We study the temporal evolution of the power rigidity spectrum of the first (27days) and the
second (14days) harmonics of the 27-day variation of the galactic cosmic ray intensity
measured by neutron monitors in the period of 1965–2002. The rigidity spectrum of these
variations can be approximated by a power law. We show the rigidity spectra of the first and
the second harmonics of the 27-day variation of the galactic cosmic ray intensity have similar
time profiles. These spectra are hard (γ≈ 0.5±0.1) and soft (γ≈ 1.1±0.2) during solar …