Solar Modes in the Interplanetary Medium

Because very low frequency solar modes provide the only way to determine conditions in the Sun's core, their detection and accurately measuring their frequencies has been described by Chaplin as the "Holy Grail of observational helioseismology" A recent review paper (Appourchaux 2010) concludes that "there is currently no undisputed detections of solar g modes". Reported here is an update on the study of frequencies in the interplanetary medium in the range of expected normal modes of the Sun. Data from several instruments on the ACE and Ulysses spacecraft are time series analyzed and inter-compared. Doing a combined search of the spectra in both frequency and frequency splitting (and allowing for known frequency shifts due to the different orbits of the two spacecraft) we find several instances where the same frequencies (modes) are detected in two and more data sets at high confidence levels on both spacecraft. The frequencies occur reasonably close to predicted solar mode frequencies. Moreover, these detections include all 2l+1 singlets expected for modes of degree l at high significance levels. Implications for the interplanetary medium and for the internal structure of the Sun will be presented.