A schematic diagram (not to scale) showing the connected Sun-Earth system. Photo courtesy of NASA/JPL/Caltech      A Great Observatory    Earth's space environment traditionally has been explored as a set of independent parts - the interplanetary region, the magnetosphere, the ionosphere, and the upper atmosphere. Past science missions have advanced the understanding of these geospace components as individual parts. But even from the earliest space-based studies, scientists have known that these components are highly interactive. To understand the system as a whole, there was a need for comprehensive, quantitative study of the energy chain from the Sun's interior to Earth's atmosphere.    LASP has been strongly involved in the International Solar Terrestrial Physics (ISTP) program, which has coordinated the activities of an armada of spacecraft, ground-based observatories, and theoretical modeling centers. This assemblage represents a "great observatory" for space physics, providing both a global view of the Sun-Earth system and a mgnificently detailed view of its physical processes. A Laboratory in Rocket's Reach    Gases of charged particles (plasmas) fill much of the known cosmos, and the interactions of such charged gases determine the behavior of matter within our solar-terrestrial system. But the spatial, temporal, and density scales we can explore in space are much different from those produced in earthbound laboratories. Therefore, our solar-terrestrial system - which is composed of dynamic and complex systems of moving particles, magnetic fields, and electrical currents - serves as a nearby example of what probably happens throughout our whole universe. It is a unique laboratory for investigating the natural processes that occur in nearly all astrophysics and it is a laboratory that we can reach relatively easily with rockets and spacecraft. A Picture Large and Small    In the early years of LASP, the laboratory was involved in the Orbiting Solar Observatory (OSO) missions to explore and understand the Sun. Later programs such as the Solar Mesosphere Explorer (SME) studied the      The Polar and Wind satellites of the International Solar Terrestrial Physics program in orbit around the Earth. Photo courtesy of NASA/JPL/Caltech interation of the Sun with Earth's upper atmosphere. The present international space physics program represents a multi-billion dollar investment toward understanding the Sun-Earth system in unprecedented scope and detail. When these spacecraft are linked with ground-based elements and theoretical modeling tools, the combined resources provide not only a telescopic view, but also a microscopic view. This coupling of microscopic and telescopic views is crucial to understanding the physical processes - such as magnetic reconnection and partice accelleration - that drive our solar system and our near-Earth environment. Disturbances in our Skies    The Sun reaches maximum activity every 11 years or so. As it reaches the peak it expels with increasing frequency huge magnetic clouds of material (called coronal mass ejections, or CMEs) that can move outward at speeds approaching 2,000 kilometers per second.    The shock waves preceding such clouds can accelerate particles to tremendous energies - sometimes more that 100 million electron volts (meV). If the CMEs and the shock waves they produce strike Earth's magnetosphere, they can cause violent geomagnetic storms that can disturb power systems, communication links, and the constellations of spacecraft of which society inceasingly relies.    As our appreciation of the Sun-Earth system has grown more sophisticated, so too has our technology. Today, a tangled web of electrical and communication links has been woven across Earth's surface, while fleets of spacecraft work in the electric space above us. By using electromagnetic techniques to enhance communication, navigation, reconnaissance, and weather prediction that generally make the world safer, we have also put ourselves in danger. Every tool and gadget that relies on radio waves, conducting wires, and sensitive transistors and processing chips can be affected by disturbances in the solar-terrestrial system. Power and Precision to Study our Sun    Never before have we had such a complete set of missions with which to study the Sun-Earth system. And never before have we had tools of such power and precision to study our most important star - the Sun - and our most important planet - the Earth. We have a chance to study all aspects of the Sun and its consequent effects on near-Earth space. ISTP has already reaped a rich scientific harvest. Future projects such as the Magnetospheric Multiscale (MMS) mission should provide even more opportunities to pursue a new, profound understanding of the Sun and the Earth and interplanetary space between them. Using the MMS constellation we will be able to study magnetic reconnection, particle acceleration, and plasma turbulence throughout many of the key regions in Earth's neighborhood. Related LASP Projects: FAST: Fast Auroral Snapshop Satellite IMEX: Inner Magnetospheric Explorer ISTP: International Solar Terrestrial Physics Radio Tomography Imaging SAMPEX: The Solar, Anomalous, and Magnetospheric Particle Explorer STEREO: The Solar-Terrestrial Relations Observatory

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