Rotation of Doppler features in the solar photosphere

Snodgrass, H. B.; Ulrich, R. K.

doi:10.1086/168467

Cited by 246 publications

(204 citation statements)

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“…where 2 =2 ' À77 nHz and 4 =2 ' À57 nHz (Snodgrass & Ulrich 1990), we arrive to the simplest possible description of the coupling coefficients as where @!=@l is the frequency separation along the p-mode ridge. This result is identical to that of Woodard (1989), when his result is reduced to terms linear in the rotational velocity .…”

Section: Mode Coupling Due To Differential Rotationmentioning

confidence: 95%

Modeling Solar Oscillation Power Spectra. I. Adaptive Response Function for Doppler Velocity Measurements

Vorontsov

Jefferies

2005

ApJ

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Improving the accuracy and resolution of helioseismic inversions calls for more accurate modeling of the observational p-mode power spectra from which the solar oscillation frequencies are traditionally measured. We present a new technique of calculating the response function ( leakage matrix) for Doppler velocity measurements that is based largely on an analytical description of the relevant instrumental and physical effects. The computational efficiency of the new approach allows us to implement the response function in an adaptive manner: i.e., the compensation for instrumental or optical distortions of unknown magnitude can be performed as a part of the spectral fitting procedure.

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Section: Mode Coupling Due To Differential Rotationmentioning

confidence: 95%

Modeling Solar Oscillation Power Spectra. I. Adaptive Response Function for Doppler Velocity Measurements

Vorontsov

Jefferies

2005

ApJ

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“…There have been multiple studies of rotation (reviewed by Beck 2000). Interestingly, each method returns different values of the Ω(θ) coefficients, e.g., the equatorial rotation rate A = 453.75 nHz (25.51 days) as measured by spectroscopy and A = 473.01 nHz (24.47 days) as measured by surface tracers (Snodgrass and Ulrich 1990). This might reflect the sensitivity to rotation of each method varying with depth in the Sun.…”

Section: Solar Rotationmentioning

confidence: 99%

“…From the Sun, we know that different methods for measuring rotation, e.g., spot tracing (D 'Silva and Howard 1994) and helioseismology (Schou et al 1998), show the outer envelope of the Sun rotating differentially. The solar surface rotation period changes by 4 Paper III -Constraining differential rotation of Sun-like stars from asteroseismic and starspot rotation periods approximately 2.2 days between the equator and 40 • latitude (Snodgrass and Ulrich 1990), while in the radial direction the rotation period changes by ∼1 day in the outer few percent of the solar radius (Beck 2000). While small on the Sun, differential rotation could be larger on other stars.…”

Section: Introductionmentioning

confidence: 99%

Differential Rotation in Sun-like Stars from Surface Variability and Asteroseismology

Nielsen

2017

Springer Theses

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“…If there is a time difference between two observations we translate all relevant images to the time of the nearest magnetic field data using the differential solar rotation rate described in Snodgrass and Ulrich (1990). Mx (an average field strength of 500 G for a pixel located at disk center).…”

Section: Co-alignmentmentioning

confidence: 99%

Quiescent Reconnection Rate Between Emerging Active Regions and Preexisting Field, with Associated Heating: NOAA AR 11112

et al. 2014

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When magnetic flux emerges from beneath the photosphere it displaces the preexisting field in the corona, and a current sheet generally forms at the boundary between the old and new magnetic domains. Reconnection in the current sheet relaxes this highly stressed configuration to a lower energy state. This scenario is most familiar, and most often studied, in flares, where the flux transfer is rapid. We present here a study of steady, quiescent flux transfer occurring at a rate three orders of magnitude below that in a large flare. In particular we quantify the reconnection rate, and related energy release, occurring as new polarity emerges to form Active Region 11112 (SOL16 October 2010T00:00:00L205C117) within a region of preexisting flux. A bright, low lying kernel of coronal loops above the emerging polarity, observed with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory and the X-ray Telescope onboard Hinode, originally shows magnetic connectivity only between regions of newly emerged flux when overlaid on magnetograms from the Helioseisimic and Magnetic Imager. Over the course of several days, this bright kernel advances into the preexisting flux. The advancement of an easily visible boundary into the old flux regions allows measurement of the rate of reconnection between old and new magnetic domains. We compare the reconnection rate to the inferred heating of the coronal plasma. To our knowledge, this is the first measurement of steady, quiescent heating related to reconnection. We determine that the newly emerged flux reconnects at a fairly steady rate of 0.38 × 10 16 Mx s −1 over two days, while the radiated power varies between (2 ∼ 8) × 10 25 erg s −1 over the same time. We find that as much as 40% of the total emerged flux at any given time may have reconnected. The total amount of transferred flux (∼ 1 × 10 21 Mx) and radiated energy (∼ 7.2 × 10 30 ergs) are comparable to that of a large M-or small X-class flare, but are stretched out over 45 hours.

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Rotation of Doppler features in the solar photosphere

Cited by 246 publications

References 0 publications

Modeling Solar Oscillation Power Spectra. I. Adaptive Response Function for Doppler Velocity Measurements

Modeling Solar Oscillation Power Spectra. I. Adaptive Response Function for Doppler Velocity Measurements

Differential Rotation in Sun-like Stars from Surface Variability and Asteroseismology

Quiescent Reconnection Rate Between Emerging Active Regions and Preexisting Field, with Associated Heating: NOAA AR 11112

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