Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solar cycle variation in solar irradiance   The correlation between solar irradiance and the 11-year solar activity cycle
is evident in the body of measurements made from space, which extend over the
past four decades. Models relating variation in solar irradiance to
photospheric magnetism have made significant progress in explaining most of the
apparent trends in these observations. There are, however, persistent
discrepancies between different measurements and models in terms of the
absolute radiometry, secular variation and the spectral dependence of the solar
cycle variability. We present an overview of solar irradiance measurements and
models, and discuss the key challenges in reconciling the divergence between
the two.

18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int