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Diagnostics of the Coronal Hole and the adjacent Quiet Sun by The Hinode/EUV Imaging Spectrometer (EIS) | | P. Kayshap
; D. Banerjee
; A.K. Srivastava
; | | Date: |
3 Sep 2014 | | Abstract: | A comparison between a Coronal Hole (CH) and the adjacent Quiet-Sun (QS) has
been performed using spectroscopic diagnostics of Hinode/ the EUV Imaging
Spectrometer (EIS). Coronal funnels play an important role in the formation and
propagation of the nascent fast solar wind. Applying Gaussian fitting
procedures to the observed line profiles, Doppler velocity, intensity, line
width (FWHM) and electron density have been estimated over CH and adjacent QS
region of a North Polar Coronal Hole (NPCH). The aim of this study is to
identify the coronal funnels based on spectral signatures. Excess width regions
(excess FWHM above a threshold level) have been identified in QS and CH. The
plasma flow inversion (average red-shifts changing to blue-shifts at a specific
height) in CH and excess width regions of QS take place at ~
5.01$ imes$10$^{5}$ K. Furthermore, high density concentration in excess width
regions of QS provides an indication that these regions are the footprints of
coronal funnels. We have also found that non-thermal velocities of CH are
higher in comparison to QS confirming that the CHs are the source regions of
fast solar wind. Doppler and non-thermal velocities as recorded by different
temperature lines have been also compared with previously published results. As
we go from lower to upper solar atmosphere, down-flows are dominated in lower
atmosphere while coronal lines are dominated by up-flows with a maximum value
of ~ 10-12 km s$^{-1}$ in QS. Non-thermal velocity increases first but after
Log T$_{e}$ = 5.47 it decreases further in QS. This trend can be interpreted as
a signature of the dissipation of Alfv’en waves, while increasing trend as
reported earlier may attribute to the signature of the growth of Alfv’en waves
at lower heights. Predominance of occurrence of nano-flares around O {sc vi}
formation temperature could also explain non-thermal velocity trend. | | Source: | arXiv, 1409.1037 | | Services: | Forum | Review | PDF | Favorites | |
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