10.5 days in the life of the Sun

Solar and Heliosperic Observatory

SoHO is a spacecraft launched in 1995 that has been observing the Sun ever since. It is located in a halo orbit around the Earth-Sun L1 Lagrange point, which allows the satellite to study the Sun 24 hours a day, 365 days a year without interruptions. When observing from space our images do not get disturbed by the Earth's atmosphere. The EIT instrument on board SoHO takes full disk images of the Sun and also subfields of particular regions, and is able to observe the transition region and inner corona in 4 selected filters in extreme ultraviolet (EUV) wavelengths. This movie spans 10 days and 13 hours in the life of the Sun (from June 2 till June 12, 2003) and is recorded in the Fe XII emission line at 195 Å. Fe XII (which is eleven-times ionized iron) is common at temperatures of 1.5 million degrees. Almost the full disk is visible here.

The Sun rotates at a speed that varies from 25 days at the equator to 36 days at the pole. When different latitudes rotate at different periods it is called differential rotation, and that is exactly what happens in the Sun. Since solar activity is embedded or attached to the surface, it rotates together with the Sun. If we observe the Sun for long enough like in this movie, we will see that active regions cross the disk from left to right following the rotation of the Sun. In the movie we can see one active region after the other appearing from the left limb and crossing the Sun until they reach the right limb. Multiple flares occur in the leading active region as well as in other trailing active regions. Enormous bright loops interconnect magnetic patches of different polarities, and we can see that the configuration of the magnetic field lines changes continuously.

This kind of observations allow scientists to study the evolution in time of the solar magnetic fields, their different configurations, the evolution of flows, the life of sunspots, etc.

To download the movie, click HERE

Movie credit: SOHO (ESA, NASA)

Text credit: Ada Ortiz (ITA, University of Oslo)