HAO Colloquium - Chen Shi, UCLA

Large-scale structures and their effects on the evolution of the solar wind turbulence

We study the effects of the large-scale stream interaction region (SIR) and the heliospheric current sheet (HCS) on the evolution of magnetohydrodynamic (MHD) turbulence in the solar wind. We carry out two-dimensional MHD simulations with the spherical expansion of the solar wind taken into account (the expanding-box-model). We show that these large-scale structures strongly affect the waves and turbulence in the solar wind. The SIR weakens the dominance of the outward propagating Alfven waves, consistent with the observation. It leads to an excess of the kinetic energy over magnetic energy at small scales, in contrast to the observation which shows a magnetic energy excess. The HCS has stronger effect in weakening the dominance of the outward Alfven waves than the SIR. The magnetic energy gradually exceeds the kinetic energy around the HCS. We do a superposed epoch analysis of the HCS using the 1-minute OMNI2 data. The data confirms that the outward Alfven wave dominance is significantly decreased and the magnetic energy dominance is strengthened near HCS. These effects of the HCS are stronger near solar maximum than near solar minimum.

Date and time: 
Wednesday, January 15, 2020 - 2:00pm to 3:00pm