Response of the solar atmosphere to magnetic field evolution in a coronal hole region

Yang, Shuhong; Zhang, J.; Jin, Chuangui; Li, L. P.; Duan, HongYu

doi:10.1051/0004-6361/200810601

Cited by 22 publications

(9 citation statements)

References 118 publications

(140 reference statements)

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“…Based on Hinode observations, de Wijn et al (2008) found that some of the magnetic elements are associated with the chromospheric cell grains. Recently, although no obvious correlation between the magnetic flux density and the Ca ii H internetwork brightness was obtained, Yang et al (2009) were still inclined to believe that there should be a correlation between the two, and they attributed the lack of correlation to the low cadence of Ca ii H images they used.…”

Section: Nature Of Internetwork Grainsmentioning

confidence: 99%

Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

Potts

Marsch

Attié

et al. 2010

A&A

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Aims. We study horizontal supergranule-scale motions revealed by TRACE observation of the chromospheric emission, and investigate the coupling between the chromosphere and the underlying photosphere. Methods. A highly efficient feature-tracking technique called balltracking has been applied for the first time to the image sequences obtained by TRACE (transition region and coronal explorer) in the passband of white light and the three ultraviolet passbands centered at 1700 Å, 1600 Å, and 1550 Å. The resulting velocity fields have been spatially smoothed and temporally averaged in order to reveal horizontal supergranule-scale motions that may exist at the emission heights of these passbands. Results. We find indeed a high correlation between the horizontal velocities derived in the white-light and ultraviolet passbands. The horizontal velocities derived from the chromospheric and photospheric emission are comparable in magnitude. Conclusions. The horizontal motions derived in the UV passbands might indicate the existence of a supergranule-scale magnetoconvection in the chromosphere, which may shed new light on the study of mass and energy supply to the corona and solar wind at the height of the chromosphere. However, it is also possible that the apparent motions reflect the chromospheric brightness evolution as produced by acoustic shocks which might be modulated by the photospheric granular motions in their excitation process, or advected partly by the supergranule-scale flow towards the network while propagating upward from the photosphere. To reach a firm conclusion, it is necessary to investigate the role of granular motions in the excitation of shocks through numerical modeling, and future high-cadence chromospheric magnetograms must be scrutinized.

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Section: Nature Of Internetwork Grainsmentioning

confidence: 99%

Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

Potts

Marsch

Attié

et al. 2010

A&A

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“…The EUV Imaging Spectrograph (EIS) can detect changes in outflow velocities expected from the changing loop magnetic topologies (Culhane et al, 2007), and the X-ray Telescope (XRT, Golub et al, 2007) can observe the changes in loop brightness and temperature at CHB reconnection sites. Related Hinode studies of flux emergence and flux cancellation at a CHB (Yang et al, 2009) and of outflows from an active region edge at a CHB (Sakao et al, 2007) did not use the full Hinode instrument suite, which could advance our understanding of the sources of the slow solar wind and of open field transport through CHB studies. …”

Section: Reconnection At Chbsmentioning

confidence: 99%

TRACE Observations of Changes in Coronal Hole Boundaries

2010

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Solar coronal holes (CHs) are large regions of the corona magnetically open to interplanetary space. The nearly rigid north -south CH boundaries (CHBs) of equatorward extensions of polar CHs are maintained while the underlying photospheric fields rotate differentially, so interchange magnetic reconnection is presumed to be occurring continually at the CHBs. The time and size scales of the required reconnection events at CHBs have not been established from previous observations with soft X-ray images. We use TRACE 195 Å observations on 9 December 2000 of a long-lived equatorial extension of the negativepolarity north polar CH to look for changes of 5 arcsec to > 20 arcsec at the western CHB. Brightenings and dimmings are observed on both short (≈ 5 minutes) and long (≈ 7 hours) time scales, but the CHB maintains its quasi-rigid location. The transient CHB changes do not appear associated with either magnetic field enhancements or the changes in those field enhancements observed in magnetograms from the Michelson Doppler Imager (MDI) on SOHO. In seven hours of TRACE observations we find no examples of the energetic jets similar to those observed to occur in magnetic reconnection in polar plumes. The lack of dramatic changes in the diffuse CHB implies that gradual magnetic reconnection occurs high in the corona with large ( 10°) loops and/or weak coronal fields. We compare our results with recent observations of active regions at CHBs. We also discuss how the magnetic polarity symmetry surrounding quasi-rigid CHs implies an asymmetry in the interchange reconnection process and a possible asymmetry in the solar wind composition from the eastern and western CHB source regions.

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“…They are known as prominences when they are Figure 1.2: Variation of temperature and density with height from photosphere to corona. Image is taken from Yang et al (2009). seen above the solar limb, as shown in Fig.…”

Section: What Are Prominences?mentioning

confidence: 99%

A study of quiescent prominences using SDO and STEREO data

Panesar¹

2014

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Solar prominences are spectacular features on the Sun. They have been investigated for many decades, but the structure and dynamics of prominences is still not fully understood. They are highly dynamic and relatively cool compared with the surrounding corona. On the solar limb, they appear as a huge sheet of plasma. They are known as filaments when observed as dark, thin ribbon-like structures on the solar disk. Prominences usually lie above the magnetic polarity inversion lines. They are mainly of two types: Active region prominences, which are found near the active regions, and quiescent prominences (QP), which are found between the diffused active region boundaries. QPs are more stable than the active region prominences. Polar crown prominences (PCP) are high latitude quiescent prominences. They often appear as chains of chromospheric plasma and thick pillars. Some theoretical models have been proposed to explain the magnetic structure and stability of prominences. High resolution observations are needed, however, for the better understanding of prominence structure and verifying theoretical models. In the beginning, they were mainly observed in Hα line at 6563Å but now prominences are more often observed in extreme ultra violet (EUV) wavelengths. This allows the researchers to study a broader range of prominence characteristics. With the launch of the Solar Dynamic Observatory (SDO), we have excellent high resolution images for the study of structure and dynamics of prominences. This thesis mainly focuses on the study of quiescent prominences. The structure and flows of quiescent prominences have been investigated. For this purpose, SDO images with high spatial and temporal resolution have been used. The Solar Terrestrial Relations Observatory (STEREO) data has been combined with the SDO data to infer the threedimensional geometry of prominences when the spacecraft were roughly 90 degrees to the Earth-Sun line. This separation angle is extremely useful to study prominences which are observed by SDO on limb and simultaneously seen as filaments on the solar disk from the STEREO-Ahead spacecraft. Two different types of quiescent prominences are investigated; one polar crown prominence and the other rather active, tornado-like quiescent prominence. The structure and evolution of the PCP is investigated in detail. It is found that the prominence pillars are separated by many tens of Mm. They are connected with each other by dynamic bridges of cold and hot plasma, that can be seen in 304/171 Å images. The SDO images show strong upflows in the prominence pillars and indicate the presence of a coronal cavity. The STEREO-A disk images show a region of reduced emission in the filament channel that coincides the coronal cavity. The STEREO-A timeseries images show no variation in the region of reduced emission which may be an additional signature of the cavity on the disk. Several small-scale brightenings in the filament channel are observed. The arrival of diffused active region positive flux plays an important role in ...

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Response of the solar atmosphere to magnetic field evolution in a coronal hole region

Cited by 22 publications

References 118 publications

Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

Horizontal supergranule-scale motions inferred from TRACE ultraviolet observations of the chromosphere

TRACE Observations of Changes in Coronal Hole Boundaries

A study of quiescent prominences using SDO and STEREO data

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