The sun in a noncycling state

Abstract

Using the Baliunas and Jastrow (1990) study of cyclic variability in solar-type stars, we transform existing solar data to the stellar HK irradiance scale and examine the state of the solar chromosphere when a solar-type star shows little cyclic variability and surface magnetism. To reduce the chromospheric emission to levels for G-type stars showing no chromospheric activity cycles, not only must the Sun be free of plages and network; the brightness of the quiet chromosphere in the Κ line must be reduced to levels seen only in 15% of the quiet Sun area today. In contrast, the present-day level of Κ emission from the Sun places it in the class of most active solar-type stars, far removed from a noncycling state.