Low-Frequency Waves and Irregularities in the Ionosphere: Proceedings of the 2nd Esrin-Eslab Symposium, Held in Frascati, Italy, 23–27 September, 1968 PDF
Preview Low-Frequency Waves and Irregularities in the Ionosphere: Proceedings of the 2nd Esrin-Eslab Symposium, Held in Frascati, Italy, 23–27 September, 1968
LOW-FREQUENCY WAVES AND IRREGULARITIES IN THE IONOSPHERE ASTROPHYSICS AND SPACE SCIENCE LIBRARY A SERIES OF BOOKS ON THE RECENT DEVELOPMENTS OF SPACE SCIENCE AND OF GENERAL GEOPHYSICS AND ASTROPHYSICS PUBLISHED IN CONNECTION WITH THE JOURNAL SPACE SCIENCE REVIEWS Editorial Board J. E. BLAMONT, Laboratoire d'Aironomie, Verrieres, France R. L. F. BoYD, University College, London, England L. GoLDBERG, Harvard College Observatory, Cambridge, Mass., USA C. DE JAGER, University of Utrecht, Utrecht, Holland Z. KOPAL, University of Manchester, Manchester, England G. H. LUDWIG, NASA, Goddard Space Flight Center, Greenbelt, Md., USA R. LOsT, Institut fiir Extraterrestrische Physik, Garching-Miinchen, Germany B. M. McCoRMAC, Geophysics Division, liT Research Institute, Chicago, Ill., USA H. E. NEWELL, NASA, Washington, D.C., USA L. I. SEDOV, Academy of Sciences of the USSR, Moscow, USSR Z. SVESTKA, Czechoslovak Academy of Sciences, Ondfejov, Czechoslovakia Secretary of the Editorial Board W. DE GRAAFF, Sterrewacht 'Sonnenborgh', University of Utrecht, Utrecht, Holland VOLUME 14 LOW-FREQUENCY WAVES AND IRREGULARITIES IN THE IONOSPHERE PROCEEDINGS OF THE 2ND ESRIN-ESLAB SYMPOSIUM, HELD IN FRASCATI, ITALY, 23-27 SEPTEMBER, 1968 Edited by N. D'ANGELO European Space Research Institute, Frascati (Rome), Italy SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. The symposium was jointly sponsored by the European Space Research Institute ( Frascati, Italy) and the European Space Laboratory (Noordwijkerhout, The Netherlands) of the European Space Research Organisation ( ESRO) ISBN 978-94-010-3404-3 ISBN 978-94-010-3402-9 (eBook) DOI 10.1007/978-94-010-3402-9 © 1969. Springer Science+B usiness Media Dordrecht Originally published by D. Reidel Publishing Company, Dordrecht, Holland in 1969 Softcover reprint of the hardcover 1st edition 1969 No part of this book may be reproduced in any form, by print, photoprint, microfilm, or any other means, without written permission from the publisher FOREWORD During the last week of September 1968, ESRIN (the European Space Research Institute) held the ESRIN-ESLAB Symposium on 'Low-Frequency Waves and Irregularities in the Ionosphere' in Frascati, near Rome. The symposium was attended by about 60 participants, including speakers from most of the ESRO member states, the U.S.A., the U.S.S.R., and Peru. The main topics covered were: (a) observations of ionospheric irregularities by radar scattering, (b) scintillations of satellite signals, (c) geomagnetic micropulsations, and (d) whistlers. Both theoretical and observational aspects were treated. In addition, laboratory results on low-frequency waves in plasmas were discussed, emphasis being given to their possible relevance to low-frequency ionospheric phenomena. Finally, a brief presentation (not included in these proceedings) of the ESRO rocket and satellite program was given by Dr. Pedersen of ESLAB. The symposium provided an exchange of information among workers in closely related fields. It was also valuable in bringing together people whose experience is predominantly in ionospheric observations with others whose field of interest is mainly in plasma physics (theoretical or laboratory) - a combination that seemed particularly appropriate to ESRIN's program and functions. Several ESRIN staff members were instrumental in the organization of the meeting; among them Dr. G. Fiocco and Dr. K. Schindler, who helped in defining the scientific program. It is a pleasure to thank Miss M. Sachs, who did all the real work both in the preparation of the conference and for the publication of its proceedings. Permission from the copyright holders to reproduce some of the papers and a number of figures in these proceedings is gratefully acknowledged. N. D'ANGELO Frascati, February 1969 TABLE OF CONTENTS FOREWORD V DIETER PFIRSCH I Introductory Lecture on Ion Waves 1 H. KIKUCHI I General Features and Satellite Observations ofMagnetoionic and Magnetohydrodynamic Waves in the Outer Ionosphere 12 H. K. ANDERSEN, N. D'ANGELO, V. 0. JENSEN, P. MICHELSEN, and P. NIELSEN I Effects of Ion-Atom Collisions on the Propagation and Damping of Ion- Acoustic Waves 61 L. P. BLOCK and c.-G. FALTHAMMAR I Effects of Field-Aligned Currents on the Structure of the Ionosphere 69 N. D'ANGELO I Effects of Ion-Neutral Collisions on Ion-Acoustic Instabilities in the Auroral Ionosphere 78 N. D'ANGELO I Role of the Universal Instability in Auroral Phenomena 87 STANLEY D. SHAWHAN I Whistlers-Use for Determination of Composition and Temperature 94 STANLEY D. SHAWHAN I Observations of Ionospheric Very-Low-Frequency Radio Noise (Abstract) 110 T. STOCKFLET JORGENSEN 1V LF and LF Emissions at Auroral Latitudes 111 v. A. TROITSKA YA and A. v. GUL'ELMI I Diagnostics of the Parameters of the Magnetosphere and of the Interplanetary Space by Means of Micro- pulsations 120 T. M. GEORGES I Effects of Ionospheric Motions and Irregularities on HF Radio Propagation 137 BEN B. BALSLEY I Some Characteristics of Non-Two-Stream Irregularities in the Equatorial Electrojet 152 wALTER G. CHESNUT I Low Frequency Waves and Irregularities in the Auroral Ionosphere as Determined by Radar Measurements 173 L. LISZKA I Scintillations of Satellite Signals 192 G. K. HARTMANN I Inhomogeneities in the Ionosphere Measured by Radio Signals from the Beacon Satellite Explorer 22, Emphasizing Satellite Scintillations 207 NORMAN F. NESS I Observed Low Frequency Fluctuations in Space (Abstract) 216 E. RIEGER I Barium Release Experiments near the Magnetic Equator at Thumba, India (Abstract) 218 INTRODUCTORY LECTURE ON ION WAVES DIETER PFIRSCH Max-Planck-Institut /iir Astrophysik, Miinchen, W. Germany This lecture is to give to some extent a background for the understanding of the observations of low-frequency waves in the ionosphere. Certainly one is dealing with some kind of plasma oscillations. What can be their nature? There are quite a few possibilities for describing a plasma: one can regard it as an electrically conducting fluid, this being the so-called one-fluid model or magnetohydrodynamic approximation; or one can treat it as being composed of an electron fluid interpenetrated by an ion fluid (the two-fluid model). Both these models imply, as you know from ordinary hydrodynamics, that the collision mean free path of the particles is small compared with the macroscopic scale lengths involved. For our purposes these are the wavelengths of the oscillations. Examining the data of the ionosphere, one finds, however, that rather the opposite is true, the mean free path being very often larger than the wavelength divided by 2n. Thus, one cannot use one of the simple pictures just mentioned, and as always when collisions are rare one must turn to a more sophisticated description provided by a kinetic theory. Such a theory consists in Boltzmann-like equations for each particle species, i.e. we describe each species by a density in 6-dimensional phase space x, v. We call it f.(x, v, t), vindicating the species. Corresponding to fv we have current densities in x- and v-space given by xfv = vfv and Vfv = {1/mv) Kvfv, where mv is the mass of a particle of species v and Kv the force acting on such a particle. A continuity equation in phase space must then hold o-oftv + o-0·x { vfv) + o-0v· ( -1 K"' vfv ) = 0. mv It is the essential approximation of a Boltzmann-like equation that it splits the total force Kv into an average force Kv and a part which can be attributed to collisions and can then be approximated by some kind of collision term. We have then ofv ofv 1 ofv (ofv) at at + V. OX + mv Kv • OV = coli. Here it is assumed that (ojov) · Kv vanishes, which is true if Kv is the Lorentz force 1 Kv = ev(E +-V X B). c According to the definition of Kv the electric and magnetic fields E and Bare average fields; they arise not from single particles but from average particle densities and cur- D'Angelo (ed.), Low-Frequency Waves and Irregularities in the Ionosphere. All rights reserved 2 DIETER PFIRSCH rent densities, where these averages are calculated by the use off . in the form =I n.(x, t) J.(x, v, t) d3v =I n.v.(x, t) vf.(x, v, t) d3v. Inserting these expressions into the Maxwell equations we obtain a closed set of equations for f., E, B. A theory of this type is called a Vlasov theory if collisions are fully neglected. In the following, collisions of ions with neutrals are taken into account, but collisions between charged particles are neglected because of their low density, and collisions of electrons with neutrals because of the small cross-section. Because of the collisions between ions and neutrals, the ion distribution function, if disturbed, say in the form of a wave, tends to become equal to the distribution of the neutrals. The latter distribution can always be assumed to be a Maxwellian. Thus also the unperturbed ion distribution is a Maxwellian with a temperature T;. We will first consider waves under the assumption that the unperturbed state is homogeneous in space with an ion density n0• We then write for the unperturbed ion distribution fi0 = noftt (v) with and approximate the collision term for the ions simply by whereas we choose (ofefot)cou = 0 or formally We will now investigate the following situation: The unperturbed state is given by !? for the ions. The electrons are again described by a Maxwellian f~ = no(mef2nKTe)312 exp- (mef2KTe)(v- p)2 with density n and temperature Te which is generally different from T;. But we 0 allow this Maxwellian to be shifted by p in velocity space in the direction of the ionospheric magnetic field which is assumed to be constant in space and time. Thus we account for currents parallel to the magnetic field, which have been actually observed. We want to find out what kind of waves are possible in such a system, or more specifically what waves will have growing amplitudes, i.e. will be unstable. The latter is important, because perturbations in the form of waves are always present, but with very small amplitudes. Only growing waves will reach amplitudes that can be observed. Of course, such an instability must be due to the current. INTRODUCTORY LECTURE ON ION WAVES 3 I will not give a pure deductive theory here. This would not be very reasonable because of the tremendous number of degrees of freedom contained in our equations. At present one knows of about 50 different instabilities in plasma physics, and probably an infinite number exists. What will be done is to discuss from the beginning those waves which seem the most likely to explain certain phenomena. These are the so-called ion-acoustic waves in which only an electric field perturbation is present, the magnetic field remaining nearly unchanged. I will try, with an analytical treatment, to give you a feeling about the nature of these waves. The procedure will be first a more formal mathematical one, and then I will show you the physics behind it. What we have to do is to linearize our equations, mainly the Boltzmann equation yielding (with E1 /1 B0) o-f,l + vof-,1 + -e, E 1 -oofv,-o =- vJ• 1 . ot ox m, In order to find out how an initial perturbation will develop, we perform a Laplace transformation according to J00 f,1 (w), E1 (w) = eiwrf,1 (t), E1 (t) dt, Imw > 0 sufficiently 0 + 0I0- iy f,1 (t), E(t) = _1:_ e-iwrf,1 (co), E1 (w) dw, y > 0 sufficiently. 2n -oo +iy Then I00 a;/ eiwt dt =-f.~ (t = 0)- iwf.~ (w) 0 and our linearized equation reads, with f,1, E1 ~ eikx; x, v, E1 components parallel to the magnetic field B0, -i ( w+ivv-kv) f,I (w)+e-, E 1 -of=~ f,(t1 =O) m, ov from which we obtain f 1 ( w ) =e,-noE 1 1 of~ f,1 (t = 0) v m. i(w+iv.-kv) ov i(w+iv,-kv)' The first-order charge-density times 4n follows from this expression as I f 4nQ1 = 4n e. f,1 d3v I f I [ v J = 4-n -e;n-0 of~fov d 3 vE 1 - 4n e f.1 (t = 0) d 3 v . m. i(w + iv,- kv) v i(w + iv.- kv) v
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