# Contents 1. Introduction 2. T96 磁場モデルとは 3. 磁気圏対流と電場計算 4. 磁気圏モデル内粒子軌道追尾計算の例 5.Summary 入力パラメータと使用方法 Weimer 1996 モデルと共回転電場 磁気圏内プラズマ輸送問題 ( 研究の背景と計算例 )

## Presentation on theme: "Contents 1. Introduction 2. T96 磁場モデルとは 3. 磁気圏対流と電場計算 4. 磁気圏モデル内粒子軌道追尾計算の例 5.Summary 入力パラメータと使用方法 Weimer 1996 モデルと共回転電場 磁気圏内プラズマ輸送問題 ( 研究の背景と計算例 )"— Presentation transcript:

Contents 1. Introduction 2. T96 磁場モデルとは 3. 磁気圏対流と電場計算 4. 磁気圏モデル内粒子軌道追尾計算の例 5.Summary 入力パラメータと使用方法 Weimer 1996 モデルと共回転電場 磁気圏内プラズマ輸送問題 ( 研究の背景と計算例 )

Earth’s Magnetosphere

[Tsyganenko, JGR, p27187, 1996] 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. Input parameters: 1. Geodipole tilt angle, 2. Solar wind pressure (0.5~10 nPa), 3. Dst index (-100~+20), 4. IMF By and Bz (-10~+10 nT), 5. GSM position of the observation point. Click here for details )

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). Tsyganenko 1996 model (2) Effects of Geodipole Tilt From http://www-spof.gsfc.nasa.gov/Modeling/group.html Movie

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。

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. Tsyganenko 1996 model (3) Effects of Time Variation in the Solar Wind Flow Speed From http://www-spof.gsfc.nasa.gov/Modeling/group.html Movie

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: 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. [Weimer, GRL, p2549, 1996]

Example of Weimer 1996 Electric Potential IMF northward IMF duskward IMF southward IMF dawnward

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. Tsyganenko 1996 model (4) Effects of Magnetospheric Convection From http://www-spof.gsfc.nasa.gov/Modeling/group.html Movie

Contents 1. Introduction 2. T96 磁場モデルとは 3. 磁気圏対流と電場計算 4. 磁気圏モデル内粒子軌道追尾計算の例 5.Summary 入力パラメータと使用方法 Weimer 1996 モデルと共回転電場 磁気圏内プラズマ輸送問題 ( 研究の背景と計算例 )

Conventional View before GEOTAIL

Ionospheric Contribution From low-altitude observations [Chappell, JGR, 1988][Yau et al., AGU Monogr., 1988] From magnetotail observations [Orsini et al., JGR, 1990][Candidi et al., JGR, 1984]

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

Summary of Trajectory Tracings Probability of transport from the dayside magnetosphere to the tail lobe/mantle decreases with increasing energy in the energy range of 0.5-10 keV. Upper limit of energy of O + ions which can reach the magnetotail without encountering the magnetopause becomes larger in the finite IMF By case than in the purely southward IMF case. O + ions which have field-aligned pitch angles at equator (PAe) are transported to the magnetotail more frequently than perpendicular-PAe ions.

Direct entry of dayside polar ionospheric outflows in the near-Earth regions,Direct entry of dayside polar ionospheric outflows in the near-Earth regions, Plasma entry from the magnetosheath through the magnetopause,Plasma entry from the magnetosheath through the magnetopause, Extra energization of polar outflows by a pressure pulse and possibly other mechanisms,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.Transport of trapped plasma with isotropic and/or beam distributions in the dayside magnetosphere via dayside reconnection. 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:

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

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