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On measuring low-degree p-mode frequency splitting with full-disc integrated data

Appourchaux, T.; Gough, D. O.; Sekii, T. +1 more

The standard method of measuring rotational splitting from solar full-disc oscillation data, based on maximum-likelihood fitting of multi-Lorentzian profiles to oscillation power spectra, systematically overestimates the splitting. One of the reasons is that the maximum likelihood estimators (MLE) become unbiased only asymptotically as the number …

Source of excitation of low-l solar p modes: characteristics and solar-cycle variations

Chaplin, W. J.; Elsworth, Y.; Appourchaux, T. +3 more

We investigate various properties of the excitation source that is responsible for driving the acoustic p-mode oscillations of the Sun. Current prejudice places this in the superadiabatic layer of the convection zone. We consider in detail how the precise nature of the resonant mode spectrum is modified: (i) as a result of the impact of different …

Bulk flow velocities in the solar corona

Simnett, G. M.; Lewis, D. J.

We present velocity estimates of bulk motions in the solar corona using data from the Large Angle Spectrometric Coronagraph (LASCO) aboard the Solar and Heliospheric Observatory spacecraft (SOHO). We describe a new technique which automatically provides a mass-weighted mean velocity profile in an entirely objective fashion without the need for ind…