Table Of ContentSOLAR PHOTOSPHERE:
STRUCTIJRE, CONVECTION AND MAGNETIC FIELDS
INTERNATIONAL ASTRONOMICAL UNION
UNION ASTRONOMIQUE INTERNATIONALE
SOLAR PHOTOSPHERE:
STRUCTURE, CONVECTION
AND MAGNETIC FIELDS
PROCEEDINGS OF THE 138TH SYMPOSIUM OF THE
INTERNATIONAL ASTRONOMICAL UNION,
HE L DIN K I E V, U . S. S. R., MAY 1 5 - 2 0,1989
EDITED BY
J. O. S TENFLO
Institute ofA stronomy, Zurich, Switzerland
KLUWER ACADEMIC PUBLISHERS
DORDRECHT I BOSTON I LONDON
Library of Congress Cataloging in Publication Data
Solar photosphere : structure, convection, and magnetic fields:
sy.pOSiUN no. 138 held in Kiev, USSR. May 15-20. 1989 / edited by
J.O. Stenflo.
p. c •.
At head of title: International Astronomical Union, Union
astono.ique internationale.
ISBN-13:978-0-7923-0530-9 e-ISBN-13:978-94-009-1061-4
DOl: 10.1007/978-94-009-1061-4
1. Solar photosphere--Congresses. I. Stenflo. Jan Olof.
II. ·International Astronomical Union.
CB528.S65 1989
523.7'4--dc20 89-27781
ISBN-13:978-0-792 3-05 30-9
Published on behalf of
the International Astronomical Union
by
Kluwer Academic Publishers, P.O. Box /7,3300 AA Dordrecht, The Netherlands.
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TABLE OF CONTENTS
FOREWORD Xl
1. Global Properties of the Photosphere
MODELS OF THE SOLAR PHOTOSPHERE
E.H. Avrett (Invited Review) 3
THERMAL BIFURCATION OF THE OUTER PHOTOSPHERE
T.R. Ayres 23
TEMPERATURE DIAGNOSTICS OF THE UPPER PHOTOSPHERE
N.G. Shchukina, T.G. Shcherbina, R.J. Rutten 29
SOLAR OSCILLATOR STRENGTHS AS A DIAGNOSTIC TOOL
E.A. Gurtovenko, R.I. Kostik, R.J. Rutten 35
AVERAGE VARIATIONS OF PHOTOSPHERIC Fe I AND Fe II LINE
PARAMETERS AS FUNCTION OF THE MAGNETIC FILLING FACTOR
P.N. Brandt, M. Steinegger 41
II. Photospheric Fine Structure 47
HIGH RESOLUTION OBSERVATIONS OF THE PHOTOSPHERE
A.M. Title, R.A. Shine, T.D. Tarbell, K.P. Topka, G.B. Scharmer
(Invited Review) 49
PROPERTIES OF THE SOLAR GRANULATION
V.N. Karpinsky (Invited Review) 67
ANALYSIS OF THE SOLAR GRANULATION IN
THE OPACITY MINIMUM REGION
S. Koutchmy 81
FINE STRUCTURE OF PHOTOSPHERIC FACULAE
R. Muller (Invited Review) 85
BRIGHT FEATURES IN THE INTERGRANULAR REGION
Z. Suemoto, E. Hiei 9i
VI
III. Small-scale Magnetic Fields 101
EMPIRICAL MODELS OF PHOTOSPHERIC FLUX TUBES
S.K. Solanki (Invited Review) 103
EMPIRICAL PHOTOSPHERIC FLUXTUBE MODELS
FROM INVERSION OF STOKES V DATA
C.U. Keller 121
PROPERTIES OF PHOTOSPHERIC FLUXTUBES DERIVED FROM
MAGNETOGRAPH OBSERVATIONS
V.G. Lozitskij, T.T. Tsap 125
SMALL-SCALE MAGNETIC FEATURES OBSERVED IN THE PHOTOSPHERE
S.F. Martin (Invited Review) 129
HIGH-RESOLUTION OBSERVATIONS OF EMERGING MAGNETIC FIELDS
AND FLUX TUBES IN ACTIVE REGION PHOTOSPHERE
T. Tarbell, S. Ferguson, Z. Frank, R. Shine, A. Title, K. Topka,
G. Scharmer 147
SMALL SCALE MOTIONS OVER CONCENTRATED MAGNETIC
FIELD REGIONS OF THE QUIET SUN
H.C. Dara, C.E. Alissandrakis, S. Koutchmy 153
SMALL SCALE MAGNETIC STRUCTURES IN ACTIVE CENTERS
A. Dollfus 157
THEORETICAL ASPECTS OF SMALL-SCALE
PHOTOSPHERIC MAGNETIC FIELDS
M. Schussler (Invited Review) 161
MODEL CALCULATIONS OF THE PHOTOSPHERIC LAYERS OF
SOLAR MAGNETIC FLUXTUBES
O. Steiner, J .0. Stenflo 181
WAVE HEATING IN MAGNETIC FLUX TUBES
W. Kalkofen 185
IV. Magnetohydrodynamics of the Photosphere 189
SOLAR MAGNETOCONVECTION
A. Nordlund, R.F. Stein (Invited Review) 191
RESULTS FROM 2-D NUMERICAL SIMULATIONS OF SOLAR GRANULES
M. Steffen, D. Gigas, H. Holweger, A. Kruss, H.-G. Ludwig 213
WAVES AND OSCILLATIONS IN THE NON-MAGNETIC PHOTOSPHERE
F.-L. Deubner (Invited Review) 217
WAVES AND OSCILLATIONS IN MAGNETIC FLUXTUBES
M.P. Ryutova (Invited Review) 229
ON THE 5-MINUTE PHOTOSPHERIC OSCILLATION AND ITS MODELING
C. Marmolino, G. Severino 251
vii
CLASSIFICATION OF MAGNETOATMOSPHERIC MODES IN SUNSPOT
UMBRAE
S.S. Hasan, Y. Sobouti 255
THE OBSERVATIONAL SIGNATURE OF FLUX TUBE WAVES AND AN
UPPER LIMIT ON THE ENERGY FLUX TRANSPORTED BY THEM
S.K. Solanki, B. Roberts 259
MAGNETIC FLUX CONCENTRATION BY SIPHON FLOWS IN
ISOLATED MAGNETIC FLUX TUBES
J.H. Thomas, B. Montesinos 263
ELECTRIC CURRENTS IN THE ATMOSPHERE OF THE SUN
V.I. Abramenko, S.I. Gopasyuk, M.B. Ogir 267
GENERATION OF MAGNETIC FIELDS AND ELECTRIC CURRENTS
IN THE SOLAR PHOTOSPHERE
J.C. Henoux, B.V. Somov 273
V. Large-scale Structure and Dynamics 279
GLOBAL EVOLUTION OF PHOTOSPHERIC MAGNETIC FIELDS
V.I. Makarov, K.R. Sivaraman (Invited Review) 281
ORIGIN OF THE SUN'S DIFFERENTIAL ROTATION
L.L. Kichatinov (Invited Review) 297
THE SUN'S ROTATION RATE AS INFERRED
FROM MAGNETIC FIELD DATA
J.O. Stenflo 309
GENERATORS OF SOLAR DIFFERENTIAL ROTATION
AND IMPLICATIONS OF HELIOSEISMOLOGY
G. Rudiger, I. Thominen 315
ASYMMETRY OF EMERGING FLUX LOOPS CAUSED BY RADIAL
DIFFERENTIAL ROTATION
M. Marik, K. Petrovay 321
CONVECTION AND ITS STABILITY IN THE EQUATORIAL REGIONS
OF THE CONVECTION ZONE
A.V. Klyachkin 325
INVERSE CASCADE IN HYDRODYNAMIC TURBULENCE AND ITS ROLE
IN SOLAR GRANULATION
V. Krishan 329
GENERATION OF TORSIONAL OSCILLATIONS IN THE SUN
Y.V. Vandakurov (Invited Review) 333
viii
VI. Generation of Solar Magnetic Fields 341
ORDER AND CHAOS IN THE SOLAR CYCLE
A.A. Ruzmaikin (Invited Review) 343
SYMMETRY BREAKING IN THE SOLAR DYNAMO:
NONLINEAR SOLUTIONS
R.L. Jennings, N.O. Weiss 355
EXCITATION OF DYNAMO MODES
P. Hoyng (Invited Review) 359
STUDY OF SUN'S "HYDROMAGNETIC" OSCILLATIONS USING
SUNSPOT DATA
M.H. Gokhale, J. Javaraiah, K.M. Hiremath 375
VARIATION OF EVEN AND ODD PARITY IN THE SOLAR DYNAMO
A. Brandenburg, R. Meinel, D. Moss, I. Tuominen 379
SELF-ORDERING OF PHOTOSPHERIC MAGNETIC FIELDS
J.K. Lawrence 383
TORSIONAL OSCILLATIONS AND THE SOLAR DYNAMO REGIME
L Tuominen, G. Riidiger, A. Brandenburg 387
LARGE-SCALE INTERNAL MAGNETIC FIELD OF THE SUN
A.E. Dudorov, V.N. Krivodubskij, A.A. Ruzmaikin, T.V. Ruzmaikina 391
VII. Convection and Magnetic Fields in Solar-type Stars 395
OBSERVING, MODELING, AND UNDERSTANDING STELLAR
GRANULATION
D. Dravins (Invited Review) 397
A MODEL FOR STELLAR CONVECTION AND
SPECTRAL LINE ASYMMETRIES
H.M. Antia 417
COMPARATIVE ANALYSIS OF PHYSICAL CONDITIONS IN
THE SOLAR AND PROCYON ATMOSPHERES
LN. Atroshchenko, A.S. Gadun, R.I. Kostik, K.N. Pikalov 421
MAGNETIC FIELDS ON SOLAR-LIKE STARS: THE FIRST DECADE
S.H. Saar (Invited Review) 427
RESULTS OF COORDINATED MULTIWAVELENGTH OBSERVATIONS
OF SOLAR-TYPE STARS
J. Huovelin, S.H. Saar 443
NONLINEAR DYNAMO MODES AND TIMESCALES
OF STELLAR ACTIVITY
G. Belvedere, M.R.E. Proctor 447
DOES A COMMON DYNAMO MECHANISM EXIST FOR
LOWER MAIN SEQUENCE STARS ?
R.B. Teplitskaya, V.G. Skochilov 455
ix
VIII. Future Directions 461
GROUND BASED AND SPACE FUTURE PROSPECTS IN
SOLAR INTERFEROMETRY APPLIED TO THE PHOTOSPHERE
J.P. Rozelot 463
NEW OBSERVATIONAL ASPECTS
O. Engvold (Invited Review) 469
OUTSTANDING THEORETICAL PROBLEMS
C.J. Durrant (Invited Review) 489
SUMMARY LECTURE
R.J. Rutten (Invited Summary) 501
LIST 0F POSTER PAPERS 517
LETTER TO G. BUSH AND M. GORBACHEV 529
LIST OF PARTICIPANTS 531
AUTHOR INDEX 537
SUBJECT INDEX 541
FOREWORD
Solar and stellar photospheres constitute the layers most accessible to observations, forming
the interface between the interior and the outside of the stars. The solar atmosphere is a
rich physics laboratory, in which the whole spectrum of radiative, dynamical, and magnetic
processes that tranfer energy into space can be observed. As the fundamental processes take
place on very small spatial scales, we need high· resolution observations to explore them. On
the other hand the small-scale processes act together to form global properties of the sun,
which have their origins in the solar interior. The rapid advances in observational techniques
and theoreticallllodelling over the past decade made it very timely to bring together scientists
from east and west to the first lAU Symposium on this topic.
The physics of the photosphere involves complicated interactions between magnetic fields,
convection, waves, and radiation. During the past decade our understanding of these gener
ally small-scale structures and processes has been dramatically advanced. New instrumen
tations, on ground and in space, have given us new means to study the granular convection.
Diagnostic methods in Stokes polarimetry have allowed us to go beyond the limitations of
spatial resolution to explore the structure and dynamics of the subarcsec magnetic struc
tures. Extensive numerical simulations of the interaction between convection and magnetic
fields using powerful supercomputers are providing deepened physical insight. Granulation,
magnetic fields, and dynamo processes are being explored in the photospheres of other stars,
guided by our improved understanding of the solar photosphere.
Not only are we beginning to understand the relation between the small-scale processes
and the large-scale structures, but it is also becoming increasingly clear that the sun cannot
be properly sepa.rated into a "quiet" and an "active" part. The sun (and other stars for
that matter) should rather be looked upon as a complicated but indivisible organism, whose
numerous and interrela.ted properties exhibit both cyclic and secular variations, on short as
well as long time scales. The symposium has considered the photosphere of the sun within
this broader context, as an integral part of a larger system.
The symposium took place in Kiev, USSR, May 15-20, 1989, and was attended by more
than 200 participants from 24 countries. The presentations included 20 invited review papers,
37 orally contributed papers, and more than 100 poster papers. The meeting was sponsored
by IAU Commission 12 and cosponsored by Commissions 10 and 36. We are grateful for the
travel support provided by the IAU and by the Academy of Sciences of the Ukrainian SSR.
The Scientific Organizing Conmlittee consisted of V. Bumba, C.J. Durrant, D.F. Gray,
E.A. Gurtovenko, R. Howard, V.N. Karpinsky, R. Muller, A. Nordlund, R.W. Noyes, R.J.
Rutten, H.C. Spruit, J.O. Stenflo (Chairman), H. Yoshimura, and C. Zwaan. I am grateful
to the SOC members for their support. In particular I am indebted to Rob Rutten, who was
one of the originators of the idea of having this type of a symposium in Kiev, and who has
provided an important link between SOC and the organizers in Kiev.
xi
