A likely detection of a local interplanetary dust cloud passing near the Earth in the AKARI mid-infrared all-sky map

Abstract

Context. We are creating the AKARI mid-infrared all-sky diffuse maps. Through a foreground removal of the zodiacal emission, we serendipitously detected a bright residual component whose angular size is about 50 x 20 deg. at a wavelength of 9 micron. Aims. We investigate the origin and the physical properties of the residual component. Methods. We measured the surface brightness of the residual component in the AKARI mid-infrared all-sky maps. Results. The residual component was significantly detected only in 2007 January, even though the same region was observed in 2006 July and 2007 July, which shows that it is not due to the Galactic emission. We suggest that this may be a small cloud passing near the Earth. By comparing the observed intensity ratio of I_9um/I_18um with the expected intensity ratio assuming thermal equilibrium of dust grains at 1 AU for various dust compositions and sizes, we find that dust grains in the moving cloud are likely to be much smaller than typical grains that produce the bulk of the zodiacal light. Conclusions. Considering the observed date and position, it is likely that it originates in the solar coronal mass ejection (CME) which took place on 2007 January 25.

arXiv comment5 pages, 4 figures, accepted by Astronomy and Astrophysics

References in corpus (12)

• Interstellar Dust Grains
• The Infrared Astronomical Mission AKARI
• The AKARI/IRC Mid-Infrared All-Sky Survey
• The Infrared Camera (IRC) for AKARI - Design and Imaging Performance
• The Far-Infrared Surveyor (FIS) for AKARI
• Dust detection by the wave instrument on STEREO: nanoparticles picked up by the solar wind?
• An improved model for the infrared emission from the zodiacal dust cloud: cometary, asteroidal and interstellar dust
• The $AKARI$ Far-Infrared All-Sky Survey Maps
• In-orbit focal adjustment of the AKARI telescope with IRC images
• Modeling of the zodiacal emission for the AKARI/IRC mid-infrared all-sky diffuse maps
• On the Effect of the Interplanetary Medium on Nanodust Observations by the Solar Terrestrial Relations Observatory
• Effects of high-energy ionizing particles on the Si:As mid-infrared detector array on board the AKARI satellite