The neutrino magnetic moment and time variations of the solar neutrino flux

The present status of the neutrino magnetic moment solutions of the solar neutrino problem is summarized. After a brief review of the basics of the neutrino spin and spin-flavor precession I discuss the experimental data and show how the neutrino resonant spin-flavor precession (RSFP) mechanism can naturally account for sizeable time variations in the Homestake signal and no observable time variations in the Kamiokande and gallium experiments. Fits of the existing data and predictions for the forthcoming solar neutrino experiments are also discussed. In the last section I summarize the objections to the RSFP mechanism that are frequently put forward and comment on them.