Foreword [to Special Section on Insights From the Polar Spacecraft

Abstract

The International Solar Terrestrial Physics (ISTP) program [Alexander and Nishida, 1984, p. 1] defined an ambitious goal: to develop a comprehensive, global understanding of the generation and flow of energy from the Sun through the Earth s space environment (geospace) and to define the cause‐and‐effect relationships between the physical processes that link different regions of this dynamic environment. Four ISTP spacecraft were launched to accomplish the objectives of the program, two into the solar wind, Solar and Heliospheric Observatory (SOHO) from the European Space Agency (ESA) [Fleck et al., 1995] and Wind [Russell, 1995] from NASA, and two within the magnetosphere, Geotail from the Institute of Space and Astronautical Science (ISAS) [Terasawa and Kamide, 1994] and Polar from NASA [Russell, 1995]. Within this fleet the Polar spacecraft has had the responsibility for measuring the entry of plasma into the Polar magnetosphere and the geomagnetic tail, the flow of plasma to and from the ionosphere, and the deposition of particle energy in the ionosphere and upper atmosphere [Hoffman et al., 1996]. Because of common science interests, the Polar Science Team looks with anticipation toward coordinated activities with the recently launched four Cluster spacecraft mission by ESA [Escoubet et al., 1997], which will become an integral part of the ISTP program.