Low-energy anomalous cosmic rays in the ecliptic plane: 1-5 AU

Anomalous cosmic-ray (ACR) oxygen (O) fluxes in the energy range 0.5-5.0 Me V nucleon(-1) were measured in the ecliptic plane at 1 and 5 AU in 1997 and 1998. Using measurements from essentially identical instruments on the Adv anced Composition Explorer (ACE) and Ulysses spacecraft, we were able to mo nitor the decrease with time of the ACR O fluxes in the inner heliosphere d uring the onset of solar cycle 23. The data obtained from three time interv als that are relatively undisturbed by solar activity during this period sh ow that the e-folding time is similar to 140 +/- 40 days for the disappeara nce of 2-5 MeV nucleon(-1) ACR oxygen from the ecliptic plane at 5 AU.