Hobbes on equity

Klimchuk, Dennis

doi:10.1017/cbo9781139137034.009

Cited by 11 publications

(9 citation statements)

References 4 publications

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“…We now have datasets with a much higher cadence than before and we find average recurrence times around magnetic network where RBEs appear of 84 s and a minimum recurrence time of 4.3 seconds in the densest regions. Our results indicate that the conclusions of Klimchuk (2012) are unwarranted, and also highlight the dangers of using simplified models and poorly determined observational characteristics. Figure 3 shows three very different RBE examples of how the Doppler velocity and Doppler width changes with the position along the RBE.…”

Section: Quiet Sun Rbesmentioning

confidence: 85%

“…Using the recurrence rate of one RBE per 500 seconds from De Pontieu et al (2011), Klimchuk (2012) dismissed type II spicules as a sufficient source of hot plasma and energy to heat coronal loops and their importance for the temperature structure in the corona. We now have datasets with a much higher cadence than before and we find average recurrence times around magnetic network where RBEs appear of 84 s and a minimum recurrence time of 4.3 seconds in the densest regions.…”

Section: Quiet Sun Rbesmentioning

confidence: 99%

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On the Temporal Evolution of the Disk Counterpart of Type Ii Spicules in the Quiet Sun

Sekse

Voort

Pontieu

2013

ApJ

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The newly established type II spicule has been speculated to provide enough hot plasma to play an important role in the mass loading and heating of the solar corona. With the identification of Rapid Blueshifted Excursions (RBEs) as the on-disc counterpart of type II spicules we have analysed three different high quality timeseries with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish Solar Telescope (SST) on La Palma and subjected to an automated detection routine to detect a large number of RBEs for statistical purposes. Our observations are of a quiet Sun region at disc centre and we find lower Doppler velocities, 15-40 km s −1 , and Doppler widths, 2-15 km s −1 , of RBEs than in earlier coronal hole studies, 30-50 km s −1 and 7-23 km s −1 , respectively. In addition, we examine the spatial dependence of Doppler velocities and widths along the RBE axis and conclude that there is no clear trend to this over the FOV or in individual RBEs in quiet Sun at disc centre. These differences with previous coronal hole studies are attributed to the more varying magnetic field configuration in quiet Sun conditions. Using an extremely high cadence dataset has allowed us to improve greatly on the determination of lifetimes of RBEs, which we find to range from 5 to 60 s with an average lifetime of 30 s, as well as the transverse motions in RBEs, with transverse velocities up to 55 km s −1 and averaging 12 km s −1 . Furthermore, our measurements of the recurrence rates of RBEs provide important new constraints on coronal heating by spicules. We also see many examples of a sinusoidal wave pattern in the transverse motion of RBEs with periods averaging 54 s and amplitudes from 21.5 to 129 km which agrees well with previous studies of wave motion in spicules at the limb. We interpret the appearance of RBEs over their full length within a few seconds as the result of a combination of three kinds of motions as is earlier reported for spicules. Finally, we look at the temporal connection between Hα and Ca II 8542 RBEs and find that Ca II 8542 RBEs in addition to being located closer to the footpoint also appear before the Hα RBEs. This connection between Ca II 8542 and Hα supports the idea that heating is occurring in spicules and contribute more weight to the prominence of spicules as a source for heating and mass loading of the corona.

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Section: Quiet Sun Rbesmentioning

confidence: 85%

Section: Quiet Sun Rbesmentioning

confidence: 99%

On the Temporal Evolution of the Disk Counterpart of Type Ii Spicules in the Quiet Sun

Sekse

Voort

Pontieu

2013

ApJ

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“…With these preliminary remarks it is fair to say that there is some agreement between different groups [47][48][49][50][51][52] that nanoflares may play a dominate role in heating of solar corona. For example, for the typical parameters assumed in [49] the authors conclude that in order to reproduce the observations the nanoflares must have typical energies W and the frequencies of appearance dN /dt as follows [49]:…”

Section: Recent Advances and Future Developmentmentioning

confidence: 91%

Solar Extreme UV radiation and quark nugget dark matter model

Zhitnitsky

2017

J. Cosmol. Astropart. Phys.

121

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Abstract. We advocate the idea that the surprising emission of extreme ultra violet (EUV) radiation and soft x-rays from the Sun are powered externally by incident dark matter (DM) particles. The energy and the spectral shape of this otherwise unexpected solar irradiation is estimated within the quark nugget dark matter model. This model was originally invented as a natural explanation of the observed ratio Ω dark ∼ Ω visible when the DM and visible matter densities assume the same order of magnitude values. This generic consequence of the model is a result of the common origin of both types of matter which are formed during the same QCD transition and both proportional to the same fundamental dimensional parameter Λ QCD .We also present arguments suggesting that the transient brightening-like "nanoflares" in the Sun may be related to the annihilation events which inevitably occur in the solar atmosphere within this dark matter scenario.

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“…whether it is impulsive or steady (Müller et al 2003(Müller et al , 2004. Forward modelling of numerical results and comparison with EUV light curves obtained in observations have helped answering this question, but a debate exists on whether the heating requirements setting loops in a thermal non-equilibrium state fully match the general observed characteristics of active region loops (Mok et al 2008;Klimchuk et al 2010;Peter et al 2012;Lionello et al 2013;Klimchuk 2014). Coronal rain observations can help answer this question by estimating the coronal volume and mass flux involved in these events.…”

Section: Introductionmentioning

confidence: 99%

The Multi-Thermal and Multi-Stranded Nature of Coronal Rain

Antolin

Vissers

Pereira

et al. 2015

ApJ

117

161

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While the nature of the heating mechanisms in the corona remains elusive their associated cooling is also a poorly known but a far less observationally restrictive subject. In this work, we analyse coordinated observations spanning chromospheric, transition region (TR) and coronal temperatures at very high resolution which reveal essential characteristics of thermally unstable plasmas. Coronal rain is found to be a highly multi-thermal phenomenon with a high degree of co-spatiality in the multi-wavelength emission. EUV darkening and quasi-periodic intensity variations are found to be strongly correlated to coronal rain and especially 'showers'. Progressive cooling of coronal rain is observed, leading to a height dependence of the emission. Furthermore, a fast-slow twostep catastrophic cooling progression is found, which may reflect the transition to optically thick plasma states. The intermittent and clumpy appearance of coronal rain at coronal heights becomes more continuous and persistent at chromospheric heights just before impact, in agreement with previous observations above sunspots. This change of character is mainly due to a funnel effect from the observed expansion of the magnetic field at low heights. Strong density inhomogeneities on spatial scales of 0.2 ′′ − 0.5 ′′ are found, in which TR to chromospheric temperature transition occurs at the lowest detectable scales. The shape of the distribution of coronal rain widths is found to be independent of temperature with peaks close to the resolution limit of each telescope, ranging from 0.2 ′′ to 0.8 ′′ . However we find a sharp increase of clump numbers at the coolest wavelengths and especially at higher resolution, suggesting that the bulk of the rain distribution remains undetected. Rain clumps appear organised in strands. Such structure is not limited to chromospheric temperatures but extends at least to TR temperatures as well, suggesting an important role of thermal instability in the shaping of fundamental loop substructure. At the smallest detected scales

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Hobbes on equity

Cited by 11 publications

References 4 publications

On the Temporal Evolution of the Disk Counterpart of Type Ii Spicules in the Quiet Sun

On the Temporal Evolution of the Disk Counterpart of Type Ii Spicules in the Quiet Sun

Solar Extreme UV radiation and quark nugget dark matter model

The Multi-Thermal and Multi-Stranded Nature of Coronal Rain

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