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26 April 2024 |
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Velocity Characteristics of Evaporated Plasma Using Hinode/EIS | | Ryan O. Milligan
; Brian R. Dennis
; | | Date: |
11 May 2009 | | Abstract: | This paper presents a detailed study of chromospheric evaporation using the
EUV Imaging Spectrometer (EIS) onboard Hinode in conjunction with HXR
observations from 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)~8-18 T (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)~60-17 T (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 >5x10^10 ergs cm^-2 s^-1 consistent with
the value required to drive explosive chromospheric evaporation from
hydrodynamic simulations. | | Source: | arXiv, 0905.1669 | | Services: | Forum | Review | PDF | Favorites | |
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