[9] As we are interested in isolating the solar cycle extreme phases in the GCR intensity modulation and as this solar cycle is very similar to that in RZ, we looked at the known SC phases classifications for the photospheric (and nearby) activity and found that of Ju. I. Vitinsky, V. G. Kuklin, and V. N. Obridko (VKO) [Obridko and Shelting, 1992, 2003; Vitinsky et al., 1986] to be the best as an initial point.
[10] First, let us describe some terms we widely use. The development of the solar cycle can be described as the interaction of the toroidal ( T, Bj ) and poloidal ( P, Br ) subphotospheric magnetic fields and the alternating transition of the energy from T to P fields and back. Accordingly at the photosphere one can see the phenomena of the T branch of solar activity (sunspots with the ordered toroidal magnetic fields and other objects (active regions) linked to them) and those of the P branch (much weaker but large-scale poloidal magnetic fields at the polar latitudes and between the active regions, also polar faculae, etc).
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Figure 2 |
[11] In Figure 2 the Carrington rotation-averaged sunspot area (available at http://science.nasa.gov/ssl/PAD/SOLAR/greenwch.htm) (Figure 2a) and latitude range occupied by the spots (Figure 2b) are shown for each hemisphere (the solid curves for Northern and the dotted ones for Southern Hemispheres) for 1980-1999, the polarity of the sunspots (the sign of Bj ) being also reflected by the thickness of the lines. The line-of-sight component of the north and south polar photospheric magnetic field as seen from the Earth (available at http://sun.stanford.edu/ wso/) is depicted in Figure 2c. Also shown by the shading are the periods isolated by Obridko and Shelting [2003] as the extreme phases.
[12] Without going into details, we can give the following brief
description of the solar cycle main phases (according to
Vitinsky et al. [1986]
but using our ( T and
P ) terms): (1) min,
tDm < t
[13] The boundaries of the main phases
( tmA, tAM, tMD,
tDm ),
introduced by
Vitinsky et al. [1986]
as the reference points of the solar
cycle) are determined for the last solar cycles by
Obridko and Shelting [2003]
from the careful study of the sunspots, polar faculae, filaments
etc. and widely using the data (available at
http://sun.stanford.edu/ wso/) on the large-scale magnetic fields both
on the photosphere and at the base of the heliosphere. It is this
particular interest in the very important for the heliosphere solar
P phenomena, that determined our choice of the above classification as
the best initial point in our search for the SC phases in the GCR
intensity modulation.
Citation: 2004), Main phases of the solar cycle in the galactic cosmic ray intensity, Int. J. Geomagn. Aeron., 5, GI2004, doi:10.1029/2004GI000070.
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