Low Frequency Radio Signals from Giant Air Showers

我们观测到了与大规模空气阵雨有关的无线电信号。对于一次能量为10 ^eV的簇射，可以在大约5公里的核心距离内观测到无线电信号。<19>主要观察到负单极信号，也可获得频率较低的正单极和双极信号，脉宽分布在1~5 μ s之间。我们用一个新的发射模型进行了计算，在这个模型中，无线电信号是由于负电荷过剩电子的减速电离损失过程和大气电场的作用而发射的。负电荷电子的过量在低于几MeV的能量下是显著的。然后我们假设负电荷过剩电子的能量为1MeV，在穿过厚度为1g/cm ^2的大气层时被减速。即使初级宇宙线具有相同的能量，在相同的R处计算的场强取决于到达方向的天顶角（theta）和phi，并且与观察到的强度非常一致。分布也与该模型一致，因为具有相同初级能量和到达方向的theta的簇射中，具有180度的簇射给出了最大的场强。此外，该模型根据R、theta和phi预测正负单极和双极信号。这一结果也与观测结果一致。然而，计算的脉冲宽度比观测信号的脉冲宽度小约三倍。如果我们考虑到由于系统的时间响应和分析中所采用的方法而引起的脉冲变形，则可以解释这种差异的某些部分。我们的计算表明，能量大于10 ^eV的宇宙线的到达方向和初级能量（E）可以分别在3度和0.1 log（E）的精度内测量。<20>

We have observed radio signals associated with large air showers. For showers with primary energies of 10^<19>eV, radio signals can be observed at core distances within about 5km. Negative unipolar signals are mainly observed, while positive unipolar and bipolar signals are also obtained with rather low frequency and their pulse widths distribute from 1 to 5mus. We made a calculation with a new emission model in which radio signals are emitted due to deacceleration of negative charge excess electrons with a process of ionization loss and by the effect of the atmospheric electric field. The excess of negative charge electrons is significant at lower energies than several MeV. Then we have assumed that negative charge excess electrons have energies of 1MeV and are deaccelerated during passing through the atmosphere with thickness of 1g/cm^2. Even though primary cosmic rays have the same energies, calculated field intensities at same R depend on zenith angles(theta) of arrival directions and phi and are much consistent with observed intensities The distribution are also consistent with this model, since a shower with phi of 180 degrees gives the largest field intensities among showers with the same primary energies and theta of arrival direction. Furthermore, this model predicts positive and negative unipolar and bipolar signals according to R, theta and phi. This result is also consistent with observed results. However calculated pulse widths are smaller than those of observed signals by about three times. Some parts of this difference can be explained if we take into account of pulse deformation due to time response of the system and the employed method in the analysis. Our calculation shows that arrival directions and primary energies(E) of cosmic rays with energies above 10^<20>eV can be measured within an accuracy of 3 degrees and 0.1 in log(E) respectively.