Multitaper testing of spectral lines and the detection of the solar rotation frequency and its harmonics

We develop statistical testing methodology for closely spaced spectral line s based on multitaper spectrum estimates and apply it to a time series of s olar magnetic field magnitude data recorded by the Ulysses spacecraft. The test is formulated through complex-valued weighted least squares. Using thi s test in combination with the test for well-separated lines, we can accura tely detect the solar equatorial rotation frequency of the sun, and its har monics, from data recorded by Ulysses's magnetometer at solar mid-latitudes ; this is a potentially important result for solar physicists, since it has implications for the structure and dynamics of magnetic fields in the sola r corona.