Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Helioseismic Signature of Chromospheric Downflows in Acoustic
  Travel-Time Measurements from Hinode   We report on a signature of chromospheric downflows in two emerging-flux
regions detected by time-distance helioseismology analysis. We use both
chromospheric intensity oscillation data in the Ca II H line and photospheric
Dopplergrams in the Fe I 557.6nm line obtained by Hinode/SOT for our analyses.
By cross-correlating the Ca II oscillation signals, we have detected a
travel-time anomaly in the plage regions; outward travel times are shorter than
inward travel times by 0.5-1 minute. However, such an anomaly is absent in the
Fe I data. These results can be interpreted as evidence of downflows in the
lower chromosphere. The downflow speed is estimated to be below 10 km/s. This
result demonstrates a new possibility of studying chromospheric flows by
time-distance analysis.

9
The categories of this paper are: nlin
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
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The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph