Polar cap patch segmentation of the tongue of ionization in the morning convection cell

Zhang, Q. H.; Zhang, B. C.; Moen, J.; Lockwood, Mike; McCrea, I. W.; Yang, Huigen; Hu, Hongqiao; Liu, R. Y.; Zhang, S. R.; Lester, M.

doi:10.1002/grl.50616

Cited by 58 publications

(88 citation statements)

References 14 publications

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“…As an example, plasma originating at midlatitudes can be transported to high latitudes and into the polar cap in a form of a tongue of ionization which greatly enhances the plasma density in the polar cap, cusp and auroral zone (e.g., Foster et al, 2005). Tongues of ionization can also be segmented into 100-1000 km sized islands of enhanced electron density, called polar cap patches (e.g., Lockwood and Carlson, 1992;Zhang et al, 2013). The patches are transported over the polar cap following the convection pattern.…”

Section: Introductionmentioning

confidence: 99%

An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

et al. 2016

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Abstract. Incoherent scatter radar measurements are an important source for studies of ionospheric plasma parameters. In this paper the EISCAT Svalbard radar (ESR) long-term database is used to evaluate the International Reference Ionosphere (IRI) model. The ESR started operations in 1996, and the accumulated database up to 2012 thus covers 16 years, giving an overview of the ionosphere in the polar cap and cusp during more than one solar cycle. Data from ESR can be used to obtain information about primary plasma parameters: electron density, electron and ion temperature, and line-ofsight plasma velocity from an altitude of about 50 and up to 1600 km. Monthly averages of electron density and temperature and ion temperature and composition are also provided by the IRI model from an altitude of 50 to 2000 km. We have compared electron density data obtained from the ESR with the predicted electron density from the IRI-2016 model. Our results show that the IRI model in general fits the ESR data well around the F2 peak height. However, the model seems to underestimate the electron density at lower altitudes, particularly during winter months. During solar minimum the model is also less accurate at higher altitudes. The purpose of this study is to validate the IRI model at polar latitudes.

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Section: Introductionmentioning

confidence: 99%

An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

et al. 2016

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“…Recently, Goodwin et al (2015) used SWARM data to document the intake of solar-EUV plasma through fast flow channels. Those fast flows are also associated with poleward moving auroral forms (PMAFs), which are considered to be an ionospheric signature of localized dayside magnetic reconnection and flux transfer events (FTEs) (Moen et al 1995;Provan et al 1998McWilliams et al 2000;Milan et al 2000;Sandholt and Farrugia 2003;Lockwood et al 2005;Carlson et al 2006;Zhang et al 2011Zhang et al , 2013b. PMAFs initiate near the poleward boundary of the dayside auroral oval and then propagate poleward before fading away (Lorentzen et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP

et al. 2016

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Recent imager and radar observations in the nightside polar cap have shown evidence that polar cap patches are associated with localized flow channels. To understand how flow channels propagate from the dayside auroral oval into the polar cap, we use an all-sky imager in Antarctica and DMSP (F13, F15, F16, F17 and F18) to determine properties of density and flows associated with dayside polar cap patches. We identified 50 conjunction events during the southern winter seasons of 2007-2011. In a majority (45) of events, longitudinally narrow flow enhancements directed anti-sunward are found to be collocated with the patches, have velocities (up to a few km/s) substantially larger than the large-scale background flows (~500 m/s) and have widths comparable to patch widths (~400 km). While the patches start with poleward moving auroral forms (PMAFs) as expected, many PMAFs propagate azimuthally away from the noon over a few hours of MLT, resulting in formation of polar cap patches quite far away from the noon, as early as ~6 MLT. The MLT separation from the noon is found to be proportional to the IMF |By|. Fast polar cap flows of >~1500 m/s are predominantly seen during large IMF |By| and small |Bz|. The presence of fast, anti-sunward flow channels associated with the polar cap patches suggests that the flow channels form in the dayside auroral oval through transient reconnection and can be the source of flow channels propagating into the polar cap.

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“…(Zhang et al, 2017), but, if they appear only in 630.0 nm keogram ( Figure 1B), so called polar cap patches (e.g., Sato et al, 1998;Zhang et al, 2011Zhang et al, , 2013aZhang et al, ,b, 2016Hosokawa et al, 2012). Whenever, these structures meet the GNSS signals, they give rise to moderate amplitude and phase scintillation (Hosokawa et al, 2014), especially for polar cap hot patches (Zhang et al, 2017).…”

Section: Fixed Boundary Auroral Emissions (Fbae)mentioning

confidence: 98%

“…PMAFs are the poleward moving auroral forms and they cause severe degradation on the GNSS signals by causing scintillation and the loss of lock between satellite signal and the GNSS ground based receiver . Crowley et al (2000) and Zhang et al (2013aZhang et al ( , 2015 mentioned that nighttime aurora are occasionally due to the dayside high plasma density, which enters the nightside auroral oval and generate aurora thereafter, these high density plasma returns back to the dayside region. Inside the nightime auroral oval if the polarcap patches enters and produce aurora, the strongest scintillation is mostly found at the poleward edge of the nighttime auroral oval .…”

Section: Introductionmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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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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Polar cap patch segmentation of the tongue of ionization in the morning convection cell

Cited by 58 publications

References 14 publications

An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP

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

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