Limb Event Brightenings and Fast Ejection Using IRIS Mission Observations

Tavabi, E.; Koutchmy, S.; Golub, L.

doi:10.1007/s11207-015-0771-3

Cited by 19 publications

(19 citation statements)

References 35 publications

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“…Therefore resonant scattering is often dominant above the limb. The search for asymmetric profiles in off-limb events, such as those described in Tavabi et al (2015) where Si iv lines are recorded with IRIS, would allow for a new and more complete diagnostic of coronal plasmas.…”

Section: Discussionmentioning

confidence: 99%

Evidence of scattering effects influenced by plasma flows in C VI 1548 Å, 1550 Å spectral lines emitted from the Sun

Gontikakis

Vial

2016

A&A

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Aims. We search for, and study, individual spectral profiles where the complex shape of the C iv 1548 Å line is different from the shape of the simultaneously recorded C iv 1550 Å line. Such an asymmetry is not expected for line emission resulting from collisional excitation. Therefore we propose an explanation of these observations through the differential effect of velocity fields on resonant scattering. Methods. We analyse spectra recorded with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on the Solar and Heliospheric Observatory (SOHO) over active region, NOAA 8541 as well as a second data set on the quiet Sun. We perform Gaussian fits on the individual profiles with two or three Gaussian functions. Moreover, we parameterize the profile asymmetries by calculating the intensity ratios I 1548 /I 1550 , from the derived Gaussian functions. We also calculate artificial spectral profiles emitted from two plasma volumes, which have different line of sight motions and where the plasma emission is influenced by resonant scattering. Results. We locate three small regions in NOAA 8541 which have spectral asymmetries. There the profiles have two or three spectral components, with different intensity ratios. Artificial profiles show that two plasma volumes, having distinct velocities relative to the observer, may reproduce the observed profiles, under the influence of resonant scattering. Conclusions. Asymmetric profiles, found in an active region, can be used as a diagnostic for the importance of resonant scattering in transition region plasma.

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Section: Discussionmentioning

confidence: 99%

Evidence of scattering effects influenced by plasma flows in C VI 1548 Å, 1550 Å spectral lines emitted from the Sun

Gontikakis

Vial

2016

A&A

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“…Between t=30 s and t=45 s, the jet continues to develop and moves upward. The most representative time of the jet formation is t=60 s; at this time we can see a structure with a similar morphology to a Type II spicule, which reaches a height of about z≈7 Mm measured from the transition region (Tavabi et al 2015), and a vertical velocity of about v z ≈130 km s −1 , as shown in Figure 6. These characteristics are similar to those of a Type II spicule (De Pontieu et al 2007b).…”

Section: Results Of Numerical Simulationsmentioning

confidence: 71%

“…Apart from the upward motion, Type II spicules show swaying or transverse motions at the limb, with velocity amplitudes of the order of 10-30 km s −1 and periods of 100-500 s (De Pontieu et al 2007a;Tomczyk et al 2007;Zaqarashvili & Erdélyi 2009;McIntosh et al 2011;Sharma et al 2017), suggesting generation of upward, downward, and standing Alfvén waves (Okamoto & De Pontieu 2011;Tavabi et al 2015), and the generation of MHD kink mode waves or Alfvén waves due to magnetic reconnection (Nishizuka et al 2008;He et al 2009;Kuridze et al 2012;McLaughlin et al 2012). Suematsu et al (2008) suggested that some spicules show multi-thread structure as a result of possible rotation.…”

Section: Introductionmentioning

confidence: 99%

I. Jet Formation and Evolution Due to 3D Magnetic Reconnection

González-Avilés

Guzmán

Fedun

et al. 2018

ApJ

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Using simulated data-driven, 3D resistive MHD simulations of the solar atmosphere, we show that 3D magnetic reconnection may be responsible for the formation of jets with the characteristics of Type II spicules. We numerically model the photosphere-corona region using the C7 equilibrium atmosphere model. The initial magnetic configuration is a 3D potential magnetic field, extrapolated up to the solar corona region from a dynamic realistic simulation of the solar photospheric magnetoconvection model that mimics the quiet-Sun. In this case, we consider a uniform and constant value of the magnetic resistivity of 12.56 Ω m. We have found that the formation of the jet depends on the Lorentz force, which helps to accelerate the plasma upward. Analyzing various properties of the jet dynamics, we found that the jet structure shows a Doppler shift close to regions with high vorticity. The morphology, the upward velocity covering a range up to 130 km s −1 , and the timescale formation of the structure between 60 and 90 s, are similar to those expected for Type II spicules.

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“…Studies of such motions have been done in several recent papers (e.g. De Pontieu et al 2014a;Tavabi et al 2014aTavabi et al , 2015a. Alissandrakis et al (2018) performed an extended work to deduce the ''average" properties of a static chromosphere from the IRIS mission FUV data.…”

Section: Introductionmentioning

confidence: 99%

Chromospheric Peculiar Off-limb Dynamical Events from IRIS Observations

Tavabi

Koutchmy

2019

ApJ

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To study motions and oscillations in the solar chromosphere and at the transition region (TR) level we analyze some extreme Doppler shifts observed off-limb with the Interface Region Imaging Spectrograph (IRIS). Raster scans and slit-jaw imaging observations performed in the near-ultraviolet (NUV) channels were used. Large transverse oscillations are revealed by the far wings profiles after accurately removing the bulk average line profiles of each sequence. Different regions around the Sun are considered. Accordingly, the cool material of spicules is observed in Mg II lines rather dispersed up to coronal heights. In the quiet Sun and especially in a polar coronal hole, we study dynamical properties of the dispersed spiculesmaterial off-limb using a high spectral, temporal and spatial resolutions IRIS observations. We suggest that numerous smallscale jet-like spicules show rapid twisting and swaying motions evidenced by the large distortion and dispersion of the line profiles, including impressive periodic Doppler shifts. Most of these events repeatedly appear in red-and blue-shifts above the limb throughout the whole interval of the observation datasets with an average swaying speed of order ±35 kms -1 reaching a maximum value of 50 km s -1 in the polar coronal hole region, well above the 2.2 Mm heights. We identified for the 1 st time waves with a short period of order of 100 sec and less and transverse amplitudes of order of ± 20 to 30 km s -1 with the definite signature of Alfven waves. No correlation exists between brightness and Doppler shift variations; the phase speed of the wave is very large and cannot definitely be determined from the spectral features seen along the quasi-radial features. Even shorter periods waves are evidenced, although their contrast is greatly attenuated by the overlapping effects along the line of sight.

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Limb Event Brightenings and Fast Ejection Using IRIS Mission Observations

Cited by 19 publications

References 35 publications

Evidence of scattering effects influenced by plasma flows in C VI 1548 Å, 1550 Å spectral lines emitted from the Sun

Evidence of scattering effects influenced by plasma flows in C VI 1548 Å, 1550 Å spectral lines emitted from the Sun

I. Jet Formation and Evolution Due to 3D Magnetic Reconnection

Chromospheric Peculiar Off-limb Dynamical Events from IRIS Observations

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