What Solar Oscillation Tell us About the Solar Minimum

TL;DR

This study analyzes helioseismic data during the recent solar minimum, revealing lower mode frequencies and delayed cycle onset, indicating a weaker solar activity compared to previous minima.

Contribution

It provides the first detailed comparison of intermediate-degree mode frequencies and flow patterns between two solar minima, highlighting differences in solar interior dynamics.

Findings

Mode frequencies are significantly lower than the previous minimum.

No signs of cycle 24 beginning until end of 2008.

Travel times are higher, indicating weaker solar activity.

Abstract

The availability of continuous helioseismic data for two consecutive solar minima has provided a unique opportunity to study the changes in the solar interior that might have led to this unusual minimum. We present preliminary analysis of inter mediate-degree mode frequencies in the 3 mHz band during the current period of minimal solar activity and show that the mode frequencies are significantly lower than those during the previous activity minimum. Our analysis do not show any signature of the beginning of cycle 24 till the end of 2008. In addition, the zonal and meridional flow patterns inferred from inverting frequencies also hint for a delayed onset of a new cycle. The estimates of travel time are higher than the previous minimum confirming a relatively weak solar activity during the current minimum.