TY - JOUR
T1 - Fast-moving diffuse auroral patches
T2 - A new aspect of daytime Pc3 auroral pulsations
AU - Motoba, Tetsuo
AU - Ebihara, Yusuke
AU - Kadokura, Akira
AU - Engebretson, Mark J.
AU - Lessard, Marc R.
AU - Weatherwax, Allan T.
AU - Gerrard, Andrew
N1 - Funding Information:
All-sky optical measurements at South Pole Station have been conducted under a joint project between the New Jersey Institute of Technology, Merrimack College (USA), Kyoto University, and National Institute of Polar Research (Japan) with support provided from the U.S. National Science Foundation (NSF) under awards PLR-1247975 and ANT-0638587 and the Japanese Antarctic Research Expedition (JARE) program. Search coil magnetometer at South Pole Station is operated jointly by Augsburg College and the University of New Hampshire with support from NSF grants PLR-1341493 and PLR-1341677. The optical and search coil magnetometer data used in this paper were obtained through the individual PIs. The authors thank the wintering science research associate at South Pole Station, in particular Ethan R. Good who devotedly maintained the optical instruments in the 2012 austral winter season. The OMNI data were obtained from the GSFC/SPDF OMNIWeb interface at http://omniweb.gsfc.nasa.gov.
Publisher Copyright:
©2016. American Geophysical Union. All Rights Reserved.
PY - 2017/2/1
Y1 - 2017/2/1
N2 - Auroral pulsations are a convenient diagnostic of wave-particle interactions in the magnetosphere. A case study of a daytime Pc3 (22–100 mHz) auroral pulsation event, measured with a ~2 Hz sampling all-sky camera at South Pole Station (74.4°S magnetic latitude) on 17 May 2012, is presented. The daytime Pc3 auroral pulsations were most active in a closed field line region where the aurora was dominated by diffuse green-line emissions and within ±2 h of magnetic local noon. Usually, but not always, the corresponding periodic variations were recorded with a colocated search coil magnetometer. Of particular interest is the two-dimensional auroral signature, indicating that the temporal luminosity variations at a given point were due to repeated formation and horizontal motion of faint, nonpulsating auroral patches with scale sizes of ~100 km. The individual patches propagated equatorward with speeds of 15 km s−1 up to 20–25 km s−1 one after another along the magnetic meridian through local magnetic zenith. These properties differ considerably from typical pulsating aurorae, being periodic on-off luminosity variations in a particular auroral patch and drifting in accordance with the convection electric field in the magnetosphere. We speculate that such repetitive patterns of the fast-moving auroral patches, being another aspect of the daytime Pc3 auroral pulsations, may be a visible manifestation of compressional Pc3 waves which propagate earthward and cause modulation of precipitating keV electron fluxes in the dayside outer magnetosphere.
AB - Auroral pulsations are a convenient diagnostic of wave-particle interactions in the magnetosphere. A case study of a daytime Pc3 (22–100 mHz) auroral pulsation event, measured with a ~2 Hz sampling all-sky camera at South Pole Station (74.4°S magnetic latitude) on 17 May 2012, is presented. The daytime Pc3 auroral pulsations were most active in a closed field line region where the aurora was dominated by diffuse green-line emissions and within ±2 h of magnetic local noon. Usually, but not always, the corresponding periodic variations were recorded with a colocated search coil magnetometer. Of particular interest is the two-dimensional auroral signature, indicating that the temporal luminosity variations at a given point were due to repeated formation and horizontal motion of faint, nonpulsating auroral patches with scale sizes of ~100 km. The individual patches propagated equatorward with speeds of 15 km s−1 up to 20–25 km s−1 one after another along the magnetic meridian through local magnetic zenith. These properties differ considerably from typical pulsating aurorae, being periodic on-off luminosity variations in a particular auroral patch and drifting in accordance with the convection electric field in the magnetosphere. We speculate that such repetitive patterns of the fast-moving auroral patches, being another aspect of the daytime Pc3 auroral pulsations, may be a visible manifestation of compressional Pc3 waves which propagate earthward and cause modulation of precipitating keV electron fluxes in the dayside outer magnetosphere.
KW - daytime auroral pulsations
KW - outer magnetospheric dynamics
KW - wave-particle interactions
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U2 - 10.1002/2016JA023285
DO - 10.1002/2016JA023285
M3 - Article
AN - SCOPUS:85011634632
SN - 2169-9380
VL - 122
SP - 1542
EP - 1554
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
IS - 2
ER -