Semantische Analyse

Wilhelm, Reinhard; Maurer, Dieter

doi:10.1007/978-3-662-00077-9_8

Cited by 10 publications

(12 citation statements)

References 2 publications

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“…Generally, it is reported that the QS and CH start to show intensity contrast only if the temperature exceeds 6× 10 5 K (Wilhelm 2000;Stucki et al 2000Stucki et al , 2002Cranmer 2009). Therefore, it is often difficult to isolate CH regions from QS without taking recourse to coronal images.…”

Section: Discussionmentioning

confidence: 99%

Quiet-Sun and Coronal Hole in Mg II k Line as Observed by IRIS

Kayshap¹,

Tripathi²,

Solanki

et al. 2018

ApJ

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Coronal holes (CHs) regions are dark in comparison to the quiet-Sun (QS) at the coronal temperatures. However, at chromospheric and transition region (TR) temperatures, QS and CHs are hardly distinguishable. In this study we have used the Mg II 2796.35Å spectral line recorded by the Interface Region Imaging Spectrometer (IRIS) to understand the similarities and differences in the QS and CH at chromospheric levels. Our analysis reveals that the emission from Mg II k3 & k2v that originates in the chromosphere is significantly lower in CH than in QS for the regions with similar magnetic field strength. The wing emissions of Mg II k that originates from the photospheric layer, however, do not show any difference between QS and CH. The difference in Mg II k3 intensities between QS and CH increases with increasing magnetic field strength. We further studied the effects of spectral resolution on these differences and found that the difference in the intensities decreases with decreasing spectral resolution. For a arXiv:1807.03494v2 [astro-ph.SR] 20 Nov 2018 -2resolution of 11Å, the difference completely disappears. These findings are not only important for mass and energy supply from the chromosphere to the corona but also provides essential ingredients for the modelling of the solar spectral irradiance for the understanding of the Sun-climate relationships.

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Section: Discussionmentioning

confidence: 99%

Quiet-Sun and Coronal Hole in Mg II k Line as Observed by IRIS

Kayshap¹,

Tripathi²,

Solanki

et al. 2018

ApJ

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“…Although jets of similar size have been reproduced in one-and two-dimensional numerical simulations, most often driven by the velocity or pressure pulse in the upper chromosphere, the actual physical mechanism driving macrospicules remains unknown (Shibata 1982;Andreev & Kosovichev 1994;Murawski et al 2011). In particular, it is still a matter of discussion whether macrospicules are just rare occurrences of oversized spicules, or whether they are produced by an essentially different mechanism (Moore et al 1977;Blake & Sturrock 1985;Shibata et al 1992a;Sterling 2000;Wilhelm 2000;Yamauchi et al 2004).…”

Section: Introductionmentioning

confidence: 99%

What is a Macrospicule?

Loboda

Богачев

2019

ApJ

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Macrospicules are typically described as solar jets that are larger and longer-lived than spicules, and visible mostly in transition-region spectral lines. They show a broad variation in properties, which pose substantial difficulties for their identification, modelling, and the understanding of their role in the mass and energy balance of the solar atmosphere. In this study, we focused on a sub-population of these jets that undergo parabolic trajectories when observed in the He II 304Å line using high-cadence observations of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) to accumulate a statistically significant sample, which included 330 such events. We found these jets to be typically narrow (3-6 Mm), collimated flows of plasma, which reach heights of about 25 Mm, thus being among the smallest jets observed in the extreme ultraviolet (EUV). Combined with the rise velocities of 70-140 km s −1 and lifetimes of around 15 min, this makes them plausible candidates for the EUV counterpart of type II spicules. Moreover, we have found their dynamics to be inconsistent with a purely ballistic motion; instead, there is a strong correlation between the initial velocities and decelerations of the jets, which indicates that they may be driven by magneto-acoustic shocks with a dominant period of 10 ± 2 min. This makes these EUV jets similar in their dynamics to the conventional, or type I spicules, thus justifying the name of macro-spicules in this case, while a substantial difference in the shock periods (1-2 min for the chromospheric jets) suggests a dissimilarity in the formation conditions.

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“…These dynamic jet-like features dominate the solar limb and since their first reports they have been challenging to explain, as attested in various reviews (Beckers 1968;Sterling 2000;Tsiropoula et al 2012). Over the last decades spicules have been observed in a variety of filters and instruments (e.g Dere et al 1989;Wilhelm 2000;Zachariadis & Gontikakis 2002;O'Shea et al 2005), but the contribution of the Hinode mission (Kosugi et al 2007) has been nothing short of revolutionary. From high quality time series of spicules in the Ca II H band of the Solar Optical Telescope (SOT, Tsuneta et al 2008;Suematsu et al 2008) it emerged that there are at least two types of spicules (De Pontieu et al 2007).…”

Section: Introductionmentioning

confidence: 99%

AN INTERFACE REGION IMAGING SPECTROGRAPH FIRST VIEW ON SOLAR SPICULES

Pereira

Pontieu

Carlsson

et al. 2014

ApJ

134

128

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Solar spicules have eluded modelers and observers for decades. Since the discovery of the more energetic type II, spicules have become a heated topic but their contribution to the energy balance of the low solar atmosphere remains unknown. Here we give a first glimpse of what quiet Sun spicules look like when observed with NASA's recently launched Interface Region Imaging Spectrograph (IRIS). Using IRIS spectra and filtergrams that sample the chromosphere and transition region we compare the properties and evolution of spicules as observed in a coordinated campaign with Hinode and the Atmospheric Imaging Assembly. Our IRIS observations allow us to follow the thermal evolution of type II spicules and finally confirm that the fading of Ca II H spicules appears to be caused by rapid heating to higher temperatures. The IRIS spicules do not fade but continue evolving, reaching higher and falling back down after 500 − 800 s. Ca II H type II spicules are thus the initial stages of violent and hotter events that mostly remain invisible in Ca II H filtergrams. These events have very different properties from type I spicules, which show lower velocities and no fading from chromospheric passbands. The IRIS spectra of spicules show the same signature as their proposed disk counterparts, reinforcing earlier work. Spectroheliograms from spectral rasters also confirm that quiet Sun spicules originate in bushes from the magnetic network. Our results suggest that type II spicules are indeed the site of vigorous heating (to at least transition region temperatures) along extensive parts of the upward moving spicular plasma.

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Semantische Analyse

Cited by 10 publications

References 2 publications

Quiet-Sun and Coronal Hole in Mg II k Line as Observed by IRIS

Quiet-Sun and Coronal Hole in Mg II k Line as Observed by IRIS

What is a Macrospicule?

AN INTERFACE REGION IMAGING SPECTROGRAPH FIRST VIEW ON SOLAR SPICULES

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