Locating Hot Plasma in Small Flares using Spectroscopic Overlappogram Data from the Hinode {\it EUV} Imaging Spectrometer

Abstract

One of the key processes associated with the "standard" flare model is chromospheric evaporation, a process where plasma heated to high temperatures by energy deposition at the flare footpoints is driven upwards into the corona. Despite several decades of study, a number of open questions remain, including the relationship between plasma produced during this process and observations of earlier "superhot" plasma. Hinode/EIS has a wide slot often used as a flare trigger in the He II emission line band. Once the intensity passes a threshold level, the study switches to one focussed on the flaring region. However, when the intensity is not high enough to reach the flare trigger threshold, these datasets are available during the entire flare period and provide high-cadence spectroscopic observations over a large field of view. We use one-minute cadence data from two such studies of a C4.7 flare and a C1.6 flare to probe the relationship between hot Fe XXIV plasma and plasmas observed by RHESSI and XRT to track where the emission comes from, and when it begins. Although the spatial and spectral information are merged in the wide-slot data, it is still possible to extract when the hot plasma appears using the Fe XXIV spectral image. It is also possible to derive spectrally pure Fe XXIV light curves from the EIS data, and compare them with those derived from hard X-rays, enabling a full exploration of the evolution of hot emission. The Fe XXIV emission peaks just after the peak in the hard X-ray lightcurve; consistent with an origin in the evaporation of heated plasma following the transfer of energy to the lower atmosphere. A peak was also found for the C4.7 flare in the RHESSI peak temperature, which occurred before the hard X-rays peaked. This suggests that the first peak in hot-plasma emission is likely directly related to the energy-release process.

References in corpus (12)

• The Interface Region Imaging Spectrograph (IRIS)
• An Observational Overview of Solar Flares
• Velocity Characteristics of Evaporated Plasma Using Hinode/EIS
• RHESSI Line and Continuum Observations of Super-hot Flare Plasma
• The 2014 March 29 X-flare: sub-arcsecond resolution observations of Fe XXI 1354.1
• Simultaneous IRIS and Hinode/EIS observations and modelling of the 27 October 2014 X 2.0 class flare
• Statistical Properties of Super-hot Solar Flares
• Analysis and modelling of recurrent solar flares observed with Hinode/EIS on March 9, 2012
• IRIS, Hinode, SDO, and RHESSI observations of a white light flare produced directly by non-thermal electrons
• Coronal-Temperature-Diagnostic Capability of the Hinode/X-Ray Telescope Based on Self-Consistent Calibration. II. Calibration with on-Orbit Data
• Hard X-ray footpoint sizes and positions as diagnostics of flare accelerated energetic electrons in the low solar atmosphere
• Calibrating Data from the Hinode/X-Ray Telescope and Associated Uncertainties

Cited by in corpus (1)

• Properties of EUV Imaging Spectrometer (EIS) Slot Observations