with \`\`very strong” magnetic fields. The standard model of particle physics suggested that the magnetic moment of neutrinos is smaller than the order of $\sim 10^{-18} \mu_B$, where $\mu_B=e \hbar/2 m_e c$ is Bohr magnetons, $e$ is the charge of an electron, and $m_e$ is electron mass (review in [@pu92]). However, particle theories beyond the standard model have suggested that the upper limit of the neutrino magnetic moment is up to $\sim 10^{-10} \mu_B$ (e.g., [@fy87]) and grand unified theory permits such a \`\`large” magnetic moment of neutrinos. Therefore, if evidence for a neutrino magnetic moment is found, it will become a quite new trace of particle physics beyond the standard model. Neutrino experiments also have constrained the upper limit of neutrino magnetic moment. Recently, the TEXONO experiment deduced the upper limit $\mu_{\bar{\nu}_e} < 7.4 \times 10^{-11} \mu_B$ from $\bar{\nu}_e$ detection [@wo07]. The GEMMA experiment obtained a stronger constraint $\mu_{\nu_e} < 5.8 \times 10^{-11} \mu_B$ at 90 % C.L. [@be07]. Astrophysical limit has been evaluated from plasmon decays in stars in globular clusters as $\mu_\nu < 3 \times 10^{-12} \mu_B$ [@ra99].

If neutrinos are Majorana particles and have a finite magnetic moment, they have only transition magnetic moment. In this 