Century-old data help measure the Sun’s magnetic field

The magnetic flux of the Sun is exclusive therein, in contrast to several different celestial bodies, it reverses its polarity roughly each eleven years. Regular observations of the Sun’s magnetic flux begin in 1967, and, so far, we’ve knowledge for the amount from 1967 virtually to this, spanning the star cycles 20-24. Now, associate degree Indo-Russian collaboration has additional to the current with a plot of the star magnetic flux from 1915 to 1965 (solar cycles 15-19). employing a novel approach, they need mark and calculated the sector mistreatment knowledge from the archives of the Kodaikanal star Observatory of the Indian Institute of uranology.

“For concerning the last fifty years, that is, from around Nineteen Seventies, regular measurements of magnetic flux ar out there from completely different observatories. One vital one is Wilcox star Observatory from the America. Before that mountain peak star Observatory provided some knowledge, though they’re not of prime quality and uniform,” says Dipankar Banerjee, Director of Aryabhata analysis Institute of empiric Sciences, Nainital, associate degreed an author of the paper that has been accepted for publication within the astronomy Journal Letters.

Data from Kodaikanal

The present study makes the vital contribution of building on this mistreatment the Kodaikanal star observatory knowledge, and increasing the magnetic flux calculations for one more fifty years about. “Understanding the magnetic flux evolution within the past improves our understanding of the physics itself. within the work we’ve conjointly talked concerning the temporal order of the polarity reversal, that is additionally important,” adds academician. Banerjee. star variations, each of long scale and short, depend upon the magnetic flux, and these will have an effect on each the climate and house weather. Therefore, understanding the magnetic flux variations will contribute to our understanding of climate and house weather.

The Kodaikanal star Observatory was established in 1899 and observations of the Sun from this observatory run over 100 years, providing what’s among the longest series of star knowledge. a crucial feature of those knowledge is that the multi-wavelength observations. the info comprises full disc spectral pictures of the Sun mistreatment the Ca II K and H-alpha lines. each these lines image the region layer of the Sun referred to as the layer.

Extracting info

From the full-disc pictures of Ca II K options, bright patches higher than magnetic flux regions, referred to as plages ar known. “Underneath these one will realize sunspots, thus plages offer info concerning magnetic flux locations and strength,” says Bidya Binay Karak, a Ramanujan Fellow at the Department of Physics, Indian Institute of Technology (BHU), Varanasi, associate degreed an author of the paper.

On the opposite hand, the H-alpha pictures show filaments, that ar fashioned on magnetic neutral lines. “Their presence conjointly represents the magnetic flux distribution to a lower place. They conjointly enable America to check the evolution of magnetic flux with time,” he explains.


The team 1st mark the Ca IIK pictures of the Kodaikanal knowledge mistreatment magnetic flux measurements that were out there throughout that amount. Using this, they understood the info for the periods once magnetic flux measurements weren’t out there, namely, years 1915-1965. “The H-alpha pictures show the situation of filaments, that ar believed to be fashioned on the magnetic neutral lines, thus these pictures offer info on the magnetic polarity,” says Dr Karak. “Combining the 2 sets, the complete magnetic flux knowledge was reconstructed.”

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