A senior astronomer at the National Solar Observatory has been awarded the Arctowski Medal of the National Academy of Sciences for "for major contributions to understanding the Sun's magnetic fields and its interior structure, and for developing the instrumentation that has made these discoveries possible."

Jack Harvey has been with NSO and its predecessor organizations in Tucson, AZ, since he earned his doctorate in astrogeophysics at the University of Colorado in 1969.

"I've worked on instruments that provide a long baseline of data relating to how the Sun varies and how Earth responds to it," Harvey explained. He started with the original Kitt Peak magnetograph built by Bill Livingston, the first of a series of key instruments that dissect sunlight to measure the strength of magnetic fields, which generate sunspots, flares, coronal mass ejections, and other events that drive space weather. Mapping and tracking magnetism are of paramount importance in understanding solar activity and how it affects Earth

Data from the Kitt Peak magnetographs form a continuous 35-year-long record of changes in solar magnetic activity. Harvey now is project scientist for its replacement, the Vector Spectromagnetograph, which also measures the direction the fields. It is part of NSO's Synoptic Optical Long-term Investigations of the Sun (SOLIS) project.

Harvey also is the instrument scientist for the Global Oscillation Network Group (GONG), a chain of six small, identical telescopes around the world. These monitor up-down pulsations in the solar atmosphere, which scientists translate into models of interior flow and even maps of activity on the far side.

"My role in the initial phase was to worry about how to design and operate instruments for helioseismology," which literally means "shaking Sun," Harvey explained. GONG started as a three-year project and now is entering its 16th year and third round of enhancements, the addition of cameras to observe the Sun in H-alpha light, a deep red color that reveals active regions. "I started my career doing H-alpha patrol work and it looks like I'll end it doing that," he noted. "I'm very proud to be a part of GONG."

Harvey was involved with a GONG predecessor set up five summers at the South Pole where it could observe the Sun for days at a time without interruption. Again, looking at oscillations on the surface revealed what was happening inside.

"We made several basic discoveries," Harvey said. "We figured out that internal rotation is differential, like the surface, throughout the gently convecting layers of the Sun" meaning that the Sun rotates faster at the equator and slower towards the poles. "We also determined that the deeper layers, the so-called radiative zone, rotate rigidly." That is, the middle region, between the core and the convective zone, rotates nearly solidly even though it is a gas. These features, in turn, affect the dynamo that generates the Sun's magnetic fields.

Harvey also serves on several national review panels and was a co-editor of the journal Solar Physics.

The Arctowski Medal is awarded for outstanding contributions to the study of solar physics and solar-terrestrial relationships. It includes a $20,000 prize, as well as $60,000 to an institution of the recipient's choice. Harvey and 12 other NAS awardees will be honored in a ceremony on May 1 during the Academy's annual meeting in Washington, DC.