Virendra Yadav

Aryabhatta Research Institute of Observational Sciences (ARIES)

Scintillations on VHF radio signal are sparsely observed during daytime due to unavailability of strong electron density irregularities in equatorial E- or F-region. Type I/II irregularities observed at E-region altitudes during the daytime are linked with either two-stream or gradient drift instability. The occurrence of these irregularities in pr...

On a geomagnetically quiet night of 07 July 2018, the allsky imager at Hanle, Leh Ladakh (32.7°N, 78.9°E; Mlat. ∼24.1°N), India captured a number of plasma structures in O(1D) 630.0 nm airglow emission. In a short observational period of around 3 hours, two different Medium Scale Traveling Ionospheric Disturbances (MSTIDs) and two different mid‐lat...

We report a unique simultaneous occurrence of two plasma structures using a 630.0 nm all-sky airglow imager in Hanle, India. The characteristics indicate that the observed structures are Medium Scale Travelling Ionospheric Disturbances (MSTIDs) of different types, namely periodic and single dark band. Based on previous understandings of Perkins ins...

In this paper, we study the interaction between a nighttime Medium Scale Traveling Ionospheric Disturbance (MSTID) and geomagnetic north-south oriented field-aligned plasma depletion structure over Hanle, Leh Ladakh (32.7°N, 78.9°E; Mlat. ∼24.1°N), India on a geomagnetically quiet night (06 May 2019, Ap = 4). The results are based on the observatio...

A sporadic E layer with dense ionization blocks the upper ionospheric layers in ionosonde observations and it is called, blanketing sporadic E (Esb). Although earlier studies have demonstrated that Esb occurrence is dependent on solar activity, seasons, local time and equatorial electrojet/counter electrojet (EEJ/CEEJ) strength, the physics behind...

This paper reports a rare interaction between two fronts of nighttime medium scale traveling ionospheric disturbances (MSTIDs) and associated phenomena observed over geomagnetic low-mid latitude transition region on a geomagnetically quiet night (Ap=5) of 21 May, 2020. The event was observed for nearly eight hours in O(1D) 630.0 nm airglow images c...

We have installed a multi-wavelength allsky airglow imager over the Indian Himalayan region at Hanle, Leh Ladakh, (32.7°N, 78.9°E; dip lat. ∼24.1°N). This is the first of its kind that is installed in the Himalayan region at an altitude of around 4200 m above the mean sea level. The high sensitive thermoelectrically cooled CCD based imager is equip...

Generation of equatorial spread F (ESF) irregularities resulting from magnetic disturbance is known for past few decades. However, better prediction models for this phenomenon are still lacking. Magnetic storms also affects the F region plasma drifts. In this work we examined variability in (i) occurrence of such freshly generated ESF and (ii) low-...

Visual observations of meteor showers have been carried out for many decades by astronomers. Modern developments in imaging systems have advanced our knowledge about the shower dynamics and their origin. We have made an attempt to make a portable video recording system to observe meteor showers. The system consists of a camera capable of recording...

We have studied the Forbush decrease (FD) event that occurred on February 14, 1978 using 43 neutron monitor observatories to understand the global signature of FD. We have studied rigidity dependence of shock amplitude and total FD amplitude. We have found almost the same power law index for both shock phase amplitude and total FD ampli- tude. Loca...

We present the seasonal and local time occurrence of ionospheric F3-layer over Tirunelveli (geo. lon. 77.8° E, geo. lat. 8.7° N, dip 0.7°) during extremely low and prolonged solar activity period (2007–2009). CADI ionosonde observations from this station are used in the present study. We find that the occurrence of F3-layer is nearly three times hi...

Temporal variation of secondary cosmic rays (SCR) flux was measured during the several full and new moon and days close to them at Department of Physics, University of Mumbai, Mumbai (Geomagnetic latitude: 10.6 N), India. The measurements were done by using NaI (Tl) scintillation detector with energy threshold of 200 keV. The SCR flux shows sudden...

A thin and highly dense sporadic E layer, which can occasionally block the upper ionospheric layers, is called blanketing sporadic E (Esb). We present the statistical seasonal local time occurrence pattern of Esb at equatorial station Tirunelveli (8.7° N, 77.8° E, dip latitude 0.7° N) during the extended minimum of solar cycle 24 (2007–2009). In sp...

Given the renewed scientific interest in lunar exploration missions, complete understanding of lunar near surface environment and its exosphere under different conditions is of paramount importance. Lunar exosphere has been extensively studied by ground based observations [18,19,20,21,22,23] and hypothesized by different models[1,2,3,4,5,6,7,8,9,10...

Temporal variation of secondary cosmic rays (SCR) flux was measured during the total lunar eclipse on December 10, 2011 and the subsequent Full Moon on January 8, 2012 from Mumbai (Geomagnetic latitude: 10.6 ∘ N), India. The measurements were done by using NaI (Tl) scintillation detector by keepingwith energy threshold of 200 keV. The SCR flux show...

Temporal variation of secondary cosmic rays (SCR) flux was measured during the total lunar eclipse on December 10, 2011 and the subsequent full moon on January 8, 2012. The measurements were done at Department of Physics, University of Mumbai, Mumbai (Geomagnetic latitude: 10.6 N), India using NaI (Tl) scintillation detector by keeping energy thres...

In this paper statistical investigation on the daytime descending intermediate layers near the anomaly crest region, Allahabad (25.3N, 81.5E, dip latitude 16.24N) using Canadian advanced digital ionosonde (CADI) data under extremely prolonged low solar activity period during 2007-2009 has been presented. This layer occurs in the altitude range of 1...

A thin and highly dense sporadic E layer, which can occasionally block the upper ionospheric layers, is called blanketing sporadic E (E sb). We present the statistical seasonal local time occurrence pattern of E sb at equatorial station Tirunelveli (8.7 • N, 77.8 • E, dip latitude 0.7 • N) during the extended minimum of solar cycle 24 (2007–2009)....

A thin and highly dense sporadic E layer, which can occasionally block the upper ionospheric layers, is called blanketing sporadic E (E sb). We present the statistical seasonal local time occurrence pattern of E sb at equatorial station Tirunelveli (8.7 • N, 77.8 • E, dip latitude 0.7 • N) during the extended minimum of solar cycle 24 (2007–2009)....

Plasma inhomogenities or irregularities in the nighttime F-region of the equatorial and low latitude ionosphere are known as equatorial spread F (ESF). These irregularities have been studied by practically every radio and optical experimental tool available for space research in addition to theoretical and modeling studies. These irregularities sho...

The gamma ray flux was measured during the annular solar eclipse on January 15, 2010 at Rameswaram, India using NaI (Tl) scintillator detectors and the variation in charged particles and gamma rays was monitored using Geiger Mu¨ller (GM) counters. The gamma ray flux variation was studied in energy range of 0.1–3.5 MeV. Weather parameters (temperatu...