In the realm of solar physics and helioseismology, understanding the nuances of solar oscillations and dynamics is crucial for improving our knowledge of the Sun’s interior and its impact on space weather. Dr. Irina N. Kitiashvili, a researcher at the Bay Area Environmental Research Institute in collaboration with NASA’s Ames Research Center, has been delving into the complexities of helioseismic data, particularly the center-to-limb variations observed in solar observations. Her work, published in the journal Solar Physics, offers valuable insights that could refine our interpretation of solar data and enhance our predictive capabilities for space weather events.
Dr. Kitiashvili’s research focuses on the systematic variations in helioseismic and photospheric data as observed from the center of the solar disk to its limbs. These variations, known as center-to-limb effects, can complicate the interpretation of data collected by missions such as the Solar Dynamics Observatory (SDO) and the Solar and Heliospheric Observatory (SOHO). To unravel the physical origins of these effects, Dr. Kitiashvili and her team conducted local 3D radiative hydrodynamic simulations. These simulations incorporated the effects of solar rotation to generate synthetic time series of continuum intensity and Doppler velocity for various viewing angles, spanning from -75 to 75 degrees.
The simulations revealed several key findings. Firstly, there is a systematic decrease in oscillation power toward the solar limbs. Additionally, a pronounced East-West asymmetry was observed, which increases with frequency and is primarily attributed to rotation-induced flows. As the angular distance from the disk center increases, the amplitudes and widths of the surface gravity (f) and resonant pressure (p) modes decrease. Conversely, the amplitudes of the corresponding pseudo-modes, which have frequencies above the acoustic cut-off frequency, increase in the intensity power spectra but are suppressed in the velocity spectra.
The research also demonstrated that local helioseismology ring-diagram analysis of the simulation data shows anisotropic broadening of the modes and distinct differences in background noise and pseudo-mode structure between the intensity and velocity data. These findings suggest that center-to-limb effects arise from both geometric projection and physical factors such as line-formation height and potential effects of the radial differential rotation.
The practical implications of this research for the energy sector, particularly in space weather prediction, are significant. Accurate interpretation of helioseismic data is essential for understanding the Sun’s interior dynamics and predicting solar activity, which can impact satellite operations, power grids, and other critical infrastructure. By providing a framework for correcting helioseismic observations, Dr. Kitiashvili’s work contributes to the development of more reliable space weather forecasting models. This, in turn, can help energy companies and other stakeholders better prepare for and mitigate the effects of solar storms and other space weather events.
In summary, Dr. Irina N. Kitiashvili’s research offers valuable insights into the center-to-limb effects in helioseismic data, highlighting the importance of realistic 3D radiative hydrodynamic simulations in disentangling geometric and physical biases in solar data. Her findings, published in Solar Physics, provide a framework for correcting helioseismic observations and improving our understanding of solar dynamics, ultimately enhancing our predictive capabilities for space weather events and their impact on the energy sector.
This article is based on research available at arXiv.