Proceedings Article | 25 November 1996
KEYWORDS: Solar processes, Sun, Magnetism, Space operations, Coronagraphy, Space telescopes, Telescopes, Magnetosphere, Observatories, Particles
The solar output changes on a variety of timescales, from minutes, to years, to tens of years and even to hundreds of years. The dominant timescale of variation is, of course, the 11-year solar cycle. Observational evidence shows that the physics of solar output variation is strongly tied to changes in the magnetic field, and perhaps the most dramatic manifestation of a constantly changing magnetic field is the Coronal Mass Ejection (CME). On August 5 - 6, 1996 the Second Workshop to discuss missions to observe these phenomena from new vantage points, organized by the authors, was held in Boulder, Colorado at the NOAA Space Environmental Center. The workshop was attended by approximately 20 scientists representing 13 institutions from the United States and Europe. The purpose of the Workshop was to discuss the different concepts for multi- spacecraft observation of the Sun which have been proposed, to develop a list of scientific objectives, and to arrive at a consensus description of a mission to observe the Sun from new vantage points. The fundamental goal of STEREO is to discover how coronal mass ejections start at the Sun and propagate in interplanetary space. The workshop started with the propositions that coronal mass ejections are fundamental manifestations of rapid large-scale change in the global magnetic structure of the Sun, that CME's are a major driver of coronal evolution, and that they may play a major role in the solar dynamo. Workshop participants developed a mission concept that will lead to a comprehensive characterization of CME disturbances through build-up, initiation, launch, and propagation to Earth. It will also build a clear picture of long-term evolution of the corona. Participants in the workshop recommended that STEREO be a joint mission with the European scientific community and that it consist of four spacecraft: `East' at 1 AU near L4, 60 deg from EArth to detect active regions 5 days before they can be seen by terrestrial telescopes. `West' at L5 views the sources of energetic particle events reaching Earth. `Earth Orbiter' to view the Sun, solar plasma and Earth's magnetosphere, and `North-South' in a 1 AU orbit tilted 30 deg from the ecliptic plane to provide measurements of polar fields and high-latitude activity. All spacecraft will carry solar activity imagers (e.g., EUV telescope and white-light coronagraph) and radio burst detectors to support a tomography program. All will carry sensitive polarimeters that will image CME's from 40 solar radii to 1 AU, and all will carry instruments for situ plasma and energetic particle sampling. East and North-South have solar vector magnetographs.
