We study properties of nonlinear magnetic fluctuations in the turbulent boundary layer (TBL) over polar cusps during a typical TBL crossing on 19 June 1998. Interball-1 data in the summer TBL are compared with that of Geotail in solar wind (SW) and Polar in the northern TBL. In the TBL two characteristic slopes are seen: =-1 at (0.0040.08) Hz and =-2.2 at (0.082) Hz. We present evidences that random current sheets with features of coherent solitons can result in: (i) slopes of * 1 in the magnetic power spectra; (ii) demagnetization of the SW plasma in diamagnetic bubbles; (iii) nonlinear, presumably, 3-wave phase coupling with cascade features; (iiii) departure from the Gaussian statistics. We discuss the above TBL properties in terms of intermittency and self-organization of nonlinear systems, and compare them with kinetic simulations of reconnected current sheet at the nonlinear state. Virtual satellite data in the model current sheet reproduce valuable cascade-like spectral and bi-spectral properties of the TBL turbulence.
On the properties of turbulent boundary layer over polar cusps
2002
Abstract
We study properties of nonlinear magnetic fluctuations in the turbulent boundary layer (TBL) over polar cusps during a typical TBL crossing on 19 June 1998. Interball-1 data in the summer TBL are compared with that of Geotail in solar wind (SW) and Polar in the northern TBL. In the TBL two characteristic slopes are seen: =-1 at (0.0040.08) Hz and =-2.2 at (0.082) Hz. We present evidences that random current sheets with features of coherent solitons can result in: (i) slopes of * 1 in the magnetic power spectra; (ii) demagnetization of the SW plasma in diamagnetic bubbles; (iii) nonlinear, presumably, 3-wave phase coupling with cascade features; (iiii) departure from the Gaussian statistics. We discuss the above TBL properties in terms of intermittency and self-organization of nonlinear systems, and compare them with kinetic simulations of reconnected current sheet at the nonlinear state. Virtual satellite data in the model current sheet reproduce valuable cascade-like spectral and bi-spectral properties of the TBL turbulence.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
