Cross-Spectral Fitting of HMI Velocity and Intensity Data
Abstract
The simultaneous HMI velocity and intensity observations are used to obtain better estimates of solar acoustic mode parameters. This is achieved by fitting four spectra simultaneously viz. velocity, intensity, the phase difference and the coherence between the intensity and velocity spectra. We further compare the oscillation mode parameters obtained from the single-observable fitting and those from the cross-spectral fitting method. We find that the mode frequencies derived from the cross-spectral procedure are lower than those derived from the velocity spectrum fitted with an asymmetrical profile. We further note a clear solar cycle dependence in the mode frequencies while other mode parameters e.g. amplitudes and line widths do not show significant variation with solar activity. This corroborates earlier findings that the interpretation of model fit parameters based on measurements of a single spectra should be examined critically.
- Publication:
-
SDO 2016: Unraveling the Sun's Complexity
- Pub Date:
- October 2016
- Bibcode:
- 2016usc..confE..84T
- Keywords:
-
- SDO;
- SDO 2016;
- Solar Dynamic Observatory;
- SDO-2016;
- SDO Workshop;
- SDO 2016: Unraveling the Sun's Complexity