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The Diffuse Auroral Eraser
Journal article   Open access   Peer reviewed

The Diffuse Auroral Eraser

R. N. Troyer, A. N. Jaynes, S. L. Jones, D. J. Knudsen and T. S. Trondsen
Journal of geophysical research. Space physics, Vol.126(3), e2020JA028805
03/2021
DOI: 10.1029/2020JA028805
url
https://doi.org/10.1029/2020JA028805View
Published (Version of record) Open Access

Abstract

The source of diffuse aurora has been widely studied and linked to electron cyclotron harmonic and upper‐band chorus waves. It is known that these waves scatter 100s of eV to 10s of keV electrons from the plasma sheet, but the relative contribution of each wave type is still an open question. In this study, we report an interesting and unusual auroral feature observed on March 15, 2002. We believe that these observations could help further our understanding of waves associated with diffuse aurora. This diffuse auroral feature is characterized by four phases: (1) the initial phase exhibiting regular diffuse aurora; (2) the brightening phase, where an east‐west auroral stripe rapidly brightens; (3) the eraser phase, where the stripe dims to below its initial state; and (4) the recovery phase, where the diffuse aurora returns to its original brightness. Using a superposed epoch analysis of 22 events, we calculate the average recovery phase time to be 20 s, although this varies widely between events. We hypothesize that the process responsible for these auroral eraser events could be the result of chorus waves modulating diffuse aurora. Plain Language Summary Aurora are caused by electrons from within the magnetic bubble that surrounds Earth, called the magnetosphere. Sometimes these electrons are deposited into our upper atmosphere, producing light. This process can also transfer large amounts of energy from the magnetosphere to the atmosphere, thus potentially affecting the climate. Pictures of the aurora usually depict discrete green curtains, but this is not the only type of aurora. Diffuse aurora is another, which look like a faint glow over large portions of the sky. Diffuse aurora is extremely common, but not well understood. We have found an unusual process within diffuse aurora that could improve our understanding. We call it a diffuse auroral eraser. We found these events in a movie taken the night of March 15, 2002 in Churchill, MB, Canada. They appear as a section of diffuse aurora that rapidly brightens, then disappears and also erases the background aurora. Then, over the course of several tens of seconds, the diffuse aurora recovers to its original brightness. We calculated the average recovery time by overlaying plots of brightness from each of the 22 events that we found. This average time was 20 s, although it varied widely between individual events. Key Points We identify an interesting and unusual feature, called a diffuse auroral eraser, which occurred during low magnetic activity An auroral eraser starts as diffuse aurora that brightens, dims to lower than its initial level, then recovers to its initial brightness We found the average recovery time to be 20 s with a 13 s standard deviation
 diffuse aurora diffuse aurora eraser magnetosphere ionosphere coupling pulsating aurora

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