High Energy Physics Seminars

Small-scale anisotropy in cosmic ray distribution observed by GRAPES-3 at TeV energies

by Ms. Medha Chakraborty (DHEP, TIFR)

Tuesday, May 30, 2023 from to (Asia/Kolkata)
at TIFR, Mumbai ( D-405 )
The deflection of cosmic rays (CRs) in the interstellar magnetic fields results in an almost isotropic flux, as observed on Earth. The presence of anisotropies on various angular scales of magnitude ∼ 10−4–10−3 has been predicted by theoretical models. These predictions encompass small-scale anisotropic formations on angular scales of up to 60°, arising from the relative diffusion of CRs in the local turbulent magnetic fields, the contribution of nearby sources, and other factors. Over the past decade, a number of large air shower experiments located in the northern and southern hemispheres have detected CR anisotropy across multiple angular scales. The GRAPES3 experiment, located at 11.4° N latitude, has the unique advantage of observing a substantial portion of both hemispheres and covering around 56% of the sky at TeV energies. By analysing four years of air shower data collected between 2013 and 2016, we have observed two striking hot-spot regions of angular scale ∼ 60° that are consistent with observations reported by other air shower experiments such as Milagro, ARGO-YBJ, and HAWC. The analysis methods, observed anisotropy structures, their features, and comparisons with other experiments will be presented.