observations of high frequency waves in...

><BRITISH-RUSSIAN SEMINAR 2017, 6TH JULY 2017

Observations of high-frequency waves in

spicules JUIE SHETYE

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• Spicules - long & thin jet-like features seen all over the sun. • Apparent Type I and Type II spicules —Different formation

mechanism, lifetimes and velocities.

Overview - What are spicules ?

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SOT/ Hinode movie High resolution of images in Ca II H spectral line November 9, 2006 (from Okamoto et al. (2007))

--BRITISH-RUSSIAN SEMINAR 2017

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Why do we study Spicules?


Credit: Scott McIntosh, Bart De Pontieu, Viggo Hansteen and Karel Schrijver /UCAR.

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Peculiar spicular-type events

IBIS - DST H-alpha images

• Traditionally spicules are considered as flux tubes where plasma flows along its length.

• Suddenly appearing and disappearing events.

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Spicular-type events: the hypothesis

Judge et al 2011, 2012 suggested that these could be sheet-like structures of chromospheric material and sudden appearance could be LOS effect due to density perturbations, analogous to curtains.


Example of curtains (Judge et al.2011,2012)

8542.0 Å

photosphere

chromosphere

original movie : Dr. Eamon Scullion

How do we detect spicular-type events ?

Imaging-spectroscopy by CRISP (SST in Ca II 8542 Å)

• Combining physical and spectral properties of a structure.

• Shows how we scan across solar atmosphere using imaging spectroscopy.

• As we scan through the spectral line, we see different images corresponding to different layers of atmosphere.

(CRISP - CRisp Imaging SpectroPolarimeter) (SST - 1m Swedish Solar Telescope)

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Examples of spicular-type observations

time(s)

0.88

0.90

0.92

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0.96

0.98

1.00

norm

alize

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yredblue

0 20 40 60 100

• Using 1-meter Swedish Solar Telescope (SST) in Hα .

• I use light curves to show appearance and disappearance in red and blue wings.

• Light curves are plotted by summing the intensity taken at various points along the length of the spicules

• More complex events.

• Movie : Temporal evolution at - 774 mÅ of Hα line scan• 10 June data (cadence 3.9s) 7250km X 7250

km


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What are spicule-type events ?

•Spicules that represent magnetic flux-tubes, moving in and out of the 60 mÅ CRISP narrowband filter lasting between 15 to 40s.

•Similar to on-disk signatures of type-II spicules.

•Sudden appearances and disappearances - absence of flows

•Observed transverse motion (line of sight motion and image plane motion).

•High-frequency waves (~50mHz).

Shetye et al . 2016, A&A, 589, A3--BRITISH-RUSSIAN SEMINAR 2017

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High-frequency wave in image-plane direction

•Movie at - 774 mÅ from Hα line core•Cadence of 5s and lifetime of transient at 40s


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Analysis of transverse motion

4 6 8 10X (arcsecs)

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Y (arc

secs

)

0 100 200

distance (km)0

20406080

+516 mÅ +774 mÅ

300 0 100 200 300distance(km)

0 100 200

distance(km)0

20406080

-774 mÅ

020406080

time

(s)

time

(s)

time

(s)

P1

300

• High-frequency waves : Periods ~40s• Time—distance diagrams are plotted for each slit position across

different wavelength positions• Image in + 774 mÅ of Hα line scan• Are these propagating or standing waves?


P1 P10

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High-frequency waves in LOS direction

arcsecs arcsecs arcsecs arcsecs

arcsecsarcsecsarcsecsarcsecsarcsecsarcsecs

arcs

ecs

arcs

ecs

08:06:42.886 UT

2 4 6 8

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arcsecs

08:06:46.842 UT

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arcsecs

08:06:50.798 UT

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08:06:54.777 UT

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08:06:58.736 UT

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08:07:02.695 UT

2 4 6 8

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08:07:06.671 UT

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08:07:10.622 UT

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08:07:14.572 UT

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08:07:18.549 UT

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08:07:22.501 UT

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08:07:26.478 UT

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• Doppler image sequence corresponding - constructed from image difference of intensity images at +/- 774 mÅ

• Is this torsional Alfvén wave or helical kink or something less? • Need for analysing image-plane and LOS transverse motion.• We cannot comment on exact nature due to absence of spectro-polarimetric

signals. Shetye et al . 2016 CSPM Proceedings --BRITISH-RUSSIAN SEMINAR 2017

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• The time--distance maps are plotted from the bottom of the feature to the top represented by positions P1-P10.

• The location of the spicule is represented by blue colour in the time--distance maps.

• Spicules (blue) are closer to each other and indistinguishable in slit positions P1 and move apart and are around 800 km apart in P9.

Possibility of mode-coupling associates with spicular-type events


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Coherence between LOS velocity and intensity perturbations - analysis

• Intensity variations represent compression of flux tube

• Velocity (transverse motion, incompressive) shows coherence with intensity perturbation (compressive) - Jess et al 2015, SSR, Sharma et al. 2017)

normalised intensity velocity (km/s)

0 40 80 1201006020

time(s)

no

rma

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d in

ten

sity

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m/s

)


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Relations of spicular-type events towardsenergy transfer from photosphere to the

corona ?


•Multiple spicule-type events interacting.

•Complex magnetic flux tubes interacting with each other.

•Imagine a cylinder with multiple flux tubes and the waves are propagating.

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Contribution to energy transfer? - theory

•Simple MHD simulation

•Multiple flux tubes•High-frequency waves moving from the photosphere to the corona

Movie: Shrivastava, et al. 2017 Nat SR., Simulations done by Prof. Kris Murawski

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Contribution to coronal energy budget

So the spicular-type events acting as multiple flux tubes interacting with each other:

1. can harbour high-frequency waves

2. can transfer energy to the corona (Total energy after reflection from the transition region: ~106 ergs cm-2s-1).

Image: Shrivastava, et al. 2017 Nat SR.


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Summary

What physical processes are related to observations of spicules? • I have tried to show the physics behind occurrence of spicular-type

events.• I have further shown that such events drive high-frequency waves (50

mHz or ~50 s)• Using models, we have shown that such waves can reach lower corona

and contribute to energy transfer.

What is left to be done? • Quantifying the role of such events towards heating - How much energy

is converted into heating? • Understanding plasma properties related to waves in spicular-type

events : Spectro-polarimetric observations - Need DKIST/ESTMagnetic field information - Need DKIST/EST


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• Combining observations of the solar chromosphere with numerical simulations.

• High resolution observations from National Solar Telescope (BBSO), Swedish Solar Telescope (SST) with IRIS/SDO.

• LareXd • Projects -✴ Spicules - formation and

dynamics. ✴ Rotating chromospheric jets. ✴ Chromospheric dynamics of

Prominences and flares.

What am I working on at CFSA, UoW?

Bottom panel : AIA 1600 image, top left CRISP Hα image and top right - top view of the MHD model

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THANK YOU

19--BRITISH-RUSSIAN SEMINAR 2017

ACKNOWLEDGEMENTS : PROF. J.G.DOYLE,

DR.EAMON SCULLION,DR. DAVID KURIDZE,

DR. MARCO STANGALINI,DR. VASCO HENRIQUES,

DR. ABHISHEK SRIVASTAVA,PROF. KRIS MURAWSKI,

ORGANISERS OF BRITISH-RUSSIAN SEMINAR 2017

observations of high frequency waves in...

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