Small-amplitude magnetohydrodynamic waves are studied in a dilute collisionless plasma with an anisotropic plasma pressure. The parallel and perpendicular pressure components are defined by two polytropic pressure laws. Previous results obtained within the framework of the Chew–Goldberger–Low double-adiabatic and double-isothermal models are recovered for specific values of the polytropic indices. The double-polytropic model can be considered as an extension of its single-polytropic counterpart model. Dispersion relations for the linear waves are derived and analyzed in the presence of pressure anisotropy. Particular cases of linear and nonlinear waves in a magnetic slab with double-polytropic plasma are investigated. The presence of the effective parallel and perpendicular sound speeds in the slab gives rise to a complicated interplay between kink and sausage modes supported by the slab. The behavior of weakly nonlinear waves in the slab are governed by the Benjamin–Ono equation. The soliton-like solution of this equation may be accelerated or retarded depending on the values of parallel and perpendicular sound speeds. The solitons are always accelerated in the magnetically dominated slab.

1.
G. F.
Chew
,
M. L.
Goldberger
, and
F. E.
Low
,
Proc. R. Soc. London, Ser. A
236
,
112
(
1956
).
2.
V. M.
Nakariakov
and
V. N.
Oraevsky
,
Sol. Phys.
158
,
29
(
1995
).
3.
P.
Song
,
C. T.
Russell
, and
M. F.
Thomsen
,
J. Geophys. Res.
97
,
8295
(
1992
).
4.
T. D.
Phan
,
G.
Paschmann
,
W.
Baumjohann
,
N.
Sckopke
, and
N.
Lühr
,
J. Geophys. Res.
99
,
121
(
1994
).
5.
E. J.
Weber
and
L. J.
Davis
,
J. Geophys. Res.
75
,
2419
(
1970
).
6.
M.
Tan
and
B.
Abraham-Shrauner
,
Cosm. Electrodyn.
3
,
71
(
1972
).
7.
S. J.
Bame
,
J. R.
Asbridge
,
W. C.
Feldman
,
M. D.
Montgomery
, and
S. P.
Gary
,
Geophys. Res. Lett.
2
,
373
(
1975
).
8.
Y.
Kato
,
M.
Tajiri
, and
T.
Taniuti
,
J. Phys. Soc. Jpn.
66
,
765
(
1966
).
9.
B. W.
Abraham-Shrauner
,
J. Plasma Phys.
1
,
361
(
1967
).
10.
L.-N.
Hau
and
B. U. Ö.
Sonnerup
,
Geophys. Res. Lett.
20
,
1763
(
1993
).
11.
L.-N.
Hau
and
C. A.
Lin
,
Phys. Plasmas
2
,
294
(
1995
).
12.
B. W.
Abraham-Shrauner
,
Plasma Phys.
15
,
375
(
1973
).
13.
M.
Goossens
,
M. S.
Ruderman
, and
J. V.
Hollweg
,
Sol. Phys.
157
,
75
(
1995
).
14.
F. F. Cap, Handbook on Plasma Instabilities (Academic, New York, 1976), p. 212.
15.
M. G. Kivelson and C. T. Russell, Introduction to Space Physics (Cambridge University Press, Cambridge, 1995), p. 350.
16.
B.
Roberts
,
Sol. Phys.
69
,
39
(
1981
).
17.
B.
Roberts
and
A. R.
Webb
,
Sol. Phys.
56
,
5
(
1978
).
18.
B.
Roberts
,
Phys. Fluids
28
,
3280
(
1985
).
19.
H.
Ono
,
J. Phys. Soc. Jpn.
39
,
1082
(
1975
).
This content is only available via PDF.
You do not currently have access to this content.