Indian Journal of Radio & Space Physics

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ISSN : 0367-8393

VOLUME 34

 

NUMBER 3

CODEN:IJRSAK 

JUNE 2005

 

CONTENTS

 

Editorial: The changing ionosphere – Long term trends

151

        K K Mahajan*

 

 

Solar EUV flux during sunspot cycles 21, 22 and 23 – Correlation with proxy indices and real time prediction

153

        K K Mahajan* & A K Dwivedi

 

 

Hysteresis and non-linearity between solar EUV and 10.7 cm fluxes

161

        R P Kane*

 

 

Cosmic ray variations during density extremes in solar wind

171

        R P Kane*

 

 

Solar longitudinal distribution of solar flares in association with Forbush decreases

175

        Pankaj K Shrivastava* & Neelam Singh

 

 

Wide band single-fed parasitically excited microstrip patch antenna for GPS

179

        Ashwani kumar & A D Sarma*

 

 

TEC derived from incoherent scatter measurements during solar maximum and their comparison with IRI-2001 model

184

        N K Sethi* & V K Pandey

 

 

Theoretical Z-R relationship for precipitating systems using Mie scattering approach

191

        Usha N Rao, Abhijit Sarkar* & M Mohan

 

 

Potential and field distribution in a cylindrical tube filled with a dielectric material with a centre hole

197

        B N Das*, Arun Gayen & D R Poddar

 

 

FTFN based dual inputs current-mode allpass inverse filters

206

        N A Shah* & M A Malik

 

 

Corrigendum

210

 

 

 

 

__________

 

*Corresponding authors

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, June 2005, pp. 153-160

 

 

Solar EUV flux during sunspot cycles 21, 22 and 23—Correlation with proxy indices and real time prediction

 

K K Mahajan & A K Dwivedi

Radio & Atmosphere Science Division, National Physical Laboratory, New Delhi 110 012

Received 22 December 2004; accepted 4 March 2005

Langmuir probe on the Pioneer Venus Orbiter measured the total solar EUV flux during large portions of sunspot cycles 21 and 22, while CELIAS/Solar EUV Monitor (SEM) on the SOlar and Heliospheric Observatory (SOHO) measured this flux in the spectral ranges 26-34 nm and 0.1-50 nm during the whole of sunspot cycle 23. In this paper, daily values of these EUV fluxes are studied in relation to various often-used proxy indices to identify a single index which has the highest correlation coefficient with the observed values during all the three sunspot cycles. It is observed that no single index exhibits this feature. However, almost all the proxy indices averaged over one-half or more solar rotations show a high degree of correlation with the daily EUV flux. Further, the solar magnetic field is found to exhibit somewhat better correlation and it is recommended that this index averaged over three previous solar rotations may be used for real time prediction of solar EUV flux.

Keywords: Solar EUV flux, Solar indices, Sunspot cycles, Proxy indices

PACS No.: 96.60 Rd, 96.60.Tf; 96.60 Qc

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, June 2005, pp. 161-170

 

 

Hysteresis and non-linearity between solar EUV and 10.7 cm fluxes

 

R P Kane

Instituto Nacional de Pesquisas Espaciais, São José dos Campos, SP, Brazil

E-mail: kane@laser.inpe.br

Received 31 December 2003; revised 12 January 2005; accepted 11 April 2005

It has been reported in literature that for values of the solar 2800 MHz radio flux (10.7 cm, F10) exceeding 200, solar EUV values show saturation effects. This aspect was examined using EUV data obtained by the AE-E satellites during 1977-1981 and the SEM/SOHO satellite data from 1996 onwards up to date. It was noticed that the saturation effects were not always seen in sequences of days when F10 exceeded 200. In both of these data sets, near solar maximum, there were slight differences in the evolution of the EUV and F10. Either their peaks were slightly displaced and/or their evolution profiles were different, the F10 remaining steady for several months after peaking (flat peak), while the EUV started decreasing soon after peaking, indicating probable ‘hysteresis’ loops.

Key words: Solar EUV, Solar 10.7 cm flux

PACS No: 95.85.-e; 96.60 Rd; 96.50.Ek

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, June 2005, pp. 171-174

 

 

Cosmic ray variations during density extremes in solar wind

                                                                                                         

R P Kane

Instituto Nacional de Pesquisas Espaciais, São Jose dos Campos, São Paulo, Brazil

E-mail: Kane@dge.inpe.br

Received 24 March 2004; revised 24 June 2004; accepted 27 April 2005

A comparison of the variations of the cosmic ray neutron monitor intensities with variations of geomagnetic disturbance Dst and (number) densities N of interplanetary plasma observed near the Earth during June-August, 1979 and May 1999 (intervals when N was abnormally low) has been presented. It showed that cosmic ray variations were very loosely related to Dst variations (variations often out-of-phase by several days, and magnitudes not proportional) and had no relationship with plasma densities N (low or high).

Keywords: Cosmic ray intensity, Solar wind, Geomagnetic indices, Interplanetary plasma density

PACS No.: 96.60.Vg; 96.40-z

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, June 2005, pp. 175-178

 

 

Solar longitudinal distribution of solar flares in association

with Forbush decreases

 

Pankaj K Shrivastava & Neelam Singh

Department of Physics, Government Model Science College, Rewa (M.P) 486 001

E-mail: pankaj_in_2001@rediffmail.com

Received 24 March 2004; revised 28 December 2004; accepted 12 April 2005

Solar flares are complex transient excitation of the solar atmosphere above magnetically active region of the solar surface. In the present study major solar flare events have been utilized to study their longitudinal frequency distribution in eastern and western hemisphere of the sun. A statistical study has been done to derive their association with Sudden Storm Commencements (SSCs) and Forbush decreases (Fds) for the period of solar cycle 22 (1986 to February, 1996) and recent period of solar cycle 23 (March, 1996 to August, 2003). It has been noted that large number of solar flares in the solar western hemisphere are found to be associated with Forbush decreases. It is found for solar cycle 22 that the number of solar flares (Fd associated) that occurred in western hemisphere is larger as compared to that in eastern hemisphere. Number of SSC associated solar flares are also found to be larger in the solar western hemisphere.

Key words: Solar flares, Forbush decreases, Solar cycle

PACS No.: 96.60 Rd

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, June 2005, pp. 179-183

 

 

 

Wide band single-fed parasitically excited microstrip patch antenna for GPS

 

Ashwani Kumar1 & A D Sarma2

1Defence Electronics Research Laboratory, Candrayangutta, P.O. Kesavgiri, Hyderabad 500 005 (A P), India

2R & T Unit For Navigational Electronics, Osmania University, Hyderabad 500 007 (AP), India

Email: ad_sarma@yahoo.com

Received 12 April 2004; revised 8 July 2004; accepted 19 April 2005

As a part of the modernization of GPS system, a second civil signal at L2 (1227.45 MHz) and a third new civil signal at L5 (1176.45 MHz) will be added to future GPS satellites in addition to existing civil signal at L1 (1575.42 MHz) frequency. A wide band, compact, low profile, parasitically excited microstrip antenna design is presented to cover L2 and L5 frequencies. The proposed antenna design has a perfect square patch, which is parasitically excited by a nearly square patch fed at single point. Good impedance matching and circularly polarized radiation patterns have been obtained over wide frequency band by using bandwidth-enhancing techniques. The gain of the antenna is found to be more than 5.5 dB.

Keywords: GPS, Wide band microstrip antenna, Parasitic excitation, Circular polarization

PACS No: 84.40 Ba

IPC Code: H 01 Q9/00; H 01 Q21/00; H 01 Q23/00

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, June 2005, pp. 184-190

 

 

TEC derived from incoherent scatter measurements during solar maximum and their comparison with IRI-2001 model

 

N K Sethi & V K Pandey

Radio and Atmospheric Sciences Division, National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012

Received 28 October 2004; revised 11 February 2005; accepted 4 March 2005

The diurnal and seasonal variations of the total electron content (TEC), derived from high resolution electron density profiles measured with the Arecibo (18.4°N, 66.7°W, dip 50°N) incoherent scatter radar, are examined during high sunspot activity period (1989-90). Median values of TEC are then obtained at each hour during different seasons and compared with those obtained from the latest available International Reference Ionosphere (IRI-2001) model. The diurnal variations of TEC show more or less similar trend during all the seasons (i.e. maximum around daytime and minimum around midnight) with the largest values of TEC during equinox. The variability of TEC is larger at night than by day during all the seasons. Comparison of the diurnal variation of the observed median values of TEC with those predicted by the IRI model reveals, in general, similar trend during all the seasons and at all local times except during winter, when the IRI exhibits diurnal peak of TEC at around 0900 hrs LT, and the observed median peak occurs at around 1400 hrs LT. Discrepancies between the IRI and the median values exceed 40% during nighttime for winter and equinox. However, during daytime, they are less than 20% for all the seasons, except winter morning hours. The TEC peak content increases by a factor of around 4 from solar minimum (1975-1976) to solar maximum (1989-1990).

Keywords: TEC, IRI Model, Incoherent scatter, Sunspot activity, Electron density

PACS No: 94.20.Ji ; 94.20.Gg ; 94.20.Ee

 

Indian Journal of Radio & Space Physics

Vol. 34, June 2005, pp. 191-196

 

 

Theoretical Z-R relationship for precipitating systems using

Mie scattering approach

 

Usha N Rao1, Abhijit Sarkar1 & M Mohan2

1Meteorology and Oceanography Group
2Marine Water Resources Group

Space Applications Centre, ISRO, Ahmedabad 380 015, India

Received 2 April 2004; revised 2 November 2004; accepted 19 April 2005

Making use of Mie scattering formulation from the classical electromagnetic theory, backscattering efficiency and radar reflectivity have been derived for a wide range of rain rates. The coefficients of Z-R (Z = radar reflectivity factor, R = rain rate, mm/h) relationships have been theoretically computed for 2.84 GHz (used in coastal Doppler radars), 13.8 GHz (used in the space-borne precipitation radar on-board TRMM satellite) and also 35.5 GHz (to be used in the forthcoming Global Precipitation Mission Radar). The Mie scattering results were compared with those obtained in the Rayleigh approximation. In the present work, analyses have been carried out for the well known Marshall-Palmer and Log-normal dropsize distributions. The theoretical approach described here however allows for any other dropsize distribution of precipitating system and operating radar frequency.

Keywords: Radar reflectivity, Rainfall rate, Mie scattering, TRMM

PACS No: 92.60 Jq ; 92.60 Ta

 

 

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, June 2005, pp. 197-205

 

 

Potential and field distribution in a cylindrical tube filled with a

dielectric material with a centre hole

 

B N Das & Arun Gayen

Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology,
Kharagpur 721 302, India

&

D R Poddar

Electronics and Telecommunication Engineering, Jadavpur University, Kolkata 700 032, India

Received 5 May 2004; revised 5 August 2004; accepted 16 August 2004

The paper presents a method of analysis of potential and field distribution in a cylindrical tube (metallic), covered at both ends with metallic plates, and containing a dielectric cylindrical shell whose axis coincides with the axis of the cylinder. The cylindrical surface and lower end are maintained at ground potential and the top plate is insulated and maintained at high potential. The resulting Laplace’s equation is solved using the method of separation of variables. The constants appear in the resulting equation are found from the boundary conditions followed by representation of the functions satisfying orthogonality condition in cylindrical co-ordinates. If the field intensity exceeds the breakdown limit, the resulting breakdown of the gas leads to plasma generation inside the structure, which can provide a convenient method of generation of laser beam.

Keywords: Metallic cylindrical tube, Dielectrics, Laplace’s equation, Cylindrical co-ordinates, Variables separation, Potential distribution, Field intensity distribution.

PACS No.: 41.20 Cv; 52.25 Mq

IPC Code: H01P 5/00; G01N 21/17

 

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol. 34, June 2005, pp. 206-209

 

 

FTFN based dual inputs current-mode allpass inverse filters

 

N A Shah & M A Malik*

Postgraduate Department of Electronics & Instrumentation Technology, The University of Kashmir, Srinagar 190 006 (India)

*E-mail: mohdameen2003@yahoo.co.in

Received 13 April 2004; revised 8 February 2005; accepted 15 April 2005

In this study, four new configurations implementing first-order current-mode allpass inverse filter signals are presented. The proposed generic circuit with two inputs and a single output employs a single FTFN, three resistors and a capacitor with both the inputs supporting the first-order allpass inverse responses separately. The topologies offer high output impedance, which enable easy cascading in current-mode. The realizability condition is simple and temperature invariant, being in the ratio of two grounded resistors. The additional advantage of the circuit is that the phase can be controlled by adjusting the values of passive components without disturbing the realizability condition. The tracking error performance for the filters has also been studied. The simulation results are also included.

Keywords: Four terminal floating nullor, Current-mode circuits, Allpass inverse filters

PACS No.: 84.30.Vn.

IPC Code: H03H 15/00; H03H 19/00