[P-EM13] Dynamics of the Inner Magnetospheric System

[PEM13-18] Direct observation of pulsating aurora electrons: LAMP sounding rocket experiment

*Noda Taisei¹, Yoshizumi Miyoshi¹, Keisuke Hosokawa², Kazushi Asamura³, Takeshi Sakanoi⁴, Marc Lessard⁵, Alison Jaynes⁶, Mike Shumko⁷, Alexa Jean Halford⁸, Taku Namekawa⁹, Takefumi Mitani³, Masahito Nose¹⁰, Geoff McHarg¹¹, Vincent Ledvina¹², Don Hampton¹² (1.Institute for Space-Earth Environmental Research, Nagoya University, 2.University of Electro-Communications, 3.Institute of Space and Astronautical Science, JAXA, 4.Planetary Plasma and Atmospheric Research Center, Grad uate School of Science, Tohoku University, 5.University of New Hampshire, Durham, US, 6.University of Iowa, Iowa, US, 7.Applied Physics Laboratory, Johns Hopkins University, Maryland, US, 8.Goddard Space Flight Center, NASA, 9.The National Institute of Information and Communications Technology, 10.Nagoya City Uni versity, 11.The United States Air Force Academy, Colorado, US, 12.University of Alaska, Fairbanks, US)

Keywords:pulsating aurora, over-darkening, LAMP sounding-rocket

Pulsating aurora is a type of diffuse aurora characterized by quasi-periodic variations in brightness, typically with periods ranging from a few to a few tens of seconds. Over-darkening, a decrease in brightness by several tens of percent relative to the background, frequently occurs immediately after an increase in brightness during the pulsation “ON” phase.
We investigated pulsating aurora and associated over-darkening phenomena using electron data from EPLAS and optical data from AIC, both onboard the LAMP sounding-rocket, which was launched on March 5, 2022 at Poker Flat Research Range, US. EPLAS measures electrons in the 5 eV-15 keV energy range, while AIC observes optical emissions in the 667-680 nm and 844-848 nm wavelength ranges. During the rocket flight, both pulsating aurora and over-darkening events were observed. Near the apex, the optical aurora emission at the magnetic footprint decreased from 3,000 Rayleigh to 1,300 Rayleigh. Simultaneously, EPLAS detected a ~50% reduction in downward energy flux, indicating an over-darkening event. An energy dispersion of precipitating electrons was also observed during the darkening phase.
Time-of-flight (TOF) analysis estimated the modulation source region to be ~55,000 km from the rocket, suggesting that the pitch angle scattering of electrons occurred near the magnetic equator. These findings indicate that the over-darkening in pulsating aurora luminosity modulations is likely caused by the suppression of precipitating electrons near the magnetic equator, possibly due to the wave-particle interactions. In this presentation, we will show multiple over-darkening events during the flight and discuss mechanisms responsible for over-darkening.