Io and the Radio Emissions of its Host Planet

When Galileo Galilei looked at Jupiter through his telescope centuries ago, he was able to see four of the many satellites orbiting the gas giant. They are now known as the Galilean moons. One of them, Io, is the most volcanically active place in the solar system. Its atmosphere is mostly made of sulfur dioxide, which is always escaping from Io’s volcanoes. It also forms a magnetosphere around Io, known as the Io plasma torus.
The inside of Jupiter’s magnetosphere contains particles from Io. As part of the interactions between the magnetospheres of these two worlds, neutrally charged sodium forms a ‘nebula’ known as Jupiter’s sodium nebula. It is known that Jupiter’s magnetosphere is affected by the solar wind, a stream of charged particles from the sun. We also know that  one of Jupiter’s naturally occurring radio emissions,  the HOM, is connected to its aurora–yes, Jupiter has aurora, and gives off radio emissions. These are affected by the solar wind. The magnetosphere is also affected by the amount of sodium from Io that enters the sodium nebula–so, does Io’s volcanic activity have any effect on Jupiter?
Volcanic eruptions are visible on Io in this image, taken by the Galileo spacecraft. Image credit Galileo Project/JPL/NASA. May 22, 2011 Astronomy Picture of the Day.
Volcanic eruptions are visible on Io in this image, taken by the Galileo spacecraft. Image credit Galileo Project/JPL/NASA. May 22, 2011 Astronomy Picture of the Day.
Today’s article, “Io’s volcanism controls Jupiter’s radio emissions” by M. Yoneda, F. Tsuchiya, H. Misawa, B. Bonfond, C. Tao, M. Kagitani, and S. Okano, was published in Geophysical Research Letters in 2013. They used a telescope on Mt. Haleakala, on Maui, Hawaii, to try to answer this question. Their observations went from May 19th to June 21st, 2007, using a telescope with a specialized filter. This filter allowed them to see the emission spectrum of Jupiter’s sodium nebula. When passed through a device known as a spectrometer, light splits into many lines at various wavelengths of light; the pattern of these lines are unique to each element. By looking at the brightness of one of these lines, an indication of the density of plasma in the nebula could be determined. The authors also used the WIND (Comprehensive Solar Wind Laboratory for Long-Term Solar Wind Measurements) spacecraft to detect the HOM.
It appears from other works that the greater the density of plasma, the more intense the HOM. However, the effect of the plasma density on the magnetosphere is not known. It appears that the more plasma, the more Jupiter’s aurora move towards the equator. In this work, the HOM decreased, but it was unclear if the aurora did as well.
During the study, an increase in HOM was detected, and it was not from the solar wind. However, the sun also gives out radio signals. Due to these signals during the study, the HOM signals could not be determined. Therefore, the authors could not correlate a relationship between HOM signals and Io’s volcanoes, if one exist. More studies, perhaps searching for a link between Io’s volcanic activity and the solar nebula, and Jupiter’s aurora, could be performed. Science is not perfect, and sometimes other things get in the way–like solar radio signals. It is often frustrating when things to do not work out, but such is the way of science.

 

 

Bibliography
Astronomy Picture of the Day. “APOD: 2011 May 22 – Io: The Prometheus Plume.” N.p., n.d. Web.
The Astronomy Picture of the Day used for the image that appears in this post.
National Aeronautics and Space Administration. “Io.” N.p., n.d. Web.
NASA’s page dedicated to Io.
National Aeronautics and Space Administration. “WIND Spacecraft.” N.p., n.d. Web.
NASA’s webpage about it’s WIND spacecraft, which is now over twenty years old.
Serway, Raymond A., and John W. Jewett. Principles of Physics: A Calculus-Based Text. 4th ed. Victoria, Australia ; Belmont, CA: Thomson/Brooks/Cole, 2006. Print.
My introductory physics textbook, used for reference on emission spectra.
Yoneda, Mizuki, et al. “Io’s volcanism controls Jupiter’s radio emissions.”Geophysical Research Letters 40.4 (2013): 671-675.
Today’s main paper.
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