Yesterday I blogged about next Tuesday's launch of the Solar Dynamics Observatory (SDO), which I'll be attending as a Twitter correspondent, and the spate of educational events and tweetups around the world that will accompany the launch. So why is this mission important enough to garner all this attention, and for NASA to deem it the crown jewel of its solar science space fleet?

THe SDO will image the Sun at a far greater resolution than previous missions, and take images and measurements at much shorter intervals. This will let scientists look at short-term changes in the Sun's brightness, appearance, and magnetic field in unprecedented detail, and should allow them to better understand the processes that drive solar activity and produce the "space weather" that can, upon reaching our world, cause geomagnetic storms that endanger astronauts and satellites, disrupt radio communications, and cause power surges or blackouts.

The SDO is the first mission in the space agency's "Living with a Star" program, which seeks to help us better understand the nature of solar activity and variability, and how it can ultimately impact Earth. I briefly spoke to "Living With a Star" lead program scientist Madhulika Guhathakurta before she departed for Florida for the SDO launch. She characterized the Sun as an ordinary magnetic variable star.

The Sun's variability is intimately tied to its magnetism, which is driven by our star's rotation as well as internal convection. But while Earth's magnetic field is dipolar, similar to a bar magnet, the Sun's is spread among a number of dipolar pairs of patches that line up like mini bar magnets. These so-called active regions are often are marked by sunspots. The number of patches waxes and wanes with the quasi-regular, approximately 11-year cycle of solar activity that's often called the sunspot cycle.

The Sun is generally overlooked as a variable star, as its fluctuations--at least in visible light--are relatively minor, with its brightness varying by no more than about 1 percent. But what may seem to us to be an unchanging orb is revealed to astronomers as a far more active star.

Galileo first drew sunspots in 1612, although Chinese and Greek observers had spotted naked-eye sunspots many centuries earlier. In 1859 British astronomer Richard Carrington observed an intense brightening near a sunspot group, a rare white-light solar flare.The following day, a geomagnetic storm disrupted telegraph communications, and Carrington correctly surmised a connection between these two events. Solar flares emit X rays and ultraviolet radiation--which can put astronauts and satellites in danger--as well as radio waves; all three can combine to wreak havoc on radio communication.

We live within the Sun's extended atmosphere. The solar wind, a continuous stream of charged particles flowing from the Sun, interacts with Earth's magnetic field. Sometimes violent outbursts from the Sun can release a volley of high-energy particles.

Missions such as the Solar and Heliospheric Observatory (SOHO) employ an instrument called a coronagraph. In effect, it creates an artificial solar eclipse, revealing the Sun's corona, an outer atmosphere of tenuous yet superheated, ionized plasma. At intervals ranging from several times a week at sunspot minimum to several times daily at solar max, coronagraph images reveal coronal mass ejections (CMEs), huge gouts of plasma with embedded magnetic fields erupting from the solar corona to stream into interplanetary space (see the image above).

If the CME happens to be pointed towards Earth, it will reach our world 1 to 5 days later. Its interaction with Earth's magnetic field can cause auroras, disrupt radio communications, cause power surges and blackouts, and damage satellites. The STEREO mission, which consists of twin spacecraft orbiting independently around the Sun yet working together, was designed in large measure to triangulate CMEs so we'd know in advance if they'd hit us or pass harmlessly to the side.

To help us better understand how the Sun's magnetic activity relates to the development of sunspots, solar flares, CMEs, and other features, the SDO will provide near-continuous coverage of multiple areas of the Sun--interior, photosphere, and corona. To this end, it carries a suite of three instruments: the Helioseismic Magnetic Imager (HMI), the Atmospheric Imaging Assembly (AIA), and the Extreme Ultraviolet Variability Experiment (EVE).

Think 1080p HD is cool? The SDO's Atmospheric Imaging Assembly (AIA) will do far better, recording the Sun in 4,096- by 4,096-pixel glory, comparable to IMAX resolution. AIA is a battery of four telescopes that will image the Sun's photosphere (surface) and corona (atmosphere) in 10 wavelengths, out to a distance of 1.3 solar diameters. The bulk of the SDO's data will come from the AIA, which will produce a new image every 10 seconds.

In comparison, the twin STEREO Sun-watching spacecraft generate full-disk solar images every 3 minutes, while the Solar and Heliospheric Observatory (SOHO) is showing its age, taking a pokey 12 minutes to produce each 1,024 by 1,024 image. This improvement in "time resolution", coupled with the increased pixel count, will allow SDO to give us a much better look at the rapid development of the Sun's transient features.

The EVE measures the Sun's brightness over a range of extreme ultraviolet (EUV) wavelengths. EUV radiation is completely absorbed by our atmosphere, but it can be quite harmful to astronauts and spaceborne electronics alike, and has brought satellites out of orbit. While previous missions measure the Sun's EUV energy every 90 minutes, SDO will measure it every 10 seconds. And while the EVE is measuring the Sun's radiant energy in the extreme ultraviolet, AIA will take images at the same wavelengths to identify the features associated with the EUV radiation.

The HMI seeks to determine the interior sources and mechanisms of solar variability relate to surface magnetic field and activity. It will measure the motion of the solar photosphere (the Sun's visible surface) to study solar oscillations (the photosphere rises and falls with about a 5-minute period) and better understand what's going on in the Sun's interior, a technique known as helioseismology. At the same time, the HMI will study the photosphere's magnetic field by measuring the polarization in the Sun's spectral lines.

The spacecraft will send 150 megabits of data back to Earth every second. Unlike previous solar missions, SDO doesn't cache its data. The satellite will be in constant line-of-sight contact with two dedicated 18-meter radio dish antennas in New Mexico, to which it will beam its data.

The SDO's main scientific goals include a better understanding of the 11-year cycle of solar activity; identifying the role of the Sun's magnetic field in delivering energy to the solar atmosphere; studying how the outer regions of the Sun's atmosphere evolve over space and time; and observing the levels of solar output (such as EUV) that can effect the atmospheres of Earth and other worlds. With the SDO's powerful and focused set of tools producing solar images at a higher resolution and greater frequency than ever before, it is bound to revolutionize our understanding of the Sun, that familiar yet enigmatic star vital to our survival. And the spacecraft should produce some pretty cool IMAX-res movies of it as well.