Astronomy and Astrophysics – Astronomy
Scientific paper
May 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21640715w&link_type=abstract
American Astronomical Society, AAS Meeting #216, #407.15; Bulletin of the American Astronomical Society, Vol. 41, p.862
Astronomy and Astrophysics
Astronomy
Scientific paper
Quasi-periodic propagating intensity disturbances were found by SOHO/EIT and TRACE imaging observations in fanlike coronal loops 10 year ago. The 3 min and 5 min oscillations have been interpreted as propagating slow magnetoacoustic waves which originate from the photospheric p-mode oscillations due to the wave leakage. However, some cases show oscillations with periodicities of more than 10 min, which are hard to explain by wave leakage, and so were argued in some studies that they may be periodic flows. In this presentation, we report the first observation of multiple-periodic (12 and 25 min) propagating disturbances along a fan-like coronal structure simultaneously detected in both intensity and Doppler shift in the Fe XII line with EIS onboard Hinode. We measured Doppler shift amplitude of 1-2 km/s, relative intensity amplitude of (3-5)% and the apparent propagation speed of 100-120 km/s. The amplitude relationship between intensity and Doppler shift oscillations provides convincing evidence that these propagating features are a manifestation of slow magnetoacoustic waves but not flows. The feature of symmetric line profiles also confirms that the measured small Doppler-shift amplitudes are not due to the line wing enhancement caused by high-speed flows. A new application of coronal seismology is provided based on these observations, with which we determine the inclination angle of the magnetic field and the temperature of a coronal loop. We will also show the result of multi-temperature line analysis to explore the temperature-dependent behavior of this phenomenon.
Davila Jose Manuel
Ofman Leon
Wang Tongjiang
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