Published on June 27, 2014
Simulations of the Dynamics Generated in the Solar Atmosphere by Solar Global Oscillating Eigenmodes Michael Griffiths, Viktor Fedun, Robertus Erdélyi The Solar Wave Theory Group And Corporate Information and Computing Services The University of Sheffield National Astronomy Meeting University of Portsmouth June 2014
Outline • Solar Global Oscillating Eigenmodes • A model for studying dynamics in the atmosphere • Simulation • Evidence of induced Dynamics • Conclusion and Future Work
Dynamics in the Solar Atmosphere • Earliest observations of motions of the solar surface around 1918, (St.John C.E. et al, from Doppler Shift when studying solar rotation). • Leighton1960, Vertical motions 300- 400m/s,explained by Ulrich1970 • The solar p modes are generated by global resonant oscillations and turbulent motions just beneath the photosphere. • Modes trapped below the photosphere refracted by sharp change in density • Power peak at 5 – minutes p mode oscillations
l=4,m=2 l=10,m=4 l=20,m=2 Solar Global Eigen modes of Oscillation Hydrodynamic Waves Gravitating Slab Quantization condition – l usually large Spherical solution using spherical harmonics
• Demonstrate code validity by repeating earlier hydrodynamic 2D models of Malins and Erdelyi • Demonstrate cavity modes in the Chromosphere • Surface modes in the transition region • Understand dynamics allowing mode tunnelling and energy leakage into the corona • Modes evanescent around photosphere – inhibit propagation into corona • Upper and lower turning points determined by order Objectives
Vertical driver to Induce Dynamics in the Solar Atmosphere • Represent oscillation modes as a vibrating membrane • Driver located at temperature minimum • Deliver same amount of energy for different modes
• Fully stratified quiet solar atmosphere based on VALIIIC and McWhirter • Model of the stratified solar atmosphere • Height upto 6Mm • Cross section 4Mmx4Mm • 128x128x128 computational domain • Local acoustic cut-off • Propagation below cutoff • Evanescence (above cutt- off) • Cutoff calculated in different ways • Isothermal atmosphere • Highly stratified • Models with 30s,180s,300s drivers • 00,01 and 02 modes • Run normal mode fixed energy Computational Model
Stratified Magnetohydrodynamics Accelerated Using GPUs:SMAUG • SMAUG is a novel fully non- linear MHD code based on SAC/VAC (Shelyag et al 2008) • designed for simulations of linear and non-linear wave propagation • with gravitationally strongly stratified magnetised plasma. • Version of SAC ported to GPU (Graphical Processing Units) • Single GPU • 2.5xfaster than latest Intel Xeon (using 8 cores) • Multiple GPU version available
Validation of SMAUG (Flux Tube with Torsional Driver) 128x128x128 1.5x2x2Mm Fully stratified quiet solar atmosphere based on VALIIIC Flux tube 1000G Driver Amplitude 200km/s Period Also Orszag- Tang, Brio- Wu and explosion model Fedun et Al., Astrophys. J. Lett 740:L46,2011 movie
Energy leakage and Evolution • For each time step integrate the total energy over the model cross section • Plot the energies for the transition region and into the Corona • 180s and 300s modes provide energy leakage with period the same as that of the driver • 30s driver is the least efficient at coronal energy leakage. • Evidence for non linear beahviour
Variation of Energy leakage with Driver frequency • Integrate perturbed energy over cross sectional and over either the transition region or the corona • Take average over the simulation time • For the 02 mode 180s driver dominates
Variation of Energy leakage with Driver frequency Compute time averaged perturbation energy for the 00 and 01 modes • fundamental mode 5 min driver (300s) effective for energy supply to the corona region and 3 min driver effective for TR • 01 mode 5 min nothing for corona and 3 min again effective for TR • 02 mode 5 min nothing for corona and 3 min effective for corona
Distance Time Plots For 0,1 mode from left to right 30s, 180s, 300s for the vertical component of the velocity
Driver is 0,1 Mode with Period 300s (z Component of Velocity)
• Mainly future work! • GPU code performs well • Results provide evidence for energy leakage into the corona • fundamental mode 5 min driver (300s) effective for energy supply to the corona region and 3 min driver effective for TR • 01 mode 5 min nothing for corona and 3 min again effective for TR • 02 mode 5 min nothing for corona and 3 min effective for corona • Distance time plots illustrate cavity modes in the chromosphere • For 300s and 180s drivers clear indication of induced dynamics in the corona • Unexplained resonances e.g. for 30s driver probably resulting from non-linear behaviour • Further characterisation of the normal modes and run models with a greater range of modes of oscillation • Genuine MHD examples • Vertical B field • Horizontal B field • Flux tubes Conclusion and Future Work
• Thank you for Listening • http://uk.virginmoneygiving.com/mikeg64
Driver is 0,1 Mode with Period 30s
Driver is 0,1 Mode with Period 180s
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