[M-GI21] Earth and planetary informatics with huge data management

[MGI21-P05] Automatic extraction of frequency sweep rate of chorus from a huge data set of Akebono

Takuya Kanbayashi¹, *Yoshitaka Goto², Yoshiya Kasahara³ (1.Graduate School of Natural Science and Technology, Kanazawa University, 2.Faculty of Electrical and Computer Engineering, Kanazawa University, 3.Information Media Center, Kanazawa University)

Keywords:chorus emission, Akebono satellite, automatic extraction

Chorus emission is one of the most popular plasma waves observed in the Earth's magnetosphere. It has a distinctive feature in spectrum, that is, frequency sweep in a very short time period. The chorus is known to be generated at the magnetic equator and propagates to higher latitude along a magnetic field line. Its generation mechanism has been controversial for many years. In recent years, a theory was proposed that growth of the chorus is caused by a non-linear mechanism. An important point of the theory is a dependence of the frequency sweep rate on wave amplitude.
We performed a statistical analysis of the dependence using data obtained by the Akebono satellite. The Akebono satellite had observed plasma waves in the inner magnetosphere for 26 years. In order to find chorus emissions in the huge data set automatically, we adopted a modified template matching to the data set. One of the essential modifications is that intensity distribution of the template is determined according to that of target chorus elements. By this method, we successfully extracted chorus elements. We, then, investigated relations between frequency sweep rates and wave amplitudes of the extracted chorus elements. As a result, positive correlation is found between them.