Global conditions in the solar corona from 2010 to 2017

Morgan, Huw; Taroyan, Y.

doi:10.1126/sciadv.1602056

Cited by 42 publications

(37 citation statements)

References 70 publications

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“…The inferred T e values in streamers and closed field line regions range from 1.2 to 1.4 ×10 6 K. These T e values are consistent with the quiet sun regions inferred by SDO/AIA below 1.2 R , but are far lower than the typical active region temperatures of 2 − 4 × 10 6 K (e.g. Dudok de Wit et al 2013;Morgan & Taroyan 2017). This difference is likely caused by observational selection effects that are very different in optical versus EUV observations.…”

Section: Spatial Distribution Of T Esupporting

confidence: 79%

“…Ultraviolet and Extreme Ultraviolet (EUV) spectroscopy can be used to infer T e in the chromosphere and low corona (< 1.5 R ) from remote sensing observations of ionic emission lines (e.g. Habbal et al 1993;Raymond et al 1997;Morgan & Taroyan 2017). Coronal T e 's inferred from these studies typically range from 1 to 4 × 10 6 K. Particle detectors in situ, such as SWICS on Ulysses and ACE, have inferred coronal T e via measurements of charge to mass ratios of solar wind plasma (Gloeckler et al, 1992(Gloeckler et al, , 1998.…”

Section: Introductionmentioning

confidence: 99%

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CME-induced Thermodynamic Changes in the Corona as Inferred from Fe xi and Fe xiv Emission Observations during the 2017 August 21 Total Solar Eclipse

Boe

Habbal

Druckmüller

et al. 2020

ApJ

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We present the first remote sensing observations of the impact from a Coronal Mass Ejection (CME) on the thermodynamic properties of the solar corona between 1 and 3 R . Measurements of the Fe xi (789.2 nm) and Fe xiv (530.3 nm) emission were acquired with identical narrow-bandpass imagers at three observing sites during the 2017 August 21 Total Solar Eclipse. Additional continuum imagers were used to observe K+F corona scattering, which is critical for the diagnostics presented here. The total distance between sites along the path of totality was 1400 km, corresponding to a difference of 28 minutes between the times of totality at the first and last site. These observations were used to measure the Fe xi and Fe xiv emission relative to continuum scattering, as well as the relative abundance of Fe 10+ and Fe 13+ from the line ratio. The electron temperature (Te) was then computed via theoretical ionization abundance values. We find that the range of Te is 1.1 − 1.2 × 10 6 K in coronal holes and 1.2 − 1.4 × 10 6 K in streamers. Statistically significant changes of Te occurred throughout much of the corona between the sites as a result of serendipitous CME activity prior to the eclipse. These results underscore the unique advantage of multi-site and multi-wavelength total solar eclipse observations for probing the dynamic and thermodynamic properties of the corona over an uninterrupted distance range from 1 to 3 R .

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Section: Spatial Distribution Of T Esupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

CME-induced Thermodynamic Changes in the Corona as Inferred from Fe xi and Fe xiv Emission Observations during the 2017 August 21 Total Solar Eclipse

Boe

Habbal

Druckmüller

et al. 2020

ApJ

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“…Morgan & Taroyan (2017) suggest that this high temperature component also leads to a solar cyclic variation in the EM distribution below log T=6.2 (1.6 MK); however, a separate analysis of EVE spectra reports that there is no variation with the solar cycle at these temperatures (Schonfeld et al 2017). Our results are consistent with Schonfeld et al (2017): as Figure 3 shows, the EM distribution is very similar up to at least log T=6.15 at all times.…”

Section: Emission Measure Distributionssupporting

confidence: 79%

“…Indeed Brooks et al (2009) suggest that it has a universal character, driven by the radiating and conducting properties of the plasma. In this picture, the explanation for the different distribution near solar maximum found by Morgan & Taroyan (2017), is that the observations at this time are not of truly quiet Sun. The EM distribution averaged over regions of quiet Sun peaks at 1.1 MK and has fallen by two orders of magnitude already by 2 MK; see, for example, Figure 6 of Brooks et al (2009).…”

Section: Emission Measure Distributionsmentioning

confidence: 76%

Solar Cycle Observations of the Neon Abundance in the Sun-as-a-star

Brooks

Baker

Driel-Gesztelyi

et al. 2018

ApJ

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Properties of the Sun's interior can be determined accurately from helioseismological measurements of solar oscillations. These measurements, however, are in conflict with photospheric elemental abundances derived using 3D hydrodynamic models of the solar atmosphere. This divergence of theory and helioseismology is known as the "solar modeling problem." One possible solution is that the photospheric neon abundance, which is deduced indirectly by combining the coronal Ne/O ratio with the photospheric O abundance, is larger than generally accepted. There is some support for this idea from observations of cool stars. The Ne/O abundance ratio has also been found to vary with the solar cycle in the slowest solar wind streams and coronal streamers, and the variation from solar maximum to minimum in streamers (∼0.1-0.25) is large enough to potentially bring some of the solar models into agreement with the seismic data. Here we use daily sampled observations from the EUV Variability Experiment on the Solar Dynamics Observatory taken in 2010-2014, to investigate whether the coronal Ne/O abundance ratio shows a variation with the solar cycle when the Sun is viewed as a star. We find only a weak dependence on, and moderate anti-correlation with, the solar cycle with the ratio measured around 0.2-0.3 MK falling from 0.17 at solar minimum to 0.11 at solar maximum. The effect is amplified at higher temperatures (0.3-0.6 MK) with a stronger anti-correlation and the ratio falling from 0.16 at solar minimum to 0.08 at solar maximum. The values we find at solar minimum are too low to solve the solar modeling problem.

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“…Importantly, a basal flux of Alfvénic waves is a crucial requirement for any mechanism to be considered as a major component in the heating of quiescent and open field regions in the Sun's atmosphere, where the temperature and emission measure are relatively homogenous [27]. Using the wave measurements from SDO, an order of magnitude estimate for the observed Alfvénic wave energy flux in quiescent and coronal holes is 50-80 Wm -2 (see Supplementary Text section 2), which falls below the standard values for coronal radiative losses (100-200 Wm -2 ).…”

mentioning

confidence: 99%