Sagan C, Veverka J
Science. 1967 Oct 6;158(3797):110-2. doi: 10.1126/science.158.3797.110.
The small magnetic field strength observed near Mars by Mariner IV suggests that protons from the solar wind may enter the Martian atmosphere and produce ionization in addition to that produced by ultraviolet light and x-rays. It is found that solar protons produce a thin ionized layer at a rate of the order of 3 x 10(3) per cubic centimeter per second at a depth corresponding to the F(1) region in the terrestrial atmosphere. Unless the effective recombinative coefficient is very large (greater than 10(-5) centimeter cubed per second) or unless unusual diffusion effects are present, this layer should have been detected by Mariner IV, and therefore must be present in one of the observed ionized regions. Because of its very compact shape, the subsidiary maximum near 95 kilometers discovered in the Mariner-IV occultation experiment may be the proton ionization peak. If so, the major 120-kilometer maximum is an F(2) layer. Distinction between photon and proton ionization regions can be made by microwave occultation experiments aboard planetary orbiters.
水手四号在火星附近观测到的小磁场强度表明，太阳风质子可能会进入火星大气层，并产生除紫外线和X射线所产生的电离之外的电离现象。研究发现，在与地球大气层F(1)区域相对应的深度处，太阳质子以每秒每立方厘米约3×10(3)的速率产生一个薄电离层。除非有效复合系数非常大（大于每秒10(-5)立方厘米），或者存在异常扩散效应，否则这个层应该已经被水手四号探测到，因此必定存在于观测到的电离区域之一中。由于其形状非常紧凑，在水手四号掩星实验中发现的95公里附近的次极大值可能就是质子电离峰。如果是这样，主要的120公里极大值就是一个F(2)层。通过行星轨道器上的微波掩星实验可以区分光子电离区域和质子电离区域。
