Helicity as the ultimate test to the surface dynamo problem.
Alexei A. Pevtsov (National Solar Observatory, USA)
Dana W. Longcope (Montana State University, USA)
It has become widely accepted that large-scale magnetic structures on
the Sun, such as active regions, are the product of a dynamo of
periodicity approximately 22 years situated at or near the base of the
convection zone. There has been speculation that the intermixed,
small-scale photospheric magnetic field is generated by a second
dynamo operating at or near the solar surface. Numerical simulations
have shown that such dynamo could work, although it would not be as
effective in generating flux as the more conventional deep-seated
dynamo. Since they are driven by flows of different sizes operating
on different time scales, the magnetic fields generated by these two
dynamos should be quantiatively different. In particular, there are
well-studied helical trends in the large-scale magnetic which could
be imprinted on them by the deep, slow flows of the dynamo which
generates them; these helical trends would be absent from a field
generated by a surface dynamo. We propose that observations of
magnetic/current helicity at very small scales can be used to
establish the role of the second, surface dynamo on the Sun.
Correspondence
Pevtsov, Alexei, Dr., National Solar Observatory
presentation
oral