 2009; revised 15 June 2009; re-revised 3 August; accepted 17 August 2009

The paper presents the design and development of an X-band linearly polarized microstrip array antenna. The array elements are fed by corporate feed network, which improves the impedance bandwidth of the two element rectangular microstrip array antenna (2RMSAA) by 15.38%. By increasing the array elements from two to four and eight, multiband operation can be achieved with improved impedance bandwidth. These multiband array antennas may provide an alternative to large bandwidth planar antennas in applications where large bandwidth is needed for operating at two separate transmit-receiver frequencies. When the two operating frequencies are far apart, a multiband antenna can be used to avoid the use of separate antennas. Experimental results for the array antennas in term of return loss, radiation pattern, -3dB beam width, and gain are presented.

Keywords: Microstrip array antenna, Corporate feed network, Rectangular array antenna

PACS No.: 84.40.Ba