Jean-François Cossette, Université de Montréal
Résumé/abstract:
Total solar irradiance (TSI) is the total power of the solar electromagnetic radiation integrated over all wavelengths that is received per unit area by a detector placed at 1 AU from the Sun. The TSI has been measured almost continuously since the 1980s by several space instruments and is now know to vary in phase with the 11-year solar sunspot number with an amplitude corresponding to 0.1 percent of its mean value. Although most of the variability can be explained by taking into account cumulative effects of sunspots, faculae and other magnetic structures present at the Sun's surface, the question whether or not global structural changes of the star may also contribute to the irradiance cycle remains unanswered. Recent global MHD simulations of the solar convection zone (SCZ) produced large-scale magnetic cycles with polarity reversals similar in many aspects to those observed on the Sun. These simulations also show a thermal signature pervading the whole SCZ that varies in phase with the magnetic cycle and therefore offer the chance to assess the impact that global structural changes would have on TSI fluctuations.
Ce séminaire est présenté par le groupe astronomie et astrophysique du Département de physique de l'Université de Montréal.
