Study of a global auroral Pc5 pulsation event with concurrent ULF waves

Abstract

We present results from a study of concurrent, periodic variations in auroral luminosity (auroral pulsations) and in magnetospheric plasma/magnetic field data. This event occurred on 10 March 2010 from~13 to 17 UT during an extended southward interplanetary magnetic field and was probably triggered by a slow shock. The auroral pulsations, as measured by the Ultraviolet Imager on board the Polar satellite, were long lasting (~2.5 h), monochromatic (~2.5 mHz), large scale, and appeared in the night sector auroral zone with a latitudinal extent comparable to the latitudinal width of the oval. There was no phase shift between the auroral pulsations observed at different local times, indicating a stationary structure. Particle data from the Defense Meteorological Satellite Program Special Sensor Precipitating Electron and Ion Spectrometer indicate that the pulsations were diffuse originating from the central plasma sheet. During this time, Geotail was in the dawn sector plasma sheet and observed a ULF wave with the same frequency as the auroral pulsations last~35 min. The ULF wave had large radial and compressional components, and the plasma density and total magnetic field were anticorrelated. These two observations strongly suggest that the observed ULF wave was associated with an standing ULF poloidal mode. The wave compressional component may be able to change the loss cone, resulting in periodic auroral precipitating.

Daytime Pc5 Diffuse Auroral Pulsations and Their Association With Outer Magnetospheric ULF Waves

“…Although we have primarily discussed the possible role of compressional Pc5 pulsations on the daytime auroral pulsations, we cannot completely rule out a potential interaction process of energetic electrons with poloidal Pc5 pulsations because THEMIS-D observed the large E φ oscillations. However, we refrain further discussion here, because Liou and Sibeck (2014) and Motoba et al (2015) have already argued the possible contribution of poloidal Pc5 pulsations to the nightside diffuse auroral pulsations.…”

“…In contrast to many examples of periodic auroral arcs which display FLR-related pulsation characteristics, only a few studies reported long-period pulsations in the diffuse aurora (Liou & Sibeck, 2014;Taylor et al, 1989;Yamamoto et al, 1988). Using ground-based all-sky TV and magnetometer data, Yamamoto et al (1988) demonstrated examples of which the diffuse auroral luminosity in the dawn sector was modulated in concert with Pc5 geomagnetic pulsations on the ground.…”

Dawn‐Dusk Auroral Oval Oscillations Associated With High‐Speed Solar Wind

“…Saka et al () reported evidence for a close association between auroral pulsations and a strong poloidal component of the Pc 5 magnetic field oscillations observed on the ground. More recently, Liou and Sibeck () found that some long‐duration, monochromatic Pc5 auroral pulsations are associated with ULF waves at the same frequency observed concurrently in the magnetosphere.…”

“…This type of auroral pulsation is often accompanied by magnetic pulsations. Auroral pulsations have been observed not only from the ground (Yamamoto et al, 1988) but also in space (Liou et al, 2008;Liou & Sibeck, 2014;Liou & Takahashi, 2013). The long-period auroral pulsations are usually tied to discrete auroras (e.g., arcs) (Samson et al, 1996;Xu et al, 1993) and are thought to be associated with field line resonances (Samson et al, 1996).…”

First satellite imaging of auroral pulsations by the Fast Auroral Imager on e‐POP

“…In particular, electrostatic electron cyclotron harmonic and electromagnetic chorus waves have been identified as drivers. Recently, auroral intensity modulations with a much longer period (~400 s) and extended over an extensive region were reported by Liou and Sibeck [].…”