Estimating Ion Temperatures at the Polar Coronal Hole Boundary

Zhu, Yafen; Szente, Judit; Landi, E.

doi:10.3847/1538-4357/acc187

Cited by 3 publications

(3 citation statements)

References 80 publications

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“…In this study, the excessive heating to Z/A ions, such as Fe VIII, Fe X, and Fe XI, was also found in the EIS observation of the polar CH. Previous studies reported T eff = 4-6 MK for Fe X at the base of a polar CH during the solar minimum (Hahn et al 2010;Zhu et al 2023), which is consistent with 3PAMIS and EIS observations during the 2017 TSE.…”

Section: Preferential Heatingsupporting

confidence: 89%

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Spectroscopic Observations of the Solar Corona during the 2017 August 21 Total Solar Eclipse: Comparison of Spectral Line Widths and Doppler Shifts between Open and Closed Magnetic Structures

Zhu 朱,

Habbal,

Ding

et al. 2024

ApJ

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The spectroscopic observations presented here were acquired during the 2017 August 21 total solar eclipse (TSE) with a three-channel partially multiplexed imaging spectrometer operating at extremely high orders (>50). The 4 R ⊙ extent of the slit in the north–south direction scanned the corona starting from the central meridian out to approximately 1.0 R ⊙ off the east limb throughout totality. The line widths and Doppler shifts of the Fe x (637.4 nm) and Fe xiv (530.3 nm) emission lines, characteristic of 1.1 × 106 K and 1.8 × 106 K electron temperatures, respectively, varied across the different coronal structures intercepted by the slit. Fe xiv was the dominant emission in the closed fields of an active region and the base of a streamer, with relatively constant 20–30 km s−1 line widths independent of the height. In contrast, Fe x emission exhibited broader (>40 km s−1) line widths in open fields, which increased with height, in particular in the polar coronal hole. Inferences of line widths and Doppler shifts were consistent with extreme ultraviolet (EUV) observations from the Hinode/EUV Imaging Spectrograph, as well as with the near-infrared Fe xiii 1074 nm line observed by Coronal Multichannel Polarimeter. The differences in the spectral line widths between distinct coronal structures are interpreted as an indication of the predominance of wave heating in open structures versus localized heating in closed structures. This study underscores the unparalleled advantages and the enormous potential of TSE spectroscopy in measuring line widths simultaneously in open and closed fields at high altitudes, with minimal exposure times, stray light levels, and instrumental widths.

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Section: Preferential Heatingsupporting

confidence: 89%

“…This effect might be evident in open-field structures where fast outflows in the lower corona are expected. Consequently, different Doppler shifts along the LOS may broaden profiles in open-field structures (e.g., Akinari 2007;Zhu et al 2023).…”

Section: Los Integrationmentioning

confidence: 99%

Spectroscopic Observations of the Solar Corona during the 2017 August 21 Total Solar Eclipse: Comparison of Spectral Line Widths and Doppler Shifts between Open and Closed Magnetic Structures

Zhu 朱,

Habbal,

Ding

et al. 2024

ApJ

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“…Thus, with the current data sets, we were able to obtain density estimates but not temperature. Therefore, we used the reported temperature values, e.g., T log 6.20 10 = ( ) in the quiet Sun obtained by Doschek & Warren (2019), and for the coronal hole case, we used the temperature values ( T K log 5.9 6.2 10 » ( ) -) presented by Zhu et al (2023). They are derived from different intensity ratios observed by Hinode/EIS.…”

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confidence: 99%

The Plasma β in Quiet Sun Regions: Multi-instrument View

Rodríguez-Gómez,

Kuckein,

González Manrique

et al. 2024

ApJ

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A joint campaign of several spaceborne and ground-based observatories, such as the GREGOR solar telescope, the Extreme-ultraviolet Imaging Spectrometer (EIS), and the Interface Region Imaging Spectrograph (Hinode Observing Plan 381, 2019 October 11–22) was conducted to investigate the plasma β in quiet Sun regions. In this work, we focus on 2019 October 13, 17, and 19 to obtain the plasma β at different heights through the solar atmosphere based on multiheight observational data. We obtained temperature, density, and magnetic field estimates from the GREGOR High-resolution Fast Imager, Infrared Spectrograph, Interface Region Imaging Spectrograph, and EIS and complementary data from the Solar Dynamics Observatory Atmospheric Imaging Assembly (AIA). Using observational data and models (e.g., FALC and PFSS), we determined the plasma β in the photosphere, chromosphere, transition region, and corona. The obtained plasma β values lie inside the expected ranges through the solar atmosphere. However, at EIS and AIA coronal heights (from 1.03 to 1.20 R ⊙), plasma β values appear in the limit defined by Gary; such behavior was previously reported by Rodríguez Gómez et al. Additionally, we obtained the plasma β in the solar photosphere at different optical depths from log τ = − 1.0 to –2.0. These values decrease with optical depth. This work provides a complete picture of plasma β in quiet Sun regions through the solar atmosphere, which is a prerequisite of a better understanding of the plasma dynamics at the base of the solar corona.

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Propagating kink waves in an open coronal magnetic flux tube with gravitational stratification: Magnetohydrodynamic simulation and forward modelling

Gao,

Van Doorsselaere,

Tian

et al. 2024

A&A

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In coronal open-field regions, such as coronal holes, there are many transverse waves propagating along magnetic flux tubes, which are generally interpreted as kink waves. Previous studies have highlighted their potential role in coronal heating, solar wind acceleration, and seismological diagnostics of various physical parameters. This study aims to investigate propagating kink waves, considering both vertical and horizontal density inhomogeneity, using 3D magnetohydrodynamic (MHD) simulations. We established a 3D MHD model of a gravitationally stratified open flux tube, incorporating a velocity driver at the lower boundary to excite propagating kink waves. Forward modelling was conducted to synthesise observational signatures of the Fe ix 17.1 nm line. Resonant absorption and density stratification both affect the wave amplitude. When diagnosing the relative density profile with velocity amplitude, resonant damping needs to be properly considered to avoid a possible underestimation. In addition, unlike standing modes, propagating waves are believed to be Kelvin-Helmholtz stable. In the presence of vertical stratification, however, the phase mixing of transverse motions around the tube boundary can still induce small-scale structures, partially dissipating wave energy and leading to a temperature increase, especially at higher altitudes. Moreover, we conducted forward modeling to synthesise observational signatures, which revealed the promising potential of future coronal imaging spectrometers such as MUSE in resolving these wave-induced signatures. Also, the synthesised intensity signals exhibit apparent periodic variations, offering a potential method for indirectly observing propagating kink waves with current extreme ultraviolet imagers.

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Estimating Ion Temperatures at the Polar Coronal Hole Boundary

Cited by 3 publications

References 80 publications

Spectroscopic Observations of the Solar Corona during the 2017 August 21 Total Solar Eclipse: Comparison of Spectral Line Widths and Doppler Shifts between Open and Closed Magnetic Structures

Spectroscopic Observations of the Solar Corona during the 2017 August 21 Total Solar Eclipse: Comparison of Spectral Line Widths and Doppler Shifts between Open and Closed Magnetic Structures

The Plasma β in Quiet Sun Regions: Multi-instrument View

Propagating kink waves in an open coronal magnetic flux tube with gravitational stratification: Magnetohydrodynamic simulation and forward modelling

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