Direct Observations of the Evolution of Polar Cap Ionization Patches

Zhang, Qinghe; Zhang, Beichen; Lockwood, Mike; Hu, Hongqiao; Moen, J.; Ruohoniemi, J. M.; Thomas, E. G.; Zhang, Shun‐Rong; Yang, Huigen; Liu, Ruiyuan; McWilliams, K. A.; Baker, J. B.

doi:10.1126/science.1231487

Cited by 125 publications

(186 citation statements)

References 23 publications

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“…Investigations of density depressions can be regarded as a complementary effort to studies of production and evolution of plasma enhancements such as polar patches [Crowley et al, 1993]. In this sense, the current study complements well the recent experimental studies of polar patches that were enabled by expanding capabilities to image the polar cap using radio and optical techniques [e.g., Hosokawa et al, 2009Hosokawa et al, , 2014Oksavik et al, 2010;Dahlgren et al, 2012b;Moen et al, 2013;Zhang et al, 2013;Burston et al, 2014;Nishimura et al, 2014]. Moreover, the current study also focused on series of propagating density enhancements in the vicinity of density depressions and can therefore be regarded as complementary to both of these broader efforts.…”

Section: Discussionsupporting

confidence: 55%

“…Localized enhancements in plasma density (100-1000 km in extent) known as polar patches have received even more attention than their low-density counterparts [Buchau et al, 1983;Weber et al, 1984;Rodger et al, 1994;Milan et al, 2002;Hosokawa et al, 2009;Dahlgren et al, 2012aDahlgren et al, , 2012bZhang et al, 2013;Burston et al, 2014;Goodwin et al, 2015]. A fundamental problem is what causes the plasma to be chopped into islands and what happens with patches after they have been separated from their source region including further structuring processes [Carlson, 2012].…”

Section: Introductionmentioning

confidence: 99%

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Resolute Bay Incoherent Scatter Radar observations of plasma structures in the vicinity of polar holes

2015

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The Resolute Bay Incoherent Scatter Radar North (RISR‐N) data collected between January 2012 and June 2013 are employed to identify and analyze 14 events with significant plasma density depressions (Ne<4 × 1010 m−3) in the winter polar cap ionosphere. The RISR‐N observations near a magnetic latitude (MLAT) of 85°N refer to the region poleward of the previously identified polar hole‐auroral cavity region 70°–80° MLAT where extremely low densities (down to 2 × 108 m−3 near 300 km in altitude) are found at times. Multipoint observations by RISR‐N are also characterized by multiple series of propagating local density enhancements (plasma structures) both well outside and in the vicinity of polar holes. A superposed epoch analysis of plasma density and convection reveals that the density depressions tend to reach their minimum near the reversal of the meridional convection component. The wavelet analysis of plasma density time series shows that the wave power is enhanced within the depressions and tends to peak near the density minimum. The plasma structures are more elongated at mesoscales (>150 km), with no apparent differences between structure shapes outside and inside low‐density regions. The structure propagation velocity is perpendicular to its elongation direction and consistent with that of the large‐scale plasma convection. The observations indicate that large‐scale density depressions can form under a variety of convection conditions and that plasma structuring processes outside the depressions may be responsible for their partial filling.

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Section: Discussionsupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Resolute Bay Incoherent Scatter Radar observations of plasma structures in the vicinity of polar holes

2015

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“…The high AE index indicates a moderate substorm, which will be associated with the larger energetic particle precipitation which results in poleward and equatorward expansion of the auroral emission structures. IMF (B z ) was southward throughout the BBAE, which causes the existence of active two cell convection pattern across the polar cap (Dungey, 1961;Zhang et al, 2013b). Following Lee et al (2010), positive IMF By causes extension of the aurora oval boundary more poleward at the post-midnight sectors in the northern hemisphere.…”

Section: Bouncing Boundary Auroral Emissions (Bbae)mentioning

confidence: 99%

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

Priyadarshi

Zhang

et al. 2018

Front. Astron. Space Sci.

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Dynamical nightside auroral structures are often observed by the all sky imagers (ASI) at the Chinese Yellow River Station (CYRS) at Ny-Ålesund, 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 (S 4 ) and phase scintillation (σ φ ) 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. S 4 and σ φ have similar levels around the FBAE, while σ φ was much stronger than S 4 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.

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“…Both Carlson (2012) and Zhang et al (2013) have provided analyses of events using, respectively, EISCAT for Ne data and GPS receiver arrays for TEC. The latter dataset is overlaid with SuperDARN convection patterns.…”

Section: Search For Observational Supportmentioning

confidence: 99%

On the convection of ionospheric density features

Boer¹,

Noel²,

St.-Maurice³

2018

Preprint

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Abstract. We investigate whether the boundaries of an ionospheric region of different density than its surroundings will drift relative to the background E × B drift and, if so, how the drift depends on the degree of density enhancement and the altitude.We find analytic solutions for discrete circular features in a 2-D magnetised plasma. The relative drift is proportional to the density difference, which suggests that where density gradients occur they should tend to steepen on one side of a patch while they are weakened on the other. This may have relevance to the morphology of polar ionospheric patches and auroral arcs, since 5 the result is scale-invariant. There is also an altitude dependence which enters through the ion-neutral collision frequency. We discuss how the 2-D analytic result can be applied to the real ionosphere.

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Direct Observations of the Evolution of Polar Cap Ionization Patches

Cited by 125 publications

References 23 publications

Resolute Bay Incoherent Scatter Radar observations of plasma structures in the vicinity of polar holes

Resolute Bay Incoherent Scatter Radar observations of plasma structures in the vicinity of polar holes

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

On the convection of ionospheric density features

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