Abstract
Dynamical nightside auroral structures are often observed by the all sky imagers (ASI) at the Chinese Yellow River Station (CYRS) at Ny-Alesund, Svalbard, located in the polar cap near poleward edge of the nightside auroral oval. The boundaries of the nightside auroral oval are stable during quiet geomagnetic conditions, while they often expand poleward and pass through the overhead area of CYRS during the substorm expansion phase. The motions of these boundaries often give rise to strong disturbances of satellite navigations and communications. Two cases of these auroral boundary motions have been introduced to investigate their associated ionospheric scintillations: one is Fixed Boundary Auroral Emissions (FBAE) with stable and fixed auroral boundaries, and another is Bouncing Boundary Auroral Emissions (BBAE) with dynamical and largely expanding auroral boundaries. Our observations show that the auroral boundaries, identified from the sharp gradient of the auroral emission intensity from the ASI images, were clearly associated with ionospheric scintillations observed by Global Navigation Satellite System (GNSS) scintillation receiver at the CYRS. However, amplitude scintillation (S4) and phase scintillation (σφ) respond in an entirely different way in these two cases due to the different generation mechanism as well as different IMF (Interplanetary Magnetic Field) condition. S4 and σφ have similar levels around the FBAE, while σφ was much stronger than S4 around BBAE. The BBAE were associated with stronger particle precipitation during the substorm expansion phase. IU/IL, appeared to be a good indicator of the poleward moving auroral structures during the BBAE as well as FBAE.
Highlights
The widely recognized threat to the trans-ionospheric radio wave communication and ranging is the presence of ionospheric irregularities in their signal path, which give rise to ionospheric scintillation and degrades the signal quality (Yeh and Liu, 1982; Bhattacharyya et al, 1992; Basu and Basu, 1993; Yeh and Wernik, 1993; Wernik et al, 2004; Kintner et al, 2007; Priyadarshi, 2015)
Our observations show that the auroral boundaries, identified from the sharp gradient of the auroral emission intensity from the all sky imagers (ASI) images, were clearly associated with ionospheric scintillations observed by Global Navigation Satellite System (GNSS) scintillation receiver at the Chinese Yellow River Station (CYRS)
The scintillation generated in the cusp is associated with the ionospheric irregularity perturbation in the cusp region as well as cusp region particle precipitation, whereas, nighttime auroral oval scintillations are associated with the nightside energetic particle precipitation giving rise to auroral emissions (Prikryl et al, 2010, 2011, 2014; Jiao et al, 2013; Kinrade et al, 2013; Hosokawa et al, 2014; Jin et al, 2014 and references therein)
Summary
The widely recognized threat to the trans-ionospheric radio wave communication and ranging is the presence of ionospheric irregularities in their signal path, which give rise to ionospheric scintillation and degrades the signal quality (Yeh and Liu, 1982; Bhattacharyya et al, 1992; Basu and Basu, 1993; Yeh and Wernik, 1993; Wernik et al, 2004; Kintner et al, 2007; Priyadarshi, 2015). Recent research studies related to the auroral emission and the polar ionospheric (e.g., Crowley et al, 2000; Zhang et al, 2013a, 2015; Jin et al, 2015, 2016, 2017; Liu 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. The section will introduce two types of auroral emissions and discuss the amplitude and phase scintillation variations during these auroral emissions
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