Solar Radial Velocity and Oscillations as Measured by Sodium and Potassium Resonant Scattering Spectrometers
Since the beginning of 1990, a sodium based resonance scattering spectrometer belonging to the IRIS Network has operated at Observatorio del Teide side by side with the MkI instrument (a resonance scattering spectrometer based on potassium) from the University of Birmingham and operated since 1975. A 3 month series of simultaneous data obtained in summer 1990 is the basis for this study that compares the performance of both instruments in measuring the solar radial velocity and oscillations. Interesting features of the p-modes as seen at two different levels of the solar atmosphere such as the ratio of energies per unit mass and the difference of phases are obtained. These results demonstrate that the p-modes are truly standing waves. Crosscorrelation of the spectra of the series obtained with both instruments shows the existence of signals well above the cutoff frequency of the solar atmosphere, being interpreted as travelling waves, also called pseudomodes. An estimation of the cutoff frequency gives a value of 5.6 ± 0.1 mHz, higher than theoretically predicted.
Astronomy and Astrophysics
- Pub Date:
- February 1992
- solar oscillations - spectrophotometry