IRIS observation of penumbral microjets in the chromosphere and their transition region counterpart

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1 IRIS observation of penumbral microjets in the chromosphere and their transition region counterpart Y. Katsukawa (NAOJ), Y. Kimura (Univ. of Tokyo) T. J. Okamoto (Nagoya Univ.), T. Tarbell (LMSAL) IRIS-4 WS May 18-22, 2015

2 Penumbral micro-jets (PMJs)!! Penumbral micro-jets (PMJs)!! Energy release through magnetic reconnection in the interlaced magnetic fields in a sunspot penumbra.!! It is hard to generate fast (>30km/s) jets if magnetic reconnection happens in the upper photosphere or lower chromosphere (because plasma beta ~1). Are waves important? May 18-22, 2015 IRIS-4 WS

3 Spectroscopic observations of the Ca II 854 nm line with IBIS Reardon, Tritschler, Katsukawa (2013)!! Observation with IBIS at DST (NSO)!! Emissions in the wings.! T enhancements in the low chromosphere.!! For some PMJs, a blue-wing enhancement is seen, which indicates ~10 km/s upflows. Do they influence upper chromosphere (or higher)? How does the velocity evolve along the height? May 18-22, 2015 IRIS-4 WS 3

4 Observation (IHOP250) AR Mar 2014 SDO AIA 1600 A Hinode Ca II H 1.6 sec cadence Ca II H FFT filtered (t < 100 s) Hinode SP IRIS! SJ Mg II and Si IV 10 sec cadence! Sit-and-stare Mg II, C II, and Si IV 5 sec cadence Sparse-dynamic mode 9 FOV in 1 minute Hindoe! FG: Ca II H 1.6 s cadence! SP: sparse-dynamic mode IRIS SJ 2796 A IRIS SJ 1400 A SDO AIA 171 A May 18-22, 2015 IRIS-4 WS

5 Examples of PMJs seen with IRIS SJ Hinode Ca II H filtered (t < 100 s) IRIS SJ 2796 IRIS SJ 1400 SDO AIA arcsec May 18-22, 2015 IRIS-4 WS

6 Examples of PMJs seen with IRIS SJ Hinode Ca II H filtered (t < 100 s) IRIS SJ 2796 IRIS SJ 1400 SDO AIA arcsec Similar structure in Mg II Bright dots at the outer edge of the PMJ The PMJ looks similar but longer in Mg II Slightly elongated along the PMJ Slightly elongated along the PMJ The PMJ looks longer in Mg II May 18-22, 2015 IRIS-4 WS

7 Bright dots in the TR above a sunspot!! Si IV bright dots in a sunpot were already reported by Tian et al. (2014).! Size: km and km, slightly elongated parallel to filamentary structure.! Lifetime less than 1 minute! Half of the dots show apparent movement with km/s We found most of the short-lived bright dots seen in the Si IV images are associated with PMJs. May 18-22, 2015 IRIS-4 WS

8 Time evolution along PMJs Ca II H Ca II H Position along the length (arcsec) Ca II H filtered SJ Mg II SJ Si IV Time ~1000 km/s ~500 km/s ~100 km/s Elongated brightenings at the outer end of PMJ Time ~400 km/s ~150 km/s May 18-22, 2015 IRIS-4 WS Position along the length (arcsec) Ca II H filtered SJ Mg II SJ Si IV

9 Time evolution along PMJs Ca II H Ca II H Position (arcsec) Ca II H filtered ~400 km/s SJ Mg II SJ Si IV Time Time May 18-22, 2015 IRIS-4 WS Position along the length (arcsec) Ca II H filtered ~400 km/s SJ Mg II SJ Si IV

10 Temporal evolution of spectra observed by IRIS IRIS SJ 1400A Mg II Mg II diff C II Si IV - Enhancements of Mg II k2 emission - Enhancement at the blue wing suggesting ~10km/s blue shifts. - No brightenings at C II and Si IV. Time (sec) - Si IV brightenings (and C II also but weak) with a small (<10km/s) Doppler shift. lambda May 18-22, 2015 IRIS-4 WS

11 Summary of HINODE-IRIS obs of PMJs!! PMJs are clearly identified in the IRIS SJ data.!! Owing to the 1.6 sec cadence Ca II data obtained by HINODE, we can see acceleration near the footpoint of the PMJs in some events. Mg II Si IV!! The PMJs are driven near the footpoints in the lower chromosphere, and they rapidly propagate upward and heat the upper chromosphere to TR (and coronal) temperatures. Ca II May 18-22, 2015 IRIS-4 WS

12 Time evolution of Ca II 854nm spectra observed with IBIS Ca II 854 nm -548 ma -274 ma Line center +274 ma +534 ma Time slice along the PMJ at different wavelength positions of Ca II 854nm.! Observation of a sunspot with the IBIS Fabry-Perot instrument. 30 wavelength position around the Ca II 854 nm line (-1.5 Å to +1.5 Å). 5 sec cadence Time evolution of Ca II spectra along a PMJ Outer side! Wing emission propagates outward rapidly along the PMJ.! Weak line-core emission happens near the outer end. Position (arcsec) Outer May 18-22, 2015 Inner side wavelength IRIS-4 WS Inner

13 Summary!! By combining high resolution observations done by HINODE and IRIS, we clearly found counterparts of PMJs in the higher temperature lines.!! We can resolve time evolution of the PMJs by the high cadence (1.6 sec) obs with HINODE. It s hard to resolve the time evolution with the 10 sec cadence.!! What makes strong acceleration and heating along the PMJs?!! We can see faint brightenings even in coronal images (such as AIA 171 A) for some events. PMJs possibly contribute to the coronal heating. May 18-22, 2015 IRIS-4 WS