Abstract
The solar dynamo problem is the question of how the cyclic variation in the solar magnetic field is maintained. One of the important processes is the transport of magnetic flux by surface convection. To reveal this process, the dependence of the squared displacement of magnetic flux concentrations on the elapsed time is investigated in this paper via a feature-recognition technique and a continual five-day magnetogram. This represents the longest time scale over which a satellite observation has ever been performed for this problem. The dependence is found to follow a power law and differ significantly from that of diffusion transport. Furthermore, there is a change in the behavior at a spatial scale of 103.8 km. A super-diffusion behavior with an index of 1.4 is found at smaller scales, while changing to a sub-diffusion behavior with an index of 0.6 on larger ones. We interpret this difference in the transport regime as coming from the network-flow pattern.
Highlights
Magnetic fields on the solar surface are a fundamental driver of solar activity, with its effects on the Sun-Earth system
Sunspots appear near 30° latitude with a certain lean angle from the longitudinal direction and are dispersed within one or two months; in line-of-sight observations of the photospheric magnetic field, the Sun reveals a patchy structure at small scales ( 103 km), called magnetic flux concentration
Iida: Tracking of magnetic concentrations and surface magnetic transport about the form of the global transport, it is only a necessary condition. We investigate this relationship in the transport of magnetic flux concentration on the solar surface
Summary
Magnetic fields on the solar surface are a fundamental driver of solar activity, with its effects on the Sun-Earth system. It has a spatial size of ~1.6 · 104 km, and a typical horizontal speed of 300–500 m sÀ1 (see Rieutord & Rincon 2010 and references therein) Because these surface convections are much faster than the meridional flow, the magnetic flux concentration rapidly prevails during transport to the pole. Wang et al (1989) investigated this model by using numerical simulation They calculated the time evolution of the surface magnetic field by changing the meridional flow speed and the diffusion coefficient for smaller-scale convections. The analysis of huge amounts of events is needed for investigating solar surface transport This is because the magnetic elements are much smaller than the global scale, and the statistical character is crucial; feature-recognition techniques are plausible solutions to this difficulty.
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