Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Formation and evolution of coronal holes during the rising phase of
  cycle 23   Regularities of formation of coronal holes (CH) at the rising phase of cycle
23 are investigated. The period from 01.01.1997 to 01.03.2000 (Carrington
rotations (CRs) 1918-2059) is considered in detail. The evolution of the global
magnetic field (GMF) of the Sun from the zonal to the sectorial structure is
analyzed. It is shown that the zonal structure is quasi-stable. The sum of
zonal harmonics dominated up to CR 1941, although a stable four-sector
structure of GMF was formed in 1932. In CRs 1941-1950 the contribution of the
zonal and sectorial components becomes approximately equal and from CR 1950 the
sectorial structure of GMF was dominated. Sectorial structure of GMF undergoing
sharp changes from four-sector, at the beginning of growth of the sectorial
harmonics (CR 1926), to the two-sector structure, then back to four-sector and
then again to the two-sector structure. CHs clearly trace all evolutionary
changes in the GMF. The structure of the polarity of the GMF uniquely
determines the zones of photospheric magnetic fields where the CHs are formed.

7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th