X‐ray observations of MeV electron precipitation with a balloon‐borne germanium spectrometer
X‐ray observations of MeV electron precipitation with a balloon‐borne germanium spectrometer
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DOI：
10.1029/2002gl015922
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发表时间：
2002-12
影响因子：
5.2
通讯作者：
R. Millan;R. Lin;D. Smith;K. R. Lorentzen;M. McCarthy
中科院分区：
文献类型：
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作者：
R. Millan;R. Lin;D. Smith;K. R. Lorentzen;M. McCarthy
在南极洲上空 18 天的飞行中，MAXIS（MeV 极光 X 射线成像和光谱）气球有效载荷上的高分辨率锗探测器检测到 9 次 X 射线爆发，其通量超过 0.5 MeV。这些持续数分钟到数小时的事件的特征是极其平坦的光谱 (∼E−2)，类似于 1996 年发现的第一个 MeV 事件，表明大部分母体沉淀电子处于相对论能量。在磁纬度 58°–68°（L 值 3.8–6.7）之间检测到 MeV 爆发，但仅在下午晚些时候/黄昏区域（14:30–00:00 MLT）检测到，表明 EMIC（电磁离子回旋加速器）波的散射是一种降水机制。我们估计沉淀 E ≥ 0.5 MeV 电子的平均通量为 ∼360 cm−2s−1，对应于在 L = 3.8–6.7 的八天内沉淀出约 5 × 1025 个此类电子，相比之下，根据 GPS 航天器上的剂量计测量估计约 2 × 1025 个捕获的 0.5–3.6 MeV 电子。这些观测结果表明 MeV 电子沉淀事件是外层相对论电子的主要损失机制。
The high‐resolution germanium detector aboard the MAXIS (MeV Auroral X‐ray Imaging and Spectroscopy) balloon payload detected nine X‐ray bursts with significant flux extending above 0.5 MeV during an 18 day flight over Antarctica. These minutes‐to‐hours‐long events are characterized by an extremely flat spectrum (∼E−2) similar to the first MeV event discovered in 1996, indicating that the bulk of parent precipitating electrons is at relativistic energies. The MeV bursts were detected between magnetic latitudes 58°–68° (L‐values of 3.8–6.7) but only in the late afternoon/dusk sectors (14:30–00:00 MLT), suggesting scattering by EMIC (electromagnetic ion cyclotron) waves as a precipitation mechanism. We estimate the average flux of precipitating E ≥ 0.5 MeV electrons to be ∼360 cm−2s−1, corresponding to about 5 × 1025 such electrons precipitated during the eight days at L = 3.8–6.7, compared to ∼2 × 1025 trapped 0.5–3.6 MeV electrons estimated from dosimeter measurements on a GPS spacecraft. These observations show that MeV electron precipitation events are a primary loss mechanism for outer zone relativistic electrons.