10:45 AM - 12:15 PM
[PEM10-P02] Interaction between the null-separator structure and the plasma dynamics in the northward IMF condition
Keywords:null-separator structure, magnetosphere structure, global MHD simulation
The magnetosphere-ionosphere coupled convection is affected by the magnetic field configuration which is derived from the null-separator structure. Tanaka et al. (2017) revealed that the interaction between the magnetospheric plasma dynamics (convection) and topology of the magnetic field (the null-separator structure) causes the sun-aligned arc and void structure in the polar cap in the northward IMF condition. In the present talk, we will investigate the interaction in detail from the numerical results of the global MHD simulation.
The main findings of this research are as follows;
1. The null-separator structure in the vacuum field forms a torus by closed field lines and two cylinders extending parallel and anti-parallel to the IMF direction [Lau and Finn, 1990]. In the solar wind environment, as the two cylinders bend toward the magnetic equatorial plane on the night side, the anti-parallel magnetic field lines appear in the equatorial plane. However, these anti-parallel field lines can not merge because there is no null point in the equatorial plane of the tail magnetosphere. Therefore, the closed field lines must occupy the region between the two cylinders. This is the formation of the plasma sheet. At the same time, plasma pressure should be enhanced in the plasma sheet with weak magnetic field intensity.
2. The cylinder accompanies the open slot from the tail magnetosphere to the solar wind in the magnetotail. Plasmas and electromagnetic energy of the solar wind intrude the tail magnetosphere through the slot. Furthermore, the plasmas entering through the slot create a plasma plume and shear flow in the magnetotail.
3. The field-aligned current (the sun-aligned arc) in the polar cap is strongly connected to the plasma plume in the magnetotail.
4. When IMFBy is negative, in the northern hemisphere, the Poynting flux passing the dayside magnetopause in the morning side of the separator line enters the inner magnetosphere, and the Poynting flux passing the afternoon region escapes from the magnetosphere through the magnetotail. This behavior is associated with the magnetic field configuration of the null-separator structure.
5. There is a spatial gap between the outermost closed field boundary and the solar wind-open field boundary in the equatorial plane. The plasma flow velocity in this gap becomes faster in the outer region.
References
Lau, Y.-T. and Finn, J. M. (1990), Three-dimensional kinematic reconnection in the presence of field nulls and closed field lines, Astrophysical Journal, 350, 672-691.
Tanaka, T., T. Obara, M. Watanabe, S. Fujita, Y. Ebihara, and R. Kataoka (2017), Formation of the Sun-aligned arc region and the void (polar slot) under the null-separator structure, J. Geophys. Res. Space Physics, 122, doi:10.1002/2016JA023584.
The main findings of this research are as follows;
1. The null-separator structure in the vacuum field forms a torus by closed field lines and two cylinders extending parallel and anti-parallel to the IMF direction [Lau and Finn, 1990]. In the solar wind environment, as the two cylinders bend toward the magnetic equatorial plane on the night side, the anti-parallel magnetic field lines appear in the equatorial plane. However, these anti-parallel field lines can not merge because there is no null point in the equatorial plane of the tail magnetosphere. Therefore, the closed field lines must occupy the region between the two cylinders. This is the formation of the plasma sheet. At the same time, plasma pressure should be enhanced in the plasma sheet with weak magnetic field intensity.
2. The cylinder accompanies the open slot from the tail magnetosphere to the solar wind in the magnetotail. Plasmas and electromagnetic energy of the solar wind intrude the tail magnetosphere through the slot. Furthermore, the plasmas entering through the slot create a plasma plume and shear flow in the magnetotail.
3. The field-aligned current (the sun-aligned arc) in the polar cap is strongly connected to the plasma plume in the magnetotail.
4. When IMFBy is negative, in the northern hemisphere, the Poynting flux passing the dayside magnetopause in the morning side of the separator line enters the inner magnetosphere, and the Poynting flux passing the afternoon region escapes from the magnetosphere through the magnetotail. This behavior is associated with the magnetic field configuration of the null-separator structure.
5. There is a spatial gap between the outermost closed field boundary and the solar wind-open field boundary in the equatorial plane. The plasma flow velocity in this gap becomes faster in the outer region.
References
Lau, Y.-T. and Finn, J. M. (1990), Three-dimensional kinematic reconnection in the presence of field nulls and closed field lines, Astrophysical Journal, 350, 672-691.
Tanaka, T., T. Obara, M. Watanabe, S. Fujita, Y. Ebihara, and R. Kataoka (2017), Formation of the Sun-aligned arc region and the void (polar slot) under the null-separator structure, J. Geophys. Res. Space Physics, 122, doi:10.1002/2016JA023584.