Scientists measured the global magnetic field of the solar corona

A wonderful demonstration of how we can exploit the Alfvén waves.

Using observations from the Coronal Multi-channel Polarimeter (CoMP), an international team of solar physicists has recently measured the global magnetic field of the outermost layer of the Sun’s atmosphere, the solar corona.

Until now, routine measurements of the solar magnetic field have only been achieved at the surface of our star. Its been more than a century for the first measurement of the Sun’s magnetic field. We still do not have a precise knowledge of the magnetic field in the upper solar atmosphere, especially the corona.

About two decades ago, a technique called magneto seismology came out to measure the magnetic field in the corona. This method uses magnetic waves, known as Alfvén waves, that are observed to travel along with the magnetic fields.

Dr. Richard Morton, a UKRI Future Leader Fellow, working at Northumbria University, said, “The data that is collected from CoMP reveals the Sun’s corona is full of these Alfvén waves and provides us with the best available view of them.”

“I think that this is a wonderful demonstration of how we can exploit the Alfvén waves to probe the properties of the Sun. The process is similar to how seismologists use earthquakes to find out what the interior of the Earth looks like.”

Coronal magnetic field lines obtained from the PFSS model
Coronal magnetic field lines obtained from the PFSS model. Credit: Z.-H. Yang et al., Science (2020)

“This is the first time that a global map of the coronal magnetic field has been obtained through actual coronal observations, thus marking a leap towards solving the problem of coronal magnetic field measurements.”

Together with simultaneously measured magnetic field measurements from the Sun’s surface, these synoptic coronal magnetograms will provide critical information to advance the understanding of how the magnetic field couples the different layers of the Sun’s atmosphere as well as the physical mechanisms responsible for solar eruptions and solar cycle.

Journal Reference:
  1. Z. Yang el al. Global maps of the magnetic field in the solar corona. DOI: 10.1126/science.abb4462

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