Sunspot Proper Motions Research Articles

Sunspot proper motion of individual sunspot in active region 11429 during X5.4 solar flare on March 7, 2012

Based on high resolution images obtained from Helioseismic and Magnetic Imager (HMI) instrument onboard Solar Dynamic Observatory (SDO) satellite at visual wavelength, we traced several individual umbral sunspots to find drift motion during flare occurrences within Active Region (AR) 11429 (N17, E15) at 00:00 to 05:00 UT on March 7, 2012. AR11429 was a large sunspot group with 1270 millionth solar hemisphere in area and complex magnetic morphology with beta-gamma-delta class. We measured relative motion of 22 umbral sunspots positions during eruptive and post-flare phases for about 5 hours. Some sunspots showed faster motion during eruptive phase at about 10% than decay phase and they moved nearly along the magnetic field polarity inversion line that showed shear motion. Flare outburst which is occurred in corona layer affected sunspot motion and area, as seen for their changing configuration and morphology, before and after peaked X-ray intensity. This result indicates that there is a strong connection between X-ray solar flare at corona layer and its foot points motion at photosphere.

Short-period variations in the proper motions of sunspots from SOHO (MDI) observations

Short-period (1–60 min) variations in the coordinates of the centers of gravity of isolated sunspots are analyzed. The sunspot coordinated were determined using two sets of observational data—magnetograms and intensities—obtained by SOHO (MDI) on December 6, 1998, from 01:00 to 21:57 UT with temporal resolution 60 s and spatial resolution 0.6″/pixel. A slow drift in the sunspot coordinates was removed using a low-frequency filter with a 61-min integration window. The guiding errors (RMS∼0.014″) were determined by analyzing correlated motions in pairs of sunspots, and were removed from the time series before determining the sunspot proper motions. Based on the calculated power spectra for the sunspot proper motions, two period intervals containing appreciable power were identified. One coincides with the well-known 5-min acoustic solar oscillations. The concentration of power in this interval is greater for the coordinate variations derived the magnetograms than those derived from the intensities; the harmonic amplitude for some peaks reaches ∼±30 km. The other spectral interval corresponds to periods exceeding 30 min. Overall, the rms short-period variations in the sunspot proper motions are 9.9±2.2 and 16.7±7.6 km (0.014″±0.003″ and 0.024″±0.010″) for the magnetogram and intensity data, respectively.

Emergence of Twisted Magnetic-Flux Bundles and Flare Activity in a Large Active Region, NOAA 4201

Abstract To reveal what is the key agent for strong flare activity, we studied the evolution of a large sunspot group, NOAA 4201, and its flare activity. We analyzed high-resolution Hα images obtained with the Domeless Solar Telescope at Hida Observatory, and Kitt Peak full disk magnetograms. We examined the sunspot proper motions and evolutionary changes of Hα fine structures and magnetic fields in this active region, and constructed a schematic model of emerging twisted magnetic-flux bundles. We also found that the occurrence of high flare activity was restricted to the rapidly emerging region of the twisted flux bundle. This fact suggests that the emergence of a twisted emerging flux bundle should be the key to high flare productivity of the sunspot group.

Sunspot Motions Associated with Flares

The evolution of five bipolar sunspot groups during their disk passage leading to flares are analysed and studied using Kodaikanal Observatory photoheliogram and spectroheliogram data. The changes in the orientation angle observed in the spot groups show that sunspot proper motion plays an important role in introducing non-potential character to the field lines. This in turn develops shear and once the shear reaches a critical value, the flare eruption is triggered. The rotational motions in the sunspots are measured from the change in their orientation angle and are given as a measure of shear. The sunspots considered for analyses in the present study are not associated with any filament activity.

Emergence of a Twisted Magnetic Flux Bundle as a Source of Strong Flare Activity

Sunspot proper motions and flares of a super active region NOAA 5395—the largest and most flare-active region in the 22d sunspot cycle—were analyzed in detail. We measured sunspot proper motions by using the Hα - 5.0 A images obtained with the 60 cm Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University and found some peculiar vortex-like motions of small satellite spots, which successively emerged from the leading edge of this sunspot group. To explain these motions of small sunspots, we proposed a schematic model of the successive emergence of twisted and winding magnetic flux loops coiling around a trunk of a magnetic flux tube. The location of the strongest flare activity was found to coincide with the site of the vortex-like motions of sunspots. We conclude that the flare-productive magnetic shear is produced by the emergence of the twisted magnetic flux bundle. Magnetic energy is stored in the twisted flux bundle, which is originally formed in the convection zone and released as flares in the course of the emergence of the twisted flux bundle above the photosphere.

Local solar magnetic and velocity field development and related photospheric and chromospheric activity

We have compiled the results of our long-term studies of the local magnetic field and its activity development, derived from investigating sunspot group evolution, photoelectrically measured longitudinal magnetic and velocity fields, and measurements of sunspot proper motions. We estimate certain regularities according to which the magnetic and velocity fields, and photospheric, as well as chromospheric activities develop. We speculate about the physical background of such processes.

Sunspot Proper Motion and Flare Frequency

Flare activity of solar active regions is generally believed to depend on a sheared configuration of magnetic fields (Hagyard et al. 1984). There are cases when the shear necessary for a flare can be attributed to the emergence of a new flux in the spot group (Wang 1992). But, perhaps, a newly born active region can also influence the magnetic field configuration in a nearby active region (Poleto et al. 1993, Gesztelyi et al. 1993). In this paper we are interested primarily in the influence of a newly emerging spot group on a nearby one.The three neighbouring active regions NOAA AR 6412(B-C), 6413(A) and 6415(D) have been studied between 13-22 December 1990. White-light pictures for studying sunspot proper motion and area evolution were taken at Gyula Observing Station (Hungary), Debrecen Heliophysical Observatory (Hungary) and Helwan Observatory (Egypt). Times and positions of the flares were taken from the Solar Geophysical Data (No. 558, part 1, February 1991).

Rapid sunspot motion during a major solar flare

A major solar flare on 15 November, 1991 produced a striking perturbation in the position and shape of the sunspot related most closely to the flare. We have studied these perturbations by use of the aspect-sensor images from the Soft X-ray Telescope on board YOHKOH, and with ground-based data from the Mees Solar Observatory. The perturbation occurred during the impulsive phase of the flare, with a total displacement on the order of 1 arc sec. The apparent velocity of approximately 2 km s−1 exceeds that typically reported for sunspot proper motions even in flare events. We estimate that the magnetic energy involved in displacing the sunspot amounted to less than 4 × 1030 ergs, comparable to the radiant energy from the perturbed region. Examination of the Mees Observatory data shows that the spot continued moving at lower speed for a half-hour after the impulsive phase. The spot perturbation appears to have been a result of the coronal restructuring and flare energy release, rather than its cause.

The variation of filament direction in a flaring region

We have analyzed the variations in shear angle over a time interval of 30 s during a flare on June 11, 1991, using Kodaikanal Observatory spectroheliogram and photoheliogram data, and assuming Hα filaments are a proxy for the neutral lines. The changes in shear angles have been analysed at two points of the filament. The orientation of the Hα filament underwent a considerable change of ∼55° from June 10, 1991 to prior to the start of the flare on June 11, 1991. The photoheliogram on June 10, 1991 shows considerable twisting of the umbrae (in one common penumbra) and broke into parts before the onset of the flare on June 11, 1991. The twisting of umbrae on June 10, 1991 shows that sunspot proper motion plays an important role in bringing a non-potential character to the field lines. This in turn develops shear and kink and it is argued that changes in filament orientation over a small interval of a half minute triggers the eruption of the flare.

Area-Weighting of Sunspot Group Positions and Proper Motion Artifacts

AbstractTwo simple examples are presented to show that concepts about the physical nature of sunspot groups may significantly influence the statistical data analysis process. In particular, the second example shows that the well-known difference in the decay rates of preceding (p-) and following (f-) polarity parts of sunspot groups may lead to a fake proper motion effect when area-weighted group positions are used. This effect may be responsible for some recent contradictory findings concerning the motions of sunspot groups. It is therefore argued that while area-weighting is adequate when calculating the mean positions of p- and f-parts of a sunspot group separately, defining the position of the group as a whole by the unweighted average of the mean positions of the p- and f-parts is more satisfactory from the theoretical point of view (whenever it is possible to distinguish between spots of different polarities). Similarly, it is best not to “correct” sunspot proper motions for internal differential rotation within groups.

Sunspot proper motions and behaviour of rising magnetic flux tubes

Greenwich data for proper motions of the components of sunspot groups are analysed. We have found that only 4% of the 408 examined sunspot groups do not show systematic proper motions of the components at the beginning of their life. Interpreting proper motions as the results of ascending sub-photospheric magnetic flux tubes, information on characteristics of the tubes have been deduced. The influence of proper motions on the evaluation of the sunspot rotation rates is discussed.

Sunspot proper motions in active region NOAA 2372 and its flare activity during SMY period of 1980 April 4–13

Solar Active Region NOAA 2372 was observed extensively by the Solar Maximum Mission (SMM) satellite and several ground-based observatories during 1980 April 4–13 in the Solar Maximum Year. After its birth around April 4, it underwent a rapid growth and produced a reported 84 flares in the course of its disc passage. In this paper, we have studied photospheric and chromospheric observations of this active region together with Marshall Space Flight Center magnetograms and X-ray data from HXIS aboard the SMM satellite. In particular, we discuss the relationship of the flare-productivity with sunspot proper motions and emergence of new regions of magnetic flux in the active region from its birth to its disappearance at the W-limb.

Sunspot proper motions in connection with the white-light flare of 25 April 1984

During the descending phase of the present cycle of solar activity one of the largest events was the 3B/X13.0 white-light flare in NOAA Active Region No. 4474 near the eastern limb on 24/25 April 1984. We present a study of the evolution of the very complex and extended active region 4474, the proper motion of the sunspots and the changes in the magnetic field in connection with the large flare, with special emphasis on the magnetic shear and other possible types of motion leading to flare build-up, and following the flare.

Material motions in sunspot umbrae

view Abstract Citations (97) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Material motions in sunspot umbrae. Beckers, J. M. Abstract Material motions in the umbrae of a number of sunspots have been measured on an absolute scale by means of the g = 0 line of Ti I at 5713 A. It is found that the rates of solar rotation as derived from sunspot proper motions and from spectra are identical to within 1% and that the vertical flow inside umbrae is small, being less than 25 m/s when the pressure shift is ignored. The so-called limb effect is absent in the umbrae leading to an upper limit to the convective energy flux of 0.5% of the radiative energy flux outside sunspots. The position of the line with respect to its laboratory wavelengths is shifted to the red by 613 m/s, in agreement with the predicted gravitational redshift of 636 m/s. Publication: The Astrophysical Journal Pub Date: May 1977 DOI: 10.1086/155222 Bibcode: 1977ApJ...213..900B Keywords: Solar Gravitation; Solar Rotation; Sunspots; Umbras; Convective Flow; Doppler Effect; Radiant Flux Density; Red Shift; Solar Limb; Solar Spectra; Solar Physics full text sources ADS |

Reliability of sunspots as tracers of solar surface rotation

NEW methods of measuring solar rotation have produced significantly different rotation speeds to those derived from sunspots1,2. Spectroscopic measurements of Doppler displacements give a so-called plasma rotation velocity of 13.76° d−1 (sidereal) at the solar equator3 as against 14.38 ° d−1 (sidereal) from sunspot proper motion velocity4,5. Other techniques of measuring solar rotation lead to differences in the differential rotation from a strong variation of the solar rotation with latitude for sunspots4 and photospheric plasma3 to hardly any variation at all for coronal holes6. Our understanding of these differences is very poor. It is therefore appropriate to obtain additional accurate solar rotation measurements with as many different techniques as possible and to check the validity of the assumption that the proper motion of tracers, like sunspots, correspond to the actual motion of matter on the solar surface. We report here the result of plasma rotation velocity measurements inside sunspot umbrae and their relation to the rotation velocities derived from spot proper motions. We find that plasmas inside and outside the spots rotate at similar rates, and conclude that sunspots make poor tracers.

The proper motions of sunspots and the magnetic field of active regions

According to our program of sunspot proper motion investigations (Kuklin and Syklen, 1966) we study the interdependence of the sunspot proper motions inside the group and the magnetic field of the whole group or active region. This aspect of the dynamics of matter in disturbed regions of the Sun was not considered practically up to the last time.