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Paper: Spectroscopic Observations of Continuous Outflows and Propagating Waves in Active Region NOAA 10942 with Hinode/EIS
Volume: 455, 4th Hinode Science Meeting: Unsolved Problems and Recent Insights
Page: 219
Authors: Nishizuka, N.; Hara, H.
Abstract: We analyze "sit-and-stare" mode observations of continuous outflows and waves with the Extreme ultraviolet Imaging Spectrometer (EIS) on board Hinode, whose slit was located along the open field lines at the edge of active region NOAA 10942 on February 20, 2007. We found both intensity and velocity disturbances in Fe xii 195.12 Å propagating along the field lines with apparent speeds of 140 km s-1. The Doppler shifts shows mean upward velocities of 30–50 km s-1 and small velocity disturbances with amplitudes of 5–15 km s-1 in phase with intensity disturbances of 3–5% amplitude relative to the mean intensity. Not only a quasi-periodicity of 10–13 minutes but also “tad pole'' signatures—which may be evidence of propagating waves—were observed at the footpoints of the loops. Covariation of intensity and Doppler velocity is consistent with upward motion of propagating slow-mode magnetoacoustic waves. The energy flux of the waves was estimated to be 1–3× 105 erg s-1 cm–2, which is not enough to account for coronal heating but sufficient for solar wind acceleration. High temporal spectroscopic observation also revealed intermittent signatures of line broadening at the footpoints of the loops. Each of them seems to correspond to the footpoints of propagating disturbances. This may indicate that the origins of flows and waves are unresolved explosive events at the lower atmosphere, by analogy to spectroscopic observations of a jet.
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