Introduction to Helio- and Astro-Seismology
During the 1970’s, the subject of helioseismology developed rapidly as generally satisfactory theoretical explanations for the by-then frequently-observed solar 5-minute oscillation appeared in the literature (Ulrich, 1970; Leibacher and Stein, 1971; Ando and Osaki, 1975, 1977). Stated simply, the observed oscillation in the photosphere was shown to represent an evanescent wave, a response of the photosphere to standing wave pulsations in the underlying convection zone. The properties of these standing waves were determined by, and thus offered a diagnostic probe of, the physical conditions in these lower regions, thus affording the possibility of using the observed properties of these oscillations at the solar surface to determine the physical characteristics of the directly unobservable regions below. This represented a truely giant step forward in solar physics, offering an observational method for determining the nature of solar subsurface convection and differential rotation, of placing meaningful constraints on theoretical models for the postulated solar dynamo (which depends on the interaction of subsurface convection and differential rotation), and even of probing the physical conditions in the solar core, as we shall see in the following paper presented by Deubner. Thus the field of helioseismology was born.
KeywordsSolar Surface Differential Rotation Solar Dynamo Solar Interior Spherical Harmonic Degree
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