Context: An international team of solar physicists has measured the global magnetic field of the Sun’s corona, or outer atmosphere, for the very first time.
Background: The Sun is Earth’s closest star which is made up mostly of hydrogen, followed by helium.
- Temperature:The visible part of the sun is about 10,000 degrees Fahrenheit (5,500 degrees Celsius), while temperatures in the core reach more than 27 million F (15 million C), driven by nuclear reactions.
- Sun’s atmosphere: The solar interior, from the inside out, is made up of the core, radiative zone and the convective zone.
- The solar atmosphere above consists of the photosphere, chromosphere, a transition region and the corona.
- Beyond that is the solar wind, an outflow of gas from the corona.
There are two main puzzles about the Sun.
- The coronal heating problem: The core of the Sun is at a temperature of about 15 million degrees, its outer layer, the photosphere is only 5700 degrees hot.
- However, its corona or outer atmosphere is at a much much higher temperature of about one million degrees.
- Scientists believe that the magnetic field of the corona causes the atmosphere of the Sun (corona) to heat up.
- The strength of the sun's magnetic field is typically only about twice as strong as Earth's field. However, it becomes highly concentrated in small areas, reaching up to 3,000 times stronger than usual.
- Solar flares and coronal mass ejections: These are driven by magnetic reconnections happening in the Sun’s corona.
- Magnetic reconnection is a process where oppositely polarity magnetic field lines connect and some of the magnetic energy is converted to heat energy and kinetic energy generating heating, solar flares, solar jets, etc.
About the experiment
Coronal seismology or magneto-seismology was used to measure the coronal magnetic field.
It measures the properties of magnetohydrodynamic (MHD) waves and the density of the corona simultaneously.
- These waves propagate through a magnetic plasma. Once the wave properties and the density of the corona are measured, then scientists can compute the magnetic fields in the corona.
- Instrument used: The experiment used the Coronal Multi-channel Polarimeter (CoMP) is an instrument operated by High Altitude Observatory, of the U.S.
- It is located at Mauna Loa Solar Observatory, near the summit of that volcano on the big island of Hawaii.
Significance of experiment:
- It is very important to measure the corneal magnetic fields regularly since the solar corona is highly dynamic and varies within seconds to a minute time scale.
- The measurement of global coronal magnetic fields was missing in the past since the coronal magnetic fields are very weak.
While ground-based measurements pose challenges, India’s first solar mission, Aditya-L1 satellite will aim to measure the solar coronal magnetic fields regularly.
Image Source: NASA
The Aditya-1 mission
A Satellite placed in the halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system has the major advantage of continuously viewing the Sun without any occultation/ eclipses.
The Aditya-1 mission has now been revised to “Aditya-L1 mission” and will be inserted in a halo orbit around the L1, which is 1.5 million km from the Earth.
The satellite carries additional six payloads with enhanced science scope and objectives.
- Objectives: Aditya-L1 with additional experiments can now provide observations of Sun's Corona (soft and hard X-ray, Emission lines in the visible and NIR), Chromosphere (UV) and photosphere (broadband filters).
Wave is a propagation of disturbances from place to place in a regular and organized way.
For example, surface waves that travel on water, sound, light, and the motion of subatomic particles all exhibit wavelike properties.
- Waves can be longitudinal waves (for example, sound waves) or transverse waves (for example, ripples on a lake surface).
The properties of waves depend on the medium in which they travel.
- By measuring certain wave properties, some of the properties of the medium through which they have travelled can be obtained.