The payload, solar X-ray monitor (XSM), which detected the solar flares, is capable of measuring X-rays emitted by the Sun and its corona, and can also measure the intensity of solar radiation. Its primary objective is to provide X-ray spectrum in the energy range of 1-15 keV, according to Indian Space Research Organisation (Isro).
Chandrayaan-2’s orbiter circling the Moon
Currently, the solar cycle is heading towards minima and the Sun has been extremely quiet for the past few months. Therefore, XSM could observe a series of small flares between September 30 and October 1.
The orbiter also uses X-rays emitted by the Sun in a clever way to study elements on the lunar surface. Solar X-rays excite atoms of constituent elements on the lunar surface. These atoms when de-excited emit characteristic X-rays (a fingerprint of each atom). By detecting the characteristic X-rays, it becomes possible to identify various major elements of the lunar surface. However, to determine their concentration, it is essential to have simultaneous knowledge of the solar X-ray spectrum. The orbiter’s Large Area Soft X-ray Spectrometer (CLASS) and XSM payloads can measure the lunar elemental composition using this technique. While CLASS detects the characteristic lines from the lunar surface, XSM simultaneously measures the solar X-ray spectrum.
The graph showing solar flare measurement taken by the orbiter’s payload solar X-ray monitor (XSM)
What is a solar flare?
Many violent phenomena keep occurring on the surface of the Sun and its atmosphere known as the corona. This solar activity follows an 11-year cycle, which means, it goes through its ‘solar maxima’ and ‘solar minima’ once every 11 years. While the cumulative emission of solar X-rays emitted over a year varies with the solar cycle, these are often punctuated with extremely large X-ray intensity variations over very short periods, few minutes to hours. Such episodes are known as solar flares.