Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

Abstract

We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer and HXR measurements acquired with RHESSI during an M-class flare. During the flare impulsive phase, we observe no significant flows in the cooler Fe XIII line but strong upflows, up to 80-150 km/s, in the hotter Fe XVI line. The largest Doppler shifts observed in the Fe XVI line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe XIII line pair ratio exhibited fast increase (within two minutes) from the pre-flare level of 5.01x10^(9) cm^(-3) to 3.16x10^(10) cm^(-3) during the flare peak. The nonthermal energy flux density deposited from the coronal acceleration site to the lower atmospheric layers during the flare peak was found to be 1.34x10^(10) erg/s/cm^(2) for a low-energy cut-off that was estimated to be 16 keV. During the decline flare phase, we found a secondary intensity and density peak of lower amplitude that was preceded by upflows of 15 km/s that were detected in both lines. The flare was also accompanied by a filament eruption that was partly captured by the EIS observations. We derived Doppler velocities of 250-300 km/s for the upflowing filament material.The spectroscopic results for the flare peak are consistent with the scenario of explosive chromospheric evaporation, although a comparatively low value of the nonthermal energy flux density was determined for this phase of the flare. This outcome is discussed in the context of recent hydrodynamic simulations. It provides observational evidence that the response of the atmospheric plasma strongly depends on the properties of the electron beams responsible for the heating, in particular the steepness of the energy distribution.

arXiv comment13 pages, 11 figures, accepted for publication in Astronomy and Astrophysics

References in corpus (26)

• An Observational Overview of Solar Flares
• Global Energetics of Thirty-Eight Large Solar Eruptive Events
• Radiative Hydrodynamic Models of the Optical and Ultraviolet Emission from Solar Flares
• Imaging coronal magnetic-field reconnection in a solar flare
• Velocity Characteristics of Evaporated Plasma Using Hinode/EIS
• The Magnetic Field in the Solar Atmosphere
• Global Properties of Solar Flares
• Investigation of the Neupert effect in solar flares. I. Statistical properties and the evaporation model
• Slipping magnetic reconnection during an X-class solar flare observed by SDO/AIA
• RHESSI and SOHO/CDS Observations of Explosive Chromospheric Evaporation
• Observational Evidence for Gentle Chromospheric Evaporation During the Impulsive Phase of a Solar Flare
• Quasi-periodic Slipping Magnetic Reconnection During an X-class Solar Flare Observed by the Solar Dynamics Observatory and Interface Region Imaging Spectrograph
• Properties of a solar flare kernel observed by Hinode and SDO
• Modelling of EIS spectrum drift from instrumental temperatures
• A Non-radial Eruption in a Quadrupolar Magnetic Configuration with a Coronal Null
• Coronal magnetic reconnection driven by CME expansion -- the 2011 June 7 event
• Magnetohydrodynamic Simulation of the X2.2 Solar Flare on 2011 February 15: II. Dynamics Connecting the Solar Flare and the Coronal Mass Ejection
• Dynamics and evolution of an eruptive flare
• Magnetic Structure Producing X- and M-Class Solar Flares in Solar Active Region 11158
• Helioseismic response to X2.2 solar flare of February 15, 2011
• Plasma diagnostics of an EIT wave observed by Hinode/EIS and SDO/AIA
• Time-Dependent Density Diagnostics of Solar Flare Plasmas Using SDO/EVE
• Multiwavelength imaging and spectroscopy of chromospheric evaporation in an M-class solar flare
• Measuring the Magnetic Field Strength of the Quiet Solar Corona Using "EIT Waves"
• Sign singularity and flares in solar active region NOAA 11158
• Observation of 2011-02-15 X2.2 flare in Hard X-ray and Microwave

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• Statistical Study of Chromospheric Evaporation in Impulsive Phase of Solar Flares
• Energy Deposition by Energetic Electrons in a Diffusive Collisional Transport Model
• A Spectroscopic Measurement of High Velocity Spray Plasma from an M-class Flare and Coronal Mass Ejection