A team of Indian scientists have discovered the first evidence of solitary waves in the Martian magnetosphere — the space around a planet that is controlled by its magnetic field.
The solitary waves are mainly distinct electric field fluctuations in Mars’ magnetosphere, which are responsible for controlling particle energisation, plasma loss, its transport, and other processes through wave-particle interactions.
India’s Ministry of Science and Technology, which reported the finding earlier this month, said the study is crucial for researchers to get new insights into the behaviour of the Martian magnetosphere and could help in the understanding of such phenomena in other planetary magnetic fields.
The Earth is a giant magnet, and its magnetic field generated by the motion of molten iron in its core protects us from high-speed charged particles that are continuously emitted from the Sun in the form of solar wind. Unlike Earth, the planet Mars does not have any intrinsic magnetic field, which allows the high-speed solar wind to interact directly with the Mars atmosphere, like an obstacle in flow.
If the Earth lacked a magnetic field, the solar wind would have penetrated all the way to the top of the atmosphere and would then have flowed around the Earth, the way water flows around a rock in a stream. Something like that in fact happens, for instance, at the planet Venus, which seems to have no magnetic field of its own. At Earth, however, a strong magnetic field confronts the solar wind, forming a much bigger obstacle than the Earth itself. Because the solar wind is a plasma, it is forced to detour around the Earth’s field, creating a large, shielded cavity around the Earth–the magnetosphere.
Scientists are of the opinion that even in a weak and thin magnetosphere like that of Mars, one can observe frequent occurrences of solitary waves. However, despite several missions to Mars, the presence of solitary waves in the Martian magnetosphere was never detected earlier.
Now for the first time, a research team from the Indian Institute of Geomagnetism (IIG), an autonomous institute of the Department of Science and Technology, has identified and reported the solitary waves in the Martian magnetosphere with the help of high-resolution electric field data recorded by the Langmuir Probe and Waves instrument on the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft of NASA.
The magnetosphere is weak but highly dynamic and formed due to the direct interaction of solar winds with the Martian atmosphere. There is a suggestion from the study that there is an active process taking place in the planet’s magnetic environment.
The study revealed the solitary waves to be distinct electric field fluctuations, which lasted for about 0.2-1.7 milliseconds and were predominant during dawn or between afternoon to dusk at an altitude of 1,000-3,500 km from Mars’ surface. The researchers also found that the spatial extent of these structures is very small — 30 to 330 metres.
The Science and Technology Ministry said further investigation is needed to determine exactly why these waves are dominant during a fixed time of the day.
As these solitary waves are known to be responsible for plasma energisation and its transport in the Earth’s magnetosphere, the research team is further exploring their role in the particle dynamics in the Martian magnetosphere and to understand whether such waves play any role in the loss of atmospheric ions on Mars.
The MAVEN spacecraft found solar radiation striking Mars’ unprotected atmosphere directly, knocking atoms off into space. When solar wind hits the weak Martian magnetosphere, it imparts energy to atmospheric atoms and molecules, giving them enough velocity to escape the planet’s gravity.
