Spatial and temporal variations in the solar brightness

We have investigated long-term variations of solar brightness as a function of both time and solar latitude using eight years of ground-based photometric data in conjunction with space-based irradiance data. In particular, we have examined whether the combination of sunspot brightness deficits and facular brightness excesses is sufficient to explain the solar cycle irradiance variations. After correcting for the contribution from sunspots, we find that the irradiance data can be adequately explained by a model in which the remaining brightness variations are due entirely to facular contributions confined to the magnetically active latitudes. Thus we find no support for the hypothesis that there are convectively driven hot bands in the active latitudes, and our data show brightness variations that are well described by a facular contrast function.     

Practical considerations for the generation of large-order spherical harmonics

Techniques for generating large-order Y _l ^m (, ) are discussed.     

A search for acoustic amplitude deficit at the antipodes of sunspots

We present a search for the acoustic oscillation deficit which may exist at the antipodes of sunspots. Dopplergrams from Big Bear Solar Observatory 1988 helioseismology data were selected for five days on which large sunspots were known to be on the unseen hemisphere of the Sun. Acoustic oscillation amplitudes in the antipodal regions of these sunspots were compared with amplitudes in surrounding quiet-Sun regions. We did not detect a statistically significant acoustic amplitude deficit in our data. Our results indicate that the amplitude deficit at the sunspot antipodal points is limited to no more than 3% of the acoustic amplitude in the region, for solar oscillation modes of spherical harmonic degree l 200. We conclude that no strong acoustic deficit exists at the antipodes of sunspots. A more sensitive search, requiring more elaborate observations than we have performed, would be desirable in order to determine if a weak acoustic amplitude deficit exists at some level at the antipodes of sunspots, perhaps at higher spatial frequencies of oscillation. The noise level in any signals detected by such observations would probably limit their usefulness as seismic probes. However, information on the lifetimes of solar oscillation modes can be deduced even if no acoustic amplitude deficit is detected.