From astrobites: “The Deepest Rumblings of the Sun”

Astrobites bloc

astrobites

Feb 7, 2018
Avery Schiff

Title: Asymptotic g modes: Evidence for a rapid rotation of the solar core
Authors: Eric Fossat, Patrick Boumier, Thierry Corbard, et al.
First Author’s Institution: Université Côte d’Azur, Observatoire Côte d’Azur, France
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Status: Published in Astronomy and Astrophysics, open access

Far below its surface, the Sun slowly breaths with invisible pulses. Blobs of plasma are launched upwards by buoyant forces, only to reach the peak of their trajectories and plunge back to the depths below. This motion is known as a g-mode oscillation, and until recently it was unseen by solar scientists. In today’s paper, Fossat et al. describe one of the most promising detections of the g-modes to date and the implications for the Sun’s deepest layers.

Helioseismology

While the Sun appears constant in brightness to the naked eye, careful telescope observations reveal that it periodically dims and brightens on a miniscule scale. Just as a song is made from many notes, the flickering occurs at countless different frequencies that create the “music” of the Sun. Helioseismology, an observation technique that tracks vibrations deep into the Sun, uses Fourier analysis to determine which frequencies are most important and study three potential sources of brightness fluctuations on the Sun: p-mode, g-mode, and f-mode oscillations. Since the brightness of plasma is strongly related to the density, each mode is associated with material compressing or decompressing in some way. P-mode and f-mode oscillations are frequently observed at the solar surface, but the g-modes lurk far beneath the surface of the Sun. By studying g-modes, we are studying the lowest depths of the Sun far below what is visible to us.

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Figure 1: An illustration of the layers of the sun. While p-mode oscillations are able to travel from the surface all the way to the core, g-modes are unable to escape the radiative zone. Credit: ESA

See the full article here .

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