Poster for CS20.5: HELIOSEISMIC INVESTIGATIONS OF THE QUASI-BIENNIAL OSCILLATION

We investigate the behaviour of the Quasi-Biennial Oscillation (QBO) over solar Cycles 23 and 24, making use of helioseismic techniques. Using data from GONG and MDI/HMI, we see evidence of the QBO in frequency shifts of intermediate degree p-modes. By analysing the frequencies and lower turning points of these modes, we may better confine where the magnetic field driving the QBO is located. We find that evidence of the QBO exists over all frequencies and lower turning points across the full input data range (1600-4000 µHz, 0.2-1 solar radii) suggesting that the magnetic field generating the QBO must be anchored in the near surface layer. The periodicity of the QBO is roughly seen to be between 400-800 days through both Cycles 23 and 24, although its presence is weaker in Cycle 24. This data was analysed using AuTomated Empirical Mode Decomposition (ATEMD), a technique adept at extracting quasi-oscillatory signals