Delhi : Our galaxy could be easily misunderstood as there are mysteries which hasn’t been resolved even until today. Diving deeper into these mysteries not only reveals the existence of our planet but also allows us to learn about other distant stars better.
With the driving curiosity to know more and beyond, a team of scientists used Mangalyaan to study the Solar Corona when the Earth and Mars were on opposite sides of the Sun. The scientists from the Space Physics Laboratory of Vikram Sarabhai Space Centre, Trivandrum; Physics Research Laboratory, Ahmedabad and ISRO SRO Telemetry Tracking and Command Network (ISTRAC), Bangalore, used the solar conjunction to look into the atmosphere of the Sun. It is a complex mystery, and hence to solve that Indian scientists used S-band radio signals coming from Mangalyaan to study the Solar Corona.
The conjunction event has been taken from the year 2015; a time when the Sun’s activity was quite low, to study the turbulence in the solar corona.
What is Solar Corona & Coronal Heating?
The mysterious outer region of the Sun consists of hot and highly diffuse plasma, ionized gas at temperatures that exceed one million Kelvin, much higher than the photospheric temperature of 6,000 Kelvin, the visible surface temperature of the Sun.The most mysterious and crucial puzzle related to the sun is its temperature. The ionized gas temperature at the core of the Sun reaches up to 15 million degrees Celsius, which drops to mere 5,700 degrees at the solar surface (photosphere). But the temperature starts to increase again above the photosphere with a height reaching one million degrees or more in the corona. The increase or rise of temperature in Corona despite moving away from the source of energy is against the natural expectation that the temperature should reduce. Scientists have termed this phenomenon as a ‘Coronal Heating Problem’.Also, the Sun is a magnetized star and the active regions above the Sunspots have stronger magnetic fields. It is suggested that the magnetic fields play a crucial role in coronal heating. There are different theories governing this mechanism but one of the theories relies on the occurrence of a large number of small solar flares which are known as ‘nanoflares’. Another observation about the corona suggests that certain elements are found to have abundances three to four times higher in active regions than in the photosphere. This happens for elements that are easier to ionize.
The Intriguing Observations:
The study that has been published in the Journal Monthly Notices of the Royal Astronomical Society makes intriguing observations. The Indian Space Agency said that the radio signals from MOM (Mars Orbit Mission) spacecraft crossing through the solar corona during the conjunction event experienced the dispersive effects. These effects in the corona produce fluctuations in plasma density which are registered as fluctuations in the phase of radio waves passing through it. Studying the turbulence reflects the region where the solar wind primarily gets accelerated to velocities of a few hundreds of kilometres per second.Apart from this, another intriguing observation recorded by the scientists is when they compared the studies by MOM spacecraft with similar experiments conducted by the earlier missions which spanned past solar cycles. The work based on MOM data reports an insight into the feeble maxima of solar cycle 24, which is recorded as a peculiar solar cycle in terms of overall lower activity than any other previous solar cycle.