Low-Frequency Waves and Irregularities in the Ionosphere: Proceedings of the 2nd Esrin-Eslab Symposium, Held in Frascati, Italy, 23–27 September, 1968

225 Pages·1969·9.626 MB·English

by  Dieter Pfirsch (auth.), N. D’angelo (eds.)

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