Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Principal component analysis of geomagnetic activity: New information on
  solar wind   We use the principal component analysis (PCA) to study geomagnetic activity
at annual resolution using a network of 26 magnetic stations in 1966-2015, and
an extended network of 40 stations in 1980-2015. The first principal component
(PC1) describes the long-term evolution of global geomagnetic activity, and has
an excellent correlation with indices like the Kp/Ap index. The two networks
give identical results for PC1. The second principal component (PC2) is highly
correlated with the annual percentage of high-speed streams (HSS). The extended
network has a slightly higher sensitivity to HSSs. We verify the non-trivial
latitudinal distribution of the second empirical orthogonal function (EOF2). We
find that the amplitude of the 22-year variation of geomagnetic activity has a
closely similar latitudinal distribution as EOF2. This verifies that the
22-year variation of geomagnetic activity is related to HSSs. The most likely
cause is the Russell-McPherron mechanism.

17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin