Observations of high-frequency and high-wavenumber solar oscillations

Doppler shift measurements of the Na D1 absorption line have revealed solar oscillations in a new regime of frequency and wavenumber. Oscillations of vertical velocities in the temperature minimum and low chromosphere of the Sun are observed with frequencies ranging up to 9.5 mHz. The fundamental modes appear with wavenumbers up to 5.33 1/Mm (equivalent spherical harmonic degree 3710). No evidence are found for chromospheric modes of 3 minute period