Variation in Sun's Seismic Radius and its implication on the TSI variability
Abstract
Space-borne instruments on-board SoHO and SDO have been collecting uninterrupted helioseismic data since 1996 and are providing a unique opportunity to study changes occurring below the surface over two solar cycles, 23 and 24. Here we study the variation in solar seismic radius with the changing level of the surface magnetic activity. The seismic radius is calculated from the fundamental modes of solar oscillations utilizing the observations from SoHO/MDI and SDO/HMI. Our study suggests that the sub-surface layers shrinks with increasing magnetic activity. We interpret these changes in seismic radius to be caused by the variation of sound speed, temperature or the changes in the super-adiabatic superficial layers. Our estimated maximum change in seismic radius during a solar cycle is about 5 kilometers, and is consistent in both solar cycles 23 and 24. We also explore the relationship between seismic solar radius and the total solar irradiance (TSI) and find that the radius variation plays a secondary role in TSI variability. We further observe that the solar irradiance increases with decreasing seismic radius, however the anti-correlation between them is moderately weak.
- Publication:
-
Catalyzing Solar Connections
- Pub Date:
- November 2018
- Bibcode:
- 2018csc..confE.131J