How a Magnetograph at L5 would Improve the Space Weather Prediction Capabilities.

Knowledge of the magnetic field in solar photosphere plays essential role in modern space weather forecast. Thus, for example, synoptic maps of radial magnetic field are used as input for WSA-ENLIL model to derive the properties of solar wind near the Earth and elsewhere in the solar system. Topology of magnetic field around the source regions of flares and CMEs offers important clues about orientation of magnetic field in interplanetary magnetic clouds and ejecta, and the information about large-scale magnetic connectivity in solar corona brings better understanding of remote triggering solar eruptions. Here I will review the benefits of having magnetograph observations from two viewing points: one at Earth-viewing angle and the other at L5, and I will discuss the type of magnetographs that can be considered for a future L5 mission.