Evolution of active region outflows throughout an active region lifetime

Abstract

We have shown previously that SOHO/UVCS data allow us to detect active region (AR) outflows at coronal altitudes higher than those reached by other instrumentation. These outflows are thought to be a component of the slow solar wind. Our purpose is to study the evolution of the outflows in the intermediate corona from AR 8100, from the time the AR first forms until it dissolves, after several transits at the solar limb. Data acquired by SOHO/UVCS at the time of the AR limb transits, at medium latitudes and at altitudes ranging from 1.5 to 2.3 R_sun, were used to infer the physical properties of the outflows through the AR evolution. To this end, we applied the Doppler dimming technique to UVCS spectra. These spectra include the H I Lyman alpha line and the O VI doublet lines at 1031.9 and 1037.6 A. Plasma speeds and electron densities of the outflows were inferred over several rotations of the Sun. AR outflows are present in the newly born AR and persist throughout the entire AR life. Moreover, we found two types of outflows at different latitudes, both possibly originating in the same negative polarity area of the AR. We also analyzed the behavior of the Si XII 520 A line along the UVCS slit in an attempt to reveal changes in the Si abundance when different regions are traversed. Although we found some evidence for a Si enrichment in the AR outflows, alternative interpretations are also plausible. Our results demonstrate that outflows from ARs are detectable in the intermediate corona throughout the whole AR lifetime. This confirms that outflows contribute to the slow wind.

arXiv comment13 pages, Astronomy and Astrophysics accepted

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Cited by in corpus (11)

• Origins of the Ambient Solar Wind: Implications for Space Weather
• Upflows in the upper solar atmosphere
• Helium abundance and speed difference between helium ions and protons in the solar wind from coronal holes, active regions, and quiet Sun
• Apparent and Intrinsic Evolution of Active Region Upflows
• A comparison of the active region upflow and core properties using simultaneous spectroscopic observations from IRIS and Hinode
• Widespread Occurrence of High-Velocity Upflows in Solar Active Regions
• Effects of the chromospheric Lyα line profile shape on the determination of the solar wind HI outflow velocity using the Doppler dimming technique
• Plasma Upflows Induced by Magnetic Reconnection Above an Eruptive Flux Rope
• Analysis of a long-duration AR throughout five solar rotations: Magnetic properties and ejective events
• Characteristics of solar wind rotation
• Active region upflows in various coronal structures and their coupling to the lower atmosphere