1991 Fiscal Year Final Research Report Summary
Low Frequency Radio Signals from Giant Air Showers
| Project/Area Number |
02452023
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
KAKIMOTO Fumio Tokyo Institute of Technology, Department of Physics, Assistant Professor, 理学部, 助教授 (00092544)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUBARA Yutaka Nagoya University, STE Laboratory, Assistant Professor, 理学部(助手) 現名古屋大学・太陽・地球環境研究所, 助教授 (80202323)
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| Project Period (FY) |
1990 – 1991
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| Keywords | the most energetic cosmic rays / air showers / a new technique / radio signals with low frequencies |
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| Research Abstract |
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.
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