On the Study of Waves and Transients in the Solar

Atmosphere

(In the Prospective of Our Upcoming National Projects) Abhishek K. Srivastava

Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital,

India

Some  Majors  of  Solar  Research  in  Current  Prospective

[2] Space borne observations, modeling, and atmospheric seismology related to various magnetohydrodynamic waves.

[1] Study of large-scale eruptive phenomena and their space weather consequences.

[3] Study of solar transients at diverse spatio-temporal scales.

STUDY OF LARGE SCALE TRANSIENTS

[1] Flare-CME Relationship using Multiwavelength Observations.

[2] Space Weather Consequences of Solar Eruptions.

[3] Drivers of Solar Eruptive Phenomena : Flux Emergences; Instabilities; Role and conditions for well known reconnection events !!

[1] About AR 10960 on 04th June 2007 Gave Recurrent Flares

This AR was very unique in terms of flare productions, however, was poor in CMEs production capability. It has produced 10 M-class flares in which only two were associated with CMEs (Yashiro et al., 2008). Its location was S09E50 near the east limb on 04th June 2007, and it has produced one B-class flare between 4.00-5.00 UT, while M-class flare during 5.00-7.00 UT. AR was associated with the descending phase of previous solar cycle 23, and it was normal AR.

References : [1] Srivastava, A.K., Zaqarashvili, T.V., Kumar, P., Khodachenko, M.L., 2010, ApJ, 715, 292. [2] Kumar, P., Srivastava, A.K., Filippov, B.P., Uddin, W., 2010, Solar Physics, 266, 39

The recurrent solar flares have been occurred in the AR on 04th June 2007 due to very interesting activity at a small positive polarity sunspot and associated twisted loop at the centre of AR.

[1] B5.0 Class Flare during 04:40—04:51 UT [2] M8.9/3B Flare during 05:06—06:45 UT

STEREO/SECCHI reveals the coronal overlying field configuration during the time of recurrent solar flares (B and M-class). It should be noted that the overlying magnetic field seems very complex. The major change is the evolution of successive helical twists in the AR 10960 near a positive polarity sunspot.

AR10960 as Viewed from Corona during Recurrent Flares

Results and Conclusions [1] The activation of first helical twist is found to be the driver of recurrent

flares. [2] The minimum 3 twists are visible at one half of the twisted flux tube. Therefore, the total twist crosses the critical limit of 2.5-3.5 Pi to trigger the instability.

[3] The Alfvenic transit time is found to be ~80 s (L=80 Mm, VA=1000 km/s) for our observations. Therefore, any imbalance in the twist can be smoothed by this time. Therefore , we assume the quasi-symmetric twist In the loop as proposed by Fan et al. (2009), and estimate the upper limit of the total twist as 12 Pi.

[4] Simulation is also supporting upto some extent such important observations of kink unstable flux-tubes.

References : Botha, G.T.T., Arber, T.D., Srivastava, A. K., 2011, ApJ, vol. 742, in press.

[3] The Generation of M-Class Flare due to Coalescence Instability and Associated Quasi-periodic Oscillations References :- [1] Pankaj Kumar, A.K. Srivastava, B.V. Somov, P.K.Manoharan, R. Erdelyi, W. Uddin, 2010, ApJ,723, 1651 [2] A.K. Srivastav , Nakariakov, V., Dwivedi, B.N., Kumar, P.., 2011, BASI and also in preparation the main part (the QPO paper)

M7.9 class flare, AR 10875, 27 April 2006

GOES/SXI

TRACE 171

Loop-Loop Interaction and Flare Energy Release

[1] Tajima’s coalescence instability works in our observations (Kumar et al., 2010) when two magnetic islands merge and cause the bursty reconnection (Tajima et al., 1982, Kleim et al., 2000) [Srivastava, Nakariakov, Dwivedi, and Kumar, 2011, sub].

Credit : Aschwanden, 2004

[2] In the high energy range of the HXR (50-100 keV), we got the bursty QPO of which is certainly not related with the wave phenomena as it is showing only < 2.0 cycles during course of the detection of QPO. This again shows that some instability in the interacting loop system is causing the bursty power and related periodicity.

Several Facts in Observations

[3] Failed Flux-ropes and Building-up of Magnetic Complexity during Flares

This AR11045 as studies on 12 February 2010 was very unique in terms of high flux emergence and flare productions, during its journey over the whole disk. A huge twisted flux-tube was activated to move up with an M-class flare, and it was expected on the first instance that it may give the associated CME. However, interestingly it was failed to penetrate the overlying magnetic fields due to its initial suppression due to an overlying remanent flux-tube. Detailed estimations can be found in the reference [1] Important to forecast the pre-conditions of any outer coronal eruptions.

References : [1] Kumar, P., Srivastava, A.K., Filippov, B.P., Erdleyi, R., Uddin, W., 2011, Solar Physics, in press. [2] Dwivedi, B.N., Srivastava, A.K. et al., 2012, New Astr., in press.

Magnetic field complexity generates the coronal responses of the eruption.

[2] M Class Flare and related Halo CME on 07 Feb 2010 From the same AR

Transients at Comparatively Small-Scale (Jets, Spicules, Flows etc.)

De Pontieu, Erdelyi, James, Nature, 2004, 430, 536

Leakage of 5.0 min oscillations

De Pontieu et al., 2011, Science, 331, 55

Hot plasma upflows in the atmosphere

Flows and/or Waves !

Waves and Reconnection

Cirtain, 2007, Science, 318, 1580 Propagation of transversal waves at Alfvenic velocity !!

Standard scenario of reconnection generated jet

[1] Observations of A Cool Jet in North Polar Region on Aug 03, 2010

SDO/AIA Observations

Length = 72 Mm

Width = 20 Mm

Life-Time = 21 Min

Most of the emissions are in the 304 channel, therefore, considered as a cool jet motion.

Different from polar surges depending upon life-time and spatial scale (Georgakilas et al., 1999)‏

Not any unusual activity/ appeared near the origin of jet during course of its life time.

Srivastava and Murawski, 2011, A&A, in press

FOV

A fainter jet motion with a speed around 110 km/s, and then the fall of the material along the same path.

2-D MHD Model

Equilibrium Conditions

&

Consideration of gravitationally stratified atmosphere with an appropriate T-model (Vernazza et al., 1981)‏

Magnetic Field Configuration

with

Velocity Pulse

[2] The Dynamics of Post-flare Plasma during an M1.0 Class Flare

Two Ribbon M1.0 Class Flare from AR11093 as shown in SDO/AIA 171 on 18:51 UT (right) and 304 (left) overlaid by MDI magnetic field contours

Reference : Srivastava and Murawski, 2011, ApJ, vol. 742, in press.

Subsonic post-flare transients moving with lower bound speed of 29 km/s. The hot plasma counterpart is also visible in SDO /AIA 171 that envelopes the above visualized cool counterpart as evident in 304.

Numeric in the Support of Observations

The simulated macrospicule with a velocity pulse launched above the photosphere for the duration of 1000 s

A velocity pulse is steepen in to a slow shock. Rarefaction of the plasma behind the shock front creates the under pressure region that sucks up the cool low atmospheric material into the upper atmosphere forming the long spicule.

When the down-falling plasma interacts with another outgoing pulse, then the bi-directional plasma motion is seen as observed.

This explains many observed properties of the long spicules, e.g, ballistic nature, bi-directional flows, periodic rise and all , and upto some extent the length, width, and life-time that can be exactly tuned.

[3] Numerical Simulation of Solar Macrospicules

Prominences

Spicule Boarder Open Field Coronal Hole

Network Patterns forming the lower atmospheric canopies and cavities

Eq. Coronal Hole

Coronal Loops (Active regions)‏

Quiet Sun

Coronal Bright Points (assumed to be made by small scale loops) ‏

MHD waves and oscillations are ubiquitous observationally at the Sun now using recent space based observations (e.g., Hinode, STEREO, SDO) as well as by ground based observations using modern techniques (e.g., SST, ROSA).

Credit : EUVI/STEREO

Prominence Cavities

e.g., Tubular modes ,e.g, kink, sausage, torsional oscillation; Propagating (e.g., slow and fast magneto-acoustic waves near footpoint) ‏

e.g., Propagating Alfvén , slow and fast magnetoacoustic waves

e.g., Propagating Alfvén , slow and fast magnetoacoustic waves

e.g., Propagating Alfvén and fast magnetoacoustic waves. Cavity modes in the lower atmosphere

e.g., Leakage of 5-min acoustic oscillations, Alfvén waves

e.g., Alfvén waves and Magnetoacoustic waves

STUDY OF WAVES AND OSCILLATIONS AND MHD SEISMOLOGY

Observations/Identification of Wave Modes in Coronal Structures

•  Kink oscillations of coronal loops (e.g., Aschwanden et al. 1999, Nakariakov et al. 1999, O’Shea, Srivastava, Doyle, and Banerjee, 2007, Pandey & Srivastava, 2009 for the analogy of stellar loops)‏

•  Propagating longitudinal waves in polar plumes and near loop footpoints (e.g., De Forest & Gurman, 1998; Berghmans & Clette, 1999; DeMoortel et al., 2002, 2003; Banerjee et al., 2009; Srivastava and Dwivedi, 2010a)‏

•  Standing longitudinal waves in coronal loops (e.g., Kliem at al. 2002; Wang & Ofman 2002, Srivastava & Dwivedi, 2010b, Mukul Kumar, Dwivedi, and Srivastava, 2011)‏

•  Sausage mode (e.g., Nakariakov et al. 2003, Srivastava et al., 2008; Erdelyi & Taroyan, ‏(2008

•  Propagating fast wave trains, Alfven waves (e.g, Williams et al. 2001, 2002; Cooper et al. 2003; Katsiyannis et al. 2003; Nakariakov et al. 2004, Verwichte et al. 2005, Jess et al., ‏( 2009

Diagnose the local plasma conditions Principle of MHD Seismology

Analogous to Helioseismology

Modern Trend : Multiple harmonics are diagnosing crucial plasma conditions, e.g., scale heights, density contrasts, longitudinal structuring, effects of magnetic field divergence and density stratification etc.

Selected Loop

1. Multiple Sausage Observations in the Cool Post Flare Loop

The loop system is also visible in higher temperature lines , e.g.,Fe IX/ X 171 EIT/SOHO : This implies that the energy balance is not occurring, and there is temporal change of density, temperature etc. This also implies that the loop is not in hydrostatic equilibrium as we are aware. Hence, the hydrostatic condition of upper or lower solar atmosphere is only a limiting case.

H-alpha 6563 Image obtained using ARIES Tower Telescope

May 2, 2001 AR 9433 (N15, W 88) ,01:00:52 UT – 01:58 :28 UT ---> Post Flare Loop System

Power Spectrum Near Loop Apex Power Spectrum Near Loop Footpoint

Ø  Observed Loop Length ~ 35 Mm, Loop Width ~ 4 Mm

Ø  The phase speed will be ~ 2L/P ~ 109 km/s

Ø  The speed is much higher than the sound speed at this low temperature .

Ø  Hence, we suggest the fast tubular sausage modes in this cool loop. Ø  Period Ratio P1/2P2 = 0.84.

Fast Sausage Oscillation Modes in the Curved Loops Fundamental

Mode : Pressure anti nodes

at apex while pressure nodes

near appex

Fundamental Mode : Hence leads density

perturbation and associated intensity

oscillation near apex

First Harmonics :

Pressure node at apex,

while pressure anti-nodes near foot-points

First Harmonics : Hence leads density

perturbations and associated intensity

oscillations near foot-points

Since, the loop is maintained at temperature 104 K. Hence, at low sound-speed we can use the cold plasma approximation. Hence the cut-off wave number kc will be (Edwin & Roberts 1983, Solar Physics, 88, 179; Roberts et al. 1984, ApJ, 279, 857) :

------------------------------ [1]

------------------------------ [2]

----------------------------- [3]

Loop Seismology with multiple oscillations

Ø  Only very dense loops can support the non-leaky sausage mode in the estimated length and width (Nakariakov et al. 2003, A&A, 412, L7).

Ø  The post flare loops have usually very high density contrast between 100-1000, and thus our selected loop is also an over dense postflare loop.

Ø  The selected loop is cool postflare loop, and density ratio falls in the expected range. hence, the trapped sausage mode may occurs in the loop, however, wave leakage can not be ruled out.

Results and Discussions

Ø  Shift of P1/P2 ratio from 2.0 can be due to the density stratification or magnetic field stratification in such loops, similarly as found by Van Doorsselaere et al. (2007, A&A, 473,959), Verth & Erdelyi (2008, A&A, 486, 1015) for kink waves.

Ø  The estimated density scale height for the observed parameters is ~ 6.0 Mm

Ø  These results are the confirmations of the findings published in our one paper in (MNRAS, 388, 1899) by A.K. Srivastava, T.V. Zaqarashvili, W.Uddin, B.N. Dwivedi, and Pankaj Kumar. However, the local plasma properties vary from loop to loop in the post-flare loop system.

Ø  A theoretical test has been successfully performed by Inglis et al. (A&A, 2009) for our mail observational findings published in MNRAS.

Co-aligned images and overlaid contours confirm the presence of small-scale loop system associated with coronal bright point

[2] Reference : Srivastava, A.K., Dwivedi, B.N., 2010, MNRAS : A Case Study of Waves in the BP

Tadpole Head

Tadpole Tail

Damped Oscillation Amplitude

Linear Trend

Sound Speed = Speed of Acoustic Waves Cs (t) temporally varies and will be inversely proportional to period of the

oscillation in the closed loop system cooled by the radiative cooling effect (Aschwanden 2004). However, this was not tested

yet in observations.

Therefore, this is the observational signature for the radiative cooling effect which can damp acoustic waves

Radiative cooling and thus finite radiative relaxation time generates the

low –frequency cut-off environment which allows the propagation of

acoustic waves upto inner corona (Theory : - Roberts, B., Sol. Phys., 1983,

88, 77). We have the observational clues here !!!

Recently the first detailed theoretical models have been reported by Morton & Erdelyi (2009), and Morton et al. (2010) about the effect of radiative cooling on the kink oscillation modes of solar loops as well as also on the propagating magnetoacoustic waves in the homogeneous plasma. The observational results are still awaited regarding these firstly performed modeling.

However, this will be interesting to model such observations of small-scale solar structures, which are small in length scale however very bright and denser also.

Large radiative loss is not expected from background quiet-Sun. However, the highly dense and comparatively much active BPs may have good emissions.

Slight Amplification

Inversion of Quasi -Tadpole

Signature of Damping again due to radiative cooling, however, again then the growth of the wave in the inner corona : Possibility of resonant energy transfer to the acoustic wave which propagates upto inner corona already after getting damped in the chromosphere !!!! Most probably the resonant energy transfer from the transversal waves of double period !!!!.

Alfven Waves above the Bright Points : The First Discovery from the SST/La Palma by Jess et al (2009 , Science)

The transversal Waves with period < 700 s have been discovered in the family of such bright points

The chromospheric magnetic BP (MBP) is the region of high magnetic field concentration

Possibility of Mode Coupling and Resonant Energy Transfer by Alfven Wave of Double Period

1. In Idea MHD, the Alfven wave of the double period can resonantly transfer its energy to the acoustic wave in the region where plasma beta approaches unity (Zaqarashvili and Roberts, 2006). The plasma beta can approach unity not only In the lower chromosphere but also anywhere upto inner corona (Gary et al., 2001). 2. If initially there is an Alfv´en wave, then it drives sound waves with twice the frequency and wave number of the Alfv´en wave (Hollweg 1971).

We most probably firstly find some indirect evidences of the coupling of acoustic wave around 5 min with the transversal waves with double period as observed by Jess et al. (2009) in the family of solar bright points. However, the more detailed study is needed in this direction with simultaneous observations of longitudinal and transversal waves with recent space (e.g., Hinode, SDO) and ground based observations (e.g., SST/La Palma, ROSA/ St. Peak NSO).

3. The signature of dissipation and then growth ( by The energy transfer from the transversal wave ) at ~ 10 min scale in the inner coronal plasma also probably confirms the resonant energy transfer between two modes.

Science with NLST and

ADITYA

Dynamics of Low-atmospheric Dynamical Events.

(NLST)

Activity and Energetic Phenomena

(NLST, ADITYA)

Magnetic Fields and Surface Magnetism

(NLST & ADITYA)

Local Helioseismology (NLST)

Community will be looking forward for the solar research related to waves and transients in the solar atmosphere

as one of the scientific pursuits keeping the view of upcoming complementary high resolution data from upcoming 2m-NLST and ADITYA.

THANK YOU VERY MUCH