ИСТИНА

Large amplitude Alfven waves contribute significantly to the spectrum of magnetic field fluctuations in the solar wind. These waves are believed to be responsible for solar wind turbulent heating at large scale. Previous investigations demonstrated that Alfven wave magnetic field variations (often estimated in an amplitude of Alfven speed oscillations in the solar wind) well exceed variations of the plasma speed, what indicates on internal instability of the wave configuration. In this presentation we consider possible sources of the observed difference between magnetic field and plasma energies (amplitude of fluctuations of Alfven and plasma speeds) of Alfven waves in the solar wind. We suggest that the effect of a finite ion gyroradius and the corresponding plasma pressure anisotropy should be taken into account to decrease the Alfven speed variations, what should results in stable Alfven wave structure.