Long-Term Solar-Terrestrial Data Sets and Their Value

Abstract

Synoptic, long-term observational programmes provide a wide diversity of information on the solar-terrestrial environment. Such data sets are particularly valuable in certain locations, on the ground, or in space. Further, such data sets are necessary for identifying the baseline from which anthropogenic changes may occur, for characterising transient events, for placing the results of short-term experiments in context, and also for carrying out statistical analyses. Results for all of these four examples can be interpreted according to present understanding of the physics of solar-terrestrial phenomena. Inadequacies are identified and understanding is thereby improved. New hypotheses are put forward and tested; new modelling schemes and new observational techniques are devised.
Some examples are presented, dealing with different physical parameters of solar, interplanetary, magnetospheric, ionospheric, thermospheric and geomagnetic phenomena. Considerations of mass, momentum and energy transfer across the magnetopause, and of energy dissipation in the polar, auroral and midlatitude upper atmosphere are emphasised, on time scales ranging from a few minutes to a century. Such studies are essential for the success of the Solar Terrestrial Energy Programme, STEP, the research aspects of which are underpinned by synoptic programmes. They will open the door to more successful predictions of the solar-terrestrial environment, an ever-developing requirement for mankind at the end of the twentieth century.