  It has been argued for years that the accretion mode changes from bright
active galactic nuclei (AGNs) to low-luminosity AGNs (LLAGNs) at a rough
dividing point of bolometric Eddington ratio $\lambda \sim 10^{-2}$. In this
work, we strengthen this scenario through investigation of the relationship
between the radio loudness $R_{\rm UV}$ and the optical-to-X-ray spectral index
$\alpha_{\rm ox}$ in LLAGNs with $10^{-6} \lesssim \lambda \lesssim 10^{-3}$.
We compile from literature a sample of 32 LLAGNs, consisting 18 LINERs and 14
low Eddington ratio Seyfert galaxies, and observe a strong negative $R_{\rm
UV}$--$\alpha_{\rm ox}$ relationship, with large scatter in both $R_{\rm UV}$
and $\alpha_{\rm ox}$. We further demonstrate that this negative correlation,
and the additional two negative relationships reported in literature ($R_{\rm
UV}$--$\lambda$ and $\alpha_{\rm ox}$--$\lambda$ correlations), can be
understood consistently and comprehensively under the truncated accretion--jet
model, the model that has been applied successfully applied to LLAGNs. We argue
that the scatter in the observations are (mainly) due to the spread in the
viscosity parameter $\alpha$ of a hot accretion flow, a parameter that
potentially can serve as a diagnose of the strength and/or configuration of
magnetic fields in accretion flows.
