The Sun's activity waxes and wanes periodically and holds sway over our space environment. Sunspots, strongly magnetized blotches on the solar surface, sometimes release fierce storms in space that severely impact our satellite based communication and navigational systems and occasionally, render satellites useless.

However, a complete understanding of all aspects of the sunspot activity cycle remains elusive. One of its curious features is the long observed lopsided activity of its two hemispheres. Sometimes, the northern hemisphere becomes more active, sometime the south, with no apparent way to predict when this might happen.

Now, a team of scientists from the Center of Excellence in Space Sciences India at IISER Kolkata and the Tata Institute of Fundamental Research in Mumbai have uncovered a hitherto unknown link between plasma jets in the Sun's interior and the sunspot cycle which may foretell the unequal activity of the Sun's hemispheres.

Plasma material at different locations inside the Sun rotates at different rates powering a dynamo mechanism that creates the magnetic sunspots. The rate of rotation has been earlier observed to change with time with faster and slower streams of plasma jets known as torsional oscillations superposed on the average rotation.

These jets accompany the progress of the sunspot cycle with their patterns of migration similar to those of sunspots on the Sun's surface hinting at a causal link. In a paper in the Astrophysical Journal of the American Astronomical Society, Lekshmi B., Dibyendu Nandi and H. M. Antia report that asymmetries in plasma jets just below the Sun's surface precede asymmetries in sunspot activity by about a year, a discovery with no clear theoretical explanation yet.

"The strength of the Sun's torsional oscillation is very small compared to the differential rotation thus making it difficult to measure. Our careful analysis covering 16 years of both ground- and space-based observations has allowed us to discover this link," said graduate student Lekshmi B.

The team used a technique called helioseismology which observes oscillations on the Sun's surface that are produced by the propagation of acoustic waves in its interior. Through use of helioseismic techniques, plasma velocity changes in the Sun's two hemispheres are then teased out.

"Our study probes only the near-surface bands of faster and slower rotation. However, the current consensus is that magnetic fields that form sunspots are created deeper inside the Sun. It is extremely intriguing, therefore, that the sunspot cycle asymmetry is mirrored across the vast depth of the Sun's convection zone linking the deep and the near-surface layers of the Sun" said Dibyendu Nandi who supervised the research in collaboration with H. M. Antia.

"This may be an early manifestation of the creation of magnetic fields deep within the Sun and may lead to techniques for predicting its hemispheric activity levels," he adds.

Research Report: "Asymmetry in Torsional Oscillation and the Sunspot Cycle," Lekshmi, B., Nandy, D., and Antia, H. M, 2018 July 12, Astrophysical Journal, 2018 July 12

Related Links
Center Of Excellence In Space Sciences India
Solar Science News at SpaceDaily

Tweet

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

Cutting-Edge Heat Shield Installed on NASA's Parker Solar Probe
Laurel MD (SPX) Jul 06, 2018
The launch of Parker Solar Probe, the mission that will get closer to the Sun than any human-made object has ever gone, is quickly approaching, and on June 27, 2018, Parker Solar Probe's heat shield - called the Thermal Protection System, or TPS - was installed on the spacecraft. A mission 60 years in the making, Parker Solar Probe will make a historic journey to the Sun's corona, a region of the solar atmosphere. With the help of its revolutionary heat shield, now permanently attached to the spac ... read more