The Sun to the Earth -- and Beyond A Decadal Research Strategy in Solar and Space Physics (2003) / Chapter Skim
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4. Connections Between Solar and Space Physics and Other Disciplines
4. Connections Between Solar and Space Physics and Other Disciplines
Pages 93-110
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From page 93... ...
Solar physics and space physics share with laboratory plasma physics and astrophysics an interest in a variety of phenomena, including magnetic dynamo action, magnetic reconnection, turbulence, collisionless shocks, energetic particle transport and acceleration, and plasma instabilities. Understanding developed in one of these fields is thus in principle applicable to the others, and productive cross-fertilization between disciplines has occurred in a number of instances, for the reason that any fundamental principle, regardless of where it is discovered, is applicable throughout the universe.
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From page 94... ...
Finally, the committee considers briefly the role played by theoretical and laboratory studies of atomic and molecular processes in solar and space physics research. LABORATORY PLASMA PHYSICS Laboratory plasma experiments represent a valuable tool for advancing our understanding of the physical processes underlying phenomena observed in both solar system plasmas and remote astrophysical systems.
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From page 95... ...
Dynamo Experiments In a dynamo, the motions of an electrically conducting fluid generate magnetic fields, thereby converting kinetic energy of motion into magnetic energy. Magnetic dynamos are critical elements of both solar and space 95
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From page 96... ...
. This process is called magnetic reconnection or merging, and it is thought to be the main means by which magnetic fields in space plasmas change the way they are linked with one another.
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From page 97... ...
Here, as in the reconnection studies, the laboratory plasma is more dissipative than are most typical space plasmas, but the laboratory experiments demonstrate and explore the physical effects that are relevant to the physical systems of interest to solar and space physics. Progress has been made in identifying the natural oscillations of the system, referred to as eigenmodes, observing the decay of excited eigenmodes, and measuring the effects of turbulence on electrical conductivity.
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From page 98... ...
Other plasma physical phenomena that have been the subjects of recent laboratory experiments include waves in dusty plasmas and solar prominences. Recommendation: In collaboration with other interested agencies, the NSF and NASA should take the lead in initiating a program in laboratory plasma science that can provide new understanding of fundamental processes important to solar and space physics.
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From page 99... ...
The solar system thus represents a laboratory for astrophysical studies in which fundamental plasma physical processes such as reconnection, turbulence, particle acceleration, and shocks can be investigated at both the micro- and macroscales and in ways not possible through numerical simulations or laboratory plasma experiments.4 The physical understanding derived from observational studies of solar system plasmas provides a basis for theoretical extrapolation to more extreme astrophysical systems. Fruitful cross-fertilization between solar-system plasma physics and astrophysics is particularly well exemplified in the study of collisionless shocks, magnetohydrodynamic turbulence, and magnetic reconnection.
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From page 100... ...
These observations have stimulated an ongoing effort to develop theoretical treatments of MH D turbulence appropriate to the two similar systems. Although this effort relies heavily on studies of the solar wind as the more fully characterized of the two plasmas, it is strongly interdisciplinary in character, drawing on insights from theoretical plasma physics and laboratory plasma physics as well as on observational and theoretical studies.
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From page 101... ...
Flux removal by reconnection has also been proposed as relevant to the production of magnetic viscosity in accretion disks. Magnetic reconnection is thought to be responsible for flarelike releases of energy in interactions between neutron star magnetospheres and accretion disk magnetic fields as well as for flares occurring in accretion disk coronae, and the solar flare model of reconnection has been applied to flares from dwarf stars, binaries, and T Tauri stars.
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From page 102... ...
The observed turbulence is thought to enhance heating of the interplanetary medium, and it is responsible for scattering and transport of cosmic rays originating from both inside and outside the heliosphere. Solar wind turbulence also provides important clues about the nature of the lower solar corona.
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From page 103... ...
. By including pickup ions, the turbulence model captures the temperature increase from 20 AU to 60 AU, showing highly non-adiabatic behavior.
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From page 104... ...
Helioseismology has confirmed the theoretical model of the solar interior and revealed complex, three-dimensional flow patterns within the convective zone, presumably responsible for generating and sustaining the Sun's magnetic fields. Precision confirmation of the theoretical model of the Sun gives us confidence in the theoretical models of the interior structure, dynamics, and evolution of other stars (see sidebar, "The Solar Laboratory".
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From page 105... ...
. The precision is now such that we can use the hello-seismic frequencies to test individual nuclear cross sections of the pep chain, which are the source of the Sun's energy.
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From page 106... ...
Sputtering not only plays a role in atmospheric loss but also, through the sputtering of surfaces, produces tenuous atmospheres such as the recently discovered oxygen exospheres about the Jovian moons Europa and Ganymede. Sputtering of the surface of Mercury by solar wind particles probably contributes, along with other processes such as photodesorption, to the creation of Mercury's variable sodium exosphere.
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From page 107... ...
Ionization produced by galactic cosmic rays could have an influence on the nucleation of cloud particles. An apparent correlation between globally averaged low cloud cover and the cosmic ray flux over solar cycle 22 has been adduced in support of this mechanism.
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From page 108... ...
The interpretation of observations of auroral and dayglow emissions from the outer planets requires accurate excitation and emission cross sections of molecular hydrogen. Accurate modeling of complex processes such as EUV and collisional ionization, recombination, charge exchange, and electron-stripping of high-energy particles is essential for interpreting the ionic charge state and elemental composition of the solar wind.
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From page 109... ...
Fortunately, a number of new laboratory investigations have recently been i n itiated i n th is area. Recommendation: The NSF and NASA should take the lead and other interested agencies should collaborate in supporting, via the proposal and funding processes, increased interactions between reseachers in solar and space physics and those in allied fields such as atomic and molecular physics, laboratory fusion physics, atmospheric science, and astrophysics.
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From page 110... ...
6. In its 1995 report, the Panel on Opportunities in Plasma Science identified MHD turbulence as one of the outstanding problems in plasma astrophysics (NRC, Plasma Science, 1995, p.
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