Sun density
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Sun Density: Insights from Recent Research
Dark Matter Density at the Sun's Location
Local Centrifugal Equilibrium Method
Recent research has provided a reliable estimate of the dark matter density at the Sun's location using a method based on local centrifugal equilibrium. This approach is advantageous as it does not require a global mass model of the Galaxy and is independent of the dark matter density profile's shape, the rotation curve from the galaxy center to the virial radius, and the complexities of bulge/disk/dark halo mass decomposition. The derived dark matter density at the Sun's location is approximately 0.43 GeV/cm³, with uncertainties stemming from the slope of the circular-velocity and the ratio between the Sun's radius and the stellar exponential thin disk's length scale.
Density Structure in the Solar Corona
Radial Evolution of Density
The solar corona's density structure has been studied using white-light measurements from the SOHO coronagraphs and the HAO Mauna Loa Mk III K-coronameter. These observations reveal that the density structure at the Sun's surface extends radially into interplanetary space, maintaining the same density gradient. This radial evolution is consistent across both coronal hole and quiet Sun regions, except for coronal streamers, which transform into the heliospheric current sheet within a few solar radii.
Electron Densities in the Inner Corona
Further insights into the solar corona's density come from analyzing electron densities using density-sensitive line ratios in the N I isoelectronic sequence. Studies have shown that the average electron density in the inner corona, derived from S x lines, is about 1.0 x 10⁸ cm⁻³ at heights greater than 8" above the white-light limb. This density remains consistent across both quiet Sun and active regions.
Core Density of the Sun
High Density and Temperature
The Sun's core, the innermost layer, is characterized by extreme conditions. It has a density approximately 160 times that of water and a temperature of about 16 million K. The core, which constitutes about 10% of the Sun's mass, is the site of nuclear fusion, generating the Sun's energy. The high density and temperature are a result of the immense gravitational compression from the overlying layers.
Conclusion
The density of the Sun and its surrounding regions varies significantly from the core to the outer corona. The core exhibits extremely high density and temperature due to gravitational compression, while the solar corona's density structure extends radially into space, maintaining a consistent gradient. Additionally, the dark matter density at the Sun's location has been reliably estimated using local centrifugal equilibrium methods, providing valuable insights into the Sun's immediate environment. These findings collectively enhance our understanding of the Sun's density profile and its implications for solar and galactic dynamics.
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