Peter Young, George Doschek, Harry Warren, Hiro Hara
The standard model of solar flares predicts fast upflows of multi-million degree plasma following rapid heating of the solar chromosphere in the early phase of flares. Spatially-resolved spectroscopic observations from the EUV Imaging Spectrometer (EIS) on board the Hinode satellite have isolated these upflow regions in bright flare kernels for the first time. An example is presented from a M1.1 class flare observed on 2011 February 16 07:44 UT for which the location of the upflow region seen by EIS can be precisely aligned to high spatial resolution images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO), and surface magnetic field maps from the Heliospheric Magnetic Imager (HMI) on board SDO. A string of bright flare kernels is found to be aligned with a ridge of strong magnetic field, and one kernel site is highlighted for which an upflow speed of 400 km/s is measured in lines formed at 10-30 MK. Emission over a continuous range of temperatures down to the chromosphere is found, and the kernels have a similar morphology at all temperatures. The kernels are at the resolution limit of the AIA instrument, suggesting sizes of < 0.6 arcsec. For temperatures of 0.3-3.0 MK the EIS emission lines show multiple velocity components, with the dominant component becoming more blue-shifted with temperature from a redshift of 35 km/s at 0.3 MK to a blueshift of 60 km/s at 3.0 MK. Emission lines from 1.5-3.0 MK show a weak redshifted component at around 60-70 km/s implying multi-directional flows at the kernel site.
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http://arxiv.org/abs/1212.4388
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