Author name code: parker ADS astronomy entries on 2022-09-14 author:"Parker, Eugene N." ------------------------------------------------------------------------ Title: Exploring the innermost solar atmosphere Authors: Parker, Eugene N. Bibcode: 2020NatAs...4...19P Altcode: 2019NatAs.tmp....6P The Parker Solar Probe spacecraft completed the first two of its 24 scheduled orbits around the Sun on 18 June 2019, making history by flying halfway between Mercury and the Sun. Title: The FIELDS Instrument Suite for Solar Probe Plus. Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients Authors: Bale, S. D.; Goetz, K.; Harvey, P. R.; Turin, P.; Bonnell, J. W.; Dudok de Wit, T.; Ergun, R. E.; MacDowall, R. J.; Pulupa, M.; Andre, M.; Bolton, M.; Bougeret, J. -L.; Bowen, T. A.; Burgess, D.; Cattell, C. A.; Chandran, B. D. G.; Chaston, C. C.; Chen, C. H. K.; Choi, M. K.; Connerney, J. E.; Cranmer, S.; Diaz-Aguado, M.; Donakowski, W.; Drake, J. F.; Farrell, W. M.; Fergeau, P.; Fermin, J.; Fischer, J.; Fox, N.; Glaser, D.; Goldstein, M.; Gordon, D.; Hanson, E.; Harris, S. E.; Hayes, L. M.; Hinze, J. J.; Hollweg, J. V.; Horbury, T. S.; Howard, R. A.; Hoxie, V.; Jannet, G.; Karlsson, M.; Kasper, J. C.; Kellogg, P. J.; Kien, M.; Klimchuk, J. A.; Krasnoselskikh, V. V.; Krucker, S.; Lynch, J. J.; Maksimovic, M.; Malaspina, D. M.; Marker, S.; Martin, P.; Martinez-Oliveros, J.; McCauley, J.; McComas, D. J.; McDonald, T.; Meyer-Vernet, N.; Moncuquet, M.; Monson, S. J.; Mozer, F. S.; Murphy, S. D.; Odom, J.; Oliverson, R.; Olson, J.; Parker, E. N.; Pankow, D.; Phan, T.; Quataert, E.; Quinn, T.; Ruplin, S. W.; Salem, C.; Seitz, D.; Sheppard, D. A.; Siy, A.; Stevens, K.; Summers, D.; Szabo, A.; Timofeeva, M.; Vaivads, A.; Velli, M.; Yehle, A.; Werthimer, D.; Wygant, J. R. Bibcode: 2016SSRv..204...49B Altcode: 2016SSRv..tmp...16B NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products. Title: Fundamental Concepts Associated with Magnetic Reconnection Authors: Gonzalez, W. D.; Parker, E. N.; Mozer, F. S.; Vasyliūnas, V. M.; Pritchett, P. L.; Karimabadi, H.; Cassak, P. A.; Scudder, J. D.; Yamada, M.; Kulsrud, R. M.; Koga, D. Bibcode: 2016ASSL..427....1G Altcode: The chapter starts with a discussion about the importance of the concept of magnetic field lines in space plasmas and magnetic reconnection, followed by presentations on: (a) the meaning and validity of empirical constructs related with magnetic reconnection research, such as: "moving" magnetic field lines, "frozen-in" condition and "diffusion region" of reconnection; and (b) experimental evidence of the diffusion region and related energetics. Next, aims to link external (MHD) with internal (non-MHD) regions of reconnection are discussed in association with the so-called "Axford conjecture", followed by short presentations on: (a) global equilibria in reconnection; and (b) the role of the separatrices in global aspects of reconnection. In the last section, we present additional discussion about the concept of "diffusion region" and about the two fundamental questions associated with magnetic reconnection reviewed in this chapter. Title: Rapid Reconnection and Field Line Topology Authors: Parker, E. N.; Rappazzo, A. F. Bibcode: 2016ASSL..427..181P Altcode: Rapid reconnection of magnetic fields arises where the magnetic stresses push the plasma and field so as to increase the field gradient without limit. The intent of the present writing is to show the larger topological context in which this commonly occurs. Consider an interlaced field line topology as commonly occurs in the bipolar magnetic regions on the Sun. A simple model is constructed starting with a strong uniform magnetic field B 0 in the z-direction through an infinitely conducting fluid from the end plate z = 0 to z = L with the field lines tied at both end plates. Field line interlacing is introduced by smooth continuous random turbulent mixing of the footpoints at the end plates. This configuration is well suited to be modeled with the reduced magnetohydrodynamic (MHD) equations, with the equilibria given by the solutions of the 2D vorticity equation in this case. The set of continuous solutions to the "vorticity" equation have greatly restricted topologies, so almost all interlaced field topologies do not have continuous solutions. That infinite set represents the "weak" solutions of the vorticity equation, wherein there are surfaces of tangential discontinuity (current sheets) in the field dividing regions of smooth continuous field. It follows then that current sheets are to be found throughout interlaced fields, providing potential sites for rapid reconnection. That is to say, rapid reconnection and nanoflaring are expected throughout the bipolar magnetic fields in the solar corona, providing substantial heating to the ambient gas. Numerical simulations provide a direct illustration of the process, showing that current sheets thin on fast ideal Alfvén timescales down to the smallest numerically resolved scales. The asymmetric structure of the equilibria and the interlacing threshold for the onset of singularities are discussed. Current sheet formation and dynamics are further analyzed with dissipative and ideal numerical simulations. Title: Magnetic Reconnection Authors: Gonzalez, Walter; Parker, Eugene Bibcode: 2016ASSL..427.....G Altcode: No abstract at ADS Title: Prospects and Limitations of Chemical and Isotopic Groundwater Monitoring to Assess the Potential Environmental Impacts of Unconventional Oil and Gas Development Authors: Mayer, B.; Humez, P.; Becker, V.; Nightingale, M.; Ing, J.; Kingston, A.; Clarkson, C.; Cahill, A.; Parker, E.; Cherry, J.; Millot, R.; Kloppmann, W.; Osadetz, K.; Lawton, D. Bibcode: 2015PrEPS..13..320M Altcode: No abstract at ADS Title: Reminiscing my sixty year pursuit of the physics of the Sun and the Galaxy Authors: Parker, Eugene N. Bibcode: 2014RAA....14....1P Altcode: Reminiscing begins with childhood and passes on to student days through graduate school and the first real contact with research. Then early academic positions and stumbling efforts to pursue my ideas. The first significant progress came as a research associate with Prof. W. M. Elsasser at the University of Utah, beginning with an introduction to magnetohydrodynamics and the generation of the geomagnetic field through induction in the liquid metal core of Earth. A move to the University of Chicago to work with Prof. J. A. Simpson, on the implications of cosmic ray variations and interplanetary magnetic fields, led to the theory of coronal expansion and the solar wind and then to exploring the dynamical effects of cosmic rays on the galactic magnetic field. Spontaneous current sheets and intrinsic rapid reconnection in interlaced magnetic field line topologies were the next big project, leading up to retirement. Finally, it is a pleasure to recall my many associates, whose fresh thinking helped stimulate the daily research activities. Title: Current Sheets Formation in Tangled Coronal Magnetic Fields Authors: Rappazzo, A. F.; Parker, E. N. Bibcode: 2013ApJ...773L...2R Altcode: 2013arXiv1306.6634R We investigate the dynamical evolution of magnetic fields in closed regions of solar and stellar coronae. To understand under which conditions current sheets form, we examine dissipative and ideal reduced magnetohydrodynamic models in Cartesian geometry, where two magnetic field components are present: the strong guide field B 0, extended along the axial direction, and the dynamical orthogonal field b. Magnetic field lines thread the system along the axial direction that spans the length L and are line-tied at the top and bottom plates. The magnetic field b initially has only large scales, with its gradient (current) length scale of the order of l b . We identify the magnetic intensity threshold b/B 0 ~ l b /L. For values of b below this threshold, field-line tension inhibits the formation of current sheets, while above the threshold they form quickly on fast ideal timescales. In the ideal case, above the magnetic threshold, we show that current sheets thickness decreases in time until it becomes smaller than the grid resolution, with the analyticity strip width δ decreasing at least exponentially, after which the simulations become underresolved. Title: Field Line Topology and Rapid Reconnection Authors: Parker, Eugene N. Bibcode: 2012ASSP...33....3P Altcode: 2012msdp.book....3P Consider a magnetic field extending through an infinitely conducting fluid between end plates z = 0, z = L, with arbitrary interlacing of the field lines throughout. The field is fixed in both endplates and is allowed to relax to an equilibrium described by the force-free equilibrium equation ∇ ×B = αB. The divergence of this field equation yields ∇ ṡα = 0, requiring that the torsion coefficient α be constant along each individual field line, and showing that the field lines represent a family of real characteristics of the equilibrium field equation. So the field line topology plays a direct role in determining the nature of the equilibrium field. For an arbitrarily prescribed interlacing field line topology a continuous field generally cannot provide an α that is constant along field lines. Yet with the field fixed at both ends it is obvious that every topology has an equilibrium. So there must be a mathematical solution to the field equation for each and every topology. This dilemma is resolved by the fact that the field lines represent a family of real characteristics, so that surfaces of discontinuity (current sheets) can form along the flux surfaces. In almost all field line topologies, then, the continuous field is cut up by surfaces of tangential discontinuity between regions of continuous field. Title: The Dynamics of the Heliosphere from 1961 TO Voyagers i and II in 2011 Authors: Parker, E. N. Bibcode: 2011AGUFMSH13C..02P Altcode: The first MHD models of the heliosphere were produced in 1961, illustrating the theoretical shape of the heliosphere in the two extremes of an interstellar wind without interstellar magnetic field and an interstellar magnetic field without a wind. The lack of information on the density and velocity of the solar wind, and on the interstellar wind and magnetic field, precluded any real estimate of the dimensions of the heliosphere at that time. The plasma detector on the Mariner II voyage to Venus in 1962 brought the realities into focus, measuring wind densities of 5 ions/cc and velocities of 300 - 700 km/sec. The subsequent exploration of the solar wind has filled in the picture in considerable detail. Most recently, Voyagers I and II have determined the dimensions of the heliosphere, as well as suggesting unanticipated dynamical effects in the heliosheath. For instance, rapid reconnection of the magnetic sector structure into separate magnetic bubbles is predicted. Then the curious 4 AU region of vanishing radial wind velocity requires explanation. We have also learned that the anomalous cosmic rays are not accelerated in the terminal shock, at least in the regions penetrated by the Voyagers. So there is much yet to be understood, much like the situation in 1961 fifty years ago. Title: Kinetic and Hydrodynamic Representations of Coronal Expansion and The Solar Wind Authors: Parker, E. N. Bibcode: 2010AIPC.1216....3P Altcode: We consider the Lemaire-Scherer construction of the supersonic solar wind as the kinetic escape of a collisionless (scatter-free) plasma from an exosphere near the Sun. The radial electric field enforces equality of the electron and ion densities and also equality of the electron and ion fluxes. Consequently, the electrons form an electrostatically confined atmosphere with the temperature declining outward only slowly from the exosphere and becoming the work horse that lifts and accelerates the ions to supersonic velocity. Title: Extraterrestrial Amino Acids in the Almahata Sitta Meteorite Authors: Callahan, Michael; Aubrey, A.; Bada, J. L.; Dworkin, J. P.; Elsila, J. E.; Glavin, D. P.; Parker, E.; Jenniskens, P. Bibcode: 2009DPS....41.0909C Altcode: The recovery of meteorite fragments from the 2008 TC3 asteroid impact, collectively named Almahata Sitta, revealed a rare, anomalous polymict ureilite containing large carbonaceous grains (Jenniskens et al. 2009). Here we report the first amino acid analysis of a meteorite from an F-type asteroid as part of the Almahata Sitta meteorite sample analysis consortium. A single fragment (piece #4, 1.2 grams) was crushed to a powder, and separate 0.1 g aliquots of the same meteorite were carried through identical hot-water extraction, acid hydrolysis and desalting procedures at NASA Goddard Space Flight Center and the Scripps Institution of Oceanography. The o-phthaldialdehyde/N-acetyl-L-cysteine amino acid derivatives in the extracts were analyzed by high performance liquid chromatography with UV fluorescence detection and time-of-flight mass spectrometry. Analyses of the meteorite extracts revealed a complex distribution of two- to six-carbon aliphatic amino acids with abundances ranging from 0.5 to 69 parts-per-billion (ppb). Glycine was the most abundant amino acid detected, however, since this protein amino acid is a common terrestrial contaminant, we are currently unable to rule out at least a partial terrestrial source. However, the D/L ratio of alanine in the meteorite was racemic, suggesting that very little terrestrial amino acid contamination. Several non-protein amino acids that are rare in the biosphere were also identified in the meteorite above background levels including D,L-4-amino-2-methybutyric acid (65 ± 8 ppb), D-isovaline (1.3 ± 0.1 ppb), L-isovaline (1.4 ± 0.1 ppb), and α-aminoisobutryic acid (7.1 ± 5.8 ppb). The abundance of isovaline and AIB are 1000 times lower than the abundances found in the CM2 meteorite Murchison while D,L-4-amino-2-methybutyric acid is similar. The very low amino acid abundances and the presence of several amino acid decomposition products including methylamine, ethylamine, and isopropylamine are consistent with extensive thermal alteration of organic compounds on the parent asteroid. Title: Exploration of amino acid biomarkers in polar ice with the Mars Organic Analyzer Authors: Jayarajah, C.; Botta, O.; Aubrey, A.; Parker, E.; Bada, J.; Mathies, R. Bibcode: 2009AGUSM.P11A..08J Altcode: A portable microfabricated capillary electrophoresis (CE) system named the Mars Organic Analyzer (MOA) has been developed to analyze fluorescently-labeled biomarkers including amino acids, amines, nucleobases, and amino sugars with the goal of life detection on Mars (1,2). This technology has also been shown to be effective in screening the formation of biogenic amines during fermentation (3). The MOA is a part of the Urey instrument package that has been selected for the 2016 European ExoMars mission by ESA. The identification of recent gully erosion sites, observations of ice on and beneath the surface of Mars, and the discovery of large reservoirs of sub-surface ice on Mars point to water-ice as an important target for astrobiological analyses. In addition, the ice samples on the Moon, Mercury, Europa and Enceladus are of interest due to the possibility that they may contain information on biogenic material relevant to the evolution of life. We explore here the use of the MOA instrument for the analysis of amino acids in polar ice samples. The amino acids valine, alanine/serine, glycine, glutamic acid, and aspartic acid were found in the parts-per-billion range from Greenland ice-core samples. Chiral analysis of these samples yielded D/L ratios of 0.51/0.09 for alanine/serine and 0.14/0.06 for aspartic acid. Individual amino acids in the parts-per-trillion range were found in Antarctic ice samples collected from the surface of a meteorite collection area. The distinct amino acid and amine content of these samples indicates that further biomarker characterization of ice samples as a function of sampling location, depth, and structural features will be highly informative. The rapid sensitive analysis capabilities demonstrated here establish the feasibility of using the MOA to analyze the biomarker content of ice samples in planetary exploration. 1. Skelley, A. M.; Scherer, J. R.; Aubrey, A. D.; Grover, W. H.; Ivester, R. H. C., Ehrenfreund, P.; Grunthaner, F. J.; Bada, J. L.; Mathies, R. A. PNAS, 2005, 192, 1041. 2. Skelley, A. M., Cleaves, H. J., Jayarajah, C. N., Bada, J. L. and Mathies, R. A., Astrobiology 2006, 6, 824. 3. Jayarajah, C.N., Skelley, A.M., Fortner, A.D., and Mathies, R.A., Anal. Chem. 2007, 79, 21, 8162. Title: Hydrodynamics, magnetohydrodynamics, and astrophysical plasmas Authors: Parker, E. N. Bibcode: 2009cwse.conf...23P Altcode: No abstract at ADS Title: Solar Magnetism: The State of Our Knowledge and Ignorance Authors: Parker, E. N. Bibcode: 2009SSRv..144...15P Altcode: 2008SSRv..tmp..170P We review some longstanding scientific mysteries related to solar magnetism, with final attention to the mystery of the “turbulent diffusion” essential for the theoretical α ω-dynamo that is believed to be the source of the magnetic fields of the Sun. Fundamental difficulties with the concept of turbulent diffusion of magnetic fields suggest that the solar dynamo problem needs to be reformulated. An alternative dynamo model is proposed, but it remains to be shown that the model can provide the quantitative aspects of the cyclic magnetic fields of the Sun. Title: Solar Magnetism: The State of Our Knowledge and Ignorance Authors: Parker, E. N. Bibcode: 2009odsm.book...15P Altcode: We review some longstanding scientific mysteries related to solar magnetism, with final attention to the mystery of the "turbulent diffusion" essential for the theoretical α ω-dynamo that is believed to be the source of the magnetic fields of the Sun. Fundamental difficulties with the concept of turbulent diffusion of magnetic fields suggest that the solar dynamo problem needs to be reformulated. An alternative dynamo model is proposed, but it remains to be shown that the model can provide the quantitative aspects of the cyclic magnetic fields of the Sun. Title: Minor Planet Observations [705 Apache Point] Authors: Becker, A.; Babylon, E.; Hollingsworth, T.; Becker, A. C.; Puckett, A. W.; Hendrickson, S.; Vasquez, L.; Zumwalt, L.; Burton, M.; Dilucchio, H.; Higley, E.; Warnock, L.; Brady, S.; Gablehouse, G.; Kintz, K.; Ouellette, A.; Parker, E.; Ratley, L.; Holmes-Perry, K.; Hovden, L.; King, C.; Leemhuis, J.; Pascall, R.; Schwebke, J. Bibcode: 2008MPC..64488...6B Altcode: No abstract at ADS Title: Ironstone Concretions - Analogs to Martian Hematite Spherules Authors: Aubrey, A. D.; Parker, E.; Chalmers, J. H.; Lal, D.; Bada, J. L. Bibcode: 2007LPI....38.2053A Altcode: We report herein physical and chemical characterization of a new terrestrial analog to the martian "blueberries" found throughout San Diego County. Title: Conversations on Electric and Magnetic Fields in the Cosmos Authors: Parker, Eugene N. Bibcode: 2007cemf.book.....P Altcode: No abstract at ADS Title: Solar Wind Authors: Parker, E. N. Bibcode: 2007hste.book...96P Altcode: No abstract at ADS Title: Interstellar Conditions and Planetary Magnetospheres Authors: Parker, Eugene N. Bibcode: 2006ASSL..338...87P Altcode: No abstract at ADS Title: Heating the Solar X-Ray Corona Authors: Parker, E. N. Bibcode: 2005ESASP.596E...1P Altcode: 2005ccmf.confE...1P No abstract at ADS Title: Principles of Magnetohydrodynamics, with Applications to Laboratory and Astrophysical Plasma. By H. GOEDBLOED & S. POEDT. Cambridge University Press, 2004. 632 pp. ISBN 0521 623472, £80 (hardback); ISBN 0521 626072, £40 (paperback) Authors: Parker, E. N. Bibcode: 2004JFM...519..377P Altcode: Available from http://dx.doi.org/10.1017/S0022112004001466 Title: New Seafloor Map of the Puerto Rico Trench Helps Assess Earthquake and Tsunami Hazards Authors: ten Brink, Uri; Danforth, William; Polloni, Christopher; Andrews, Brian; Llanes, Pilar; Smith, Shepard; Parker, Eugene; Uozumi, Toshihiko Bibcode: 2004EOSTr..85..349T Altcode: 2004EOSTr..85..349B The Puerto Rico Trench, the deepest part of the Atlantic Ocean, is located where the North American (NOAM) plate is subducting under the Caribbean plate (Figure 1). The trench region may pose significant seismic and tsunami hazards to Puerto Rico and the U.S. Virgin Islands, where 4 million U.S. citizens reside. Widespread damage in Puerto Rico and Hispaniola from an earthquake in 1787 was estimated to be the result of a magnitude 8 earthquake north of the islands. A tsunami killed 40 people in NW Puerto Rico following a magnitude 7.3 earthquake in 1918. Large landslide escarpments have been mapped on the seafloor north of Puerto Rico, although their ages are unknown. The Puerto Rico Trench is atypical of oceanic trenches. Subduction is highly oblique (10°-20°) to the trench axis with a large component of left-lateral strike-slip motion. Similar convergence geometry is observed at the Challenger Deep in the Mariana Trench, the deepest point on Earth. In addition to its extremely deep seafloor, the Puerto Rico Trench is also characterized by the most negative free-air gravity anomaly on Earth, -380 mGal, located 50 km south of the trench, where water depth is 7950 m (Figure 2). A tilted carbonate platform provides evidence for extreme vertical tectonism in the region. This platform was horizontally deposited over Cretaceous to Paleocene arc rocks starting in the Late Oligocene. Then, at 3.5 Ma, the carbonate platform was tilted by 4° toward the trench over a time period of less than 40 kyr, such that its northern edge is at a depth of 4000 m and its reconstructed elevation on land in Puerto Rico is at +1300 m (Figures 1 and 2). Title: The Microworld of the Solar Corona Authors: Parker, Eugene Bibcode: 2004APS..APR.Q1003P Altcode: The corona of the Sun, visible during an eclipse of the Sun, has been a challenge to physics for more than a century, and, for all the scientific progress, the dynamical microstructure of the corona is only beginning to be revealed. To begin, there are three distinct states of the million degree coronal gas: The weak-field coronal hole, and the strong field, X-ray emitting, bipolar magnetic regions, and the active corona surrounding the bipolar regions. Their origin leads into the microworld of the magnetic fields, with the intense magnetic fibrils at the visible surface, the magnetic carpet, and the interlaced bipolar field lines, with the associated nanoflares, microflares, and flares, and all with internal scales of 100 km or less. Unfortunately 100 km is well below the limit of resolution of existing telescopes. An essential step forward is the proposed Advanced Technology Solar Telescope, a 4m ground based telescope with adaptive optics providing resolution down to 50 km, together with rapid cadence, high dispersion spectroscopy to follow the action. Title: Universal Magnetic Reconnection And Coronal Heating Authors: Parker, E. N. Bibcode: 2004hell.conf....1P Altcode: No abstract at ADS Title: Foreword (Dynamic Sun) Authors: Parker, E. N. Bibcode: 2003dysu.bookD..15P Altcode: No abstract at ADS Title: The Advance Solar Telescope and Future Solar Physics Authors: Parker, E. N. Bibcode: 2002AAS...200.3401P Altcode: 2002BAAS...34..690P The magnetic activity of the Sun, with its terrestrial outreach, is conventionally defined in terms of the larger magnetic features on the surface of the Sun, while the evolution of the large magnetic features is largely determined by their small-scale fibril structure. Unfortunately the individual fibrils can be observed only as unresolved bright blobs. Thus their frequent interactions, their internal structure, and the associated dynamical flows all remain a mystery, which prevents our constructing a definitive dynamical theory of the large-scales and of solar activity in general. The microscopic world of magnetic fibrils awaits investigation, requiring a suitable telescope system with adaptive optics at an excellent site so as to provide angular resolution of 0.1" or better on a regular basis. The telescope must be of sufficient aperture ( 4m) to carry on high resolution, high dispersion spectroscopy at rapid cadence to determine the time dependent spatial structure of the gas flows and magnetic fields on the smallest possible scales. It will be important to follow the rapid evolution of the small flux bundle, or fibril, as it first appears through the visible surface somewhere in the interior of a supergranule, and then to follow the resulting magnetic fibril as it is convected into the boundary downdrafts, and ultimately into the junctions of several boundaries. The quiet photosphere, the active photosphere, at both low and high latitudes, the umbra and penumbra of sunspots of all sizes, the ephemeral active regions, the microstructure of all classes of flares, and the microstructure of spicules, surges and prominences are obvious immediate targets for the high resolution telescope. We cannot anticipate what will be seen, but whatever it turns out to be, it will move scientific comprehension well ahead of the present limited conjectural state. Title: A history of the solar wind concept Authors: Parker, E. N. Bibcode: 2002css1.book..225P Altcode: No abstract at ADS Title: A history of early work on the heliospheric magnetic field Authors: Parker, E. N. Bibcode: 2001JGR...10615797P Altcode: The idea of a magnetic field in space around Earth began 400 years ago with Gilbert's recognition that the magnetic field of Earth extends outward into space to form what we now call the magnetosphere. The concept of the solar wind and the heliosphere had its first glimmerings with the recognition, about 270 years ago, that geomagnetic activity is correlated with solar activity. It was suggested about a 100 years ago that the connection is through solar corpuscular radiation with velocities of the order of 103km/s. The observed acceleration of comet tails indicated the universal nature of solar corpuscular radiation, giving rise to the first speculation on the existence of the heliosphere. The hydrodynamic expansion of the million degree solar corona was then shown to provide the solar wind (solar corpuscular radiation), stretching out the magnetic fields of the Sun to fill the heliosphere with a spiral magnetic field. The advent of the space age soon verified the solar wind and magnetic field with direct measurements. Title: A Critical Review of Sun-Space Physics Authors: Parker, E. N. Bibcode: 2001Ap&SS.277....1P Altcode: The Sun and the heliosphere form a single dynamical system, driven by the convection in the Sun and the magnetic fields generated by that convection. The magnetic fields are the primary channel for producing the high temperatures and high velocities that extend outward to form the heliosphere. The essential point is that, while the general picture seems to be reasonable, several important steps in the process are not understood, and several concepts commonly employed in explanation are false physics. These scientific gaps should not be forgotten in the rush to pursue new and exotic discoveries. Title: Magnetic reconnection and the lowest energy state Authors: Parker, E. N. Bibcode: 2001EP&S...53..411P Altcode: No abstract at ADS Title: Solar Activity and Classical Physics Authors: Parker, E. N. Bibcode: 2001ChJAA...1...99P Altcode: This review of solar physics emphasizes several of the more conspicuous scientific puzzles posed by contemporary observational knowledge of the magnetic activity of the Sun. The puzzles emphasize how much classical physics we have yet to learn from the Sun. The physics of solar activity is based on the principles of Newton, Maxwell, Lorentz, Boltzmann, et al., along with the principles of radiative transfer. In the large, these principles are expressed by magnetohydrodynamics. A brief derivation of the magnetohydrodynamic induction and momentum equations is provided, with a discussion of popular misconceptions. Title: The heliosphere as viewed from Earth Authors: Parker, E. N. Bibcode: 2001ohnf.conf..481P Altcode: No abstract at ADS Title: Large-Scale Plasma Dynamics Authors: Parker, E. Bibcode: 2000eaa..bookE2217P Altcode: Most of the universe is occupied by gas that is electrically neutral but more or less fully ionized, i.e. PLASMA, and permeated by a magnetic field B on a large scale L. The plasma, driven by the energy of the stars, is in a remarkably active, and often suprathermal, state. The coronal mass ejection from the Sun is an example of the active state, while the million degree corona of the Sun is an e... Title: Instability of the Stochastic Galactic Magnetic Field Authors: Parker, E. N.; Jokipii, J. R. Bibcode: 2000ApJ...536..331P Altcode: We examine the effects of the stochastic galactic magnetic field on the dynamical instability of the interstellar gas and magnetic field. The large-scale random walk, or meandering, of the magnetic field exerts stresses across the average magnetic field direction, which suppress the growth of perturbations having a small wavelength normal to the field. The result is that, compared with a nonstochastic initial magnetic field, those perturbations, which grow, are significantly broadened in the direction normal to the field. Hence, the instability in a stochastic magnetic field, such as that observed in our Galaxy, should evolve into clouds that are more similar to those that are observed than are those found in the absence of the stochastic field. Title: Solar Flares, the Solar Corona, and Solar Physics Authors: Parker, E. N. Bibcode: 2000IAUS..195..455P Altcode: The Sun serves as the local physics laboratory for studying the suprathermal activity phenomena of stars. Scrutiny of the Sun has led to the discovery of a host of previously unknown physical effects, largely within the classical physics of Newton and Maxwell, but including quantum mechanics and lepton physics as well. Title: Application of Shape Memory Alloys to Rock Splitting: A Successful Example of Cooperation between Space Research and Industry Authors: Carosio, S.; Zangani, D.; Parker, E.; Sutherland, I. Bibcode: 2000ESASP.470...27C Altcode: 2000aics.conf...27C No abstract at ADS Title: TUTORIAL: Newton, Maxwell, and Magnetospheric Physics Authors: Parker, E. N. Bibcode: 2000GMS...118....1P Altcode: 2000mcs..book....1P The goal of magnetospheric physics is to understand the active magnetosphere in terms of the principles of Newton and Maxwell. These principles include Ampere's law, the Faraday induction equation, and the dynamical interplay of the forces between the bulk plasma velocity u, the plasma pressures p and p, and the magnetic field B. It turns out, then, that these principles cannot be written in terms of the electric current density j and the electric field E, to the exclusion of u and B, in any generally useful form, indicating that the electric current and field are not the fundamental physical quantities sometimes claimed. Thus, the description of the active magnetosphere in electrical terms does not directly address the dynamics of the magnetosphere. The popular dynamical concepts of the electric circuit analog and the active role of the electric field E = -u×B/c in the solar wind have not been established from Newton and Maxwell, and application to simple problems illustrates their restrictions and errors. In contrast, magnetospheric physics is making great strides forward using MHD modeling of the large-scale dynamical magnetosphere, and this tutorial emphasizes the generality of the MHD approach. We review the theoretical basis for the momentum equation and the induction equation for the large-scale nonrelativistic dynamics of the magnetosphere and ionosphere, showing the general MHD character of the contending stresses and momenta. Title: LOTIS Limits on Prompt Optical Emission from GRBs Authors: Hartmann, D. H.; Williams, G. G.; Park, H. S.; Ables, E.; Band, D. L.; Barthelmy, S. D.; Bionta, R.; Butterworth, P. S.; Cline, T. L.; Ferguson, D. H.; Fishman, G. J.; Gehrels, N.; Hurley, K.; Kouveliotou, C.; Meegan, C. A.; Ott, L.; Parker, E.; Porrata, R. Bibcode: 2000sgrb.conf...37H Altcode: No abstract at ADS Title: SOLSPA Summary Summary and Perspectives Authors: Parker, E. N. Bibcode: 2000ESASP.463..263P Altcode: 2000sctc.proc..263P No abstract at ADS Title: The physics laboratory in the sky Authors: Parker, E. N. Bibcode: 1999CSci...77.1445P Altcode: No abstract at ADS Title: Space Physics Before the Space Age Authors: Parker, E. N. Bibcode: 1999ApJ...525C.792P Altcode: 1999ApJC..525..792P No abstract at ADS Title: The separation of field and fluid in the Sun Authors: Parker, E. N.; Thyagaraja, A. Bibcode: 1999SoPh..189...45P Altcode: The magnetic field at the surface of the Sun is confined to widely separated small, intense magnetic flux bundles or fibrils with most of the gas in a relatively field free state in the interstices. There is evidently a systematic field and fluid separation effect in operation, overriding the tendency for turbulent mixing of the two phases. It is well known that a constantly rotating volume of fluid soon excludes any exterior magnetic field. To take the next theoretical step, this paper examines the exclusion of magnetic field from a circular cylinder with oscillating angular velocity. The result is that the field is effectively excluded from any oscillating or tumbling body of fluid that maintains coherence over a sufficiently long time. However, there is no expectation of such long term coherence in turbulent convection in the Sun, suggesting that the observed separation of field and fluid does not come about by the exclusion of field from convective cells. This leads to the conclusion that the separation of fluid and field is a consequence of extraction of fluid from the field through buoyancy and reconnection. Title: LOTIS Search for Early-Time Optical Afterglows: GRB 971227 Authors: Williams, G. G.; Park, H. S.; Ables, E.; Band, D. L.; Barthelmy, S. D.; Bionta, R.; Butterworth, P. S.; Cline, T. L.; Ferguson, D. H.; Fishman, G. J.; Gehrels, N.; Hartmann, D. H.; Hurley, K.; Kouveliotou, C.; Meegan, C. A.; Ott, L.; Parker, E.; Porrata, R. Bibcode: 1999ApJ...519L..25W Altcode: 1999astro.ph..2190W We report on the very early time search for an optical afterglow from GRB 971227 with the Livermore Optical Transient Imaging System (LOTIS). LOTIS began imaging the ``original'' BATSE error box of GRB 971227 ~14 s after the onset of gamma-ray emission. Continuous monitoring of the position throughout the evening yielded a total of 499 images (10 s integration). Analysis of these images revealed no steady optical afterglow brighter than R=12.3+/-0.2 in any single image. Co-addition of the LOTIS images also failed to uncover transient optical emission. In particular, assuming a constant early-time flux, no optical afterglow brighter than R=14.2+/-0.2 was present within the first 1200 s, and no optical afterglow brighter than R=15.0+/-0.2 was present in the first 6.0 hr. Follow-up observations by other groups revealed a likely X-ray afterglow and a possible optical afterglow. Although subsequent deeper observations could not confirm a fading source, we show that these transients are not inconsistent with our present knowledge of the characteristics of gamma-ray burst afterglows. We also demonstrate that with the upgraded thermoelectrically cooled CCDs, LOTIS is capable of either detecting very early time optical afterglow or placing stringent constraints on the relationship between the gamma-ray emission and the longer wavelength afterglow in relativistic blast-wave models. Title: Space physics before the space age Authors: Parker, E. N. Bibcode: 1999AIPC..471....3P Altcode: 1999sowi.conf....3P The concept of space and the ponderable dynamical activity in space have a long history of development, going back centuries and millenia, and what is commonplace today should not be considered apriori obvious, however ``obvious'' it may seem now that it has been discovered and studied. The development of space physics over the centuries has followed close on the heels of the development of physics. With the fundamental laws of classical physics well in hand today, present space physics research aims at direct discovery of the diverse phenomena occurring in space, followed by sufficiently detailed quantitative study to understand how the effects follow from the basic principles of Newton, Maxwell, Boltzmann, et al. The pursuit of space physics often turns up new twists to the ``old'' physics of the terrestrial laboratory, made possible by the vastly greater dimensions of space. The present review traces the development of physics and its application to space physics from classical times to the early years of the space age, when direct in situ studies of space became possible. Title: Solar physics: Sunny side of global warming Authors: Parker, E. N. Bibcode: 1999Natur.399..416P Altcode: No abstract at ADS Title: It Started with George Ellery Hale Authors: Parker, E. N. Bibcode: 1999AAS...194.5703P Altcode: 1999BAAS...31..915P With his invention of the spectroheliograph, showing the structure and activity of the surface of the Sun, and with his spectroscopic determination of the magnetic character of the sunspot, Hale initiated a line of research that has brought us deeper into the mysteries of the Sun with each passing decade. The flare is perhaps the most spectacular aspect of the activity, along with the more recently discovered coronal mass ejection. However, we must not overlook the spectacular revelation, by Grotrian, Edlen, and Lyot, that the outer atmosphere of the Sun has a temperature of a million or more degrees K, providing both radio and X-ray emission. It is all too often forgotten in these heady times that, while we have a number of plausible ideas about how things work, there is not yet a clear understanding of why a late main sequence star should exhibit such effects. Magnetic fields generated by some form of MHD dynamo appear to initiate the suprathermal activity in all its many forms. The intensely fibril form of the magnetic fields seems to be a clue to the nature of the dynamo process, and the first observational priority now is to develop a 4m telescope with an adaptive optics system that can properly resolve the individual fibrils at the visible surface (0.1" or better)to determine their behavior. Indeed the nature of the sunspot, the faculae and plages,the microflare, etc. all lie at the limits of telescopic resolution. The varying brightness of the Sun seems to be a byproduct of the magnetic activity, and besides the consequences for the climate at Earth, provides another baffling clue to the puzzle. We cannot guess what further marvels will be discovered before the puzzle is resolved in hard scientific terms, but we may be certain that Hale would have been enchanted, and probably leading the charge, were he alive today. Title: Fifty Years of the Galactic Magnetic Field Authors: Parker, E. N. Bibcode: 1999AAS...194.2503P Altcode: 1999BAAS...31..863P Scientific awareness of the galactic magnetic field had its beginning in the years 1948 - 1951 with Fermi's work on cosmic rays, and the observation of the polarization of dust reddened starlight by Hiltner and Hall, and the interpretation of the polarization in terms of magnetically aligned dust grains by Spitzer and Tukey and by Davis and Greenstein. The field was more or less along the local spiral arm, with large fluctuations on scales of 100 pc. Faraday rotation measurements indicated a strength of the order of a few microgauss, and dynamical considerations on the structure of the gaseous disk of the galaxy suggested similar values. By 1966 it was clear that the magnetic field and the cosmic ray gas were tied to the interstellar gas to form an unstable active tripart dynamical system. The system is continually inflated by blast waves from supernovae and particularly by the cosmic ray gas from supernovae, which extend lobes of the galactic magnetic field outward at speeds of the order of 50 km/sec in both directions from the disk of the Galaxy to form the galactic halo. The dissipation of shock waves and the dissipation of magnetic field in the halo evidently provide the multi-million degree gas responsible for the x-ray emission from the halo, best seen from galaxies other than our own. The concentration of magnetic field in and along the spiral density waves forming the spiral arms strongly suggests that the galactic magnetic field represents a progressive dynamo wave. However, the dynamo theory of the galactic magnetic field has yet to establish the nature of the field dissipation that makes the dynamo possible. Title: Magnetic Discontinuities from Field Topology Authors: Parker, E. N. Bibcode: 1999Ap&SS.264....1P Altcode: 1998Ap&SS.264....1P No abstract at ADS Title: LOTIS Constraints on Simultaneous and Early Time Optical Emission from Gamma-Ray Bursts Authors: Williams, G. G.; Hartmann, D. H.; Park, H. S.; Ables, E.; Bionta, R.; Ott, L.; Parker, E.; Band, D. L.; Barthelmy, S. D.; Butterworth, P. S.; Cline, T. L.; Gehrels, N.; Ferguson, D. H.; Fishman, G. J.; Meegan, C. A.; Kouveliotou, C.; Hurley, K. Bibcode: 1998AAS...192.4304W Altcode: 1998BAAS...30..874W LOTIS (Livermore Optical Transient Imaging System) is a gamma-ray burst (GRB) optical counterpart search experiment capable of imaging an initial GRB error box within 10 s of the start of a burst. This early response, often simultaneous with gamma-ray emission, is accomplished by utilizing a fully automated rapidly slewing telescope linked to the GRB Coordinates Network (GCN). The LOTIS telescope consists of four cameras configured in a 2 x 2 array with a total field-of-view of 17.4(deg) x 17.4(deg) . Since routine operations began in October 1996 LOTIS has responded to more than 40 GCN triggers. We will report on LOTIS observations which have placed upper limits on the ratio of simultaneous optical to gamma-ray flux. A recent upgrade to thermoelectric cooled CCDs increased the LOTIS sensitivity to V ~ 15 (10 s integration) extending the capability of detecting or further constraining simultaneous optical activity from GRBs. In addition to LOTIS, Super-LOTIS, a fully automated 60 cm reflector with a limiting magnitude of V ~ 19 will soon begin a dedicated search for optical counterparts of GRBs. Both the upgraded LOTIS system and Super-LOTIS will also search for very early time optical afterglow from GRBs. Title: Super-LOTIS a high-sensitive optical counterpart search experiment Authors: Park, H. S.; Ables, E.; Band, D. L.; Barthelmy, S. D.; Bionta, R. M.; Butterworth, P. S.; Cline, T. L.; Ferguson, D. H.; Fishman, G. J.; Gehrels, N.; Hartmann, D.; Hurley, K.; Kouveliotou, C.; Meegan, C. A.; Ott, L.; Parker, E.; Williams, G. G. Bibcode: 1998AIPC..428..842P Altcode: 1998hgrb.symp..842P We are constructing a 0.6 meter telescope system to search for early time gamma-ray burst (GRB) optical counterparts. Super-LOTIS (Super-Livermore Optical Transient Imaging System) is an automated telescope system that has a 0.8°×0.8° field-of-view, is sensitive to Mv~19 and responds to a burst trigger within 5 min. This telescope will record images of the gamma-ray burst coordinates that are given by the GCN (GRB Coordinate Network). A measurement of GRB light curves at early times will greatly enhance our understanding of GRB physics. Title: First year results from LOTIS Authors: Williams, G. G.; Park, H. S.; Ables, E.; Band, D. L.; Barthelmy, S. D.; Bionta, R.; Butterworth, P. S.; Cline, T. L.; Ferguson, D. H.; Fishman, G. J.; Gehrels, N.; Hartmann, D. H.; Hurley, K.; Kouveliotou, C.; Meegan, C. A.; Ott, L.; Parker, E.; Wurtz, R. Bibcode: 1998AIPC..428..837W Altcode: 1998hgrb.symp..837W LOTIS (Livermore Optical Transient Imaging System) is a gamma-ray burst optical counterpart search experiment located near Lawrence Livermore National Laboratory in California. The system is linked to the GCN (GRB Coordinates Network) real-time coordinate distribution network and can respond to a burst trigger in 6-15 seconds. LOTIS has a total field-of-view of 17.4°×17.4° with a completeness sensitivity of mv~11 for a 10 second integration time. Since operations began in October 1996, LOTIS has responded to over 30 GCN/BATSE GRB triggers. Seven of these triggers are considered good events subject to the criteria of clear weather conditions, <60 s response time, and >50% coverage of the final BATSE 3σ error circle. We discuss results from the first year of LOTIS operations with an emphasis on the observations and analysis of GRB971006 (BATSE trigger 6414). Title: The sun: the ultimate challenge to astrophysics Authors: Parker, E. N. Bibcode: 1998AdSpR..21..267P Altcode: Among the many exotic astronomical objects available for study, the proximity of the Sun provides the principal source of new physics, ranging from neutrinos to the mysteries of the magnetohydrodynamic activity and to the geological evolution of terrestrial climate. For it must be recalled that it is not known why the Sun is compelled by the laws of nature to produce something as familiar as the sunspot or as unexpected as the year by year variation in irradiance. The next decade holds exciting promise of experimental exploration of neutrino physics, advanced helioseismic exploration of magnetic fields below the photosphere, and high resolution glimpses of the small scale activity and magnetic fibril behavior at the visible surface (e.g. SOHO). It behooves the solar physics community to represent the productive state of affairs to the rest of the astrophysical world, who need the physics in their speculations on the nature of their unresolved objects. Title: LOTIS: A Search for Simultaneous Optical Counterparts of Gamma-Ray Bursts Authors: Williams, G. G.; Hartmann, D. H.; Park, H. S.; Ables, E.; Bionta, R.; Ott, L.; Parker, E.; Band, D. L.; Barthelmy, S. D.; Butterworth, P. S.; Cline, T. L.; Gehrels, N.; Ferguson, D. H.; Fishman, G. J.; Meegan, C. A.; Kouveliotou, C.; Hurley, K. Bibcode: 1998BAAS...30..762W Altcode: LOTIS (Livermore Optical Transient Imaging System) is a gamma-ray burst (GRB) optical counterpart search experiment located near Lawrence Livermore National Laboratory in California. The LOTIS telescope consists of a 2 x 2 array of cameras mounted on a rapidly slewing mount. The system is fully automated and linked to the GRB Coordinates Network (GCN). Imaging of an initial GRB error box begins ~ 6--15 s after the start of a burst. LOTIS can detect all objects brighter than V ~ 11 (10 s integration) within a total field-of-view of 17.4(deg) x 17.4(deg) . Since the beginning of routine operations in October 1996, LOTIS has responded to over 35 GCN triggers. We will report on the results from the first year of LOTIS operations with an emphasis on the photometric analysis of the observations. Title: Reflections on Macrophysics and the Sun (Special Historical Review) Authors: Parker, E. N. Bibcode: 1997SoPh..176..219P Altcode: No abstract at ADS Title: New Constraints on Simultaneous Optical Emission From Gamma-Ray Bursts Measured by the Livermore Optical Transient Imaging System Experiment Authors: Park, H. S.; Williams, G. G.; Ables, E.; Band, D. L.; Barthelmy, S. D.; Bionta, R.; Butterworth, P. S.; Cline, T. L.; Ferguson, D. H.; Fishman, G. J.; Gehrels, N.; Hartmann, D.; Hurley, K.; Kouveliotou, C.; Meegan, C. A.; Ott, L.; Parker, E.; Wurtz, R. Bibcode: 1997ApJ...490L..21P Altcode: LOTIS is a gamma-ray burst optical counterpart search experiment located near Lawrence Livermore National Laboratory in California. Since operations began in 1996 October, LOTIS has responded to five triggers as of 1997 July 30, which occurred during good weather conditions.

GRB 970223 (BATSE trigger 6100) was an exceptionally strong burst, lasting ~30 s with a peak at ~8 s. LOTIS began imaging the error box ~11 s after the burst began and achieved simultaneous optical coverage of 100% of the region enclosed by the BATSE 3 σ error circle and the interplanetary network annulus. No optical transients were observed brighter than the mV~11 completeness limit of the resulting images, providing a new upper limit on the ratio of simultaneous optical to gamma-ray fluence of RL<1.1×10-4 and on the ratio of simultaneous optical (at 700 nm) to gamma-ray (at 100 keV) flux density of RF<305 for a B-type spectrum and RF<475 for an M-type spectrum. Title: New Constraints on Simultaneous Optical Emission From GRBs Measured by the LOTIS Experiment Authors: Park, H. S.; Williams, G. G.; Ables, E.; Band, D. L.; Barthelmy, S. D.; Bionta, R.; Butterworth, P. S.; Cline, T. L.; Ferguson, D. H.; Fishman, G. J.; Gehrels, N.; Hartmann, D.; Hurley, K.; Kouveliotou, C.; Meegan, C. A.; Ott, L.; Parker, E.; Wurtz, R. Bibcode: 1997astro.ph..8130P Altcode: LOTIS is a gamma-ray burst optical counterpart search experiment located near Lawrence Livermore National Laboratory in California. Since operations began in October 1996, LOTIS has responded to five triggers as of July 30, 1997, which occurred during good weather conditions. GRB970223 (BATSE Trigger #6100) was an exceptionally strong burst lasting $\sim30$ s with a peak at $\sim8$ s. LOTIS began imaging the error box $\sim 11$ s after the burst began, and achieved simultaneous optical coverage of 100% of the region enclosed by the BATSE $3\sigma$ error circle and the IPN annulus. No optical transients were observed brighter than the m$_V \sim 11$ completeness limit of the resulting images providing a new upper limit on the simultaneous optical to gamma-ray fluence ratio of $R_L < 1.1 \times 10^{-4}$ and on the simultaneous optical (at 700 nm) to gamma-ray (at 100 keV) flux density ratio of $R_F < 305$ for a B type spectrum and $R_F < 475$ for an M type spectrum. Title: Spontaneous current sheets and stellar x-ray emission Authors: Parker, E. N. Bibcode: 1997PPCF...39A...9P Altcode: The x-ray emission from a star like the sun comes from plasma at 106-107 K and 1010 ions cm-3- trapped in the 100 Gauss bipolar magnetic fields of active regions. The x-ray intensity reaches 107 ergs cm-2s-1, which is a measure of the heat input required to maintain the temperature of the emitting gas. The basic energy input is photospheric convection, which swirls and intermixes the photospheric footpoints of the bipolar magnetic fields, thereby creating an interlaced topology of the field lines in the bipolar field above the photosphere. The basic theorem of magnetostatics asserts that almost all field topologies develop internal tangential discontinuities as the field relaxes to equilibrium. The discontinuities are a necessary and sufficient condition for the Maxwell stresses to achieve static balance. It appears that rapid reconnection across these internal current sheets provides the principal heat source for the x-ray corona. Title: Reply Authors: Parker, E. N. Bibcode: 1997JGR...102.9657P Altcode: No abstract at ADS Title: Spontaneous current sheets and stellar x-ray emission Authors: Parker, E. N. Bibcode: 1997PPCF...39....9P Altcode: No abstract at ADS Title: Adventures With the Geomagnetic Field Authors: Parker, E. N. Bibcode: 1997dima.conf..143P Altcode: No abstract at ADS Title: Galactic Dynamos and Other Questions on the Origins of Magnetic Fields Authors: Parker, E. N. Bibcode: 1997cdc..conf..309P Altcode: No abstract at ADS Title: Mass Ejection and a Brief History of the Solar Wind Concept Authors: Parker, E. N. Bibcode: 1997cwh..conf....3P Altcode: 2006mslp.conf....3P No abstract at ADS Title: S. Chandrasekhar and Magnetohydrodynamics Authors: Parker, E. N. Bibcode: 1996JApA...17..147P Altcode: No abstract at ADS Title: The X-ray Coronae of Solitary Late-Type Stars Authors: Parker, E. N. Bibcode: 1996SoPh..169..327P Altcode: Recent observations of the motion of the footpoints of the bipolar magnetic fields of active X-ray regions of the Sun establish that the footpoints are intermixed on the same characteristic time and scale as the granule motions. It follows that the bipolar magnetic fields have an internally interlaced topology creating magnetic free energy. It follows from the basic theorem of magnetostatics that the topology creates internal surfaces of tangential discontinuity which effectively dissipate the magnetic free energy into heat. This process appears to be the cause of the X-ray coronae of solitary late Main-Sequence stars like the Sun. Title: Comment on ``Current Paths in the Corona and Energy Release in Solar Flares'' Authors: Parker, E. N. Bibcode: 1996ApJ...471..489P Altcode: The dynamical behavior of an electrically conducting fluid containing a magnetic field B is described by Newton's and Maxwell's equations directly in terms of the momentum density, Reynolds stress, and Maxwell stress, all expressed simply in terms of B and v. The mathematical solution to the equations with the appropriate initial conditions (t = 0) and boundary conditions on B and v provides a complete and unique description of B and v for t > 0 so that further modifications are not possible. On the other hand, the electric current paradigm urged by Melrose provides dynamical equations that are mathematically intractable. The declaration of an electric current analog to replace a mathematical solution of the dynamical equations yields results that are at variance with the solutions of Newton's and Maxwell's equations. We suggest that a proper solution of the equations in terms of B and v is the preferable modus operandi in large-scale astronomical scenarios. Title: Inferring Mean Electric Currents in Unresolved Fibril Magnetic Fields Authors: Parker, E. N. Bibcode: 1996ApJ...471..485P Altcode: It is shown that the curl of the transverse magnetogram of magnetic fields composed of unresolved separate fibrils bears no direct relation to the mean longitudinal electric current density. The mean current density is essentially zero, regardless of the spatial variation and torsion of the mean field. Title: The alternative paradigm for magnetospheric physics Authors: Parker, E. N. Bibcode: 1996JGR...10110587P Altcode: This paper emphasizes that the macrodynamics of the terrestrial magnetosphere is more effectively treated in terms of the primary variables B and v (the B, v paradigm). The common practice of relating the dynamics to E and j (the E, j paradigm) provides direct answers in a variety of symmetric cases, but breaks down in even so simple a static problem as a flux bundle displaced (perhaps by reconnection with the magnetic field in the solar wind) from its normal equilibrium position in a static dipole field. The essential point is that a direct derivation from the equations of Maxwell and Newton leads to field equations written in terms of the continuum fields B and v. The equations can be recast in terms of E and j, of course, but they are then unwieldy, being integrodifferential equations. Hence the E, j paradigm, when correctly applied, is seriously limited in its effectiveness in dynamical problems. Circumventing the limitations with the common declaration that E is the prime mover, actively penetrating from the solar wind into the magnetosphere, provides dynamics that is unfortunately at variance with the results that follow directly from Maxwell and Newton. The paper outlines the standard derivation of the basic field equations and then goes on to treat a variety of circumstances to illustrate the effectiveness of the deductive B, v paradigm in the continuum dynamics of the magnetic field and plasma. There is no attempt to develop a comprehensive model of magnetospheric activity. However we suggest that the ultimate task is more effectively attacked with the B, v paradigm. Title: The Sun as the Ultimate Challenge to Astrophysics: The Vital Phase of Solar Physics Authors: Parker, E. N. Bibcode: 1996mpsa.conf..399P Altcode: 1996IAUCo.153..399P No abstract at ADS Title: Solar variability and teffestrial climate. Authors: Parker, E. N. Bibcode: 1996sube.conf..117P Altcode: No abstract at ADS Title: Questions and conjectures on the origin of stellar and galactic magnetic fields. Authors: Parker, E. Bibcode: 1996ASIC..481....1P Altcode: The magnetic fields of the Sun and the Galaxy, as prototypes of the fields of other stars and galaxies, appear to originate in some form or variant of the well known αω-dynamo. However, the αω-dynamo can function only in the presence of irreversible diffusion and dissipation of the small-scale internal magnetic fields, requiring effective diffusion coefficients of the order of 1012 and 1025 cm2/sec for the Sun and Galaxy, respectively. It is hypothesized that the magnetic field of the Sun is in an intensely fibril state throughout the convective zone, with rapid reconnection wherever nonparallel fibrils are pressed together by the fluid motions. The result of this scenario would seem to be a sufficiently rapid irreversible interdiffusion of fields for successful operation of the solar dynamo. For the Galaxy it is hypothesized that rapid reconnection between the extended magnetic lobes or Ω-loops that form the halo accomplished the irreversibility necessary for the operation of the galactic dynamo. Title: Some implications of solar and stellar activity. Authors: Parker, E. Bibcode: 1996ASIC..481..337P Altcode: The astonishing variability and suprathermal activity of the Sun and similar stars is presened as a problem in physics, about which there is currently more conjecture than hard fact. Attention is directed to the coronal hole, the active X-ray corona, and to the overall variation in solar brightness. The variation of solar brightness has profound effect on terrestrial climate. The observational difficulties are listed. Title: Theoretical Properties of Omega -Loops in the Convective Zone of the Sun. V. Coriolis Force and the Centrifugal Potential Barrier Authors: Parker, E. N. Bibcode: 1995ApJ...454..927P Altcode: The effect of Coriolis force and centrifugal force on a rising sheet of fluid in an otherwise rigidly rotating fluid body (representing an idealized solar convective zone) is treated, showing the minor effect on the Kelvin-Helmholtz instability of the rising sheet. The principal effect is the reduction of the small centrifugal force on an element of fluid responding to the Coriolis force. The result is that a substantially steeper ambient superadiabatic temperature gradient is required if the rising fluid is not to be cut off by the ambient hydrostatic pressure. This result suggests the theoretical possibility that there may be substantial activity of buoyant flux bundles in the lower convective zone that is prevented from showing itself at the visible surface of the Sun. Title: Subrahmanyan Chandrasekhar, 19 October 1910 - 21 August 1995. Authors: Parker, E. N. Bibcode: 1995PhT....48k.106P Altcode: No abstract at ADS Title: Theoretical Properties of the Omega -Loops in the Convection Zone of the Sun. IV. Stability of Updrafts Authors: Parker, E. N. Bibcode: 1995ApJ...448..942P Altcode: This paper treats the Kelvin-Helmholtz instability of a two-dimensional stream of fluid simulating the convective updraft described in the two previous papers. It appears that the instability is strong enough by itself to dismember at least the upper end of a columnar updraft extending up from the bottom of the convective zone. On the other hand, the tension in the vertical legs of accumulated Ω-loops may suppress the instability in the upper portion of the updraft if the magnetic field is in an intense fibril state. The eddy viscosity of the ambient convection may be as large as 1013 cm2 s-1, in which case it too may stabilize the updraft to some degree. In conclusion, it appears that the updraft may be sufficiently stable to be recognizable as a coherent dynamical form, thereby fulfilling the observational requirement that the Ω-loops emerge through a localized (and only slowly shifting) site at the visible surface. The coherence over the height of the convective zone is the basis for the conjecture that the updraft, created by successive emerging Ω-loops, is the principal cause of the enhancement of solar irradiance during periods of high solar activity. Title: Physics of the Sun: The Ultimate Challenge to Astrophysics Authors: Parker, E. N. Bibcode: 1995SPD....26.1212P Altcode: 1995BAAS...27..985P No abstract at ADS Title: Theoretical Properties of Omega -Loops in the Convective Zone of the Sun. III. Extended Updrafts Authors: Parker, E. N. Bibcode: 1995ApJ...442..405P Altcode: It was pointed out in an earlier paper that the continuing emergence of Omega-loops at localized sites on the surface of the Sun indicates a continuing updraft at those sites. The updraft evidently extends all the way from the base of the convective zone to somewhat near (approximately 109cm) the surface. We pointed out that such updrafts enhance the convective heat transport to the surface, accounting for a major part of the increased solar brightness or irradiance during times of solar activity. The problem is to work out, as much as possible, the dynamical nature of the extended updrafts, initiated as the wakes of successive rising Omega-loops and driven thereafter by the convective forces. The question is, does the updraft take on a long-lived columnar form of its own, or does it never devlop beyond a sequence of rising wakes, resembling beads on a string? The dynamics of a columnar updraft is complicated by both the large Reynolds number and the strong stratication of the atmosphere, and by a total lack of direct observational information. Extended slender updrafts are not a spontaneous occurrence in numerical simulations of thermal convection in a stratified atmosphere, although slender concentrated downdrafts commonly occur. This paper examines several aspects of a columnar updrft in a convective atmosphere under various idealized circumstances to investigate to what extent that state can be maintained against the diminishing vorticity and expansion in the updraft. It appears that the successive passage of Omega-loops from the bottom to the top of the convective zone is an essential feature of the continuing existence of the updraft. Title: Theoretical Properties of Omega -Loops in the Convective Zone of the Sun. II. The Origin of Enhanced Solar Irradiance Authors: Parker, E. N. Bibcode: 1995ApJ...440..415P Altcode: The brightness of the Sun is observed to vary by 0.2% with the 11 yr activity cycle. We suggest that the brightness increase with magnetic activity is a direct result of the enhanced heat transport provided by the vertical wakes of the successive Omega-loops of magnetic field that produce the activity. The dynamics of a vertical wake in a stratified atmosphere is relatively complicated, but the observed rapid succession of emergence of Omega-loops at a localized site in the middle of a bipolar active region can be understood only if an established concentrated updraft extends up from the bottom of the convective zones. It is these updrafts that we suggest are the major cause of the brightness enhancement. The next paper examines some of the dynamical characteristics of vertical wakes. Title: GONG and The Solar Dynamo Authors: Parker, E. N. Bibcode: 1995ASPC...76....3P Altcode: 1995gong.conf....3P No abstract at ADS Title: The Magnetic Field of the Galaxy Authors: Parker, E. N. Bibcode: 1995fras.conf..115P Altcode: No abstract at ADS Title: Vital phase of space science Authors: Parker, E. N. Bibcode: 1994JGR....9919155P Altcode: Space science began with the indirect phase where the activity in space was inferred from such terrestrial phenomena as geomagnetic storms, ionospheric variations, and fluctuations in the cosmic ray intensity. The direct phase was initiated with spaceflight placing instruments directly in space and permitting the direct observation of UV and X rays, as well as precision observations of solar luminosity variations. The evidence from these many direct studies, together with the historical record of terrestrial conditions, shows that the variations of the luminosity of the Sun affect the terrestrial atmosphere at all levels, with devastating changes in climate tracking the major changes in the activity level and luminosity of the Sun. The quantification and understanding of this vital connection should be the first priority of space science and geophysics, from oceans and atmosphere through the ionosphere, magnetosphere, and all the way to the convective zone of the Sun. It becomes the vital phase of space science, focused on the basic science of the changing habitability of Earth. Title: Theoretical Properties of Omega -Loops in the Convective Zone of the Sun. I. Emerging Bipolar Magnetic Regions Authors: Parker, E. N. Bibcode: 1994ApJ...433..867P Altcode: It is proposed that the observed 500 G intensity of the magnetic fields emerging through the surface of the Sun can be understood from the Bernoulli effect in the upwelling Omega-loops of magnetic field. It is also proposed that the inferred 105 G azimuthal flux bundles below the base of the convective zone can be understood as a consequence of the large-scale buoyancy associated with the upwelling fluid in and around the rising Omega-loop. The process fits in naturally with the Babcock-Leighton form of the solar alpha-omega-dynamo. The emerging Omega-loop implies the coherence of the upwelling all the way from the bottom of the convective zone, enhancing the convective heat transport to account for the observed variation of the solar irradiance by about two parts in 103. Title: Comments and Perspectives Authors: Parker, E. N. Bibcode: 1994ASPC...68..413P Altcode: 1994sare.conf..413P No abstract at ADS Title: Origins of the Solar Magnetic Field Authors: Parker, E. N. Bibcode: 1994smf..conf...94P Altcode: No abstract at ADS Title: Summary comments Authors: Parker, E. N. Bibcode: 1994seit.conf..527P Altcode: No abstract at ADS Title: Replacement Concepts for Turbulent Diffusion of Magnetic Fields in Stars and Galaxies Authors: Parker, E. N. Bibcode: 1994ASIC..422..123P Altcode: 1994coma.conf..123P No abstract at ADS Title: Theoretical Interpretation of Magnetic Activity Authors: Parker, E. N. Bibcode: 1994svsp.coll..264P Altcode: 1994IAUCo.143P.264P No abstract at ADS Title: Spontaneous current sheets in magnetic fields : with applications to stellar x-rays Authors: Parker, Eugene Newman Bibcode: 1994ISAA....1.....P Altcode: 1994QB529.P36...... Expanding upon the ideas first proposed in his seminal book Cosmical Magnetic Fields , Eugene N. Parker here offers the first in-depth treatment of the magnetohydrodynamic theory of spontaneous magnetic discontinuities. In detailing his theory of the spontaneous formation of tangential discontinuities (current sheets) in a magnetic field embedded in highly conducting plasma, Parker shows how it can be used to explain the activity of the external magnetic fields of planets, stars, interstellar gas clouds, and galaxies, as well as the magnetic fields in laboratory plasmas. Provocative and fascinating, Spontaneous Current Sheets in Magnetic Fields presents a bold new theory that will excite interest and discussion throughout the space physics community. Title: Anomalous Resistivity and the Evolution of Magnetic Field Topology Authors: Parker, E. N. Bibcode: 1993ApJ...414..389P Altcode: This paper explores the topological restructuring of a force-free magnetic field caused by the hypothetical sudden onset of a localized region of strong anomalous resistivity. It is shown that the topological complexity increases, with the primitive planar force-free field with straight field lines developing field lines that wrap half a turn around each other, evidently providing a surface of tangential discontinuity in the wraparound region. It is suggested that the topological restructuring contributes to the complexity of the geomagnetic substorm, the aurora, and perhaps some of the flare activity on the sun, or other star, and the Galactic halo. Title: A Solar Dynamo Surface Wave at the Interface between Convection and Nonuniform Rotation Authors: Parker, E. N. Bibcode: 1993ApJ...408..707P Altcode: A simple dynamo surface wave is presented to illustrate the basic principles of a dynamo operating in the thin layer of shear and suppressed eddy diffusion beneath the cyclonic convection in the convection zone of the sun. It is shown that the restriction of the shear delta(Omega)/delta(r) to a region below the convective zone provides the basic mode with a greatly reduced turbulent diffusion coefficient in the region of strong azimuthal field. The dynamo takes on the character of a surface wave tied to the lower surface z = 0 of the convective zone. There is a substantial body of evidence suggesting a fibril state for the principal flux bundles beneath the surface of the sun, with fundamental implications for the solar dynamo. Title: Resistive Dissipation and Magnetic Field Topology in the Stellar Corona Authors: Parker, E. N. Bibcode: 1993ApJ...407..342P Altcode: Tangential discontinuities, or current sheets, in a magnetic field embedded in a fluid with vanishing resistivity are created by discontinuous fluid motion. Tangential discontinuities are also created when a magnetic field is allowed to relax to magnetostatic equilibrium after mixing by fluid motions (either continuous or discontinuous) into any but the simplest topologies. This paper shows by formal examples that the current sheets arising solely from discontinuous fluid motions do not contribute significantly to the dissipation of magnetic free energy when a small resistivity is introduced. Dissipation that is significant under coronal conditions occurs only by rapid reconnection, which arises when, and only when, the current sheets are required by the field topology. Hence it is topological dissipation that is primarily responsible for heating tenuous coronal gases in astronomical settings, whether the fluid displacements of the field are continuous or discontinuous. Title: On the Generation of ``Strong'' Magnetic Fields Authors: Vainshtein, S. I.; Parker, E. N.; Rosner, R. Bibcode: 1993ApJ...404..773V Altcode: We rediscuss the nature of magnetic field generation in astrophysical systems. We show that as a result of ineffective three-dimensional turbulent diffusion in the presence of strong azimuthal magnetic fields, the standard dynamo equations are not likely to provide a reasonable description of magnetic dynamos in systems such as late-type stars and galaxies. Instead, we propose a new set of dynamo equations, which take into account the modifications of turbulent diffusion by strong magnetic fields. Title: Galactic cosmic rays and galactic halo X-ray emission Authors: Parker, Eugene N. Bibcode: 1993cac..book....3P Altcode: No abstract at ADS Title: Fast Dynamos, Cosmic Rays, and the Galactic Magnetic Field Authors: Parker, E. N. Bibcode: 1992ApJ...401..137P Altcode: It is suggested here that the dynamo believed to be responsible for the magnetic field of the Galaxy is a fast dynamo due to the dynamical reconnection of the azimuthal field of the Galaxy as the field is deformed by the instability of the gaseous disk and the rapid inflation of magnetic lobes by the cosmic-ray gas to form the Galactic halo. The reconnection of adjacent lobes carries out both the alpha effect and field dissipation essential for the existence of the Galactic alpha-omega dynamo. The azimuthal field is generated primarily in the gaseous disk, while the alpha effect is carried out in the halo. Title: Electron and Nuclear Counters Authors: Parker, Eugene N.; Korff, Serge Bibcode: 1992NYASA..65...30P Altcode: No abstract at ADS Title: Vortex Attraction and the Formation of Sunspots Authors: Parker, E. N. Bibcode: 1992ApJ...390..290P Altcode: A downdraft vortex ring in a stratified atmosphere exhibits universal attraction for nearby vertical magnetic flux bundles. It is speculated that the magnetic fields emerging through the surface of the sun are individually encircled by one or more subsurface vortex rings, providing an important part of the observed clustering of magnetic fibrils to form pores and sunspots. Title: The X Ray Corona, the Coronal hole, and the Heliosphere Authors: Parker, E. N. Bibcode: 1992JGR....97.4311P Altcode: The X ray emission from the Sun arises primarily from the gas trapped in the bipolar magnetic fields of both small and large active regions. It appears that the trapped gas is heated by the intermittent dissipation of magnetic energy (nanoflares) at the current sheets that arise spontaneously in any magnetic field subject to continuous deformation. The solar wind issues from regions of weak field pushed open by the expanding corona. Most of the heat input is close to the Sun, in the first 1-2 RS, raising the gas slowly out through the gravitational field and gradually accelerating it through the speed of sound at a distance of perhaps 3-5 RS. The waves generated by photospheric convection dissipate only at distances of 5 RS and beyond, where their heat input and momentum accelerate the wind to the high velocities of 600-800 km/s sometimes observed. The only source for the principle heat input close to the Sun appears to be the network activity, as suggested by Martin, Porter, and Moore. Thus the mass loss and the formation of the heliosphere are primarily a consequence of the smallest-scale activity supplemented by occasional flares and coronal mass ejections. The X ray emission is largely a consequence of the smallest flares, the nanoflares, supplemented by occasional X ray bursts from large flares. It is presumed that the mass loss and associated circumstellar spheres and the X ray emission from most other stars arise in the same manner, although there is no possibility for detailed observation, of course. Title: Heating coronal holes and accelerating the solar wind Authors: Parker, E. N. Bibcode: 1992sws..coll...79P Altcode: The special energy requirements of a coronal hole combined with current knowledge of the limited dissipation of Alfven and fast mode MHD waves in the solar corona suggest a unique source of heat for the coronal hole. The near coronal hole requires approximately 3 - 4 x 10 exp 5 ergs/sq cm s, which can come only from the fluid jets, fast particles, and short period MHD waves from the network activity. The high speed streams of solar wind from coronal holes show that there is substantial heating, of 1 - 2 x 10 exp 5 ergs/sq cm s, beyond the sonic point in the wind, which can come only from the dissipation by thermal conduction of long period (approximately equal or greater than 100 sec) MHD waves from subphotospheric convection. Although the Alfven wave flux from the photosphere is generally taken for granted in the literature, we point out that it is a crucial phenomenon that has yet to be established on either a theoretical or observational scientific basis. Title: The Sunspot Phenomenon - a Commentary Authors: Parker, E. N. Bibcode: 1992ASIC..375..413P Altcode: 1992sto..work..413P The current knowledge of the sunspot phenomenon is summarized, and some of the unanswered questions are identified. It is noted that the reason for the formation of sunspots remains the basic unanswered question. Attention is given to background considerations, formation of sunspots, the penumbra phenomenon, sunspot structure, and general theoretical problems. Title: Dynamical Buoyancy of Hydrodynamic Eddies Authors: Parker, E. N. Bibcode: 1991ApJ...380..251P Altcode: The dynamical pressure reduction within a vortex tube produces both a tension along the tube and a general buoyancy, analogous to magnetic flux tubes. The dynamical buoyancy causes convective cells to rise at speeds comparable to the rms fluid velocity within the cell. Consequently, the convective cells in a stratified atmosphere are more active than indicated by the standard anelastic approximation. The coherent convective cells at each level actively crowd upward into the convective cells above, elbowing weaker cells out of the way and flattening themselves and others against the upper surface of the convective region. These effects can be seen in the recent SOUP observations of the solar granulation. Deeper in the convective zone the inhomogeneity of the buoyancy may explain the random character of the convective motions that turns up in recent numerical simulations. Title: The optical analogy for vector fields Authors: Parker, E. N. Bibcode: 1991PhFlB...3.2652P Altcode: This paper develops the optical analogy for a general vector field. The optical analogy allows the examination of certain aspects of a vector field that are not otherwise readily accessible. In particular, in the cases of a stationary Eulerian flow v of an ideal fluid and a magnetostatic field B, the vectors v and B have surface loci in common with their curls. The intrinsic discontinuities around local maxima in absolute values of v and B take the form of vortex sheets and current sheets, respectively, the former playing a fundamental role in the development of hydrodyamic turbulence and the latter playing a major role in heating the X-ray coronas of stars and galaxies. Title: Space plasma and its origin at the sun Authors: Parker, E. N. Bibcode: 1991PhFlB...3.2367P Altcode: This paper provides a concise review of the large picture of space plasmas, concentrating on the heliosphere and the origin of the X-ray corona and coronal hole at the sun. It is tentatively suggested that the active X-ray corona is heated primarily by the dissipation of magnetic energy at the spontaneous tangential discontinuities (current sheets) in the confining bipolar magnetic fields of active regions. The discontinuities arise because of the continuous mapping of the footpoints of the field by the photospheric convection. The coronal holes appear to be heated by a combination of Alfven waves, providing the high-speed streams in the solar wind, and the microflaring in the small-scale network fields. Title: The Magnetic Field of the Galaxy Authors: Parker, E. N. Bibcode: 1991ICRC....5...35P Altcode: 1991ICRC...22e..35P No abstract at ADS Title: The Phase Mixing of Alfven Waves, Coordinated Modes, and Coronal Heating Authors: Parker, E. N. Bibcode: 1991ApJ...376..355P Altcode: Phase mixing has been a popular theoretical mechanism invoked to dissipate the photospheric plane shear Alfven waves hypothesized to penetrate up into the coronal hole and solar wind, thereby maintaining the expanding coronal gas at 1.5 million K and serving as the principal energy source for the solar wind. However, phase mixing requires an ignorable coordinate, which is not available in the presumably filamentary coronal hole. The filamentary density and temperature of the coronal hole couple the waves into a coordinated mode with a unique phase velocity omega/k, which provides the other popular theoretical mechanism, viz, resonant absorption where the local Alfven speed C is equal to omega/k. This provides coronal heating at radial distances O(10 solar radii), where it serves to accelerate the solar wind to high velocity. But it does not provide the principal heat input in the first 1-2 solar radii, required by Withbroe's (1988) analysis of the observed structure of the coronal hole. Title: Heating Solar Coronal Holes Authors: Parker, E. N. Bibcode: 1991ApJ...372..719P Altcode: It has been shown that the coronal hole, and the associated high-speed stream in the solar wind, are powered by a heat input of the order of 500,000 ergs/sq cm s, with most of the heat injected in the first 1-2 solar radii, and perhaps 100,000 ergs/sq cm s introduced at distances of several solar radii to provide the high speed of the issuing solar wind. The traditional view has been that this energy is obtained from Alfven waves generated in the subphotospheric convection, which dissipate as they propagate outward, converting the wave energy into heat. This paper reviews the generation of waves and the known wave dissipation mechanisms, to show that the necessary Alfven waves are not produced under the conditions presently understood to exist in the sun, nor would such waves dissipate significantly in the first 1-2 solar radii if they existed. Wave dissipation occurs only over distances of the order of 5 solar radii or more. Title: Convection, Spontaneous Discontinuities, and Stellar Winds and X-Ray Emission. (Karl Schwarzschild Lecture 1990) Authors: Parker, E. N. Bibcode: 1991RvMA....4....1P Altcode: No abstract at ADS Title: Micro/Nanoflare Coronal Heating (With 8 Figures) Authors: Parker, E. N. Bibcode: 1991mcch.conf..615P Altcode: No abstract at ADS Title: Intrinsic magnetic discontinuities and solar X-ray emission Authors: Parker, E. N. Bibcode: 1990GeoRL..17.2055P Altcode: The fundamental theorem of magnetostatic equilibrium predicts that the bipolar magnetic fields of active regions on the Sun contain tangential discontinuities as an intrinsic part of their equilibrium. It appears that rapid reconnection at these many tangential discontinuities (nanoflares) is the primary source of heat that produces the X-ray emitting corona. The X-ray corona Is then a cloud of nanoflares. Title: The solar probe mission Authors: Feldman, W. C.; Anderson, J.; Bohlin, J. D.; Burlaga, L. F.; Farquhar, R.; Gloeckler, G.; Goldstein, B. E.; Harvey, J. W.; Holzer, T. E.; Jones, W. V.; Kellogg, P. J.; Krimigis, S. M.; Kundu, M. R.; Lazarus, A. J.; Mellott, M. M.; Parker, E. N.; Rosner, R.; Rottman, G. J.; Slavin, J. A.; Suess, S. T.; Tsurutani, B. T.; Woo, R. T.; Zwickl, R. D. Bibcode: 1990AIPC..203..101F Altcode: 1990pacr.rept..101F The Solar Probe will deliver a 133.5 kg science payload into a 4 Rs perihelion solar polar orbit (with the first perihelion passage in 2004) to explore in situ one of the last frontiers in the solar system-the solar corona. This mission is both affordable and technologically feasible. Using a payload of 12 (predominantly particles and fields) scientific experiments, it will be possible to answer many long-standing, fundamental problems concerning the structure and dynamics of the outer solar atmosphere, including the acceleration, storage, and transport of energetic particles near the Sun and in the inner (<65 Rs) heliosphere. Title: Solar and stellar coronae Authors: Parker, E. N. Bibcode: 1990AdSpR..10i..17P Altcode: 1990AdSpR..10...17P A review of the observational facts of the X-ray corona of the sun suggests that the dissipation of waves plays at most a minor role in heating the corona. On the other hand, the random continuous shuffling and mixing of the footpoints of the bipolar magnetic fields, in which the X-ray corona resides, causes the spontaneous appearance of current sheets. Current sheets are highly dissipative, with a tendency to transient bursts of magnetic reconnection. Detailed observations show that the X-ray corona is made up of large numbers of small intense impulsive events of the same magnitude as expected from the bursts of reconnection. It appears, then, that it is the spontaneous current sheets that are the direct cause of the X-ray corona, driven by the continuous motions of the footpoints of the field in the photospheric convection. Title: The Magnetic Field of the Sun - an Object Lesson Authors: Parker, E. N. Bibcode: 1990IAUS..140....1P Altcode: The magnetic field of the sun is created by a magnetohydrodynamic dynamo under conditions bearing some qualitative similarities to the apparent generation of the Galactic field in the gaseous disk of the Galaxy. There is a similarity, too, in the extension of bipolar lobes of the solar field above the surface of the sun and the extension of bipolar lobes of the solar field above the surface of the sun and the extension of bipolar lobes of the Galactic field outward from both sides of the disk. The expected origin and activity of the galactic field can be studied by examining the behavior of the magnetic field of the sun. The origin of the solar magnetic field far below the surface can be investigated as can the theoretical origin of the Galactic field, where there is so little direct observation of the small scale motions and magnetic fields. The activity of the magnetic field of the sun, producing prominences, flares and X-ray corona, a solar wind, and coronal mass ejection, can all have counterparts in the activity of the Galactic field above the surface of the gaseous disk. Title: Bowie medal to Eugene N. Parker; Citation and reply Authors: Jokipii, J. R.; Parker, E. N. Bibcode: 1990EOSTr..71..783J Altcode: On May 30, 1990, at the Spring Meeting in Baltimore, Md., AGU honored Eugene N. Parker of the University of Chicago with its most prestigious award, the William Bowie Medal. The annual award is given for outstanding contributions to fundamental geophysics and for unselfish cooperation in research. The award citation and Parker's response are presented below. Title: Spontaneous Discontinuities in Galactic Magnetic Fields and the Creation of Galactic X-Ray Halos Authors: Parker, E. N. Bibcode: 1990IAUS..140..169P Altcode: The magnetic field in the gaseous disk of the Galaxy is dynamically unstable to undulations with wavelenghts of the order of 1 kpc. The elevated portions of the field are subject to rapid inflation (of about 5 km/sec) by the cosmic rays produced within the gaseous disk. The result is a magnetic halo of 1-3 x 10 to the -6th gauss, composed of close packed bipolar lobes of field extending outward from the surface of the disk to distances of several kpc. The inflation is presumably irregular, producing tangential discontinuities (current sheets) throughout the extended bipolar fields. A major portion of the magnetic energy is dissipated by rapid reconnection at these current sheets, heating the tenuous halo gas to temperatures of 10 to the 6th to 10 to the 7th K and producing the X-ray emission observed from the halos of many spiral galaxies. Title: The basic magnetostatic theorem. Authors: Parker, E. N. Bibcode: 1990ppst.conf....3P Altcode: The purpose of this paper is to familiarize the reader with a basic theorem of magnetohydrodynamics, that tangential discontinuities (current sheets) are an intrinsic part of the magnetostatic equilibrium of all but the simplest field topologies. A tangential discontinuities here refers to a surface (flux surface) across which the magnitude of the field is continuous but the direction is not. This theorem can be applied to the theory of heating the solar corona. Title: The cause of the solar X-ray corona. Authors: Parker, E. N. Bibcode: 1990ppst.conf...63P Altcode: This lecture takes a critical look at the cause of the active X-ray corona of the Sun to determine how this remarkable suprathermal phenomenon is produced. The traditional ideas run into serious quantitative difficulty when confronted with observation. The theoretical considerations suggest that the active X-ray corona is maintained largely by many small reconnection events in the tangential discontinuities that arise spontaneously in the bipolar magnetic fields. Alfvén waves are undoubtedly present in the bipolar fields, but their total contribution to the energy input to the active corona is, evidently, minor. Title: Tangential discontinuities and the optical analogy for stationary fields. VII. Effects of resistivity Authors: Parker, E. N. Bibcode: 1990GApFD..55..161P Altcode: The relatively large resistivity in the solar photosphere and chromosphere softens the ideal tangential discontinuities of magnetostatic equilibrium into continuous transitions in field direction over scales of 0.1-10 km. This softening is communicated upward at the Alfvén speed into the active solar corona. The degree of softening is a vital part of the theory of magnetic heat input to the active X-ray corona, because the very low resistivity of the coronal gas provides effective dissipation only if the current sheets are reduced to a thickness of 10-2km. A close examination of the problem shows that the Alfvén transit time up into the corona is large compared to the characteristic time of 1 sec in which the coronal tangential discontinutities are formed. It also shows that the principal effect of the resistivity is to create a thin surface layer of fluid on adjacent flux bundles, which causes a general drift of the flux but does not directly broaden the current sheets higher up in the field. In fact the motions of the surface layers do not extend upwards beyond the first winding pattern at each end of a coronal loop. It appears that the photospheric and chromospheric resistivity is without striking consequences for magnetic heating in the corona. Title: Spontaneous tangential discontinuities and the optical analogy for static magnetic fields. VI. Topology of current sheets Authors: Parker, E. N. Bibcode: 1990GApFD..53...43P Altcode: The electric surface current in a tangential discontinuity in a force-free magnetic field is conserved. The direction of the current is halfway between the direction of the continuous fields on either side of the surface of discontinuity. Hence the current sheets, i.e. the surface of tangential discontinuity, have a topology that is distinct from the lines of force of the field. The precise nature of the topology of the current sheet depends upon the form of the winding patterns in the field. Hence, invariant winding patterns and random winding patterns are treated separately. Current sheets may have edges, at the junction of two or more topological separatrices. The current lines may, in special cases, be closed on themselves. The lines of force that lie on either side of a current sheet somewhere pass off the sheet across a junction onto another sheet. In most cases the current sheets extending along a field make an irregular honeycomb. The honeycomb pattern varies along the field if the winding pattern of the field varies. The surface current density in a tangential discontinuity declines inversely, or faster, with distance from its region of origin. The edges of weaker tangential discontinuities (originating in more distant regions) are bounded by the stronger tangential discontinuities (of nearby origin). An examination of the force-free field equations in a small neighborhood of the line of intersection of two tangential discontinuities shows that the lines of force twist around to cross the line of intersection at right angles. If the angle between the tangential discontinuities exceeds /2, there is also the possibilitity that the lines twist around so as to come tangent to the line of intersection as they cross it. Title: Tangential discontinuities and the optical analogy for stationary fields. v. formal integration of the force-free field equations Authors: Parker, E. N. Bibcode: 1990GApFD..52..183P Altcode: This paper demonstrates the appearance of tangential discontinuities in deformed force-free fields by direct integration of the field equation x B = B. To keep the mathematics tractable the initial field is chosen to be a layer of linear force-free field Bx = + B0cosqz, By = - B0sinqz, Bz = 0, anchored at the distant cylindrical surface π = (x2 + y2)1/2 = R and deformed by application of a local pressure maximum of scale l centered on the origin x = y = 0. In the limit of large R/l the deformed field remains linear, with α = q[1 + O(l2/R2)]. The field equations can be integrated over π = R showing a discontinuity extending along the lines of force crossing the pessure maximum. On the other hand, examination of the continuous solutions to the field equations shows that specification of the normal component on the enclosing boundary π = R completely determines the connectivity throughout the region, in a form unlike the straight across connections of the initial field. The field can escape this restriction only by developing internal discontinuities.

Casting the field equation in a form that the connectivity can be specified explicitly, reduces the field equation to the eikonal equation, describing the optical analogy, treated in papers II and III of this series. This demonstrates the ubiquitous nature of the tangential discontinuity in a force-free field subject to any local deformation. Title: Tangential discontinuities and the optical analogy for stationary fields IV. High speed fluid sheets Authors: Parker, E. N. Bibcode: 1990GApFD..50..229P Altcode: It was shown in the previous paper that a sufficiently strong pressure maximum applied to an equilibrium flux surface, by the fields on either side of the surface, produces a gap in the flux surface. The fields on either side make contact through the gap to produce a surface of tangential discontinuity (current sheet). It is shown in the present paper that there is a high speed sheet of fluid and field sliding over the surface of discontinuity when the applied pressure moves slowly across the flux surface. Conditions in the active X-ray corona of the sun suggest that such sheets are generally present, with velocities of the order of 102 km/sec, but with thicknesses too small to be observed. More substantial high speed sheets of fluid may occur in solar flares. Title: Intermittent Behavior of Galactic Dynamo Activities Authors: Ko, C. M.; Parker, E. N. Bibcode: 1989ApJ...341..828K Altcode: Recent observations by Beck and Golla of far-infrared and radio continuum emission from nearby spiral galaxies suggest that the galactic magnetic field strength is connected to the current star formation rate. The role of star formation on the generation of large-scale galactic magnetic field is studied in this paper. Using a simple galactic model, it is shown how the galactic dynamo depends strongly on the turbulent velocity of the interstellar medium. When the star formation efficiency is high, the ISM is churned which in turn amplifies the galactic magnetic field. Between active star formation epochs, the magnetic field is in dormant state and decays at a negligible rate. If density waves trigger star formation, then they also turn on the otherwise dormant dynamo. Title: Solar and Stellar Magnetic Fields and Atmospheric Structures - Theory Authors: Parker, E. N. Bibcode: 1989SoPh..121..271P Altcode: 1989IAUCo.104..271P This presentation reviews selected ideas on the origin of the magnetic field of the Sun, the dynamical behavior of the azimuthal field in the convective zone, the fibril state of the field at the photosphere, the formation of sunspots, prominences, the spontaneous formation of current sheets in the bipolar field above the surface of the Sun, coronal heating, and flares. Title: Tangential discontinuities and the optical analogy for stationary fields III. Zones of exclusion Authors: Parker, E. N. Bibcode: 1989GApFD..46..105P Altcode: This paper presents a number of formal examples of the bifurcation of individual flux surfaces by the pressure maxima imposed by the fields on either side. An approximate necessary and sufficient criterion for the convexity of the pressure maximum is provided, with application to fields with and without gaps in their flux surfaces. Gaps automatically produce tangential discontinuities in almost all cases, by permitting fields otherwise separated by finite distance to come in contact. Both Euclidean and non Euclidean flux surfaces are examined, showing that positive curvature fosters the formation of gaps while negative curvature opposes it. The special conditions for producing single or double gaps are pointed out. The general conditions for producing gaps are so mild as to indicate the special character of the familiar continuous solutions to the force-free equilibrium equations, in which the maxima and minima of the field pressure are so arranged as to provide flux surfaces without gaps. Title: Spontaneous tangential discontinuities and the optical analogy for static magnetic fields. I. Force-free fields, potential fields, and discontinuities Authors: Parker, E. N. Bibcode: 1989GApFD..45..159P Altcode: The lines of force of a magnetic field extending through an infinitely conducting fluid between footpoints on the planes z=0 and z=L can be wrapped and interwoven by bounded continuous motions of the footpoints into a random sequence of arbitrary topological patterns along the field. The sign of the topological helicity of the winding pattern of the field vanes at random along the field. On the other hand, in force-free equilibrium the relative helicity (=B. B/B2) is rigorously constant along each line of force. Indeed in the limit of an endless random sequence of independent winding patterns along the field, the helicity falls asymptotically to zero and the field becomes curl free. A field with constant helicity along each line of force is obliged to create internal tangential discontinuities (in which the sign of the curl and the helicity is arbitrary) if it is to follow the varying topological helicity imposed by the twists and turns of the succession of independent winding patterns. Title: Tangential discontinuities and the optical analogy for stationary fields II. The optical analogy Authors: Parker, E. N. Bibcode: 1989GApFD..45..169P Altcode: It is shown that any stationary three-dimensional velocity field or magnetic field is a potential field in the two dimensional subspace of the Bernoulli surfaces S(Q) or isobaric surfaces S(p), respectively. From this it is shown that the streamlines and the lines of force follow the optical ray paths in S(Q) and S(p) for indices of refraction v and B, respectively. This formal analogy shows how the lines are refracted by variations of the pressure applied by the fluid and field on either side. In particular, it is shown how continuous variations of the pressure produce discontinuities (bifurcations) in the field, forming tangential discontinuities. Title: Nanoflares and the Solar X-Ray Corona Authors: Parker, E. N. Bibcode: 1988ApJ...330..474P Altcode: Observations of the sun with high time and spatial resolution in UV and X-rays show that the emission from small isolated magnetic bipoles is intermittent and impulsive, while the steadier emission from larger bipoles appears as the sum of many individual impulses. We refer to the basic unit of impulsive energy release as a nanoflare. The observations suggest, then, that the active X-ray corona of the sun is to be understood as a swarm of nanoflares. This interpretation suggests that the X-ray corona is created by the dissipation at the many tangential discontinuities arising spontaneously in the bipolar fields of the active regions of the sun as a consequence of random continuous motion of the footpoints of the field in the photospheric convection. The quantitative characteristics of the process are inferred from the observed coronal heat input. Title: Dynamical Oscillation and Propulsion of Magnetic Fields in the Convective Zone of a Star. V. Instability and Propulsion of Flux Bundles Authors: Parker, E. N. Bibcode: 1988ApJ...326..395P Altcode: Simple analysis of the hydrodynamics initiated by the presence of a coherent flux bundle in the lower half of the convective zone of a star like the Sun indicates that bundles with diameters comparable to the local pressure scale height (∼5 x 109 cm) are subject to sidewise motions perhaps as fast as 103 cms-1. The motions arise as a consequence of the bundle being squeezed between the cool shadow above and the accumulating heat below, and because of convective propulsion. This suggests that the equatorward motion (102 cm s-1) of the azimuthal fields, inferred from observations of the Sun, may be as much a consequence of the hydrodynamics of flux bundles and meridional circulation as it is of the dynamo effects that create the flux. Title: Dynamical oscillation and propulsion of magnetic fields in the convective zone of a star. VI - Small flux bundles, network fields, and ephemeral active regions Authors: Parker, E. N. Bibcode: 1988ApJ...326..407P Altcode: Simple analysis of the hydrodynamics initiated by the presence of a coherent flux bundle in the lower half of the convective zone of a star like the Sun indicates that bundles with diameters comparable to the local pressure scale height (5 x 10 cm) are subject to sidewise motions perhaps as fast as 10 cm 51 The motions arise as a consequence of the bundle being squeezed between the cool shadow above and the accumulating heat below, and because of convective propulsion. This suggests that the equatorward motion (102 cm s1) of the azimuthal fields, inferred from observations of the Sun, may be as much a consequence of the hydrodynamics of flux bundles and meridional circulation as it is of the dynamo effects that create the flux. Subject headings: hydromagnetics - stars: interiors stars: magnetic Title: Dynamical Oscillation and Propulsion of Magnetic Fields in the Convective Zone of a Star. IV. Eruption to the Surface Authors: Parker, E. N. Bibcode: 1988ApJ...325..880P Altcode: It was shown in the previous paper that the heat accumulating beneath the azimuthal field in the convective zone of the sun initiates a Rayleight-Taylor instability, causing tongues of gas to intrude upward into the field. The present paper works out the conditions in an intruding tongue of gas, showing that it penetrates all the way through the field, emerging into the atmosphere above with a specific entropy significantly in excess of the ambient value. The entropy is large enough that the gas rises to the visible surface in 10 to the 6th s or less, where it produces a bipolar magnetic region. Once the eruption to the surface has carried away the accumulated hot gas below the field, there remains only the general downdraft which retracts the magnetic flux from the surface in a characteristic time of 10 to the 7th s. Title: The origins of the stellar corona. Authors: Parker, E. N. Bibcode: 1988sscd.conf....2P Altcode: This paper is a critical review of present observational facts and theoretical developments relating to the cause of the active X-ray corona and to the coronal holes of the sun and other late type stars. Title: Magnetic Monopole Plasma Oscillations and the Survival of Galactic Magnetic Fields Authors: Parker, E. N. Bibcode: 1987ApJ...321..349P Altcode: This paper explores the general nature of magnetic-monopole plasma oscillations as a theoretical possibility for the observed Galactic magnetic field in the presence of a high abundance of magnetic monopoles. The modification of the hydromagnetic induction equation by the monopole oscillations produces the half-velocity effect, in which the magnetic field is transported bodily with a velocity midway between the motion of the conducting fluid and the monopole plasma. Observational studies of the magnetic field in the Galaxy, and in other galaxies, exclude the half-velocity effect, indicating that the magnetic fields is not associated with monopole oscillations. In any case the phase mixing would destroy the oscillations in less than 100 Myr. The conclusion is that magnetic monopole oscillations do not play a significant role in the galactic magnetic fields. Hence the existence of galactic magnetic fields places a low limit on the monopole flux, so that their detection - if they exist at all - requires a collecting area at least as large as a football field. Title: The Dynamical Oscillation and Propulsion of Magnetic Fields in the Convective Zone of a Star. II. Thermal Shadows Authors: Parker, E. N. Bibcode: 1987ApJ...321..984P Altcode: The dynamics of thermal shadows which develop in the convective zone of a star around an insulating obstacle such as a horizontal band in intense magnetic field are studied. The depth of the shadow on the cool side of the obstacle is found to depend largely on the width of the obstacle multiplied by the temperature gradient. Thermal shadows pressing fields up to 10,000 G downward against the bottom of the convective zone are produced by the broad bands of the azimuthal field in the sun's convective zone. In the third part, the time-dependent accumulation of heat beneath a thermal barrier simulating such a band in the lower convective zone of the sun is considered. The resulting Rayleigh-Taylor instability is shown to cause tongues of heated gas to penetrate upward through the field, providing the emerging magnetic fields that give rise to the activity of the sun. Title: The Dynamical Oscillation and Propulsion of Magnetic Fields in the Convective Zone of a Star. III. Accumulation of Heat and the Onset of the Reyleigh-Taylor Instability Authors: Parker, E. N. Bibcode: 1987ApJ...321.1009P Altcode: This paper studies the time-dependent accumulation of heat beneath a thermal barrier simulating a broad band of intense azimuthal field in the lower convective zone of the Sun, or other star. The accumulating heat causes the gas density beneath the field to decline (Δρ/ρ = -ΔT/T) to the point that the gas is less dense than the gas within the magnetic field (where Δρ/ρ = -β2/8πp). The resulting Rayleigh-Taylor instability causes tongues of heated gas to penetrate upward through the field. We suggest that the tongues of hot gas take on the nature of thermal plumes, extending all the way to the surface, where they provide the emerging magnetic fields that give rise to the activity of the Sun. The whole process, beginning with the accumulation of heat, followed by the onset of the Rayleigh-Taylor instability, and the extension of tongues of hot gas into thermal plumes to the surface, is estimated to take a week or two, in agreement with the observed weekly emergence of thermal plumes and magnetic flux in activity complexes at the surface. Title: Stimulated dissipation of magnetic discontinuities and the origin of solar flares. Authors: Parker, E. N. Bibcode: 1987SoPh..111..297P Altcode: It is proposed that the principal cause of the confined solar flare is the dissipation of magnetic energy at the many small-scale pre-existing tangential dscontinuities in the local bipolar magnetic field. The discontinuities are a consequence of the continuous shuffling and intermixing of the footpoints of the bipolar field by the turbulent photospheric granules. The X-ray corona within the bipolar field is presumed to be a consequence of the continuing dissipation by reconnection at these discontinuities. A flare results when static deformation and/or internal agitation of the field stimulates the onset of rapid reconnection at the many small internal discontinuities. The discontinuities are partially exhausted by the flare, so that the post-flare X-ray emission of that particular loop is substantially below the pre-flare level for a period of some hours while the discontinuities are being rejuvenated. Title: Small-scale energy storage and release as the cause of the stellar X-ray corona. Authors: Parker, E. N. Bibcode: 1987NASCP2483...89P Altcode: 1987tphr.conf...89P It has yet to be established why ordinary stars possess X-ray coronas. Detailed observations of the Sun make it doubtful that the X-ray corona is produced by the dissipation of Alfven waves. The uniform X-ray brightness over all scales from 10,000 to 100,000 km simply does not look like a resonance phenomenon. It is demonstrated that the arbitrary winding patterns introduced into the bipolar magnetic fields of X-ray corona produce discontinuities within the field. It is suggested that the random motions of the footprints of the field cause the accumulation of internal strains in the field, which dissipate through neutral reconnection across the associated discontinuities to provide the primary heat source for the X-ray corona. It is emphasized, however, that the essential high resolution observations of the Sun have yet to be carried out, and until the theory is firmly established for the Sun, it cannot be known how to interpret the X-ray emission of the Sun or of the other stars. Title: Why do stars emit x rays? Authors: Parker, Eugene N. Bibcode: 1987PhT....40g..36P Altcode: Because X-ray emission is the principal means of energy loss from most stellar coronas, X-ray luminosity may be taken as a measure of the energy input needed to produce the corona. If, moreover, it were known why the sun is made to generate patches of bright X-ray corona, the X-ray emission could be used as a diagnostic tool for probing the properties of other stars. Attention is presently given to stars with surface temperatures below about 7000 K, such as the sun, to elucidate such phenomena as wrapping and interweaving of the magnetic lines of force in a bipolar magnetic region, the twisting of a single flux bundle in an otherwise uniform field, and future prospects being developed by NASA for more intensive study of solar X-ray processes. Title: Magnetic Reorientation and the Spontaneous Formation of Tangential Discontinuities in Deformed Magnetic Fields Authors: Parker, E. N. Bibcode: 1987ApJ...318..876P Altcode: This paper provides an explicit illustration of the formation of tangential discontinuities (current sheets) in a force-free magnetic field whose footpoints have been subjected to bounded continuous displacement and shuffling, so that the lines of force are wound about each other in complex but continuous patterns. The discontinuities appear spontaneously because of the reorientation of the field under the enhanced pressure where two regions of different field topology are pressed together by the general winding and wrapping. Title: The energy source of the interplanetary medium and the heliosphere. Authors: Parker, Eugene N. Bibcode: 1987NASCP2464...75P Altcode: 1987ess..nasa...75P The activity of the interplanetary medium arises from occasional transient outbursts of the active corona and, for the most part, from the interaction of fast and slow streams in the solar wind. The basic driver is the heat input to the corona, both transient and steady. The fast streams issue from coronal holes where the heat input may be Alfven waves with root mean squared (rms) fluid velocities of nearly 100 km/sec or may be wholly or in part the waves refracted into the hole from neighboring active regions. If the latter, then the character of the wind from the coronal hole depends upon the proximity and vigor of active regions, with significant differences between the polar and low altitude solar wind. In any case, there is no observational support for any of these ideas, so that the primary cause of the wind from the Sun, as well as any other similar star is not without mystery. It is to be hoped that ground-based observations together with the input from the Solar Optical Telescope and the International Solar Polar Mission may in time succeed in clearing up some of the basic questions. Title: The Dynamo Dilemma Authors: Parker, E. N. Bibcode: 1987SoPh..110...11P Altcode: The recent determination that the angular velocity Ω of the Sun declines downward through the convective zone raises serious questions about the nature of the solar dynamo. The principal qualitative features of the Sun are the azimuthal fields that migrate toward the equator in association with an oscillating poloidal field which reverses at about the time of maximum appearance of bipolar magnetic regions. If Ω decreases downward, or is negligible, the horizontal gradient in Ω produces a dynamo with some of these essential characteristics. There is reason to think that the dynamo is confined to the lower half of the convective zone where α has the opposite sign from the usual (α > 0 in the northern hemisphere) producing equatorward migration but reversing the sign of the associated poloidal field. Meridional circulation may play an essential role in shaping the dynamo. At the present time it is essential to measure Ω accurately and determine the nature of the meridional circulation. Title: The dynamical origin of active magnetic regions at the surface of theSun and other stars. Authors: Parker, E. N. Bibcode: 1987PBeiO...9....2P Altcode: No abstract at ADS Title: Magnetic Activity Complexes, Thermal Relaxation Oscillations, and the Dynamics of the Azimuthal Magnetic Field of a Star Authors: Parker, E. N. Bibcode: 1987ASSL..137..289P Altcode: 1987isav.symp..289P The large amount of magnetic flux cycling through an activity complex in a period of six months suggests that the azimuthal magnetic field in the convective zone of the Sun is not less than 3×103gauss and probably is considerable more. A field of 3 kilogauss or more has the effect of blocking the convective heat transport, producing a cool shadow above the azimuthal field and causing heat to accumulate below. The incremental weight of the cool shadow is sufficient to overpower the magnetic buoyancy, pressing the field against the bottom of the convective zone. The accumulation of heat underneath produces a thermal relaxation oscillation that erupts to the surface at intervals of the order of a week, supplying the intermittent emergence of magnetic flux observed in the activity complex. Title: The causes of the corona of a star. Authors: Parker, E. N. Bibcode: 1987PBeiO...9....7P Altcode: No abstract at ADS Title: The Dynamical Oscillation and Propulsion of Magnetic Fields in the Convective Zone of a Star. I. General Considerations Authors: Parker, E. N. Bibcode: 1987ApJ...312..868P Altcode: Observations of the sun show that the magnetic flux of the large activity complexes emerges in localized sites in brief bursts at intervals of many days or a few weeks. The quantity of flux arriving at the surface suggests that the mean aximuthal field of the sun in the lower convective zone is not less than 3000 G and may perhaps be considerably more. Such a field inhibits the convective transport of heat. Hence there is a cool shadow on the upper side of the field, and that cool shadow presses downward so hard as to suppress the magnetic buoyancy, forcing the field to remain in the lower convective zone. The accumulation of heat below the field forces intruding fingers of gas up through the field, forming thermal plumes extending up to the visible surface. It is suggested that the process is intermittent, providing a thermal relaxation oscillation with a period of the order of one week. The activity complexes observed at the surface are the consequence of these eruptions of fluid and entrained field from the lower convective zone. Title: Magnetic Nonequilibrium and Current Sheet Formation Authors: Vainshtein, S. I.; Parker, E. N. Bibcode: 1987sman.work..201V Altcode: This paper investigates the equilibrium of a cluster of long straight twisted magnetic flux tubes extending in the z-direction in a highly conducting fluid, subject to the boundary condition that the transverse component of the field (produced by the twisting) goes continuously to zero at the outer boundary of the flux tubes. It is shown that equilibrium requires that the length of the periphery of the tube remains invariant during any deformation of the tube. From this principle it is shown that there is equilibrium only for axial symmetry, i.e. only for a single twisted flux tube. These examples provide another perspective on the general absence of equilibrium, and consequent rapid dissipation, of any magnetic field subject to small-scale internal strains, such as the field extending outward from the convective zones of stars. Title: Heating of the stellar corona. Authors: Parker, E. N. Bibcode: 1986NASCP2442....9P Altcode: 1986copp.nasa....9P The present state of development of the theory of coronal heating is summarized. Coronal heating is the general cause of stellar X-ray emission, and it is also the cause of stellar mass loss in most stars. Hence a quantitive theory of coronal heating is an essential part of X-ray astronomy, and the development of a correct theory of coronal heating should be a primary concern of X-ray astronomers. The magnetohydrodynamical effects involved in coronal heating are not without interest in their own right, representing phenomena largely unknown in the terrestrial laboratory. Until these effects can be evaluated and assembled into a comprehensive theory of coronal heating for at least one star, the interpretation of the X-ray emissions of all stars is a phenomenological study at best, based on arbitrary organization and display of X-ray luminosity against bolometric luminosity, rotation rate, etc. The sun provides the one opportunity to pursue the exotic physical effects that combine to heat a stellar corona. Title: Stellar challenge Authors: Parker, Eugene N. Bibcode: 1986Natur.323..210P Altcode: No abstract at ADS Title: Book-Review - Physics of the Sun - V.I - the Solar Interior - V.II - the Solar Atmosphere - V.III - Astrophysics and Solar / Terrestrial Relations Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.; Parker, E. N. Bibcode: 1986Natur.323..210S Altcode: No abstract at ADS Title: Magnetic Nonequilibrium and Current Sheet Formation Authors: Vainshtein, S. I.; Parker, E. N. Bibcode: 1986ApJ...304..821V Altcode: This paper investigates the equilibrium of a cluster of long, straight, twisted magnetic flux tubes extending in the z-direction in a highly conducting fluid, subject to the boundary condition that the cluster is surrounded by a uniform pressure P. It is shown that there is equilibrium only for axial symmetry, i.e., only for a single twisted flux tube. Any more complicated cluster of twisted tubes is subject to nonequilibrium reconnection of the transverse component of the field. The example provides another perspective on the general absence of equilibrium, and consequent rapid dissipation, of any magnetic field subject to random small-scale internal strains, such as the fields extending outward from the convective zones of stars. Title: Present Knowledge, Problems and Questions concerning the Fibril Field of the Sun Authors: Parker, E. N. Bibcode: 1986ssmf.conf...13P Altcode: This paper reviews some of the dilemmas presently posed by the magnetic fields of the sun, particularly the intense fibril state of the field at the visible surface. The fibril state has been conjectured to extend throughout the convective zone, although there is now evidence to the contrary. It is the agitation of the fibrils that supplies the energy to heat the active X-ray corona, presumably through dissipation in the thin current sheets arising from the intermixing of the footpoints. The coronal holes are presumed to be heated by Alfvén waves from the general agitation of fibrils. The active motion of the fibrils is a fundamental datum in the theory of the stellar corona, and it is to be hoped that the motions can be determined by observation in the next few years. Title: Equilibrium of magnetic fields with arbitrary interweaving of the lines of force. I - Discontinuities in the torsion Authors: Parker, E. N. Bibcode: 1986GApFD..34..243P Altcode: Consideration is given to the static force-free equilibrium of a magnetic field in which all of the lines of force connect without knotting between parallel planes. The field is formed by continuous deformation from an initial uniform field, and is conventiently described in terms of the scalar function psi, which is the stream function for the incompressible wrapping and interweaving of the lines of force. Local compression and expansion of the lines of force is described in terms of the scalar function Phi. Equilibrium in the field requires satisfaction of two independent equations which cannot be accomplished without the full freedom of both psi and Phi. It is shown that discontinuities in the torsional characteristics of the lines occur when psi is predetermined by an arbitrary pattern. Discontinuities in the winding pattern of the lines can lead to discontinuities in the associated current sheets. Title: Equilibrium of magnetic fields with arbitrary interweaving of the lines of force. II. Discontinuities in the field. Authors: Parker, E. N. Bibcode: 1986GApFD..35..277P Altcode: The surfaces of discontinuity (SDs) identified by Parker (1986) in the torsion of a force-free magnetic field in an infinitely conducting fluid contained betweeen two fixed boundary planes are characterized analytically. It is shown that field discontinuities (current sheets) occur whenever an SD terminates within the fluid or intersects with another SD, that intersections occur in most cases, and that the resulting current sheets are responsible for most field dissipation in highly conducting fluids. The astrophysical implications of these findings and a number of unresolved problems are discussed. Title: The Magnetic Structure of Solar and Stellar Atmospheres Authors: Parker, E. N. Bibcode: 1986LNP...254..341P Altcode: 1986csss....4..341P No abstract at ADS Title: The magnetic structure of solar and stellar atmospheres Authors: Parker, E. N. Bibcode: 1986LNP...254..339P Altcode: This paper summarizes the present state of knowledge and understanding of the remarkable structure of the magnetic field of the one star where the structure can be observed. The discussion emphasizes several of the outstanding puzzles in the form of the field above and below the visible surface and provides a brief survey of present theoretical understanding, so far as it goes. Emphasis is given to the basic observational and theoretical work that remains before we have what might be called a theory of solar and stellar activity. Title: The Heliospheric Energy Source Authors: Parker, E. N. Bibcode: 1986ASSL..123...33P Altcode: 1986shtd.symp...33P The solar wind and the heliosphere exist as a consequence of the heat input to the corona, particularly the coronal holes. The necessary energy input to coronal holes has been estimated to be 10 to the 6th erg/sq cm sec, requiring Alfven waves with rms fluid velocities of 100 km/sec. Observational upper limits on coronal fluid velocities are of the order of 25 km/sec, which may not apply to the transparent coronal hole. Alternatively it has been suggested that coronal holes may be heated by agitation from neighboring active regions, suggesting that the vigor of a coronal hole depends upon its location. The Ulysses Mission will provide a direct comparison of the strength of the high speed wind from coronal holes at low latitude and coronal holes at high latitude, from which the nature of the presently unknown energy sources of the coronal holes and the resulting structure of the heliosphere may be better judged. The question is fundamental to the dynamics of the windspheres of all stars. Title: The Future of Solar Physics Authors: Parker, E. N. Bibcode: 1985SoPh..100..599P Altcode: The future of solar physics is founded on the existing fundamental unsolved problems in stellar physics. Thus, for instance, the physics of stellar interiors has been called into serious question by the very low-measured neutrino flux. The 71Ga neutrino detection experiment is the next step in unravelling this mystery. If that experiment should find the expected neutrino flux from the basic p-p reaction in the Sun, then astrophysics is in a difficult situation, because the most likely explanation for the low neutrino flux found in the 37Cl experiment would be an error in our calculation of the opacity or an error in our understanding of the elemental abundances in stellar interiors, with serious implications for present ideas on stellar structure and the age of the galaxy. Title: Stellar fibril magnetic systems. II - Two-dimensional magnetohydrodynamic equations. III - Convective counterflow Authors: Parker, E. N. Bibcode: 1985ApJ...294...47P Altcode: The dynamics of magnetic fibrils in the convective zone of a star is investigated analytically, deriving mean-field equations for the two-dimensional transverse motion of an incompressible fluid containing numerous small widely spaced circular cylinders. The equations of Parker (1982) are extended to account for the inertial effects of local flow around the cylinders. The linear field equation for the stream function at the onset of convection is then rewritten, neglecting large-scale heat transport, and used to construct a model of convective counterflow. The Kelvin impulse and fluid momentum, convective motion initiated by a horizontal impulse, and the effects of a viscous boundary layer are considered in appendices. Title: Stellar Fibril Magnetic Systems - Part Three - Convective Counterflow Authors: Parker, E. N. Bibcode: 1985ApJ...294...57P Altcode: The linearized equations of motion of a fibril magnetic field and the mean fluid motion through that field are used to illustrate the convective counterflow effect. The calculations show that starting from static equilibrium, a vertical impulse applied to a cluster of fibrils (represented by a cluster of parallel circular cylinders) may result in the fluid moving either upward or downward across the cluster, depending on the eccentricity of the cross section of the cluster and the strength of the aerodynamic drag coupling the fluid and fibrils. Specifically, a flattened cluster of fibrils, with a width in excess of twice the thickness, may be carried in the opposite direction from the initial applied impulse by the associated counter convective motion. It appears that this counterflow effect may operate in the upper few thousand km of the convective zone of the Sun, where it would play a role in suppressing the buoyant rise of magnetic flux tubes to the surface. Hence the convective counterflow may take an active part in controlling the emergence of flux tubes through the surface of a star like the Sun, perhaps regulating to some degree the form and general level of the activity of the star. Title: The vector structure of active magnetic fields Authors: Parker, E. N. Bibcode: 1985svmf.nasa....7P Altcode: Observations are needed to show the form of the strains introduced into the fields above the surface of the Sun. The longitudinal component alone does not provide the basic information, so that it has been necessary in the past to use the filamentary structure observed in Halpha to supplement the longitudinal information. Vector measurements provide the additional essential information to determine the strains, with the filamentary structure available as a check for consistency. It is to be expected, then, that vector measurements will permit a direct mapping of the strains imposed on the magnetic fields of active regions. It will be interesting to study the relation of those strains to the emergence of magnetic flux, flares, eruptive prominences, etc. In particular we may hope to study the relaxation of the strains via the dynamical nonequilibrium. Title: Heating the corona of the sun. Authors: Parker, E. N. Bibcode: 1985rbcc.conf..299P Altcode: The author suggests that coronal holes are heated by the dissipation of Alfvén waves. He also suggests that the active corona is heated by the random walk of the footpoints of the magnetic field, causing cumulative small-scale strains in the magnetic field. These quasi-static strains dissipate as a consequence of the absence of magnetostatic equilibrium for random topological distortions of the field, producing current sheets and neutral point reconnection. Title: Equilibrium of magnetic fields with arbitrary interweaving of the lines of force i. discontinuities in the torsion Authors: Parker, E. N. Bibcode: 1985GApFD..34..243P Altcode: This paper considers the static force-free equilibrium V×B=B of a magnetic field in which all of the lines of force connect without knotting between parallel planes. The field is formed by continuous deformation from an initial uniform field, and is conveniently described in terms of the scalar function , which is effectively the stream function for the incompressible wrapping and interweaving of the lines of force, and the scalar function , which describes the local compression and expansion. Equilibrium requires satisfaction of two independent equations (the third equation defines ), which cannot be accomplished without the full freedom of both functions and . It is shown by integration along the characteristics of the equilibrium equations that, when is predetermined by an arbitrary winding pattern, there appear discontinuities in . Discontinuities in have discontinuities in the field (i.e. current sheets) associated with them. We expect such discontinuities to be produced in the magnetic fields extending outward from the convecting surfaces of the cooler stars. Title: Solar Physics as Related to Stellar Physics Authors: Parker, E. N. Bibcode: 1985spit.conf...13P Altcode: No abstract at ADS Title: The vector structure of active magnetic fields. Authors: Parker, E. N. Bibcode: 1985NASCP2374....7P Altcode: Observations are needed to show the form of the strains introduced into the fields above the surface of the sun. The longitudinal component alone does not provide the basic information, so that it has been necessary in the past to use the filamentary structure observed in Hα to supplement the longitudinal information. Vector measurements provide the additional essential information to determine the strains, with the filamentary structure available as a check for consistency. It is to be expected, then, that vector measurements will permit a direct mapping of the strains imposed on the magnetic fields of active regions. Title: Magnetic Buoyancy and the Flux Ejection Effect in Stellar Dynamos Authors: Parker, E. N. Bibcode: 1985spit.conf..360P Altcode: No abstract at ADS Title: The Rapid Dissipation of Stellar Magnetic Fields and the Production of X-Ray Coronas Authors: Parker, E. N. Bibcode: 1985spit.conf..925P Altcode: No abstract at ADS Title: Magnetic Fields in the Radiative Interior of Stars - Part Two - Forced Convection and the 7LI Abundance Authors: Parker, E. N. Bibcode: 1984ApJ...286..677P Altcode: Magnetic fields of various forms, and of strengths ranging up to 5×108gauss, in the radiative core of the Sun have been hypothesized by various authors. This paper points out that the thermal shadows of magnetic inhomogeneities in the radiative core cause vertical mixing of fluid, with possible consequences for the 7Li abundance in the Sun. Magnetic fields of the order of 4×105gauss with scales of 3×104km are sufficient to provide the partial depletion of 7Li inferred from observation. It is found that the rms field in the outer radiative zone cannot much exceed 4×105gauss. Title: Magnetic fields in the radiative interior of stars. I Thermal shadows and forced convection. Authors: Parker, E. N. Bibcode: 1984ApJ...286..666P Altcode: It is pointed out that magnetic fields in the radiative interior of a star cause a slight reduction in the gas pressure, by a fraction of the order of B2/8πp. The effect is a proportionate reduction in the opacity and an increase in the effective heat transport coefficient, so that magnetic inhomogeneities cast thermal shadows in the general outflow of radiant energy. The shadows involve horizontal temperature gradients, forcing convective circulation in the otherwise stably stratified radiative zone. The associated vertical mixing may have important consequences for the thermonuclear burning of 7Li in the outer envelope of the star. Title: The rapid dissipation of magnetic fields with internal strains. Authors: Parker, E. Bibcode: 1984JRASC..78..205P Altcode: No abstract at ADS Title: Stellar fibril magnetic systems. I - Reduced energy state Authors: Parker, E. N. Bibcode: 1984ApJ...283..343P Altcode: The remarkable fibril structure of the magnetic fields at the surface of the sun (with fibrils compressed to 1,000-2,000 gauss) lies outside existing statistical theories of magnetohydrodynamic turbulence. The total energy of the fibril field is enhanced by a factor of more than 100 above the energy for the mean field in a continuum state. The magnetic energy density within a fibril is of the order of 100 times the local kinetic energy density, so that no simple application of equipartition principles is possible. It is pointed out that the total energy of the atmosphere (thermal + gravitational + magnetic) is reduced by the fibril state of the field by avoiding the magnetic inhibition of the convective overturning, suggesting that the formation of the observed intense fibril state may be in response to the associated energy reduction. Calculation of the minimum total energy of a polytropic atmosphere permeated by magnetic fibrils yields theoretical fibril fields of the order of 1-5 kilogauss when characteristics appropriate to the solar convective zone are introduced, in rough agreement with the actual fields of 1-2 kilogauss. The polytrope model, although crude, establishes that a large reduction in total energy is made possible by the fibril state. Title: Magnetic buoyancy and the escape of magnetic fields from stars Authors: Parker, E. N. Bibcode: 1984ApJ...281..839P Altcode: Magnetic buoyancy causes the azimuthal magnetic fields of stars to rise rapidly to the surface, from where they are generally assumed to escape freely into space. However, a closer look at the problem reveals the simple fact that disengagement of the field from the gas, and escape into space, require a convoluted field configuration, producing neutral point reconnection of the flux in the tenuous gas above the surface of the star. Only that flux which reconnects can escape.

Recent observations of the magnetic fields emerging through the surface of the Sun show that even at sunspot maximum the gaps in longitude between bipolar magnetic regions are so wide as to limit severely the reconnection between regions. We suggest from the observations that no more than perhaps 3% of the flux that is observed to emerge through the surface is able to reconnect and escape. Hence the surface of the Sun approximates to an impenetrable barrier rather than an open surface, with quantitative consequences for theoretical dynamo models.

Recent observations of the retraction of bipolar fields at the end of their appearance at the surface suggest active dynamical control by the convection beneath the surface. Title: Depth of origin of solar active regions Authors: Parker, E. N. Bibcode: 1984ApJ...280..423P Altcode: Observations show that the individual bipolar magnetic regions on the sun remain confined during their decay phase, with much of the magnetic field pulling back under the surface, in reverse of the earlier emergence. This suggests that the magnetic field is held on a short rein by subsurface forces, for otherwise the region would decay entirely by dispersing across the face of the sun. With the simple assumption that the fields at the surface are controlled from well-defined anchor points at a depth h, it is possible to relate the length l of the bipolar region at the surface to the depth h, with h about equal to l. The observed dimensions l about equal to 100,000 km for normal active regions, and l about equal to 10,000 km for the ephemeral active regions, indicate comparable depths of origin. More detailed observational studies of the active regions may be expected to shed further light on the problem. Title: The role of flux ejection in stellar dynamos Authors: Parker, E. N. Bibcode: 1984ApJ...276..341P Altcode: Magnetic buoyancy causes the magnetic field in the convective zone of a star to escape through the surface in times short compared to the period of the magnetic cycle. The sun serves as a prototype, where fields of 100-1000 gauss or stronger are present in the convective zone, as part of the 22 year magnetic cycle. The theoretical alpha-omega dynamo effect cannot cope with the rapid escape (in a year or so) because increasing the rate of generation of field serves also to shortern the period, to a value comparable to the escape time. It is suggested that the flux ejection dynamo effect may be operating in the deep convective zone, where the cyclonic rotation of the convective cells may be as large as 180 deg. If so, then the flux ejection effectively opposes the buoyant rise. It is shown that the net effect of flux ejection in the lower convective zone, and unopposed buoyancy in the upper convective zone, permits the alpha-omega-dynamo effect to carry on the cyclic regeneration of the magnetic field much as in the absence of either buoyancy or flux ejection, except that the magnetic field is strongly concentrated against the bottom of the convective zone. It is suggested that the lower and upper regions of the dynamo may be related to the normal and ephermeral active regions, as has already been suggested by others on the basis of the observed distinctions in distribution. Title: Magnetic Reconnection and Magnetic Activity Authors: Parker, E. N. Bibcode: 1984mrsl.conf...32P Altcode: No abstract at ADS Title: Magnetic reconnection and magnetic activity Authors: Parker, E. N. Bibcode: 1984GMS....30...32P Altcode: 1984GMS.........32P A large-scale magnetic field extending through a highly conducting tenuous fluid may become distorted on a small scale as a consequence of slow small-scale shuffling of the magnetic lines of force at the boundaries of the tenuous fluid. Any slow wrapping and winding introduced at the boundaries is distributed along the field (at the Alfven speed). It is a curious and little-known fact that such wrapping and winding possesses no static equilibrium (except for a set of solutions of extreme symmetry). The result is neutral-point reconnection of the strains in the field, rapidly dissipating the wrapping and winding. It is suggested that this is the principal cause of the extreme heating that produces the active corona of the sun and other stars. The shuffling of the footpoints of the magnetic field in the photospheric turbulence introduces small-scale wrapping and twisting into the coronal loops. The work done by the turbulence in twisting the fields is dissipated within a matter 10-20 hours by neutral-point reconnection, introducing heat into the corona at a rate of about 10 Mergs/sq cm sec for photospheric turbulence of 0.5 km/sec. It is suggested that this is the basic cause of the X-ray corona. Title: Heating the Corona of the Sun Authors: Parker, E. N. Bibcode: 1984rcch.conf..299P Altcode: No abstract at ADS Title: Galactic magnetic fields and magnetic monopoles. Authors: Parker, E. N. Bibcode: 1984mono.conf..125P Altcode: No abstract at ADS Title: Alfvén waves in a thermally stratified fluid. Authors: Parker, E. N. Bibcode: 1984GApFD..29R...1P Altcode: The propagation of Alfvén waves along a uniform horizontal field in a highly conducting incompressible fluid, subject to the convective forces produced by a uniform vertical temperature gradient, is treated in a Boussinesq approximation. It is shown that there are exact solutions with large amplitude but restricted form. Title: Alfvén waves in a thermally stratified fluid. Authors: Parker, E. N. Bibcode: 1984GApFD..29Q...1P Altcode: The propagation of Alfvén waves along a uniform horizontal field in a highly conducting incompressible fluid, subject to the convective forces produced by a uniform vertical temperature gradient, is treated in a Boussinesq approximation. It is shown that there are exact solutions with large amplitude but restricted form. Their restricted form means that an arbitrary disturbing force produces other motions as well as Alfvén waves. An arbitrary initial disturbance of small amplitude produces waves whose state of polarization varies along the direction of propagation. For large amplitudes, however, any mixtures of polarization states causes scattering into new modes. Title: Alfven waves in a thermally stratified fluid Authors: Parker, E. N. Bibcode: 1984GApFD..29....1P Altcode: The properties of Alfven waves propagating along a uniform horizontal field in a highly conducting incompressible medium in the presence of strong convective instability are examined in the Boussinesq approximation. In particular, it is sought to determine whether there are exact solutions to the dynamical equations in the presence of convective forces. It is shown that a class of exact solutions of arbitrary amplitude, but of limited form, which may be of some physical interest, does exist. For large amplitudes, any mixtures of polarization states are shown to cause scattering into new modes. Title: Direct coronal heating from dissipation of magnetic field. Authors: Parker, E. N. Bibcode: 1983NASCP.2280..23P Altcode: 1983sowi.conf...23P The visible corona of the Sun appears to be heated by direct dissipation of magnetic fields. The magnetic fields in the visible corona are tied at both ends to the photosphere where the active convection continually rotates and shuffles the footpoints in a random pattern. The twisting and wrapping of flux tubes about each other produce magnetic neutral sheets in a state of dynamical nonequilibrium such that the current sheets become increasingly concentrated with the passage of time. Dissipation of the high current densities takes place regardless of the high electrical conductivity of the fluid. The convection on the feet of the lines of force at the surface of the Sun goes directly (within a matter of 10 to 20 hours) into heat in the corona. The rate of doing work seems adequate to supply the necessary 10 to the 7th power ergs/square cm. sec for the active corona. Title: Invited Talk (Solar Division): "Theoretical MHD Structure of Stellar Atmospheres, and Close Observations of the Sun" Authors: Parker, Eugene Bibcode: 1983BAAS...15..950P Altcode: No abstract at ADS Title: Magnetic fields in the cosmos Authors: Parker, E. N. Bibcode: 1983SciAm.249b..44P Altcode: 1983SciAm.249...44P; 1983SciAm.249...36P Descriptive models for the dynamo processes that generate magnetic fields around celestial objects are reviewed. Magnetic fields are produced, along with an electric current, when a conductor is moved perpendicularly through a magnetic field, so long as the resulting current is fed back into the conductor to amplify the current and field. In MHD theory, the lines of force of the magnetic field travel with the conducting fluid. A weak current or field must be present initially to generate the field. Planets have molten cores and stars have ionized gases to act as the conductors, and all space has sufficient gas with free electrons. The rotations of the planets, stars, and galaxy enhance the magnetic fields. Convective patterns have been characterized in the earth's molten core because of anomalies observed in the magnetic field at the surface. It has been shown that the faster a planet rotates, the more powerful its magnetic field is. However, fluid motions will produce fields only if the fluid motion is helical. The exact mechanism in stars could be primordial magnetism trapped during formation. However, in galaxies, the Biermann battery effect, wherein free electrons move along the surfaces of stars, could create enough of a field for the amplification process to proceed. Title: Up to a frontier of astrophysics Authors: Parker, E. N. Bibcode: 1983Natur.303..262P Altcode: No abstract at ADS Title: Magnetic neutral sheets in evolving fields. I - General theory. Authors: Parker, E. N. Bibcode: 1983ApJ...264..635P Altcode: The problem of the hydrostatic equilibrium of a large-scale magnetic field embedded in a fluid with infinite electrical conductivity is considered. It is pointed out that a necessary condition for static equilibrium is the invariance of the small-scale pattern in the field along the large-scale direction. A varying topological pattern implies that no fluid pressure distribution exists for which the field is everywhere static. Magnetic neutral sheets form, and dynamical reconnection of the field takes place. It is shown here that the invariance is also a sufficient condition for the existence of a fluid pressure distribution producing static equilibrium. Even in the simplest cases, however, the requirements on the fluid pressure are extreme and, a priori, are unlikely. It is concluded that almost all twisted flux tubes packed together produce dynamical nonequilibrium and dissipation of their twisting. This is the basic effect underlying the long-standing conjecture that the shuffling of the footpoints of the bipolar magnetic fields in the sun is responsible for heating the active corona. Attention is then given to the consequences of this general dynamical dissipation in the magnetic fields that produce the active corona of the sun. The footpoints of the field are continually manipulated by the subphotospheric convection in such a way that the lines of force are continually wrapped and rotated about one another. Title: Magnetic Neutral Sheets in Evolving Fields - Part Two - Formation of the Solar Corona Authors: Parker, E. N. Bibcode: 1983ApJ...264..642P Altcode: It is shown in the previous paper that whenever twisted flux tubes are bundled together, they are subject to dynamical nonequilibrium and internal neutral point reconnection, causing rapid dissipation of their torsion. In the present paper we explore the consequences of this general dynamical dissipation in the magnetic fields that produce the active corona of the Sun. The footpoints of the field are continually manipulated by the subphotospheric convection, so that the lines of force are continually wrapped and rotated about each other. The dynamical dissipation of the wrapping and rotation transfers the work done on the footpoints directly into heat in the corona, at a rate estimated to be of the order of 107 ergs cm-2 s-1. The effect appears to be the principal source of heat to the visible corona.

This general picture implies that all magnetic fields extending outward from convecting astronomical bodies produce intense heating of the tenuous outer atmospheres of those bodies, in general agreement with the observed fact of the universal activity of stars and galaxies. Title: Generation of solar magnetic fields. I. II Authors: Parker, E. N. Bibcode: 1983ASSL..104..101P Altcode: 1983stp..conf..101P Attention is given to those magnetic field properties which allow the fields to destroy themselves rapidly, thereby producing solar, stellar and geomagnetic activity. Magnetic fields actively figure in the production of flares, plages, eruptions and streamers. The existence of magnetic fields in other stars is inferred from the X-rays that can be observed to radiate from them. In the second part of this paper, the discussion in the first part of the generation of magnetic fields from the motion of conducting fluids is further developed through the proposal of the 'short, sudden' idealization, and quick bursts of turbulence during which any degree of twisting and rotation can be accomplished are introduced. After these quick bursts of motion, the fluid is held motionless so that small scale irregularities subside, leaving a smooth, average and large scale state. This cycle is repeated at time intervals tau, producing the dynamo equations for the mean vector potential. Title: The propagation of torsion along flux tubes subject to dynamical nonequilibrium Authors: Parker, E. N. Bibcode: 1983GApFD..24..245P Altcode: The dynamical nonequilibrium of close-packed flux tubes is driven by the torsion in the individual tubes so that, wherever tubes with the same sense of twisting come into contact, there is reconnection of their azimuthal field components. The reconnection consumes the local torsion, causing the propagation of torsional Alfven waves into the region from elsewhere along the tubes. The formal problem of the propagation of the torsion along twisted flux tubes is presented and some of the basic physical properties worked out in the limit of small torsion. It is pointed out that in tubes with finite twisting the propagation of torsional Alfven waves can be a more complicated phenomenon. Application to the sun suggests that the propagation of torsion from below the visible surface up into the corona is an important energy supply to the corona for a period of perhaps 10-20 hours after the emergence of the flux tubes through the surface of the sun, bringing up torsion from depths of 104km or more. Torsion is continually supplied by the manipulation and shuffling of the field by the convection, of course. Title: Heating of the outer solar atmosphere. I. II Authors: Parker, E. N. Bibcode: 1983ASSL..104..129P Altcode: 1983stp..conf..129P The magnetic field coming up through the surface of the sun is responsible for the solar activity that heats the outer solar atmosphere. The field behaves in ways that are unexpected and little understood. Beckers and Schroeter (1969) found that the field of the sun has a fibril structure made up of separate, compressed flux tubes having fields of 1000-2000 G and 100-500 km diameters. Immediately above the solar surface, the field expands to fill the available volume. Nothing is known about the state beneath the surface of the sun. Attention is presently given to the state of knowledge on the heating of the corona as well as to a model for magnetic merging. In the second part of this presentation, the mutual wrapping and shuffling of the lines of force of a bipolar magnetic field above the photosphere and the structure of the cross section through a flux tube bundle are discussed. Title: Absence of equilibrium among close-packed twisted flux tubest Authors: Parker, E. N. Bibcode: 1983GApFD..23...85P Altcode: The general absence of static equilibrium of a close-packed array of parallel twisted flux tubes in a highly conducting medium is demonstrated by showing that the solutions to the equilibrium equation V2A+4P'(A) = 0 do not generally preserve the flux connections around each twisted tube as the functional form of P(A) is varied. A special constraint on the variation of P(A) is introduced, then, by the requirement that the flux connections be preserved. Hence we conclude that while a particular array of twisted tubes, described by the internal circulation of flux within each tube, may have an equilibrium for some suitably chosen functional form P(A), the array is generally in a state of nonequilibrium for lack of that precise functional form in the real world. Title: The hydrodynamics of magnetic nonequilibrium Authors: Parker, E. N. Bibcode: 1983GApFD..24...79P Altcode: Because the dynamical nonequilibrium of closely packed twisted flux tubes is essentially the problem of two-dimensional MHD turbulence, the extensive literature on two-dimensional turbulence represents the hydrodynamics of magnetic nonequilibrium. Many features of the turbulence can conversely be understood as a consequence of the dynamical nonequilibrium. Attention is presently given to the dynamics of the strong fluid jets, issuing from reconnection points, that are exhibited by numerical simulations of two-dimensional turbulence. Simple examples are given which show that the uniformity of jet width observed is a consequence of the form of the pressure of the magnetic fields between which the jets are confined. The general hydrodynamics of a layer of fluid confined by steady pressures is reducible to a quadrature, so that a variety of effects may be considered, including gravitation. The dissipation of the solar corona is discussed. Title: Cosmic magnetic fields. Their origin and manifestation. In two parts. Authors: Parker, E. Bibcode: 1983cmft.book.....P Altcode: No abstract at ADS Title: Generation of Solar Magnetic Fields II Authors: Parker, Eugene N. Bibcode: 1983ASSL..104..113P Altcode: No abstract at ADS Title: Heating of the Outer Solar Atmosphere II Authors: Parker, Eugene N. Bibcode: 1983ASSL..104..139P Altcode: No abstract at ADS Title: The rapid dissipation of magnetic fields in highly conducting fluids Authors: Parker, E. N. Bibcode: 1982GApFD..22..195P Altcode: This paper treats the dynamical conditions that obtain when long straight parallel twisted flux tubes in a highly conducting fluid are packed together in a broad array. It is shown that there is generally no hydrostatic equilibrium. In place of equilibrium there is a dynamical nonequilibrium, leading to neutral point reconnection and progressive coalescence of neighboring tubes (with the same sense of twisting), forming tubes of larger diameter and reduced twist. The magnetic energy in the twisting of each tube declines toward zero, dissipated into small-scale motions of the fluid and thence into heat. The physical implications are numerous. For instance, it has been suggested that the subsurface magnetic field of the sun is composed of close-packed twisted flux tubes. Any such structures are short lived, at best. The footpoints of the filamentary magnetic fields above bipolar magnetic regions on the sun are continually shuffled and rotated by the convection, so that the fields are composed of twisted rubes. The twisting and mutual wrapping is converted directly into fluid motion and heat by the dynamical nonequilibrium, so that the work done by the convection of the footpoints goes directly into heating the corona above. This theoretical result is the final step, then, in understanding the assertion by Rosner, Tucker, and Valana, and others, that the observed structure of the visible corona implies that it is heated principally by direct dissipation of the supporting magnetic field. It is the dynamical nonequilibrium that causes the dissipation, in spite of the high electrical conductivity. It would appear that any bipolar magnetic field extending upward from a dense convective layer into a tenuous atmosphere automatically produces heating, and a corona of some sort, in the sun or any other convective star. Title: Magnetic monopoles and the survival of galactic magnetic fields Authors: Turner, Michael S.; Parker, E. N.; Bogdan, T. J. Bibcode: 1982PhRvD..26.1296T Altcode: The most stringent, mass-independent limit on the flux of magnetic monopoles is based upon the survival of the galactic magnetic fields, the so-called "Parker limit": F<~10-16 cm-2sr-1sec-1. We reexamine this limit, taking into account the monopole's mass and velocity distribution, and the observed structure of the galactic magnetic field. We derive flux limits which depend upon the monopole's mass and velocity, and the strength, coherence length, and regeneration time of the galactic magnetic field. The largest monopole flux consistent with both the survival of the galactic magnetic field and the bounds from the mass density contributed by monopoles is F~=10-12 cm-2sr-1sec-1, arising for monopoles of mass ~= 1019 GeV with velocity ~=3×10-3c which cluster with the Galaxy. An observed flux greater than this would have profound implications for our understanding of the galactic magnetic field, and we briefly explore some exotic possibilities. Of course, this bound is not applicable to a local source (e.g., the Sun, atmospheric cosmic-ray production, etc.). Title: The Flux Ejection Dynamo with Small Diffusivity - Part One - Basic Properties Authors: Parker, E. N. Bibcode: 1982Ap&SS..85..167P Altcode: The flux ejection dynamo in an infinitely broad convective layer of finite depth is treated in the limit of large electrical conductivity. The upper surface of the convective layer is open to empty space while the lower surface is closed to the passage of fluid and field. An idealized convective overturning is employed, permitting an exact description of the symmetry and distribution of the magnetic field carried with the fluid. Escape of the reverse field through the free surface restores the initial vertical distribution of mean field and adds a thin sheet of flux in the initial direction across the bottom of the convective layer. The total flux in the mean horizontal field grows linearly with the number of convective cycles. We discuss the boundary conditions to be applied to an astronomical body with the flux ejection dynamo operating at its surface. It is pointed out that if there were a flux ejection dynamo operating in the Sun, the implications of the magnetic bipolar regions emerging through the surface would be the opposite of the usual. Title: The Flux Ejection Dynamo with Small Effusivity - Part Two - Illustrative Examples Authors: Parker, E. N. Bibcode: 1982Ap&SS..85..183P Altcode: A number of examples are worked out to illustrate the consequences of reverse flux ejection from the surface of a convective layer of conducting fluid. Generally the reverse flux ejection has the opposite effect of magnetic buoyancy, tending to bury the fields rather than bringing them through the surface. Even a weak flux ejection effect prevents the excape of magnetic field through the surface. Reverse flux ejection at the surface of an αω-dynamo profoundly alters the character of the solutions of the dynamo equations. Altogether, flux ejection serves to obscure the interpretation of magnetic observations. The outstanding problem now is to determine under what circumstances there exists cyclonic convection with rotations in excess of ±1/2π in the rising columns of fluid. Negative turbulent diffusion is expected to be a close companion of the flux ejection effect. Title: The Dynamics of Fibril Magnetic Fields - Part Four - Trapping in Closed Convective Rolls Authors: Parker, E. N. Bibcode: 1982ApJ...256..746P Altcode: The equations of motion for a slender, buoyant flux tube extending horizontally along a closed convective roll are solved to illustrate the motion of the flux tube relative to the fluid. The principal effect of the buoyant rise u of the flux tube is to offset the path of the tube (which remains closed) from the closed circulation pattern of the fluid. Further investigation shows that an upward decrease of ρ u causes the position of the tube to spiral inward to the dynamical equilibrium point where the convective downdraft is equal to the buoyant rise. Any variation of the convective velocity along the length of the roll has the same effect, so that flux tubes, or fibrils, are stably trapped in any closed convective flow that exceeds u.

The effect may be operative in the convective zone of the Sun and other stars where the meridional circulation is larger than the rate of rise of the standard fibril. Even if there is no long-term trapping of the field, the position of emergence of flux tubes at the surface of the Sun may be widely removed from their birthplace. A number of examples are given to illustrate the possibilities. Title: The dynamics of fibril magnetic fields. III - Fibril configurations in steady flows. Authors: Parker, E. N. Bibcode: 1982ApJ...256..736P Altcode: The present investigation has the objective to provide an illustration of the equilibrium form of a hypothetical fibril field beneath the surface of the sun. Equilibrium fibril paths in static and moving atmospheres are considered. The provided examples are related to horizontal flows in an atmosphere in which the two anchor points of the arched fibril lie along the flow direction relative to each other. A brief introduction to the subject of the motion of horizontal fibrils in convective rolls is also presented, taking into account some implications for the sun. The equations of motion for a slender, buoyant flux tube extending horizontally along a closed convective roll are solved to illustrate the motion of the flux tube relative to the fluid, and attention is given to theoretical possibilities for the escape of flux tubes from a large horizontal convective roll in the sun. Title: The Dynamics of Fibril Magnetic Fields - Part Two - the Mean Field Equations Authors: Parker, E. N. Bibcode: 1982ApJ...256..302P Altcode: A variety of scenarios for the origin and activity of magnetic fields in the convective zone of the Sun have been put forth in recent years. In particular, a number of authors have urged that the magnetic field is in a generally fibril state, much as observed at the surface, with a variety of suggestions as to the consequences. The present paper works out the mean field equations for intense thin fibrils of fixed cross section under the assumption of some significant local ordering. The aim is to establish to what degree new effects may arise as a result of the fibril state. It is shown that the fibril state of a mean field B enhances the tension in the field and the buoyancy of the field by the compression factor m of the field in the individual fibrils. New qualitative effects appear in the slip velocity u of the fibrils through the ambient fluid and in the neutral point reconnection of neighboring fibrils. Some of the novel features are illustrated in later papers in this series. One of the most important consequences is the simplification of the theory of turbulent diffusion by eliminating the looping and tangling that arises when a continuum field is carried in a chaotic turbulent flow. We have been unable to find any effects that would admit of a new concept for the origin of the solar magnetic fields. Title: The dynamics of fibril magnetic fields. I - Effect of flux tubes on convection. Authors: Parker, E. N. Bibcode: 1982ApJ...256..292P Altcode: Observations have established the general fibril state of the magnetic field at the visible surface of the sun. This extraordinary state of the field, in separate intense flux tubes, implies that the convection has a relatively permanent, closed topology, in spite of the large Reynolds number. This paper explores some of the effects of the separate flux tubes on the convective motions, generally pushing the convective cells toward aligning their downdrafts with the flux tubes so as to minimize the dissipation. Title: Compression of magnetic field in a viscous boundary layer. Authors: Parker, E. N. Bibcode: 1982SoPh...77....3P Altcode: Galloway, Proctor, and Weiss have shown by numerical experiment that the magnetic field extending across a convective cell in a highly conducting viscous fluid may be concentrated into sheets with energy density B2/8π larger than the kinetic energy density 1/2ϱv2 of the convection by a factor (v/η)1/2 or more. This paper employs conventional boundary layer theory for high Reynolds number to provide a simple analytical example illustrating this remarkable effect of field concentration. Title: The flux ejection dynamo effect Authors: Parker, E. N. Bibcode: 1982GApFD..20..165P Altcode: The mean-field effects of cyclonic convection become increasingly complex when the cyclonic rotation exceeds ½-. Net helicity is not required, with negative turbulent diffusion, for instance, appearing in mirror symmetric turbulence. This paper points out a new dynamo effect arising in convective cells with strong asymmetry in the rotation of updrafts as against downdrafts. The creation of new magnetic flux arises from the ejection of reserve flux through the open boundary of the dynamo region. It is unlike the familiar -effect in that individual components of the field may be amplified independently. Several formal examples are provided to illustrate the effect. Occurrence in nature depends upon the existence of fluid rotations of the order of in the convective updrafts. The flux ejection dynamo may possibly contribute to the generation of field in the convective core of Earth and in the convective zone of the sun and other stars. Title: Photospheric flow and stellar winds Authors: Parker, E. N. Bibcode: 1981ApJ...251..266P Altcode: The effect of the photospheric outflow on the expansion of the strongly bound coronas of dwarf main-sequence stars is examined. The extended temperatures of the strongly bound coronas cause the stars to expand and form tenuous stellar winds, with a slight mean upward motion of the gas in the photosphere to replenish the mass loss through the coronal expansion. A formal solution of the time-dependent hydrodynamic equations illustrates the effects of the photospheric velocity at large distances, and the effect of blocking the upward flow in the photosphere is calculated using the sun as an example. Results indicate that the expansion of a strongly bound corona is insensitive over historical time scales to the small outflow of gas in the photosphere. Title: The hydromagnetic dynamo Authors: Parker, E. N. Bibcode: 1981ESASP.161...23P Altcode: 1981plas.work...23P No abstract at ADS Title: The non-equilibrium of magnetic fields Authors: Parker, E. N. Bibcode: 1981ESASP.161...31P Altcode: 1981plas.work...31P No abstract at ADS Title: The magnetohydrodynamic dynamo Authors: Parker, E. N. Bibcode: 1981plap.rept...23P Altcode: A mechanism for the maintenance of the magnetic fields of planets, stars, and galaxies is postulated. It appears that cyclonic convection and nonuniform rotation within the liquid metal cores of planets, the convective zones of stars, and the gaseous disks of galaxies provide an efficient dynamo mechanism for the production of these fields. The dominant field within the body is azimuthal, produced by nonuniform rotation from the poloidal field. The interaction of cyclonic convection within the azimuthal field produces loops of flux in meridional planes whose net effect is a meridional circulation of field in the same sense as the original poloidal field. Both stationary and oscillatory fields can be generated in this way. Title: The nonequilibrium of magnetic fields Authors: Parker, E. N. Bibcode: 1981plap.rept...31P Altcode: The more subtle properties of magnetic fields which create nonequilibrium and lead to vigorous activity in otherwise sluggish gas-field systems are evaluated for gross hydromagnetic effects. The gentle manipulation of magnetic fields on a large scale leads to the production of small scale variations and discontinuities, providing intense dissipation of magnetic field in a large scale system. A magnetic field embedded in a conducting fluid possesses a static equilibrium only if the topology of the lines of force is suitably invariant along the direction of the field. When the field does not possess the necessary invariance, it is subject to internal neutral point reconnection. The magnetic fields of most stars suffer such nonequilibrium, and consequent enhanced dissipation, providing an important source of heat in their outer atmospheres. Title: The Dissipation of Inhomogeneous Magnetic Fields and the Problem of Coronae - Part Two - the Dynamics of Dislocated Flux Authors: Parker, E. N. Bibcode: 1981ApJ...244..644P Altcode: When any of the flux tubes that collectively make up a magnetic field continuum is dislocated and misaligned relative to the rest of the field, there is a dynamical steepening of field gradients. Consequently, there is rapid dissipation of the dislocated field no matter how large the electrical conductivity of the medium. This paper presents some formal illustrations of local conditions along a misaligned flux tube, showing the simultaneous onset of diffusion, fluid motion, and hydromagnetic wave propagation. The examples show that the total effect is complicated and subject only to estimation, rather than formal calculation, at the present time.

We suggest that dislocation dissipation occurs in the magnetic fields of active regions on the Sun, contributing to the enhanced corona. Estimates of the dislocation dissipation in the active corona are carried out based on the observed properties of active coronal arches and filaments. The estimates show that the dissipation may contribute a significant portion of the coronal heating. It is pointed out that dislocation dissipation must occur in the active terrestrial magnetosphere and in the active gaseous disk of the Galaxy, although we make no attempt at a quantitative assessment of the rates. Title: The dissipation of inhomogeneous magnetic fields and the problem of coronae. I - Dislocation and flattening of flux tubes. II - The dynamics of dislocated flux Authors: Parker, E. N. Bibcode: 1981ApJ...244..631P Altcode: Attention is given to the dynamical dissipation arising in a magnetic field extending up through a tenuous atmosphere when an elemental flux tube in the field (1) is displaced from its equilibrium position and/or (2) is inflated by an internal fluid pressure different from the external fluid pressure. It is pointed out that as a consequence the tension in the lines of force of the ambient field flattens the dislocated tube so that the thickness of the tube decreases without limit and that the local field gradients increase rapidly with the passage of time until destroyed by one or more dissipative effects. The magnetic energy of a dislocated flux tube is therefore soon converted into thermal energy no matter how low the molecule resistivity of the fluid. Some formal illustrations of local conditions along a misaligned flux tube are presented, showing the simultaneous onset of diffusion, fluid motion, and hydromagnetic wave propagation. The examples demonstrate that the total effect is complicated and subject only to estimation, rather than formal calculation, at the present time. Title: Residual fields from extinct dynamos Authors: Parker, E. N. Bibcode: 1981GApFD..18..175P Altcode: The paper explores some of the many facets of the problem of the generation of magnetic fields in convective zones of declining vigor and/or thickness. The ultimate goal of such work is the explanation of the magnetic fields observed in A-stars. The present inquiry is restricted to kinematical dynamos, to show some of the many possibilities, depending on the assumed conditions of decline of the convection. The examples serve to illustrate in what quantitative detail it will be necessary to describe the convection in order to extract any firm conclusions concerning specific stars. The first illustrative example treats the basic problem of diffusion from a layer of declining thickness. The second adds a buoyant rise to the field in the layer. The third treats plane dynamo waves in a region with declining eddy diffusivity, dynamo coefficient, and large-scale shear. The dynamo number may increase or decrease with declining convection, with an increase expected if the large-scale shear does not decline as rapidly as the eddy diffusivity. It is shown that one of the components of the field may increase without bound even in the case that the dynamo number declines to zero. Title: The spontaneous concentration of magnetic field in the photosphere of the sun. Authors: Parker, E. N. Bibcode: 1981ASIC...68...33P Altcode: 1981spss.conf...33P The basic physics of magnetic flux tubes in the solar photosphere is reviewed, with areas still open to conjecture pointed out. The question of the concentration of individual small flux tubes to levels of 1-2 kilogauss, when the average solar surface magnetic field is on the order of 10 gauss, by processes of twisting and the formation of flux ropes made up of tubes wound around each other is considered together with the effects of turbulence on the flux tube. Mechanisms for tube compression by the evacuation of the gas contained within a flux tube are then examined, and the possibility of field concentration through the cooling of the gas within the tube in a superadiabatic process is suggested. Attention is then given to possible mechanisms serving to maintain the concentration of flux tubes far below the surface of the sun which gives rise to sunspots and pores as the flux tree emerges through the surface. Title: Summary Commentary - Solar Phenomena in Stars and Stellar Systems Authors: Parker, E. N. Bibcode: 1981ASIC...68..551P Altcode: 1981spss.conf..551P No abstract at ADS Title: A review of: "Solar flare magnetohydrodynamics" Authors: Parker, E. N. Bibcode: 1981GApFD..18..332P Altcode: Edited by E. R. Priest (Volume 1 of "The Fluid Mechanics of Astrophysics and Geophysics"). Gordon and Breach Science Publishers, 1981. xii + 563 pp. (Cloth Bound $89.50). (ISBN 0 677 0553 7 and ISSN 0 2604353). Title: Solar System Plasma Physics. Authors: Lanzerorotti, L. J.; Kennel, C. F.; Parker, E. N. Bibcode: 1980JPlPh..24..191L Altcode: No abstract at ADS Title: Book-Review - Solar System Plasma Physics Authors: Kennel, C. F.; Lanzerotti, L.; Parker, E. N.; Akasofu, S. I. Bibcode: 1980Natur.285..598K Altcode: No abstract at ADS Title: Book-Review - Cosmical Magnetic Fields Authors: Parker, E. N.; de Groot, M. Bibcode: 1980IrAJ...14..189P Altcode: No abstract at ADS Title: Book-Review - Solar System Plasma Physics Authors: Kennel, C. F.; Lanzerotti, L. J.; Parker, E. N.; Hultqvist, B. Bibcode: 1980SSRv...26R.449K Altcode: No abstract at ADS Title: Sunspots and the physics of magnetic flux tubes. VIII. Overstability in a magnetic field in a downdraft. Authors: Parker, E. N. Bibcode: 1979ApJ...233.1005P Altcode: The dynamical properties of convective overstability in a vertical magnetic field with a downdraft are considered. A variety of effects is illustrated. The overstability produces Alfven waves propagating both upward or downward along the magnetic field. The favored direction of emission may be upward or downward depending upon the magnitude of the heat transport coefficient. The largest asymmetry is produced by a difference in reflectivity between the upper and lower boundaries. It is shown that a very modest reflection coefficient of the upper boundary, with no reflection at the lower boundary, causes most of the waves to be emitted downward, and vice versa. Applying these results to the flux tubes extending up through the convective zone of the Sun, it follows that those flux tubes are dynamically active beneath the surface, as suggested earlier by ourselves and others, but there is no reason to expect any significant wave flux to appear in the field above the surface. The waves propagate downward into the Sun and are presumably dispersed there by the nonlinear interaction with the turbulent convection, etc. Title: Sunspots and the physics of magnetic flux tubes. IX. Umbral dots and longitudinal overstability. Authors: Parker, E. N. Bibcode: 1979ApJ...234..333P Altcode: The dynamical properties of the sunspot field and of a column of hot gas confined by such a vertical magnetic field are examined in order to understand the umbral dot within the context of the magnetic sunspot structure. Attention is given to the conditions necessary for gas intrusion, longitudinal as well as convective overstability, the growing modes, and the even mode. With the hypothesis that the subsurface magnetic field of a sunspot splits into many separate flux tubes with field-free gas between, it is suggested that the field-free columns occasionally punch their way up through the overlying magnetic field to the surface, appearing there as the bright, field-free umbral dots. Effects fostering the phenomenon are also discussed, that is, the enhanced temperature of a column of rising gas, the strongly reduced overhead magnetic pressure, and the initiated upward intrusion; these effects are illustrated with examples. Title: Sunspots and the Physics of Magnetic Flux Tubes. VII. Heat Flow in a Convective Downdraft Authors: Parker, E. N. Bibcode: 1979ApJ...232..291P Altcode: The heat flux in the familiar Boussinesq convective cell with free upper and lower boundaries is plotted to show the suppression of the upward heat flow by a downdraft. Application to the solar convective zone shows that downdrafts of 1-2 km 1 at depths of 1 x 1O km beneath the visible surface of the Sun are sufficient to reduce the upward heat flux to a small fraction of the ambient value. Hence the downdraft that is postulated to operate beneath the sunspot, to account for the gathering of flux tubes to form the spot, would be sufficient to reduce the heat flux to values comparable to those observed in sunspot umbrae. This greatly relieves the demands on cooling by the convective generation of Alfve'n waves in order to form the observed intense fields of 3000 gauss or more. Subject headings: convection - hydromagnetics - Sun: sunspots Title: Sunspots and the physics of magnetic flux tubes. VI. Convective propulsion. Authors: Parker, E. N. Bibcode: 1979ApJ...232..282P Altcode: The effect of negative aerodynamic drag in an ideal fluid subject to convective instability is considered. It is shown that a cylinder moving in such a fluid is propelled forward in its motion by the convective forces and that the characteristic acceleration time is comparable to the onset time of convective motions in the fluid. It is suggested that convective propulsion plays an important role in the dynamics of flux tubes extending through the surface of the sun. The suppression of the upward heat flow in a Boussinesq convective cell with free upper and lower boundaries by a downdraft is then analyzed. Application to the solar convection zone indicates that downdrafts of 1 to 2 km/s at depths of 1000 to 4000 km beneath the visible surface of the sun are sufficient to reduce the upward heat flux to a small fraction of the ambient value. Title: Sunspots and the physics of magnetic flux tubes. V. Mutual hydrodynamic forces between neighboring tubes. Authors: Parker, E. N. Bibcode: 1979ApJ...231..270P Altcode: The mutual hydrodynamic forces between parallel cylinders in a moving fluid are illustrated through several formal examples. Parallel tubes in a uniform flow are attracted or repelled depending on whether they are side by side or one ahead of the other, respectively. A pulsating or undulating tube attracts all other neighboring tubes toward itself. These hydrodynamic effects suggest that the separate flux tubes beneath the sunspots exert significant attractive forces on each other. Title: Sunspots and the physics of magnetic flux tubes. III. Aerodynamic lift. Authors: Parker, E. N. Bibcode: 1979ApJ...231..250P Altcode: The aerodynamic lift exerted on a magnetic flux tube by the asymmetric flow around the two sides of the tube is calculated as part of an investigation of the physics of solar flux tubes. The general hydrodynamic forces on a rigid circular cylinder in a nonuniform flow of an ideal fluid are derived from the first derivatives of the velocity field. Aerodynamic lift in a radial nonuniform flow is found to act in the direction of the flow, toward the region of increased flow velocity, while in a shear flow, lift is perpendicular to the free stream and directed toward increasing flow velocity. For a general, three dimensional, large-scale stationary incompressible equilibrium flow, an expression is also derived relating the lift per unit length to the dynamical pressure, cylinder radius and the gradient of the free-stream velocity. Evidence from an asymmetric airfoil in a uniform flow indicates that lift is enhanced in a real fluid in the presence of turbulence. Title: Sunspots and the physics of magnetic flux tubes. II. Aerodynamic drag. Authors: Parker, E. N. Bibcode: 1979ApJ...230..914P Altcode: No abstract at ADS Title: Sunspots and the physics of magnetic flux tubes. I. The general nature of the sunspots. Authors: Parker, E. N. Bibcode: 1979ApJ...230..905P Altcode: Analysis of the dynamical stability of a large flux tube suggests that the field of a sunspot must divide into many separate tubes within the first 1000 km below the surface. Buoyancy of the Wilson depression at the visible surface and probably also a downdraft beneath the sunspot hold the separate tubes in a loose cluster. Convective generation of Alfven waves, which are emitted preferentially downward, cools the tubes. Aerodynamic drag on a slender flux tube stretched vertically across a convective cell is also studied. Since the drag is approximately proportional to the local kinetic energy density, the density stratification weights the drag in favor of the upper layers. Horizontal motions concentrated in the bottom of the convective cell may reverse this density effect. A downdraft of about two km/sec through the flux tubes beneath the sunspot is hypothesized. Title: The Instability of a Horizontal Magnetic Field in an Atmosphere Stable Against Convection Authors: Parker, E. N. Bibcode: 1979Ap&SS..62..135P Altcode: The theoretical problem posed by the buoyant escape of a magnetic field from the interior of a stably stratified body bears directly on the question of the present existence of primordial magnetic fields in stars. This paper treats the onset of the Rayleigh-Taylor instability of the upper boundary of a uniform horizontal magnetic field in a stably stratified atmosphere. The calculations are carried out in the Boussinesq approximation and show the rapid growth of the initial infinitesimal perturbation of the boundary. This result is in contrast to the extremely slow buoyant rise of a separate flux tube in the same atmosphere. Thus for instance, at a depth of 1/3R beneath the surface of the Sun, a field of 102 G develops ripples over a scale of 103 km in a characteristic time of 50 years, whereas the characteristic rise time of the same field in separate flux tubes with the same dimensions is 1010 years. Thus, the development of irregularities proceeds quickly, soon slowing, however, to a very slow pace when the amplitude of the irregularities becomes significant. Altogether the calculations show the complexity of the question of the existence of remnant primordial magnetic fields in stellar interiors. Title: INVITED PAPER - George Ellery Hale and Active Mangetic Fields Authors: Parker, E. N. Bibcode: 1979BAAS...11..423P Altcode: No abstract at ADS Title: Cosmical magnetic fields. Their origin and their activity Authors: Parker, E. N. Bibcode: 1979cmft.book.....P Altcode: The physics of large-scale magnetic fields in fluids of high electrical conductivity is examined, with emphasis on the generation of magnetic fields in astronomical bodies and interactions of the fields with those bodies. The role and nature of cosmic magnetic fields are described and solutions to the basic electromagnetic equations are developed. Consideration is given to magnetic field stress and energy and the problem of magnetic equilibrium. The propagation of disturbances in a magnetic fluid is discussed, and the basic properties and interactions of isolated flux tubes and twisted flux tubes are considered. The topology of magnetic lines of force, the nonequilibrium of invariant and non-invariant fields, the breakup and escape of submerged magnetic fields, the rapid reconnection of magnetic lines of force, the exclusion of magnetic fields from closed circulation patterns, and the generation and nature of magnetic fields in turbulent fluids, including the dynamo problem, are treated, and planetary, solar, stellar and galactic magnetic fields are examined. Title: Gearing up to answer question posed by the sun. Authors: Parker, E. N. Bibcode: 1979PhT....32i...9P Altcode: No abstract at ADS Title: The University of Chicago: Department of Astronomy and Astrophysics, Chicago, Illinois 60637; The Yerkes Observatory, Williams Bay, Wisconsin 53191. Report. Authors: Parker, E. N.; Hobbs, L. M. Bibcode: 1979BAAS...11...80P Altcode: No abstract at ADS Title: The enigma of solar activity. Authors: Parker, E. N. Bibcode: 1979psa..conf....8P Altcode: No abstract at ADS Title: Book-Review - Cosmical Magnetic Fields - Their Origin and Their Activity Authors: Parker, E. N. Bibcode: 1979AstQ....3..201P Altcode: No abstract at ADS Title: Solar system plasma physics. Vol.1: Solar and solar wind plasma physics; Vol.2: Magnetospheres; Vol.3: Solar system plasma processes Authors: Parker, E. N.; Kennel, Charles F.; Lanzerotti, Louis J. Bibcode: 1979sspp.book.....P Altcode: No abstract at ADS Title: Summary Remarks Authors: Parker, E. N. Bibcode: 1979AIPC...56..425P Altcode: 1979pama.work..425P No abstract at ADS Title: Solar system plasma physics. Volume 3 - Solar system plasma processes Authors: Lanzerotti, L. J.; Kennel, C. F.; Parker, E. N. Bibcode: 1979anh..book.....L Altcode: The papers deal with such solar system plasma processes as shocks in collisionless space plasmas; magnetic field reconnection, hydrodynamic waves; plasma processes in the earth's radiation belts; and magnetospheric plasma waves. Some papers deal with the ionospheric plasma; the physics of heavy ions in the magnetosphere; impacts of ionospheric-magnetospheric processes on terrestrial science and technology; and impacts of the solar system environment on man, and vice versa. Title: Solar system plasma physics. Volume 1 - Solar and solar wind plasma physics Authors: Parker, E. N.; Kennel, C. F.; Lanzerotti, L. J. Bibcode: 1979sswp.book.....P Altcode: The paper covers such aspects of solar physics as the mechanisms which drive solar phenomena (such as heating of the corona, the acceleration of particles in flares, the dissipation of magnetic energy in current sheets, and the generation of the solar wind), the structure and energetics of the quiet solar atmosphere, the structure of the corona, the solar composition, and solar terrestrial interactions. Phenomena associated with solar flares are discussed, and physical mechanism which have been advanced to explain them are examined. The impact of solar physics on the development of plasma physics and magnetohydrodynamics is noted. The mathematical framework describing the microscopic and macroscopic aspects of the solar wind plasma is outlined Title: A broad look at solar physics adapted from the solar physics study of August 1975 Authors: Parker, E.; Timothy, A.; Beckers, J.; Hundhausen, A.; Kundu, M. R.; Leith, C. E.; Lin, R.; Linsky, J.; MacDonald, F. B.; Noyes, R. Bibcode: 1979sswp.book....3P Altcode: 1979sswp.book....3B The current status of our knowledge of the basic mechanisms involved in fundamental solar phenomena is reviewed. These include mechanisms responsible for heating the corona, the generation of the solar wind, the particle acceleration in flares, and the dissipation of magnetic energy in field reversal regions, known as current sheets. The discussion covers solar flares and high-energy phenomena, solar active regions; solar interior, convection, and activity; the structure and energetics of the quiet solar atmosphere; the structure of the corona; the solar composition; and solar terrestrial interactions. It also covers a program of solar research, including the special observational requirements for spectral and angular resolution, sensitivity, time resolution, and duration of the techniques employed. Title: Solar system plasma physics. Volume 2 - Magnetospheres Authors: Kennel, C. F.; Lanzerotti, L. J.; Parker, E. N. Bibcode: 1979magn.book.....K Altcode: The present volume covers such topics as global problems in magnetospheric plasma physics; magnetosphere, ionosphere, and atmosphere interactions; Jupiter's magnetosphere and radiation belts, the magnetosphere of Mercury; interactions of the solar wind with the planets Mars, Venus, and Mercury; and interactions between the solar wind and comets. The theory of planetary dynamics is outlined, and the contemporary basis for the development of a comparative theory of magnetospheres is examined. Title: The mutual attraction of magnetic knots. Authors: Parker, E. N. Bibcode: 1978ApJ...222..357P Altcode: It is observed that the magnetic knots associated with active regions on the sun have an attraction for each other during the formative period of the active regions, when new magnetic flux is coming to the surface. The attraction disappears when new flux ceases to rise through the surface. Then the magnetic spots and knots tend to come apart, leading to disintegration of the sunspots previously formed. The dissolution of the fields is to be expected, as a consequence of the magnetic repulsion of knots of like polarity and as a consequence of the hydromagnetic exchange instability. The purpose of this paper is to show that the mutual attraction of knots during the formative stages of a sunspot region may be understood as the mutual hydrodynamic attraction of the rising flux tubes. Two rising tubes attract each other, as a consequence of the wake of the leading tube when one is moving behind the other, and as a consequence of the Bernoulli effect when rising side by side. Title: Hydraulic concentration of magnetic fields in the solar photosphere. VI. Adiabatic cooling and concentration in downdrafts. Authors: Parker, E. N. Bibcode: 1978ApJ...221..368P Altcode: The remarkable concentration of the general field of the Sun into isolated intense flux tubes at the visible surface must be a direct consequence of conditions immediately beneath the surface. It is pointed out that the convective heat transport in the magnetic field swept into the downdrafts in the junctions of supergranule boundaries is strongly suppressed by the magnetic field. The net heat transport is reduced to such a degree that the temperature of the downdraft within the field increases nearly adiabatically below the visible surface, and hence is significantly cooler than the surrounding ambient gas. The reduced temperature enhances the downdraft within the field and permits the gravitational field to evacuate the flux tube. The magnetic field is then strongly compressed by the external gas pressure, leading to the extraordinary observed strengths of 1500 gauss or more. It is suggested that the magnetic knots found in active regions are formed wholly or partly by the same effect. The general occurrence of superadiabatic temperature gradients and convective heat transport in the dwarf and subdwarf main-sequence stars suggests that their magnetic fields are generally broken up and concentrated by this effect, much as in the Sun. Subject headings: convection hydromagnetics - Sun: granulation - Sun: magnetic fields Title: The University of Chicago, Department of Astronomy and Astrophysics, Chicago, Illinois; The Yerkes Observatory, Williams Bay, Wisconsin. Reports. Authors: Parker, E. N.; Hobbs, L. M. Bibcode: 1978BAAS...10Q..77P Altcode: No abstract at ADS Title: The University of Chicago, Department of Astronomy and Astrophysics, Chicago, Illinois. The Yerkes Observatory, Williams Bay, Wisconsin. Reports. Authors: Parker, E. N.; Hobbs, L. M. Bibcode: 1978BAAS...10R..77P Altcode: No abstract at ADS Title: Solar Physics in Broad Perspective Authors: Parker, E. N. Bibcode: 1978nsp..conf....1P Altcode: No abstract at ADS Title: The relative diffusion of strong magnetic fields and tenuous gases. Authors: Parker, E. N. Bibcode: 1977ApJ...215..374P Altcode: General equations are given for treating the diffusion of a magnetic field in a fluid with electrical conductivity and a resistive diffusion coefficient. Consequences of nonnegligible gas motion are investigated by considering the one-dimensional problem where a tenuous isothermal gas with pressure expressed as a function of x-coordinate and time is enmeshed in a magnetic field in the y-direction. Approximate equations are obtained for the case of weak fluctuations in gas or field pressure, and the properties of a nonlinear diffusion equation are illustrated with the example of an initial thin slab of gas confined by a uniform field on either side. The advance of a gas front into a nonvanishing gas density is illustrated by using the progressive wave solution. Application of the results to the evolution of streamers and filaments observed in the solar corona is briefly discussed Title: The generation of magnetic fields in astrophysical bodies. XI. The effect of magnetic buoyancy on the growth and migration of dynamo waves in the sun. Authors: Parker, E. N. Bibcode: 1977ApJ...215..370P Altcode: The hydromagnetic dynamo equations are solved including a simple magnetic buoyancy term to demonstrate the effect of the buoyant rise of the magnetic field on the operation of the solar dynamo. The calculations show that the strength of the fluid motions necessary for the generation of field is sharply increased in a dynamo driven principally by vertical shear, as a consequence of the rapid, buoyant loss of field out of the free upper surface. In a dynamo driven by horizontal shear, such as the observed nonuniform rotation of the Sun, the necessary fluid motions are stronger or weaker depending upon whether the vertical migration of the dynamo waves is upward or downward, respectively. Unfortunately, our present ignorance of the fluid motions in the Sun excludes any more detailed conclusion than the general remark that the buoyancy has important quantitative effects on the operation of the solar dynamo. Subject headings: hydromagnetics - Sun: magnetic fields Title: A comment on the thermal structure of sunspots Authors: Parker, E. N. Bibcode: 1977MNRAS.179P..93P Altcode: Summary. It is pointed out that, at the present time, there is no certain explanation for the spontaneous self-concentration of magnetic fields to form the cool sunspots on the surface of the Sun. A brief discussion is presented, with comments on a recent paper by Cowling. Title: Comment on "the Elementary Theory of Twisted Flux Tubes. Equilibrium Configurations Authors: Parker, E. N. Bibcode: 1977ApJ...214..616P Altcode: It is pointed out that Wilson's calculations confirm the validity of our earlier results on the variation of fields along a slender force-free magnetic flux tube with slowly varying radius R(z) ( R/ z 1). The field distributions across tube are correct, neglecting terms O( R/ z) compared to one. Subject headings: hydromagnetics - Sun: magnetic fields Title: Cosmic-ray propagation and containment. Authors: Parker, E. N. Bibcode: 1977NASCP...2..283P Altcode: 1977scgr.nasa..283P; 1977NASCP.002..283P The cosmic rays are an active gaseous component of the disk of the galaxy, and their propagation and containment is a part of the general dynamics of the disk. The sources of cosmic rays are a matter of speculation. The disk is inflated by the cosmic-ray gas pressure, P, comparable to the magnetic pressure B super 2/ 8 pi, but the rate of inflation is unknown. The time spent by the individual cosmic-ray particles in the disk is inversely proportional to the cosmic-ray production rate and may be anything from 100,000 to more than 10 million years. It is evident from the decay of Be(10) that the cosmic rays circulate through a volume of space perhaps ten times the thickness of the gaseous disk, suggesting a magnetic halo extending out approximately 1 kpc from either face of the disk. The cosmic rays may be responsible for the halo by inflating the magnetic fields of the disk. Extension of the fields to 1 kpc would imply a high production rate and short life of cosmic rays in the dense gaseous disk of the galaxy. Title: The University of Chicago, Department of Astronomy and Astrophysics, Chicago, Illinois; The Yerkes Observatory, Williams Bay, Wisconsin. Observatory reports. Authors: Parker, E. N.; Hobbs, L. M. Bibcode: 1977BAAS....9...73P Altcode: No abstract at ADS Title: The origin of solar activity. Authors: Parker, E. N. Bibcode: 1977ARA&A..15...45P Altcode: The basis physical problems and principles of solar activity are reviewed, insofar as they are understood, concentrating on the general question of why magnetic fields produce activity. The continuous emergence of magnetic flux tubes through the solar surface is examined, the origin of solar magnetic fields is considered, and the behavior of the magnetic fields is investigated. Magnetic buoyancy is analyzed together with flux-tube twisting, the variation of twisting along a flux tube, magnetic-field concentration into isolated flux tubes, and dynamical dissipation of magnetic fields. It is concluded that the fluid motions which produce the magnetic fields in the convecting sun generally prevent the fields from achieving the perfect topological symmetry necessary for the existence of an equilibrium, that these fields should be active (i.e., perpetually in a state of reconnection), and that this seems to be the cause of the continuous activity of the magnetic fields which emerge through the surface of the sun. Title: Hydraulic concentration of fields in the solar photosphere. IV. Evolution of fields near equipartition. Authors: Parker, E. N. Bibcode: 1976ApJ...210..810P Altcode: It has previously been inferred that small isolated flux tubes appearing in supergranule boundaries are compressed to 1500 gauss or more. This paper considers whether some dynamic condition within a flux tube exists which provides both stability and a 'mechanical advantage' so that a small force over a small period of time can accomplish the enormous compression from the weak-field to the strong-field state. It is found that the equipartition solutions to the hydromagnetic equations apparently may have the desired property of permitting an infinitesimal external pressure to convert a gentle flow of gas along a weak field into a very intense field through a succession of equipartition states. An illustrative example is presented, and field compression by convective forces is analyzed. Title: Hydraulic Concentration of Fields in the Solar Photosphere. V. Dynamical Effects in a Stratified Atmosphere Authors: Parker, E. N. Bibcode: 1976ApJ...210..816P Altcode: The dynamical equations are presented for the steady flow of an inviscid ideal gas along a magnetic tube of force extending vertically across a stratified atmosphere with temperature T(z) in a uniform gravitational acceleration g. It is shown that under usual conditions an equilibrium dynamical solution extends across the full height of the atmosphere only if there is a point somewhere in the atmosphere where d(kT/mg)/dz = . If such a critical point exists, then the dynamical solutions extend across the atmosphere and possess the property of strong concentration of field in the general neighborhood of the critical point, where the fluid and field cross over equipartition, pV2 = B2/8ir. It is shown that the necessary condition on the temperature gradient is satisfied in the Sun in the top 50 km of the convective zone, suggesting that the observed concentration of magnetic field to 10 gauss or more in the photosphere is a localized phenomenon attributable at least in part to the dynamical flow of gas along the field. A crucial observational test for the occurrence of dynamical concentration would be a determination of the gas velocity ( j 5 km s -1) in the region of concentration. Subject headings: hydromagnetics - Sun: atmosphere - Sun: magnetic fields Title: Basic Properties of Magnetic Flux Tubes and Restrictions on Theories of Solar Activity Authors: Parker, E. N. Bibcode: 1976Ap&SS..44..107P Altcode: It is shown that the mean longitudinal field in a magnetic flux tube is reduced, rather than enhanced, by twisting the tube to form a rope. It is shown that there is no magnetohydrostatic equilibrium when one twisted rope is wound around another. Instead there is rapid line cutting (neutral point annihilation). It is shown that the twisting increases, and the field strength decreases, along a flux tube extending upward through a stratified atmosphere. These facts are at variance with Piddington's recent suggestion that solar activity is to be understood as the result of flux tubes which are enormously concentrated by twisting, which consist of several twisted ropes wound around each other, and which came untwisted where they emerge through the photosphere. Title: On the physical interpretation of the cosmic-ray transport equations. Authors: Jokipii, J. R.; Parker, E. N. Bibcode: 1976ApJ...208..220J Altcode: It is pointed out that an earlier paper (Jokipii and Parker, 1967) had discussed in detail the question of the interpretation of the energy-change terms in the general equation for cosmic-ray transport in the solar wind, so that no need exists to reassess the physical interpretation, as urged by Gleeson and Webb (1974). The question concerns the expression for the adiabatic deceleration, which is 'replaced' by an expression for the mean rate of change of momentum of fast particles. It is pointed out that these two expressions represent two essentially different quantities. The adiabatic deceleration refers to the mean rate loss of kinetic energy of an individual particle as a result of the expansion of the gas and magnetic field of the wind. This parameter can in no way depend on the gradient of the fast particle density, as does the mean rate of change of momentum of the fast particles. Title: Astronomers' Petition Authors: Schramm, David N.; Anders, Edward; Chandrasekhar, S.; Palmer, Patrick; Parker, Eugene; Simpson, J. A. Bibcode: 1976Sci...191.1124S Altcode: No abstract at ADS Title: Hydraulic concentration of magnetic fields in the solar photosphere. III. Fields of one or two kilogauss. Authors: Parker, E. N. Bibcode: 1976ApJ...204..259P Altcode: Detailed analysis of weak and strong lines suggests that the magnetic fields in isolated intense flux tubes in supergranule boundaries in the solar photosphere may be as large as 2000 gauss. This paper is a concise systematic review of hydrodynamic effects that might compress a magnetic field to great intensity. The properties of force-free fields are reviewed to show that they do not contribute to concentration of magnetic fields, in spite of the popular notion to the contrary. Of the seven effects considered, it is concluded that only cooling of the gas within the field can produce the high field densities inferred from observation. It is shown that inhibition of convection appears not to possess the necessary qualitative cooling features and that overstability, generating transverse hydromagnetic waves - essentially Alfven waves - is the only way to account for the cooling and field intensification. Title: The Enigma of Solar Activity Authors: Parker, E. N. Bibcode: 1976IAUS...71....3P Altcode: No abstract at ADS Title: The Acceleration of Particles to High Energy Authors: Parker, E. N. Bibcode: 1976ASIC...28..137P Altcode: 1976pntr.conf..137P No abstract at ADS Title: The Basic Physical Properties of a Galactic Magnetic Field Authors: Parker, E. N. Bibcode: 1976ASIC...28..169P Altcode: 1976pntr.conf..169P No abstract at ADS Title: University of Chicago, Department of Astronomy and Astrophysics, Chicago, Illinois; The Yerkes Observatory, Williams Bay, Wisconsin. Observatory reports. Authors: Parker, E. N.; Hobbs, L. M. Bibcode: 1976BAAS....8...54P Altcode: No abstract at ADS Title: The magnetic fields of planets Authors: Parker, E. N. Bibcode: 1976pspe.proc..812P Altcode: The magnetic fields of planets are considered, taking into account the history of the geomagnetic field characteristics, the magnetic field of Jupiter, the magnetic properties of Mars, the significance of a failure to detect signs of a magnetic field during the passage of Mariner 10 near Venus, the discovery of a magnetic field during the passage of Mercury, the absence of a lunar magnetic field, and the magnetic field of the sun. The causes of planetary magnetism are discussed and attention is given to dynamic considerations. Title: The escape of magnetic flux from a turbulent body of gas. Authors: Parker, E. N. Bibcode: 1975ApJ...202..523P Altcode: Topological conditions on the surface of a turbulent body of highly conductive fluid under which escape of magnetic force lines would be impossible (Drobyshevski, Yuferev 1974) are studied with exact calculation of intermediate field configurations as a possible explanation of the decay of stellar magnetic fields via turbulent mixing. It is shown that upward escape of magnetic force lines in the regions between convective cells is possible through rapid reconnection of the force lines (studied as neutral point annihilation) such as occurs continually in rapidly evolving sunspot groups. It is concluded that there exists no topological barrier to the escape of magnetic flux from the sun or from the local galaxy. Title: X-ray bright spots on the sun and the nonequilibrium of a twisted flux rope in a stratified atmosphere. Authors: Parker, E. N. Bibcode: 1975ApJ...201..494P Altcode: The calculations are concerned with the hydrostatic equilibrium of a magnetic flux tube whose two ends are anchored at some level in a stratified atmosphere. It is shown that no hydrostatic equilibrium exists if the whole flux tube is twisted more than a modest amount, equivalent to a 450 pitch over only one scale height. When the total twisting exceeds this small amount, the tube is subject to negative tension (compression) and buckles, spirals, and/or lengthens into a contorted form which causes rapid dissipation and reconnection of the magnetic field. The rapid dissipation continues until the excess azimuthal field is consumed and equilibrium is again possible. We suggest that the magnetic flux tubes in the Sun generally have more than the allowed twisting, so that, when they rise up through the surface, as a consequence of their buoyancy, they are subject to rapid dissipation, causing the phenomenon observed as the X-ray bright spot. Subject headings: hydromagnetics - Sun - X-rays, solar Title: Solar activity and the general absence of hydrostatic equilibrium in an azimuthal magnetic field. Authors: Parker, E. N. Bibcode: 1975ApJ...201..502P Altcode: It is shown that any temperature variation along the axis of symmetry of an azimuthal field causes continual convective activity. There is no static equilibrium configuration except in very special, and hence improbable, cases. It is suggested that this dynamic effect contributes to the activity associated with the flux tubes extending through the solar photosphere. The X-ray bright spots, evidently caused by the emergence and expansion of small bipolar regions, may be produced in part by the convective effect of an azimuthal field. Title: Comment on "The stabilizing effects of cloud reacceleration, microturbulence, and rotation on Parker's instability". Authors: Parker, E. N. Bibcode: 1975ApJ...201...74P Altcode: It is pointed out that the calculations in the paper by Zweibel and Kulsrud do not speak to the question of the instability and evolution of the gaseous disk of the Galaxy. Rather, they seem to treat the question of the statistical stability of the present turbulent dynamical state. Subject headings: hydromagnetics - interstellar matter - turbulence Title: The sun. Authors: Parker, E. N. Bibcode: 1975SciAm.233c..42P Altcode: 1975SciAm.233...42P The development of scientific knowledge of the sun is reviewed from Emden's first theoretical solar model (early 19th century) to the latest Skylab observations. Concepts dealt with include the solar wind, solar activity, energetic processes, thermonuclear generation of energy, and solar neutrinos. The carbon-nitrogen cycle and the proton-proton chain are outlined, and attempts at neutrino detection are discussed. Magnetohydrodynamic activity on the sun is described together with the nature and behavior of sunspots. Possible effects of sunspot activity on terrestrial weather are considered. Title: The Dynamo Mechanism for the Generation of Large-Scale Magnetic Fields Authors: Parker, E. N. Bibcode: 1975NYASA.257..141P Altcode: No abstract at ADS Title: The generation of magnetic fields in astrophysical bodies. X. Magnetic buoyancy and the solar dynamo. Authors: Parker, E. N. Bibcode: 1975ApJ...198..205P Altcode: The magnetic field appearing as bipolar magnetic regions at the surface of the sun represents the lines of force from a general azimuthal field of the order of 100 gauss somewhere beneath the surface. The amplification time, as a consequence of the nonuniform rotation, is of the order of 10 years. But magnetic buoyancy brings the azimuthal field up through much of the convective zone in a time rather less than 10 years, raising the question of where the azimuthal field can be retained long enough to be amplified. We show that magnetic fields can be retained for long periods of time in the stable radiative region beneath the convective zone, but unfortunately the solar dynamo cannot function there because turbulent diffusion is an essential part of its operation. The only possible conclusion appears to be that the dynamo operates principally in the very lowest levels of the convective zone at depths of 150,000 km or more, where the gas density is 0.1 g/cu cm, and the fields are limited to 50 gauss. Title: The Nature of the Sunspot Phenomenon. IV: The Intrinsic Instability of the Magnetic Configuration Authors: Parker, E. N. Bibcode: 1975SoPh...40..291P Altcode: It is pointed out that the equilibrium configuration of a sunspot magnetic field, confined to the cool umbra by the pressure of the surrounding photospheric gas, is unstable to the familiar hydromagnetic exchange instability. The characteristic time for dissolution of the sunspot is of the order of one hour. Title: The Nature of the Sunspot Phenomenon. III: Energy Consumption and Energy Transport Authors: Parker, E. N. Bibcode: 1975SoPh...40..275P Altcode: This paper points out the basic relation between the conversion of thermal energy into convective fluid motion (Alfvén waves when a strong vertical magnetic field is present) and the convective transport of thermal energy. It is shown that heat transport necessarily accompanies convective driving of fluid motion. Convective motions restricted to a layer whose thickness is a small fraction of the local scale height can divert no more than the same fraction of the energy into Alfvén waves. But if the convecting layer extends over many scale heights, then the convective forces may convert more energy into fluid motion than they transport. Hence the creation of a cool sunspot requires convection extending coherently over several scale heights, at least 500 km. This requirement is basically just the familiar thermodynamic efficiency of an ideal heat engine. The calculations establish that convection need not be much less efficient than the ideal. Title: Book Review: Cosmic gas dynamics. EVRY SCHATZMAN and LUDWIG BIERMANN: John Wiley, New York, 1974. xv + 291 pp. £8.40 Authors: Parker, E. N. Bibcode: 1975P&SS...23..388P Altcode: No abstract at ADS Title: The dynamo mechanism for the generation of large-scale magnetic fields. Authors: Parker, E. N. Bibcode: 1975NYASA.257Q.141P Altcode: No abstract at ADS Title: The University of Chicago, Department of Astronomy and Astrophysics, Chicago, Illinois; The Yerkes Observatory, Williams Bay, Wisconsin. Observatory reports. Authors: Parker, E. N.; Hobbs, L. M. Bibcode: 1975BAAS....7...25P Altcode: No abstract at ADS Title: The dynamo mechanism for the generation of larg-scale magnetic fields. Authors: Parker, E. N. Bibcode: 1975NYASA.257R.141P Altcode: No abstract at ADS Title: The Instability of Strong Magnetic Fields in Stellar Interiors Authors: Parker, E. N. Bibcode: 1974Ap&SS..31..261P Altcode: There has been discussion of the possibility of resolving the solar neutrino dilemma with a sufficiently strong magnetic field (5×108 G) in the solar interior to relieve the gas pressure by some ten percent or more. We examine the time in which magnetic buoyancy will bring a strong field to the surface and find it to be less than 108 yr. We see no possibility for retaining a suitably strong magnetic field in the solar interior. Title: The Nature of the Sunspot Phenomenon. II: Internal Overstable Modes Authors: Parker, E. N. Bibcode: 1974SoPh...37..127P Altcode: The properties of Alfvén waves in a vertical column of field are pointed out as a guide in treating the complicated problem of overstability. There are internal Alfvén waves of arbitrary form propagating along the magnetic field, without disturbing the fluid outside the column. There are also surface waves which involve the fluid both inside and outside the column of field. The surface waves propagate at a speed less than the Alfvén speed. Title: The Dynamical Properties of Twisted Ropes of Magnetic Field and the Vigor of New Active Regions on the Sun Authors: Parker, E. N. Bibcode: 1974ApJ...191..245P Altcode: The equilibrium configuration following expansion of all, or part, of a force-free magnetic rope is worked out formally from the hydromagnetic equilibrium equations. It is shown that expansion of a portion of the length of a long magnetic rope beyond a certain radius causes the expanded portion to be wrapped with an azimuthal field composed of lines of force from the surface layer of the unexpanded portion. This singular redistribution takes an extended period of time to achieve. Further, it automatically causes the expanded portion to become unstable to buckling. We suggest that the restless behavior of the magnetic fields in new active regions in the solar photosphere is largely a result (a) of the buckling brought about by the expansion of the fields as they emerge through the photosphere, and (b) of the long-term redistribution of the surface lines of force onto the expanded portion of the rope. Subject headings: hydromagnetics - magnetic fields, solar - solar activity Title: Hydraulic Concentration of Magnetic Fields in the Solar Photosphere. II. Bernoulli Effect Authors: Parker, E. N. Bibcode: 1974ApJ...190..429P Altcode: The magnetic filaments in the solar photosphere are subject to vigorous kneading and massaging by the convective turbulence at, and beneath, the visible surface. It is shown that the Bernoulli effect of the consequent surging of fluid up and down along the filaments is a major factor in concentrating the magnetic pressure of the filament (the mean square field). The mean field is also increased if the phase velocity of the external massaging exceeds the Alfven speed within the filament. The net observational magnetic result of the surging, then, depends upon the response of the observing instrument, and whether it essentially observes the mean field, the rms field, or whether there are saturation effects. The hydraulic effects responsible for the formation of the concentrated magnetic filaments are part of the dynamical picture of spicules, pointed out a decade ago. Hence we suggest that the chromospheric mottles (spicules) seen in Ha are in fact the intense magnetic filaments that carry most of the magnetic flux across the photospheric boundary of the Sun. Subject headings: granules and supergranules, solar - hydromagnetics - magnetic fields, solar Title: The Nature of the Sunspot Phenomenon. I: Solutions of the Heat Transport Equation Authors: Parker, E. N. Bibcode: 1974SoPh...36..249P Altcode: Heat transport in the Sun is describable by a Fokker-Planck, or diffusion, transfer equation. A study of the general character of the solutions of the transfer equation shows that the inhibition of convective transport beneath the photosphere produces a photospheric dark ring surrounded by a bright ring, or at best, a dark area surrounded by a bright ring. The mean temperature beneath the `sunspot' is unavoidably above normal, so that the enhanced gas pressure would disperse, rather than concentrate, the magnetic field. Hence we conclude that the inhibition of convection cannot be the cause of a sunspot. Title: Hydraulic Concentration of Magnetic Fields in the Solar Photosphere. I. Turbulent Pumping Authors: Parker, E. N. Bibcode: 1974ApJ...189..563P Altcode: Observations suggest that most of the magnetic flux through the solar photosphere is concentrated in vertical filaments in the supergranule boundaries. Each filament appears to contain about 3 x 10' maxwells, in the form of a field of 500 gauss or more, over a diameter of 700 km or less. The magnetic energy density in the filaments is 100 times the observed kinetic energy density of the observed supergranule motions, but comparable to the kinetic energy density of the granules. Force-free field configurations cannot duplicate the observational numbers, nor can such cooling effects as are believed responsible for the intense fields in sunspot umbrae. We point out a simple hydraulic mechanism- turbulent pumping that appears to account for the observed concentration of fields. The mechanism is treated by using the simple mixing-length theory of convection and turbulence. Subject headings: atmospheres, solar - granules and supergranules, solar hydromagnetics - turbulence Title: The University of Chicago: Department of Astronomy and Astrophysics, Chicago, Illinois; The Yerkes Observatory, Williams Bay, Wisconsin 1972-1973. Observatory reports. Authors: Parker, E. N.; van Altena, W. F. Bibcode: 1974BAAS....6R..15P Altcode: No abstract at ADS Title: The University of Chicago, Department of Astronomy and Astrophysics, Chicago, Illinois; The Yerkes Observatory, Williams Bay, Wisconsin 1972-1973. Observatory reports. Authors: Parker, E. N.; van Altena, W. F. Bibcode: 1974BAAS....6Q..15P Altcode: No abstract at ADS Title: Comment on "galactic Magnetic Fields: Cellular or Filamentary STRUCTURE?" Authors: Parker, E. N. Bibcode: 1974ApJ...187..191P Altcode: The recent statistical studies of Michel and Yahil emphasize again the difficulty in interpreting the observed Faraday rotation measure in terms of an unambiguous model of the galactic magnetic field. We have difficulty in understanding their specific suggestion that the magnetic fields expelled from stars have anything to do with the model. Subject headings: interstellar matter magnetic fields - solar wind Title: Convection and Magnetic Fields in an Atmosphere with Constant Temperature Gradient. II. The Supergranules and Magnetic Fields Authors: Parker, E. N. Bibcode: 1973ApJ...186..665P Altcode: The hydrodynamic properties of convective motions in a stratified atmosphere suggest that e supergranules in the solar photosphere extend to depths in excess of their horizontal diameters. The calculations presented here show that the weak fields which appear at the photosphere are as strong as, or stronger than, the horizontal fields anywhere in the supergranules below the surface. Hence the general gauss azimuthal field of the Sun, whose presence is indicated by the emerging bipolar magnetic regions, must lie below the base of the supergranules, i.e., below a depth probably of the order of 2-5 x i0 km. Presumably then the azimuthal field is generated by nonuniform rotation below the supergranule convection and does not appear in the supergranule layer because of the high rate of turbulent diffusion loss from that layer. Subject headings: atmospheres, solar - granules, solar - hydromagnetics Title: Convection and Magnetic Fields in an Atmosphere with Constant Temperature Gradient. I. Hydrodynamic Flows Authors: Parker, E. N. Bibcode: 1973ApJ...186..643P Altcode: In order to deduce the fluid and field conditions deep in the supergranules from the fluid motions and magnetic fields observed in the solar photosphere, it is necessary to have some idea of the depth to which the supergranules extend and the form of their internal fluid velocities. Toward this end a number of analytic solutions of the Navier-Stokes equations are given for circumstances possessing various facets of the supergranule environment in the Sun. These solutions, together with the earlier work by others, shows that the granules extend to depths in excess of their mean diameters, that the convective velocities probably do not diminish much, if any, with depth, and that across the tops of the supergranules at the photosphere the horizontal velocity is more or less independent of depth. Subject headings: atmospheres, solar - granules, solar - hydrodynamics Title: Extragalactic Cosmic Rays and the Galactic Magnetic Field Authors: Parker, E. N. Bibcode: 1973Ap&SS..24..279P Altcode: The origin and behavior of cosmic rays in the Galaxy depends crucially upon whether the galactic magnetic field has a closed topology, as does the field of Earth, or whether a major fraction of the lines of force connect into extragalactic space. If the latter, then cosmic rays could be of extragalactic origin, or they could be of galactic origin, detained in the Galaxy by the scattering offered by hydromagnetic waves, etc. If, on the other hand, the field is largely closed, then cosmic rays cannot be of extragalactic origin (at least below 1016 eV). They must be of galactic origin and escape because their collective pressure inflates the galactic field and they push their way out. This paper examines the structure of a galactic field that opens initially into intergalactic space and, with the inclusion of turbulent diffusion, finds no possibility for maintaining a significant magnetic connection with an extragalactic field. Unless some mechanism can be found, we are forced to the conclusion that the field is closed, that cosmic rays are of galactic origin, and that cosmic rays escape from the Galaxy only by pushing their way out. Title: The Generation and Dissipation of Solar and Galactic Magnetic Fields Authors: Parker, E. N. Bibcode: 1973Ap&SS..22..279P Altcode: Turbulent diffusion of magnetic field plays an essential role in the generation of magnetic field in most astrophysical bodies. This paper reviews what can be proved, and what can be believed, about the turbulent diffusion of magnetic field. Observations indicate the dissipation of magnetic field at rates that can be understood only in terms of turbulent diffusion. Theory shows that a largescale weak magnetic field diffuses in a turbulent flow in the same way that smoke is mixed throughout the fluid by the turbulence. The small-scale fields (produced from the large-scale field by the turbulence) are limited in their growth by reconnection of field lines at neutral points, so that the turbulent mixing of field and fluid is not halted by them. Altogether, it appears that the mixing of field and fluid in the observed turbulent motions in the Sun and in the Galaxy is unavoidable. Turbulent diffusion causes decay of the general solar fields in a decade or so, and of the galactic field in 108 109 yr. We conclude that continual dynamo action is implied by the observed existence of the fields. Title: Cosmic Rays in the Outer Solar System (Article published in the Space Science Reviews special issue on 'Outer Solar System Exploration - An Overview', ed. by J. E. Long and D. G. Rea.) Authors: Parker, E. N. Bibcode: 1973SSRv...14..576P Altcode: A space mission to Jupiter and Saturn, and beyond, provides an opportunity to explore the low energy galactic cosmic rays, which are largely excluded from the inner solar system by the outward sweep of the magnetic fields in the solar wind. The low energy cosmic rays are believed to be responsible for much of the heating of the gaseous disk of the galaxy, so a measurement of their intensity will have far reaching effects on theories of the interstellar gas and the evolution of the galaxy. The nuclear abundances, and in particular the presence or absence of high Z nuclei, will give critical information on the proximity of cosmic ray sources. Title: The Reconnection Rate of Magnetic Fields Authors: Parker, E. N. Bibcode: 1973ApJ...180..247P Altcode: Solar flares, and the absence of intense small-scale magnetic fields in the turbulent solar photosphere, suggest that the reconnection rate, or merging speed, of two oppositely directed magnetic fields is of the general order of the Alfve'n speed. The fluid between the opposite fields escapes via the well-known interchange and kink instabilities, permitting rapid close approach of the fields, and merging rates probably of the order of 0.1 VA, or faster, in most cases. Hence reconnection is sufficiently rapid, with or without microinstabilities, that it plays a major role in solar flares and in the reduction of small-scale turbulent fields. Subject headings: flares, solar - hydromagnetics - magnetic fields, solar - turbulence Title: Comments on the reconnexion rate of magnetic fields Authors: Parker, E. N. Bibcode: 1973JPlPh...9...49P Altcode: The reconnexion rate of magnetic fields is crucial in understanding the fields found in turbulent flows in the solar photosphere and in the galaxy, and in flare phenomena. This paper examines the behaviour of magnetic fields in the neighbourhood of an X-type neutral point. The treatment is kinematical, specifying the velocity field v and constructing solutions to the hydromagnetic equation for B. The calculations demonstrate that the reconnexion rate is controlled by the diffusion in the near neighbourhood of the neutral point, and is not arbitrarily large, as has been suggested by similarity solutions of the complete field and fluid equations for vanishing diffusion Title: A strategy for investigation of the outer solar system. Outer planets, their satellites, and particles and fields at great distances from the sun. Authors: Münch, G.; Hunten, D. M.; Kliore, A. J.; Lewis, J. S.; McElroy, M. B.; Spencer, N. W.; Stone, P. H.; Wetherill, G. W.; Cameron, A. G. W.; Hubbard, W. B.; Murray, B. C.; Peale, S. J.; van Allen, J. A.; Axford, W. I.; Gulkis, S.; Kennel, C. F.; Montgomery, M. D.; Parker, E. N.; Sonett, C. P.; Stone, R. G.; Trainor, J. H.; Rea, D. G.; Long, J. E.; Padrick, B. D. Bibcode: 1973SSRv...14..347M Altcode: No abstract at ADS Title: (Inaugural Lecture) What We Think We Know and Do Not Know About Solar Flares Authors: Parker, E. N. Bibcode: 1973str..conf....1P Altcode: No abstract at ADS Title: The Generation of Magnetic Fields in Astrophysical Bodies.IX. a Solar Dynamo Based on Horizontal Shear Authors: Lerche, I.; Parker, E. N. Bibcode: 1972ApJ...176..213L Altcode: In view of the uncertainty in the angular velocity (r, 0) in the solar interior, we have worked out the general behavior of the solar dynamo for horizontal shear (() /aO) for comparison with the earlier models based on vertical shear (a /ar). The horizontal shear produces greater complexity, with the fields at the surface migrating toward the equator (for a uniform distribution of shear and cyclonic convection) and a layer of counter migrating fields at the bottom of the dynamo. More important, perhaps, the horizontal shear excites the even and odd modes equally, whereas vertical shear excites the odd mode before the even mode. Title: Topological Dissipation and the Small-Scale Fields in Turbulent Gases Authors: Parker, E. N. Bibcode: 1972ApJ...174..499P Altcode: It is shown that a large-scale magnetic field possesses a hydrostatic equilibrium only if the pattern of small-scale variations is uniform along the large-scale field. Thus equilibrium obtains only if the variations in the field consist of simple twisting of the lines, with the twists extending uniformly the full length of the field. Any more complicated topology, such as two or more flux tubes wrapped around each other to form a rope, or braided or knotted flux tubes, is without equilibrium, no matter what fluid pressures are applied along the individual lines of force. The result is rapid dissipation and field-line merging, which quickly reduces the topology to the simple equilibrium form. It follows from this general theorem that line merging has important consequences in turbulent fields. In spite of large magnetic Reynolds numbers of the individual eddies, the line merging reduces the small-scale fields in the turbulence below the value for equipartition with the turbulence. The effect has important astrophysical implications. It explains the absence of strong small-scale fields in the solar photosphere and in interstellar space in spite of the vigorous turbulence. Title: Present Developments in Theory of the Solar Wind Authors: Parker, E. N. Bibcode: 1972NASSP.308..161P Altcode: 1972sowi.conf..161P No abstract at ADS Title: The dynamical behavior of the interstellar gas, field, and cosmic rays Authors: Parker, E. N. Bibcode: 1972cpp..conf..195P Altcode: No abstract at ADS Title: The Generation of Magnetic Fields in Astrophysical Bodies. VII. The Internal Small-Scale Fields Authors: Lerche, I.; Parker, E. N. Bibcode: 1971ApJ...168..231L Altcode: The paper investigates the small-scale magnetic fields B generated, along with the large-scale magnetic fields B, by cyclonic turbulence and large-scale shear. The results are directly applicable to the problem of the generation of magnetic fields in the Galaxy,for which the observations show only the complexity of the small- and large-scale fields together, making it difficult to discover the actual configuration of the large-scale galactic field. The calculations show that the fluctuations in the generaijon of field in the Galaxy contribute a (( B)1) comparable to (B1). Title: The Generation of Magnetic Fields in Astrophysical Bodies. VIII. Dynamical Considerations Authors: Parker, E. N. Bibcode: 1971ApJ...168..239P Altcode: It is pointed out that the kinetic energy of the differential rotation of the Galaxy is sufficient to maintain generation of the galactic magnetic field for a period of time in excess of 10's years. In the Sun, on the other hand, the nonuniform rotation must be driven by thermal convective forces, etc. Magnetic buoyancy of the azimuthal field B is an important energy source in the Sun, nd contributes to the generation of the poloidal of the solar field. In the Galaxy the magnetic buoyancy of B contributes to the generation of the poloidal field, but if present observational estimates are correct, the inflation of the gaseous disk of the Galaxy by cosmic rays is a major source of the energy generating the poloidal component of the galactic poloidal field. The dynamical-dynamo equations are solved in the linear approximation to illustrate the direct generation of poloidal field from magnetic buoyancy and from cosmic-ray inflation. Title: Recent Developments in Theory of Solar Wind Authors: Parker, E. N. Bibcode: 1971RvGSP...9..825P Altcode: 1971RvGeo...9..825P No abstract at ADS Title: The Generation of Magnetic Fields in Astrophysical Bodies.VI. Periodic Modes of the Galactic Field Authors: Parker, E. N. Bibcode: 1971ApJ...166..295P Altcode: It is shown from the dynamo equations that the cyclonic turbulence and nonuniform rotation of the gaseous disk of the Galaxy generate magnetic field in both periodic and nonperiodic modes. Order-ofmagmtude estimates of the dynamo number suggest that the large-scale galactic field is generated in the lowest even periodic and/or nonperiodic modes. The characteristic period of the periodic mode is estimated at 108 years. The large amplitude of the small-scale (lO pc) fluctuations in the internal field of the Galaxy make it difficult to compare the local field observations with theory to designate the mode of the large-scale field extending throughout the disk. Title: The Generation of Magnetic Fields in Astrophysical Bodies. V. Behavior at Large Dynamo Numbers Authors: Parker, E. N. Bibcode: 1971ApJ...165..139P Altcode: There is the theoretical possibility that some astrophysical objects may have large dynamo numbers, generating fields in high modes. The effect of the boundaries is diminished, and it is profitable to consider the fields in terms of the four basic wave modes of the dynamo. Normal incidence and reflection of dynamo waves from boundaries are worked out. Dynamo wave packets are discussed briefly, and a pseudoillustration of the solar dynamo is presented. The purpose of the calculations is to illustrate some of the behavior at large dynamo numbers, to aid in observational recognition. Title: The Generation of Magnetic Fields in Astrophysical Bodies.IV. The Solar and Terrestrial Dynamos Authors: Parker, E. N. Bibcode: 1971ApJ...164..491P Altcode: This paper explores the question of why the magnetic field of Earth is quasi-stationary in time while the field of the Sun is quasi-periodic. Both fields are believed to be produced by a combination of nonuniform rotation and cyclonic turbulence, or Rossby waves. The calculations show that small dynamo numbers lead to stationary states, producing a dipole when the dynamo number is negative in the northern hemisphere, as in Earth. The dynamo number in the northern hemisphere of the Sun is positive, but fails to produce the stationary quadrupole field because of the high dissipation associated with the thinness of the convective region. The lowest mode available in the Sun is periodic in time, with the fields an odd function of latitude, as observed. The calculations show that a modest increase in the dynamo number in the Sun excites the quadrupole mode. In view of the observed north-south asymmetry of the solar magnetic fields, the periodic quadrupole mode may be excited much of the time. The important consequences of magnetic variation of the Sun for the space environment of Earth suggest that a more general theoretical exploration of the dynamo equations in spherical coordinates should be carried out. Title: The Dynamical Effects of Cosmic Rays in the Galaxy and the Generation of the Galactic Magnetic Field. Authors: Parker, E. N. Bibcode: 1971ICRC....8...95P Altcode: 1971ICRC........95P; 1971ICRC...12h..95P No abstract at ADS Title: The Generation of Magnetic Fields in Astrophysical Bodies. III. Turbulent Diffusion of Fields and Efficient Dynamos Authors: Parker, E. N. Bibcode: 1971ApJ...163..279P Altcode: It is shown v formal calculation that the probability distribution of magnetic field carried in a turbulent fluid varies with the time in a manner identical with the probability distribution of a scalar field carried in the same turbulence. Then if Kraichnan's results are used for the diffusion of scalar fields, the effective turbulent-diffusion coefficient is 0.15 `u/k5, where u is the rms velocity of the turbulence and k0 is the wavenumber of the large eddies. In the gaseous disk of the Galaxy this gives 3 X I0 cm2 . It follows from this large value of that the galactic field cannot be primordial, but is automatically generated by the nonuniform rotation and turbulence throughout the gaseous disk. Title: The Generation of Magnetic Fields in Astrophysical Bodies. II. The Galactic Field Authors: Parker, E. N. Bibcode: 1971ApJ...163..255P Altcode: The gaseous disk of the Galaxy is subject to nonuniform rotation and internal turbulence. The rotation causes the turbulence to be cyclonic. Formal solution of the dynamo equations in a slab of gas, representing the galactic disk, produces regenerative modes, in which the aximutal field is an even function of the distance a from the central plane of the slab. Inclusion of the ` eddy diffusivity" of the turbulence in the dissipation terms of the dynamo equations gives growth times of 108 years. Hence we suggest that the magnetic field of the Galaxy is generated by the combination of nonuniform rotation and turbulence in the gaseous disk. The dynamo principle responsible for the magnetic field of Earth and of tlie Sun appears to be operative on a galactic scale, too. Title: Magnetic fields in astrophysics. Authors: Parker, E. N. Bibcode: 1971JAP....42.1464P Altcode: Magnetic fields appear in association with most astrophysical objects and spaces. Their general effect is to promote fast-particle and enhanced-temperature activity. It appears that the magnetic fields are generated by the combined nonuniform rotation and cyclonic turbulence of the objects. The nonuniform rotation shears the fields, producing strong fields in the azimuthal direction. The cyclonic turbulence interacts with the azimuthal field Bφ generating azimuthal vector potential Aφ at a rate described by the dynamo equation (∂/∂t-η▿2) Aφ = ΓBφ, where Γ is essentially the cyclonic velocity of the turbulence. The fields of Earth, the Sun, and the galaxy appear to be generated in this way. Title: Theoretical aspects of the worldwide magnetic storm phenomenon. Authors: Parker, E. N.; Ferraro, V. C. A. Bibcode: 1971HDP....49..131P Altcode: No abstract at ADS Title: Universal magnetic fields. Authors: Parker, E. N. Bibcode: 1971AmSci..59..578P Altcode: No abstract at ADS Title: The Generation of Magnetic Fields in Astrophysical Bodies. I. The Dynamo Equations Authors: Parker, E. N. Bibcode: 1970ApJ...162..665P Altcode: The paper presents a formal derivation of the dynamo equations describing the generation of largescale magnetic fields by small-scale cyclonic turbulence (or convection) in a rotating fluid body. The derivation is based on the simple approximation that the individual turbulent cells are small and shortlived. The dynamo equations show that large-scale magnetic fields are generated at a very high rate, in periods comparable to the time of nonuniform rotation. The dynamo equations describe the generation of the quasi-steady field of Earth and the migratory field of the Sun, in characteristic times of 10 and 10 years, respectively. Title: Comments on `Steady state charge neutral models of the magnetosphere' Authors: Lerche, I.; Parker, E. N. Bibcode: 1970Ap&SS...8..140L Altcode: No abstract at ADS Title: The Origin of Magnetic Fields Authors: Parker, E. N. Bibcode: 1970CoASP...2..127P Altcode: 1970ComAp...2..127P No abstract at ADS Title: The Origin of Magnetic Fields Authors: Parker, E. N. Bibcode: 1970ApJ...160..383P Altcode: No abstract at ADS Title: on the Convection, Diffusion, and Adiabatic Deceleration of Cosmic Rays in the Solar Wind Authors: Jokipii, J. R.; Parker, E. N. Bibcode: 1970ApJ...160..735J Altcode: We present a generalization and clarification of work on the transport of cosmic rays in the solar system. The general equations for the cosmic-ray density and flux, in the anisotropic-diffusion approximation, are derived in the frame of reference moving with the solar wind, and the transformation to the fixed frame is discussed. Only if the particle density varies smoothly with energy does one obtain a straightforward generalization of equations derived previously for isotropic diffusion. In this approximation we write down, for the first time, the correct differential equations for the particle density and flux for anisotropic diffusion. If the density varies sharply with energy, more complex integro-differential equations arise. We conclude that existing alternative derivations, based on the Boltzmann equation, are in general not adequate for either anisotropic-diffusion or energy transformations. Title: The Origin of Solar Magnetic Fields Authors: Parker, E. N. Bibcode: 1970ARA&A...8....1P Altcode: No abstract at ADS Title: The Origin and Dynamical Effects of the Magnetic Fields and Cosmic Rays in the Disk of the Galaxy Authors: Parker, E. N. Bibcode: 1970IAUS...39..168P Altcode: No abstract at ADS Title: Report on quasi-stationary modulation papers. Authors: Parker, E. N. Bibcode: 1970ICRC....5..341P Altcode: 1970ICRC...11e.341P; 1969ICRC.......341P No abstract at ADS Title: Interstellar Gas and Field Authors: Parker, E. N.; Lerche, I. Bibcode: 1969CoASP...1..215P Altcode: 1969ComAp...1..215P No abstract at ADS Title: The Occasional Reversal of the Geomagnetic Field Authors: Parker, E. N. Bibcode: 1969ApJ...158..815P Altcode: It is presently believed that the geomagnetic field is generated by the combined effects of the cyclonic convective motions and the nonuniform rotation of the liquid core of Earth. Fossil magnetism shows that the fie'd remains steady for periods of the order of 1O6~1O7 years, and then, at apparently random times, reverses abruptly, thereafter remaining steady for another 1O~-1O~ years, etc. We do not believe that the reversal of the field is caused by a temporary change in the sign of the cyclonic or nonuniform rotations, since the signs of both are determined by the Coriolis forces of the rotating Earth. We demonstrate that a statistical fluctuation in the distribution of the fifteen to twenty cyclonic con~ vective cells in the core produces an abrupt reversal of the geomagnetic field. The simplest fluctuation lead- ing to reversal is a general absence of cyclones below about 300 latitude for a time comparable to the life (`-%`1O~ years) of the individual cell. Assuming that the convective cells are statistically independent of each other, we estimate that such a fluctuation might occur once in 1O~ years. The simplicity of the mechanism recommends it as the explanation for the reversal of the field at random intervals Title: Amplification of Weak Magnetic Fields in Turbulent Flow Authors: Parker, E. N. Bibcode: 1969ApJ...157.1119P Altcode: The problem of a weak magnetic field carried in a turbulent-velocity field is considered under the circumstance that the velocity field is a prescribed random function of space and time. It is assumed that the time over which the velocity field is correlated with itself is very short. In this approximation the theory of random functions is used to show that the velocity field amplifies the magnetic field at all wave- numbers. Thus the calculation establishes that the large-scale components of a magnetic field in a turbu- lent-velocity field grow without limit as long as the velocity field is maintained. The unlimited amplifica- tion is of interest in astrophysical problems Title: Origin of the Magnetic Field of the Galaxy Authors: Parker, E. N. Bibcode: 1969ApJ...157.1129P Altcode: A recent formal calculation demonstrates that the individual Fourier components of a magnetic field are stochastic variables when the field is carried in a random turbulent velocity V~(r,t). The indi- vidual Fourier components random-walk, with the result that their mean squares increase with time. The calculation is applicable to the Galaxy when the magnetic field is sufficiently weak (B < 1O~ gauss). Application to the gaseous disk of the Galaxy indicates that a field of 1O~ gauss would be created in less than 1O~ years. The present orientation and large scale of the field along the galactic arm are presumably the result of the nonuniform rotation of the Galaxy. We conclude that turbulence is the most powerful source of magnetic field in the Galaxy, and that the present galactic magnetic field is the result of such turbulence. I. INTRODUCTIO Title: Galactic Effects of the Cosmic-Ray Gas Authors: Parker, E. N. Bibcode: 1969SSRv....9..651P Altcode: On an astronomical scale cosmic rays must be considered a tenuous and extremely hot (relativistic) gas. The pressure of the cosmic-ray gas is comparable to the other gas and field pressures in interstellar space, so that the cosmic-ray pressure must be taken into account in treating the dynamical properties of the gaseous disk of the galaxy. This review begins with a survey of present knowledge of the cosmic-ray gas. Then the kinetic properties of the gas are developed, followed by an exposition of the dynamical effects of the cosmic-ray gas on a large-scale magnetic field embedded in a thermal gas. The propagation of low-frequency hydromagnetic waves is worked out in the fluid approximation. The dynamical properties of the gaseous disk of the galaxy are next considered. The equations for the equilibrium distribution in the direction perpendicular to the disk are worked out. It is shown that a self-consistent equilibrium can be constructed within the range of the observational estimates of the gas density, scale height, turbulent velocity, field strength, cosmic-ray pressure, and galactic gravitational acceleration. Perturbation calculations then show that the equilibrium is unstable, on scales of a few hundred pc and in times of the order 2 × 107 years. The instability is driven about equally by the magnetic field and the cosmic-ray gas and dominates self-gravitation. Hence the instability dominates the dynamics of the interstellar gas and is the major effect in forming interstellar gas clouds. Star formation is the end result of condensation of the interstellar gas into clouds, indicating, then, that cosmic rays play a major role in initiating star formation in the galaxy. The cosmic rays are trapped in the unstable gaseous disk and escape from the disk only in so far as their pressure is able to inflate the magnetic field of the disk. The observed scale height of the galactic disk, the short life (106 years) of cosmic-ray particles in the disk of the galaxy, and their observed quiescent state in the disk, indicate that the galactic magnetic field acts as a safety valve on the cosmic ray pressure P so that P≅B 2/8π. We infer from the observed life and quiescence of the cosmic rays that the mean field strength in the disk of the galaxy is 3 5 × 10-6 gauss. Title: Theoretical Studies of the Solar Wind Phenomenon Authors: Parker, E. N. Bibcode: 1969SSRv....9..325P Altcode: This paper is a review of current theoretical topics concerning the solar wind. Broadly speaking the questions outstanding at the present time concern the loss of angular momentum to the sun, the origin of the fluctuations observed in the wind at the orbit of earth, conditions in the wind in regions yet unvisited by spacecraft (inside the orbit of Venus, beyond the orbit of Mars, and out of the plane of the ecliptic), conditions at the terminus of the wind, etc. The question of angular momentum loss is important in understanding the evolution of the sun to its present form with a slowly rotating surface. Evidence from both comet and spacecraft observations of the wind indicate that the rate at which angular momentum is being carried away by the solar wind is very large, of the order of 1031 dyne/cm in the gas flow and half as much by the interplanetary magnetic field. But theory cannot account for more than about 1030 dynes/cm in the gas without special assumptions. The fluctuations presently observed in the wind at the orbit of earth have scales ranging upward from 102 km. Their presence is puzzling because fluctuations with scales less than about 106 km are not expected to survive from the sun. Presumably, therefore, the fluctuations are generated by the velocity differences of more than 100 km/sec in the wind from different regions in the solar corona and by instabilities produced by the anisotropy of the electrons of the wind plasma. Conditions in the wind at places far removed from the orbit of earth can be inferred from the behavior of cosmic rays. The evidence is that the wind becomes relatively placid beyond about 5 AU, extending from there out to 30 300 AU without much small-scale turbulence. There are also some suggestions that the wind may perhaps be less turbulent toward the sun from 1 AU, and that the wind may be faster and more turbulent at higher solar latitudes. But the ambiguity of the situation does not permit a firm conclusion on this yet. Title: Stochastic Aspects of Magnetic Lines of Force with Application to Cosmic-Ray Propagation Authors: Jokipii, J. R.; Parker, E. N. Bibcode: 1969ApJ...155..777J Altcode: It is pointed out that magnetic lines of force in nature are generally stochastic and ergodic. Owing to unavoidable fluctuations in the field, adjacent lines of force random-walk away from each other. The stochastic properties of the lines of force in the astrophysical universe are related to the stochastic prop- erties of the (turbulent) velocity fields in which they are imbedded. The consequent random walk of the field lines is shown to contribute appreciably to K1, the coefficient for particle diffusion normal to the average field, with the result that the particles are spread across the average magnetic field much more rapidly than expected from the usual resonant scattering by small-scale irregularities. The Sun's extended magnetic field, traversed by both energetic solar particles and galactic cosmic rays, serves as an excellent illustration of these concepts. Application of the theory to the interplanetary magnetic fields shows that the random walk of the field lines is determined by the observed power spec- trum of the fluctuations in the magnetic field at zero frequency. The observed turbulent velocity field in the solar photosphere yields a random walk equal to that obtained from the observed power spectrum of the magnetic field. These two determinations of the random walk of the field lines, in turn, agree with the observed spread in solar longitude of promptly arriving solar cosmic rays. The observed shear planes and flux tubes of the "wet spaghetti" model of the interplanetary magnetic field are evidently a direct manifestation of the photospheric supergranulation. We also discuss the diffusion of cosmic rays in the interplanetary magnetic field observed near solar minimum. For protons with energies of 10 MeV and below, the ratio KL/KII at the orbit of the Earth becomes comparable to unity, instead of nearly zero as would be expected on the basis of resonant scat- tering alone. The contribution of the random walk to K~ is also significant at relativistic energies. Applica- tion to the theory of the diurnal variation of galactic cosmic rays agrees with observation both at `-~.-`1O MeV and at relativistic particle energies Title: Cosmic-Ray Life and the Stochastic Nature of the Galactic Magnetic Field Authors: Jokipii, J. R.; Parker, E. N. Bibcode: 1969ApJ...155..799J Altcode: We point out that the observed mean life for cosmic rays of ~ yrs is difficult to account for in conventional models of the galactic magnetic field. A stochastic model of the interstellar magnetic field is proposed, and is shown to provide a natural explanation of the cosmic-ray lifetimes. The random walk of magnetic lines of force, deduced from the observed turbulent motions of the gas and also from observa- tions of the polarization of starlight, leads to rapid motion of the cosmic-ray particles normal to the plane of the galactic disk Title: Energetic solar particles. Authors: Parker, E. N. Bibcode: 1969AIQSY...4...57P Altcode: No abstract at ADS Title: Solar wind interaction with the geomagnetic field. Authors: Parker, E. N. Bibcode: 1969RvGSP...7....3P Altcode: 1969RvGeo...7....3P No abstract at ADS Title: Summary of symposium Authors: Parker, E. N. Bibcode: 1969sfsr.conf..412P Altcode: No abstract at ADS Title: Physical model of hydrodynamic turbulence. Authors: Parker, E. N. Bibcode: 1969PhFl...12.1592P Altcode: A model for statistically isotropic homogeneous turbulence in an incompressible fluid is constructed, representing the turbulence as a superposition of individual vortex sheets. Each vortex sheet moves in the velocity field of the other sheets which have larger scale. Each sheet is stretched out, and intensified, until obliterated by viscosity at high wavenumber. The rate of stretching is related to the symmetric part of the strain tensor ∂νi/∂κj, which is postulated to be statistically independent of the antisymmetric part. Representing the turbulence by the usual energy spectrum function F(k) leads to a set of integrodifferential equations. Solution of the equations gives a spectrum which is in close agreement with experimental spectra of turbulence over both the inertial and viscous subranges, suggesting that the model may be of some real physical interest. The model is sufficiently explicit so as to give information on the correlation between different Fourier components of the turbulence. The calculations give the probability of finding a particular value of the vorticity or velocity at a given position and time in the turbulent field. Title: Dynamical properties and effects of cosmic rays in the galaxy Authors: Parker, E. N. Bibcode: 1969pia..conf..237P Altcode: No abstract at ADS Title: The Dynamical Behaviour of the Gaseous Disk of the Galaxy Authors: Parker, E. N. Bibcode: 1969crsr.conf..202P Altcode: No abstract at ADS Title: The Dynamical State of the Interstellar Gas and Fields. VII. Disruptive Forces Authors: Parker, E. N. Bibcode: 1968ApJ...154..875P Altcode: The important role played by disruptive forces in regulating the conversion of interstellar gas into stars is pointed out in the context of the present dynamical theory of the interstellar gas and fields Title: The Dynamical State of the Interstellar Gas and Field.VI. Instability and Enhanced Diffusion in a Twisted Field Authors: Lerche, I.; Parker, E. N. Bibcode: 1968ApJ...154..515L Altcode: The general instability of a magnetic field confined by the weight of thermal gas (through which the field threads) is investigated for a twisted field (v X B II B). The purpose is to see whether the asso- ciated enhanced ambipolar diffusion is seriously affected by the twist in the field. It was pointed out earlier that the enhanced diffusion (computed for an untwisted field) may contribute (a) to the escape of the interstellar magnetic field from the gas forming a star and (b) to the evolution of the gaseous disk of the Galaxy The calculations given in the present paper suggest that the twist in the field should in- crease the instability and the associated large wavenumbers, thereby increasing the enhanced ambipolar diffusion. We conclude that our earlier estimates of the enhanced ambipolar diffusion rate in the Galaxy may be on the conservative side Title: The Dynamical State of the Interstellar Gas and Field.IV. Evolution of the Disk of Interstellar Gas Authors: Parker, E. N. Bibcode: 1968ApJ...154...49P Altcode: It is shown that ambipolar diffusion, enhanced by the dynamical instability of the interstellar gas-field system, may permit the escape of a significant portion of the interstellar magnetic field from the disk of the Galaxy during the 1O'°-year life of the Galaxy. The result is a decrease in the scale height or thickness of the gaseous disk Title: The Dynamical State of the Interstellar Gas and Field. V. Reduced Dynamical Equations Authors: Parker, E. N. Bibcode: 1968ApJ...154...57P Altcode: The dynamical equations for a gas suspended on a horizontal magnetic field are simplified and re- duced by supposing that the Alfvén speed is large compared with the thermal velocity and that the scales are small compared with the scale height. The simplification renders the equations tractable in more complicated physical situations than the complete set of hydromagnetic equations used in some of the earlier investigations. A number of results for hydrostatic equilibrium, and for small perturbations of an equilibrium, are worked out to illustrate the properties of the approximate system of equations. Com- parison with the special cases treated from the complete equations indicates that most of the essential features of the dynamics appear to be retained by the simplified equations. The simplified equations are to be applied to more complicated cases in future papers Title: Random Walk of Magnetic Lines of Force in Astrophysics Authors: Jokipii, J. R.; Parker, E. N. Bibcode: 1968PhRvL..21...44J Altcode: We point out the importance of the random fluctuations in astrophysical magnetic fields, which lead among other things to rapid diffusion of energetic particles across the average magnetic field. Application to the interplanetary magnetic field leads to a theory in which the field-line random walk, measured by the observed power spectrum of field fluctuations, is in agreement with that deduced from the observed turbulent motions in the solar photosphere. The two determinations agree well with the recently observed spread in longitude of low-energy particles released at the sun. Title: Dynamical Properties of Cosmic Rays Authors: Parker, E. N. Bibcode: 1968nim..book..707P Altcode: 1968S&SS....7..707P No abstract at ADS Title: Dynamical Properties of the Magnetosphere Authors: Parker, E. N. Bibcode: 1968ASSL...10....3P Altcode: 1968phma.conf....3P No abstract at ADS Title: Considerations of Solar Wind-Magnetosphere Interactions Authors: Parker, Eugene N. Bibcode: 1968epf..conf..357P Altcode: No abstract at ADS Title: The role of stochastic fields in admitting low-energy galactic cosmic rays to the solar system Authors: Parker, E. N. Bibcode: 1968JGR....73.6842P Altcode: No abstract at ADS Title: Non-Equilibrium and Enhanced Mixing at a Plasma-Field Interface Authors: Lerche, I.; Parker, E. N. Bibcode: 1967ApJ...150..731L Altcode: No abstract at ADS Title: Cosmic ray diffusion, energy loss, and the diurnal variation Authors: Parker, E. N. Bibcode: 1967P&SS...15.1723P Altcode: The purpose of this paper is to consider a number of points pertaining to the origin of the observed mean diurnal variation of the cosmic ray intensity, which were not treated in the earlier papers on the subject. Following a brief review of the basic nature of the diurnal variation, the necessary diffusion across the lines of force is investigated. It is found that the values κ ≅ 10 -2 deduced from the observed fluctuations inside the orbit of Earth give about the right amount of diffusion to account for the fact that the amplitude of the diurnal variation is approximately half the theoretical upper limit, which would apply if κ were much larger. The calculations show that the geometry of the spiral form of the field beyond the orbit of Earth plays an essential role in providing sufficient diffusion across the lines of force. The calculations also show that variation in outer radius R and in κ due to changing wind conditions may contribute to some of the observed changes in the amplitude of the diurnal variation. The diurnal variation is rederived for steady uniform wind conditions in order to include the effect of adiabatic deceleration. The effect is the addition of a small diurnal component with an amplitude proportional to the radial cosmic ray gradient in space. The effect is only a few per cent of the total diurnal variation above 1 GeV, and so may be neglected there. The effect is large at low energies, but is not subject to observation. The principal observable steady diurnal variation is, then, the rotation of the cosmic rays with the Sun. Appendix II gives a summary of the motion of a particle in an idealized smooth spiral interplanetary field, with a discussion of the energy loss from adiabatic expansion. Title: An Initial-Value Problem for Oscillations of the Interstellar Gas Authors: Lerche, I.; Parker, E. N. Bibcode: 1967ApJ...149..559L Altcode: For a simple model of the interstellar-gas-magnetic-field system, in which the disk population of stars provides most of the gravity, it is demonstrated that a dispersion relation approach to the problem of small perturbations of the equilibrium state leads to unstable modes which possess a constant energy density at an infinite distance from the disk. Since one normally treats perturbations in which the energy density vanishes at infinity, rather than merely being bounded, we investigate an initial-value problem in which the energy density does vanish at infinity. It is shown, with one simple case, that an unstable situation still develops but that the perturbed quantities grow linearly with time rather than exponentially, as a normal mode analysis would indicate. It is further shown that one can still characterize the time scale for instability by the free-fall time so that conclusions drawn elsewhere by Parker remain valid. Title: Energy changes of cosmic rays in the solar system Authors: Jokipii, J. R.; Parker, E. N. Bibcode: 1967P&SS...15.1375J Altcode: The energy (in the fixed frame of reference) of a cosmic-ray particle with velocity w in the frame of the solar wind fluctuates between 1/2M(w + v) 2 and 1/2M(w - v) 2 as the particle random walks in the magnetic field, where v is the wind velocity. This energy change cannot be treated as a simple Markov process, together with the random walk and adiabatic deceleration, in a fixed frame of reference. To describe the particle motion by a Fokker-Planck differential equation, the energy variable must be the particle energy in a frame of reference moving with the wind. The appropriate transformations of both the solutions and boundary conditions are presented to order v/ w. The corrections due to this effect are ∼10% for 1 MeV particles and correspondingly less for higher energy particles. The energy balance between the solar wind and cosmic rays is examined and is shown to depend in a fundamental manner on these energy transformations. Although the solar wind does net work on the cosmic-ray gas, no particle gains more than 2 Mvw kinetic energy and the few particles which penetrate deeply into the solar system suffer a net energy loss because of adiabatic deceleration. Title: The Dynamical State of the Interstellar Gas and Field. II. Non-Linear Growth of Clouds and Forces in Three Dimensions Authors: Parker, E. N. Bibcode: 1967ApJ...149..517P Altcode: The growth of the two-dimensional instability of a gas in a gravitational field g confining a horizontal magnetic field B is followed into the non-linear regime to provide an illustration of the formation of discrete gas clouds from a more uniform medium. A shock forms as the gas falls together, dissipating the energy and making the process irreversible. The effective force field of an element of gas (suspended on the lines of force of a horizontal magnetic field) is calculated in three dimensions. The force field is made up of an attractive force of the same form as gravity but stronger by the factor g2/GB2, and a force which extends undiminished along the lines of force passing near the element of gas. The latter dominates the former at large distances and is attractive on the lines of force through, and above and below, the element of gas, and repulsive along the lines of force passing beside the element of gas. The over-all effect is a strong attraction, accompanied by vigorous streaming of gas both toward and away from an established cloud. Clouds are expected to accumulate gas in such a way as to increase their vertical dimension relative to the transverse dimension g X B. Title: The Dynamical State of the Interstellar Gas and Field. III. Turbulence and Enhanced Diffusion Authors: Parker, E. N. Bibcode: 1967ApJ...149..535P Altcode: The dynamical instability of the interstellar gas, caused by the galactic cosmic rays and magnetic field, is examined for the purpose of gaining a more detailed understanding of the phenomenon. It is shown that a tissue of field, formed by superposing alternate layers of field at right angles to each other, fails to produce stability. It is shown that the instability develops very short wavelengths in the direction perpendicular to the galactic gravitational field g and magnetic field B. The result is that the interstellar gas must be in a continual state of turbulence and fragmentation down to scales of 1 pc or less, terminating only when the clouds become so dense that self-gravitation becomes dominant The turbulence and fragmentation enhance ambipolar diffusion to such an extent that the field escapes from the gas rapidly compared to the usual ambipolar rates It is suggested that this may contribute to the escape of the magnetic fields from the interstellar gas which forms stars Title: Phenomena in Interplanetary Space. (Book Reviews: The Solar Wind. Proceedings of a conference held in Pasadena, California, in April 1964) Authors: Parker, Eugene N. Bibcode: 1967Sci...155..681P Altcode: 1967Sci...155..681M No abstract at ADS Title: Sun and Earth Authors: Parker, E. N. Bibcode: 1967easp.book...46P Altcode: No abstract at ADS Title: Disturbance of the Geomagnetic Field by the Solar Wind Authors: Parker, E. N. Bibcode: 1967pgp..conf.1154P Altcode: No abstract at ADS Title: The Dynamical State of the Interstellar Gas and Field Authors: Parker, E. N. Bibcode: 1966ApJ...145..811P Altcode: There is now enough observational information available to show that the interstellar magnetic field in the general neighborhood of the Sun is, on the average, parallel to the plane of the Galaxy, with an average strength somewhere between 10-6 and tO-' gauss. This paper points out certain dynamical requirements for the existence of such a field. The paper is based on the assumption that the intergalactic medium, whatever it may be, exerts pressures on the Galaxy that are small compared to 10-12 dyne/cm'. It can then be shown that the galactic, or interstellar, magnetic field must be to the Galaxy by the weight of the gas threaded by the field and distributed throughout the disk of the Galaxy. It is then shown that the interstellar gas-field system is subject to a universal Rayleigh-Taylor instability of such a nature that the interstellar gas tends to concentrate into pockets suspended in the field. The cause of the instability may he thought of as a hydromagnetic self-attraction in the interstellar gas, which may be ten times larger than the gravitational self-attraction of the gas. It is this hydromagnetic self-attraction which produces the observed tendency of the interstellar gas to be confined in discrete clouds. The calculations and arguments do not restrict the over-all topology or the strength of the galactic field, which apparently must still be determined from observation. Title: Non-Relativistic Equations of Bulk Motion of a Relativistic Gas Authors: Lerche, I.; Parker, E. N. Bibcode: 1966ApJ...145..106L Altcode: The linearized equations of bulk motion of a gas, in which the pressure cannot be neglected compared to the rest energy of the gas, are deduced by taking moments of the collisionless Boltzmann equation in the absence of external forces. The problem is of interest because of its application to the cosmic-ray gas in the Galaxy. Title: The Kinetic Properties of the Galactic Cosmic-Ray Gas Authors: Parker, E. N. Bibcode: 1966ApJ...144..916P Altcode: The elementary formulae for the pressure and the speed of sound in a statistically isotropic homogeneous cosmic-ray gas are worked out. Cosmic-ray observations near Earth give a cosmic-ray energy density of 1.29 X 10- erg/cm3, a pressure of 0.45 x 1O dyne/cm2, and a compressibility P/ N = 0.66>< 10-li erg/cm3. There is reason to believe that the interstellar values are not significantly higher than near Earth. Title: The effect of adiabatic deceleration on the cosmic ray spectrum in the solar system Authors: Parker, E. N. Bibcode: 1966P&SS...14..371P Altcode: Cosmic rays in the magnetic fields carried in the solar wind are continually expanded and decelerated, in addition to being convected out of the solar system. The effect of the deceleration on the cosmic ray spectrum is calculated for the case that the outward convection of cosmic rays is small and for the case that the cosmic ray spectrum is a simple power law and the diffusion coefficient is independent of energy. The calculations are carried out for both particle momentum and energy. It is shown that a power law spectrum is preserved by the deceleration. It is shown that the deceleration contributes a decrease at high energies of about one third of the total modulation. Where the spectrum flattens out at lower energies, the deceleration produces an increase which partially cancels the reduction by convection. Title: Dynamical Properties of Stellar Coronas and Stellar Winds. V. Stability and Wave Propagation Authors: Parker, E. N. Bibcode: 1966ApJ...143...32P Altcode: The stability of an expanding corona against radial compressional waves is considered. It is shown that the linearized equations of motion are hyperbolic and the expanding corona is stable to the same general degree as a static atmosphere. Examples of wave propagation are worked out to illustrate the variation of amplitude of the waves with radial distance from the Sun. Title: The Penetration of Galactic Cosmic Rays into the Solar System Authors: Parker, E. N. Bibcode: 1966sowi.conf..185P Altcode: No abstract at ADS Title: Particle Effects in the Geomagnetic Field Authors: Parker, E. N. Bibcode: 1966ASSL....5..302P Altcode: 1966rtem.conf..302P No abstract at ADS Title: Superthermal Hydromagnetic Waves. Authors: Parker, E. N. Bibcode: 1965ApJ...142.1086P Altcode: The linearized of motion of a thermal gas and some very hot suprathermal gas, such as interstellar cosmic rays, in a uniform magnetic field are wntten down for plane waves in the low-frequency limit. The dispersion relation shows that there are three modes altogether: The conventional slow and fast hydromagnetic waves in the thermal gas are unaffected, except that there is a "hole" in the fast mode in the direction perpendicular to the magnetic field. The third mode is the suprathermal mode, representing waves in the suprathermal gas with essentially the velocity of sound in the suprathermal gas alone. The suprathermal mode fills the "hole" in the fast mode and is obviously the first disturbance to reach distant points following a supernova explosion. Title: Dynamical Theory of the Solar Wind Authors: Parker, E. N. Bibcode: 1965SSRv....4..666P Altcode: This paper is a review of the basic theoretical dynamical properties of an atmosphere with an extended temperature strongly bound by gravity. The review begins with the historical developments leading up to the realization that the only dynamical equilibrium of an atmosphere with extended temperature is supersonic expansion. It is shown that sufficient conditions for supersonic expansion are T(r) declining asymptotically less rapidly than 1/r, or the density at the base of the corona being less than N b given by (40) if no energy is available except through thermal conductivity, or the temperature falling within the limits given by (18) if T ∝ N α-1 throughout the corona. Less extended temperatures lead to equilibria which are subsonic or static. The hypothetical case of a corona with no energy supply other than thermal conduction from its base is considered at some length because the equations may be solved by analytical methods and illustrate the transition from subsonic to supersonic equilibrium as the temperature becomes more extended. Comparison with the actual corona shows that the solar corona is actively heated for some distance into space by wave dissipation. The dynamical stability of the expanding atmosphere is demonstrated, and in a later section the radial propagation of acoustic and Alfvén waves through the atmosphere and wind is worked out. The calculations show that the magnetometer will probably detect waves more easily than the plasma instrument, but that both are needed to determine the mode and direction of the wave. An observer in the wind at the orbit of Earth can “listen” to disturbances generated in the corona near the sun and in turbulent regions in interplanetary space. The possibility that the solar corona is composed of small-scale filaments near the sun is considered. It is shown that such filamentary structure would not be seen at the orbit of Earth. It is pointed out that the expansion of a non-filamentary corona seems to lead to too high a calculated wind density at the orbit of Earth to agree with the present observations, unless T(r) is constant or increases with r. A filamentary corona, on the other hand, would give the observed wind density for declining T(r). It is shown that viscosity plays no important role in the expansion of an atmosphere either with or without a weak magnetic field. The termination of the solar wind, presumably between 10 103 AU, is discussed briefly. The interesting development here is the interplanetary L αrecently observed, which may come from the interstellar neutral hydrogen drifting into the outer regions of the solar wind. Theory is at the present time concerned with the general dynamical principles which pertain to the expansion equilibrium of an atmosphere. It is to be expected that the rapid progress of direct observations of the corona and wind will soon permit more detailed studies to be carried out. It is important that the distinction between detailed empirical models and models intended to illustrate general principles be kept clearly in mind at all times. Title: Cosmic Rays and Their Formation of a Galactic Halo. Authors: Parker, E. N. Bibcode: 1965ApJ...142..584P Altcode: It is demonstrated that a magnetic gas cloud confined by gravity has no equilibrium configuration if cosmic rays are generated within it. By application of the theorem to the Galaxy, it is shown that cosmic rays lead to inflation of the galactic magnetic fields, producing a halo of cosmic rays and field around the Galaxy. Present observational estimates of cosmic-ray life, magnetic-field strength, etc.,indicate an outward inflation rate of the order of 102 km/sec, although this number may be revised with improved observations. This cosmic-ray halo extends far out from the disk and nucleus of the Galaxy, presumably limited by instabilities which eventually free the cosmic rays and fields at a great distance. The field inflation acts as a pressure regulator on the cosmic rays generated in the galactic disk and nucleus, so that the life of a cosmic-ray particle in the disk of the is determined mainly by the rate of generation of cosmic rays. Present estimates of the cosmic-ray life are based on the rather uncertain value of the density of interstellar gas. The gas is intimately associated both with the dynamics of the galactic fields and the calculated rate of cosmic-ray production. Title: Dynamical Properties of Stellar Coronas and Stellar Winds, IV. The Separate Existence of Subsonic and Supersonic Solutions. Authors: Parker, E. N. Bibcode: 1965ApJ...141.1463P Altcode: The dynamical equations are considered for a stationary stellar corona whose energy is supplied only by thermal conduction from its base and which is surrounded by a cold vaccuum. The density and temperature at the base of the corona are denoted by N0 and T0, respectively. It is shown that subsonic and supersonic expansion of such a minimum stellar corona are separated by a density N (To): If N0 < NB(To), the expansion is supersonic; if N0> NB(To), the expansion is subsonic. Observations suggest that T0 1 X 100 K for the quiet solar corona, so that NB(To) 3 X 1010/ cm3. The observed densities are 108-109/cm3, requiring supersonic expansion. Detailed comparison of this theoretical corona of minimum heating with the observed solar temperatures, densities, and expansion velocity suggests that the solar corona is, in fact, heated in depth. Title: General dynamical effects of cosmic rays in the Galaxy. Authors: Parker, E. N. Bibcode: 1965ICRC....1..126P Altcode: 1965ICRC....9..126P No abstract at ADS Title: The passage of energetic charged particles through interplanetary space Authors: Parker, E. N. Bibcode: 1965P&SS...13....9P Altcode: The passage of cosmic ray particles and energetic solar particles through interplanetary space is illustrated with a number of idealized examples. The formal examples are worked out from the condition that energetic particles in interplanetary space random walk in the irregularities in the large-scale interplanetary magnetic field. The irregularities move with approximately the velocity of the solar wind. The classical probability distribution is describable by a Fokker-Planck equation. A general expression for the particle diffusion coefficient kij is worked out, including both scattering in magnetic irregularities and systematic pressure drifts. Magnetometer data from Explorer XVIII is presented to show the close average adherence of the quiet-day interplanetary magnetic field to the theoretical spiral angle, and to show the tendency for particles to move more freely along the field than across, k > k. The observed fields show that the diffusion coefficient is of the order of 10 21-10 22 cm 2/sec, as had been estimated from earlier cosmic ray studies. A middle value of 3 × 10 21 cm 2/sec suggests a cosmic ray density gradient of about 10 per cent per a.u. across the orbit of Earth. Direct observations of the interplanetary magnetic field afford the possibility for quantitative estimate of Kij as a function of particle energy. The first example to be considered is isotropic diffusion in a spherical region r < R with uniform radial wind velocity v for the purpose of illustrating the general nature and duration of the passage of a cosmic ray particle through the solar system. It is shown that the cosmic ray density reduction is of the order of exp (- vR/ k), and, hence, that during the years of solar activity vR/ k is not less than about 1 for protons of one BeV or so. It follows from this that the galactic cosmic ray particles will generally have spent several days in the solar system by the time they are observed. During this time they are in the expanding magnetic fields carried in the solar wind and are adiabatically decelerated, losing 15 per cent or more of their energy by the time they are observed. The energy distribution is shown for particles starting all with the same energy T0 from interstellar space. The incoming probability wave of a single particle is computed as a function of time, showing how the particle is swept back by the wind. The converse problem of energetic solar particles is illustrated. The solar particles may typically lose half their initial energy before escaping into interstellar space. The outward motion of the wind displaces their probability distribution outward so that ultimately the maximum solar particle intensity may lie beyond the orbit of Earth. The outward motion of the wind steepens the decline of the solar particle intensity. The steady-state cosmic ray intensity is calculated throughout the spherical region r < R supposing a uniform cosmic ray density N0 to obtain in interstellar space. The calculation is carried out for isotropic Kij, which would obtain if the magnetic irregularities were of large amplitude and of a scale not exceeding the radius of gyration of the cosmic ray particles, and for anisotropic kij with k ≫ k, which obtains when the field is relatively smooth. (The observations at sunspot minimum suggest k ≫ k at the orbit of Earth.) The particles diffuse only along the spiral lines of force when k ≫ k, so their path in and out of the solar system is much longer than when Kij is isotropic. The result is a much greater reduction of the cosmic ray intensity for a given vR/| Kij|. There is no direct observational information on Kij beyond the orbit of Earth, where the intensity reduction takes place. Indirect information is available, however. There is the fact that the intensity of energetic solar particles at Earth often decays as t- g with g = 1·5-2·0. It is shown that in order for this to follow, it is necessary that | Kij| ∞ rs with s = 0·0-0·5 if kij is isotropic, and s = 2·0-2·5 if k ≫ k. That is to say, if Kij should continue to be as anisotropic beyond Earth as it is observed to be near Earth, then the diffusion must increase rapidly with distance from the Sun. These qualitative features should be easily detectable with particle, field, and plasma observations beyond the orbit of Earth. Title: On the Existence of Slow Solutions in Coronal Hydrodynamics. Authors: Parker, E. N. Bibcode: 1965ApJ...141..322P Altcode: No abstract at ADS Title: Some remarks on the influence of the granulation on the magnetic field Authors: Parker, E. N. Bibcode: 1965IAUS...22..232P Altcode: No abstract at ADS Title: A brief outline of the development of cosmic ray modulation theory Authors: Parker, E. N. Bibcode: 1965ICRC....1...26P Altcode: 1965ICRC....9...26P No abstract at ADS Title: Coronal Expansion and Solar Corpuscular Radiation Authors: Parker, E. N. Bibcode: 1965ASSL....3...99P Altcode: 1965pss..conf...99P No abstract at ADS Title: A Mechanism for Magnetic Enhancement of Sound-Wave Generation and the Dynamical Origin of Spicules. Authors: Parker, E. N. Bibcode: 1964ApJ...140.1170P Altcode: It is pointed out that a vertical magnetic field through an atmosphere with a small scale height greatly tahances the generation of sound (fast-mode) waves in the fluid motions in the atmosphere. The fluid motions become a monopole, rather than the usual quadrupole, source of radiation. The sound waves ropagate principally in the upward direction along the field. It is suggested that this mechanism, apart from its other applications, operates in the plage areas on the Sun and is responsible for the spicules. Title: Review of Publications- Interplanetary Dynamical Processes Authors: Parker, E. N. Bibcode: 1964JRASC..58..235P Altcode: No abstract at ADS Title: Discussion of Paper by E. J. Stegelmann and C. H. von Kenschitzki `On the Interpretation of the Sudden Commencement of Geomagnetic Storms' Authors: Parker, E. N.; Dessler, A. J. Bibcode: 1964JGR....69.3745P Altcode: It was pointed out some years ago [Dessler et al. 1960] that a major part of the rise time of a sudden commencement can be accounted for as the period of time in which the enhanced solar wind sweeps over the outer boundary of the geomagnetic field, plus the difference in propagation time from different points on the boundary. The dimensions of the outer boundary of the geomagnetic field are of the order of 105 km, so that an enhanced wind of 103 km/sec characteristically takes about 102 seconds to engulf the field and enhance the compression of the field. Typical propagation times within the field differ by 102 seconds. The basic idea was simply that the compression of the geomagnetic field at the surface of the earth results from the algebraic sum of all the compressive forces exerted by the wind on the outer boundary of the field [Parker, 1958]. Any changes in the compressive forces on the outer boundary are communicated inward at about the Alfvén velocity [Francis et al., 1959]. Enhanced compression of the boundary starts somewhere on the solar side, at which time a slight increase in compression begins to propagate through the geomagnetic field as a hydromagnetic wave. With the passage of time more and more of the boundary is compressed as the enhanced wind sweeps by in space. The rising compression communicates throughout the field with the Alfvén speed, and levels off only after the enhanced wind fully encloses the geomagnetic field. Title: Theory of streaming of cosmic rays and the diurnal variation Authors: Parker, E. N. Bibcode: 1964P&SS...12..735P Altcode: The motion of charged particles in magnetic fields is reviewed for the purpose of understanding the observed net streaming of cosmic rays through interplanetary space. It is shown that the large-scale fields (which often reverse) give no steady streaming by themselves. Small-scale irregularities in the large-scale fields can give steady radial streaming which in the vicinity of Earth is some small fraction of the solar wind velocity. A large-scale field at the orbit of Earth with sufficient magnetic irregularity beyond gives an azimuthal streaming with the velocity of rigid rotation with the Sun. It is suggested that this rigid rotation is the origin of the observed diurnal variation. Title: Formation of Massive Quasi-Stellar Objects. Authors: Miller, R. H.; Parker, E. N. Bibcode: 1964ApJ...140...50M Altcode: Enhancement of evaporation from a star cluster through the operation of co-operative phenomena is suggested as a possible mechanism for the formation of compact massive objects from star clusters in times of the order of 1016 years. Title: Coronal expansion and solar corpuscular radiation Authors: Parker, E. N. Bibcode: 1964P&SS...12..451P Altcode: No abstract at ADS Title: The Scattering of Charged Particles by Magnetic Irregularities Authors: Parker, E. N. Bibcode: 1964JGR....69.1755P Altcode: The equations of motion of a charged particle are integrated through an irregularity in a large-scale magnetic field. The scattering of the particle is shown to diminish as the cyclotron radius of the particle becomes either large or small compared to the scale of the irregularity and to have a maximum when the radius is comparable to the scale. When the cyclotron radius is large, the order of magnitude of the scattering depends on the number of sequential reverse bends in the lines of force through the magnetic irregularity. It is important for the understanding of modulation of the cosmic-ray intensity by the solar wind to determine the degree of correlation between adjacent bends in the irregularities in the interplanetary magnetic field. Title: The Perturbation of Interplanetary Dust Grains by the Solar Wind. Authors: Parker, E. N. Bibcode: 1964ApJ...139..951P Altcode: It is expected that photoelectric emission from the interplanetary dust grains leads to a positive charge the order of 10 volts on each grain. The Lorentz forces exerted on this charge by the magnetic fields . ied in the solar wind produce large perturbations in the Kepler orbits of the grains. On the assumpn that the sign of the interplanetary magnetic field reverses every few days, it is shown that the orbital lination of particles with radii equal to or smaller than about 1 X 10- cm at the orbit of Earth is atly increased by the Lorentz forces The importance of the Lorentz perturbation increases with the tance from the Sun. Title: Dynamical Properties of Stellar Coronas and Stellar Winds. III. The Dynamics of Coronal Streamers. Authors: Parker, E. N. Bibcode: 1964ApJ...139..690P Altcode: Observations suggest that the solar corona may perhaps consist of thin radial filaments and streamers, rather than bring an amoiphous atmosphere. The filaments and streamers presumably are confined by the magnetic field, along whose lines 9f force they lie. To investigate the consequences of a filamentary corona for the solar wind, the dynamics of an idealized cona composed of gaseous streamers, with vacuum between the streamers, is worked out neglecting solar rotation, etc. The pnndpal conclusions are that the streamers occupy most of space at large radial distance from the Sun, no matter how small a fraction they may occupy at the Sun; the velocity of the solar wind is not greatly affected by filamentary structure for a given coronal temperature distribution; the mean-wind density is not affected by more than a factor of 2. Mtogether, then, except for the presence of some thin interstreamer regions, there is no great effect of a filamentary structure on the mean values of the solar-wind velocity and density at large distance from the Sun. The possibility of instability of coronal streamers is looked into, and it is shown that, if the corona is composed principally of streamers, the Helmholtz instability may be expected to disorder and mix up the streamer and interstreamer regions beyond some distance 0 (1 a.u.) from the Sun, which might perhaps be the origin of some of the disorder observed by Mariner. More quantitative observational information of the solar corona and/or of the structure of the solar wind close to the Sun will have to be available before quantitative statements can be made concerning the role of streamers in the solar wind. Title: Dynamical Properties of Stellar Coronas and Stellar Winds. I. Integration of the Momentum Equation. Authors: Parker, E. N. Bibcode: 1964ApJ...139...72P Altcode: The hydrodvnamic momentum and mass flow equations are integrated for a stellar corona with spherical symmetry about the center of the star. The coronal temperature is taken to be a known function T(r) of radial distance. The general properties of the equations are discussed, and it is shown that if the corona is tightly bound by the solar gravitational field, so that the thermal elodty is small compared to the gravitational escape velocity, and if the coronal temperature declines outward more slowly than 1/r, then the corona is quasi-static at its base and expands to supersonic velocity in space. No alternative is available. The stellar mass loss resulting from the expansion is determined by the coronal temperature between the base of the corona and the point at which the flow becomes supersonic. The amount by which the velocity of the resulting stellar wind exceeds the thermal velocity in the corona depends principally upon the temperature beyond the point where the flow becomes supersonic. Title: Dynamical Properties of Stellar Coronas and Stellar Winds. II. Integration of the Heat-Flow Equation. Authors: Parker, E. N. Bibcode: 1964ApJ...139...93P Altcode: The temperature T(r) in a stellar corona is computed under the circumstances that energy is supplied outward from the base of the corona only by thermal conduction. The heat-flow equation is solved analytically under a variety of circumstances. It is shown that the energy flow to infinity is non-vanishing for finite coronal density and thermal conductivity. The temperature declines less rapidly than 1/r, and a supersonic stellar wind is the only available solution of the equations compatible with negligible pressure at r = A variety of asymptotic cases are worked out to illustrate some of the temperature proffles T(r) to be expected under various circumstances. For instance, in a corona of very low density the energy consumed by expansion of the corona can be neglected and T(r) , as in Chapman's original static coronal model. The result is a supersonic stellar wind with a velocity v( ) of the same order as the gravitational escape velocity 21!2w. In a corona with medium density and sufficiently low temperature that v('0) is small compared to w, a near region, in which T(r) extends for some distance outward from the star before the far region, T(r) , takes over. The result is a supersonic stellar wind velocity v( ) of the same order as the characteristic thermal velocity C0 at the base of the corona. In a corona which is exceedingly dense, an intermediate region in which T(r) appears between the near and the far regions, which has the result of extending to large distance the point at which the coronal expansion becomes supersonic. In a corona which is exceedingly hot (cc w) the expansion becomes so violent that thermal conduction becomes negligible and the behavior of the corona is approximately adiabatic. It is shown that any effect which tends to reduce the thermal conductivity of the coronal gases at large distance from the star has the effect of enhancing the velocity of the stellar wind. Comparison with Chamberlain's earlier discussion of the solution of the momentum and heat-flow equations in his "solar-breeze" model shows that he made two self-consistent errors in his assumption that the energy flux in the solar wind is identically zero and that the gas motion is adiabatic at large radial distances from the sun. It is shown that neither assumption is correct in a corona of finite density. It is shown, however, that the analytical form T(r) 1/r suggested by Chamberlain is obtained in the limit as the density of the corona is made large without limit, in which case all motion in the corona approaches zero. Application of the solutions of the heat-flow equation to the sun-assuming that the solar corona is heated solely by thermal conduction-show that at least under present conditions the solar corona and wind lie in the middle ground between high and low density and temperature. Assuming that they have coronas heated solely by conduction it is suggested that some of the giant stars with the low gravitational escape velocities, may fall into the high-density case, and certain dwarfs into the low-density case. Some of the very active stars may fall into the high-temperature quasi-adiabatic case. Title: Coronal Expansion and Solar Corpuscular Radiation Authors: Parker, E. N. Bibcode: 1964rege....1...99P Altcode: No abstract at ADS Title: Comments on Understanding the Solar Flare Authors: Parker, E. N. Bibcode: 1964NASSP..50..417P Altcode: 1964psf..conf..417P No abstract at ADS Title: Kinematical Hydromagnetic Theory and its Application to the Low Solar Photosphere. Authors: Parker, E. N. Bibcode: 1963ApJ...138..552P Altcode: The magnetic field B is computed from the hydromagnetic equations for a variety of given velocity fields';. The velocity fields are classified as turbulent if their time correlation extends no more than their scale a divided by their characteristic velocity v. The velocity fields are classified as persistent if their time correlation extends beyond a/v but is short compared with the magnetic diffusion time a2/X (X = c2/4ir , and as stationary if their time correlation extends beyond a2/X. It is shown that turbulent fluid motions in the solar photosphere generate r.m.s. fields which are a few times the large-scale field strength B0 in the photosphere. Where B0> 20 gauss, this leads to equipartition of energy between the turbulent magnetic and velocity fields. It is & njectured that, since plages occupy the areas on the solar surface where B0> 20 gauss, there may be some connection between equipartition and plage formation. It is shown that motions tend to draw the field into concentrated sheets and filaments. The observed supergranulation in the solar atmosphere tends to concentrate vertical magnetic fields around the edges of the cells, where the field density may become 102 times larger than in the interior of the cell. It is shown that stationary motions tend to exclude the magnetic field from the region of fluid motion. A number of examples are given to show the distortion of the field by the forces exerted by the fluid diffusing through it. It is to be hoped that observations will yield simultaneous velocity and magnetic-field maps so that quantitative comparison can be made with the expected theoretical results. Title: A Kinematical Theory of Turbulent Hydromagnetic Fields. Authors: Parker, E. N. Bibcode: 1963ApJ...138..226P Altcode: A kinematical theory is developed for the r.m.s. magnetic fields produced by the interaction of turbulent eddies, of scale a and velocity v, with a large-scale weak magnetic field B0. The principal interest lies in the small-scale magnetic field generated by the observed photospheric granules in the observed large-scale photospheric magnetic fields. The theory considers how a rope of magnetic flux is both lengthened and widened by the velocity gradients in statistically stationary, isotropic, homogeneous turbulence in which the velocity fields are given. Both the amplification and diffusion of the magnetic field are then computed from the proportions of the rope of flux, employing the usual statistical assumption that moments of order 2n can be expressed in terms of the product of n factors of second moments. The conclusion is that a weak field B0 can be amplified by a factor of the order of R1/4/ln R, where R is the magnetic Reynolds number. in the solar photospheric granules this amounts to amplification by a factor less than 10, so that the small-scale r m 5. fields resulting in quiet regions where B0 __ 1 gauss are far below the value for equipartition of energy with the velocity field. Title: The Solar-Flare Phenomenon and the Theory of Reconnection and Annihiliation of Magnetic Fields. Authors: Parker, E. N. Bibcode: 1963ApJS....8..177P Altcode: The paper presents a study of the observations and theory which are relevant to the presently popular belief that the solar-flare phenomenon is a direct consequence of the annihilation of magnetic fields on the sun. There is very little in the observations to support such views. A systematic study of the known theoretical mechanisms for the diffusion, reconnection, and annihilation of magnetic fields is presented. The mechanisms discussed are Joule dissipation, ambipolar diffusion, and various forms of Sweet's mechanism. It is shown that Sweet's mechanism is much more effective in a highly compressible medium if the merging magnetic fields are exacily antiparallel. None of the known mechanisms are sufficiently rapid to account for the solar flare from the annihilation of magnetic fields. Errors and omissions in earlier discussions of the problem are cited. Since no possible energy source other than magnetic fields has yet been developed, the question of field annihilation remains both open and pressing. The possibilities of runaway electrons and hydrodynamic instability, as means for hastening magneticfield annihilation, are considered. It is shown that there is no reason to expect runaway electrons and no effective instability unless the fields are exactly antiparallel. The observational and theoretical difficulties with the hypothesis of magnetic-field annihilation suggest that other alternatives for the flare must be explored. Title: Discussion of Paper by L. M. Noble and F. L. Scarf, `Hydrodynamic Models of the Solar Corona' Authors: Parker, E. N. Bibcode: 1963JGR....68.1769P Altcode: In a recent paper entitled `Hydrodynamic models of the solar corona' Noble and Scarf [1962] discuss the many theoretical models of the solar corona that have been worked out over the past few years. Some of the calculations they present are of interest, but unfortunately the value of the calculations is obscured by the extraordinary physical interpretations the authors associate with them. For instance, Noble and Scarf remark that `the models with conductive [heat] flow and no inner heat source lead to density distributions in fair agreement with zodiacal light observations, but no solar wind is obtained'. They seem to be unaware that Chamberlain [1961], whose paper on conductive flow they quote, had arbitrarily to inhibit the thermal conductivity by a factor of 8 to obtain agreement with the zodiacal light. Uninhibited thermal conduction in a 2×106 deg K corona supplies energy in the amount that seems to be required for the observed solar wind [Bridge et al., 1962]. Title: Theory of Solar Wind Authors: Parker, E. N. Bibcode: 1963ICRC....1..175P Altcode: 1963ICRC....8a.175P No abstract at ADS Title: Plasma Dynamics in Astrophysics and Geophysics (Notes by M. Turoff and A. Skalafuris) Authors: Parker, E. N. Bibcode: 1963ambp.book....1P Altcode: No abstract at ADS Title: Comments on Coronal Heating. Authors: Parker, E. N. Bibcode: 1963IAUS...16...11P Altcode: No abstract at ADS Title: Interplanetary dynamical processes. Authors: Parker, Eugene Newman Bibcode: 1963idp..book.....P Altcode: 1963QB505.P3....... No abstract at ADS Title: Kinetic properties of interplanetary matter Authors: Parker, E. N. Bibcode: 1962P&SS....9..461P Altcode: The paper is a review of present estimates of the kinetic and transport properties of the interplanetary medium. It is pointed out that the effective mean free paths of interplanetary ions and electrons are effectively small compared to the scale of the system either because of Coulomb collisions or because of dynamical instability of the gas. Numerical expressions are given for the mean free path for Coulomb collisions, the electrical conductivity, the thermal conductivity, the viscosity, electromagnetic emission rates, recombination and ionization times and the charge exchange cross-sections. The magnetic Reynolds number of the solar wind proves to be large, the Reynolds number is not very large and the Prandtl number is small. All stationary atoms and ions are swept out of the solar system by the solar wind. It is pointed out that the quiet day cosmic ray density in interplanetary space increases the speed of sound beyond the orbit of Earth, reaching 10 2 km/sec at 50 a.u. if the solar wind should extend that far. Energetic particles from the sun have an effect which may be much larger. The abundance of heavy ions in the solar wind may be significantly below the solar abundance because of diffusion in the solar corona. Title: Interplanetary Dynamical Processes; The Solar Wind and Interplanetary Fields Authors: Parker, E. N. Bibcode: 1962pss..conf...23P Altcode: No abstract at ADS Title: Dynamics of the Geomagnetic Storm Authors: Parker, E. N. Bibcode: 1962SSRv....1...62P Altcode: This paper is intended as a critical review of current ideas concerning the mechanisms responsible for the geomagnetic storm. The dynamical theory of the geomagnetic storm phenomenon is formulated as a problem in elasticity. The observed variations in the field are the strains produced by particle stresses exerted by gases in interplanetary space, by gases enmeshed in the field, and by the gases in the ionosphere. The stresses exerted by interplanetary gases are principally inward, resulting in the initial phase increase of the horizontal component. The stresses exerted by gases enmeshed in the field are principally outward, resulting in the main phase decrease of the horizontal component. The transient sudden commencement is a hydromagnetic wave phenomenon. The main phase is most simply explained by the shock heating of the ions to kev energies at 3 5 R E during the active phase of the storm. The recovery follows then from charge exchange with the ambient neutral hydrogen. The predicted more rapid recovery at sunspot minimum has been verified observationally. Title: A Mechanism to Establish the Magnetic Storm Ring Current Authors: Dessler, A. J.; Hanson, W. B.; Parker, E. N. Bibcode: 1962JPSJS..17A.178D Altcode: 1962PSJaP..17A.178D; 1962ICRC....7A.178D; 1962JPSJ...17A.178D No abstract at ADS Title: Interplanetary Dynamics and Cosmic Ray Modulation Authors: Parker, E. N. Bibcode: 1962JPSJS..17B.563P Altcode: 1962PSJaP..17B.563P; 1962JPSJ...17B.563P; 1962ICRC....7B.563P No abstract at ADS Title: Theory of Magnetic Storms Authors: Parker, E. N. Bibcode: 1962JPSJS..17A.199P Altcode: 1962ICRC....7A.199P; 1962JPSJ...17A.199P; 1962PSJaP..17A.199P No abstract at ADS Title: Formation of the Geomagnetic Storm Main-Phase Ring Current Authors: Dessler, A. J.; Hanson, W. B.; Parker, E. N. Bibcode: 1961JGR....66.3631D Altcode: It is suggested that hydromagnetic waves generated by the impact of solar plasma on the geomagnetic field may form shock waves in the magnetosphere, thus providing a mechanism for establishing the diamagnetic main-phase ring current. These shock waves should develop on the night side of the earth and heat the ambient protons (which constitute the normal protonosphere) to approximately the hydromagnetic-wave velocity (of the order of 500 km/sec). The transfer of hydromagnetic-wave energy to the protons stresses the geomagnetic field and produces the geomagnetic-storm main phase; i.e., the kilovolt-energy protons form a diamagnetic current. The bombardment of the upper atmosphere by energetic hydrogen atoms from the decaying ring current and the possible change in the decay time-constant of the ring current through the sunspot cycle are discussed. Title: Transresonant Electron Acceleration Authors: Parker, E. N. Bibcode: 1961JGR....66.2673P Altcode: Helliwell and Bell have suggested synchronous acceleration of electrons by electromagnetic waves in the whistler range in the geomagnetic field. The acceleration of trapped electrons by electromagnetic waves is here generalized to include nonsynchronous or transresonant acceleration. It is shown that whistlers will scatter the electron velocity, by an amount inversely proportional to the square root of the time rate of change of the whistler frequency, during the time that the whistler frequency is passing over the electron gyrofrequency. Only electrons with initial energy above about 102 ev can see the Doppler-shifted whistler frequency at the gyrofrequency and be affected by this transresonant acceleration. Thermal electrons experience no effect. Current observation of whistlers in the outer geomagnetic field is too sketchy to allow a determination of transresonant acceleration rates, so that the relative importance, as compared, for example, with the strong-whistler synchronous acceleration of Helliwell and Bell, cannot be assessed. The importance of whistler acceleration can be established when the whistler frequency spectrum and recurrence rate are known throughout the geomagnetic field. Title: The Distribution of Trapped Particles in a Changing Magnetic Field Authors: Parker, E. N. Bibcode: 1961JGR....66.2641P Altcode: The redistribution of charged particles in the mirror field B(s, t) = B0T(t){1 + [s/a(t)]v (t)}is worked out for slow changes in T(t), a(t), and v(t). It is found that increasing T(t) gives a relatively greater particle density increase in the center of the field than deep in the mirrors s≫a(t). The mirror distance retracts like 1/T1/(v+2). Decreasing a(t) has the opposite effect. Field variations constrained to preserve T(t) a2(t) and v(t) leave the form of the particle distribution unchanged, increasing the density everywhere by the same factor. Title: The Stellar-Wind Regions. Authors: Parker, E. N. Bibcode: 1961ApJ...134...20P Altcode: From the observations of the solar wind and of the M giant a Herculis the gross dynamical features of the stellar-wind regions associated with class G main-sequence and M giant stars are given for various interstellar environments. The supersonic wind from a class G star undergoes a shock transition to subsonic flow at a radial distance of 1O-1O a u. This subsonic flow will be subject to turbulence and other instabilities in many cases. The wind from an M giant may extend many parsecs if the M-giant phase of evolution lasts as long as 1O years; the resultant interstellar contamination and heating are important. A rough calculation of the cavity formed by a stellar wind in a large-scale interstellar magnetic field shows that the cavity shape and dimensions for stationary flow depend on the pressure at infinity. As the pressure increases, the cavity changes from a circular cylinder of infinite radius, through an increasingly bulbous shape of finite radius, to a sphere of infinite radius with one finite cylindrical channel from each pole. Title: Sudden Expansion of the Corona Following a Large Solar Flare and the Attendant Magnetic Field and Cosmic-Ray Effects. Authors: Parker, E. N. Bibcode: 1961ApJ...133.1014P Altcode: We show from the hydrodynamic equations that the 4 X 106 K temperatures observed in the solar corona after a large solar flare can produce a hydrodynamic blast wave, moving out through interplanetary space with velocities of 1500 km/sec and densities from a few times 105/cm3 to 105/cm3 at the orbit of earth. We suggest that it is this hydrodynamic explosion of the enhanced corona that is the "accelerating mechanism" for the "plasma clouds" or "enhanced solar corpuscular emission" responsible for the geomagnetic storm, the cosmic-ray decrease, the low4atitude aurorae, etc, observed at earth a day or two following large solar flares on the visible hemisphere of the sun. We compute the interplanetary magnetic field in the blast wave, assuming an initial quiet-day solar wind of a few hundred km/sec ahead of the wave. The spiral field of the quiet-day wind is sheared by the blast wave, and its density, of the order of 2 X 10- gauss at the orbit of earth, may be increased to 5 X 10- gauss or more for a period of several hours. The effect of the outward-sweeping magnetic shear in the blast wave is to decrease the cosmic-ray intensity, occasionally perhaps by as much as 40 per cent, in the inner solar system behind the blast wave. The onset of the decrease has a characteristic time of several hours, and the relaxation many hours or days. The energy dependence of the decrease may go inversely with particle rigidity, or it may be flatter, depending on the details of the magnetic configuration in and around the blast wave. Thus the cosmic-ray decrease produced by the blast wave is identical with the Forbush-type cosmic-ray decrease observed in association with "enhanced solar corpuscular radiation." Thus, besides producing the observed 1500 km/sec ejection of matter from the sun responsible for the geomagnetic storm, the hydrodynamic expansion of the enhanced corona produces the observed Forbush decrease. We suggest, therefore, that the simple dynamical model of the enhanced corona developed in this paper is not unlike what actually occurs following a large solar flare. Title: Effect of Hydromagnetic Waves in a Dipole Field on the Longitudinal Invariant Authors: Parker, E. N. Bibcode: 1961JGR....66..693P Altcode: Hydromagnetic wave violation of the longitudinal invariant of a particle trapped in a mirror magnetic field is investigated quantitatively. It is shown that the passage of hydromagnetic waves across the region of mirroring leads to a diffusion of the individual-particle mirror points. If the relative wave amplitude ΔB/B is maintained throughout the mirror field, particles released in the field will soon diffuse out through the mirror and be lost. Application to thermonuclear devices is obvious. Confining our attention principally to the charged particles trapped in the geomagnetic field, it is shown that high-energy (105-ev) electrons in the outer Van Allen radiation zone are caused to diffuse along the lines of force with a characteristic time of 4 months by hydromagnetic waves of 1 cps and an amplitude of 10-4 gauss. Hydromagnetic diffusion appears to be more important than collisions in determining the electron lifetime and distribution in the outer Van Allen radiation zone. Different wave distributions along the lines of force can give radically different particle distributions. It is shown that, if the hydromagnetic disturbances extend throughout the geomagnetic field, then, rather than yielding particle acceleration, they result in a net loss of particle energy. But if we assume a region of hydromagnetic disturbance localized inside the geomagnetic field, limited particle acceleration may result. Title: The Interplanetary Gas and Magnetic Fields Authors: Parker, E. N. Bibcode: 1961sis..book..229P Altcode: No abstract at ADS Title: The Solar Wind Authors: Parker, E. N. Bibcode: 1961spas.book..157P Altcode: No abstract at ADS Title: The Hydrodynamic Theory of Solar Corpuscular Radiation and Stellar Winds. Authors: Parker, E. N. Bibcode: 1960ApJ...132..821P Altcode: We show from the conventional application of the static barometric law to the density of the solar corona, observed out to 20 RO at sunspot minimum, that the corona would be so hot at 20 RO that it could not be static but must expand. Thus one cannot correctly deduce the temperature in the outer corona from the density distribution by using the static barometric law. Allowing for the possibility of expansion, we find that the solution of the stationary, spherically symmetric, hydrodynamic equation for a uniform coronal temperature of 1.22 X 106 0K fits the observed coronal density predsely out to 14 R O,indicating an expansion velocity of the order of 300 km/sec at large radial distances. We conclude that at sunspot minimum the coronal temperature is 1.22 X 106 0K. We carry out an extensive investigation of the singular mathematical properties of the solutions of the stationary, spherically symmetric, non-linear hydrodynamic equation for the polytrope law P a N0. We show that there exist continuous solutions 4, [(4,o) , a, X; which go from low velocity in a strong gravitational field at the base of the corona out to infinity with the necessary boundary condition that p( ) = 0. These solutions yield supersonic velocities of expansion. In terms of the polytrope index, a, and the gravitational parameter, X GMOM/ROk T0, we show that these solutions exist for a strong gravitational field (X »1), provided only that a < T3 and X < 2a/(a - 1). Since observations of the solar corona show that these conditions are satisfied, we demonstrate formally the expansive nature of the solar corona. The mathematical theory allows us to work out the upper and lower bounds on the velocity of expansion of the solar corona-the solar wind-into interplanetary space. We find that at solar minimum the velocity of expansion may be only 300 km/sec, with densities as low as 20/cm2 at the orbit of earth. The quiet-day solar wind during the years of solar activity is evidently more than 500 km/sec. The solar wind is obviously what has heretofore been termed the ccsolar corpuscular radiation," to which quiet-day velocities and densities of 500 km/sec and 102/cm3 have been assigned on the basis of a number of independent observational analyses. We show that we expect at least all main-sequence stars later than class F to possess stellar winds, in analogy with the solar wind, so that the phenomenon is of widespread importance in the mass balance of the Galaxy, as well as in the early evolution of most stars. In the appendix we give an outline of the theory of hydromagnetic heating of the solar corona, pointing out that the ion thermal velocity in a stellar atmosphere, in which hydromagnetic heating is dominant, should be of the same order as the bydromagnetic wave velocity. This prediction is in agreement with the observed solar coronal temperatures. Title: Geomagnetic Fluctuations and the Form of the Outer Zone of the Van Allen Radiation Belt Authors: Parker, E. N. Bibcode: 1960JGR....65.3117P Altcode: It is demonstrated by formal calculation that the large-scale geomagnetic fluctuations observed at ground stations result in a rapid and somewhat remarkable kind of diffusion of the electrons in the outer zone of the Van Allen radiation belt. An initial thin ring of electrons will give an immediate finite particle flux at infinity, at the same time that the group of the particles remaining moves radially inward as a `wave'. We predict a decline of particle counting rate beyond about 4 earth radii of the order of 1/rβ, where β≅12 to 16, depending upon the kind of counter, in agreement with the many observations. Title: Geomagnetic Storm Sudden-Commencement Rise Times Authors: Dessler, A. J.; Francis, W. E.; Parker, E. N. Bibcode: 1960JGR....65.2715D Altcode: Adopting the view that the sudden commencement of a geomagnetic storm (SC) is the result of the impact on the geomagnetic field of an abrupt solar-plasma front, the form of the SC observed on the surface of the earth is investigated. A model is constructed to represent the shape of the geomagnetic field boundary as perturbed by the solar plasma. Calculations (carried out in the equatorial plane for simplicity) show that, regardless of how abrupt may be the impact of a solar-plasma front on the geomagnetic field, the variation in hydromagnetic transit times from different positions on the boundary, down to a point on the surface of the earth, yields SC rise times of several minutes at ground level. These times are in agreement with the observed SC rise times. Title: The Hydrodynamic Treatment of the Expanding Solar Corona. Authors: Parker, E. N. Bibcode: 1960ApJ...132..175P Altcode: It has been argued elsewhere that our earlier hydrodynamic treatment of the solar corona, which predicted a steady 500-km/sec expansion, is incorrect and that the appropriate treatment of the mass loss to the solar corona is with the classical evaporation theory of Jeans et at. In the first part of this paper we investigate the singular properties of the solutions of the hydrodynamic equations and show that the only stationary solution appropriate to the solar corona is the critical solution, which passes straight across the critical point and yields supersonic (500-km/sec) expansion at infinity. In the second part of the paper we show that the evaporative solutions are incompatible with the hydrodynamic equation and hence incompatible with the Boltzmann equation. Title: Statement of Agreement regarding the Ring-Current Effect Authors: Hines, C. O.; Parker, E. N. Bibcode: 1960JGR....65.1299H Altcode: In an earlier communication [Hines and Parker, 1958], we recorded discrepant views regarding the possible magnetic effects at the ground caused by a hypothetical ring current in the earth's exosphere. This followed upon earlier statements by Parker [1956, 1958a and b] to the effect that only an increase of geomagnetic field could be produced in a reasonably short time by such a current, as a consequence of exospheric shielding, and conflicting statements by Hines [1957] and Hines and Storey [1958] to the effect that geomagnetic field changes of either sense could be propagated rapidly through the exosphere by hydromagnetic waves. In view of the interest that this controversy appears to have raised, and because of the basic importance of the consequences in geomagnetic storm theory, we wish now to record a reconciliation of views, to the effect that circulating charge high in the exosphere can indeed be associated with a decrease of geomagnetic field at ground level in a reasonably short time and, therefore, may indeed be responsible for the main phase of a geomagnetic storm. In order to clarify the basic features of the controversy most readily, the original discrepant views will be restated briefly in application to very extreme models where each in turn undoubtedly applies. It should be noted, however, that each view can in turn be justified for other models which bear a much closer resemblance to the circumstances of nature, and the separate conclusions were originally formulated with these other models in mind. Title: Extension of the Solar Corona into Interplanetary Space Authors: Parker, Eugene Bibcode: 1960exsp.conf...28P Altcode: No abstract at ADS Title: Extension of the Solar Corona into Interplanetary Space Authors: Parker, Eugene Bibcode: 1959JGR....64.1675P Altcode: I shall first write down a number of observational facts, and then in another column compare them with the results of the theoretical program we have been carrying out at Chicago over the past few years. The purpose of this comparison will be to suggest experiments, some of which are already in progress, and which will perhaps resolve a few of the difficulties in our present knowledge of the dynamics of the interplanetary medium. I shall start with the sun, since we believe, as Gold and others have pointed out, that it is the source of energy for all phenomena observed in the earth, in particular magnetic storms and auroras, and the source of energy for all the churning that apparently occurs in interplanetary space. Let me list a few basic facts about the sun that seem most pertinent to the problem. Title: Plasma Dynamical Determination of Shock Thickness in an Ionized Gas (a Correction). Authors: Parker, E. N. Bibcode: 1959ApJ...129..860P Altcode: No abstract at ADS Title: Plasma Dynamic Determination of Shock Thickness in an Ionized Gas. Authors: Parker, E. N. Bibcode: 1959ApJ...129..217P Altcode: It is shown that the principal interaction in a shock front in a tenuous ionized gas is a plasma interaction in which the ions transfer their translational energy to the plasma oscillations. The effect is, of course, of interest in auroral theories and in solar radio noise. It turns out to be the dominant effect in determining shock thicknesses nearly everywhere that the gas density is less than the solar photospheric value of 1016 atoms/cm3. We estimate that shock thicknesses in interstellar H ii regions and in interplanetary space will be 1 km or less, even though the mean free paths may be 108 km or more and the ion Larmor radius 100 km. Title: Inadequacy of Ring-Current Theory for the Main Phase of a Geomagnetic Storm Authors: Parker, E. N. Bibcode: 1958JGR....63..683P Altcode: It is demonstrated that there is apparently not enough dissipation to allow significant diffusion, during a magnetic storm, of the magnetic fields in the vicinity of the earth. It is then demonstrated that a ring-current field can only increase the horizontal component of the geomagnetic field, and so cannot account for the main phase of a geomagnetic storm. Thus, other storm mechanisms must be sought. Title: Statement of Differences Regarding the Ring-Current Effect Authors: Hines, C. O.; Parker, E. N. Bibcode: 1958JGR....63..691H Altcode: The two preceding articles have expressed different views concerning the possible effects of ring currents, and have supported those views at some length by quite distinct analyses. It is probable that the essential points of difference which still remain require clarification, and the purpose of this note is to provide that clarification. The statements made here are based on views expressed in a lengthy private correspondence between the present authors, who, unfortunately, were unable to reconcile their differences. In Parker's view, a magnetic field such as that pictured in Figure 1 would be distorted for an extremely long time into the form given in Figure 2, following the introduction of a line-current source such as that indicated. The shaded areas are intended to represent the region filled by a highly conducting fluid, before and after the establishment of the current; the unshaded areas represent the space swept clear of fluid by the newly created ring-current field. This picture is based on the fact that the equations describing electromagnetic effects in a conducting fluid can be written in the usual hydromagnetic form ? which implies that the lines of force and the fluid move exactly together. From this, Parker deduces that the field of a newly created ring current cannot immediately penetrate the surrounding gas, and so will push back the gas and the pre-existent field lines, as in Figure 2. Title: Suprathermal Particles. III. Electrons Authors: Parker, E. N. Bibcode: 1958PhRv..112.1429P Altcode: Certain phenomena in nature, such as the 50- to 100-kev electrons of the aurora, suggest that there are plasma-dynamical processes which can quickly transfer the translational energy of the ions in a plasma stream to the electrons (some 20 kev/ion for a 2000-km/sec solar wind). It is shown that two interpenetrating streams of noncolliding and initially neutral plasma can achieve this energy transfer with a characteristic time comparable to (Mm)12 times the plasma period. The process is closely analogous to the excitation of plasma oscillations by two interpenetrating electron streams, but of course proceeds to much greater electron energies because the ion components of the streams carry so much more kinetic energy than do the electron components. Hence, besides the auroral electrons, it is probably responsible for solar radio emission, rather than the electron streams implied in current theories. Further, the process is probably the dominant interaction in shock fronts, particularly in astrophysical cases where neither direct collisions nor the existing weak magnetic fields can give sharp fronts. The characteristic thickness of a shock front in the solar wind is of the order of 104 cm due to the above plasma excitation whereas the Larmor radius of the ions, which would otherwise determine the shock thickness in the absence of collisions, is 100 km or more. Title: Suprathermal Particle Generation in the Solar Corona. Authors: Parker, E. N. Bibcode: 1958ApJ...128..677P Altcode: It is shown that hydromagnetic waves propagating outward through the solar corona will convert all but a small portion of their energy into suprathermal particles It is suggested that this is the source, of the 3 X 1028 ergs/sec necessary to maintain the 2 X 108 0K solar corona with its continued expansion into the solar wind The temperature of the solar corona will then correspond to an ion thermal velocity of the same order of magnitude as the hydromagnetic wave velocity. Title: Dynamics of the Interplanetary Gas and Magnetic Fields. Authors: Parker, E. N. Bibcode: 1958ApJ...128..664P Altcode: We consider the dynamical consequences of Biermann's suggestion that gas is often streaming outward in all directions from the sun with velocities of the order of 500-1500 km/sec. These velocities of 500 km/sec and more and the interplanetary densities of 500 ions/cm3 (1014 gm/sec mass loss from the sun) follow from the hydrodynamic equations for a 3 X 1060 K solar corona. It is suggested that the outward-streaming gas draws out the lines of force of the solar magnetic fields so that near the sun the field is very nearly in a radial direction. Plasma instabilities are expected to result in the thick shell of disordered field (10- gauss) inclosing the inner solar system, whose presence has already been inferred from cosmic-ray observations. Title: Suprathermal Particles Authors: Parker, E. N.; Tidman, D. A. Bibcode: 1958PhRv..111.1206P Altcode: The production of suprathermal particles in agitated plasmas bearing magnetic fields is discussed. This is done by setting up a Fokker-Planck equation to describe the phenomenon. The role of such particles in astrophysics and in the problem of the production of thermonuclear power is considered. Title: Gross Dynamics of the Interstellar Medium Authors: Parker, E. N. Bibcode: 1958RvMP...30..955P Altcode: 1958IAUS....8..955P No abstract at ADS Title: Cosmic-Ray Modulation by Solar Wind Authors: Parker, E. N. Bibcode: 1958PhRv..110.1445P Altcode: It is shown that the hydrodynamic outflow of gas from the sun observed by Biermann results in a reduction of the cosmic-ray intensity in the inner solar system during the years of solar activity. The computed cosmic-ray energy spectrum so closely resembles the observed spectrum at earth that we suggest the outflow of gas to be the explanation for the 11-year variation of the cosmic-ray intensity. It is also suggested that perhaps the Forbush-type decrease, which is a local geocentric phenomenon, is the result of disordering of the outer geomagnetic field by the outflowing gas from the sun. Title: Electrical Conductivity in the Geomagnetic Storm Effect Authors: Parker, E. N. Bibcode: 1958JGR....63..437P Altcode: Hines1 has recently argued that it is possible for the magnetic field of a ring current to penetrate rapidly through the electrically conducting gas surrounding the earth because the geomagnetic field greatly reduces the conductivity perpendicular to the lines of force. In this way, he argues that a ring current can very quickly cancel (dissipate) part of the geomagnetic field at the surface of the earth to yield the main phase of a geomagnetic storm. Now it was first pointed out by Schlüter,2 and has since been discussed by Bungey,3 and by Cowling,4 that the decay or dissipation of a magnetic field is not enhanced by the reduction of conductivity perpendicular to B. As Cowling puts it, one is justified in discussing the conductivity only if at the same time he considers the effective electric field. Title: Interaction of the Solar Wind with the Geomagnetic Field Authors: Parker, E. N. Bibcode: 1958PhFl....1..171P Altcode: The dynamical properties of the solar wind blowing past the geomagnetic field are investigated by considering the effective viscosity and the resulting transition layer thickness. The collision of ions in the solar wind produces a negligible viscosity in the flow past the geomagnetic field, but such an inviscid flow is shown to be unstable. The resulting disordered interface between the field and the wind yields Fermi acceleration of ions and consequently a not insignificant effective viscosity. The Fermi acceleration results in suprathermal ions which may have an energy spectrum like that observed for primary auroral protons.

The auroral zones and the agitated nature of the polar geomagnetic field are shown to follow from the depth of penetration of the solar wind into the geomagnetic field. The injection of gas into the geomagnetic field is studied. The effect at Earth of the distortion of the outer boundary of the geomagnetic field is computed; no matter how unevenly and anisotropically the outer field is distorted, the effect at Earth is a nearly uniform perturbation field which is closely parallel to the geomagnetic axis. Pushing in on the outer field increases the horizontal component at Earth, and pulling out decreases it; the total increase of the horizontal component is the algebraic sum of all the pushing and pulling. The simultaneous world-wide onset and the main phase of a geomagnetic storm follow.

The common tendency of large and/or violent bodies of plasma to produce suprathermal particles is noted and suggested to be a general dynamical property. Title: Dynamical Instability in an Anisotropic Ionized Gas of Low Density Authors: Parker, E. N. Bibcode: 1958PhRv..109.1874P Altcode: It is shown that when the thermal motions of a tenuous ionized gas are sufficiently anisotropic, the gas, and the initially uniform magnetic field which the gas is assumed to contain, become unstable. One mode of instability occurs when the gas pressure is greater parallel to the field than perpendicular, and another mode when the pressure is greater perpendicular than parallel. It is suggested that such instabilities may be of astrophysical interest, particularly with regard to the configuration of the solar dipole field as it is drawn out into interplanetary space by ionized gas from the sun. Title: Origin and Dynamics of Cosmic Rays Authors: Parker, E. N. Bibcode: 1958PhRv..109.1328P Altcode: As a consequence of our inability to observe directly the origin of a cosmic-ray particle, we begin the development with a discussion of the limitations within which we can construct a cosmic-ray accelerator mechanism. We find that we are allowed only the betatron effect and the Fermi mechanism. We review some of the many variations of these mechanisms which are to be found in the literature. Then it is shown that trains of oppositely moving hydromagnetic waves of large amplitude and with sharp crests can accomplish large and continued particle accelerations which are adequate to maintain the observed galactic cosmic-ray field. The large acceleration arises as a consequence of the simple fact that each wave tends to sweep up the cosmic-ray particles before it, so that head-on collisions of particles with waves are much more common than overtaking collisions. It is pointed out that the sharp crests of the waves are a natural consequence of the observed supersonic mass motions. Therefore, the acceleration by oppositely moving waves does not depend upon any special wave form, and we suggest that it is the naturally occuring acceleration process. By treating the cosmic rays as a gas with relativistic thermal motions, it is shown that the cosmic-ray gas is effectively coupled to the motions of the ordinary matter both parallel and perpendicular to the magnetic field. Thus the effective speed of sound must be computed in the composite cosmic-ray and ordinary gas. It is noted that with this composite speed of sound the irregular mass motions in the galactic disk and halo are approximately Mach one. It is suggested that this represents a general dynamic balance to be found in all sufficiently active regions of space, and explains how it is that we often observe prolonged mass motions in the galaxy and in stellar atmospheres which would otherwise be computed to be highly supersonic and dissipative. The dynamic balance comes about from the fact that increased cosmic-ray density would reduce the effective Mach number below one, allowing the sharp crests of the hydromagnetic waves to degenerate, and thereby halting the production of comsic-ray particles. Title: On the Variations of the Primary Cosmic Ray Intensity Authors: Parker, E. N. Bibcode: 1958IAUS....6..420P Altcode: No abstract at ADS Title: Sweet's Mechanism for Merging Magnetic Fields in Conducting Fluids Authors: Parker, E. N. Bibcode: 1957JGR....62..509P Altcode: Sweet's mechanism for the merging of two oppositely directed magnetic fields in a highly conducting fluid is investigated in a semi-quantitative manner. It is shown that two oppositely directed sunspot fields with scales of 104 km could be merged by Sweet's mechanism, if shoved firmly together, in about two weeks; their normal interdiffusion time would be of the order of 600 years. It is suggested that Sweet's mechanism may be of considerable astrophysical importance: It gives a means of altering quickly the configuration of magnetic fields in ionized gases, allowing a stable field to go over into an unstable configuration, subsequently converting much of the magnetic energy into kinetic energy of the fluid. Title: Acceleration of Cosmic Rays in Solar Flares Authors: Parker, E. N. Bibcode: 1957PhRv..107..830P Altcode: It is shown that the white-light cosmic-ray solar flare of February 23, 1956 expended of the order of 2×1032 ergs of energy, or 104 ergs/cm3. The energy apparently came from a 500-gauss force-free magnetic field initially occupying the site of the flare. It is shown that the 500-gauss field, besides supplying the flare energy, will produce fluid motions of sufficient velocity to accelerate ions from thermal to relativistic energies by Fermi's mechanism in about 2 minutes. The theoretical energy spectrum of the model is in agreement with the observed spectrum. About one percent of the total flare energy is converted to relativistic particles and the remainder is dissipated through thermal processes to produce the observed optical radiation. Title: The Gross Dynamics of a Hydromagnetic Gas Cloud. Authors: Parker, Eugene N. Bibcode: 1957ApJS....3...51P Altcode: The tensor virial equations are applied to the dynamics of magnetic gas clouds in which self-gravitation is negligible, such as are presumed to be ejected from the sun into interplanetary space. To avoid the immense mathematical difficulties of a general treatment, we constrain the cloud to homogeneous, though not necessarily isotropic, dilatation. It is shown that, in the absence of an external magnetic - field surrounding the cloud, no static equilibrium is possible without non-vanishing external gas pressure. The unsymmetric expansion of a cloud along one axis is considered. In the presence of an external large-scale magnetic field surrounding the cloud, it is necessary, in order that we may compute the external field, to pad- the cloud surface so that the over-all shape will be ellipsoidal. Cloud equilibrium conditions are given in the presence of the external fiel 1. The force exerted on a cloud by a gradient in the external field is given; it is shown that a cloud expelled, like a melon seed, from a large-scale field may have a velocity as great the speed of sound or the Alfve'n wave velocity, whichever is greater. It is shown that a field-free cloud of gas be contained between constrictions in a large-scale field; but we do not expect to find permanent field-free clouds in nature because such a cloud will repeatedly split lengthwise or otherwise decrease one of its limit, until the field-free gas diffuses into the external field. - It is pointed out that, except -in special cases where the cloud is held together by constrictions in an external field, the existence of a static equilibrium requires that the lines of force of the internal cloud field be tangled. Title: The Solar Hydromagnetic Dynamo Authors: Parker, E. N. Bibcode: 1957PNAS...43....8P Altcode: No abstract at ADS Title: On the Geomagnetic Storm Effect Authors: Parker, E. N. Bibcode: 1956JGR....61..625P Altcode: The high electrical conductivity of the region surrounding Earth, inferred from the observations of atmospheric whistlers and the zodiacal light, requires abandoning the customary models for producing a geomagnetic storm field with impressed current system. It becomes necessary to adopt a purely hydromagnetic approach wherein one focuses his attention only on the magnetic lines of force of the geomagnetic field and their displacement with the conducting gas surrounding Earth. From the hydromagnetic point of view, a decrease of the horizontal component is brought about by lifting the lines of force in the region above the observer. It is suggested that heating in the upper atmosphere may produce the necessary lifting; this model, along with another, is developed quantitatively to show that lifting the lines of force a distance of only 5 km will produce a decrease in the horizontal component of 0.2 per cent at the equator. Title: Solar Cosmic Rays of February, 1956 and Their Propagation through Interplanetary Space Authors: Meyer, P.; Parker, E. N.; Simpson, J. A. Bibcode: 1956PhRv..104..768M Altcode: The data from six neutron-intensity monitors distributed over a wide range of geomagnetic latitudes have been used to study the large and temporary increase of cosmic-ray intensity which occurred on February 23, 1956, in association with a solar flare. During the period of enhanced intensity a balloon-borne neutron detector measured the absorption mean free path and intensity of the flare particles at high altitudes. From these experiments the primary particle intensity spectrum as a function of particle rigidity, over the range <2 to> 15-30 Bv rigidity, has been deduced for different times during the period of enhanced intensity. It is shown that the region between the sun and the earth should be free of magnetic fields greater than ~10-6 gauss and that the incoming radiation was practically isotropic for more than 16 hours following maximum flare particle intensity. The decline of particle intensity as a function of time t depends upon the power law t-32, except for high-energy particles and late times, where the time dependence approaches an exponential. The experiments lead to a model for the inner solar system which requires a field-free cavity of radius greater than the sun-earth distance enclosed by a continuous barrier region of irregular magnetic fields [B(rms)~10-5 gauss] through which the cosmic-ray particles must diffuse to reach interstellar space. This barrier is also invoked to scatter flare particles back into the field-free cavity and to determine the rate of declining intensity observed at the earth. The diffusion mechanism is strongly supported by the fact that the time dependence t-32 represents a special solution of the diffusion equation under initial and boundary conditions required by experimental evidence. The coefficient of diffusion, the magnitude of the magnetic field regions, the dimensions of the barrier and cavity, and the total kinetic energy of the high-energy solar injected particles have been estimated for this model. Recent studies of interplanetary space indicate that the conditions suggested by the experiments may be established from time to time in the solar system. The extension of the model to the explanation of earlier cosmic-ray flare observations appears to be satisfactory. The solar flare event was superposed by chance upon a large but typical intensity decrease of nonsolar cosmic rays which began several days prior to February 23. Hence, the flare particles have been used as probes to explore the intensity modulation mechanism responsible for this decrease of background cosmic-ray intensity. Title: Modulation of Primary Cosmic-Ray Intensity Authors: Parker, Eugene N. Bibcode: 1956PhRv..103.1518P Altcode: It is assumed that the cosmic-ray particles observed at the earth are of galactic origin, except for the occasional bursts from solar flares. With this interpretation the 11-year variation of the cosmic-ray intensity and the Forbush decreases represent depressions of the steady galactic intensity. The observed rigidity dependence of the depression indicates that magnetic fields are responsible. A quantitative investigation of the possible motion and configuration of magnetic fields capable of producing the observed effects is carried out. It is shown that, within the limitations imposed by what we think we know today of the galactic magnetic field, of solar activity, and of interplanetary fields, serious difficulties are encountered by any mechanism, such as Morrison's interplanetary cloud model, modulating the galactic cosmic-ray intensity throughout the solar system. It is proposed that the modulation of the intensity is produced locally, within a few earth's radii, by interplanetary magnetic gas clouds captured by the terrestrial gravitational field. Such a model seems to produce the observed effects on the basis of the known facts about solar activity. The most straightforward test of this geocentric model, independent of inferences from cosmic-ray effects, is the question of whether the absorption of the captured magnetic hydrogen gas can be detected as a narrow line in the center of the broad solar Lα emission line. Title: Diffusion and Severing of Magnetic Lines of Force. Authors: Parker, E. N.; Krook, M. Bibcode: 1956ApJ...124..214P Altcode: The general asymptotic form for the magnetic field in a diffusing flux tube is developed and applied to the problem of severing magnetic lines of force in a medium with finite electrical conductivity Calculations of the details of the severing and reconnection of lines of force are given for the formation of an idealized free meridional magnetic ring in a hydromagnetic dynamo, for the merging of idealized neighboring rings, and for the straightening of the lines in a twisted tube, in order to illustrate the general qualitative features of these processes as they would presumably occur in the core of the earth. The problem of two nearly intersecting slender flux tubes is considered in order to demonstrate how the lines of force of the lesser tube are diverted into the denser tube. Title: Hydromagnetic and Plasma Problems Authors: Parker, Eugene N. Bibcode: 1956SCoA....1...59P Altcode: No abstract at ADS Title: Hydromagnetic Dynamo Models. Authors: Parker, Eugene N. Bibcode: 1955ApJ...122..293P Altcode: The purpose of this paper is to investigate the steady-state amplification of magnetic fields in a fluid It is shown that a rotating sphere of conducting fluid can regenerate a dipole magnetic field. It is sufficient for the angular velocity of rotation to vary with distance from the axis of rotation and for cyclonic fluid motions to be present The nonuniform rotation generates a toroidal field from the dipole field; the cyclones generate, from the toroidal field, loops of flux in the meridional plane which coalesce to amplify the dipole field The rotating sphere is discussed in relation to the liquid core of the earth and the geomagnetic dipole field. If, instead of a rotating sphere, one has a prismatic volume of fluid, it is possible to construct migratory dynamo waves The dynamo waves are discussed in relation to the solar convective zone; it is shown that such waves can account for many of the principal features of the observed solar magnetic activity Title: Hydromagnetic Waves and the Acceleration of Cosmic Rays Authors: Parker, Eugene N. Bibcode: 1955PhRv...99..241P Altcode: The large amounts of energy necessary for the acceleration of cosmic rays throughout the galaxy introduces a serious transport problem. The hydrodynamic and hydromagnetic equations are investigated from the viewpoint of energy propagation. It is shown that, with the galactic model of Fermi and Chandrasekhar, the observed motions of the interstellar gas reduce to hydromagnetic waves, which are, as it turns out, the most effective means of energy transport. A consideration of the interaction of charged particles with hydromagnetic waves shows that it is the fluid velocity, and not the wave velocity, that is responsible for the acceleration of cosmic rays by Fermi's mechanism. We calculate the the dissipation of hydromagnetic waves in the interstellar medium, and the variation of amplitude and wavelength of such waves with changes in density and large-scale field intensity. It is then shown that the galaxy is no more than one percent efficient in the acceleration of cosmic rays because of the tremendous viscous losses in the interstellar medium, and that there is no hydromagnetic mechanism that can convert the observed large-scale low-velocity fluctuations in the interstellar medium to the required small-scale high-velocity motions. Title: The Formation of Sunspots from the Solar Toroidal Field. Authors: Parker, Eugene N. Bibcode: 1955ApJ...121..491P Altcode: It is shown that a horizontal magnetic flux tube in an electrically conducting atmosphere is buoyant and will tend to rise. This magnetic buoyancy is large enough to bring an occasional strand of flux from the general solar toroidal field up into the photosphere, if we assume general field densities of a few hundred gauss farther down. Identifying the intersection of such ropes with the photosphere as the source of sunspots, we may deduce several general characteristics of the spots, e.g., east-west orientation, bipolarity, appearance only in low latitudes, migration, reversal of polarity, etc. The linearized static equilibrium equations for a flux tube are developed. With a cooling mechanism, such as that suggested by Biermann (1941), we find from the equilibrium equations that a sunspot group should consist of a diffuse flux tube of 10-100 gauss and 10 km extent in the photosphere, forming eventually a number of cool intense cores of several thousand gauss. Title: Instability of Thermal Fields. Authors: Parker, Eugene N. Bibcode: 1953ApJ...117..431P Altcode: The field equation for the kinetic temperature, Te, is considered in the case of a gas composed of hydrogen-like atoms. If the atoms are largely ionized and free-free emission does not predominate, the thermal field is unstable unless stabilized by a strongly temperature-dependent supply of energy. The possibility of interpreting much of the thermal activity in the solar atmosphere as due to such instability is discussed. Title: On the instability of gaseous media. Authors: Parker, Eugene N. Bibcode: 1953AJ.....58Q..46P Altcode: Introducing the assumption that all large scale astrophysical structures, e.g., gas clouds, galaxies, etc. have formed by collapse of regions of an initially more homogeneous distribution of matter according to Jeans' gravitational instability criterion, it is possible to work backwards from existing conditions to the initial conditions. It is found that gravitational instability produces a collapse in which the scale of the final structure is approximately one-sixth of its original dimensions. This agrees with observations of the interstellar gas clouds which show that the clouds are separated by approximately twice the diameter of their extremities. Given the relative velocity of neighboring clouds, it is possible from the diameter of the clouds to determine the average density of the interstellar medium. The relative velocity 3 km/sec gives roughly 10 hydrogen atoms per cm1. This agrees with the average density computed by smearing out the estimated mass of the galaxy over the estimated dimensions of the galaxy. The collapse time in such a medium is of the order of I0~ years. On the other hand, galaxies are separated by distances of the order of 100 or more times their diameters, implying that they have separated greatly since their formation. Observations imply masses of the order of 1011 Mo and internal velocities 300 km/sec for the brighter galaxies. From these is predicted a relative velocity 50 km/sec for galaxies not in clusters. The observed motions and dimensions of both spheroidal and spiral galaxies yield an initial mean density of the order of 5 X 10-26 gm/cm3 at the time the collapse of the primordial homogeneous medium began. That both types give the same initial density suggests that regions not occupied by relatively active eddies have collapsed over smaller dimensions to form spheroidal galaxies, i.e., galaxies of low mass, whereas active regions, if they collapse at all, form the more massive galaxies. Finally, the collapse time for forming a galaxy is found to be of the order of 3 X 108 years. Department of Mathematics and Astronomy, University of Utah, Salt Lake City, Utah. Title: The Interstellar Structures. I. Gas Clouds. Authors: Parker, Eugene N. Bibcode: 1953ApJ...117..169P Altcode: In an effort to arrive at a dynamical model for the interstellar medium, its mechanical properties are discussed. Using a polytrope relation between the temperature and density within a gas cloud, the mechanical and then the statistical properties of an idealized model of the interstellar clouds are developed. One finds that the collision rate of clouds, computed in an elementary fashion from their diameters and random translational velocities, leads to several difficulties. First, the very inelastic nature of head-on collisions would rapidly reduce the translational velocities, and it would be difficult to explain the observed radial velocities. Second, there would be a strong tendency toward statistical equilibrium of the internal state of the clouds. The equilibrium is investigated, and the cloud is found to be either in a collapsed condition or completely dispersed, again contrary to observation. Ordering of the translational velocities is proposed as one means of circumventing these difficulties. In any case, the tendency of clouds to collapse, possibly to form clusters of stars, is shown to be intrinsic in their nature. Title: An analytical investigation of turbulence and acoustics in the solar ionization zone. Authors: Parker, Eugene N. Bibcode: 1952AJ.....57Q..22P Altcode: An investigation of the turbulence field to be expected in the solar ionization zone requires an extension of the existing turbulence theories to cover the case of an inhomogeneous field where convective forces are producing the turbulence. Heisenberg's development of isotropfc homogeneous turbulence was used because it affords a simple physical picture of turbulence and is therefore readily generalized to the inhomogeneous field. Isotropy was assumed for the solar convection turbulence field. A convective driving and a diffusion term were worked out on this basis and inserted in Heisenberg's field equation. Thus it is possible to compute the velocity field in the ionization zone as well as the diffusion of this turbulent velocity field up into the solar atmosphere. Second, in order to compute the acoustical radiation which the velocity field of the ionization zone produces, it was necessary to reformulate radiation theory since many misconceptions are associated with the conventional viewpoint. An inhomogeneous wave equation was obtained giving rigorously the velocities of radiation particles in terms of the velocity field producing the turbulence. Because of the complexity of the velocity of a turbulent field, the inhomogeneous term in the wave equation can be computed only approximately from the turbulence field. As a result of the above analysis the turbulence velocity field is found to have velocities 0.6 km$sec in agreement with observations on the solar granules.' Further, the turbulence diffuses only ~oo km into the atmosphere above the convection zone. The acoustical radiation for the entire velocity field is found to be completely inadequate to heat the corona. The differences between this and previous results by Mr. Schwarzschild2 are readil tracked down in the theory. Finally, from the reformulation of radiation theory it follows that supersonic turbulence in the chromosphere is an impossibility unless the entire energy of such a velocity field is replenished, say, every 50 seconds, a truly fantastic energy source being required. I.R. S. Richardson and M. Schwarzschild, Ap. J. iii, 351, 1950. 2.Ap. J. 107, 1, 1947. University of Utah, Salt Lake City, Utah. Title: The interstellar dust and gas structures Authors: Parker, Eugene Newman Bibcode: 1951PhDT........36P Altcode: An investigation of the statistical properties of the mechanics of the dust and gas structures making up the interstellar medium is carried out. The aim is to get a comprehensive picture of the general nature of the motions and structure of the interstellar material that would follow from certain simple assumptions. Comparison with observation then shows to what extent the behavior of the interstellar material can be accounted for on such a basis and to what extent further factors, such as for example magnetic fields, will have to be studied in the hope of finding more satisfactory agreement.In I the interstellar gas is considered. It is shown that the observed radial motions of the gas clouds, if unordered, give too high a kinetic temperature for one to account for the observed clumping of the gas into clouds. The stability of a clump of gas was investigated using a modification of the ideas commonly employed in the virial theorem. It is further shown that given discrete gas clouds, the unordered component of their proper motions must be even lower to prevent them from collapsing into extremely dense structures, possibly clusters of stars, after repeated low velocity collisions.In II the observed dust structures are considered and their general evolution under the influence of the velocity field of the gas and the radiation field is worked out. It is shown that for a continuous distribution of dust sizes, certain types of finely striated structures cannot be formed.From the inadequacies of this non-magnetic theory, one concludes that magnetic fields must play a very significant role in the dynamics of the interstellar medium.Finally, in III the collapse of a nonturbulent nonrotating dust cloud under its own gravitational field is very briefly considered yielding remarkably short collapse times of the order of only [...] years.