Japan-US FOXSI experiment & Hinode satellite discover solar nanoflares

Image courtesy of ISAS.

Japan’s Institute of Space and Astronautical Science (ISAS), a research institute under the purview of Japan’s space agency JAXA, has announced that an international research team has discovered hidden solar nanoflares in the sun’s corona, possibly accounting for its unusually high temperature.

This previously-undiscovered finding was made using a combination of data from a sounding rocket known as FOXSI (Focusing Optics X-ray Solar Imager), and JAXA’s Hinode (SOLAR-B), an astronomical satellite launched in 2006 to study the solar corona.

FOXSI, an international collaboration between various US and Japanese space organisations (UMN, UCB, NASA/Marshall, NASA/Goddard, JAXA/ISAS, and the National Astronomical Observatory of Japan), carried US-developed X-ray optics and Japan-developed a semiconductor X-ray imaging detector. The results from this experiment came from FOXSI-2, the team’s second sounding rocket, launched in 2014 with an observation window of 6 minutes. 

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The data from FOXSI has been combined with Hinode’s X-ray telescope (XRT), which is sensitive to soft X-ray emissions. The result strongly suggests the occurrence of nanoflares even in a region without apparent flaring activities, and also demonstrates the X-ray technologies on both FOXSI and Hinode, which are highly sensitive and able to detect small amounts of hot plasma in the solar corona.

Said Dr. Shin-nosuke Ishikawa, head of the international research team, “FOXSI’s data clearly demonstrated that our experiments succeeded in obtaining qualitatively new data”.

He added that more data is necessary, and that the research team is working on new missions, “In order to reveal the mechanism of coronal heating with nanoflares, it is necessary to increase the number of regions to be observed as well as to conduct observations with a longer time span. We are keen to examine if nanoflares are general phenomena.”

Read the scientific paper here.


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