Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userPlasma diagnostics of an EIT wave observed by Hinode/EIS and SDO/AIA
325
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present plasma diagnostics of an EIT wave observed with high cadence in Hinode/EIS sit-and-stare spectroscopy and SDO/AIA imagery obtained during the HOP-180 observing campaign on 2011 February 16. At the propagating EIT wave front, we observe downward plasma flows in the EIS Fe XII, Fe XIII, and Fe XVI spectral lines (log T ~ 6.1-6.4) with line-of-sight (LOS) velocities up to 20 km/s. These red-shifts are followed by blue-shifts with upward velocities up to -5 km/s indicating relaxation of the plasma behind the wave front. During the wave evolution, the downward velocity pulse steepens from a few km/s up to 20 km/s and subsequently decays, correlated with the relative changes of the line intensities. The expected increase of the plasma densities at the EIT wave front estimated from the observed intensity increase lies within the noise level of our density diagnostics from EIS XIII 202/203 AA line ratios. No significant LOS plasma motions are observed in the He II line, suggesting that the wave pulse was not strong enough to perturb the underlying chromosphere. This is consistent with the finding that no Halpha Moreton wave was associated with the event. The EIT wave propagating along the EIS slit reveals a strong deceleration of a ~ -540 m/s2 and a start velocity of v0 ~ 590 km/s. These findings are consistent with the passage of a coronal fast-mode MHD wave, pushing the plasma downward and compressing it at the coronal base.
rate research
Read More
A comprehensive study of the physical parameters of active region fan loops is presented using the observations recorded with the Interface Region Imaging Spectrometer (IRIS), the EUV Imaging Spectrometer (EIS) on-board Hinode and the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on-board the Solar Dynamics Observatory (SDO). The fan loops emerging from non-flaring AR~11899 (near the disk-center) on 19th November, 2013 are clearly discernible in AIA 171~{AA} images and those obtained in ion{Fe}{8} and ion{Si}{7} images using EIS. Our measurements of electron densities reveal that the footpoints of these loops are approximately at constant pressure with electron densities of $log,N_{e}=$ 10.1 cm$^{-3}$ at $log,[T/K]=5.15$ (ion{O}{4}), and $log,N_{e}=$ 8.9 cm$^{-3}$ at $log,[T/K]=6.15$ (ion{Si}{10}). The electron temperature diagnosed across the fan loops by means of EM-Loci suggest that at the footpoints, there are two temperature components at $log,[T/K]=4.95$ and 5.95, which are picked-up by IRIS lines and EIS lines respectively. At higher heights, the loops are nearly isothermal at $log,[T/K]=5.95$, that remained constant along the loop. The measurement of Doppler shift using IRIS lines suggests that the plasma at the footpoints of these loops is predominantly redshifted by 2-3~km~s$^{-1}$ in ion{C}{2}, 10-15~km~s$^{-1}$ in ion{Si}{4} and $~$15{--}20~km~s$^{-1}$ in ion{O}{4}, reflecting the increase in the speed of downflows with increasing temperature from $log,[T/K]=4.40$ to 5.15. These observations can be explained by low frequency nanoflares or impulsive heating, and provide further important constraints on the modeling of the dynamics of fan loops.
In this paper, we carry out multiwavelength observations of three recurring jets on 2014 November 7. The jets originated from the same region at the edge of AR 12205 and propagated along the same coronal loop. The eruptions were generated by magnetic reconnection, which is evidenced by continuous magnetic cancellation at the jet base. The projected initial velocity of the jet2 is 402 km s. The accelerations in the ascending and descending phases of jet2 are not consistent, the former is considerably larger than the value of solar gravitational acceleration at the solar surface, while the latter is lower than solar gravitational acceleration. There are two possible candidates of extra forces acting on jet2 during its propagation. One is the downward gas pressure from jet1 when it falls back and meets with jet2. The other is the viscous drag from the surrounding plasma during the fast propagation of jet2. As a contrast, the accelerations of jet3 in the rising and falling phases are constant, implying that the propagation of jet3 is not significantly influenced byextra forces.
We perform multiwavelength time-distance analysis of a fan loop system anchored in an isolated sunspot region AR 12553. The active region was observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. We measure the phase speeds of the propagating intensity disturbances by employing cross-correlation analysis, as well as by obtaining the slopes in xt-plots. We obtain original as well as de-trended light curves at different heights of the time-distance maps and characterize them by performing Fourier and Wavelet analysis, respectively. The time-distance maps reveal clear propagation of intensity oscillations in all the coronal EUV channels except AIA 94 and 335~{AA}. We determine the nature of the intensity disturbances as slow magnetoacoustic waves by measuring their phase speeds. The time-distance maps, as well as the de-trended light curves, show an increase and decrease in the amplitude of propagating 3-min oscillations over time. The amplitude variations appear most prominent in AIA 171~{AA}, though other EUV channels also show such signatures. Fourier power spectrum yield the presence of significant powers with several nearby frequencies between 2--3 minutes (5--8 mHz), along with many other smaller peaks between 2--4 minutes. Wavelet analysis shows an increase and decrease of oscillating power around 3-min simultaneous to the amplitude variations. We obtain the modulation period to be in the range of 20--30 minutes. Our results provide the viability of occurrence of phenomenon like `Beat among the nearby frequencies giving rise to the observed amplitude modulation. However, we cannot, at this stage, rule out the possibility that the modulation may be driven by variability of an underlying unknown source.
This study on plasma heating considers the time-dependent ionization process during a large solar flare on September 10, 2017, observed by Hinode/EIS. The observed FeXXIV / FeXXIII ratios increase downstream of the reconnection outflow, and they are consistent with the time-dependent ionization effect at a constant electron temperature Te = 25 MK. Moreover, this study also shows that the non-thermal velocity, which can be related to the turbulent velocity, reduces significantly along the downstream of the reconnection outflow, even when considering the time-dependent ionization process.
Quiet Sun and active region spectra from the Hinode/EIS instrument are presented, and the strongest lines from different temperature regions discussed. A list of emission lines recommended to be included in EIS observation studies is presented based on analysis of blending and diagnostic potential using the CHIANTI atomic database. In addition we identify the most useful density diagnostics from the ions covered by EIS.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
