P013-0003
Ground based observation of optical planetary lightning flashes with Planetary Lightning Detector
Ground based observation of optical planetary lightning flashes with Planetary Lightning Detector
Tuesday, 8 December 2020
Poster
Abstract:
The lightning detection can be used to understand the atmospheric dynamics on the other planets. The convection generate the lightning in planetary atmosphere. In the case of Jupiter, the lightning flashes have been observed by spacecrafts. Previous studies (e.g. Gierasch et al., 2000; Ingersoll et al., 2000) suggested that zonal jet is driven by the many small-scale eddies which are received their energy from the moist convection. Lightning is correlated with the moist convection, and thus lightning observation can be useful to investigate the formation mechanism of Jupiter’s zonal jet. The existence of Venusian lightning is controversial for 40 years. No unambiguous lightning flash events have been detected by LAC onboard AKATSUKI Venus Climate orbiter (Lorenz et al., 2019). If we can the existence of Venusian lightning, it could also be used to have access to the Venusian atmospheric dynamics.
We have developed the Planetary Lightning Detector (PLD) to understand the relationship between lightning and atmospheric dynamics of Jupiter and Venus. The PLD is the high-speed and high-sensitive photon counting sensor by using a photomultiplier tube to obtain the light curve of planetary lightning flashes. We can obtain the light-curve with up to sampling rate of 2.0×104 s-1. We will obtain the distribution of lightning and its frequency and the, we derive the distribution of a few tens km scale convections.
The emission line of 777.4 nm is the most predominant in the Venus lightning optical spectrum (Borucki et al., 1996). PLD equips narrowband filter of 777 nm (FWHM = 1 nm). The maximum time resolution is about 2×104 points/s to observe the light curve with photomultiplier tube. The FOV of PLD can be selected from some pinholes, and a slit. Some signal processing is used to remove the shot noise and large time scale variation by Earth’s atmosphere. We have observed Venus from May 2020 and Jupiter from Jan 2019. In our Venus observation, we could find possibly several lightning events having large count values. The event rate of possible lightning is about 10-11 [s-1km-2]. It is ten times larger than the rate of previous study 2.7×10-12 [s-1km-2] (Hansell et al., 1995). Our total observation time is not enough to compare with the previous study. We will increase the total observation time to over 3 hour.
We have developed the Planetary Lightning Detector (PLD) to understand the relationship between lightning and atmospheric dynamics of Jupiter and Venus. The PLD is the high-speed and high-sensitive photon counting sensor by using a photomultiplier tube to obtain the light curve of planetary lightning flashes. We can obtain the light-curve with up to sampling rate of 2.0×104 s-1. We will obtain the distribution of lightning and its frequency and the, we derive the distribution of a few tens km scale convections.
The emission line of 777.4 nm is the most predominant in the Venus lightning optical spectrum (Borucki et al., 1996). PLD equips narrowband filter of 777 nm (FWHM = 1 nm). The maximum time resolution is about 2×104 points/s to observe the light curve with photomultiplier tube. The FOV of PLD can be selected from some pinholes, and a slit. Some signal processing is used to remove the shot noise and large time scale variation by Earth’s atmosphere. We have observed Venus from May 2020 and Jupiter from Jan 2019. In our Venus observation, we could find possibly several lightning events having large count values. The event rate of possible lightning is about 10-11 [s-1km-2]. It is ten times larger than the rate of previous study 2.7×10-12 [s-1km-2] (Hansell et al., 1995). Our total observation time is not enough to compare with the previous study. We will increase the total observation time to over 3 hour.