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Variation of the Altitude of Auroral Emission During a Substorm Cycle: Stereoscopic Optical Observations During the LAMP Rocket Experiment.

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Title: Variation of the Altitude of Auroral Emission During a Substorm Cycle: Stereoscopic Optical Observations During the LAMP Rocket Experiment.
Authors: Hosokawa, K.1 (AUTHOR) keisuke.hosokawa@uec.ac.jp, Miyoshi, Y.2 (AUTHOR), Mcharg, M.3 (AUTHOR), Ledvina, V.4 (AUTHOR), Hampton, D.4 (AUTHOR), Lessard, M.5 (AUTHOR), Shumko, M.6,7 (AUTHOR), Asamura, K.8 (AUTHOR), Sakanoi, T.9 (AUTHOR), Mitani, T.8 (AUTHOR), Namekawa, T.8,10 (AUTHOR), Nosé, M.11 (AUTHOR), Ogawa, Y.12 (AUTHOR), Jaynes, A.13 (AUTHOR), Halford, A.7 (AUTHOR)
Source: Journal of Geophysical Research. Space Physics. Nov2024, Vol. 129 Issue 11, p1-17. 17p.
Subject Terms: Auroras, Rocket launching, Rockets (Aeronautics), Altitudes, Statistical correlation
Abstract: We estimated the altitude of aurora by combining data from all‐sky cameras at multiple places which were obtained during the LAMP sounding rocket experiment in Alaska on 5 March 2022. During the launch window of the rocket, three high‐speed all‐sky cameras were operative at three stations immediately below the trajectory of the rocket: Poker Flat, Venetie and Fort Yukon. The all‐sky cameras captured all‐sky images with a temporal resolution of 100 Hz (80 Hz for the Fort Yukon case). The method of altitude determination is based on analyses of time‐series of the optical intensity obtained from the all‐sky cameras in Venetie and Poker Flat covering the downrange area of the rocket trajectory. The estimated altitude of pulsating aurora during the rocket experiment was found to be consistent with that derived from the in‐situ observation of precipitating electrons with a model of optical emission, which confirms the feasibility of deriving the emission altitude through correlation analyses using time‐series. The estimated altitude of aurora decreased after the expansion onset of the substorm and stayed slightly below 100 km during the interval of pulsating aurora in the recovery phase. In particular, prompt and brief lowering of the auroral emission, well down to around 90 km, was detected during a transition of auroral form from discrete to diffuse which occurred ∼10 min after the onset. This result implies an existence of a process causing harder electron precipitation operative soon after the start of the expansion phase of auroral substorm. Plain Language Summary: To determine the altitude of the auroras, we analyzed the brightness of the auroras over time using the images obtained during the LAMP sounding rocket experiment in Alaska on 5 March 2022. The altitude of the pulsating auroras observed during the experiment matched the altitude estimated from the direct observation of electrons precipitating into the atmosphere, using a model of optical emissions. This confirms that the method of deriving auroral height through time‐series correlation analysis is effective. The height of the auroras decreased after the substorm began and remained just below 100 km during the period of pulsating auroras in the recovery phase. Specifically, a rapid and brief decrease in auroral height to around 90 km was observed about 10 min after the substorm started, when the aurora changed from discrete to diffuse. This indicates a process that causes more intense electron precipitation shortly after the substorm expansion phase begins. Key Points: Altitude of pulsating aurora emission was estimated by using triangulation of all‐sky camera data from multiple stations in AlaskaAltitude of pulsating diffuse aurora was lower than discrete auroraDecrease of the emission altitude occurred ∼10 min after the substorm onset [ABSTRACT FROM AUTHOR]
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Abstract:We estimated the altitude of aurora by combining data from all‐sky cameras at multiple places which were obtained during the LAMP sounding rocket experiment in Alaska on 5 March 2022. During the launch window of the rocket, three high‐speed all‐sky cameras were operative at three stations immediately below the trajectory of the rocket: Poker Flat, Venetie and Fort Yukon. The all‐sky cameras captured all‐sky images with a temporal resolution of 100 Hz (80 Hz for the Fort Yukon case). The method of altitude determination is based on analyses of time‐series of the optical intensity obtained from the all‐sky cameras in Venetie and Poker Flat covering the downrange area of the rocket trajectory. The estimated altitude of pulsating aurora during the rocket experiment was found to be consistent with that derived from the in‐situ observation of precipitating electrons with a model of optical emission, which confirms the feasibility of deriving the emission altitude through correlation analyses using time‐series. The estimated altitude of aurora decreased after the expansion onset of the substorm and stayed slightly below 100 km during the interval of pulsating aurora in the recovery phase. In particular, prompt and brief lowering of the auroral emission, well down to around 90 km, was detected during a transition of auroral form from discrete to diffuse which occurred ∼10 min after the onset. This result implies an existence of a process causing harder electron precipitation operative soon after the start of the expansion phase of auroral substorm. Plain Language Summary: To determine the altitude of the auroras, we analyzed the brightness of the auroras over time using the images obtained during the LAMP sounding rocket experiment in Alaska on 5 March 2022. The altitude of the pulsating auroras observed during the experiment matched the altitude estimated from the direct observation of electrons precipitating into the atmosphere, using a model of optical emissions. This confirms that the method of deriving auroral height through time‐series correlation analysis is effective. The height of the auroras decreased after the substorm began and remained just below 100 km during the period of pulsating auroras in the recovery phase. Specifically, a rapid and brief decrease in auroral height to around 90 km was observed about 10 min after the substorm started, when the aurora changed from discrete to diffuse. This indicates a process that causes more intense electron precipitation shortly after the substorm expansion phase begins. Key Points: Altitude of pulsating aurora emission was estimated by using triangulation of all‐sky camera data from multiple stations in AlaskaAltitude of pulsating diffuse aurora was lower than discrete auroraDecrease of the emission altitude occurred ∼10 min after the substorm onset [ABSTRACT FROM AUTHOR]
ISSN:21699380
DOI:10.1029/2024JA033036