An international team of solar physicists, including scientists from the University of Northumbria, recently measured for the first time the global magnetic field of the sun’s outermost atmosphere, the solar corona. The team, which included researchers from Peking University and the National Center for Atmospheric Research (NCAR), used a coronal multichannel polarimeter (CoMP) to observe. It is an instrument that can provide measurements of infrared radiation emanating from the Sun’s atmosphere. Research scientists published in the journal Science.
The sun is a magnetized star, and its magnetic field plays a crucial role in shaping the solar atmosphere. The magnetic field determines many aspects of the Sun’s behavior, leading to an 11-year solar cycle, spectacular solar eruptions, and the heating of hot gas (plasma) in the solar corona to millions of degrees Celsius.
The magnetic field penetrates the various layers of the Sun’s atmosphere, which means that information about the magnetic field of the entire atmosphere is necessary to understand the interaction between the solar plasma and the magnetic field. Until now, however, conventional measurements of the Sun’s magnetic field have only been carried out on the surface of our star – a region of the Sun known as the photosphere.
Although more than 100 years have passed since the first measurement of the Sun’s magnetic field, we still do not have accurate information about the magnetic field in the upper layers of the Sun’s atmosphere, especially the corona.
More than 20 years ago, the magnetoseismology method was proposed as a way to measure the magnetic field in the corona. This method uses Alfven magnetic waves, transverse magnetohydrodynamic plasma waves, propagating along the lines of force of the magnetic field.
It is important to note that the speed of propagation of waves is dependent on the strength of the magnetic field, which means that being able to measure how fast they propagate allows you to estimate the magnetic field.
Dr. Richard Morton, the future UKRI Research Fellow at the University of Northumbria, is a global expert in the observation and analysis of waves in the Sun’s corona and was part of the team that produced these exciting results. He has long used the CoMP instrument and advocated increasing the frequency of such measurements to study the solar magnetic field.
CoMP data shows that the Sun’s corona is full of these Alfvén waves and gives us the best view of them available.
Dr. Richard Morton, future UKRI Research Fellow at the University of Northumbria
The current research builds on earlier work by Dr. Morton, which demonstrated the use of magnetic waves as a tool. He also stated that his research is an excellent demonstration of how scientists can use Alfvén waves to study the properties of the Sun. The process is similar to how seismologists use earthquakes to figure out what is inside the earth.
This is the first time that a global map of the coronal magnetic field has been obtained through real coronal observations, which marks a step towards solving the problem of coronal magnetic field measurements.
In principle, with the help of this technique, it is now possible to obtain maps of the global coronal magnetic field in the usual way, filling in the missing part of the measurements of the global magnetism of the Sun.
In addition, synoptic corona magnetograms can provide important information for a deeper understanding of how the magnetic field binds different layers of the Sun’s atmosphere, as well as the physical mechanisms responsible for solar eruptions and the solar cycle.