Solar EUV measurements at Venus based on photoelectron emission from the Pioneer Venus Langmuir Probe
Solar EUV measurements at Venus based on photoelectron emission from the Pioneer Venus Langmuir Probe
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基于先锋金星朗缪尔探测器的光电子发射在金星进行太阳能 EUV 测量
DOI：
10.1029/ja093ia07p07282
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
R. Theis
中科院分区：
文献类型：
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作者：
L. H. Brace;W. Hoegy;R. Theis
自1979年以来，来自先锋金星朗缪尔探测器的光电子流提供了对金星太阳极紫外线通量的测量。该电流是收集器的光电产额和波长短到足以引起发射的太阳光谱的产物。计算表明，大约51%的发射是由于莱曼α（1216 A），46%是由550和1100 A之间的波长产生的，不到3%是由于波长长于莱曼α。因此，朗缪尔探测器提供了一个直接测量太阳EUV总通量的方法，包括产生金星电离层和加热和激发热层中中性粒子的大部分波长。本文介绍了测量技术，并给出了1979年至1987年期间获得的光电流日平均测量值。光电流表现出与太阳周期和太阳自转有关的变化，以及主要的7.2个月周期。我们提出了基于测量的EUV的三个指数：（1）光电发射电流本身，（2）总EUV通量，和（3）F10.7类太阳指数。将这些与在地球上同时进行的相关测量进行比较。由于测量是在金星上进行的，它们对许多先锋金星的调查比地球或地球卫星对太阳的观测更有用。这些数据还可以帮助太阳物理学家跟踪太阳上EUV发射区域的强度，而这些区域在地球上是不可见的。本文还给出了太阳耀斑事件的极紫外辐射通量分布图。未来，该方法还可应用于彗星使命，以获得入射太阳EUV通量，测量彗星大气的EUV消光剖面，并通过尘埃和气体撞击收集器时产生的电离直接采样彗星的尘埃和气体环境。
The photoelectron current from the Pioneer Venus Langmuir probe has provided measurements of the solar extreme ultraviolet flux at Venus since 1979. This current is the product of the photoelectric yield of the collector and the solar spectrum at wavelengths short enough to cause emission. Calculations show that approximately 51% of the emission is due to Lyman α (1216 A), 46% is produced by wavelengths between 550 and 1100 A, and less than 3% is due to wavelengths longer than Lyman α. Thus the Langmuir probe provides a direct measure of the total solar EUV flux, including most of the wavelengths that produce the Venus ionosphere and heat and excite neutrals in the thermosphere. The measurement technique is described, and the daily average measurements of photocurrent obtained between 1979 and 1987 are presented. The photocurrents exhibit variations related to the solar cycle and solar rotation, as well as a major 7.2-month periodicity. We present three indices of EUV based on the measurements: (1) the photoemission current itself, (2) the total EUV flux, and (3) an F10.7-like solar index. These are compared with related measurements made simultaneously at Earth. Since the measurements are made at Venus, they are more useful for many Pioneer Venus investigations than are Earth or Earth satellite observations of the Sun. These data may also help solar physicists track the intensity of EUV emission regions on the Sun while they are not visible from the Earth. The EUV flux profile of a solar flare event is also illustrated. In the future the method also could be applied on a comet mission to obtain the incident solar EUV flux, to measure the EUV extinction profiles of the cometary atmosphere, and to sample directly the dust and gas environment of the comet through the ionization the dust and gas produce when they impact the collector.