Global magnetic field of the solar corona measured for the first time
An international team of solar physicists, including academics from Northumbria University, in Newcastle upon Tyne, has recently measured the global magnetic field of the outer most layer of the Sun’s atmosphere, the solar corona, for the first time
An international team of solar physicists, including academics from Northumbria University, in Newcastle upon Tyne, has recently measured the global magnetic field of the outer most layer of the Sun’s atmosphere, the solar corona, for the first time.
The team, including researchers from Peking University, China and National Center for Atmospheric Research (NCAR), U.S., used observations from the Coronal Multi-channel Polarimeter (CoMP), an instrument that can provide measurements of infrared radiation coming from the Sun’s atmosphere. Their research has just been published in the journal Science.
The Sun is a magnetized star, and its magnetic field plays a critical role in shaping the solar atmosphere. The magnetic field governs many aspects of the Sun’s behaviour, leading to an 11-year solar cycle, spectacular solar eruptions, and the heating of the hot gas (plasma) in the solar corona to millions of degrees Celsius.
The magnetic field threads through the different layers of the Sun’s atmosphere, which means that information on the magnetic field of the whole atmosphere is required in order to understand the interplay between the solar plasma and magnetic field.
However, up until now, routine measurements of the solar magnetic field have only been achieved at the surface of our star (the area of the Sun known as the photosphere).
While more than 100 years has passed since 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
More than 20 years ago, a technique called magnetoseismology was put forward as a way to measure the magnetic field in the corona. This method makes use of magnetic waves, known as Alfvén waves, that are observed to travel along the magnetic fields.
Importantly, the speed the waves travel at depends on the strength of the magnetic field, meaning that being able to measure how fast they travel enables an estimate of the magnetic field to made.
Dr. Richard Morton, a UKRI Future Leader Fellow working at Northumbria University, is a world expert in the observation and analysis of waves in the Sun’s corona and was part of the team which delivered these exciting results.