Local Helioseismology of Sunspots: Current Status and Perspectives (Invited Review)
arXiv:1010.4927 · doi:10.1007/s11207-012-9996-6
Abstract
Mechanisms of the formation and stability of sunspots are among the longest-standing and intriguing puzzles of solar physics and astrophysics. Sunspots are controlled by subsurface dynamics hidden from direct observations. Recently, substantial progress in our understanding of the physics of the turbulent magnetized plasma in strong-field regions has been made by using numerical simulations and local helioseismology. Both the simulations and helioseismic measurements are extremely challenging, but it becomes clear that the key to understanding the enigma of sunspots is a synergy between models and observations. Recent observations and radiative MHD numerical models have provided a convincing explanation to the Evershed flows in sunspot penumbrae. Also, they lead to the understanding of sunspots as self-organized magnetic structures in the turbulent plasma of the upper convection zone, which are maintained by a large-scale dynamics. Local helioseismic diagnostics of sunspots still have many uncertainties, some of which are discussed in this review. However, there have been significant achievements in resolving these uncertainties, verifying the basic results by new high-resolution observations, testing the helioseismic techniques by numerical simulations, and comparing results obtained by different methods. For instance, a recent analysis of helioseismology data from the Hinode space mission has successfully resolved several uncertainties and concerns (such as the inclined-field and phase-speed filtering effects) that might affect the inferences of the subsurface wave-speed structure of sunspots and the flow pattern. It becomes clear that for the understanding of the phenomenon of sunspots it is important to further improve the helioseismology methods and investigate the whole life cycle of active regions, from magnetic-flux emergence to dissipation.
34 pages, 18 figures, submitted to Solar Physics
References in corpus (32)
- The Solar Optical Telescope for the Hinode Mission: An Overview
- Penumbral structure and outflows in simulated sunspots
- MHD simulations of penumbra fine structure
- Acoustic tomography of solar convective flows and structures
- Helioseismology of Sunspots: A Case Study of NOAA Region 9787
- Modeling the Subsurface Structure of Sunspots
- Mechanism of spontaneous formation of stable magnetic structures on the Sun
- Convection and the origin of Evershed flows in sunspot penumbrae
- High Resolution Helioseismic Imaging of Subsurface Structures and Flows of A Solar Active Region Observed by Hinode
- Photospheric and Subphotospheric Dynamics of Emerging Magnetic Flux
- Detection of sea-serpent field lines in sunspot penumbrae
- MHS sunspot model from deep sub-photospheric to chromospheric layers
- Surface Magnetism Effects in Time-Distance Helioseismology
- Sensitivity of time-distance helioseismic measurements to spatial variation of oscillation amplitudes I. Observations and a numerical model
- Radiative transfer effects on Doppler measurements as sources of surface effects in sunspot seismology
- Traveling Waves of Magnetoconvection and the Origin of the Evershed Effect in Sunspots
- Moat flow in the vicinity of sunspots for various penumbral configurations
- Constructing semi-empirical sunspot models for helioseismology
- On the Moat-Penumbra Relation
- Characterization of horizontal flows around solar pores from high-resolution time series of images
- Impact of Locally Suppressed Wave sources on helioseismic travel times
- Magnetic and Thermal Phase Shifts in the Local Helioseismology of Sunspots
- Influence of Non-Uniform Distribution of Acoustic Wavefield Strength on Time-Distance Helioseismology Measurements
- Explanation of the sea-serpent magnetic structure of sunspot penumbrae
- The three-dimensional structure of sunspots II. The moat flow at two different heights
- Towards Waveform Heliotomography: Observing Interactions of Helioseismic Waves with a Sunspot
- Surface magnetic field effects in local helioseismology
- Supersonic Evershed flow outside Sunspots
- Local helioseismology of sunspot regions: comparison of ring-diagram and time-distance results
- Numerical simulations of rotating axisymmetric sunspots
- Travel Time Shifts due to Amplitude Modulation in Time-Distance Helioseismology
- Time Distance Study of Isolated Sunspots
Cited by in corpus (5)
- Waves in the lower solar atmosphere: the dawn of next-generation solar telescopes
- Temporal Evolution of Sunspot Areas and Estimation of Related Plasma Flows
- Reconstruction of Solar Subsurfaces by Local Helioseismology
- Non-zero phase-shifts of acoustic waves in the lower solar atmosphere measured from realistic simulations and their role in local helioseismology
- A new look at sunspot formation using theory and observations