Velocity Characteristics of Evaporated Plasma Using Hinode/EUV Imaging Spectrometer

Ryan O. Milligan, Brian R. Dennis

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132 Citations (Scopus)

Abstract

This paper presents a detailed study of chromospheric evaporation using the EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with hard X-ray (HXR) observations from Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). The advanced capabilities of EIS were used to measure Doppler shifts in 15 emission lines covering the temperature range T = 0.05-16 MK during the impulsive phase of a C-class flare on 2007 December 14. Blueshifts indicative of the evaporated material were observed in six emission lines from Fe XIV-XXIV (2-16 MK). Upflow velocity (v up) was found to scale with temperature as v up (km s-1) ≈ 8-18T(MK). Although the hottest emission lines, Fe XXIII and Fe XXIV, exhibited upflows of >200 km s-1, their line profiles were found to be dominated by a stationary component in contrast to the predictions of the standard flare model. Emission from O VI-Fe XIII lines (0.5-1.5 MK) was found to be redshifted by v down (km s-1) ≈ 60-17T (MK) and was interpreted as the downward-moving "plug" characteristic of explosive evaporation. These downflows occur at temperatures significantly higher than previously expected. Both upflows and downflows were spatially and temporally correlated with HXR emission observed by RHESSI that provided the properties of the electron beam deemed to be the driver of the evaporation. The energy flux of the electron beam was found to be gsim5 × 1010 erg cm-2 s-1, consistent with the value required to drive explosive chromospheric evaporation from hydrodynamic simulations....
Original languageEnglish
Pages (from-to)968-975
JournalThe Astrophysical Journal
Volume699
DOIs
Publication statusPublished - Jul 2009

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