Two‐dimensional structures in a plane perpendicular to the magnetic field, of the low‐frequency turbulence in a toroidal plasma, have been studied. The probability distribution functions for the density and the potential fluctuations are found to deviate from the Gaussian distribution significantly indicating intermittency in the turbulence and formation and destruction of the coherent structures in the strongly turbulent state. The presence of such short‐lived structures has been established, on a statistical basis, by means of conditional averaging of the fluctuation amplitudes.

1.
P. K.
Shukla
,
M. Y.
Yu
,
H. U.
Rahman
, and
K. H.
Spastchek
,
Phys. Rep.
104
,
227
(
1984
);
P. K. Shukla, Proceedings of 1989 International Conferences on Plasma Physics, New Delhi, India, 22–28 Nov. 1989, edited by A. Sen and P. K. Kaw (Indian Academy of Sciences, Bangalore, 1991), p. 297.
2.
G.
Prasad
,
D.
Bora
, and
Y. C.
Saxena
,
Geophys. Res. Lett.
19
,
241
(
1991
);
G.
Prasad
,
D.
Bora
, and
Y. C.
Saxena
,
19
,
245
(
1992
).,
Geophys. Res. Lett.
3.
D.
Bora
,
Phys. Lett. A
139
,
308
(
1989
).
4.
Z.-S.
She
,
E.
Jackson
, and
S. A.
Orszag
,
Nature
344
,
226
(
1990
);
R. H.
Kraichnan
,
Phys. Rev. Lett.
65
,
575
(
1990
);
A.
Pumir
,
B.
Shraiman
, and
E. D.
Siggia
,
Phys. Rev. Lett.
66
,
2984
(
1991
); ,
Phys. Rev. Lett.
R.
Benzi
,
L.
Biferale
,
G.
Paladin
,
A.
Vulpiani
, and
M.
Vergassola
,
Phys. Rev. Lett.
67
,
2299
(
1991
).,
Phys. Rev. Lett.
5.
J. S. Bendat and A. G. Piersol, Engineering Applications of Correlation and Spectral Analysis, 2nd Rev. (Wiley, New York, 1986).
6.
A. Papoulis, Probability, Random Variables, and Stochastic Processes (McGraw-Hill, New York, 1984).
7.
R. J. Adrian, in Turbulence in Liquids, edited by G. K. Petterson and J. L. Zakin (Science, Princeton, NJ, 1977), p. 323;
Phys. Fluids
22
,
2065
(
1979
).
8.
R. F.
Blackwelder
and
R. E.
Kaplan
,
J. Fluid Mech.
76
,
89
(
1976
);
C. H.
Chen
and
R. F.
Blackwelder
,
J. Fluid Mech.
89
,
1
(
1978
).
9.
H.
Johnsen
,
H. L.
Pécseli
, and
J.
Trulsen
,
Phys. Rev. Lett.
55
,
2297
(
1985
);
H.
Johnsen
,
H. L.
Pécseli
, and
J.
Trulsen
,
Phys. Fluids
30
,
2239
(
1987
);
T.
Huld
,
A. H.
Nielsen
,
H. L.
Pécseli
, and
J.
Juul Rasmussen
,
Phys. Rev. Lett.
64
,
3023
(
1990
);
T.
Huld
,
A. H.
Nielsen
,
H. L.
Pécseli
, and
J.
Juul Rasmussen
,
Phys. Fluids B
3
,
1609
(
1991
).
10.
S. C.
Cowley
,
R. H.
Kulsrud
, and
R.
Sudan
,
Phys. Fluid B
3
,
2767
(
1991
).
11.
P. K. Kaw, R. Singh, A. Das, and N. Chakraborty, Proceedings of Technical Committee Meeting on Research Using Small Tokamaks, People’s Republic of China, 3–8 Oct. 1991 (International Atomic Energy Agency, Vienna, 1991), p. 342.
12.
Amita Das, Sangeeta Mahajan, A. Sen, P. K. Kaw, S. Benkadda, and A. Verga (private communication, 1993).
This content is only available via PDF.
You do not currently have access to this content.