Solar Physics & Space Plasma Research Center (SP 2 RC)
Solar Physics & Space Plasma Research Center (SP 2 RC) Robertus Erdélyi Robertus@sheffield.ac.uk SP 2 RC, School of Mathematics & Statistics, The University of Sheffield (UK) http://robertus.staff.shef.ac.uk
Solar Physics & Space Plasma Research Center (SP 2 RC) Viktor Fedun, Gary Verth Richard Morton Chris Nelson, M-A Luna Michael Ruderman David Jess, David Kuridze Gareth Dorrian, Sergiy Shelyag Mihalis Mathioudakis Marcel Goossens PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) • Measurement of magnetic fields in the solar chromosphere/corona very difficult! • Worthwhile problem to solve due to the importance of available magnetic energy. • How accurate are force free magnetic extrapolations? E.g., Metcalf et al. (ApJ, 1995) estimate chromosphere not force free < 400 km. • Vector polarimetry technique proposed by Solanki et al. (Nature, 2003) to produce 3D magnetic maps using He I multiplet (formed near coronal base). Since discredited by Judge (A&A, 2009 ), found to give spurious results for simple test cases! • Kontar et al. (A&A, 2008) used RHESSI hard X-ray data to estimate expansion of magnetic field of flaring loop on solar limb. (> 400 km biggest error bar). PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) What is the motivation? • Source of atmospheric heating ; solar wind/particle acceleration • Understand atmospheric structures (spicules, prominences, loops, plumes, etc.) • Wave properties (speed, amplitude, spectrum) spectroscopic • Atmospheric diagnostic parameters (temperature, density) Observations • Geometric properties of waveguides imaging (structuring, shape, curvature) • Atmospheric physical parameters (B, fine structure, transport coefficients) Coronal Seismology (Roberts et al. 1984); Solar Magneto-Seismology (SMS) (Erdélyi 2006) PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) • Original MHD theory by e.g., Edwin & Roberts (1983) modelled a flux tube as a magnetic cylinder. • It was found that there are many different types standing waves, e.g., fast/slow magneto-acoustic modes in magnetically twisted cylinder (Erdélyi & Fedun 2010). Courtesy Verwichte PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) • Original MHD theory by e.g., Edwin & Roberts (1983) modelled a flux tube as a magnetic cylinder. • It was found that there are many different types (standing) MHD waves, e.g., Alfvén modes (Erdélyi & Fedun, Science 2007) Erdélyi & Fedun 2007 PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Relatively “simple” magnetic topology. MPBs appear at the merging points of granules (kG field strength). Small scale (100 - 300 km diameters). Hinode data Wijn et al. (2008) Buffeted by granules MHD waves generated! Q: What sort of photospheric motions are observed in MBPs? PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Photospheric Photospheric Chromospheric Doppler shift G-band movie Ca II movie Wedemeyer-Bhöm & D. Jess et al. (in prep) Bonet et al. (ApJ, 2008) Rouppe van der Voort (A&A, 2009) PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) • SST: Chromospheric bright point oscillations Chromosphere Photosphere Magnetic bright point group analysed by Jess, Mathioudakis, Erdélyi et al. (Science, 2009) with SST. Torsional Alfvén waves Intensity oscillations were not found! incompressible so can be detected by periodic spectral line broadening. PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Torsional Alfvén waves generated independently on each magnetic surface, for the first time, we can resolve the frequency as a function of radius in chromospheric flux tube! Q1 : Can photospheric vortex driver cause such a distribution? Q2 : What plasma structure will support such a frequency distribution? 2.72 mHz 2.49 mHz Q3 : What about plasma heating ? 2.22 mHz 2.09 mHz PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Simulations show that convection naturally leads to vortex motion at magnetic flux concentrations (see also Vogler et al. 2005 ; Carlsson et al. 2010 ). (Shelyag et al. 2010, 2011a,b) velocity vorticity magnetic field PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Full nonlinear ideal MHD simulation using Sheffield Advanced Code (SAC) . Flux tube embedded in VAL IIIC (quiet sun) atmosphere. (Fedun et al. 2011a,b,c; Erdélyi et al. 2012) PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Full nonlinear ideal MHD simulation using Sheffield Advanced Code (SAC) . Flux tube embedded in VAL IIIC (quiet sun) atmosphere. (Fedun et al. 2011a,b,c; Erdélyi et al. 2012) PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Full nonlinear ideal MHD simulation using Sheffield Advanced Code (SAC) . Flux tube embedded in VAL IIIC (quiet sun) atmosphere. (Fedun et al. 2011a,b,c; Erdélyi et al. 2012) PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Full nonlinear ideal MHD simulation using Sheffield Advanced Code (SAC) . Flux tube embedded in VAL IIIC (quiet sun) atmosphere. (Fedun et al. 2011a,b,c; Erdélyi et al. 2012) PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Detected frequency distribution. Computed frequency distribution. PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Note the different scale! Frequency distribution (black) outlines magnetic structure (orange)! Construct magnetic field in lower solar atmosphere!!! PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Magnetic field (frequency) distribution at different heights Erdélyi et al, in a final stage of preparation for submission PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Torsional Alfvén waves one can reconstruct magnetic topology in chromosphere (or elsewhere)! Q1 : Do I miss a key point? Q2 : Is the MHD approximation affecting the constructed frequency distribution? Q3 : Estimate error …? PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Even “simpler” magnetic topology. Pores appear at emerging ARs of with kG field strength and often simple geometry. Small scale (500 - 1000 km diameters). Waves generated by • Global acoustic modes • Granular buffeting • Vortex motion ROSA data Morton et al. (2011) PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Two movies: pore_1.mov of pore and pore2.mov shows intensity profile across pore with intensity threshold (straight line) ROSA data Morton et al. (2011) PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) Empirical Mode Decomposition used to derive IMFs from time series of pore size (red) and intensity (black). EMD separates out distinct timescales in time series. Direct comparison between pore size and intensity IMFs with similar timescales to find out of phase behaviour. PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) 1) Mode identification : Slow magneto-acoustic sausage body mode PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Solar Physics & Space Plasma Research Center (SP 2 RC) 1) Mode identification : Slow magneto-acoustic sausage surface mode Wave energy: • E=10 8 ergs cm 2 • ~10% transmission coeff needed! PIPA University of Sheffield http://robertus.staff.shef.ac.uk 19 – 22 June 2012, Tenerife
Recommend
More recommend
