10:00 〜 10:15
[PEM10-04] Disruption of accumulated northward IMF lines in the dayside magnetosheath due to discontinuous southward turning of IMF
キーワード：リコネクション、IMF南北不連続変化
Previous observations and models had shown that discontinuous direction changes of Interplanetary Magnetic Field (IMF) occur the dayside reconnection in the magnetosheath. We reproduced the dayside reconnection in the magnetosheath and the effect at the high latitude magnetosheath with a numerical simulation.
Using the Reproduce Plasma Universe (REPPU) code (Tanaka, 2015), we examined the structure of magnetic field lines in the magnetosheath when IMF turns to southward discontinuously. At first, we ran the simulation under IMF Bz = +5nT for 110 minutes to obtain a quasi-steady magnetosphere. Then, we changed IMF Bz = -3nT. As a result, we could show that the dayside reconnection in the magnetosheath occurs by the deceleration of the discontinuous surface and formation of the antiparallel magnetic structure. This reconnection has continued to completely disrupt accumulated northward IMF lines in the magnetosheath for about 8 minutes. After this process, the magnetic field lines are generated, both ends of which extend to the solar wind region. In addition, these lines are transported to the high latitude magnetosheath and occur the new reconnection with the lobe magnetic field lines. This reconnection has occurred for about 8 minutes and it becomes a quasi-steady magnetosheath under the southward IMF gradually. However, these reconnections have not always occurred for 8 minutes. In the presentation, we discuss a reconnection time universality when we add to IMF By or changed the dynamic pressure.
Using the Reproduce Plasma Universe (REPPU) code (Tanaka, 2015), we examined the structure of magnetic field lines in the magnetosheath when IMF turns to southward discontinuously. At first, we ran the simulation under IMF Bz = +5nT for 110 minutes to obtain a quasi-steady magnetosphere. Then, we changed IMF Bz = -3nT. As a result, we could show that the dayside reconnection in the magnetosheath occurs by the deceleration of the discontinuous surface and formation of the antiparallel magnetic structure. This reconnection has continued to completely disrupt accumulated northward IMF lines in the magnetosheath for about 8 minutes. After this process, the magnetic field lines are generated, both ends of which extend to the solar wind region. In addition, these lines are transported to the high latitude magnetosheath and occur the new reconnection with the lobe magnetic field lines. This reconnection has occurred for about 8 minutes and it becomes a quasi-steady magnetosheath under the southward IMF gradually. However, these reconnections have not always occurred for 8 minutes. In the presentation, we discuss a reconnection time universality when we add to IMF By or changed the dynamic pressure.