Altitude-adjusted corrected geomagnetic coordinates: Definition and functional approximations
Altitude-adjusted corrected geomagnetic coordinates: Definition and functional approximations
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DOI：
10.1002/2014ja020264
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发表时间：
2014-09-01
影响因子：
2.8
通讯作者：
Shepherd, S. G.
中科院分区：
文献类型：
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作者：
Shepherd, S. G.
对用于在地理坐标和高度调整校正地磁 (AACGM) 坐标之间转换的函数近似分析表明，极光和极地区域可能会出现 >50 公里的误差。这些误差是为了更好地近似磁赤道和南大西洋异常附近的 AACGM 坐标而做出的努力的结果。在这些区域中，AACGM 坐标未定义，并且已使用替代坐标。这种对赤道附近区域解的增强和强调导致球谐函数近似函数的精度低于极光和极地区域所需的精度。作为响应，导出了一组新的球谐系数，可以更好地表示这些区域中的 AACGM 坐标。为了确保准确性，这些新的 AACGM 系数仅限于海拔 2000 公里以下。对于海拔 2000 公里以上，建议使用磁力线追踪解决方案。为利用新的 AACGM 系数而开发的软件包能够在任何高度追踪磁场线，从而提高准确性。此外，还使用 5 年历元之间的线性插值来生成从 1965 年至今的整个时期内平稳变化的坐标。这项工作的目的是提供一个更准确的程序来确定极光和极地区域的 AACGM 坐标，以研究磁层和电离层过程。
Analysis of the functional approximations used to transform between geographic and Altitude-Adjusted Corrected Geomagnetic (AACGM) coordinates reveals that errors of >50 km can occur in the auroral and polar regions. These errors are the result of efforts to better approximate AACGM coordinates near the magnetic equator and the South Atlantic Anomaly. In these regions AACGM coordinates are not defined and alternate coordinates have been used. This augmentation and emphasis on the solution in regions near the equator result in spherical harmonic approximating functions that are less accurate than need be in the auroral and polar regions. In response, a new set of spherical harmonic coefficients have been derived that better represent AACGM coordinates in these regions. These new AACGM coefficients are limited to below 2000 km in altitude in order to ensure accuracy. For altitudes above 2000 km, a magnetic field-line tracing solution is recommended. A software package developed to take advantage of the new AACGM coefficients provides the capability of tracing magnetic field lines at any altitude, for improved accuracy. In addition, linear interpolation between 5 year epochs is used to produce coordinates that vary smoothly over the entire period from 1965 to present. The intent of this work is to provide a more accurate procedure for determining AACGM coordinates in the auroral and polar regions for the study of magnetospheric and ionospheric processes.