Magnetic Fields in the Sun’s Atmosphere: A New Discovery

Magnetic Fields in the Sun’s Atmosphere: A New Discovery

Sub: Sci

Sec: Space

Why It’s in the News

A recent breakthrough has been achieved in understanding the Sun’s atmosphere by examining the magnetic fields across its various layers. The Kodaikanal Tower Tunnel Telescope provided crucial data that has opened new avenues for exploring solar phenomena.

Overview of the Solar Atmosphere

• Composition: The solar atmosphere consists of several layers, all interconnected by magnetic fields.
• Role of Magnetic Fields: These fields act as channels, transferring energy and mass from the Sun’s inner layers to its outer layers. This process is integral to understanding the “coronal heating problem” and the generation of solar wind.

Importance of Magnetic Field Measurements

• Understanding Solar Processes: Measuring the magnetic fields at different heights within the solar atmosphere is vital for deciphering the physical mechanisms driving solar phenomena.
• Magnetic Field Strength: The intensity of these magnetic fields can be deduced from precise measurements of spectral line intensities across the Sun, conducted in full polarization.

Techniques Used

• Simultaneous Multiline Spectropolarimetry:
  • This observational technique allows scientists to capture the magnetic field at different layers of the solar atmosphere simultaneously.
  • Recent studies have shown its effectiveness in detailing the magnetic structures associated with sunspots, umbral flashes, and chromospheric variations during solar flares.

Significance of the Findings

The new method provides a deeper understanding of the Sun’s magnetic structure, offering insights into long-standing solar mysteries such as coronal heating and solar wind generation. This advancement enhances our ability to predict solar activity and its effects on space weather.

Study Overview

• Institution Involved: The study was conducted by the Indian Institute of Astrophysics, an autonomous body under the Department of Science and Technology (DST).
• Focus Area: The study examined a sunspot characterized by multiple umbrae and a penumbra, highlighting the intricate nature of this active solar region.
• Observational Techniques:
  • Simultaneous Observations: Observations were made using the Hydrogen-alpha line at 6562.8 Å and the Calcium II 8662 Å line.
  • Telescope Used: Data were gathered using the Kodaikanal Tower Tunnel Telescope at the Kodaikanal Solar Observatory (KoSO).

Significance of the Study

• Magnetic Field Stratification: The study provided insights into the magnetic field’s stratification at different heights within the solar atmosphere. This was made possible by the simultaneous observation of multiple spectral lines.
• Contribution to Solar Physics: The findings enhance our understanding of the magnetic structures associated with sunspots, which play a crucial role in solar activity.

Key Takeaways from the Telescope’s Mirror Setup and Findings

1. Mirror Setup:
   • The Tunnel Telescope uses a three-mirror system where the primary mirror (M1) tracks the Sun.
   • The secondary mirror (M2) redirects sunlight downwards.
   • The tertiary mirror (M3) makes the sunlight beam horizontal.
2. Coelostat Mechanism:
   • The setup, where the primary mirror rotates to track the Sun, is known as a Coelostat.
   • An achromatic doublet with a 38 cm aperture focuses the Sun’s image at a distance of 36 meters.
3. Probing the Chromospheric Magnetic Field:
   • Traditional diagnostic probes like the Calcium II 8542 Å and Helium I 10830 Å lines are used to infer the chromospheric magnetic field but have limitations in diverse solar features.
   • The Hydrogen-alpha (Hα) line, however, is more effective in probing the chromospheric magnetic field as it is less sensitive to local temperature fluctuations.
   • This makes the Hα line particularly useful in studying solar phenomena like flaring active regions, where sudden temperature changes occur.

Importance of a Multi-Line Approach

• Magnetic Field Stratification: The study emphasizes the need for a multi-line approach to fully understand the complex stratification of magnetic fields in the Sun’s chromosphere.

Call for Advanced Observations

• Future Observational Needs:
  • The study calls for further spectropolarimetric observations of the Hα line using cutting-edge telescopes with superior spatial and spectral resolution.
  • Potential Telescopes:
    • Daniel K. Inouye Solar Telescope (DKIST): Currently operational.
    • European Solar Telescope (EST): A future facility in development.
    • National Large Solar Telescope (NLST): A proposed 2-meter class optical and near-infrared telescope to be built in Merak, Ladakh, India.

National Large Solar Telescope (NLST):

1. Purpose: The NLST is designed as a ground-based 2-meter class optical and near-infrared (IR) observational facility aimed at studying the Sun’s magnetic fields and other solar phenomena with high precision.
2. Location: The proposed site for the NLST is Merak village in Ladakh, India. This location is chosen for its high altitude and clear skies, which are ideal for solar observations.
3. Research Focus: The NLST will focus on studying the solar atmosphere, particularly the chromosphere and photosphere, to understand magnetic field stratification and solar activity, such as flares and sunspots.
4. Technological Advancements: The telescope will feature advanced spectropolarimetric capabilities, allowing for high-resolution observations of the Sun’s magnetic fields across different atmospheric layers.
5. Global Collaboration: The NLST is expected to collaborate with other leading solar telescopes worldwide, such as the Daniel K. Inouye Solar Telescope (DKIST) and the European Solar Telescope (EST), contributing to global efforts in solar research.

Understanding the Solar Cycle

• The Solar Cycle: A solar cycle is a roughly 11-year cycle in which the Sun’s magnetic activity increases and decreases. This cycle influences various solar phenomena, including sunspots, solar flares, and the solar wind.

Phases of the Solar Cycle

Sunspots and the Solar Cycle

• Sunspot Count: The number of sunspots on the Sun’s surface is a key indicator of the solar cycle. Sunspot numbers rise during the solar maximum and decline during the solar minimum.

Impact on Earth

• Space Weather: The solar cycle affects space weather, which can influence satellite operations, communication systems, and even power grids on Earth.
• Auroras: Increased solar activity during the solar maximum can lead to more frequent and intense auroras (Northern and Southern Lights).

Historical Observations

• First Observed: The solar cycle was first observed by scientists in the 18th century, and it has been systematically studied since then.
• Current Cycle: As of 2024, we are in Solar Cycle 25, which began in December 2019 and is expected to peak around 2025.

Understanding the solar cycle is crucial for predicting space weather and preparing for its potential impacts on modern technology.