[P-EM14] Frontiers in solar physics

[PEM14-07] Exploring the Properties of Interplanetary Type III Solar Radio Bursts in the Inner Heliosphere

*Huei-Wen Siao¹、Ya-Hui Yang¹、Shih-Hao Chuang¹ (1.Department of Space Science and Engineering, National Central University, Taiwan)

キーワード：Solar radio emission, Inner Heliosphere, Parker Solar Probe

Interplanetary type III radio bursts, characterized as a fast drift from high- to low-frequency in a dynamic spectrum, are generated by plasma emission mechanism when the accelerated electrons from magnetic reconnection sites move outward along the open magnetic fields through the solar corona and interplanetary space. Type III radio bursts are thus regarded as a diagnostic tool for investigating the properties of electron beams and the ambient plasma medium. The Radio Frequency Spectrometer (RFS) of FIELIDS Experiment on board Parker Solar Probe (PSP) spacecraft provides the high-resolution radio measurements and the corresponding polarization information in the near-Sun interplanetary medium. To understand the polarization properties of interplanetary type III radio bursts close to the Sun, we analyze the distinct and isolated type III bursts detected by PSP during its first ten orbits by estimating the circular polarization sense, the degree of circular polarization (DCP), the time difference between type III intensity and DCP, as well as the frequency dependence of DCP. Our preliminary results show that most of the circular polarization signals are cut off around 1 MHz regardless of the low-cutoff frequency of type III intensity. No preference of circular polarization sense is found in our type III cases. Besides, we notice that there are different patterns shown in the circular polarization maps. The decay time of type III radio bursts with different polarization patterns will also be discussed in this study.