Alignment of air showers produced by ultra-high energy cosmic rays at the Pierre Auger Observatory

We show that the energy-weighted angular (zenith, azimuth) distribution of extensive air showers (EAS), produced by Ultra High Energy (UHE) cosmic rays at the Pierre Auger Observatory (PAO), has a thrust axis almost transverse to the interplanetary magnetic field (IMF), with a thrust value $Tp\ge 0.64$ ( where 1.0 means a perfect alignment and 0.5 isotropy). This behavior strongly suggests an effect of the IMF on the charged shower particles, producing additional lateral scattering. We discuss the weakening of the Earth’s magnetic field during geomagnetic storms (30% of observational time) when the IMF becomes preponderant, strengthening the alignment.