TY - JOUR
T1 - Helioseismic signature of chromospheric downflows in acoustic travel-time measurements from Hinode
AU - Nagashima, Kaori
AU - Sekii, Takashi
AU - Kosovichev, Alexander G.
AU - Zhao, Junwei
AU - Tarbell, Theodore D.
N1 - Funding Information:
We thank Tetsuya Magara for helpful comments. Hinode is a Japanese mission developed and launched by ISAS/JAXA, with NAOJ as domestic partner and NASA and STFC (UK) as international partners. It is operated by these agencies in co-operation with ESA and NSC (Norway). This work was carried out at the NAOJ Hinode Science Center, which is supported by the Grant-in-Aid for Creative Scientific Research “The Basic Study of Space Weather Prediction” from MEXT, Japan (Head Investigator: K. Shibata), generous donations from Sun Microsystems, and NAOJ internal funding. K. Nagashima is supported by the Research Fellowship from the Japan Society for the Promotion of Science for Young Scientists.
Funding Information:
We thank Tetsuya Magara for helpful comments. Hinode is a Japanese mission developed and launched by ISAS/JAXA, with NAOJ as domestic partner and NASA and STFC (UK) as international partners. It is operated by these agencies in co-operation with ESA and NSC (Norway). This work was carried out at the NAOJ Hinode Science Center, which is supported by the Grant-in-Aid for Creative Scientific Research “The Basic Study of Space Weather Prediction” from MEXT, Japan (Head Investigator: K. Shibata), generous donations from Sun Microsystems, and NAOJ internal funding. K. Nagashima is supported by the Research Fellowship from the Japan Society for the Promotion of Science for Young Scientists. Facilities: Hinode (SOT)
PY - 2009
Y1 - 2009
N2 - 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 557.6 nm 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 -1. This result demonstrates a new possibility of studying chromospheric flows by time-distance analysis.
AB - 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 557.6 nm 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 -1. This result demonstrates a new possibility of studying chromospheric flows by time-distance analysis.
KW - Sun: chromosphere
KW - Sun: faculae, plages
KW - Sun: helioseismology
UR - http://www.scopus.com/inward/record.url?scp=64849111054&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=64849111054&partnerID=8YFLogxK
U2 - 10.1088/0004-637X/694/2/L115
DO - 10.1088/0004-637X/694/2/L115
M3 - Article
AN - SCOPUS:64849111054
SN - 0004-637X
VL - 694
SP - L115-L119
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
ER -