The Science Behind Solar Dynamic Observatory

SDO will help us to understand the how and why of the Sun's magnetic changes. It will determine how the magnetic field is generated and structured, and how the stored magnetic energy is released into the heliosphere and geospace. SDO data and analysis will also help us develop the ability to predict the solar variations that influence life on Earth and humanity's technological systems.

SDO will measure the properties of the Sun and solar activity. There are few types of measurements but many of them will be taken. For example, the surface velocity is measured by HMI. This data can be used for many different studies. One is the surface rotation rate, which must be removed to study the others. After subtracting the rotation, you have the oscillation and convective velocities. The latter look like billows of storm clouds covering the Sun. Hot gas moves outward at the center of the billows and downward at the edges-just like boiling water. By looking at these velocities you can see how sunspots affect the convection zone. By looking at a long sequence of data (more than 30 days), you see the oscillations of the Sun (like the picture). These patterns can be used to look into and through the Sun.

Mission Science Objectives

The scientific goals of the SDO Project are to improve our understanding of seven science questions:
  • What mechanisms drive the quasi-periodic 11-year cycle of solar activity? How is active region magnetic flux synthesized, concentrated, and dispersed across the solar surface?
  • How does magnetic reconnection on small scales reorganize the large-scale field topology and current systems and how significant is it in heating the corona and accelerating the solar wind?
  • Where do the observed variations in the Sun's EUV spectral irradiance arise, and how do they relate to the magnetic activity cycles? What magnetic field configurations lead to the CMEs, filament eruptions, and flares that produce energetic particles and radiation? Can the structure and dynamics of the solar wind near Earth be determined from the magnetic field configuration and atmospheric structure near the solar surface?
  • When will activity occur, and is it possible to make accurate and reliable forecasts of space weather and climate?

Contact: Dwayne C. Brown
Headquarters, Washington