Chandrayaan instrument gives outstanding science results on solar corona, heliophysics

An instrument on board India’s Chandrayaan-2 mission has offered outstanding science results on the solar corona and heliophysics, the Indian Space Research Organisation (ISRO) mentioned.

Though we now have a reasonably good understanding of the origin of vitality and different numerous facets of the Sun, a number of probably life-changing phenomena nonetheless stay a thriller, notes the Bengaluru-headquartered area company.

Some of those mysteries are associated to the new outer environment of the Sun, generally known as corona, which emits profusely in ultra-violet and X-ray wavelengths of the electromagnetic spectrum.

It is thought that the corona consists of ionised fuel at temperatures exceeding a million Kelvin, which is way increased than photospheric temperature of 6000K, the seen floor temperature of the Sun.

However, this statement is in opposition to the pure expectation that the temperatures ought to cut back as we go away from the supply of vitality, and this is called the ‘coronal heating problem.’ From observations, such because the presence of even hotter corona, known as lively areas above the Sunspots (darkish patches seen in seen photos of the Sun) the place the magnetic fields are recognized to be stronger, it’s urged that the magnetic fields have an essential function within the coronal heating, based on the ISRO.

While there are totally different theories concerning the precise mechanism, one in every of these depends on the prevalence of numerous small solar flares known as nanoflares.

Another puzzling statement concerning the corona is that sure components are discovered to have abundances three to 4 occasions increased in lively areas than within the photosphere.

This occurs for components that are simpler to ionise, or require lesser vitality to ionise. In extra technical phrases, these components have their First Ionisation Potential (FIP) decrease than 10 eV, and therefore this phenomenon is mostly termed as FIP bias.

The precise motive behind the FIP bias and its origin stays an open query. A workforce of scientists from Ahmedabad-based Physical Research Laboratory (PRL), a unit of Department of Space, used observations of the Sun in smooth X-rays with Solar X-ray Monitor (XSM) on board ISRO’s Chandrayaan-2 mission in the course of the deepest solar minimal of the previous hundred years to be taught thrilling particulars concerning the solar corona, an replace on the ISRO web site mentioned.

“For the first time, absolute abundances of elemental Mg, Al, Si in the quiet solar corona are derived. The team discovered and characterised around 100 sub-A class microflares in the quiet corona providing new insight into coronal heating puzzle”, it mentioned.

The XSM, designed and developed by PRL with help from numerous ISRO centres, offers measurement of soppy X-ray (1- 15 keV) spectrum of the Sun.

The XSM additionally helps the quantitative measurements of elemental abundances of the lunar floor utilizing the companion payload CLASS (Chandrayaan-2 Large Area Soft X-ray Spectrometer) developed by URSC (U R Rao Satellite Centre), an ISRO centre, which measures the X-ray fluorescence spectrum from the lunar floor.

At current, XSM is the one instrument that gives smooth X-ray spectral measurements of the Sun, i.e., measures the depth of X-ray in numerous energies over the 1 to fifteen keV.

More importantly, XSM offers such measurements with excellent vitality decision at each second, the very best cadence for any instrument to date, the ISRO replace mentioned.

XSM began observations of the Sun in September 2019, in the course of the interval of solar minimal when sometimes there have been only a few Sunspots and lively areas on the Sun.

The solar minimal of 2019-2020 was much more peculiar because the Sun was extraordinarily quiet, and its exercise was on the lowest degree over the previous century, the area company mentioned.

This offered a novel alternative for XSM to watch the quiet corona with out lively areas for lengthy intervals.

The solar X-ray flux was noticed by the XSM throughout this era when no lively areas had been current on the solar disk.

A outstanding and stunning statement is the detection of a big quantity (98) of extraordinarily small flares within the quiet corona.

These flares are so small that their depth is effectively under the usual scale to categorise solar flares (i.e. A, B, C, M, and X class flares, the place every class is 10 occasions extra intense than earlier), and therefore these are termed as sub-A category microflares.

Using the X-ray spectra of those microflares obtained with the XSM and modern photos in Extreme Ultra-violet obtained with the Atmospheric Imaging Assembly (AIA) of NASA’s Solar Dynamics Observatory (SDO), the vitality content material of those flares may very well be estimated, ISRO mentioned.

“This was the first observation and statistical study of such a large sample of microflares in the quiet Sun, supporting the hypothesis of the presence of even smaller scale flares everywhere on the solar corona that could be responsible for the coronal heating,” the replace mentioned.

The X-ray emission over these 76 days, excluding the durations of the microflares, is unusually fixed.

This is the bottom depth of X-ray emission noticed from the Sun since space-borne observations started, the ISRO mentioned.

Analysis of the XSM spectra of the quiet Sun, excluding the microflares, offered the measurement of abundances of varied components.

The abundances of the low FIP components Mg, Al, and Si had been estimated and located to be decrease than the abundances seen in lively area corona however increased than that within the photosphere.

“This is the first report of measurement of abundances as well as reduced FIP bias in the quiet Sun.

Our observations of FIP bias in the quiet Sun provides significant inputs towards understanding the FIP bias and suggests that it arises due to the presence of Alfvn waves in the closed magnetic loops”, the ISRO mentioned.

These outstanding science results on the solar corona and heliophysics obtained throughout a novel solar extraordinarily quiet interval utilizing a delicate instrument XSM aboard Chandryayaan-2 observations are revealed in two companion papers within the May challenge of the’Astrophysical Journal Letters’.

“Both the Chandrayaan-2 orbiter and the XSM instrument are performing extremely well, and expected to provide many more exciting and new results”, the replace added.