Evidence of global circulation currents from solar-limb temperature variations

Abstract

The temperature distribution in a turbulent rotating photosphere is non-spherical. Dimensional arguments for the Sun suggest that such a temperature modulation may have an amplitude ΔT≈ Tv²/Φ≈0.1 K, where T is an average temperature (5,700 K) and v²/Φ is the ratio of the rotational kinetic and potential energy density of the photosphere. Detailed calculations^1–3 generally support this expectation. Here we report new observations that should help to understand the solar global dynamics problem. From about 1,400 h of solar-limb data obtained during the summers of 1983–85 we find that the solar-limb temperature variation is not spherically symmetric and is ∼1 K. Our results also indicate that the limb temperature departs from its expected l = 2 spatial harmonic form and has, at most, a weak dependence on solar cycle.