Simultaneous ground-based optical and SuperDARN observations of the shock aurora at MLT noon

Abstract

Using ground-based high temporal and spatial optical aurora observations, we investigated one fortuitous event to illustrate the direct responses of the fine structure auroral emission to interplanetary shock on 7 January 2005. During the shock impact to the magnetosphere, the Chinese Arctic Yellow River Station (YRS) equipped with all-sky imagers (ASIs) was situated at the magnetic local noon region (~1210 MLT) in the Northern Hemisphere, while the SuperDARN CUTLASS Finland HF radar covering the field of view (FOV) of the ASIs at YRS had fine ionospheric plasma convection measurement. We observed that an intensified red aurora manifesting as a discrete emission band at a higher latitude responds to the shock impact gradually, which results in a distinct broadening of the dayside auroral oval due to the equatorward shifting of its lower latitude boundary after the shock arrival. In contrast, the green diffuse aurora, manifesting as a relatively uniform luminosity structure, reacts immediately to the shock compression, displaying prompt appearance in the southern edge of the FOV and subsequent poleward propagation of its higher latitude boundary. Simultaneously, the CUTLASS Finland radar monitored enhanced backscatter echo power and increased echo number, which coincided with intensified discrete aurora in approximately the same latitudinal region. Doppler velocity measurement showed moving ionospheric irregularities with generally enhanced line-of-sight (LOS) speed, but with prominent sunward flow in the polar cap and antisunward flow in both the eastern and western regions. The SuperDARN global ionospheric convection pattern clearly presented a large-scale plasma flow divided in four circulation cells, with two reversed flow cells nested in the noon sector of the polar cap. These direct observations strongly suggest that the prompt shock compression intensified the wave-particle interaction in the inner magnetosphere and enhanced the lobe magnetic reconnection rate at magnetospheric high latitude.

Geomagnetic and ionospheric response to the interplanetary shock on January 24, 2012

“…At this time, a very strong proton arc forms, and at ~1519 UT, it completely subsides in the equatorward portion of the oval (between 130° and 165° scan angles). Therefore, our observations do not coincide completely with the previous observations (Motoba et al 2009;Liu et al 2015). We do observe a two-step development with weak poleward moving arcs, which after a few minutes stop their poleward movement and increase substantially in intensity.…”

“…The red discrete aurora is dominated by soft electron precipitation (0.1-1 keV), which corresponds to injections of magnetosheath plasma. Two types of responses of the dayside/ morning aurora to an IP shock were observed: (1) a "fast" (in ~1 min) onset of the green diffuse aurora manifested as a relatively uniform luminosity structure in the equatorward edge of the oval and (2) a "slow" (with a delay of ~4-5 min) substantial enhancement of a discrete red emission band at a higher latitude (Motoba et al 2009;Liu et al 2015). This two-step development of the postnoon shock aurora supposes the operation of several mechanisms of auroral intensification.…”

Dayside Auroral Observation Resulting From a Rapid Localized Compression of the Earth's Magnetic Field

“…Zhou et al (2009) documented a factor of 2 intensification of the aurora seen by an all‐sky imager located in Svalbard, Norway, that followed the arrival of an interplanetary shock by 5 min. Liu et al (2015) documented intensified discrete red aurora and broadening of the auroral oval in ground‐based optical aurora observations in response to an interplanetary shock. They suggest that shocks intensify interactions in the inner magnetosphere and enhance the lobe magnetic reconnection rate.…”

The Behaviors of Ionospheric Scintillations Around Different Types of Nightside Auroral Boundaries Seen at the Chinese Yellow River Station, Svalbard

“…Their brightening and diming is the signature of the open and closed field lines respectively. Many other important recent research investigations (e.g., Liu et al, 2015;Lyons et al, 2015;Prikryl et al, 2015;van der Meeren et al, 2015;Hosokawa et al, 2016;Jin et al, 2017 etc. ) related with the auroral emission have been successfully carried out suing the SuperDARN radar network.…”

“…Further, recent research studies related to the auroral emission and the polar ionospheric (e.g., Crowley et al, 2000;Zhang et al, 2013aZhang et al, , 2015Jin et al, 2015Jin et al, , 2016Jin et al, , 2017Liu et al, 2015;Lyons et al, 2015;Oksavik et al, 2015;Prikryl et al, 2015;van der Meeren et al, 2015;Hosokawa et al, 2016;Baddeley et al, 2017;Chen et al, 2017 and many others) have covered many important aspects of magnetosphere-ionosphere-thermosphere coupling, such as nightside patch related aurora and poleward edge brightening of the nightside auroral oval; nightside auroral blobs and their associated scintillations; throat aurora as the precursor of PMAFs; equatorward driven auroral arcs due to the ULF waves and their energy dissipation caused due to joule/ion frictional heating etc. Still the long time duration (3-5 h) auroral emissions neither were studied nor characterized based on their boundary movement.…”