DDGAW2004:
The Astrophysical Journal, 601:1136-1151, 2004 February 1
,
, and

The Astrophysical Journal, 591:1248-1256, 2003 July 10
Copyright is not claimed for this article. Printed in U.S.A.
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and
Code 7672, E.
O.
Hulburt Center for Space Research, US Naval Research Laboratory,
Washington, DC 20375-5352; ywang@yucca.nrl.navy.mil
, sheeley@spruce.nrl.navy.mil
Received 2003 March 5; accepted 2003 March 20
ABSTRACT
We use a flux transport model to simulate the evolution of the Sun's magnetic dipole moment, polar fields, and open flux under Maunder minimum conditions.
Even when the rate of active region emergence is taken to be a factor of 30 smaller than in recent solar cycles, regular polarity oscillations of the axial dipole and polar fields can be maintained if the speed of the poleward surface flow is reduced from 20 to 10 m s -1 and the source flux emerges at very low latitudes ( 10°). The axial dipole is then found to have an amplitude of the order of 0.5
G, as compared with 4 G during solar cycle 21. The strength of the radial interplanetary field component at Earth is estimated to be in the range 0.3 0.7
nT, about a factor of 7 lower than contemporary values. We discuss the implications of these weak fields for our understanding of geomagnetic activity and cosmic-ray modulation during the Maunder minimum.
The Astrophysical Journal, 585:553-565, 2003 March 1
© 2003. The American Astronomical Society. All rights reserved. Printed in U.S.A.
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Astronomy Department, Yale University, P.
O.
Box 208101, New Haven, CT 06520-8101; basu@astro.yale.edu
and

Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India; antia@tifr.res.in
Received 2002 June 24; accepted 2002 November 8
ABSTRACT
Data obtained by the GONG and MDI instruments over the last 7 years are used to study how solar dynamics both rotation and other large scale flows has changed with time.
In addition to the well-known phenomenon of bands of faster and slower rotation moving toward the equator and pole, we find that the zonal flow pattern rises upward with time.
Like the zonal flows, the meridional flows also show distinct solar changes. In particular, the antisymmetric component of activity related the meridional flow shows a decrease in speed with activity. We do not see any significant temporal variations in the dynamics of the tachocline region where the solar dynamo is believed to be operating.
Subject headings: Sun: helioseismology Sun: interior Sun: oscillations Sun: rotation
The Astrophysical Journal, 582:1190-1205, 2003 January 10
© 2003. The American Astronomical Society. All rights reserved. Printed in U.S.A.
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Centre for Stellar and Planetary Astrophysics, School of Mathematical Sciences, Monash
University, P.O.
Box 28M, Victoria 3800, Australia; paul.cally@sci.monash.edu.au
and
and
High Altitude Observatory, National Center for Atmospheric Research,
1
P.O.
Box 3000,
Boulder, CO 80307-3000; dikpati@hao.ucar.edu
, gilman@hao.ucar.edu
Received 2002 March 25; accepted 2002 September 17
ABSTRACT
Building on Cally's nonlinear model of two-dimensional MHD tachocline instability, we further explore the evolution of a wide variety of toroidal field profiles due to this instability. Cally showed in a recent study that an initially broad toroidal field opens up into a "clamshell" pattern because of nonlinear evolution of MHD tachocline instability.
Various other toroidal field profiles single toroidal bands, double bands, and mixed profiles with a band in addition to broad profiles may also occur in the Sun during various phases of the solar cycle. Detailed study of the evolution of banded profiles shows

no occurrence of clamshell instability, but the bands commonly tip relative to the axis of rotation.
The higher the latitude location of the band, the more it tips.
Extreme tipping results when the band is at 60° latitude or higher the magnetic ring hangs from the pole on one side of the Sun.
For bands of 10° latitude width at sunspot latitudes ( 40°), the band tip is within ±10° about the mean latitude of the band. This tipping could either enhance or reduce the observed tilt in bipolar active regions. Double bands, or profiles consisting of a band and a broad profile, may exist at find that double-band systems with certain phases of the solar cycle. We two oppositely directed bands separated widely (>15°) in latitude, as well as two close bands of same polarities, do not interact in the same hemisphere the higher latitude band tips, while the lower latitude band hardly responds.
A significant interaction between two individual bands in one hemisphere takes place only when the band separation is 15° and the bands are oppositely directed, which is a nonsolar case. In this case, the band system either tips or forms the clamshell pattern depending on the dominant mode symmetry. We also show that a mixed profile with oppositely directed narrow fields close to the equator in addition to the broad fields evolve in such a way as to oppose the reconnection of the broad fields across the equator, and thus inhibiting the clamshell formation, at least at certain phases of the solar cycle.
Finally, we note that the tipping and clamshell instabilities strongly inhibit differential rotation.
Subject headings: instabilities MHD Sun: activity Sun: magnetic fields
1 The National Center for Atmospheric Research is sponsored by the National Science Foundation.
The
Astrophysical Journal, 580:1188-1196, 2002 December 1
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,
, and
E.
O.
Hulburt Center for Space Research, Code 7670, Naval Research Laboratory,
Washington, DC 20375-5352; ywang@yucca.nrl.navy.mil
, sheeley@spruce.nrl.navy.mil
, lean@demeter.nrl.navy.mil
Received 2002 June 14; accepted 2002 July 31
ABSTRACT
We simulate the evolution of the Sun's large-scale magnetic field during solar cycle 21, including the effect of surface transport processes and active region emergence. As an important new constraint on the model, we have scaled our source fluxes upward to be consistent with the average measured strength of the interplanetary magnetic field (IMF).

By adopting a poleward bulk flow of amplitude 20 25 m s
-1
together with a supergranular diffusion rate of 500 km
2
s
-1
, we are then able to match the observed variation of the Sun's polar fields and open magnetic flux. The high meridional flow speeds, peaking at low latitudes, prevent the buildup of an overly strong axisymmetric dipole component at sunspot minimum, while accounting for the giant poleward surges of flux and accompanying polar field fluctuations observed near sunspot maximum. The present simulations also reproduce the large peak in the equatorial dipole and IMF strength recorded in 1982.
Subject headings: interplanetary medium solar-terrestrial relations Sun: activity
Sun: corona Sun: magnetic fields Sun: photosphere
Article 6:
Title:
Authors:
Transport of Magnetic Fields on the Sun.
Leighton, Robert B.
Journal: Astrophysical Journal, vol. 140, p.1547 ( ApJ Homepage )
Publication Date: 11/1964
Origin: ADS
Bibliographic Code: 1964ApJ...140.1547L