Theoretical plasma studies for space physics applicatio

Tidman, D. A.

English

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FOR --
PLASMAS AhD SPACE PHYSICS 
Submitted to the 
National Aeronautics and Space Administration I 
by the I 
Institute for Fluid Dynamics and Applied Mathematics 
University of Maryland 
College Park, Maryland 
January 20th, 1966 
Principal Investigator: Derek A. Tidman 
Research Professc 
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https://ntrs.nasa.gov/search.jsp?R=19670008542 2020-03-16T19:04:26+00:00Z
The research vork described in this report is supported by Grant No, 
NaG-220-62. 
six nonth period from August 
The research supported at  the University of LM.arylc?nd by this Grant is in the 
field of basic theoretical Plasma Physics with applications to problems in 
Space P'nysics 
We shall outline briefly the work that has been carried out in the 
St 
1965 b,o 2:~auary 31 1966 of the above Grant, 
SI, PROGRESS REPORT OF CuRp\ENT RESEARCH PROGRAMS 
In the above six month period the various members of our group have 
made the following research contributions: 
Enhanced Fluctuations in Plasmas, D. A. Tidman, Tech. Note BN-426 (1965). 
This paper is to be published in the proceedings of the Symposium on 
tshe Dynamics of Fluids and Flasmas held at the University of Haryland in October 
1965. 
be published by Academic Press, 
The Spposium was dedicated t o  Professor Burgers and the proceedings will 
Most plasmas, whether they are produced in the laboratory or naturally 
occurring, are far from thermal equilibrium, 
they are very ''noisy", i.e., various modes of the plasma are highly excited to 
more than the energy of KT/2 per propagating mode appropriate t o  thermal 
equilibrium. This excited wave spectrum may tnke the form of macroscopic turbulence 
excited externally or by instabilities, or at a lower amplitude level is continually 
present in the form of the natural fluctuations of a many-body system. 
One consequence of this is that 
Such 
turbulent motion plays an impor:ant role  in the processes of scattering and 
emission of electroinagnetic radiation by a Flasza, aod also contributes to 
transport processes such as the rapid  diffusion 02  plasma across a magnetic 
field through wave-particle scattering, 
the paper, 
Some of these effects are discussed in 
The Role of Electrostatic Plasma Oscillations in Electron Scattering in the 
Earth's Outer Magnetosphere, 
Res., 1966). 
Aharon Eviatar (communicated to Journal of Geophys. 
The scattering of electrons in a spatially homogeneous magnetic field- 
free stable plasma by ion and electron plasma waves excited by suprathermal 
particles is considered using a test-particle approach. 
theory is modified and extended t o  the case of ion-waves propagating in a current 
bearing plasma. 
and in the transieion zone between the magnetosphere and the interplanetary medium, 
where the gemgnetic field is weak in the sense that n .(( w 
1 . It is found that interaction kdth electron plasma oscillations is 2 4nne w u- Pe m 
competitive with whistlers in scattering suprathernal electrons and that ion waves 
are the dominant mechanism for the diffusion of subthermal electrons across the 
magnetopause and the shock wave. 
A previously derived 
The results are applied to electrons in the Earth's magnetosphere 
eB . 2 2 (Q = E  , 2 Pe 
Enhanced Bremsstrahlung from Plasmas Containing Nonthermal Electrons, 
Tidman snd T. H. I)upree, Phys. Fluids 8, 1860 (1965) 
D. A. ..-... - 
We have calculated the bremsstrahlung emitted from thermal plasmas 
which co-exist with a flux of energetic (suprathermal) electrons. We find that 
under some circumstances the radiation emitted can be greatly increased canpared 
' 
L 
to the cnission Zron:  a Maxvellian ~l~-.:snia with no er,ergztic particles present, 
The e&anced tziilssicm occurs the F ~ : i c ! m m ~ d  and second hamonis of the electron 
plasma frcqueocy- 
Scattering of a Test-PartFc3.e -- .--..- b ~ ?  __--__I Enhanced Tlasaa Fluctuations, 
A. Eviatar, Phys. Fluids 2, 2053 (1965). 
D. A. Tidman and 
The scattering of a test-particle by enhanced electric field fluctu- 
ations in a plasma contaixing nontherrral electrons is considered, together with 
some characteristic rimes for wave-particle scattering in suck a plasma. The 
calculations are based on the Balescu-Lenard equation. 
Propagaticp of Correlations in a Boltzmann Gas, 
Re Caldmn (Maryland), 1966 ( th is  is being rewritten as a Princeton Tech. Note). 
New results are obtained on the propagation of correlations in a 
E., A.  Frieman (Princeton) and 
Boltzwan Gas on the scale of the  mean free path and the collisional time scale, 
This appears t o  support a conjecture of Green's 
* 
on this subject. 
* 
M, Green, Physica24, 393 (1958). 
- 8-1 Asymptotic Kinetic Equation -- for Inhomogeneous Plasma, 
communicated to Canadian Jouzrml of Physics, 1966). 
R. Guernsey ( t o  be 
A kinetic equation is derived vhich is a generalization of the 
Balescu-Lenard equation and applicable t o  weakiy i ~ h ~ g e ~ i x i i i o  pl~sm,2s.  
Plasma Radiation and Solsr Radio Outbursts 
This paper is in the course of preparation by D. Tidman, T. Birmingham 
(NASA C-ddard) and He Stainer, and will be communicated t o  the Astrophysical 
Journal. It contains a calculation of the splitting of the harmonics of plasma 
radiation nenr w ar.d i lw ?uc to a wezk mgilet ic  f i e l d ,  It provides a satis- 
factory explanation of the O E ~ S C X V C L ' ;  splitting of the t w o  bands of radiation 
emitted in Type EI solar radio ou.tbursts. 
e e 
Correlation Velocities, K .  Suchy, zomunicated to Annalen der Physik, Leipzig (1966). 
Witn the coefficients of a Taylor expansion of the correlation function 
-* 
C(f,r) 
to describe the space-Sine behaviow in a satisfying manner. 
geometrical. relationship among each other, 
computation of these coefficients are discussed. 
up to the second order in. S,t ,three (or four) velocities can be defined 
They have a simple 
The necessary measurements for the 
111. GENERAL CQMMENTS 
Eoth Mr. A. Eviatar and Mr. H. Stainer are in the course of writing 
their Ph.D. theses and should finish this activity sometime this Spring. Mr. 
Eviatar's work has dealt with the role of electrostatic plasma oscillations in 
electron scattering in the earth's outer magnetosphere. 
out calculations on the line splitting of plasma radiation due to weak magnetic 
Mr. Stainer has carried 
- 
fields. 
Various members of our group have contributed papers and seminars to 
meetings and research institutions in the six month period covered by this progress 
report. Among these was an invited paper entitled "Mechanisms for Type I i  Soiar 
Outbursts" by D. Tidman at the APS Plasma Division meeting in San Francisco. 
Tidman also gave colloquia on "Enhanced Bremsstrahlung and Solar Radio Noise" at 
Chicago (November 1965) and Columbia (December 1965) universities. 
Dr. 


Plasmas and space physics Progress report, 1 Aug. 1965 - 31 Jan. 1966

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