Contents 1. Introduction 2. T96 磁場モデルとは 入力パラメータと使用方法 3. 磁気圏対流と電場計算 Weimer 1996モデルと共回転電場 4. 磁気圏モデル内粒子軌道追尾計算の例 磁気圏内プラズマ輸送問題 (研究の背景と計算例) 5. Summary Earth’s Magnetosphere Tsyganenko 1996 (T96) model A data-based model of the geomagnetospheric magnetic field with an explicitly defined realistic magnetopause, large-scale region 1 and 2 Birkeland current systems, and the IMF penetration across the boundary. [Tsyganenko, JGR, p27187, 1996] Input parameters: 1. Geodipole tilt angle, Click here for details 2. Solar wind pressure (0.5~10 nPa), 3. Dst index (-100~+20), 4. IMF By and Bz (-10~+10 nT), ) Click here for details Click here for details 5. GSM position of the observation point. Tsyganenko 1996 model (2) Effects of Geodipole Tilt From http://www-spof.gsfc.nasa.gov/Modeling/group.html QuickTimeý Dz GIF êLí£ÉvÉçÉOÉâÉÄ Ç™Ç±ÇÃÉsÉNÉ`ÉÉǾ å©ÇÈÇ …ÇÕïKóvÇÇ• ÅB Movie The animation above shows how the magnetospheric field varies in response to the dipole wobbling. The background color coding displays the distribution of the scalar difference DB between the total model magnetic field and that of the Earth's dipole only. Yellow and red colors correspond to the negative values of DB (depressed field inside the ring current, in the dayside polar cusps, and in the plasma sheet of the magnetotail). Black and blue colors indicate a compressed field (in the subsolar region on the dayside and in the magnetotail lobes on the nightside). Solar Wind Pdyn and Dst Index Dst Index とは 地上磁場観測の各ステーションのH成分から 長期磁場変動 日変化・季節変化 を取り除いた北向き磁場擾乱の世界平均 Dstは ring currentの強度の指標 ストーム時には負に大きくふれる。 Tsyganenko 1996 model (3) Effects of Time Variation in the Solar Wind Flow Speed From http://www-spof.gsfc.nasa.gov/Modeling/group.html QuickTimeý Dz GIF êLí£ÉvÉçÉOÉâÉÄ Ç™Ç±ÇÃÉsÉNÉ`ÉÉǾ å©ÇÈÇ …ÇÕïKóvÇÇ• ÅB Movie The animation above illustrates the dynamical changes of the global magnetic field in the course of a disturbance: a temporary compression of the magnetosphere by enhanced flow of the solar wind is followed by a tailward stretching of the field lines. Eventually, the increase of the tail magnetic field results in a sudden collapse of the nightside field (a substorm ) and a gradual recovery of the magnetosphere to its pre-storm configuration. Format of the figure is the same as the previous one. IMF By and Bz and Dst Index Magnetospheric Convection during Southward IMF Periods Weimer 1996 Model + corotation Weimer 1996 model: A data-based model of electric potentials in the high-latitude ionosphere based on spherical harmonic coefficients derived by a least error fit of the double-probe electric field measurements by DE-2 with simultaneous IMF data from ISEE-3 or IMP-8. Input parameters: [Weimer, GRL, p2549, 1996] 1. Solar Wind Velocity, 2. IMF By and Bz (-11~11 nT), 3. Geodipole tilt angle, 4. MLT, ILAT of the observation point. Corotation: Assuming 0-tilt dipole magnetic field. Formulation: M: dipole moment, W: angular velocity of the Earth's rotation, Ri: radial distance from the center of Earth to ionospheric altitude. Example of Weimer 1996 Electric Potential IMF northward IMF dawnward IMF duskward IMF southward Tsyganenko 1996 model (4) Effects of Magnetospheric Convection From http://www-spof.gsfc.nasa.gov/Modeling/group.html QuickTimeý Dz GIF êLí£ÉvÉçÉOÉâÉÄ Ç™Ç±ÇÃÉsÉNÉ`ÉÉǾ å©ÇÈÇ …ÇÕïKóvÇÇ• ÅB Movie The animation above illustrates the magnetospheric convection during southward IMF periods. In this case the geomagnetic and interplanetary field lines connect across the magnetospheric boundary, which greatly enhances the transfer of the solar wind mass, energy, and electric field inside the magnetosphere. As a result, the magnetospheric field and plasma become involved in a convection, as illustrated in the above animation. Contents 1. Introduction 2. T96 磁場モデルとは 入力パラメータと使用方法 3. 磁気圏対流と電場計算 Weimer 1996モデルと共回転電場 4. 磁気圏モデル内粒子軌道追尾計算の例 磁気圏内プラズマ輸送問題 (研究の背景と計算例) 5. Summary Conventional View before GEOTAIL Ionospheric Contribution From low-altitude observations [Yau et al., AGU Monogr., 1988] [Chappell, JGR, 1988] From magnetotail observations [Candidi et al., JGR, 1984] [Orsini et al., JGR, 1990] Example of Multi-Composition Ion Flows in the Lobe/Mantle Regions [Seki et al., JGR, 1999] Location of Lobe/Mantle and Multi-Component Ion Flows observed by GEOTAIL [Seki et al., JGR, 1999] Possible Supply Scenarios [Seki et al., JGR, 1998] O+ Trajectory Tracings in Empirical Magnetospheric Models Assumption: 1. Magnetic field line is equi-potential. 2. Geodipole tilt angle is zero. 3. Solar wind conditions are constant in time. ・ Magnetic field model: Tsyganenko 1996 model A data-based model of the geomagnetospheric magnetic field. Input parameters: Solar wind pressure (0.5~10 nPa), Dst index (-100~+20), IMF By and Bz (-10~+10 nT), Geodipole tilt angle, GSM position of the observation point. ・ Electric potential model: Weimer 1996 + corotation Weimer 1996 model: A data-based model of electric potentials in the high-latitude ionosphere. Input parameters: Solar wind velocity, IMF By and Bz (-11~11 nT), Geodipole tilt angle, MLT, ILAT of the observation point. Corotation: Assuming 0-tilt dipole magnetic field. Initial Conditions O+ Trajectory Tracing: initial 500 eV Purely Southward IMF Case: Pdyn=2nPa, Dst=100, By = 0nT, Bz=-10nT, Vsw=450 km/s initial condition: L=10Re, MLT=12h, Energy=500eV Examples of O+ Trajectory Tracing Purely Southward IMF Case: Pdyn=2nPa, Dst=100, By = 0nT, Bz=-10nT, Vsw=450 km/s Initial Conditions (2) O+ Trajectory Tracing: initial 500 eV Purely Southward IMF Case: Pdyn=2nPa, Dst=100, By = 7.01nT, Bz= -7.01nT, Vsw=450 km/s initial condition: L=11Re, MLT=12h, Energy=500eV Dependence on Pitch Angle and Energy O+ Remaining in Magnetosphere [%] Ratio of O+ Ions Remaining in Magnetosphere 70 60 50 solid points: Case 1 (IMF By=0) open diamons: Case 2 (IMF By=0) red: Eo=10 keV green: Eo=2.5 keV blue: Eo=500 eV 40 Average Probability of Transport to Magnetotail Lo Energy Case 1 10 Re 11Re Case 2 11 Re 30 500 eV 31.0% 21.3% 22.3% 20 2.5 keV 7.8% 6.9% 5.1% 10 keV 0.0% 0.3% 3.8% 10 0 0 22.5 45 67.5 90 initial pitch angle at equator [degrees] Conclusions On the basis of obtained results, new aspects are added by this study to the conventional view. Namely, the lobe/mantle plasma is considered to have at least the following four supply routes: • Direct entry of dayside polar ionospheric outflows in the near-Earth regions, • Plasma entry from the magnetosheath through the magnetopause, • Extra energization of polar outflows by a pressure pulse and possibly other mechanisms, • Transport of trapped plasma with isotropic and/or beam distributions in the dayside magnetosphere via dayside reconnection. Plasma Supply to Lobe/Mantle How to Get Started T96磁場モデルのソースコードは、 以下のwebページで公開されています： http://www-spof.gsfc.nasa.gov/Modeling/group.html 公開プログラム概要： T96-01.for： T96モデル GEOPACK.for： IGRF, Dipole, 座標変換, 磁力線traceなど GEOPACK Utilities 各インプットパラメータの時定数 Input parameters: 1. Geodipole tilt angle, 〜１日 予測難しい 2. Solar wind pressure (0.5~10 nPa), 3. Dst index (-100~+20), 〜数日 4. IMF By and Bz (-10~+10 nT), 予測は難しい 5. GSM position of the observation point.
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