Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solar activity around AD 775 from aurorae and radiocarbon   A large variation in 14 C around AD 775 has been considered to be caused by
one or more solar super-flares within one year. We critically review all known
aurora reports from Europe as well as the Near, Middle, and Far East from AD
731 to 825 and find 39 likely true aurorae plus four more potential aurorae and
24 other reports about halos, meteors, thunderstorms etc., which were
previously misinterpreted as aurorae or misdated; we assign probabilities for
all events according to five aurora criteria. We find very likely true aurorae
in AD 743, 745, 762, 765, 772, 773, 793, 796, 807, and 817. There were two
aurorae in the early 770s observed near Amida (now Diyarbakir in Turkey near
the Turkish-Syrian border), which were not only red, but also green-yellow -
being at a relatively low geo-magnetic latidude, they indicate a relatively
strong solar storm. However, it cannot be argued that those aurorae
(geo-magnetical latitude 43 to 50 deg, considering five different
reconstructions of the geo-magnetic pole) could be connected to one or more
solar super-flares causing the 14 C increase around AD 775: There are several
reports about low- to mid-latitude aurorae at 32 to 44 deg geo-magnetical
latitude in China and Iraq; some of them were likely observed
(quasi-)simultaneously in two of three areas (Europe, Byzantium/Arabia, East
Asia), one lasted several nights, and some indicate a particulary strong
geo-magnetic storm (red colour and dynamics), namely in AD 745, 762, 793, 807,
and 817 - always without 14 C peaks. We use 39 likely true aurorae as well as
historic reports about sunspots together with the radiocarbon content from tree
rings to reconstruct solar activity: From about AD 733 to 823, we see at least
nine Schwabe cycles ...

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The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph
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The categories of this paper are: hep-th
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The categories of this paper are: gr-qc
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The categories of this paper are: physics
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The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: supr-con
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The categories of this paper are: mtrl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph