Details

Autor(en) / Beteiligte

• Wu, Honghong
• Huang, Shiyong
• He, Jiansen
• Yang, Liping
• Yuan, Zhigang

Titel

Radial Spectral Evolution of the Elsässer Variable z− in the Slow Solar Wind

Ist Teil von

• The Astrophysical journal, 2024-05, Vol.966 (1), p.144

Ort / Verlag

Philadelphia: IOP Publishing

Erscheinungsjahr

2024

Link zum Volltext

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• The nature of the Elsässer variable z− plays a significant role in the understanding of solar wind turbulence. The radial spectral evolution of z− observed by the Helios spacecraft suggests that z− has a persistent background spectrum in the low-frequency range from 0.3 to 1 au. However, the radial evolution in the near-Sun solar wind remains unknown. Here we use Parker Solar Probe measurements to analyze the averaged spectra of z− in the slow solar wind from 0.1 to 0.5 au and compare the results with the WIND observations at 1 au. We find that the averaged spectra of z− do not show the low-frequency break at the low-frequency breakpoint on the power spectra of z+, magnetic field, and velocity. The energy in the frequency range of 10−4–10−2 Hz demonstrates a radial decay from 0.1 to 0.5 au and keeps nearly constant to 1 au. The spectral index of z− gradually decreases from −1.27 at 0.1–0.2 au to −1.59 at 0.4–0.5 au and then slowly declines to −1.70 at 1 au. The radial behaviors of the ∥, ⊥1, and ⊥2 components of z− in the field-aligned coordinates are similar to that of the trace of z−. Our findings suggest a faster radial spectral evolution of z− in the near-Sun solar wind and provide strong observational constraints for the solar wind turbulence model.