The result, which appears in the journal the Proceedings of the National Academy of Sciences, upends our understanding of how heat is transported outwards by the Sun and challenges existing explanations of the formation of sunspots and magnetic field generation.
The work was conducted by researchers from NYU’s Courant Institute of Mathematical Sciences and its Department of Physics, Princeton University, the Max Planck Institute, and NASA.
The Sun’s heat, generated by nuclear fusion in its core, is transported to the surface by convection in the outer third. However, our understanding of this process is largely theoretical—the Sun is opaque, so convection cannot be directly observed. As a result, theories largely rest on what we know about fluid flow and then applying them to the Sun, which is primarily composed of hydrogen, helium, and plasma.
Developing a more precise grasp of convection is vital to comprehending a range of phenomena, including the formation of sunspots, which have a lower temperature than the rest of the Sun’s surface, and the Sun’s magnetic field, which is created by its interior plasma motions.
In order to develop their “MRI” of the Sun’s plasma flows, the researchers examined high-resolution images of the Sun’s surface taken by the Helioseismic and Magnetic Imager (HMI) onboard NASA’s Solar Dynamics Observatory. Using a 16-million pixel camera, HMI measures motions on the Sun’s surface caused by convection.
Once the scientists captured the precise movement waves on the Sun’s surface, they were able to calculate its unseen plasma motions. This procedure is not unlike measuring the strength and direction of an ocean’s current by monitoring the time it takes a swimmer to move across the water—currents moving against the swimmer will result in slower times while those going in the same direction will produce faster times, with stronger and weaker currents enhancing or diminishing the impact on the swimmer.
What they found significantly departed from existing theory--specifically, the speed of the Sun’s plasma motions were approximately 100 times slower than scientists had previously projected.
“Our current theoretical understanding of magnetic field generation in the Sun relies on these motions being of a certain magnitude,” explained Shravan Hanasoge, an associate research scholar in geosciences at Princeton University and a visiting scholar at NYU’s Courant Institute of Mathematical Sciences. “These convective motions are currently believed to prop up large-scale circulations in the outer third of the Sun that generate magnetic fields.”
“However, our results suggest that convective motions in the Sun are nearly 100 times smaller than these current theoretical expectations,” continued Hanasoge, also a postdoctoral fellow at the Max Plank Institute in Katlenburg-Lindau, Germany. “If these motions are indeed that slow in the Sun, then the most widely accepted theory concerning the generation of solar magnetic field is broken, leaving us with no compelling theory to explain its generation of magnetic fields and the need to overhaul our understanding of the physics of the Sun’s interior.”
The study’s other co-authors were Thomas Duvall, an astrophysicist at NASA, and Katepalli Sreenivasan, University Professor in NYU’s Department of Physics and Courant Institute. Sreenivasan is also Senior Vice Provost for Science and Technology for the Global Network University at NYU and Provost of Polytechnic Institute of NYU.
James Devitt | Newswise Science News
Four elements make 2-D optical platform
26.09.2017 | Rice University
The material that obscures supermassive black holes
26.09.2017 | Instituto de Astrofísica de Canarias (IAC)
Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.
Graphene is up to the job
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
26.09.2017 | Life Sciences
26.09.2017 | Physics and Astronomy
26.09.2017 | Information Technology