We report the propagation of substorm-associated magnetic fluctuations by multipoint magnetic observations from ground and space in the same meridional plane. The first Quasi-Zenith Satellite (QZS-1), which has a unique orbit of quasi-zenith orbit with an inclination of $$41^\circ$$ 41 ∘ , an apogee of 7.1 $$R_E$$ R E radial distance, and an orbital period of 24 h, can stay for a long time in the near-earth magnetotail away from the magnetic equator. We examined a substorm event during 15:00–16:00 UT on July 09, 2013 when QZS-1 was located at $$31^\circ$$ 31 ∘ dipole latitude and 23.5 h dipole magnetic local time. The Engineering Test Satellite VIII (ETS-VIII), Time History of Events and Macroscale Interactions during Substorms D (THEMIS-D) at a radial distance of $$\sim 10$$ ∼ 10 $$R_E$$ R E , and THEMIS-E at a radial distance of $$\sim 7$$ ∼ 7 $$R_E$$ R E were located near the equator in the similar magnetic meridian. The dipolarization was first observed at THEMIS-D at 15:14:30 UT. Then, $$\sim 1$$ ∼ 1 min later, magnetic fluctuations were observed by ETS-VIII and THEMIS-E. At the same time, the magnetic bay and Pi2 pulsation were observed at low-latitude magnetic observatories and the Radiation Belt Storm Probes B satellite in the inner magnetosphere. We found that QZS-1 away from the equator observed a strong azimuthal magnetic field fluctuation with a long delay of 15 min from the first dipolarization at THEMIS-D near the equator. The speed of the poleward propagating magnetic fluctuation between the ionospheric footprints is calculated to be 310 $$\left[ \mathrm{m}/\mathrm{s}\right]$$ m / s , which is consistent with a typical speed of auroral poleward expansion. A similar time delay of the onset of the negative bay was observed between the Tixie (AACGM $$\hbox {MLAT}=66.8^\circ$$ MLAT = 66 . 8 ∘ ) and Kotelny (AACGM $$\hbox {MLAT}=71.0^\circ$$ MLAT = 71 . 0 ∘ ) observatories near the ionospheric footprint of satellites. We suggest that the long delay time of the magnetic fluctuation at QZS-1 was associated with the crossing of field-aligned current during the poleward expansion of the substorm current system. The distribution of azimuthal magnetic field variations in the magnetosphere indicates that the east side downward current extended more west side in the higher latitude part of the current wedge.

中文翻译：

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亚暴期间子午面中场对齐电流的演变：来自卫星和地面站的多点观测

我们通过在同一子午面的地面和空间多点磁观测报告了亚暴相关磁涨落的传播。第一颗准天顶卫星（QZS-1），它有一个独特的准天顶轨道，倾角为 $$41^\circ$$ 41 ∘ ，远地点为 7.1 $$R_E$$ RE 径向距离，和轨道周期为24 h，可在远离磁赤道的近地磁尾中长期停留。我们检查了 2013 年 7 月 9 日 15:00–16:00 UT 期间的亚暴事件，当时 QZS-1 位于 $31^\circ$$31 ∘ 偶极子纬度和 23.5 h 偶极子磁当地时间。工程测试卫星 VIII (ETS-VIII)，亚暴 D (THEMIS-D) 期间在 $$\sim 10$$ ∼ 10 $$R_E$$ RE 径向距离处事件和宏观相互作用的时间历史，和 THEMIS-E 的径向距离为 $$\sim 7$$ ∼ 7 $$R_E$$ RE 位于类似磁子午线的赤道附近。在 15:14:30 UT 在 THEMIS-D 首次观察到偶极化。然后，$$\sim 1$$ ~ 1 分钟后，ETS-VIII 和 THEMIS-E 观测到磁涨落。同时，在低纬度磁观测台和内磁层的辐射带风暴探测器B卫星上观测到了磁湾和Pi2脉动。我们发现远离赤道的 QZS-1 观测到强方位磁场波动，距赤道附近 THEMIS-D 的第一次偶极有 15 分钟的长延迟。电离层足迹之间的极向传播磁涨落的速度计算为 310 $$\left[ \mathrm{m}/\mathrm{s}\right]$$ m / s ，这与极光向极扩张的典型速度一致。在 Tixie (AACGM $$\hbox {MLAT}=66.8^\circ$$ MLAT = 66 . 8 ∘ ) 和 Kotelny (AACGM $$\hbox {MLAT} =71.0^\circ$$ MLAT = 71 . 0 ∘ ) 卫星电离层足迹附近的观测站。我们认为，QZS-1 磁涨落的长延迟时间与亚暴电流系统向极扩展过程中磁场对齐电流的交叉有关。磁层方位磁场变化的分布表明，东侧向下的洋流在洋流楔的高纬度部分向西延伸。在 Tixie (AACGM $$\hbox {MLAT}=66.8^\circ$$ MLAT = 66 . 8 ∘ ) 和 Kotelny (AACGM $$\hbox {MLAT} =71.0^\circ$$ MLAT = 71 . 0 ∘ ) 卫星电离层足迹附近的观测站。我们认为，QZS-1 磁涨落的长延迟时间与亚暴电流系统向极扩展过程中磁场对齐电流的交叉有关。磁层中方位磁场变化的分布表明，东侧向下的电流在电流楔的高纬度部分向西延伸。在 Tixie (AACGM $$\hbox {MLAT}=66.8^\circ$$ MLAT = 66 . 8 ∘ ) 和 Kotelny (AACGM $$\hbox {MLAT} =71.0^\circ$$ MLAT = 71 . 0 ∘ ) 卫星电离层足迹附近的观测站。我们认为，QZS-1 磁涨落的长延迟时间与亚暴电流系统向极扩展过程中磁场对齐电流的交叉有关。磁层中方位磁场变化的分布表明，东侧向下的电流在电流楔的高纬度部分向西延伸。我们认为，QZS-1 磁涨落的长延迟时间与亚暴电流系统向极扩展过程中磁场对齐电流的交叉有关。磁层中方位磁场变化的分布表明，东侧向下的电流在电流楔的高纬度部分向西延伸。我们认为，QZS-1 磁涨落的长延迟时间与亚暴电流系统向极扩展过程中磁场对齐电流的交叉有关。磁层中方位磁场变化的分布表明，东侧向下的电流在电流楔的高纬度部分向西延伸。