Airglow Patches in the Polar Cap Region: A Review

Hosokawa, K.; Zou, Ying; Nishimura, Y.

doi:10.1007/s11214-019-0616-8

Cited by 8 publications

(11 citation statements)

References 78 publications

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“…Polar cap patches are known as regions in the polar cap F region ionosphere where the electron density locally increases at least twice as much as the background value in the surrounding area (Crowley, 1996 and references therein). Patches have so far been observed using ground‐based observation techniques such as ionosondes (Weber et al., 1984), incoherent scatter radars (Pedersen et al., 2000), coherent scatter radars (Milan et al., 2002), all‐sky airglow imagers (Hosokawa et al., 2019 and references therein), and GPS‐TEC observations (Zhang et al., 2013). In recent years, in situ plasma density measurements onboard low‐altitude satellites have also been insensitively used to investigate the statistical characteristics of polar cap patches.…”

Section: Introductionmentioning

confidence: 99%

Occurrence Distribution of Polar Cap Patches: Dependences on UT, Season and Hemisphere

et al. 2021

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Polar cap patches are islands of enhanced electron density in the polar cap F region ionosphere, which sometimes affect the propagation of trans‐ionospheric radio waves. Considering the intake of daytime sunlit plasma by the high‐latitude convection as the primary cause of patches, the spatial overlap between the convection and the daytime sunlit plasma should be one of the critical factors controlling the generation of patches. To confirm this hypothesis, we statistically investigated the UT and seasonal distributions of patch occurrence frequency in both the hemispheres by using in situ plasma density data from the Swarm satellite. As a result, it was found that the occurrence distribution of patches is a complex function of UT, season and hemisphere, but it can be mostly interpreted by the spatial overlap between the high‐latitude convection and the solar terminator. This suggests that polar cap patches are not necessarily phenomena that occur only during winter months. That is, patches can often be observed even in periods away from the winter solstice if the location of solar terminator in the magnetic coordinate system is appropriate for the generation of patches. For example, in the southern hemisphere, where the offset between the geographic and magnetic poles is larger than that in the northern hemisphere, the highest patch occurrence rate is obtained around the equinoctial periods. These results indicate that it is needed to take these dependences into account when we discuss and predict the space weather impacts of patches on the trans‐ionospheric radio propagation.

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Section: Introductionmentioning

confidence: 99%

Occurrence Distribution of Polar Cap Patches: Dependences on UT, Season and Hemisphere

et al. 2021

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“…When dayside reconnection occurs, flow channels are 10.1029/2020JA028359 thought to be an important feature for the injection of corotating plasma from the subauroral plasma reservoir into transpolar flow (Carlson et al, 2006) and in the structuring of plasma within polar cap patches in their early formation stages (Carlson, 2012). Dayside flow channels have also been found to be collocated with airglow patches, forming under By-dominated dayside reconnection and potentially transporting the airglow patches across the polar cap and into the nightside auroral zone (Hosokawa et al, 2019;Nishimura et al, 2014). Flow channels have been observed deep within the polar cap on the dawn/dusk flanks and on the nightside due to magnetotail reconnection and substorms (Nishimura et al, 2010;Oksavik et al, 2010;Sandholt & Farrugia, 2009).…”

Section: Introductionmentioning

confidence: 99%

A Statistical Study of Polar Cap Flow Channels and Their IMF By Dependence

et al. 2020

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An algorithm to detect high-speed ionospheric flow channels (FCs) in the polar cap was applied to data from the Longyearbyen radar of the Super Dual Auroral Radar Network. The Longyearbyen radar is at high latitude (78.2 • N, 16.0 • E geographic coordinates) and points northeast; therefore, it is in an ideal position for measuring zonal flows in the polar cap. The algorithm detected 998 events in the dayside polar cap region over 2 years of observations. The detected FCs typically were between 200 and 300 km latitudinal width, 1.1-1.3 km s −1 peak velocity, and 3 min in duration. The FC location shows an interplanetary magnetic field (IMF) By dependency, moving dawnward/duskward for a +By/−By. The FC monthly occurrence shows a bimodal distribution with peaks around the spring and autumn equinoxes, likely due to increased coupling between the solar wind-magnetosphere-ionosphere system at these times. The highest peak velocities show an absence of broad FC widths, suggesting that as the flow speed increases in the polar cap, the channels become more localized and narrow.

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“…Each bin is 0.05° MLAT wide along the y ‐axis, and we have calculated the third quartile in each bin to exclude background emissions. Since the patches are much weaker in intensity than the throat auroras (Hosokawa et al., 2019), we changed the 630.0 nm colorbar between 78° and 80° MLAT (approximate location of patches). The throat auroras and patches are further highlighted by magenta and dark green arrows, respectively.…”

Section: Observations Resultsmentioning

confidence: 99%

Do the Throat Auroras Create Polar Cap Patches?

Zhang

Oksavik

et al. 2023

Geophysical Research Letters

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Throat auroras and polar cap patches are common phenomena in the polar ionosphere resulting from solar wind-magnetosphere-ionosphere coupling. The throat aurora is a discrete aurora that is associated with localized magnetopause indentations (Han, 2019). It is usually located equatorward of the cusp aurora oval near magnetic noon, oriented in the south-north direction (Han et al., 2015) and is more frequently observed under radial interplanetary magnetic field (IMF, Bx-dominated conditions) (e.g., Han et al., 2017;Rodriguez et al., 2012). Han et al. (2016) indicated that throat aurora is an ionospheric feature in which magnetosheath particles enter the magnetosphere along open magnetic field lines, based on data from ground-based all-sky imagers (ASIs) and Magnetospheric Multiscale (MMS) satellites. Throat auroras are also observed to be accompanied by Joule heating and ion upflows, based on data from a European Incoherent Scatter (EISCAT) radar experiment (Han et al., 2019), which supports throat aurora being associated with magnetopause reconnection.The polar cap patch is another common phenomenon in the dayside ionosphere polar regions. It is also associated with transient dayside reconnection (e.g., Carlson et al., 2004;Lockwood & Carlson, 1992;Zhang et al., 2011Zhang et al., , 2013. A patch is an island of high-density F region ionospheric plasma with a typical size of

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Airglow Patches in the Polar Cap Region: A Review

Cited by 8 publications

References 78 publications

Occurrence Distribution of Polar Cap Patches: Dependences on UT, Season and Hemisphere

Occurrence Distribution of Polar Cap Patches: Dependences on UT, Season and Hemisphere

A Statistical Study of Polar Cap Flow Channels and Their IMF By Dependence

Do the Throat Auroras Create Polar Cap Patches?

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