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Mystery of Flickering Aurora:
Elucidate the Structure of Pulsating Aurora by "REIMEI" Observations with Computer Simulation

September 28, 2015 (JST)

National Research and Development Agency
Japan Aerospace Exploration Agency (JAXA)
National University Corporation
Nagoya University
National Institute of Polar Research

The research groups of the Japan Aerospace Exploration Agency (JAXA), Nagoya University and other related agencies clarified the structure of flickering aurora by analyzing the observation data of the JAXA satellite, INnovative-technology Demonstration Experiment “REIMEI” (INDEX), combined with computer simulations conducted by Nagoya University. The research shows that a space electromagnetic wave called “Chorus” modulates electrons to create pulsating movement of the aurora.

The aurora is a phenomenon generated by a collision of electrons falling from space and the upper atmosphere at around 100 km in altitude. The aurora that is blinking every few seconds is called “pulsating aurora”. It has a mysterious character of flickering a few times in a second. What causes this flickering has been unknown.
The research this time clarifies the structure of the aurora flickering by modulating electrons that cause the aurora using space electromagnetic waves. The wave called “Chorus” sounds like birds’ warbling when the electromagnetic wave is converted to sound. The research this time elucidated that this chorus causes blinking and flickering of pulsating aurora by the same mechanism. In addition, JAXA’s “ERG” project (Exploration of energization and Radiation in Geospace) scheduled to be launched in Japan Fiscal Year 2016 will further clarify more detailed characters for the modulating process of electrons by electric waves as indicated in this research.
The achievement this time was published by the American Geophysical Union issued on September 29.

INnovative-technology Demonstration Experiment “REIMEI” (INDEX)

The REIMEI was launched on August 24, 2005 as a piggyback satellite on the Dnepr Rocket from Baikonur Cosmodrome in the Republic of Kazakhstan. The purpose of this satellite is to gain global leading scientific attainments by conducting on-orbit demonstration of cutting-edge satellite technology and also being equipped with suitable scientific observation instruments for a small satellite. Those instruments can perform electron observations using global leading temporal resolution* and simultaneous observations of aurora and electrons that light the aurora. The REIMEI is the only satellite to conduct such simultaneous observations in the world.

The minimum time variation for an observation target to change that can be distinguishable. As the time variation is smaller, the temporal resolution is higher. When the temporal resolution is high, high-speed change in observation images can be distinguishable.