• 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

      ABHA SINGH S. S. RAO V. S. RATHORE SUDESH K. SINGH A. K. SINGH

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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.

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