• S. S. RAO

      Articles written in Journal of Astrophysics and Astronomy

    • Day time whistlers observed at low latitude Varanasi ($L = 1.078$)

      S. B. SINGH S. S. RAO A. K. SINGH

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      We present results of the first time observations of whistlers during day time (sunrise) on 4th January 2017 at 01 UT(UT$+$5.30 $=$ IST) at Indian low latitude ground station Varanasi (geomag. lat. 14$^{\prime}$55$^{\prime}$ N, geomag. long. 153$^{\prime}$54$^{\prime}$ E, L.1.078). The main goal of analysis is to study the propagation characteristic of the observed whistlers during the day time (sunrise). These whistlers were observed during the quiet geomagnetic conditions (Dst-index $=$ $–$8 nT). The dispersions of the observed whistlers are found between 11.16 and 14.78 s$^{1/2}$, which shows that the observed whistlers have propagated in the ducted mode and the whole propagation path of whistlers lies in the ionosphere. Their columnar ionospheric electron contents lie between 23.57 TECU and 39.44 TECU. The ionospheric parameters derived from whistler data at Varanasi compare well with othermeasurements made by other techniques.

    • Effect of intense solar flares on TEC variation at low-latitude station Varanasi


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      The effect of intense solar flares on total electron content (TEC) variability during the declining phase of solar cycle-24 is studied at the low-latitude station at Varanasi, India (Geog. Lat. 25.31$^{\circ}$ N, Geog. Long. 82.97$^{\circ}$ E, Geomag. Lat. 16.54$^{\circ}$ N, Geomag. Long. 157.09$^{\circ}$ E). In the present paper, we have chosen the intense solar flares that occurred during 9–13 March 2015, 1–2 January 2016, 12–14 February 2016, 6–8 August 2016, and 6–8 September 2017 in the solar cycle-24 period for which the data is available. Our results showed significant enhancements in TEC up to the order of 15 TECU during and after the solar flare events. We have also given a brief account of solar flare effect in TEC with and without geomagnetic disturbances, local time effects (solar zenith angle effects) and changing the location of the solar active region. In a few cases, our results revealed a delay in TEC response during the flare peak time as well as recovery time.

    • Effect of intense geomagnetic storms on low-latitude TEC during the ascending phase of the solar cycle 24


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      The results presented in this paper are obtained from low-latitude ionospheric total electron content (TEC) variation during the chosen geomagnetic storm events happening during the solar cycle 24.We include the four intense geomagnetic storms that occurred on 26 September 2011, 15 July 2012, 19 February 2014 and 20 December 2015, depending upon the availability of TEC data. For this, we have used the TEC data from low-latitude station Varanasi (geographic latitude 25$^{\circ}$, 16$'$N, geographic longitude 82$^{\circ}$, 59$'$E and geomagnetic latitude 16$^{\circ}$, 24$'$N) and an equatorial station Bengaluru (geographic latitude 13$^{\circ}$, 02$'$N, geographic longitude 77$^{\circ}$, 34$'$E and geomagnetic latitude 04$^{\circ}$, 68$'$N). The storm-induced TEC changes at chosen stations have been discussed in terms of local time, storm wind effect, neutral wind, composition changes and variation in the dawn–dusk component of the interplanetary electric field (IEF $E_y$).

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    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

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      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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