Presentation on theme: "Bach ground: The correlation between sunspot proper motion and flares has been investigated for a long time (e.g. Antalova, 1965, Gesztelyi, 1984). The."— Presentation transcript:
Bach ground: The correlation between sunspot proper motion and flares has been investigated for a long time (e.g. Antalova, 1965, Gesztelyi, 1984). The fast motion often connected with flare activity. The acceleration in the proper motion is correlated in time to the occurence of flares in the neighborhood of the spots. Dezs¨o et al. (1980) found that some sunspots showed abrupt change in both speed and direction of proper motion in the phase of flare maximum. The very striking change in position and shape of sunspots close to a flare during the impulsive phase was found by Anwar et al. (1993), and explained as the evidence of energy release location. It has been suggested that proper motion of sunspot is regarded as a flare precursor, since the proper motion led to magnetic energy build up. Many major flares took place on a region where their spots show large proper motion (Ambastha & Bhatnagar, 1988; Dezs¨o et al.,1980). It is clear that any change in proper motion of sunspots may have close correlation with flare occurence. This implies the the flare prediction could be made by measuring the spot proper motion However, precursor events, especially in a few hours before the flare onset has not been known. The precursor mechanism triggering flare in the short period before flare onset is still unknown. In studying the proper motion of sunspot in short time scale before flare onset, we seek to any change in spot motion just before flare. This should give us the preliminary indicator in predicting the flare onset, and may allow us to find the timing of energy build up or release. Change in Sunspot Proper Motion and Its Relation to Flare Onset C.Y. Yatini (LAPAN) and Y. Suematsu (NAOJ) ABSTRACT: From the detailed measurements of motion of sunspots in six active regions, we found that some spots, which are located on flaring area, underwent a particular motion when compared with other spots in the same active region. These spots showed a 'turn' in their moving direction before flare started. The change in motion started in 0.5 to 2.5 hours before flare onset. We found the relation that if the spot shows a 'particular‘ motion, a flare occurs on this particular spot region. On the other hand, any sunspots in non-flaring active region do not show peculiar motion. In some cases, the particular spots also show the motion consistent with a rising emerging flux tube in which pair of spots move away from each other. It is likely that the peculiar motion of spots implies the rising motion of flux tube perturbed by unknown reason. From this study, we expect that SOLAR-B/SOT will be able to reveal the detailed relation between the sunspot motion, related magnetic activity and flare onset, making a short term prediction of flare occurrence possible. P60 Method of Data Analysis Tracking spots Local Cross-correlation ; - forward tracking - backward tracking Spot’s center of gravity to get reliable result, since the spot displacement is small and the image is affected by variable atmospheric seeing. NOAA 8100 on Nov 3, 1997 On 1997 November 3, the active region NOAA 8100 produced an SB/C8.6 flare. In the tracking of spots movement, we divided this active region into 3 groups (labeled A, B and C). Each spots movement is measured against its group. In group A the positive polarity spots are spots 2, 3, 5, 6, 7, 8, 9, and 10; in group B are nos 5 and 6; in group C is spot 2. Others than those are negative ones. Spots A2, C9 and C10 were appeared at about 01:30 UT or about 2.5 hours before flare onset. Solid vertical lines represent flare onset time. Arrows show the timing of the disturbance in spots movement. Active region NOAA 7912 on October 13, 1995. Spots are marked with number 2 -11 in the tracking of their movement. The ensemble of spots group (box no 1) is used as the reference. The displacement plots of spot no 2 (dotted line), 4 (dashed), 5 (solid), 6 (dash dot), 10 (dash dot dot) and 11(long dash). Solid vertical line represents the flare onset time. Arrows show the ’turning’ time of spot 5. Left is the result of forward, right is of backward tracking. Active region NOAA 8395 (fig 17) produced a 3N/X3.3 class flare on November 28, 1998. We divided the tracking of spots in two parts. In part A, we measured the spots displacement with the reference of area A. In this area spots no A8, A9, and A10 are negative polarity spots, while the others are positive. In the second part (B), we measured the spots outside of area A using spot A2 as the reference. NOAA 8123 on 1997 December 18: The spots displacement in non flaring period of active region also analyzed as well as the flaring active region. The result is used as the comparison of the movement of spots in flaring region. We used area 1, which including spots 2, 3, and 4, as the reference. There were three spots in the boxed area, and labeled as no 2 - 4. All spots is negative polarity. The spot located on west side of this box has positive polarity. In this figure, the spots kept their moving direction during the observation. The spot which has biggest displacement is spot no 2, but it did not show any remarkable change in its movement. Conclusion and Discussion: We have studied the spots displacement in some active regions before flare onset. In the result of the measurement we bring a new view about the proper motion of spots in a short term scale before flare onset. From the observation of spots movement in active regions, we found that some spots, which were located beneath Hα flare ribbon footpoints, underwent a particular motion compared with other spots in the same active region. They moved in different pattern. These spots underwent a disturbance in their moving direction before the flare started. The disturbance could be either in the east - west or the north - south direction. It started 2 hours to 30 minutes before the flare onset. This phenomenon always occurred in all the flaring active regions we studied in this paper. The spots proper motion in short time scale before flare onset give us a new view in finding the flare precursor. This finding lead to the suggestion that if a sunspot shows a ’peculiar’ motion different from other sunspots in the same active region, a flare should occur on its sunspot area a few hours later or so. On the other hand, from the GOES X-ray plots, we found no remarkable sign was observed that can be used as the precursor of flares. They show no remarkable sign before flare onset. We suggest that the proper motion is a better indicator for flare than the X-ray intensity. As the results, we suggest that in the future, the disturbance in proper motion of spots in active region might allow us to predict the flare occurrence in short time scale. We expect that SOLAR-B/SOT will be able to reveal the detailed relation between the sunspot motion, related magnetic activity and flare onset, making a short term prediction of flare occurrence possible. Data were provided by Solar Flare Telescope, Mitaka, NAOJ, data selection rule is: Continuous data (images) in order of few minutes before flare onset Continuous data (images) in order of few minutes before flare onset No flare erupted in the same active region before selected flare No flare erupted in the same active region before selected flare Data sets used in this study.