The Spectroscopic Signature of Quasi-periodic Upflows in Active Region Timeseries

Abstract

Quasi-periodic propagating disturbances are frequently observed in coronal intensity image sequences. These disturbances have historically been interpreted as being the signature of slow-mode magnetoacoustic waves propagating into the corona. The detailed analysis of Hinode EUV Imaging Spectrometer (EIS) timeseries observations of an active region (known to contain propagating disturbances) shows strongly correlated, quasi-periodic, oscillations in intensity, Doppler shift, and line width. No frequency doubling is visible in the latter. The enhancements in the moments of the line profile are generally accompanied by a faint, quasi-periodically occurring, excess emission at ~100 km/s in the blue wing of coronal emission lines. The correspondence of quasi-periodic excess wing emission and the moments of the line profile indicates that repetitive high-velocity upflows are responsible for the oscillatory behavior observed. Furthermore, we show that the same quasi-periodic upflows can be directly identified in a simultaneous image sequence obtained by the Hinode X-Ray Telescope (XRT). These results are consistent with the recent assertion of De Pontieu & McIntosh (2010) that the wave interpretation of the data is not unique. Indeed, given that several instances are seen to propagate along the direction of the EIS slit that clearly show in-phase, quasi-periodic variations of intensity, velocity, width (without frequency doubling), and blue wing enhanced emission this dataset would appear to provide a compelling example that upflows are more likely to be the main cause of the quasi-periodicities observed here, as such correspondences are hard to reconcile in the wave paradigm.

5 figures, accepted by ApJ Letters

References in corpus (5)

• Observing the Roots of Solar Coronal Heating - in the Chromosphere
• High precision density measurements in the solar corona: I. Analysis methods and results for Fe XII and Fe XIII
• Flows and Non-thermal Velocities in Solar Active Regions Observed with the Extreme-ultraviolet Imaging Spectrometer on Hinode: A Tracer of Active Region Sources of Heliospheric Magnetic Fields?
• STEREO Observations of Quasi-Periodically Driven High Velocity Outflows in Polar Plumes
• Propagating waves in polar coronal holes as seen by SUMER and EIS

Cited by in corpus (31)

• Persistent Doppler shift oscillations observed with HINODE/EIS in the solar corona: spectroscopic signatures of Alfvenic waves and recurring upflows
• Generation of Solar Spicules and Subsequent Atmospheric Heating
• Two components of the coronal emission revealed by EUV spectroscopic observations
• Observation of High-speed Outflow on Plume-like Structures of the Quiet Sun and Coronal Holes with SDO/AIA
• MHD Waves in open coronal structures
• Frequency-dependent damping in propagating slow magneto-acoustic waves
• Propagating intensity disturbances in polar corona as seen from AIA/SDO
• Upflows in the upper solar atmosphere
• Coronal Fourier power spectra: implications for coronal seismology and coronal heating
• Spectroscopic Observations of Propagating Disturbances in a Polar Coronal Hole: Evidence of Slow Magneto-acoustic Waves
• Doppler shift oscillations from a hot line observed by IRIS
• Investigating the Transition Region Explosive Events and Their Relationship to Network Jets
• Quasi-periodic pulsations with periods that change depending on whether the pulsations have thermal or nonthermal components
• Spectroscopic and Stereoscopic Observations of the Solar Jets
• Quasi-periodic pulsations with multiple periods in hard X-ray emission
• Effect of Thermal Conductivity, Compressive Viscosity and Radiative Cooling on the Phase Shift of Propagating Slow Waves with and without Heating-Cooling Imbalance
• On the Parallel and Perpendicular Propagating Motions Visible in Polar Plumes: An Incubator For (Fast) Solar Wind Acceleration?
• Excitation of flare-induced waves in coronal loops and the effects of radiative cooling
• Oscillations in active region fan loops: Observations from EIS/{\it Hinode} and AIA/SDO
• Evolution of active region outflows throughout an active region lifetime
• Revisiting the relation between nonthermal line widths and transverse MHD wave amplitudes
• Plasma injection into a solar coronal loop
• Modelling the connection between propagating disturbances and solar spicules
• Propagating Kink Waves in an Open Coronal Magnetic Flux Tube with Gravitational Stratification: Magnetohydrodynamic Simulation and Forward Modelling
• Reconnection generated plasma flows in the quasi-separatrix layer in localised solar corona
• Slow solar wind sources. High-resolution observations with a quadrature view
• Plasma Upflows Induced by Magnetic Reconnection Above an Eruptive Flux Rope
• Dynamics in the transition region beneath active region upflows viewed by IRIS
• Investigating coronal wave energy estimates using synthetic non-thermal line widths
• Active region upflows in various coronal structures and their coupling to the lower atmosphere
• A multi-viewpoint comparison of the velocity field of coronal propagating disturbances