Oscillations in the solar chromosphere using multi-layer observations. Tanmoy Samanta

Transcription

1 Oscillations in the solar chromosphere using multi-layer observations Tanmoy Samanta D. Banerjee, V. Pant Indian Institute of Astrophysics, Bangalore, India & V. Henriques, S. K. Prasad, M. Mathioudakis, D. Jess Queen s University, Belfast, Northern Ireland, UK

2 Introduction to QS Chromospheric Zoo SDO/HMI Magnetogram

3 Introduction to QS Chromospheric Zoo SDO/HMI Magnetogram

4 Introduction to QS Chromospheric Zoo SST/CRISP Fe 6302 Stokes V 1-m Swedish Solar Telescope CRisp Imaging SpectroPolarimeter (CRISP)

5 Introduction to QS Chromospheric Zoo SST/CRISP Hα Continuum

6 Introduction to QS Chromospheric Zoo SST/CRISP Hα Core

7 Introduction to QS Chromospheric Zoo Stokes V Photosphere SST/CRISP Hα Core Chromosphere

8 Multi-Layer Observations Hα line core forms at chromosphere and wings form at lower atmospheric heights (Leenaarts et al. 2006, 2012). Filtergram images taken at different position of Hα line, sample, on average, different atmospheric layers.

9 Multi-Layer Observations 7 Scan Position Magnetic Field at Solar Surface Time: 09:06 to 09:35 UT on 2013 May 5. Reconstruction: Multi- Object Multi- Frame Blind Deconvolution (MOMFBD) method. Spatial resolution: 0.16'' in Hα. FOV: Mm. Cadence of each scan was 1.34 s (28 Min total) Red Wing

10 To study the oscillation properties of the different layers we created Power-maps of different layers around 3, 5 and 7 minutes with 1-minute wide period bands.

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12 Magnetic Shadow: Suppressed power surrounding magnetic network elements. (Vecchio et al. 2007, Kontogiannis et al. 2010, 2014)

13 Magnetic Shadow: suppressed power surrounding magnetic network elements (Vecchio et al. 2007, Kontogiannis et al. 2010, 2014) Power Halo: Enhanced power close to photosphere (Kontogiannis et al. 2010, 2014)

14 1. Photosphere: Global P-modes 2. Cut-off period: 5 min in the photosphere to 3 min in the Chromosphere. 3. Magnetic field can changes the scenario. 4. Mode Conversion: Waves Change their mode 5. Create Magneto-acoustic Portals. Power Halo (Nutto et al. 2010,12 Kontogiannis et al. 2010,14)

15 Long-period slow waves are channeled to the upper chromospheric layers following the magnetic field lines, while short-period fast waves penetrate the magnetic canopy & are reflected back higher?

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17 Rapid Blueshifted Excursions Rapid Redeshifted Excursions RBEs & RREs: On-disk absorption features seen in red & blue wings of Hα. High speed jets/blobs from magnetic network with speeds of km/s. Lifetime of s. Similar to Type II spicules. (Pereira et al. 2014; Kuridze et al. 2015; Rouppe van der Voort et al. 2015).

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21 Mottles Disk counterparts of Type I spicules. Seen in the Hα line with velocities around km/s and lifetimes of 3-15 minutes (Tsiropoula et al. 2012). Tziotziou et al. (2003): Mottles arise at the network boundaries as bursts of material and propagate upward also have a tendency to occur several times at the same place with a typical duration of around 5 minutes.

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24 Artificially Generated Time Series Signatures in the power spectrum of bursty signal. A 3 min sinusoid convolve with a Gaussian signal of FWHM of 3 minutes. Amplitudes of the sinusoidal wave and the Gaussian signal are kept at 5 % and 30% of the background Why? Slow waves amplitude less than 5 % while mottles can reduce the background intensity by up to 30 % Peak ~ 7.7 minutes. Periods mainly depend on the distribution of the intensity drops/amplitude & are generally greater Than their FWHM.

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27 x Power Halo

28 Mottles Magnetic Shadow RBEs.. Power Halo Shock Waves

29 Summary Power maps of chromosphere show suppressed power surrounding magnetic network elements, known as magnetic shadows and also show enhanced power close to the photosphere, referred as power halos. The interaction between acoustic waves and inclined magnetic fields is generally believed to be responsible for the formation of these two effects. In this study we explore if small-scale transients can cause similar effects. We show that the presence of transients (lifetime), like mottles, RBEs & RREs, can strongly influence the power-maps. Magnetic shadows can be explained as due to the suppression of acoustic oscillations in the rosettes by transients like mottles. Power halos are caused by the enhancement of power by strongly Doppler-shifted transients such as RBEs and RREs. Warning : Not everything periodic in the outer atmosphere is evidence of a wave. Thanks Samanta et al. 2015, Under Review, ApJ

30 Artificially Generated Time Series Signatures in the power spectrum of bursty signal. Case-1: Fur Gaussian dips in Intensity with a FWHM of 1 minute which are separated by a random time interval. RBEs and RREs Strongest power around 7 minutes along with other peaks at 4 and 2.5 minutes. The periodicity here is mainly because of the repetition times.

31 Artificially Generated Time Series Signatures in the power spectrum of bursty signal. Case-2: two Gaussian profiles one with FWHM of 3 min & other with 5 min & separated by 12.5 min Mottles Peak a~ 6.4 minutes.

32 Artificially Generated Time Series Signatures in the power spectrum of bursty signal.