Investigating Solar Minimum Below and Above the Solar Surface: Is the Current Solar Minimum Different from the Previous Minimum?

Abstract:

The Solar magnetic field waxes and wanes with time, going through a cyclic change with a period of about 11 years, commonly known as the Solar Cycle. Other indicators of solar activity follow a similar trend, as inferred from direct measurements above the solar surface. However, there are no direct methods to measure magnetic fields or other forms of solar activity below the surface. Past studies have demonstrated strong correlations between the variations in oscillation frequencies of the waves propagating below the Sun’s surface and above-surface magnetic activity indicators, therefore the frequencies serve as an activity proxy for the interior. We use oscillation frequencies derived from the Global Oscillation Network Group’s (GONG) observations to study the conditions in the convection zone while various indicators of the solar activity are used for above surface conditions. We have identified the previous minimum, between cycles 23 and 24, was deeper than the current minimum, while the current minimum is wider. In addition, similar to the previous minimum, different layers in the convection zone during the current minimum sensed minima at different times.

This work is carried out through the National Solar Observatory Research Experiences for Undergraduates (REU) Program, which is funded by the National Science Foundation (NSF) through Award No. 1659878.