A model based on magnetohydrodynamic (MHD) stability of the tokamak plasma edge region is presented, which describes characteristics of edge localized modes (ELMs) and the pedestal. The model emphasizes the dual role played by large bootstrap currents driven by the sharp pressure gradients in the pedestal region. Pedestal currents reduce the edge magnetic shear, stabilizing high toroidal mode number (n) ballooning modes, while at the same time providing drive for intermediate to low n peeling modes. The result is that coupled peeling–ballooning modes at intermediate n(3<n<20) are often the limiting instability which constrains the pedestal and triggers ELMs. These modes are characterized in shaped tokamak equilibria using an efficient new numerical code, and simplified models are developed for pedestal limits and the ELM cycle. Results are compared to several experiments, and nonideal MHD effects are briefly discussed.

1.
H.
Zohm
,
Plasma Phys. Controlled Fusion
38
,
105
(
1996
).
2.
W.
Suttrop
,
Plasma Phys. Controlled Fusion
42
,
A1
(
2000
).
3.
J. W.
Connor
,
Plasma Phys. Controlled Fusion
40
,
191
(
1998
).
4.
L. L.
Lao
,
Plasma Phys. Controlled Fusion
42
,
A51
(
2000
).
5.
P. B. Snyder and H. R. Wilson, “ELMs and the role of current-driven instabilities in the pedestal,” Contrib. Plasma Phys. (to be published).
6.
A. E.
Hubbard
,
Plasma Phys. Controlled Fusion
42
,
A15
(
2000
).
7.
T.
Hatae
,
M.
Sugihara
,
A. E.
Hubbard
et al.,
Nucl. Fusion
41
,
285
(
2001
).
8.
T. H.
Osborne
,
J. R.
Ferron
,
R. J.
Groebner
et al.,
Plasma Phys. Controlled Fusion
42
,
A175
(
2000
).
9.
J. R.
Ferron
,
M. S.
Chu
,
G. L.
Jackson
et al.,
Phys. Plasmas
7
,
1976
(
2000
).
10.
D. Mossessian, P. B. Snyder, M. Greenwald, J. W. Hughes, Y. Lin, A. Mazurenko, S. Medvedev, H. R. Wilson, and S. Wolfe, “H-mode pedestal characteristics and MHD stability of the edge plasma in Alcator C-Mod,” Plasma Phys. Controlled Fusion (to be published).
11.
J. L.
Luxon
and
L. G.
Davis
,
Fusion Technol.
8
,
441
(
1985
).
12.
E. A.
Frieman
,
J. M.
Greene
,
J. L.
Johnson
, and
K. E.
Weimer
,
Phys. Fluids
16
,
1108
(
1973
).
13.
D.
Lortz
,
Nucl. Fusion
15
,
49
(
1975
).
14.
J. A.
Wesson
,
Nucl. Fusion
18
,
87
(
1978
).
15.
J. W.
Connor
,
R. J.
Hastie
,
H. R.
Wilson
, and
R. L.
Miller
,
Phys. Plasmas
5
,
2687
(
1998
).
16.
C.
Mercier
,
Nucl. Fusion
1
,
47
(
1960
);
C.
Mercier
,
Nucl. Fusion Suppl.
2
,
801
(
1962
).
17.
C. C.
Hegna
,
J. W.
Connor
,
R. J.
Hastie
, and
H. R.
Wilson
,
Phys. Plasmas
3
,
584
(
1996
).
18.
H. R.
Wilson
,
J. W.
Connor
,
A. R.
Field
,
S. J.
Fielding
,
R. L.
Miller
,
L. L.
Lao
,
J. R.
Ferron
, and
A. D.
Turnbull
,
Phys. Plasmas
6
,
1925
(
1999
).
19.
H. R.
Wilson
and
R. L.
Miller
,
Phys. Plasmas
6
,
873
(
1999
).
20.
P. B.
Snyder
,
H. R.
Wilson
,
X. Q.
Xu
,
J. R.
Ferron
,
L. L.
Lao
,
M. S.
Chu
,
E. J.
Strait
, and
A. D.
Turnbull
,
Europhys. Conf. Abstr.
24B
,
324
(
2000
).
21.
J. W.
Connor
,
R. J.
Hastie
, and
J. B.
Taylor
,
Phys. Rev. Lett.
40
,
396
(
1978
).
22.
H. R.
Wilson
,
P. B.
Snyder
,
G. T. A.
Huysmans
, and
R. L.
Miller
,
Phys. Plasmas
9
,
1277
(
2002
).
23.
A. B.
Mikhailovskii
,
G. T. A.
Huysmans
,
S. E.
Sharapov
, and
W.
Kerner
,
Plasma Phys. Rep.
23
,
844
(
1997
).
24.
L.C.
Bernard
,
F. J.
Helton
, and
R. W.
Moore
,
Comput. Phys. Commun.
24
,
377
(
1981
).
25.
M.
Keilhacker
and the
JET Team
,
Plasma Phys. Controlled Fusion
41
,
B1
(
1999
).
26.
H.
Shirai
and
the JT-60 Team
,
Phys. Plasmas
5
,
1712
(
1998
).
27.
I. H.
Hutchinson
,
R.
Boivin
,
F.
Bombarda
et al.,
Phys. Plasmas
1
,
1511
(
1994
).
28.
T. W. Petrie, J. G. Watkins, L. L. Lao, and P. B. Snyder, “The role of magnetic balance on the poloidal distribution of ELM-induced peak particle flux at the divertor targets,” Phys. Rev. Lett. (to be submitted).
29.
L. L.
Lao
,
Y.
Kamada
,
T.
Oikawa
et al.,
Nucl. Fusion
41
,
295
(
2001
).
30.
T. S.
Hahm
and
P. H.
Diamond
,
Phys. Fluids
30
,
133
(
1987
).
31.
B. N.
Rogers
and
J. F.
Drake
,
Phys. Plasmas
6
,
2797
(
1999
).
32.
R. J.
Hastie
,
P. J.
Catto
, and
J. J.
Ramos
,
Phys. Plasmas
7
,
4561
(
2000
).
33.
G. T. A.
Huysmans
,
S. E.
Sharapov
,
A. B.
Mikhailovskii
, and
W.
Kerner
,
Phys. Plasmas
8
,
4292
(
2001
).
34.
K. V.
Roberts
and
J. B.
Taylor
,
Phys. Rev. Lett.
8
,
197
(
1962
).
35.
W. M.
Tang
,
R. L.
Dewar
, and
J.
Manickam
,
Nucl. Fusion
22
,
1079
(
1982
).
This content is only available via PDF.
You do not currently have access to this content.