AN ASTROPHYSICAL LABORATORY IN OUR OWN BACKYARD

Plasmas exist everywhere in the universe—in the interiors of stars, in stellar winds, in the bizarre and highly energetic phenomena of stellar and galactic jets, and in the magnetospheres and ionospheres expected to surround extrasolar planets. It is only in our solar system, however, that the fundamental physical processes that occur in plasmas can be studied directly and in detail, through in situ measurements from spacecraft and sustained, high-resolution imaging from both space-based and ground-based observatories. The solar system thus serves as a “laboratory” for the investigation of processes common to all astrophysical plasmas.

At the center of this laboratory sits our Sun, a “cool” (6,000 K) main-sequence star with a hot (1,000,000 K) corona. The detailed knowledge that scientists obtain from helioseismic studies of the Sun’s interior, high-resolution imaging of the solar surface and corona, and in situ measurements of the solar wind and the IMF is being applied to the study of other magnetically active stars, with their hot x-ray-emitting

Magnetic reconnection may be responsible for accelerating cosmic rays in the lobes of giant radio galaxies such as NVSS 2146+82, a hypothesis supported by theoretical studies of reconnection in solar system plasmas.



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Understanding the Sun and Solar System Plasmas: Future Directions in Solar and Space Physics AN ASTROPHYSICAL LABORATORY IN OUR OWN BACKYARD Plasmas exist everywhere in the universe—in the interiors of stars, in stellar winds, in the bizarre and highly energetic phenomena of stellar and galactic jets, and in the magnetospheres and ionospheres expected to surround extrasolar planets. It is only in our solar system, however, that the fundamental physical processes that occur in plasmas can be studied directly and in detail, through in situ measurements from spacecraft and sustained, high-resolution imaging from both space-based and ground-based observatories. The solar system thus serves as a “laboratory” for the investigation of processes common to all astrophysical plasmas. At the center of this laboratory sits our Sun, a “cool” (6,000 K) main-sequence star with a hot (1,000,000 K) corona. The detailed knowledge that scientists obtain from helioseismic studies of the Sun’s interior, high-resolution imaging of the solar surface and corona, and in situ measurements of the solar wind and the IMF is being applied to the study of other magnetically active stars, with their hot x-ray-emitting Magnetic reconnection may be responsible for accelerating cosmic rays in the lobes of giant radio galaxies such as NVSS 2146+82, a hypothesis supported by theoretical studies of reconnection in solar system plasmas.

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Understanding the Sun and Solar System Plasmas: Future Directions in Solar and Space Physics This computer simulation shows the intense currents generated by electrons where oppositely directed magnetic fields reconnect or annihilate. Magnetospheric multiscale will provide observational tests of our models and theories of reconnection. coronas, stellar winds, and enveloping “asterospheres.” Solar Probe (originally known as Starprobe) is thus in a very real sense an astrophysics as well as a solar physics mission. By uncovering the mechanisms by which the Sun’s corona is heated and the solar wind is accelerated, Solar Probe will yield insights into coronal heating and stellar wind acceleration at other low-mass main-sequence stars in our galaxy. Earth’s magnetosphere affords a unique laboratory for the investigation of magnetic reconnection, a process that has been invoked to explain a number of astrophysical phenomena, from solar flares and CMEs, to accretion disk flares, to the acceleration of electrons at velocities close to the speed of light in the lobes of giant radio galaxies. The Magnetospheric Multiscale (MMS) mission is specifically designed to probe reconnection sites in the magnetosphere in order to unravel the poorly understood microphysics involved in the rapid conversion of magnetic energy to particle kinetic energy. The improved understanding of this fundamental plasma process which the MMS mission is expected to yield will be of invaluable benefit to scientists seeking to understand the role of reconnection in other plasma environments, both within the solar system and in remote astrophysical settings. FUNDAMENTAL PROCESSES IN ASTROPHYSICAL PLASMAS The study of solar system plasmas has made substantial contributions to our understanding of such universal plasma processes as magnetic reconnection, magnetohydrodynamic turbulence, energetic particle acceleration, and the formation of collisionless shocks. With the appropriate scaling, lessons learned in our solar system can be applied to distant astrophysical plasmas that can only be studied remotely.