Tracking Vector Magnetograms with the Magnetic Induction Equation

Schuck, P. W.

doi:10.1086/589434

Cited by 232 publications

(210 citation statements)

References 54 publications

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“…To evaluate the horizontal displacements in the photosphere, we have followed the method described by Schuck (2008) by comparing the magnetic field between two magnetograms taken with a time interval of 12 minutes by means of the Differential Affine Velocity Estimator (Schuck 2005(Schuck , 2006, using an apodization window of 11 pixels (5 5) of full width at half maximum.…”

Section: Resultsmentioning

confidence: 99%

A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

Guglielmino¹,

Zuccarello²,

Romano

et al. 2016

ApJ

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We present an analysis of multi-instrument space-and ground-based observations relevant to a C4.1 solar flare that occurred in the active region (AR) NOAA 11267 on 2011 August 6. Solar Dynamics Observatoryobservations indicate that at the flare's beginning, it was localized in the preceding sunspot of the AR, which exhibits a δ configuration. Along the polarity inversion line between its opposite polarities we find a large shear angle of about 80°. The helicity accumulation shows that the AR does not obey the general hemispheric helicity rule. At the flare peak, unique observations taken with the X-Ray Telescope aboard Hinode reveal that the bulk of the X-ray emission takes place in the δ-spot region, where the plasma heats up to 1.9 10 7 · » K. During the gradual phase, we observe the development of a Y-shaped structure in the corona and in the high chromosphere. An extruding structure forms, being directed from the emitting region above the δ spot toward the following sunspot. This structure cools down in a few tens of minutes while moving eastward along a direction opposite to the flare ribbon expansion. Finally, remote brightenings are found at the easternmost footpoint of this structure, appearing as a third flare ribbon in the chromosphere. After some minutes, RHESSI measurements show that the X-ray emission is localized in the region close to the crossing point of the coronal Y-shaped structure. Simultaneously, highresolution (0 15) observations performed at the Swedish 1 m Solar Telescope indicate a decreasing trend of the Ca II H intensity in the flare ribbons with some transient enhancements. All these findings suggest that this event is a manifestation of magnetic reconnection, likely induced by an asymmetric magnetic configuration in a highly sheared region.

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Section: Resultsmentioning

confidence: 99%

A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

Guglielmino¹,

Zuccarello²,

Romano

et al. 2016

ApJ

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“…Considering HMI provides 45-s cadence and 12-min cadence (lower noise) line-ofsight magnetograms, we chose a time interval of 12 minutes, which is close to 10 minutes, and used 12-min longitude magnetograms in this work. As for the window size, we chose 15 × 15 pixels, taking into account the shapes of the ARs we studied (Welsch et al 2007;Schuck 2008;Tian et al 2011). …”

Section: Methods and Observationsmentioning

confidence: 99%

Asymmetry of Magnetic Helicity Flux in Emerging Bipolar Active Regions

Yang¹,

Jiang²,

Yang³

et al. 2014

Journal of The Korean Astronomical Society

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We apply differential affine velocity estimator (DAVE) to the Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) 12-min line-of-sight magnetograms, and separately calculate the injected magnetic helicity for the leading and the following polarities of nine emerging bipolar active regions (ARs). Comparing magnetic helicity flux of the leading polarity with the following polarity, we find that six ARs studied in this paper have the following polarity that injected more magnetic helicity flux than that of the leading polarity. We also measure the mean area of each polarity in all the nine ARs, and find that the compact polarity tend to possess more magnetic helicity flux than the fragmented one. Our results confirm the previous studies on asymmetry of magnetic helicity that emerging bipolar ARs have a polarity preference in injecting magnetic helicity. Based on the changes of unsigned magnetic flux, we divide the emergence process into two evolutionary stages: (1) an increasing stage before the peak flux and (2) a constant or decreasing stage after the peak flux. Obvious changes on magnetic helicity flux can be seen during transition from one stage to another. Seven ARs have one or both polarity that changed the sign of magnetic helicity flux. Additionally, the prevailing polarity of the two ARs, which injects more magnetic helicity, changes form the following polarity to the leading one.

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“…It is much different from those by LCT and DAVE method. The DAVE4VM method estimates a field aligned plasma velocity from only magnetic field observations, and the DAVE produces a biased estimation of the total horizontal plasma velocity [2] . So we need to analyze the difference between the magnetic helicity derived from different velocity field.…”

Section: Velocity Fields By Different Optical Flow Techniquesmentioning

confidence: 99%

“…Photospheric velocity field is an important parameter in studying solar eruptions. This parameter can be deduced by three kinds of optical flow techniques, i.e., LCT [1] , DAVE and DAVE4VM [2] . By using an example of active region (AR) NOAA 12017, we have compared the distribution of the velocity field and magnetic helicity transport rate which calculated from the velocity field by these three methods.…”

mentioning

confidence: 99%

Three Kinds of Optical Flow Technique: LCT, DAVE and DAVE4VM

Liu¹,

Dong²,

Zheng³

2015

Advances in Computer Science Research

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Abstract. Photospheric velocity field is an important parameter in studying solar eruptions. This parameter can be deduced by three kinds of optical flow techniques, i.e., LCT [1] , DAVE and DAVE4VM [2] . By using an example of active region (AR) NOAA 12017, we have compared the distribution of the velocity field and magnetic helicity transport rate which calculated from the velocity field by these three methods. It is found that, the velocity fields are very similar for the results from LCT and DAVE method, while much different for those from DAVE4VM. However, the helicity transport rates are in similar trend for the results from all methods.

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Tracking Vector Magnetograms with the Magnetic Induction Equation

Cited by 232 publications

References 54 publications

A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

Asymmetry of Magnetic Helicity Flux in Emerging Bipolar Active Regions

Three Kinds of Optical Flow Technique: LCT, DAVE and DAVE4VM

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