Solar storms trigger Jupiter's 'Northern Lights'

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WASHINGTON, DC -- Solar storms trigger Jupiter's intense 'Northern Lights' by generating a new X-ray aurora that is eight times brighter than normal and hundreds of times more energetic than Earth's aurora borealis, new research finds.

It is the first time that Jupiter's X-ray aurora has been studied when a giant storm from the sun has arrived at the planet. The dramatic findings complement NASA's Juno mission this summer, which aims to understand the relationship between the two biggest structures in the solar system - the region of space controlled by Jupiter's magnetic field (its magnetosphere) and that controlled by the solar wind.

"There's a constant power struggle between the solar wind and Jupiter's magnetosphere," said William Dunn, a PhD candidate at University College London Mullard Space Science Laboratory and lead author of the new study.

"We want to understand this interaction and what effect it has on the planet," Dunn said. "By studying how the aurora changes, we can discover more about the region of space controlled by Jupiter's magnetic field, and if or how this is influenced by the Sun. Understanding this relationship is important for the countless magnetic objects across the galaxy, including exoplanets, brown dwarfs and neutron stars."

The Sun constantly ejects streams of particles into space in the solar wind. When giant storms erupt, the winds become much stronger and compress Jupiter's magnetosphere, shifting its boundary with the solar wind two million kilometers (1.25 million miles) through space. The new study found that this interaction at the boundary triggers the high energy X-rays in Jupiter's Northern Lights, which cover an area bigger than the surface of the Earth.

The study, published yesterday in the Journal of Geophysical Research - Space Physics, a journal of the American Geophysical Union, comes as NASA's Juno spacecraft nears Jupiter for the start of its mission this summer. Launched in 2011, Juno aims to unlock the secrets of Jupiter's origin, helping us to understand how the solar system, including Earth, formed.

As part of the mission, Juno will investigate Jupiter's relationship with the Sun and the solar wind by studying its magnetic field, magnetosphere and aurora. The research team hopes to find out how the X-rays form by collecting complementary data using the European Space Agency's X-ray space observatory, XMM-Newton, and NASA's Chandra X-ray observatory.

"Comparing new findings from Jupiter with what is already known for Earth will help explain how space weather is driven by the solar wind interacting with Earth's magnetosphere," said Graziella Branduardi-Raymont, an astrophysicist at UCL Mullard Space Science Laboratory and a co-author of the study. "New insights into how Jupiter's atmosphere is influenced by the Sun will help us characterize the atmospheres of exoplanets, giving us clues about whether a planet is likely to support life as we know it."

The researchers tracked the impact of solar storms on Jupiter's aurora by monitoring the X-rays emitted during two 11-hour observations in October 2011 when an interplanetary coronal mass ejection was predicted to reach the planet from the Sun. The scientists used the data collected to build a 3D spherical image to pinpoint the source of the X-ray activity and identify areas to investigate further at different time points.

"In 2000, one of the most surprising findings was a bright 'hot spot' of X-rays in the aurora which rotated with the planet," Dunn said. "It pulsed with bursts of X-rays every 45 minutes, like a planetary lighthouse. When the solar storm arrived in 2011, we saw that the hot spot pulsed more rapidly, brightening every 26 minutes. We're not sure what causes this increase in speed but, because it quickens during the storm, we think the pulsations are also connected to the solar wind, as well as the bright new aurora."

A second study published yesterday in the Journal of Geophysical Research - Space Physics reports that the X-ray aurora responds to quieter 'gusts' of solar wind, deepening this connection between Jupiter and the solar wind.

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Notes for Journalists

These research articles will be open access for 60 days from the date of publication. PDF copies of the articles can be downloaded at the following links:

Dunn et al: http://onlinelibrary.wiley.com/doi/10.1002/2015JA021888/pdf

Kimura et al: http://onlinelibrary.wiley.com/doi/10.1002/2015JA021893/pdf

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Title: "The impact of an ICME on the Jovian X-ray aurora"

Authors: William R. Dunn, Andrew J. Coates: Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, United Kingdom, and the Centre for Planetary Science at UCL/Birkbeck, London, United Kingdom;

Graziella Branduardi-Raymont, I. Jonathan Rae, Ali Varsani: Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, United Kingdom;

Ronald F. Elsner: NASA Marshall Space Flight Center, Huntsville, Alabama, U.S.A.;

Marissa F. Vogt: Center for Space Physics, Boston University, Boston, Massachusetts, U.S.A.;

Laurent Lamy: LESIA, The Paris Observatory, National Center for Scientific Research, Pierre and Marie Curie University, Paris Diderot University, Meudon, France;

Peter G. Ford: Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, U.S.A.;

G. Randall Gladstone: Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, U.S.A.;

Caitriona M. Jackman: Department of Physics and Astronomy, University of Southampton, Southampton, United Kingdom;

Jonathan D. Nichols: Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom;

Tomoki Kimura: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan, and Nishina Center for Accelerator-Based Science, RIKEN, Saitama, Japan;

Kenneth C. Hansen: Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, U.S.A.;

Jamie M. Jasinski: Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, London, United Kingdom; the Centre for Planetary Science at UCL/Birkbeck, London, United Kingdom; and Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, U.S.A.

Contact Information for the Authors:

William Dunn: w.dunn@ucl.ac.uk

Title:"Jupiter's X-ray and EUV auroras monitored by Chandra, XMM-Newton, and Hisaki satellite"

Authors:Tomoki Kimura: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan; Nishina Center for Accelerator-Based Science, RIKEN, Saitama, Japan; and Harvard-Smithsonian Center for Astrophysics, Smithsonian Astrophysical Observatory, Cambridge, Massachusetts, U.S.A.;

R. P. Kraft, S. S. Murray: Harvard-Smithsonian Center for Astrophysics, Smithsonian Astrophysical Observatory, Cambridge, Massachusetts, U.S.A.;

Ronald F. Elsner: NASA Marshall Space Flight Center, Huntsville, Alabama, U.S.A.;

William. R. Dunn, Graziella Branduardi-Raymont: Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, United Kingdom;

R. Gladstone: Department of Space Studies, Southwest Research Institute, Boulder, Colorado, U.S.A.;

C. Tao: Institute for Research in Astrophysics and Planetology, University of Toulouse, National Center for Scientific Research, Toulouse, France;

K. Yoshioka, G. Murakami, A. Yamazaki, H. Hasegawa: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan;

F. Tsuchiya: Planetary Plasma and Atmospheric Research Center, Tohoku University, Sendai, Japan;

Marissa F. Vogt: Center for Space Physics, Boston University, Boston, Massachusetts, U.S.A.;

A. Masters: Department of Physics, Faculty of Natural Sciences, Imperial Collage London, London, United Kingdom;

S. V. Badman: Department of Physics, Lancaster University, Lancaster, United Kingdom;

E. Roediger: Hamburg Observatory, University of Hamburg, Hamburg, Germany;

Y. Ezoe: Tokyo Metropolitan University, Tokyo, Japan;

I. Yoshikawa: Department of Complexity Science and Engineering, University of Tokyo, Chiba, Japan;

M. Fujimoto: Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan, and Earth-Life science Institute, Tokyo Institute of Technology, Tokyo, Japan.

Contact Information for the Authors:Tomoki Kimura: tomoki.kimura@riken.jp

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