Abstract:

Thirteen years ago, I scoured MDI data for characteristics of MHD waves in the solar photosphere.  The results of that work were mostly negative.  Some problems were instrumental (spatial registration of the optics), others were physical mechanisms in the solar atmosphere that could mimic MHD waves (opacity fluctuations sampling a vertical gradient of dB/dz in time), others were due to extended temporal sampling of the spectral line (acceleration affects).  Luckily, the HMI team improved upon MDI with better spatial registration of HMI optics and removal of the acceleration effects through temporal interpolation.  Meanwhile, other people pursued the topic using Hinode-SOT (Fujimura & Tsuneta, 2009) and the ASP (Settele, Sigwarth, Muglach 2002) and others with encouraging results.  Preliminary analysis with HMI magnetogram data shows oscillations are present above the noise in the line-of-sight magnetic component.  Compared with MDI, I find reduced rms amplitudes of magnetic oscillations near 3.3 mHz and a finer spatial isolation of phase relationships between the velocity and magnetic field oscillations.