Polar, Wind and Geotail:
Project Overview

"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." - Alexander and Nishida, 1984

In the 1990s, collaborations between NASA, the European Space Agency (ESA), and the Institute of Space and Astronuatical Science (ISAS) of Japan resulted in the International Solar-Terrestrial Physics (ISTP) Science Initiative. Polar, Wind and Geotail are a part of this initiative, combining resources and scientific communities to obtain coordinated, simultaneous investigations of the Sun-Earth space environment over an extended period of time.

Objectives for 2002-2006:

We will extend the systems-science approach, describing the dynamic processes associated with the decline of the solar cycle. This will be based on observable quantities and be demonstrable through realistic physical 3-D global models of the magnetosphere system.

We will understand the dynamic processes associated with the equatorial region of 2-30 RE. We will quantify the relative influences that solar and terrestrial source plasamas have on dynamic equatorial processes. We will determine the equatorial storm plasma injection and loss as a function of solar input. And, we will understand the connection between radiation belt time variations and their direct connection with solar variability.

We will investigate the global consequences of magnetic reconnection. We expect to gain an understanding of substorm onset and instability processes associated with the inner magnetosphere. We will establish which are the controlling reconnection processes and quantify their relative importance for system dynamics. Merging versus current disruption? Component versus antiparallel merging? Which are controllers, which act as regulators? Are the fundamental processes different on the dayside, the flanks and in the tail?

We will quantify the 3-D structure and evolution of large-scale interplanetary configurations and their interaction with the magnetosphere. The evolution and dynamics of large scale interplanetary structures such as corotating interaction regions (CIRS), magnetic clouds, shocks, flux ropes, etc. will be characterised using 3-point heliosphere configurations.

Accomplishments:

Our science teams have made many discoveries significantly changing the direction of Sun-Earth Connection physics, among these are:

1. The deep magnetotail does not hold the key to magnetosphere dynamics. The “action” appears to be much closer to Earth although we are still working to determine exactly where and how.

2. Collisionless reconnection is “the” most important energy transfer process between the solar wind and magnetosphere and is more widespread than first appreciated.

3. The terrestrial plasma source mass quickly loads the outer magnetosphere after solar events and thereby may be a catalyst or driver, rather than a consequence, of magnetospheric dynamics.

4. Shock fronts in the solar wind can be so steeply angled that they reach Earth before they are observed at L1. This is currently causing many uncertainties in the reliable modeling of the geospace response.

5. Different phases of a single solar cycle produce widely varying solar wind input conditions to the magnetosphere and, in turn, a widely varying cycle of dynamic response within the magnetosphere.

The future resides with answering new science questions that have come from these discoveries. We invite you to visit the home pages of each of these missions to learn more.