09:30 〜 09:45
[PEM08-15] Direct numerical simulation of the Alfvénic solar wind: a theoretical origin of magnetic switchback
★Invited Papers
キーワード：太陽風、乱流、パーカーソーラープローブ
One of the most important early findings from Parker Solar Probe is the ubiquitous presence of sudden reversals of magnetic polarity in the near-Sun solar wind. Such events are called "magnetic switchbacks". The presence of magnetic switchbacks in the near-Sun solar wind is not predicted from the standard solar wind model, in which the solar wind is heated and accelerated by Alfvén waves and turbulence. Our theoretical understanding of the solar wind acceleration is now challenged.
In this presentation, we propose the idea that the magnetic switchbacks emerge as a natural consequence of large-amplitude Alfvén waves, thus explaining the origin of magnetic switchbacks without disturbing the standard understanding. We have performed an unprecedentedly large simulation of the solar wind acceleration from the corona to the sufficiently distant region beyond the orbits (perihelions) of Parker Solar Probe. By imposing Alfvénic fluctuations from the bottom boundary, magnetic switchbacks that exhibit several observational properties are reproduced, meaning that the presence of magnetic switchback is not contradictory to the wave/turbulence-driven solar wind model. The appearance rate (filling factor) of switchback is, however, 100 times smaller than the observed value. We also directly compare our model with Parker Solar Probe observation. The simulated data show quite similar behavior to the observed data in the "quiet phase" in which the number of switchbacks is small. Our conclusion is that a part of magnetic switchbacks originates from large-amplitude Alfvén waves in the solar wind.
In this presentation, we propose the idea that the magnetic switchbacks emerge as a natural consequence of large-amplitude Alfvén waves, thus explaining the origin of magnetic switchbacks without disturbing the standard understanding. We have performed an unprecedentedly large simulation of the solar wind acceleration from the corona to the sufficiently distant region beyond the orbits (perihelions) of Parker Solar Probe. By imposing Alfvénic fluctuations from the bottom boundary, magnetic switchbacks that exhibit several observational properties are reproduced, meaning that the presence of magnetic switchback is not contradictory to the wave/turbulence-driven solar wind model. The appearance rate (filling factor) of switchback is, however, 100 times smaller than the observed value. We also directly compare our model with Parker Solar Probe observation. The simulated data show quite similar behavior to the observed data in the "quiet phase" in which the number of switchbacks is small. Our conclusion is that a part of magnetic switchbacks originates from large-amplitude Alfvén waves in the solar wind.