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Computer Simulation on Interaction of the Solar Wind with Jovian and Kronian Magnetospheres
http://hdl.handle.net/2237/8462
http://hdl.handle.net/2237/846269387506-36e1-44a6-a22d-d9ddf3dffddb
| 名前 / ファイル | ライセンス | アクション |
|---|---|---|
fukazawa_d_thesis.pdf (8.7 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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| 公開日 | 2007-06-26 | |||||
| タイトル | ||||||
| タイトル | Computer Simulation on Interaction of the Solar Wind with Jovian and Kronian Magnetospheres | |||||
| 言語 | en | |||||
| 著者 |
FUKAZAWA, Keiichiro
× FUKAZAWA, Keiichiro× 深沢, 圭一郎 |
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| アクセス権 | ||||||
| アクセス権 | open access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_abf2 | |||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Both Jupiter and Saturn have similar characters such as rapid rotation, the moon providing plasmas into the magnetosphere and giant body. The major difference is the magnitude of the intrinsic magnetic field. Due to these characteristics Jupiter and Saturn are often compared each other. In this dissertation, we study the dynamics of the Jovian magnetosphere and that of the Kronian magnetosphere. It has long been recognized that the solar wind and interplanetary magnetic field (IMF) control magnetospheric dynamics at the Earth. On the other hand, a massive rotating equatorial plasma sheet dominates the Jovian magnetosphere, and the solar wind and the IMF are not thought to be as important as at Earth. However, in our following simulation study, we found that for a purely northward IMF the Jovian magnetosphere reached an unsteady state in which a nearly periodic series of magnetic X and O lines are launched tailward. In this study we have carried out a series of three-dimensional global magnetohydrodynamic (MHD) simulations to investigate the causes of dynamic behavior of the Jovian magnetosphere, Both the effects of changes in the solar wind dynamic pressure and IMF are considered. First, the effects of dynamic pressure on the magnetospheric configuration are examined in the absence of IMF by calculating the magnetospheric configuration for four levels of solar wind dynamic pressure. The simulation started by setting the pressure to 0.090 nPa and ran the code until a quasi-steady magnetosphere resulted. Then the pressure decreased three times until it reached 0.011 nPa. In the all simulations we ran the code until a quasi-steady magnetosphere resulted. Next we simulate the magnetosphere for northward and southward IMF starting from the configuration with 0.011 nPa. Starting from the simulation with southward IMF, a series of northward IMF simulations were examined in which both the IMF magnitude and dynamic pressure were varied. When B_z was 0.105 nT and the pressure was 0.011 nPa, X/O pairs were launched tailward with an average period of 34.3 hours. For a fixed B_z of 0.105 nT the period increased with increasing dynamic pressure until at 0.045 nPa when the tail settled into a steadily reconnecting configuration. For a fixed dynamic pressure of 0.090 nPa and B_z = 0.420 nT the X/O pairs formed with two periods (～20 hours and ～50 hours) while the reconnection again became steady when the IMF was reduced to 0.105 nT. Thus higher dynamic pressure makes the period of plasmoid ejection longer while increasing northward IMF makes the period shorter. This behavior can be understood by noting that the solar wind dynamic pressure controls the location of the rotation dominated region while the IMF controls the location of the tail X-line. When the tail X-line is near the outer boundary of the rotation dominated region, the injected flux from the neutral line can rotate around Jupiter and contribute to the reconnection occurring multiple times. Saturn was thought to have aspects similar to both Jupiter and the Earth with internally driven and solar wind driven dynamics. Recently before arriving at Saturn, Cassini spacecraft observed the upstream solar wind conditions of Saturn and simultaneously Hubble Space Terrescope(HST) observed the aurora of Saturn. As the results of these observations, two explanations have been reported. One is that the Saturn’s aurorae is controlled by the solar wind dynamic pressure, another is that the IMF direction is more important than the dynamic pressure on the aurora emission. To investigate the influence of the IMF on Kronian magnetosphere and aurora brightness, we have used three dimensional MHD simulations. The magnetosphere for three cases with no IMF, northward and southward IMFs were modeled. For all of he simulations the solar wind dynamic pressure was set to the average value at Saturn’s orbit. The subsolar magnetopause and bow shock are insensitive to changes in IMF. In the Y-direction the boundaries are farthest from Saturn for the case without IMF and farther for southward IMF than northward IMF. Flow vortices formed in the magnetotail for all three cases. They were confined to the inner magnetotail for northward IMF but were found throughout the tail for the southward and no IMF cases. For the no IMF the vortices were generated in the morning sector where the rotating Kronian flows were opposite to the solar wind induced flows. For southward IMF the vorticity results from the interaction of flow driven by high latitude reconnection and corotation. For northward IMF vortives were generated in the early morning and evening where the flow from reconnection in Saturn’s tail were opposite to the solar wind induced flow. We used the energy flux toward the ionosphere and upward field-aligned currents as a proxy for diffuse and discrete auroral emissions respectively. For the no IMF case the energy flux is largest in the morning sector poleward of 75°latitude consistent with HST observations during January 2004. With southward IMF the distribution of energy flux becomes more symmetric than that of no and northward IMF cases. The energy flux in the polar cusp depends on IMF orientation with larger energy flux for northward IMF. Strong upward field-aligned currents extend to the morning sector when the IMF is northward. The strongest field-aligned currents are generated in the flow vortices. | |||||
| 言語 | en | |||||
| 内容記述 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 名古屋大学博士学位論文 学位の種類:博士(工学)(課程) 学位授与年月日:平成19年3月23日 | |||||
| 言語 | ja | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_db06 | |||||
| 資源タイプ | doctoral thesis | |||||
| 書誌情報 |
発行日 2007-03-23 |
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| 学位名 | ||||||
| 言語 | ja | |||||
| 学位名 | 博士(工学) | |||||
| 学位授与機関 | ||||||
| 学位授与機関識別子Scheme | kakenhi | |||||
| 学位授与機関識別子 | 13901 | |||||
| 言語 | ja | |||||
| 学位授与機関名 | 名古屋大学 | |||||
| 言語 | en | |||||
| 学位授与機関名 | Nagoya University | |||||
| 学位授与年度 | ||||||
| 値 | 2006 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 2007-03-23 | |||||
| 学位授与番号 | ||||||
| 学位授与番号 | 甲第7500号 | |||||
| フォーマット | ||||||
| 値 | application/pdf | |||||
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| 値 | publisher | |||||
| URI | ||||||
| 識別子 | http://hdl.handle.net/2237/8462 | |||||
| 識別子タイプ | HDL | |||||
