Comparison of Anomalous and Galactic Cosmic-Ray Oxygen at 1 au during 1997–2020

Using quiet-time measurements of element oxygen within the energy range 7.3--237.9 MeV nuc$^{-1}$ from ACE spacecraft at 1 au, we compare spectra and intensities anomalous Galactic cosmic rays (ACRs GCRs, respectively) during 1997--2020. Our analysis shows that transition ACR-dominated spectrum to GCR-dominated occurs energies $\sim$15 $\sim$35 nuc$^{-1}$, $E_t$ is found be well anticorrelated with varying solar activity. This first study ACR-GCR dependence on cycle variation. At below $E_t$, index power-law ($\gamma_1$) ranges -2.0 -0.5, whereas has a ($\gamma_2$) changing 0.3 0.8 ranging 237.9 nuc$^{-1}$. Both $\gamma_1$ $\gamma_2$ are positively correlated In addition, 24/25 minimum period, peak GCR intensity observed by about 8\% above its 2009 value, setting new record since space age, while ACR almost similar previous two cycles same pattern magnetic polarity, indicating different modulation mechanism between ACRs GCRs.