THE ORIGIN OF INTRANETWORK FIELDS - A SMALL-SCALE SOLAR DYNAMO

被引:0
作者
PETROVAY, K
SZAKALY, G
机构
来源
ASTRONOMY & ASTROPHYSICS | 1993年 / 274卷 / 02期
关键词
MHD; SUN; MAGNETIC FIELD; PHOTOSPHERE;
D O I
暂无
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The intranetwork magnetic fields observed on the solar surface consist of flux tubes that are thin enough for their motion to be fully determined by the drag forces exerted on them by turbulent motions. The equations governing such a passive transport of the mean magnetic flux density [B] and of the unsigned flux density [Absolute value of B] in the convective zone of the Sun (assuming a one-dimensional geometry) are derived and discussed: turbulent diffusion and turbulent pumping are found to be the main transport effects. As the timescale of the transpon is much shorter than the solar cycle, the flux density at any instant is given by an equilibrium solution of the transport equations. These solutions are computed and presented. The main conclusions are the following. 1. If no source terms are included in its transport equation, the mean flux density increases by 4 orders of magnitude from the surface to the bottom of the convective zone, showing that turbulent pumping is one of the main mechanisms confining the global dynamo to the bottom of the convective zone. 2. The observed emergence rate of magnetic flux in active regions is not sufficient to sustain the observed mean magnetic fields which must therefore be sustained and continuously refreshed on a timescale of approximately 20 days by the emergence of statistically aligned smaller bipolar flux concentrations (intranetwork fields or small ephemeral regions) from below. 3. The observed unsigned flux density of intranetwork fields is only consistent with the model if a small-scale dynamo mechanism is operating in the convective zone continuously producing unsigned flux; no other likely sources of flux of the correct order of magnitude are known. 4. Modelling the source term corresponding to the small-scale dynamo on the basis of numerical simulation results, the hidden magnetic flux density is predicted to lie between about 2.5 and 7.5 mT. This prediction may be tested by observations in the not too distant future.
引用
收藏
页码:543 / 554
页数:12
相关论文
共 50 条
[21]   IS THE SMALL-SCALE MAGNETIC FIELD CORRELATED WITH THE DYNAMO CYCLE? [J].
Karak, Bidya Binay ;
Brandenburg, Axel .
ASTROPHYSICAL JOURNAL, 2016, 816 (01)
[22]   A unified large/small-scale dynamo in helical turbulence [J].
Bhat, Pallavi ;
Subramanian, Kandaswamy ;
Brandenburg, Axel .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2016, 461 (01) :240-247
[23]   Solar small-scale magnetoconvection [J].
Stein, R. F. ;
Nordlund, A. .
ASTROPHYSICAL JOURNAL, 2006, 642 (02) :1246-1255
[24]   Suppression of small-scale dynamo in time-irreversible turbulence [J].
Kopyev, A., V ;
Il'yn, A. S. ;
Sirota, V. A. ;
Zybin, K. P. .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2024, 527 (01) :1055-1061
[25]   Small-scale dynamo in cool II. The effect of metallicity [J].
Witzke, V. ;
Duehnen, H. B. ;
Shapiro, A. I. ;
Przybylski, D. ;
Bhatia, T. S. ;
Cameron, R. ;
Solanki, S. K. .
ASTRONOMY & ASTROPHYSICS, 2023, 669
[26]   On the diagnostics of solar small scale magnetic fields [J].
Stodilka, M. I. .
ADVANCES IN SPACE RESEARCH, 2015, 55 (03) :891-896
[27]   THE SMALL-SCALE VELOCITY-FIELD IN THE SOLAR PHOTOSPHERE [J].
KOMM, R ;
MATTIG, W ;
NESIS, A .
ASTRONOMY & ASTROPHYSICS, 1991, 243 (01) :251-262
[28]   The onset of a small-scale turbulent dynamo at low magnetic Prandtl numbers [J].
Schekochihin, AA ;
Haugen, NEL ;
Brandenburg, A ;
Cowley, SC ;
Maron, JL ;
McWilliams, JC .
ASTROPHYSICAL JOURNAL, 2005, 625 (02) :L115-L118
[29]   Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields [J].
Chitta, L. P. ;
Peter, H. ;
Solanki, S. K. ;
Barthol, P. ;
Gandorfer, A. ;
Gizon, L. ;
Hirzberger, J. ;
Riethmueller, T. L. ;
van Noort, M. ;
Blanco Rodriguez, J. ;
Del Toro Iniesta, J. C. ;
Orozco Suarez, D. ;
Schmidt, W. ;
Pillet, V. Martinez ;
Knoelker, M. .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 2017, 229 (01)
[30]   Exploring the Small-scale Magnetic Fields of the Solar Analog KIC 8006161 Using Asteroseismology [J].
Lin, Guifang ;
Li, Yan ;
Su, Jie ;
Wu, Tao ;
Wang, Yuetong .
ASTROPHYSICAL JOURNAL, 2024, 976 (01)