The technique that was perfected in this period, however, was visual observation, which was carried out with enthusiasm and reported so eloquently that we who depend on photographs to record our observations return to the writings of the nineteenth century for adequate verbal descriptions of the corona. The corona was recognized as an object worthy of study, and the familiar techniques for analysis of light-photography, photometry, spectroscopy and polarimetry-were all applied to it. ![]() In his 1966 book on the solar corona, Donald Billings described this period: … the latter 60 years of the 19th century marked the beginning of a real coronal science. The former were carefully reported in written accounts and recorded in drawings and engravings that depended on the skills of astronomers, artists and engravers, as well as those who made and reproduced the pictures. In the first, during the latter half of the 19th century, naked-eye observations were only occasionally supplemented by photography. Once we understand those processes, we may be able to predict the eruptions, which will help us protect our technology.Eclipse studies of the white-light corona can be grouped roughly into three periods. The researchers hope that now that we can map the corona’s magnetic field, we can work on understanding the processes that lead to eruptions which blast charged particles towards Earth that can damage our satellites and power grids. “The magnetic fields can get twisted and tangled and they can cause eruptions, which can be impactful to Earth, to satellites, GPS systems, power grids.” “These are very small magnetic fields, but they’re important nonetheless,” says Tomczyk. They found it was between 1 and 4 gauss, which is more than 10 times weaker than the magnetic field of a typical refrigerator magnet. The waves are caused by magnetic fields, and their speed is dependent on the plasma density and the magnetic field strengths, so those measurements allowed the researchers to calculate the magnetic field strength across the corona. Read more: The sun is too quiet, which may mean dangerous solar storms in future They also measured the speed of waves that move through the corona like ripples on the ocean. This allowed the team to measure the density of its plasma. Steven Tomczyk at the US National Center for Atmospheric Research in Colorado and his colleagues used a ground-based instrument called the Coronal Multi-channel Polarimeter to block out the light from the sun’s disk so the fainter corona wasn’t lost in its glare. That tenuousness, along with the brightness of the disk of the sun, also makes it tough to measure. The plasma – a hot, ionised state of matter – that makes up the corona is incredibly tenuous, which is why it isn’t visible with the naked eye except during a total solar eclipse. This will help us predict solar flares that potentially threaten Earth. The outermost layer of the sun, called the corona, is extraordinarily difficult to study, but now researchers have made the first map of its magnetic field. ![]() ![]() The magnetic field of the sun’s corona has been mapped for the first time
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