Plasma and the Universe: Dedicated to Professor Hannes Alfvén on the Occasion of His 80th Birthday, 30 May 1988 PDF
Preview Plasma and the Universe: Dedicated to Professor Hannes Alfvén on the Occasion of His 80th Birthday, 30 May 1988
PLASMA AND THE UNIVERSE Dedicated to Professor Hannes Alfven on the Occasion of His 80th Birthday, 30 May 1988 Guest Editors CARL-GUNNE FALTHAMMAR Royal Institute oj Technology, Stockholm, Sweden GUST AF ARRHENIUS Scripps Institution oj Oceanography, University oj California, La Jola, California, U.S.A. BIBHAS R. DE Chevron Oil Field Research Company, La Habra, California, U.S.A. NICOLAI HERLOFSON Royal Institute oj Technology, Stockholm, Sweden D. ASOKA MENDIS, University oj California at San Diego, La Jolla, California, U.S.A. and ZDENEK KOPAL Department oj Astronomy, The University, Manchester, U.K. Reprinted from Astrophysics and Space Science Vol. 144, Nos. 112 (1988) Kluwer Academic Publishers Dordrecht / Boston / Lancaster Library of Congress Cataloging in Publication Data ISBN-13: 978-94-010-7858-0 e-ISBN-13: 978-94-009-3021-6 DOl: 10.1007/978-94-009-3021-6 CIP-data will appear on separate card. Published by Kluwer Academic Publishers, P.O. Box 17, 3300 AA Dordrecht, The Netherlands. Kluwer Academic Publishers incorporates the publishing programmes of D. Reidel, Martinus Nijhoff, Dr W. Junk and MTP Press. Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers, 101 Philip Drive, Norwell, MA 02061, U.S.A. In all other countries, sold and distributed by Kluwer Academic Publishers Group, P.O. Box 322, 3300 AH Dordrecht, The Netherlands. All Rights Reserved © 1988 by Kluwer Academic Publishers Softcover reprint ofthe hardcover 1st edition 1988 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner. ASTROPHYSICS AND SPACE SCIENCE / Vol. 144 Nos. 1-2 May 1988 SPECIAL ISSUE PLASMA AND THE UNIVERSE Dedicated to Professor Hannes A!fven on the Occasion of His 80th Birthday, 30 May 1988 Guest Editors CARL-GUNNE FALTHAMMAR, GUSTAF ARRHENIUS, BIBHAS R. DE, NICOLAI HERLOFSON, D. ASOKA MENDIS, and ZDENEK KOPAL CARL-GUNNE FALTHAMMAR, GUSTAF ARRHENIUS, NICOLAI, BIBHAS R DE, HERLOFSON, D. ASOKA MENDIS, and ZDENEK KOPAL / Special Issue Dedicated to Professor Hannes Alfven on the Occasion of His 80th Birthday, 30 May 1988 LENNART LINDBERG / Observations of Propagating Double Layers in a High Current Dis- charge 3 N. BRENNING and I. AXNAS / Critical Ionization Velocity Interaction: Some Unsolved Problems 15 B. LEHNERT / Velocity Limitation ofa Neutral Dust Cloud Colliding with a Magnetized Plasma 31 MICHAEL A. RAADU and J. JUUL RASMUSSEN / Dynamical Aspects of Electrostatic Double Layers 43 PER CARLQVIST / Cosmic Electric Currents and the Generalized Bennett Relation 73 WALTER 1. HEIKKILA / Elementary Ideas Behind Plasma Physics 85 BIBHAS R DE / The Dielectric Analogue of Magnetohydrodynamics 99 CARL-GUNNE FALTHAMMAR / Magnetosphere-Ionosphere Interactions - Near-Earth Mani- festations of the Plasma Universe \05 L. P. BLOCK / Acceleration of Auroral Particles by Magnetic-Field Aligned Electric Fields 135 BENGT HULTQVIST and RICKARD LUNDIN / Parallel Electric Fields Accelerating Ions and Electrons in the Same Direction 149 T. A. POTEMRA / Birkeland Currents in the Earth's Magnetosphere 155 P. E. SANDHOLT and E. EGELAND / Auroral and Magnetic Variations in the Polar Cusp and Cleft - Signatures of Magnetopause Boundary-Layer Dynamics 171 C. E. McILWAIN / Plasma Acceleration, Injection, and Loss: Observational Aspects 201 M. HORANYI, H. L. F. HOUPIS, and D. A. MENDIS / Charged Dust in the Earth's Magnetosphere 215 SHELLEY H. ROGERS and ELDEN C. WHIPPLE / Generalized Adiabatic Theory Applied to the Magnetotail Current Sheet 231 R-L. XU / Particle Dynamics and Currents in the Magnetotail 257 L. J. LANZEROTTI and C. G. MACLENNAN / Hydromagnetic Waves Associated with Possible Flux Transfer Events 279 J. N. TOKIS / Free Convection and Mass Transfer Effects on the Magnetohydrodynamic Flows Near a Moving Plate in a Rotating Medium 291 iv TABLE OF CONTENTS S.-1. AKASOFU / An Electric-Current Description of Solar Flares 303 CORNELIS DE JAGER / Solar Flares through Electric Current 311 J. O. STENFLO / Global Wave Patterns in the Sun's Magnetic Field 321 D. LAL / Temporal Variations of Low-Energy Cosmic-Ray Protons on Decade to and Million Year Time-Scales: Implications to Their Origin 337 W.-H. IP / Electrodynamics of the EUV/X-ray Bright Point and Filamentary Flux Loop Complexes 347 Y. OHMAN / Peculiar Solar Flares and Plages of Possible Interest for the Study of Electric Quadrupole Lines of NaI and Mgn 353 GUSTAF ARRHENIUS and SUSANNE ARRHENIUS / Band Structure of the Solar System: An Objective Test of the Grouping of Planets and Satellites 357 MICHEL AZAR and WILLIAM B. THOMPSON / The Cosmogonic Shadow Effect 373 MURRAY DRYER, ZDENKA KOPAL SMITH, and SHI TSAN WU / The Role of Magneto- hydrodynamics in Heliospheric Space Plasma Physics Research 407 A. A. GALEEV and R. Z. SAGDEEV / Alfven Waves in a Space Plasma and Its Role in the Solar Wind Interaction with Comets 427 K. SZEGO / Modeling a Cometary Nucleus 439 ANTHONY L. PERATT and A. J. DESSLER / Filamentation of Volcanic Plumes on the Jovian Satellite 10 451 S. M. KRIMIGIS and D. VENKATESAN / In Situ Acceleration and Gradients of Charged Particles in the Outer Solar System Observed by the Voyager Spacecraft 463 E. MOBIUS, B. KLECKER, D. HOVE STADT, and M. SCHOLER / Interaction of Interstellar Pick-Up Ions with the Solar Wind 487 K. MARTI and H. E. SUESS / The Even-Odd Systematics in R-Process Nuclide Abundances 507 IMRE RUFF, GEORGE MARX, and DAVID S. DEARBORN / The Solubility Problem of Heavy Elements in Internal Stellar Plasma Revisited 519 K. PAPADOPOULOS / Electron Heating in Superhigh Mach Number Shocks 535 K. D. COLE / 'Dead' Pulsars: Cosmic-Ray Sources 549 ZDENEK KOPAL / The Effects of Mutual Irradiation on the Observed Radial Velocity of the Components of Close Binary Systems 557 MICHEL AZAR and W. B. THOMPSON / Magnetic Confinement of Cosmic Clouds 587 T. W. HARTQUIST and J. E. DYSON / Mass Pick-Up in Astronomical Flows 615 SATIO HAYAKAWA / Infrared Emission from Interstellar Plasma 629 V. A. AMBARTSUMIAN / On the Fluctuations of the Surface Brightness of Galaxies 635 B. E. LAURENT, B. BONNEVIER, and P. CARLQVlST / On the Dynamics of the Metagalaxy 639 JUAN G. RODERER / Tearing Down Disciplinary Barriers 659 HANNES ALFVEN SPECIAL ISSUE DEDICATED TO PROFESSOR HANNES ALFVEN ON THE OCCASION OF HIS 80TH BIRTHDAY, 30 MAY 1988 Guest Editors CARL-GUNNE FALTHAMMAR, GUSTAF ARRHENIUS, BIBHAS R. DE, NICOLAI HERLOFSON, D. ASOKA MENDIS, and ZDENEK KOPAL HANNES ALFVEN AT EIGHTY Ten years ago, Astrophysics and Space Science dedicated its May issue to Professor Hannes Alfven on the occasion of his seventieth birthday. Time has now come to honour him on his eightieth birthday by publishing this special issue of Astrophysics and Space Science. The preface of the May 1978 issue outlined his life and work until then. In the decade that has passed since that time, the outstanding significance of his pioneering work has become even more evident. The waves that he discovered long ago are of fundamental importance to the whole field of plasma physics, in the laboratory as well as in space. Likewise, the concept of gyrocentre drift and the perturbation theory based on it are powerful tools for studying charged particle motion, and are being widely used and developed to ever higher sophistication. The critical velocity phenomenon in the inter action of a plasma and a neutral gas, which was proposed by Alfven with amazing intuition - subsequently observed experimentally and only much later explained by theoreticians - has attracted sharply increased interest in recent years, following its observation in space. The latest decade has not only verified the importance of Alfven's past work, it has also been a decade in which he has continued a very active scientific life with new contributions to science especially in the field of cosmogony. For example, he has made use of the latest data from the Voyager spacecraft to test, with remarkable success, his theoretical predictions about the detailed structure of the Saturnian rings. Hannes Alfven is, in the true sense of the words, a pioneer and an explorer who has opened new vistas in science. His early contributions earned him the Nobel Prize for Physics in 1970. These contributions date back to the 1940's and were at that time highly controversial and largely ignored by the scientific community. Much later the progress of experiments and observations have proved his ideas to be right. However, Hannes Alfven never rests on his laurels. In recent years his mind has turned to the 'Plasma Universe', ranging in space from the Earth's own neighbourhood throughout the dephts of the Cosmos, and in time to the events in the past that led to the formation of the solar system. Some of his concepts about the Plasma Universe are Astrophysics and Space Science 144 (1988) 1-2. © 1988 by Kluwer Academic Publishers. 2 BIBHAS R. DE ET AL. already receiving observational support. Others are still controversial, but, given the record of his previous contributions, one may well find them to be validated by future observations. Not only has he contributed to science by his own work, but Hannes Alfven has also inspired a generation of young scientists worldwide. Everybody, including his critics, agrees that he is a fascinating and inspiring speaker. Especially in the last few years, his invited talks at major international conferences have been exceptionally well received. Most remarkably, at eighty Hannes A1fven remains vigorously active both in his profession and in human affairs. We and his many other friends worldwide hope that for many years to come we shall have the privilege of his collaboration, his inspiration, and his contributions to science. GUSTAF ARRHENIUS BIBHAS R. DE CARL-GUNNE FALTHAMMAR NICOLAI HERLOFSON ZDENEK KOPAL D. ASOKA MENDIS OBSERVATIONS OF PROPAGATING DOUBLE LAYERS IN A HIGH CURRENT DISCHARGE* LENNART LINDBERG Department of Plasma Physics, The Royal Institute of Technology, Stockholm, Sweden (Received 30 September, 1987) Abstract. Observations of current disruptions and strong electric fields along the magnetic field in a high-density (2 x 1019m-3), highly-ionized, moving, and expanding plasma column are reported. The electric field is interpreted in terms of propagating, strong electric double layers (3-5 kV). An initial plasma column is formed in an axial magnetic field (0.1 T) by means of a conical theta-pinch plasma gun. When an axial current (max 5 kA, 3-5 kV) is drawn through the column spontaneous disruptions and double-layer formation occur within a few microseconds. Floating, secondary emitting Langmuir probes are used. They often indicate very high positive potential peaks (1-2 kV above the anode potential during a few J.ls) in the plasma on the positive side of the double layer. Short, intense bursts of HF radiation are detected at the disruptions. 1. Introduction Current limitation in plasmas due to formation of electric double layers is a fundamental phenomenon of great importance in various branches of plasma physics, e.g., space physics and solar physics (Alfven, 1981, 1986; Block, 1978; Carlqvist, 1986) as well as in technical applications. Most laboratory investigations of double layers (DL) have been made in stationary or quasi-stationary plasmas, using sophisticated data averaging technique to allow comparison with theories. See Palmadesso and Papadopoulos (1979), Michelsen and Rasmussen (1982), Schrittwieser and Eder (1984). Only a few experiments with high-density, pulsed plasmas have been reported. Lutsenko et al. (1975) observed indications ofDLs by means of external, capacitively coupled probes. Torven and Babic (1975), in early experiments on current disruptions in low pressure arcs (ne < 5 X 1017 m -3), observed sharply localized potential jumps by means of capacitive probes. Inuzuka et al. (1985) have studied formation of strong DLs in an axial pinch. Takeda and Yamagiwa (1985) and Yamagiwa and Takeda (1987) claim to have observed short-lived DLs with extremely high voltage and reversed polarity. 2. Experimental Device We have used an electrodeless plasma gun (conical theta-pinch) to create an initial, highly ionized plasma column in an axial magnetic field (0.1 T) (Figure 1). The current in the theta-pinch coil oscillates as a damped 300 kHz sinusoid, beginning at t = O. The plasma is mainly ejected during the second half period. Thereafter, another condenser * Paper dedicated to Professor Hannes Alfven on the occasion of his 80th birthday, 30 May 1988. Astrophysics and Space Science 144 (1988) 3-13. © 1988 by Kluwer Academic Publishers. 4 L. LINDBERG B jJMW ==~:> s Fast gas ~-pinch = valve coil ~ E GP Um = pump s LfE;c Fig. I. Cross-section of apparatus. Theta-pinch plasma gun produces an argon plasma column in an axial magnetic field, 0.1 T. 20-50 its later an axial current is drawn through the column by a capacitor bank of transmission-line type, between GD (or gas valve GV) and the grounded end plate E (at z = 740 mm). Base vacuum < 0.2 mPa. Double layers are observed by floating probes PI' P2 connected to capacitive voltage dividers. A microwave transmission link is placed between the probes. The axial z-coordinate is measured from GD, in the flow direction. bank, of transmission-line type, is switched in to set up an axial current through the plasma column (C = 7 IlF, L = 0.4 IlH, Rs :::::: 1 n, Ub = ± 3 to 5 kV). If short-circuited, the bank would give a constant current Ub/(Rs + JL/C) for about 70 IlS, which then decays without reversal. We have chosen this current value well above what corresponds to the thermal electron current density in the plasma column. The end electrode E (Figure 1) is always connected to ground through four symmetri cally arranged metal strips s with low inductance. In the case illustrated in Figure 1 the condenser bank is charged negative, and either a coarse grid GD, or the end surface of the fast gas valve GV, in the plasma gun is used as cathode. Ls represents the stray inductance or any additional inductance in the circuit. In this configuration E is anode and the current flows antiparallel to the motion and expansion of the plasma. Experi ments are also made with positive polarity (parallel current), with E as cathode, GV as anode. Whenever GV is used as electrode the grid GD is removed. A glass plate GP with 65 mm aperture prevents radial spreading of the discharge. Experimental parameters are: the kind of gas (H2 or Ar), the amount of gas admitted to the gun, and the time at which the axial current is initiated. We choose this time short, 20-50 IlS to be sure the plasma is free from contact with walls. This, however, has the consequence that the plasma is still in motion, expanding from the gun, during the axial discharge. The plasma gun has previously been described in several papers, eg.., Danielsson and Brenning (1975), Lindberg (1978), Brenning et al. (1981). According to previous PROPAGATING DOUBLE LAYERS IN A HIGH CURRENT DISCHARGE 5 measurements the plasma is sent out in a narrow time interval at time tern (~2 /ls) in the second half cycle of the theta-pinch current, and the ions expand approximately as free particles. At a distance s from the gun, the plasma (ion) velocity is approximately described by a hyperbola (1) (for t > tern + 2 /ls); and the density increases monotonically during the time of interest. Raadu (1979) made a theoretical study of the expansion process and the space and time evolution of the distribution functions. Records of four signals are stored in two Biomation 8100 waveform recorders with sampling interval 0.2 /lS. To achieve maximum transient response anti-aliasing filters are not used, but the sampling instants of the four channels have been carefully synchronized by means of individual signal delay cables, so that all samples are taken synchronously with an accuracy within 10 ns. Hence, we are sure that any difference, e.g., between two probe voltage signals is true. Probe voltage changes are measured by means of high impedance, purely capacitive voltage dividers, 4: 40000 pF (Craggs and Meek, 1954). As one method to achieve an operating point not too far from the plasma potential, a bias circuit Ubias, Rbias (Figure 1), has been used in some of the experiments (Lindberg and Kristoferson, 1970). Probe characteristics are further discussed in the Appendix. 3. Experimental Observations Transmission of8 mm microwaves indicates that the plasma density approaches or even exceeds the cut-off density (2 x 1019 m -3) at the time when the axial discharge is switched on. According to previous probe measurements the electron temperature is 5-10 eV. Hence, the Oebye length is ~ 0.01 mm and the random electron current density env/4 ~ 0.3 to 1 x 106 A m -2, corresponding to 1 to 3 kA in the plasma column. When the condenser bank can deliver a current well above this value current disruptions and OL formation occur at every shot when the current reaches a critical value. Figure 2(a) shows discharge current, microwave transmission and potential variations on two floating probes for a typical shot with negative U using the grid GO as cathode b - i.e., with the axial current antiparallel to the plasma stream. The first disruption is well reproducible and deep. The current is reduced to 10-20% of the initial value. Later follows a sequence of stochastic, smaller disruptions. The microwave transmission approaches slowly cut-off before the axial discharge, but is restored unexpectedly fast after the disruption. The biased probes are early driven down to near zero volts by the first arriving, very thin plasma (2 x 1016 m -3). The probe signals can be interpreted as follows: a OL, which is formed at the disruption upstream of both probes, arrives at 38 /lS to the first probe, moves further downstream and passes the second probe. It is then followed by three more OLs. To demonstrate the existence of a OL between the probes the difference of the probe voltages is calculated and plotted at the bottom of
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