Neutrino Magnetic Moment Model and Solar Neutrino Problem

We examine the time variation problem of solar neutrinos in the spin-flavour precession mechanism taking into account the $\nu_e$-$\nu_{\mu}$ mixing. The models with the small and large mixing angle are studied. It shows that the models which realize $m_{\nu_e\nu_e} \sim m_{\nu_{\mu}\nu_{\mu}} \ll m_{\nu_e\nu_{\mu}}$ and $m_{\nu_e\nu_e} \sim m_{\nu_{\mu}\nu_{\mu}} {^>_\sim} m_{\nu_e\nu_{\mu}}$ seem to have preferable time variation features. It is very interesting that the former type of models can give the large magnetic moment to neutrinos and also suppress the radiative mass correction naturally.