Solar Synoptic Maps as a Means to Study the Global Sun

Solar synoptic maps (often referred as Carrington maps) are maps of the Sun in latitude versus longitude built by merging together solar observations taken during one solar rotation. They are an efficient method to represent the Sun as it appears during a rotation yielding a global view of solar structures, such as active regions, coronal holes, and helmet streamers. They provide a clear and effective way to study evolutionary patterns on the Sun and to compare different solar datasets over long periods of time. Because of their ability to display a large number of data in a concise way, solar synoptic maps have been popular for many years. The availability of modern instruments (both in space and on the ground) that can provide consistent and calibrated measurements for many years has renewed the interest in this data format. We believe there is a need for the solar-terrestrial community to agree on a standard format for synoptic maps of the Sun. Such a format should be discussed and defined in parallel with the effort of the Solar Virtual Observatory. At the High Altitude Observatory (HAO), we are developing a public database of solar synoptic maps for the solar observations made at Mauna Loa Solar Observatory (MLSO). The database will include observations of the solar corona in visible light and of the solar chromosphere in the HeI 1083nm and Hα lines. In this paper, we present examples of MLSO solar synoptic maps and compare them with other solar synoptic maps to illustrate the scientific use and flexibility of this data format.