The cleft ion plasma environment at low solar activity (extended abstract)
The cleft ion plasma environment at low solar activity (extended abstract)
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太阳活动低时的裂隙离子等离子体环境（扩展摘要）
DOI：
10.1029/96gl00843
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
J. Holtet
中科院分区：
文献类型：
--
作者：
T. Moore;C. Pollock;M. Adrian;P. Kintner;R. Arnoldy;K. Lynch;J. Holtet
裂隙离子喷泉能量化区域探测 (SCIFER) 任务已对低能 (0.3–25 eV) 离子等离子体成分和三维差分速度分布进行了测量。在太阳活动较低的情况下，SCIFER 向极地移动，进入白天的午前裂隙区域。上段测量表明，下裂缝顶面的密度随着高度的变化而快速下降（在1400公里高度处ne≤300cm−3），并且有效载荷浮动电位从典型的约1伏特的电离层负值变为与阳光下ne≤1000cm−3一致的零或正值。当有效载荷向极地移动并接近远地点时，离子等离子体通量突然增加。在电子等离子体频率下对朗缪尔波的观测表明，在 1 公里的尺度长度上，等离子体密度增加了 6 倍。从场垂直离子加热到 T⟂∼1 eV 的情况判断，等离子体密度边界与进入裂隙区域一致，H+ 具有数 km/s 的向上整体流动，O+ 具有 1-2 km/s 的向上整体流动，并且核心 H+ 中具有特征能量 ∼4 eV 的温暖超热尾部。在离子温度和等离子体密度之间观察到负相关，这与电流驱动波的加热一致。该区域的加热裂隙等离子体以 H+ 为主，这与 DE-1 和 Akebono 在太阳活动极大期附近从 3000-6000 公里高度观察到的以 O+ 为主形成鲜明对比。
Low energy (0.3–25 eV) ion plasma composition and three-dimensional differential velocity distribution measurements have been made from the Sounding of the Cleft Ion Fountain Energization Region (SCIFER) mission. SCIFER traveled poleward into the dayside prenoon cleft region under conditions of low solar activity. Upleg measurements show that the subcleft topside had a rapid density fall-off with altitude (ne ≤ 300 cm−3 at 1400 km altitude), and that the payload floating potential changed from typical ionospheric negative values of about a volt, to zero or positive values consistent with ne ≤ 1000 cm−3 in sunlight. As the payload moved poleward and approached apogee, the ion plasma flux abruptly increased. Observations of Langmuir waves at the electron plasma frequency show the plasma density increased by a factor of 6 over a scale length of ∼1 km. The plasma density boundary coincided with passage into the cleft region, as judged from the appearance of field-perpendicular ion heating to T⟂∼1 eV, with upward bulk flows of several km/s for H+, and 1–2 km/s for O+, and warm superthermal tails in the core H+ with characteristic energy ∼4 eV. An inverse association was observed between ion temperature and plasma density, consistent with heating by current-driven waves. The heated cleft plasma was H+-dominated in this region, in stark contrast to the O+ domination observed from 3000–6000 km altitude by DE-1 and Akebono near solar maximum.