Indian Journal of Radio & Space Physics

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(CODEN : IJRSAK ISSN : 0367-8393)

VOLUME 35

NUMBER 5

OCTOBER 2006

 

CONTENTS

 

Guest Editorial: Recent advancements in wireless communications

    M V S N Prasad*

 

305

IMF and geomagnetic activity during the solar wind disappearance event

Hari Om Vats*

 

307

 

Long-term variations of solar, interplanetary, geomagnetic indices and cosmic ray intensities A brief tutorial 

R P Kane*

 

 

312

Occurrence of type-I radio bursts and their association with solar cycle

Meera Gupta, V K Mishra, D P Tiwari* & A P Mishra

 

 

324

Latitudinal and diurnal variations of some important atomic oxygen dayglow emissions

Arun Kr Upadhayaya, Vir Singh* & Satish Tyagi

 

327

Predicted and measured bottomside total electron content under high and moderate solar activity conditions over New Delhi

N K Sethi* & R S Dabas

 

 

335

Seasonal and solar activity variation of NO2 over Ahmedabad

D K Chakrabarty*, Shailesh Patel & Prakash Vala

 

344

UHF wind profiler observations of monsoon low level jet over Pune

R R Joshi*, Narendra Singh, S M Deshpande, S H Damle & G B Pant

 

349

Shape of the rain drop size distributions and classification of rain type at Gadanki

Mahen Konwar, Diganta Kumar Sarma, Jyotirmoy Das & Sanjay Sharma*

 

360

A new velocity dependent variable hysteresis-margin-based call handover scheme

P P Bhattacharya* & P K Banerjee

 

368

Design of wideband and multiband microstrip array antennas

R B Konda, G M Pushpanjali, S N Mulgi*, S K Satnoor, P M Hadalgi &
P V Hunagund

 

372

___________________

*Authors for correspondence

 

 

 

 

 

 

 

 

Indian Journal of Radio & Space Physics

Vol 35, October 2006, pp. 307-311

 

IMF and geomagnetic activity during the solar wind disappearance event

Hari Om Vats

Physical Research Laboratory, Ahmedabad 380 009, India

e-mail:vats@prl.ernet.in

Received 5 August 2005; revised 29 January 2006; accepted 10 February 2006 

There was a very peculiar situation reported during 11-12 May 1999, that the "solar wind disappeared". This was one of the long lasting, low velocity and low density solar wind events and was caused by the passage of a void around the earth and its environment. The interplanetary magnetic field (IMF), especially, the north-south component (Bz) remained quiet during the event. However, it showed a fast and intense fluctuation after the passage of this low solar wind region or void. The equatorial Dst and Ap variations indicate a mild geomagnetic storm after the passage of void. This mild geomagnetic storm is probably due to fluctuations in Bz whose value varies from 12 to 9 nT.

Keywords: Interplanetary magnetic field, Geomagnetic activity, Solar wind, Solar wind disappearance

PACS No.: 94.30 Va; 94.30 Lr; 94.30 Di

 

 

 

Indian Journal of Radio & Space Physics

Vol. 35, October 2006, pp. 312-323

 

Long-term variations of solar, interplanetary, geomagnetic indices and
comic ray intensitiesA brief tutorial

R P Kane

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

e-mail: kane@dge.inpe.br

Received 9 September 2005; revised 16 January 2006; accepted 28 April 2006

The long-term variations of the 12-month running means of several solar, interplanetary and geomagnetic parameters during the last several sunspot cycles revealed that during cycles 11-23 (1868-2004), the geomagnetic aa index showed several peaks within 3-5 years around the sunspot maxima, with some peaks during the declining phases of the sunspot cycles, whereas the sunspot numbers Rz showed smooth but broad maxima for 2-3 years in each cycle. The calcium plage area also showed multiple peaks but none in the declining phases. The 11-yr running means showed very good parallelism between Rz, aa index and global sea-surface temperature (SST). During 1940-2004, Rz and F10 (2800 MHz radio emission) showed similar 11-yr fluctuations of varying amplitudes, but coronal index, CI, showed monotonically increasing amplitudes by almost a factor of two. The open magnetic flux emanating from the sun during 1968-2004 showed long-term fluctuations, very different at low and high solar latitudes. The variations of the fluxes at low latitude (0-45o) were almost parallel to the sunspot cycle (there was a slight N-S asymmetry), while fluxes at high latitudes (45o-90o) were almost anti-parallel to the sunspot cycle. Cosmic ray neutron monitor intensities at Climax were well anti-correlated with sunspot cycle and interplanetary magnetic field (B), but poorly correlated with interplanetary number density (N), solar wind speed (V), and geomagnetic index aa. The geomagnetic index aa was best correlated with the product VB.

Keywords: Solar indices, Geomagnetic index, Sunspots, Cosmic ray intensity, Interplanetary magnetic field.

PACS No.: 94.30 Va; 96.60 Qc; 96.40 Cd

 

 

Indian Journal of Radio & Space Physics

Vol. 35, October 2006, pp. 324-326

 

Occurrence of type-I radio bursts and their association with solar cycle

Meera Gupta, V K Mishra, D P Tiwari & A P Mishra

Department of Physics, A P S University, Rewa (M P)

E-mail: vkmishra74@yahoo.com

Received 8 April 2005; revised 12 April 2006; accepted 17 May 2006

A minimum between solar cycle 22 and 23 has been defined earlier on the basis of type-I radio burst only. In the present paper a re-visit to the occurrence of type-I radio bursts in relation to general level of solar activity (sunspot number) is made covering the minima of cycle 21 to complete cycles 22-23. The study shows that, it is not appropriate to speculate solar cycle minima on the basis of type-I radio burst only.

Keywords: Type-I radio burst, Solar cycle, Solar activity, Sunspot number

PACS No.: 96.60. Rd; 96.60. Qc

 

Indian Journal of Radio & Space Physics

Vol. 35, October 2006, pp. 327-334

 

Latitudinal and diurnal variations of some important atomic

oxygen dayglow emissions

 

Arun Kr Upadhayaya1, Vir Singh2 & Satish Tyagi3

1Amity School of Engineering & Technology, Bijwasan , New Delhi 110 061, India

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

3BSNL Saharanpur, Uttar Pradesh

Email: akuphdph@iitr.ernet.in, virphfph@iitr.ernet.in

Received 23 June 2005; revised 13 January 2006; accepted 6 March 2006

In the present paper the latitudinal and diurnal variations of 5577 , 6300 , 7320 and 8446 dayglow emissions are presented. The volume emission rate profiles for these emissions are calculated using updated Glow model. To test the model, the calculated emission rate profiles for 5577 and 6300 are compared with the measurements of Wind Imaging Interferometer (WINDII) for which data are available. The emission intensities have been studied on 15 Jan. 1995 and 15 June 1995 using Tobiska solar EUV flux model. These calculations show that the intensity is maximum at 1200 hrs LT for both the dates at all latitudes for 5577 and 8446 emissions. The position of maximum intensity is found to be variable for 6300 emission on 15 January. At 30N latitude, the peak is found at 1000 hrs LT, while at 5N and 45N the maximum intensity is found to occur at nearly 1200 hrs LT. On 15 June, the intensity of 6300 emission does not show any pronounced peak and emission is found to vary within 15% between 0800 and 1400 hrs LT. On 15 January, the 7320 emission shows that the peak of maximum intensity occurs at nearly 1200 hrs LT at 5N, which moves quite close to 1000 hrs LT at 30N and 45N latitudes. On the other hand, the peak of maximum intensity for 7320 emission is found between 1200 hrs and 1400 hrs LT at all latitudes on 15 June. The smooth variation in 8446 intensity may be attributed due to steadiness of photoelectron fluxes at higher energies.

Keywords: Dayglow emission, Atomic oxygen, Glow model, Solar EUV flux, Wind imaging interferometer

PACS No.: 94.10.Fa; 94.10.Rk; 94.10.Gb; 96.60 Rd

IPC Code: G01T1/11; G01M11/00

 

 

Indian Journal of Radio & Space Physics

Vol. 35, October 2006, pp. 335-343

 

Predicted and measured bottomside total electron content under high and
moderate solar activity conditions over New Delhi

 

N K Sethi & R S Dabas

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

Received 29 March 2006; revised 11 July 2006; accepted 23 August 2006

Digital ionosonde measurements at a low-middle latitude station, New Delhi (28.6N, 77.2E, dip 42.4N) are used to derive bottomside total electron content (BTEC) for a period of high (2001-2002) and moderate (2003) solar activity periods. These observations are then used to evaluate the predictability of the latest available IRI-2001 model using both the options, i.e. (B0 Tab. and Gulyaeva). The study reveals that for both the solar activity periods, the diurnal variations of BTEC show more or less similar trend during all the seasons (i.e. maximum around daytime and minimum around midnight) and BTEC exhibits a large day-to-day variability at any given local time. Comparison of BTEC with those predicted by the IRI model using both the options during moderate solar activity reveals, in general, good agreement, except for post-noon hours during summer and equinox. However around noontime, IRI (B0 Tab.) option shows somewhat better agreement with the observations than by IRI (Gulyaeva) option. During high solar activity, a comparative analysis shows that discrepancies do exist during winter and equinox during daytime with both the options of the IRI, however the agreement between the IRI (B0 Tab.) and observations is reasonably good for summer during daytime, whereas IRI (Gul.) option overestimates the BTEC. Solar activity variations of observed median BTEC show that the peak content in general increases by a factor of more than two from moderate to high solar activity.

Keywords: Total electron content; Bottomside total electron content; Solar activity; Digital ionosonde; Ionosonde

PACS No: 94.20.Dd

 

 

 

Indian Journal of Radio & Space Physics

Vol.35, October 2006, pp. 344-348

 

Seasonal and solar activity variation of NO2 over Ahmedabad

D K Chakrabarty

Centre for Environment Survey, Vidyanagar Society 29/251, Ahmedabad 380 015, Gujarat, India

and

Shailesh Patel & Prakash Vala

St. Xaviers College, Navarangpura, Ahmedabad 380 009, Gujarat, India

Received 21 September 2005; revised 12 June 2006; accepted 1 August 2006

Nitrogen dioxide, NO2, has strong absorption signatures in 436-448 nm region. Using this property, column density of this species has been determined at Ahmedabad, a low latitude station. Absorption spectrum has been measured by a ground-based spectroscopy technique during twilight period. Scattered zenith sunlight has been used as the source of light. The twilight slant column density (SCD) values have been found to be ~ 1017 cm2. A summer maximum and a winter minimum, and a decreasing trend of NO2 with an increase of solar activity level are seen. These results have been compared with the UARS and GOME satellite values.

Keywords: Nitrogen dioxide, Nitrogen dioxide column density, Absorption spectrum; Sunlight absorption

PACS No.: 94.10.Dy; 94.10.Fa; 94.10.Gb

 

 

Indian Journal of Radio & Space Physics

Vol. 35, October 2006, pp. 349-359

 

UHF wind profiler observations of monsoon low level jet over Pune

R R Joshi, Narendra Singh, S M Deshpande, S H Damle & G B Pant

Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune 411 008, India

E-mail: rrjcpt@tropmet.res.in

Received 13 October 2005; revised 24 April 2006; accepted 27 July 2006

Data from a UHF (404 MHz) wind profiler during the active monsoon periods in 2003, 2004 and 2005 have been analyzed. Details of July 2003 as representative have been presented, which clearly show existence of jet stream over the wind profiler site at Pune (18.3 N, 73.5 E) throughout the day and night. The paper presents observed occurrence statistics of low level jet (LLJ) during monsoon month of July 2003. Wind speeds in excess of 20 ms1 are frequently observed during active monsoon phase and peak found around a height of 2-3 km. Wind speed then decreases on either side of the peak without more than 40 change in the prevailing wind directions. The evolution of monsoon LLJ, particularly its diurnal variation and its difference with respect to nocturnal LLJ phenomenon have been brought out. The observed vertical velocities are predominantly upward, up to 4 km in the presence of LLJ with mean downward momentum flux. This upward directed clear air vertical velocities probably help in developing convective systems. The energy dissipation rates (Є) are also estimated and shown to be maximum near the LLJ height.

Keywords: Jet stream; Wind profiler; Turbulence; Low level jet

PACS No.: 92.60.Ek

 

Indian Journal of Radio & Space Physics

Vol. 35, October 2006, pp. 360-367

 

 

 

 

 

Shape of the rain drop size distributions and classification of rain type at Gadanki

Mahen Konwar, Diganta Kumar Sarma, Jyotirmoy Das1 & Sanjay Sharma

Kohima Science College, Jotsoma, Kohima, Nagaland 797 002, India

1Electronics and Communication Sciences Unit, Indian Statistical Institute, Kolkata 700 108, India

[e-mail: sanjay_sharma11@hotmail.com]

Received 26 August 2005; revised 22 May 2006; accepted 3 July 2006

Three different rain drop size distribution (RDSD) models namely exponential, lognormal and gamma distribution
are fitted to RDSD as spectra observed from Joss-Waldvodgel Disdrometer (JWD) at Gadanki (13.8N, 79.18E).
Gamma distribution shows overall good agreement with observed RDSD for all ranges of rainfall rate. Rainfall rate calculated from gamma drop size distribution is found to have minimum root mean square error and biasing compared
to exponential or lognormal distribution. The intrinsic shape of RDSD is found out from normalized RDSD which
follows an S shape for both low rain
10 mm h-1 and high rain > 10 mm h-1. The convective and stratiform
rains are separated for an event. The equations of separation for convective and stratiform rains have been derived assuming power law for log10 (R) - Dm, log10 (N0*) - log10 (R) and log10 (N0*) - Dm. The coefficients and exponent for these equations are ,,, and ,, , respectively.

Keywords: Rain drop size distribution (RDSD), Exponential DSD, Lognormal DSD, Gamma DSD, Convective rain,
Stratiform rain

PACS No: 92.60.Jq

IPC Code: G01S13/95; G06T1/40

 

 

Indian Journal of Radio & Space Physics

Vol. 35, October 2006, pp. 368-371

 

A new velocity dependent variable hysteresis-margin-based call handover scheme

P P Bhattacharya

Department of Electronics and Communication Engineering, Netaji Subhash Engineering College, Techno City, Police Para, Garia, Kolkata 700 152, India

E-mail: partha_p_b@yahoo.com

and

P K Banerjee

Department of Electronics & Telecommunication Engineering, Jadavpur University, Kolkata 700 032, India

Received 25 January 2005; revised 13 June 2006; accepted 11 August 2006

The increase of mobile users compels the uses of picocells in cellular mobile communication and the task of handover becomes critical. Handover response should be faster and also should depend on mobile velocity to avoid unwanted call termination for high velocity mobiles and unnecessary handover for low velocity mobiles. In this paper, a path loss exponent and user-velocity-dependent variable hysteresis-margin-based call handover algorithm is proposed and studied. The handover algorithm is tested and found to give desired response.

Keywords: Mobile cellular communication system, Handover, Hysteresis margin

PACS No.: 84.40 Ua; 07.57 Kp

IPC Code: G01S 13/50

 

Indian Journal of Radio & Space Physics

Vol. 35, October 2006, pp. 372-375

 

Design of wideband and multiband microstrip array antennas

 

R B Konda, G M Pushpanjali, S N Mulgi, S K Satnoor, P M Hadalgi & P V Hunagund

Department of Applied Electronics, Gulbarga University, Gulbarga (Karnataka) 585 106, India

Received 8 November 2005; revised 17 April 2006; accepted 29 August 2006

A method for improving the impedance bandwidth of microstrip array antenna by incorporating a slot in the radiating patches is presented. It is further described by using a common parasitic element, which is gap-coupled to the radiating edges of the rectangular patches and embedding a slot in the parasitic element. The use of gap-coupling and slot in the parasitic element makes the antenna to have wider impedance bandwidth and leads to its operation at more than one band of frequencies. The design concepts of antenna are described and experimental results discussed. These antennas may find application in mobile communication.

Keywords: Microstrip slot antenna, gap-coupled antenna

PACS No.: 84.40.Ba

IPC Code: H01Q9/00; H01Q21/00; H01Q23/00