It is typically assumed that the kinetic and magnetic helicities play a crucial role in the growth of large-scale dynamo. In this paper, we demonstrate that helicity is not essential for the amplification of large-scale magnetic field. For this purpose, we perform nonhelical magnetohydrodynamic (MHD) simulation, and show that the large-scale magnetic field can grow in nonhelical MHD when random external forcing is employed at scale 1/10 the box size. The energy fluxes and shell-to-shell transfer rates computed using the numerical data show that the large-scale magnetic energy grows due to the energy transfers from the velocity field at the forcing scales.

1.
H. K.
Moffatt
,
Magnetic Field Generation in Electrically Conducting Fluids
(
Cambridge University Press
,
Cambridge
,
1978
).
2.
S. I.
Vainshtein
and
Y. B.
Zel'dovich
,
Sov. Phys. Usp.
15
,
159
(
1972
).
3.
S.
Childress
and
A. D.
Gilbert
,
Stretch, Twist, Fold: The Fast Dynamo
(
Springer-Verlag
,
Berlin
,
1995
).
4.
F.
Cattaneo
,
D. W.
Hughes
, and
J.
Thelen
,
J. Fluid Mech.
456
,
219
(
2002
).
5.
A.
Brandenburg
,
Astrophys. J.
550
,
824
(
2001
).
6.
A.
Brandenburg
,
Astrophys. J.
697
,
1206
(
2009
).
7.
K.
Subramanian
and
A.
Brandenburg
,
Mon. Not. R. Astron. Soc.
445
,
2930
(
2014
).
8.
A. A.
Schekochihin
,
S. C.
Cowley
,
S. F.
Taylor
,
J. L.
Maron
, and
J. C.
McWilliams
,
Astrophys. J.
612
,
276
(
2004
).
9.
A. A.
Schekochihin
,
S. C.
Cowley
,
S. F.
Taylor
,
G. W.
Hammett
,
J. L.
Maron
, and
J. C.
Mcwilliamss
,
Phys. Rev. Lett.
92
,
084504
(
2004
).
10.
R.
Kumar
,
M. K.
Verma
, and
R.
Samtaney
,
Europhys. Lett.
104
,
54001
(
2013
).
11.
G.
Glatzmaier
and
P.
Roberts
,
Nature
377
,
203
(
1995
).
12.
P.
Olson
,
U.
Christensen
, and
G. A.
Glatzmaier
,
J. Geophys. Res.
104
,
10383
, doi: (
1999
).
13.
A. R.
Choudhuri
,
Nature's Third Cycle: A Story of Sunspots
(
Oxford University Press
,
Oxford
,
2015
).
14.
A.
Gailitis
,
O.
Lielausis
,
S.
Dement'ev
,
E.
Platacis
,
A.
Cifersons
,
G.
Gerbeth
,
T.
Gundrum
,
F.
Stefani
,
M.
Christen
,
H.
Hänel
, and
G.
Will
,
Phys. Rev. Lett.
84
,
4365
(
2000
).
15.
R.
Stieglitz
and
U.
Müller
,
Phys. Fluids
13
,
561
(
2001
).
16.
R.
Monchaux
,
M.
Berhanu
,
M.
Bourgoin
,
M.
Moulin
,
P.
Odier
,
J. F.
Pinton
,
R.
Volk
,
S.
Fauve
,
N.
Mordant
,
F.
Pétrélis
,
A.
Chiffaudel
,
F.
Daviaud
,
B.
Dubrulle
,
C.
Gasquet
,
L.
Marié
, and
F.
Ravelet
,
Phys. Rev. Lett.
98
,
044502
(
2007
).
17.
F.
Plunian
,
R.
Stepanov
, and
P.
Frick
,
Phys. Rep.
523
,
1
(
2013
).
18.
A.
Brandenburg
,
Astrophys. J.
791
(
1
),
12
(
2014
).
19.
S.
Candelaresi
and
A.
Brandenburg
,
Phys. Rev. E
87
,
043104
(
2013
).
20.
T. A.
Yousef
,
T.
Heinemann
,
A. A.
Schekochihin
,
N.
Kleeorin
,
I.
Rogachevskii
,
A. B.
Iskakov
,
S. C.
Cowley
, and
J. C.
McWilliams
,
Phys. Rev. Lett.
100
,
184501
(
2008
).
21.
B. B.
Karak
,
L. L.
Kitchatinov
, and
A.
Brandenburg
,
Astrophys. J.
803
,
95
(
2015
).
22.
Y.
Ponty
and
F.
Plunian
,
Phys. Rev. Lett.
106
,
154502
(
2011
).
23.
U.
Frisch
,
Z. S.
She
, and
P. L.
Sulem
,
Physica D
28
,
382
(
1987
).
24.
M. K.
Verma
,
Phys. Rep.
401
,
229
(
2004
).
25.
E.
Dormy
and
A. M.
Soward
(Eds),
Mathematical Aspects of Natural Dynamos
(
CRC Press
,
Boca Raton
,
2007
).
26.
C.
Guervilly
,
D. W.
Hughes
, and
C. A.
Jones
,
Phys. Rev. E
91
,
041001
(
2015
).
27.
C.
Guervilly
,
D. W.
Hughes
, and
C. A.
Jones
,
J. Fluid Mech.
815
,
333
(
2017
).
28.
S. M.
Tobias
,
P. H.
Diamond
, and
D. W.
Hughes
,
Astrophys. J. Lett.
667
,
L113
(
2007
).
29.
K. H.
Rädler
and
A.
Brandenburg
,
Phys. Rev. E
77
,
026405
(
2008
).
30.
G.
Dar
,
M. K.
Verma
, and
V.
Eswaran
,
Physica D
157
,
207
(
2001
).
31.
A.
Pouquet
,
U.
Frisch
, and
J.
Léorat
,
J. Fluid Mech.
77
,
321
(
1976
).
32.
M. K.
Verma
,
Pramana
61
,
707
(
2003
).
33.
R.
Kumar
,
M. K.
Verma
, and
R.
Samtaney
,
J. Turbul.
16
,
1114
(
2015
).
34.
O.
Debliquy
,
M. K.
Verma
, and
D.
Carati
,
Phys. Plasmas
12
,
042309
(
2005
).
35.
A.
Alexakis
,
P.
Mininni
, and
A.
Pouquet
,
Phys. Rev. E
72
,
046301
(
2005
).
36.
R.
Moll
,
J. P.
Graham
,
J.
Pratt
,
R. H.
Cameron
,
W. C.
Müller
, and
M.
Schüssler
,
Astrophys. J.
736
,
36
(
2011
).
37.
M. K.
Verma
,
A.
Chatterjee
,
K. S.
Reddy
,
R. K.
Yadav
,
S.
Paul
,
M.
Chandra
, and
R.
Samtaney
,
Pramana
81
,
617
(
2013
).
38.
D.
Carati
,
S.
Ghosal
, and
P.
Moin
,
Phys. Fluids
7
,
606
(
1995
).
39.
H.
Chou
,
Astrophys. J.
556
,
1038
(
2001
).
40.
J.
Maron
,
S.
Cowley
, and
J.
McWilliams
,
Astrophys. J.
603
,
569
(
2004
).
41.
Y.
Ponty
,
P. D.
Mininni
,
D. C.
Montgomery
,
J. F.
Pinton
,
H.
Politano
, and
A.
Pouquet
,
Phys. Rev. Lett.
94
,
164502
(
2005
).
You do not currently have access to this content.