太陽黒点上空でオーロラに似た電波バーストを発見(NASA-Supported Team Discovers Aurora-Like Radio Bursts Above Sunspot)

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2024-03-13 NASA

NASAの科学者チームが、太陽からの長期間続く電波を発見しました。これらの信号は、地球のオーロラに関連するものと似ています。これらのラジオバーストは、太陽の黒点の上空、約25,000マイル(40,000 km)で検出され、以前は惑星や他の星でしか観測されていませんでした。この発見は、私たちの太陽だけでなく、同様のラジオ信号を発する遠い星の振る舞いを理解するのに役立つかもしれません。

<関連情報>

黒点上空で長時間持続するオーロラ様電波放射の検出 Detection of long-lasting aurora-like radio emission above a sunspot

Sijie Yu,Bin Chen,Rohit Sharma,Timothy S. Bastian,Surajit Mondal,Dale E. Gary,Yingjie Luo &Marina Battaglia
Nature Astronomy  Published:13 November 2023
DOI:https://doi.org/10.1038/s41550-023-02122-6

extended data figure 1

Abstract

Auroral radio emissions in planetary magnetospheres typically feature highly polarized, intense radio bursts, usually attributed to electron cyclotron maser emission from energetic electrons in the planetary polar region that features a converging magnetic field. Similar bursts have been observed in magnetically active low-mass stars and brown dwarfs, often prompting analogous interpretations. Here we report observations of long-lasting solar radio bursts with high brightness temperature, wide bandwidth and high circular polarization fraction akin to these auroral and exo-auroral radio emissions, albeit two to three orders of magnitude weaker than those on certain low-mass stars. Spatially, spectrally and temporally resolved analysis suggests that the source is located above a sunspot where a strong, converging magnetic field is present. The source morphology and frequency dispersion are consistent with electron cyclotron maser emission due to precipitating energetic electrons produced by recurring nearby flares. Our findings offer new insights into the origin of such intense solar radio bursts and may provide an alternative explanation for aurora-like radio emissions on other flare stars with large starspots.

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