Universität zu Köln

Chiba, Shota, Imamura, Takeshi, Tokumaru, Munetoshi ORCID: 0000-0002-2982-1887, Shiota, Daikou, Matsumoto, Takuma ORCID: 0000-0002-1043-9944, Ando, Hiroki, Takeuchi, Hiroshi ORCID: 0000-0001-5863-4653, Murata, Yasuhiro, Yamazaki, Atsushi, Hausler, Bernd and Paetzold, Martin (2022). Observation of the Solar Corona Using Radio Scintillation with the Akatsuki Spacecraft: Difference Between Fast and Slow Wind. Sol. Phys., 297 (3). DORDRECHT: SPRINGER. ISSN 1573-093X

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Abstract

The properties of the coronal plasma at heliocentric distances of 1.5 - 8.9 R-circle dot (solar radii) were studied with radio-occultation observations using JAXA's Akatsuki spacecraft in 2016. Physical parameters that characterize the solar wind were retrieved from the intensity-scintillation time series by fitting a theoretical spectrum to the observed power spectra. The derived solar-wind velocity clearly shows a difference between the fast wind and the slow wind, which was identified based on IPS observations. The inner scale, at which fluid motions dissipate and kinetic energy is converted to heat, increases with the heliocentric distance, and the fast wind has larger inner scales than the slow wind. By applying wavelet analysis to the frequency time series, we detected quasi-periodic fluctuations in the electron density. The density oscillations are considered to be manifestations of acoustic waves, which were generated from Alfven waves originating from the photosphere, and the energy fluxes of those acoustic waves were estimated. The relative density-amplitude peaks around 4 - 6 R-circle dot and the wave-energy flux decreases beyond approximate to 6 R-circle dot, implying that the acoustic waves dissipate to heat the corona. The phase-scintillation spectrum that we obtained cannot be expressed by a single power law. A break is seen around the frequency of 0.5 - 2 Hz beyond approximate to 6 R-circle dot, suggesting an excess power other than turbulence at lower frequencies. The enhancement of the relative density amplitude around 6 R-circle dot found by the wavelet analysis might explain this excess power. The acoustic wave-energy flux in the fast solar wind tends to exceed that in the slow wind, suggesting that the fast wind is powered by a larger injection of Alfven-wave energy than the slow wind.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Chiba, Shota UNSPECIFIED UNSPECIFIED UNSPECIFIED Imamura, Takeshi UNSPECIFIED UNSPECIFIED UNSPECIFIED Tokumaru, Munetoshi UNSPECIFIED orcid.org/0000-0002-2982-1887 UNSPECIFIED Shiota, Daikou UNSPECIFIED UNSPECIFIED UNSPECIFIED Matsumoto, Takuma UNSPECIFIED orcid.org/0000-0002-1043-9944 UNSPECIFIED Ando, Hiroki UNSPECIFIED UNSPECIFIED UNSPECIFIED Takeuchi, Hiroshi UNSPECIFIED orcid.org/0000-0001-5863-4653 UNSPECIFIED Murata, Yasuhiro UNSPECIFIED UNSPECIFIED UNSPECIFIED Yamazaki, Atsushi UNSPECIFIED UNSPECIFIED UNSPECIFIED Hausler, Bernd UNSPECIFIED UNSPECIFIED UNSPECIFIED Paetzold, Martin UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-690944
DOI:	10.1007/s11207-022-01968-9
Journal or Publication Title:	Sol. Phys.
Volume:	297
Number:	3
Date:	2022
Publisher:	SPRINGER
Place of Publication:	DORDRECHT
ISSN:	1573-093X
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language ELECTRON-DENSITY FLUCTUATIONS; POWER SPECTRUM; SOUNDING EXPERIMENTS; MAGNETIC-FIELD; MASS EJECTIONS; MARS-EXPRESS; 30 R; ACCELERATION; SCALE; WAVES Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/69094