IRIS Mg ii Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole

Tei, Akiko; Gunár, S.; Heinzel, P.; Okamoto, Takenori J.; Štěpán, Jiří; Jejčič, S.; Shibata, Kazunari

doi:10.3847/1538-4357/ab5db1

Cited by 22 publications

(17 citation statements)

References 32 publications

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“…Recently Tei et al (2018) applied the cloud model technique with constant source functions to the Mg II lines which present complex profiles because of their central reversal. Considering multi clouds, Mg II complex profiles of off-limb spicules were successfully fitted (Tei et al 2020).…”

Section: Cloud Model Methods For Mg II Linesmentioning

confidence: 99%

Multi-thermal atmosphere of a mini-solar flare during magnetic reconnection observed with IRIS

Joshi

Schmieder

Tei

et al. 2021

A&A

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Context. The Interface Region Imaging Spectrograph (IRIS) with its high spatial and temporal resolution facilitates exceptional plasma diagnostics of solar chromospheric and coronal activity during magnetic reconnection. Aims. The aim of this work is to study the fine structure and dynamics of the plasma at a jet base forming a mini-flare between two emerging magnetic fluxes (EMFs) observed with IRIS and the Solar Dynamics Observatory instruments. Methods. We proceed to a spatio-temporal analysis of IRIS spectra observed in the spectral ranges of Mg II, C II, and Si IV ions. Doppler velocities from Mg II lines were computed using a cloud model technique. Results. Strong asymmetric Mg II and C II line profiles with extended blue wings observed at the reconnection site (jet base) are interpreted by the presence of two chromospheric temperature clouds: one explosive cloud with blueshifts at 290 km s−1 and one cloud with smaller Doppler shift (around 36 km s−1). Simultaneously at the same location (jet base), strong emission of several transition region lines (e.g. O IV and Si IV), emission of the Mg II triplet lines, and absorption of identified chromospheric lines in Si IV broad profiles have been observed and analysed. Conclusions. Such observations of IRIS line and continuum emissions allow us to propose a stratification model for the white light, mini-flare atmosphere with multiple layers of different temperatures along the line of sight in a reconnection current sheet. It is the first time that we could quantify the fast speed (possibly Alfvénic flows) of cool clouds ejected perpendicularly to the jet direction via the cloud model technique. We conjecture that the ejected clouds come from plasma which was trapped between the two EMFs before reconnection or be caused by chromospheric-temperature (cool) upflow material similar to a surge during reconnection.

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Section: Cloud Model Methods For Mg II Linesmentioning

confidence: 99%

Multi-thermal atmosphere of a mini-solar flare during magnetic reconnection observed with IRIS

Joshi

Schmieder

Tei

et al. 2021

A&A

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“…Prominence modelling was reviewed by, for example, Gibson (2018) and Gunár (2014). An example of a recent study employing radiative transfer modelling in spicules is available in, for example, Tei et al (2020), and an example of filament modelling is available in Schwartz et al (2019). Information regarding the modelling of Lyman-α in CME cores is available in Heinzel et al (2016), and information regarding the modelling of Lyman-α in the solar wind is available in Dolei et al (2019).…”

Section: Introductionmentioning

confidence: 99%

Quiet-Sun hydrogen Lyman-α line profile derived from SOHO/SUMER solar-disk observations

Gunár

Schwartz

Koza

et al. 2020

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Context. The solar radiation in the Lyman-α spectral line of hydrogen plays a significant role in the illumination of chromospheric and coronal structures, such as prominences, spicules, chromospheric fibrils, cores of coronal mass ejections, and solar wind. Moreover, it is important for the investigation of the heliosphere, Earth's ionosphere, and the atmospheres of planets, moons, and comets. Aims. We derive a reference quiet-Sun Lyman-α spectral profile that is representative of the Lyman-α radiation from the solar disk during a minimum of solar activity. This profile can serve as an incident radiation boundary condition for the radiative transfer modelling of chromospheric and coronal structures. Because the solar radiation in the Lyman lines is not constant over time but varies significantly with the solar cycle, we provide a method for the adaptation of the incident radiation Lyman line profiles (Lyman-α and higher lines) to a specific date. Moreover, we analyse how the change in the incident radiation influences the synthetic spectra produced by the radiative transfer modelling. Methods. We used SOHO/SUMER Lyman-α raster scans obtained without the use of the attenuator in various quiet-Sun regions on the solar disk. The observations were performed on three consecutive days (June 24, 25, and 26, 2008) during a period of minimum solar activity. The reference Lyman-α profile was obtained as a spatial average over eight available raster scans. To take into account the Lyman-α variation with the solar cycle, we used the LISIRD composite Lyman-α index. To estimate the influence of the change in the incident radiation in the Lyman lines on the results of radiative transfer models, we used a 2D prominence fine structure model. Results. We present the reference quiet-Sun Lyman-α profile and a table of coefficients describing the variation of the Lyman lines with the solar cycle throughout the lifetime of SOHO. The analysis of the influence of the change in the incident radiation shows that the synthetic spectra are strongly affected by the modification of the incident radiation boundary condition. The most pronounced impact is on the central and integrated intensities of the Lyman lines. There, the change in the synthetic spectra can often have the same amplitude as the change in the incident radiation itself. The impact on the specific intensities in the peaks of reversed Lyman-line profiles is smaller but still significant. The hydrogen Hα line can also be considerably affected, despite the fact that the Hα radiation from the solar disk does not vary with the solar cycle.

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“…Although, in many circumstances Mg lines are single peak profiles, for instance, sunspot umbrae (Tian et al 2014), solar flares (Kerr et al 2015), and filaments (Harra et al 2014). In addition, outside of the limb, Mg k lines exhibit single-peak profile (Tei et al 2020). Therefore, in present scenario as spectra was taken far away from the limb (see IRIS slit in the left-panel of figure 6 -white dashed line), we believe that Mg lines should be single peaked profiles.…”

Section: Opacity and Evolution Of Mg Resonance Lines In The Homologou...mentioning

confidence: 86%

Diagnostic of Homologous Solar Surge Plasma as observed by IRIS and SDO

Kayshap,

Payal,

Tripathi

et al. 2021

Preprint

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Surges have regularly been observed mostly in H α 6563 Å and Ca 8542 Å. However, surge ′ s response to other prominent lines of the interface-region (Mg k 2796.35 Å & h 2803.52 Å, O 1401.15 Å, Si 1402.77 Å) is not well studied. Here, the evolution and kinematics of six homologous surges are analysed using IRIS and AIA observations. These surges were observed on 7 th July 2014, located very close to the limb. DEM analysis is performed on these surges where the co-existence of cool (log T/K = 6.35) and relatively hot (log T/K = 6.95) components have been found at the base. This demonstrates that the bases of surges undergo substantial heating. During the emission of these surges in the above mentioned interface-region lines, being reported here for the first time, two peaks have been observed in the initial phase of emission, where one peak is found to be constant while other one as varying, i.e., non-constant (observed red to blueshifts across the surge evolution) in nature. This suggests the rotational motion of surge plasma. The heated base and rotating plasma suggests the occurrence of magnetic reconnection, most likely, as the trigger for homologous surges. During the emission of these surges, it is found that despite being optically thick (i.e., R kh < 2.0), central reversal was not observed for Mg k & h lines. Further, R kh increases with surge emission in time and it is found to have positive correlation with Doppler Velocity while negative with Gaussian width.

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IRIS Mg ii Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole

Cited by 22 publications

References 32 publications

Multi-thermal atmosphere of a mini-solar flare during magnetic reconnection observed with IRIS

Multi-thermal atmosphere of a mini-solar flare during magnetic reconnection observed with IRIS

Quiet-Sun hydrogen Lyman-α line profile derived from SOHO/SUMER solar-disk observations

Diagnostic of Homologous Solar Surge Plasma as observed by IRIS and SDO

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