Formation of a penumbra in a decaying sunspot

Transcription

1 Formation of a penumbra in a decaying sunspot Rohan Eugene Louis Leibniz-Institut für Astrophysik Potsdam (AIP) Shibu Mathew, Klaus Puschmann, Christian Beck, Horst Balthasar 5-8 August st SOLARNET - 3rd EAST/ATST meeting 1

2 Introduction Distinct property of sunspots Rapid formation, growth in segments Flux exceeds x10 19 Mx (Leka & Skumanich 1998) 4 hr for coverage of half umbral circumference (Schlichenmaier et al. 2010) Individual penumbral filaments form in 30 min Transient penumbrae form on similar time scales in decaying fragments of sunspots (Louis et al. 2012) Scharmer et al August st SOLARNET - 3rd EAST/ATST meeting 2

3 Introduction Schlichenmaier et al Elongated granules indicate emergence of flux Penumbra forms on other side of sunspot away from opp. polarity 5-8 August st SOLARNET - 3rd EAST/ATST meeting 3

4 Introduction Schlichenmaier et al Flows with opp. sign as the EF during early stages of formation and late stages of decay Bellot Rubio et al August st SOLARNET - 3rd EAST/ATST meeting 4

5 Observations NOAA AR on 2011 Sept. 4 4k x 4k pixel FD solar images of continuum intensity, dopplergrams and LOS-magnetograms from HMI (Schou et al. 2012) Cadence of 12 min, 0.5 arcsec pixel sampling Hinode/SP obs. (Lites et al. 2001, Ichimoto et al. 2008) in normal map mode. Repeated scans 18''x81'' FOV 18:30-19:22 UT Θ = 14 at time of SP obs. 5-8 August st SOLARNET - 3rd EAST/ATST meeting 5

6 Results Decaying follower sunspot in AR EFR in close proximity to decaying sunspot Significant decay within 14 hr Traces of penumbral formation 5-8 August st SOLARNET - 3rd EAST/ATST meeting 6

7 Results Formation initiated by coalescence of magnetic fragment outside the DS Red shifts 1.5 km/s Speed of 300 m/s Coalescence with DS 7 hr later emergence Lifetime of about 10 hr, intensity exceeds QS by 20% during decay 5-8 August st SOLARNET - 3rd EAST/ATST meeting 7

8 Results Large segment of penumbra develops as previously formed filaments decay Strong red-shifts of 2.5 km/s at umbra-qs boundary prior to formation Red shifts persist for 3 hr before changing to regular Evershed flow 5-8 August st SOLARNET - 3rd EAST/ATST meeting 8

9 Results Elongated granules with dark intergranular lanes decaying penumbra Larger penumbral segment RS 3.5 km/s and EF of 2 km/s RS reduce to 1.5 km/s and lie side-by-side to regular EF 5-8 August st SOLARNET - 3rd EAST/ATST meeting 9

10 Results 2 comp. Inversion with SIR Pixel at intense brightening upflows 3.8 km/s, 1.1 kg, 117 Strong red-shifts in newly formed penumbra downflows 6.5 km/s, 2.3 kg, August st SOLARNET - 3rd EAST/ATST meeting 10

11 Summary Formation of penumbra in a DS by coalescence with a magnetic fragment which is strongly red-shifted Penumbral filaments at this site survive for 10 hr, decay phase, upflows of 4 km/s with intense brightening Large penumbral segment forms south of the decaying penumbral filaments, with supersonic downflows that co-exist with the regular EF for nearly 3 hr Formation is facilitated by increase in magnetic flux supplied by the magnetic fragment 5-8 August st SOLARNET - 3rd EAST/ATST meeting 11

12 Summary Penumbral formation in decaying sunspot is similar to and differs from that seen in a developing proto-spot Similarities increase in flux and red-shifts/downflows Differences formation occurs at the location of coalescence in close proximity to an emerging flux region and not on opposite side of sunspot (Schlichenmaier et al. 2010, Romano et al. 2013) 5-8 August st SOLARNET - 3rd EAST/ATST meeting 12

13 THANK YOU 5-8 August st SOLARNET - 3rd EAST/ATST meeting 13