VELOCITY CHARACTERISTICS OF EVAPORATED PLASMA USING HINODE/EUV IMAGING SPECTROMETER

By R. Milligan, Brian R. Dennis. 2009

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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 (vup) was found to scale with temperature as vup (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 vdown (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 ≳5 × 1010 erg cm−2 s−1, consistent with the value required to drive explosive chromospheric evaporation from hydrodynamic simulations.

Subfields: Astronomy and Astrophysics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/a8a47608a05a5889e70c963190c72e2a6173c09a

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Citations in the corpus

Standing Slow-Mode Waves in Hot Coronal Loops: Observations, Modeling, and Coronal Seismology (2010, background): “…high-speed upflow is consistent with the impulsive chromospheric evaporation produced in flares (e.g. Fisher et al. 1985; Doschek & Warren 2005; Milligan & Dennis 2009), while the standing slow mode waves in flare loops are excited by a shock front or blast compression disturbance preceding…”
GLOBAL ENERGETICS OF THIRTY-EIGHT LARGE SOLAR ERUPTIVE EVENTS (2012, background): “Milligan & Dennis (2009) have shown that similar best-fit parameter values are determined using different individual detectors (detectors 1, 3, 4, 5, 6, and 9 in their case), which leads to an estimate of the systematic uncertainties in the calculated total energy in electrons of ∼20%.”
PLASMOID EJECTIONS AND LOOP CONTRACTIONS IN AN ERUPTIVE M7.7 SOLAR FLARE: EVIDENCE OF PARTICLE ACCELERATION AND HEATING IN MAGNETIC RECONNECTION OUTFLOWS (2013, methodology): “To infer the overall properties of nonthermal particles and thermal plasma, we analyzed spatially integrated RHESSI spectra of individual detectors following the procedures detailed in Liu et al. (2008) and Milligan & Dennis (2009).”
An Observational Overview of Solar Flares (2011, methodology): “The improved spatial, spectral and temporal capabilities of the Extreme Ultraviolet Imaging Spectrometer (EIS) onboardHinode has also been used to study chromospheric evaporation using emission lines formed over a broad range of temperatures (Milligan & Dennis 2009).”