PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
1) diffusion of the filed line footpoints and 2) diffusion due to reconnection of open field lines with closed
loops. They demonstrated that the rate of emergence of flux on the photosphere can control the magnitude of
meridional flow. But, they found that the effect of diffusion due to magnetic reconnection is significant for
the case of structured magnetic configuration (solar minimum conditions) and it small for the case of
unstructured magnetic configuration (solar maximum conditions).
Abramenko, Fisk, Yurchishin (2006) found that the coronal hole which forms after the polar magnetic field
reversals (2002-2003) displays the local minimum for the rate of emergence of new magnetic flux. Dipole
emergence rate in quiet sun exceeds twice that in Coronal holes.
However, Hagenaar, Schrijver, and DeRosa (2008) have found that the emergence frequency of ephemeral
regions does not depend on the presence of coronal holes. Instead,
the frequency of ephemeral regions is
found to depend on the degree of flux imbalance in the photosphere. This explains the observations by
Abramenko, Fisk, & Yurchyshyn (2006) that fewer ephemeral regions emerge in quiet Sun inside coronal
holes, than outside coronal holes.
The surface-diffusion or transport models explain the polar magnetic field reversals as a result of turbulent
diffusion,
meridional circulation and differential rotation (e.g. Wang, Sheeley and Nash, 1991; Schrijver
and Title 2001). Schrijver, De Rosa, Title (2002) also point out that the transport process leads to a transport
of closed connections from equator to pole even as open solar flux is transported from the high latitudes to
the equator. Fox, McIntosh and Wilson (1997) described the evolution of the large-scale fields and their
association with polar coronal holes. Their question was whether the polar fields resulted from the local
polar dynamo or not. There is no a certain answer to this question. But, Durrant, Turner and Wilson (2002)
have observed that high-latitude flux emergence can affect the evolution of individual high-latitude plumes,
but this flux does not seriously affect the whole reversal times of the polar magnetic field. However, the
polar magnetic elements involve in the supergranular motion, solar rotation and reflect the subsurface
gradient of angular velocity (Benevolenskaya, 2007).
Conclusion
The current and future high- (low-) resolution solar observations
enable to investigate physical processes at
the all levels on the Sun (convection zone, photosphe re,
chromosphere, and corona), simultaneously. SOHO
and others missions show how our Sun is variable. In this paper I reviewed the present results with focus on
the solar cycle studies. Because of the next solar space laboratory, Solar Dynamics Laboratory (SDO), is
coming to replace SOHO with a purpose to understand the nature of the solar cycle.
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