After two years of operation, the High-Altitude Water Cherenkov (HAWC) Observatory has analyzed the TeV cosmic-ray sky over an energy range between 2.0 and 72.8 TeV. Like other detectors in the northern and southern hemispheres, HAWC observes an energy-dependent anisotropy in the arrival direction distribution of cosmic rays. This anisotropy is dominated by a dipole moment with phase in R.A. α ≈ 40° and amplitude that slowly rises in relative intensity from 8 ×10-4 at 2 TeV to 14 ×10-4 around 30 TeV, above which the dipole decreases in strength. A significant large-scale (>60° in angular extent) signal is also observed in the quadrupole and octupole moments, and significant small-scale features are also present, with locations and shapes consistent with previous observations. Compared to previous measurements in this energy range, the HAWC cosmic-ray sky maps improve on the energy resolution and fit precision of the anisotropy. These data can be used in an effort to better constrain local cosmic-ray accelerators and the intervening magnetic fields.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science