Solar coronal rotation determined by X-ray bright points  in Hinode/XRT and Yohkoh/SXT 
full-disc images

Kariyappa, R.

doi:10.1051/0004-6361:200809598

Cited by 29 publications

(36 citation statements)

References 18 publications

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“…Kariyappa (2008) and Hara (2009) both measured the rotation velocity of coronal bright points in Yohkoh/SXT images during mostly overlapping time periods. However, the rotation results, especially at the solar equator, differ significantly (lines 3 and 4 in Table 16).…”

Section: A Comparison With Other Datamentioning

confidence: 99%

A precise measurement of the solar differential rotation by tracing small bright coronal structures in SOHO-EIT images

Wöhl¹,

Brajša²,

Hanslmeier³

et al. 2010

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Aims. We precisely determine the solar rotation velocity during most of the 23rd solar cycle, in the years 1998−2006. We measure the solar differential rotation by tracing small bright coronal structures (SBCS) in SOHO-EIT images. Methods. The 28.4 nm EIT channel was used and positions of more than 55 000 structures were measured applying an interactive and improved automatic method of data reduction. Results. We achieve the closest representation of the observational data when all three solar differential rotation parameters are used and obtain the formula ω (b) = 14.499(±0.006) − 2.54(±0.06) sin 2 b − 0.77(±0.09) sin 4 b. This result represents the sidereal rotation velocity in deg day −1 and is produced by the automatic method applied in 1998−2006. A north-south rotational asymmetry and a rigid component of the solar rotation at high latitudes were found. Conclusions. A more differential rotation profile of SBCS than of sunspots and sunspot groups was found. The rotation velocity of SBCS is very similar to those obtained by small photospheric magnetic features. The north-south rotational asymmetry of SBCS was interpreted with a model of the relationship between solar rotation and activity. The rigid component of the solar rotation at high latitudes, identifiable only from the results of the automatic method, was related to larger structures mostly identified by that method, in contrast to the interactive method, which detected smaller structures.

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Section: A Comparison With Other Datamentioning

confidence: 99%

A precise measurement of the solar differential rotation by tracing small bright coronal structures in SOHO-EIT images

Wöhl¹,

Brajša²,

Hanslmeier³

et al. 2010

A&A

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“…Coronal bright points (CBPs) have also been used very frequently by using the data obtained by different satellites. For example, Brajša et al (2001Brajša et al ( , 2002bBrajša et al ( , 2004, Vršnak et al (2003), Wöhl et al (2010) used SOHO/EIT data, Hara (2009) analysed Yohkoh/SXT measurements, while Kariyappa (2008) used both Yohkoh and Hinode data. Recently, Sudar et al (2015) have used SDO/AIA measurements in the 19.3 nm channel.…”

Section: Introductionmentioning

confidence: 99%

Meridional motions and Reynolds stress from SDO/AIA coronal bright points data

Sudar

Saar

Skokić

et al. 2016

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Context. It is possible to detect and track coronal bright points (CBPs) in Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) images. A combination of high resolution and high cadence provides a wealth of data that can be used to determine velocity flows on the solar surface with very high accuracy. Aims. We derived a very accurate solar rotation profile and investigated meridional flows, torsional oscillations, and horizontal Reynolds stress based on ≈6 months of SDO/AIA data. Methods. We used a segmentation algorithm to detect CBPs in SDO/AIA images. We also used invariance of the solar rotation profile with central meridian distance (CMD) to determine the height of CBPs in the 19.3 nm channel. Results. The best fit solar rotation profile is given by ω(b) = (14.4060 ± 0.0051 + (−1.662 ± 0.050) sin 2 b + (−2.742 ± 0.081) sin 4 b) • day −1 . The height of CBPs in the SDO/AIA 19.3 nm channel was found to be ≈6500 km. Meridional motion is predominantly poleward for all latitudes, while solar velocity residuals show signs of torsional oscillations. Horizontal Reynolds stress was found to be smaller than in similar works, but still showed transfer of angular momentum towards the solar equator. Conclusions. Most of the results are consistent with Doppler measurements rather than tracer measurements. The fairly small calculated value of horizontal Reynolds stress might be due to the particular phase of the solar cycle. Accuracy of the calculated rotation profile indicates that it is possible to measure changes in the profile as the solar cycle evolves. Analysis of further SDO/AIA CBP data will also provide a better understanding of the temporal behaviour of the rotation velocity residuals, meridional motions, and Reynolds stress.

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“…Previous investigations have studied the coronal rotation at several wavelengths using different tracers in white light (Hansen et al 1969;Fisher & Sime 1984;Nash 1991;Lewis et al 1999), Fe xiv 5303 Å green line (Sime et al 1989;Rybák 1994;Wang et al 1997;Altrock 2003), near infrared (Insley et al 1995), microwave (Aschwanden et al 1995), EUV and X-ray (Timothy et al 1975;Weber et al 1999;Brajša et al 2002;Karachik et al 2006;Kariyappa 2008;Hara 2009) or through extrapolation of photospheric magnetic field data (Hoeksema & Scherrer 1987;Nash et al 1988). With the accrual of coronagraph data from the telescopes aboard the Solar and Heliospheric Observatory (SOHO; Domingo et al 1995) spacecraft, which allows one to probe the rotation rate of the entire solar corona, it is now possible to study the temporal variation in the coronal rotation rate for a whole solar cycle.…”

Section: Introductionmentioning

confidence: 99%

Coronal equatorial rotation during solar cycle 23: radial variation and connections with helioseismology

Mancuso

Giordano

2012

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Time-series observations of the O vi 1032 Å spectral line intensity provided by the UltraViolet Coronagraph Spectrometer (UVCS) telescope aboard the Solar and Heliospheric Observatory (SOHO) spacecraft have been analyzed to establish the rotational characteristics of the equatorial solar corona as a function of height and time during solar cycle 23. Overall, the coronal rotation period is observed to vary considerably from 1996 to 2006, with episodes of sudden acceleration and deceleration. On average, the rotation period in the equatorial corona tends to increase radially by ∼0.2 days/R from 1.6 to 3.0 R . An anticorrelation throughout the solar cycle is observed between the radial gradients in the inner corona ( < ∼ 2.2 R ), where the magnetic pressure dominates and the plasma is more rigidly connected, and the outer corona ( > ∼ 2.4 R ), where the field lines open up. Around the equator, the extended corona is found to rotate faster than the underlying photosphere, but its rotation rate is comparable to that estimated within the subphotospheric layers in the outer 5% of the Sun. Moreover, a striking significant positive correlation (r = 0.629 at the 0.99 R level) has been discovered between the variations in the residual rotation rates of the coronal and subphotospheric equatorial plasma, at least down to 0.95 R . This correlation suggests that the observed variations in the coronal rotation rate reflect the dynamic changes inferred within the near-surface shear layer, where the tracer structures responsible for the observed coronal emission are thus most probably anchored. These results raise the possibility that the plasma in the upper layers of the solar convection zone, at least around the equator, may be tightly connected to the plasma in the extended corona and that the deeper layers in the Sun might thus directly influence the dynamic evolution of the solar wind.

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Solar coronal rotation determined by X-ray bright points in Hinode/XRT and Yohkoh/SXT full-disc images

Cited by 29 publications

References 18 publications

A precise measurement of the solar differential rotation by tracing small bright coronal structures in SOHO-EIT images

A precise measurement of the solar differential rotation by tracing small bright coronal structures in SOHO-EIT images

Meridional motions and Reynolds stress from SDO/AIA coronal bright points data

Coronal equatorial rotation during solar cycle 23: radial variation and connections with helioseismology

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