60 citations · 302 across the 19 of their papers we have counts for
20 papers
Imaging Spectropolarimeter for Multi-application Solar Telescope at Udaipur Solar Observatory: Characterization of polarimeter and preliminary observations
Alok Ranjan Tiwary, Shibu K. Mathew, A. Raja Bayanna +2
Multi-Application Solar Telescope (MAST) is a 50 cm off-axis Gregorian telescope and started operational recently at Udaipur Solar Observatory (USO). For understanding the evolutio…
Analysis of sudden variations in photospheric magnetic fields during a large flare and their influences in the solar atmosphere
Brajesh Kumar, A. Raja Bayanna, P. Venkatakrishnan +1
The solar active region NOAA 11719 produced a large two-ribbon flare on 11 April 2013. We have investigated the sudden variations in the photospheric magnetic fields in this active…
Flux Emergence in the Solar Active Region NOAA 11158: The Evolution of Net Current
P. Vemareddy, P. Venkatakrishnan, S. Karthikreddy
We present a detailed investigation on the evolution of observed net vertical current using a time series of vector magnetograms of the active region (AR) NOAA 11158 obtained from…
Membrane based Deformable Mirror: Intrinsic aberrations and alignment issues
A. Raja Bayanna, Rohan E. Louis, S. Chatterjee +2
A Deformable Mirror (DM) is an important component of an Adaptive Optics system. It is known that an on-axis spherical/parabolic optical component, placed at an angle to the incide…
Anomalous flows in a sunspot penumbra
Rohan E. Louis, Christian Beck, Shibu K. Mathew +1
High-resolution spectropolarimetric observations of active region NOAA 11271 were obtained with the spectro-polarimeter on board Hinode to analyze the properties of an anomalous fl…
Narrow-Band Imaging System for the Multi-application Solar Telescope at Udaipur Solar Observatory: Characterization of Lithium Niobate Etalons
A. Raja Bayanna, Shibu K. Mathew, P. Venkatakrishnan +1
Multi-application Solar Telescope is a 50 cm off-axis Gregorian telescope that has been installed at the lake site of Udaipur Solar Observatory. For quasi-simultaneous photospheric…
A Study of the relation between intensity oscillations and magnetic field parameters in a Sunspot: Hinode Observations
Ankala Raja Bayanna, Shibu K Mathew, Brajesh Kumar +2
We present properties of intensity oscillations of a sunspot in the photosphere and chromosphere using G~band and CaIIH filtergrams from Hinode. Intensity power maps as function of…
On the line profile changes observed during the X2.2 class flare in the active region NOAA 11158
A. Raja Bayanna, Brajesh Kumar, P. Venkatakrishnan +4
The solar active region NOAA 11158 produced a series of flares during its passage through the solar disk. The first major flare (of class X2.2) of the current solar cycle occurred…
Observations of Supersonic Downflows in a Sunspot Light Bridge as Revealed by Hinode
Rohan E. Louis, Luis R. Bellot Rubio, Shibu K. Mathew +1
Recent high resolution spectropolarimetric observations from Hinode detected the presence of supersonic downflows in a sunspot light bridge (Louis et al. 2009). These downflows occ…
Analysis of a Fragmenting Sunspot using Hinode Observations
Rohan E. Louis, B. Ravindra, Shibu K. Mathew +3
We employ high resolution filtergrams and polarimetric measurements from Hinode to follow the evolution of a sunspot for eight days starting on June 28, 2007. The imaging data were…
On the flare induced seismicity in the active region NOAA 10930 and related enhancement of global waves in the sun
Brajesh Kumar, P. Venkatakrishnan, Savita Mathur +2
A major flare (of class X3.4) occurred on 13 December 2006 in the active region NOAA 10930. The energy released during flares is also known to induce acoustic oscillations in the S…
Observations of Supersonic Downflows Near the Umbra-Penumbra Boundary of Sunspots as Revealed by Hinode
Rohan E. Louis, Luis R. Bellot Rubio, Shibu K. Mathew +1
High resolution spectropolarimetric observations by Hinode reveal the existence of supersonic downflows at the umbra-penumbra boundary of 3 sunspots that was recently reported by L…
Supersonic Downflows at the Umbra-Penumbra Boundary of Sunspots
Rohan E. Louis, Luis R. Bellot Rubio, Shibu K. Mathew +1
High resolution spectropolarimetric observations of 3 sunspots taken with Hinode demonstrate the existence of supersonic downflows at or close to the umbra-penumbra boundary which…
Can major solar flares excite high-frequency global waves in the Sun ?
Brajesh Kumar, Savita Mathur, R. A. Garcia +1
The study of low-degree high-frequency waves in the Sun can provide new insight into the dynamics of the deeper layers of the Sun. Here, we present the analysis of the velocity obs…
On the flare induced high-frequency global waves in the Sun
Brajesh Kumar, Savita Mathur, R. A. Garcia +1
Recently, Karoff and Kjeldsen (2008) presented evidence of strong correlation between the energy in the high-frequency part (5.3<ν<8.3 mHz) of the acoustic spectrum of the Sun and…
Supersonic Downflows in a Sunspot Light Bridge
Rohan Eugene Louis, Luis R. Bellot Rubio, Shibu K. Mathew +1
We report the discovery of supersonic downflows in a sunspot light bridge using measurements taken with the spectropolarimeter on board the Hinode satellite. The downflows occur in…
Global Twist of Sunspot Magnetic Fields Obtained from High Resolution Vector Magnetograms
Sanjiv Kumar Tiwari, P. Venkatakrishnan, K. Sankarasubramanian
The presence of fine structures in the sunspot vector magnetic fields has been confirmed from Hinode as well as other earlier observations. We studied 43 sunspots based on the data…
Helicity at Photospheric and Chromospheric Heights
S. K. Tiwari, P. Venkatakrishnan, K. Sankarasubramanian
In the solar atmosphere the twist parameter has the same sign as magnetic helicity. It has been observed using photospheric vector magnetograms that negative/positive helicity…
Variation of Acoustic Power with Magnetic Field as seen in Gong+ Data
P. Venkatakrishnan, Brajesh Kumar, S. C. Tripathy
The acoustic spectra in sunspots are known to be richer in higher frequency power. We have attempted a generalized study of the effect of magnetic fields on the shape of the acoust…
Search for Spatial Variability in the Solar Acoustic Spectrum
P. Venkatakrishnan, Brajesh Kumar, S. C. Tripathy
Motivated by the various examples of spatial variability in the power of the acoustic spectrum, we attempted to look for spatial variability in the peak frequency of the spectrum.…