Solar Magnetic Fields

Recent Research by the Indian Institute of Astrophysics (IIA):

• Methodology:
  • The study focused on an active sunspot region with complex features, including multiple umbrae and a penumbra.
  • Simultaneous observations were conducted using the Hydrogen-alpha (6562.8 Å) and Calcium II 8662 Å spectral lines.
• Findings:
  • These observations provided insights into the magnetic field’s stratification across different heights of the solar atmosphere.
  • The use of the Tunnel Telescope's unique 3-mirror Coelostat setup enabled precise tracking of the Sun and enhanced data accuracy.

Technological insights:

• Tunnel Telescope Setup: The primary mirror (M1) tracks the Sun's movement, while the secondary (M2) and tertiary mirrors (M3) direct and align the sunlight for observation.
  • An achromatic doublet lens focuses the Sun's image with high precision, allowing detailed analysis.
• Limitations of traditional diagnostic probes:
  • While Calcium II 8542 Å and Helium I 10830 Å lines are commonly used to infer chromospheric magnetic fields, they have limitations in their applicability across various solar features.
  • The new method using Hydrogen-alpha and Calcium II 8662 Å lines offers a more comprehensive understanding of solar magnetic fields.

About Solar Magnetic Fields:

• The Sun’s magnetism is crucial in understanding its various activities and phenomena. Magnetic fields in the Sun are generated by the movement of electrically charged particles, specifically ions and electrons.
  • These fields influence almost every feature observed on the Sun, including sunspots, prominences, and coronal loops.
• Layers of the Solar Atmosphere: The Sun’s atmosphere consists of multiple layers: the photosphere, chromosphere, and corona.
  • The magnetic fields interlink these layers, channeling energy from the lower to the upper layers, contributing to processes like coronal heating.
• Sunspots: Sunspots are regions on the Sun’s surface where magnetic fields are extremely concentrated. These fields break through the surface, leading to cooler areas that appear darker.
  • The sunspot cycle, lasting approximately 11 years, results from the recycling of these magnetic fields through the solar interior.
• Chromospheric and Coronal Magnetic Fields: Magnetic field lines loop through the Sun's atmosphere, forming complex structures in the chromosphere and
  • While these magnetic structures are visible in the outer layers, the fields themselves are typically measured in the photosphere, the Sun’s innermost atmospheric layer.
• Measurement techniques: The Sun’s magnetic field is measured by observing the energy difference in light emitted by electrons as they move between orbits within an atom.
  • Specialised instruments like magnetometers determine the magnetic field's strength and direction across the Sun’s surface.