[P-EM10] Dynamics of Magnetosphere and Ionosphere

[PEM10-21] PARM-HEP Observation of Microburst Precipitation over Pulsating Aurora

*Taku Namekawa^1,2, Takefumi Mitani¹, Kazushi Asamura¹, Yoshizumi Miyoshi³, Keisuke Hosokawa⁴, Yasunobu Ogawa⁵ (1.Japan Aerospace Exploration Agency, 2.The University of Tokyo, 3.Nagoya University, 4.The University of Electro-Communications, 5.National Institute of Polar Research)

Keywords:microburst, pulsating aurora, sounding rocket

The phenomenon called microburst is that large numbers of radiation belt electrons of several hundred keV to several MeV precipitate to the Earth’s auroral atmosphere on a time scale of less than one second. It is suggested that this phenomenon is largely related to the loss mechanism of the outer radiation belt electrons [e.g. Thorne et al., 2005; Clilverd et al., 2006; Dietrich et al., 2010; Lorentzen et al., 2001]. It is suggested that microbursts are caused by pitch angle scattering due to magnetospheric whistler-mode chorus waves propagating from the magnetic equatorial plane to higher magnetic latitudes, but observational verification has not been made yet [Horne & Thorne, 2003; Kennel & Petscheck, 1966; Miyoshi et al., 2020].
The mechanism of microbursts is similar to that of the pulsating aurora observed in the Earth’s polar region, and there is a possibility that the origin of microburst can be clarified by proving simultaneous occurrence of microburst and pulsating aurora. For that purpose, we have developed a high-energy electron detector (HEP) for the observation of sub-relativistic - relativistic energy electrons that make up the microburst, which is one of the core instruments of the PARM instrument package developed for the simultaneous observation of the pulsating aurora and microburst. The first model of this instrument was installed by the international student sounding rocket experiment RockSat-XN and launched on the dayside (MLT = 12.4) under quiet condition at 09:13:00 UT on January 13, 2019. Although simultaneous observation with pulsating aurora was impossible and the significant microbursts cannot be detected, we could not observe the pulsating aurora simultaneously or detect significant microbursts, we observed the energy spectrum of quasi-relativistic energy electrons likely to be caused by the wave-particle interactions between whistler-mode waves and sub-relativistic electrons in the quiet dayside magnetosphere [Namekawa et al., 2021]. An improved version of HEP is also installed by LAMP (Loss through Auroral Microburst Pulsation) sounding rocket experiment. An anti-coincidence counter was loaded in this model to eliminate the effects of penetrating particles such as galactic cosmic rays. In this presentation, we will show the outline of HEP and the observation results of RockSat-XN and LAMP experiments.