Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A possible case of sporadic aurora observed at Rio de Janeiro   Being footprints of major magnetic storms and hence major solar eruptions,
mid- to low-latitude aurorae have been one of the pathways to understand
solar-terrestrial environments. However, it has been reported that aurorae are
also occasionally observed at low latitudes under low or even quiet magnetic
conditions. Such phenomena are known as "sporadic aurorae". We report on a
historical event observed by a scientist of the Brazilian Empire in Rio de
Janeiro on 15 February 1875. We analyze this event on the basis of its
spectroscopic observations, along with its visual structure and coloration, to
suggest this event was a possible case of sporadic aurorae. Given the absence
of worldwide aurora observations on that day as a consequence of low magnetic
activity recorded on the days preceding the observation, in addition to a
detailed description, the event observed can most likely be classified as a
sporadic aurora. We discuss the geographic and magnetic conditions of that
event. Thus, we add a possible case of sporadic aurora in the South American
sector.

19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math