arXiv subjects

Shiv Narayan Yadav

Publications and source records attributed to Shiv Narayan Yadav.

3 recordsLinked to original sources

arXiv2026

Study of Butterfly-Shaped Coronal Hole Evolution Across the Solar Disk

We studied the evolution of a butterfly-shaped coronal hole (CH) observed from 2025 September 8 to 14 using SDO/AIA 193~Å images and SDO/HMI line-of-sight magnetograms. The CH boundary was identified using a fixed 100~DN intensity threshold, and its area, mean EUV intensity, and total unsigned magnetic flux were tracked across the solar disk. As the CH approached the central meridian, its area increased from approximately $7.70\times10^{16}$ to $1.63\times10^{17}$~m$^{2}$ and its unsigned magnetic flux from $8.68\times10^{21}$ to $1.91\times10^{22}$~Mx, while the mean 193~Å intensity decreased from about 61 to 45~DN. The area and unsigned flux showed similar temporal trends, whereas the intensity varied oppositely. Near central-meridian passage, these quantities remained relatively stable for several days. A high-speed solar-wind stream was detected at 1~AU about 2--4 days later, reaching 600--750~km~s$^{-1}$, consistent with the CH being its likely solar source. These results link the morphological, radiative, and magnetic evolution of the CH with the subsequent high-speed solar-wind stream.

astro-ph.SR↗

arXiv2025

Energy-dependent anisotropy of cosmic-ray muons: A twelve-year study with IceCube Neutrino Observatory

We present a comprehensive, energy-resolved study of cosmic-ray muon anisotropy using 12 years (2011-2023) of data from the IceCube Neutrino Observatory, comprising 7.92 x 10^11 events in the 13 TeV to 5.3 PeV energy range. Dividing the spectrum at log-scale energy 5 GeV, we contrast low- and high-energy anisotropy features via sidereal modulation, angular profiles, Fourier analysis, and full-sky HEALPix mapping. Gaussian and power-law fits to energy distributions are evaluated using chi-squared, reduced chi-squared, and Bayesian Information Criterion. Results show strong dipolar and large-scale anisotropy at low energies, likely due to geomagnetic and atmospheric effects, while high-energy muons display weaker, more localized structures consistent with reduced scattering and source-related anisotropy. Energy distributions are well fit by Gaussians, especially in the 6.5 to 100 bin, validating IceCube's reconstruction at PeV scales. These findings confirm energy-dependent anisotropy and support cosmic-ray diffusion models.

astro-ph.HE↗

arXiv2017

Preferred alignments of angular momentum vectors of galaxies in six dynamically unstable Abell clusters

A spatial orientation of angular momentum vectors of galaxies in six dynamically unstable Abell clusters (S1171, S0001, A1035, A1373, A1474 and A4053) is studied. For this, two-dimensional observed parameters (e.g., positions, diameters, position angles) are converted into three-dimensional rotation axes of the galaxy using `position angle - inclination' method. The expected isotropic distribution curves for angular momentum vectors are obtained by performing random simulations. The observed and expected distributions are compared using several statistical tests. No preferred alignments of angular momentum vectors of galaxies are noticed in all six dynamically unstable clusters supporting hierarchy model of galaxy formation. These clusters have a larger value of velocity dispersion. However, local effects are noticed in the clusters that have substructures in the 1D-3D number density maps.

astro-ph.GA↗