Between Sun and Earth Between Sun and Earth: timeline In their own words: Robert Rosner

UCAR at 40 Who We Are Introduction One Planet, One Atmosphere •Between Sun and Earth Measuring and Modeling When Weather Matters Most Spreading the Word Knowledge for All Looking toward the Future UCAR at a Glance List of acronyms

1960s

1965 • Mauna Loa Debut NCAR opens its Mauna Loa Solar Observatory (MLSO). The station provides solar researchers around the world with data from an increasingly sophisticated series of coronameters and other sensors.

1966 • Bolivia Bound A white-light coronal camera developed by Gordon Newkirk is deployed for the first time in a solar eclipse expedition to Bolivia. The instrument is used for almost 30 years to periodically sample the Sun's corona. To avoid atmospheric distortion of the coronal signal, Newkirk and colleagues develop coronagraphs deployed by balloon and later sent into space aboard Skylab (see 1973).

1970 • Mexico Eclipse In their largest expedition to that date, HAO staff travel to San Carlos Yautapec, Mexico, to document the March 7 eclipse. It is one of 13 eclipses profiled by HAO between 1952 and 1998. Three other expeditions are thwarted by cloudiness.

1971 • Radiative Transfer Dimitri Mihalas (top right) joins (from left) Grant Athay, Andrew Skumanich, and Lewis House to complete HAO's "radiative transfer school." Studying both stellar and planetary atmospheres, the group paves the way for present understanding of nonlocal thermodynamic equilibrium (the relation between mass and radiation) and polarized radiative transfer. Its work leads to the measurement of solar-surface magnetic fields by the Advanced Stokes Polarimeter in the 1990s.

1973 • Skylab Skylab, the world's first staffed, orbiting solar observatory, is launched by NASA on May 14. In its nine-month life, Skylab samples the Sun with eight instruments, including NCAR's white-light coronagraph. The project confirms many solar theories and finds some surprises, including frequent ejections of coronal mass on a scale larger than the Sun itself.

1976 • Revisiting Maunder After analyzing a 70-year lull in sunspot observations (1645–1715), John Eddy argues that the lull reflects a true decline in solar output, rather than an absence of reports. The Maunder Minimum (named for pioneering astronomer E.W. Maunder) coincided with a series of severe winters in Europe. Eddy's work helps steer scientists toward a broader recognition of solar variability and its possible influence on climate.

1980 • Solar Max The Solar Maximum Mission satellite is launched, beginning observations that will continue off and on for nearly a decade. An NCAR-built coronagraph-polarimeter collects some 30,000 solar images, as often as once per minute, providing new data on magnetic fields.

1985 • Looking Inside An instrument designed by Timothy Brown collects the first two- dimensional measurements of Doppler shifts created on the Sun's surface by internal oscillations. Data from the Fourier tachometer, built by NCAR and the National Solar Observatory, suggest a complex picture of solar rotation: a core that rotates like a solid body and an outer convection zone that spins at different rates according to latitude.

1985 • Modeling the Outer Reaches The NCAR Thermospheric General Circulation Model carries out its first time-dependent simulation of a solar storm's effects. Developed in the early 1980s by Ray Roble, Cicely Ridley, and Robert Dickinson (now at the Georgia Institute of Technology), this model of the upper atmosphere is continually refined through the 1980s and 1990s. Dozens of university scientists use it to analyze the dynamics and magnetism of the atmosphere at heights from 80 to 500 kilometers (50–300 miles).

1987 • Solar Correlations Harry van Loon (NCAR) and Karin Labitzke (Free University of Berlin) embark on more than a decade of collaboration, studying solar-atmosphere connections. They discover a statistical link between the 11-year solar cycle and conditions in the Arctic stratosphere. This link appears when the Quasi-Biennial Oscillation (QBO) of tropical stratospheric winds is in a particular mode. In the 1990s, van Loon and Labitzke extend the correlations to the Southern Hemisphere and (independently of the QBO) to parts of the summer troposphere.

1994 • Rotation Redux With a new low-frequency, or low-l, instrument deployed at Mauna Loa, Steven Tomczyk and colleagues measure oscillations that penetrate to the Sun's core. The data confirm a thesis formed in the 1980s: the inner two-thirds of the Sun rotates much like a solid body, varying little by depth or latitude.

1995 • Model Blend A landmark union joins two key NCAR models, the Thermosphere/Ionosphere/Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) and version 2 of the Community Climate Model (CCM2). The union evolves by 2000 into a Whole Atmosphere CCM, one of the first that can simulate Earth's atmosphere from top to bottom.

1998 • Caribbean Trek An expedition based in Curacao and Panama gathers both ground-based and airborne observations of an eclipse on February 26. The ground team collects very high resolution coronal images that provide clues to the heating of the corona and the acceleration of the solar wind. Aboard the NSF/NCAR C-130 aircraft, a separate group verifies that a narrow band of infrared emissions from ionized silicon could serve as a powerful indicator of coronal field strength, as predicted by Philip Judge.

1999 • New Solar Tools NCAR completes the Advanced Coronal Observing System (ACOS), a major upgrade of MLSO. Sampling the Sun every three minutes for six hours each day, the ACOS instruments obtain a unique view of solar structures that include coronal mass ejections, erupting prominences, and filaments.

1999 • Planet Search Scientists at San Francisco State University, the Harvard-Smithsonian Center for Astrophysics, the Anglo-Australian Telescope, and NCAR use helioseismologic data to infer for the first time the presence of multiple planets around a Sun-like star, Upsilon Andromeda.