Day‐night coupling by a localized flow channel visualized by polar cap patch propagation

Nishimura, Y.; Lyons, L. R.; Zou, Ying; Oksavik, K.; Moen, J.; Clausen, L. B. N.; Donovan, E.; Angelopoulos, V.; Shiokawa, K.; Ruohoniemi, J. M.; Нишитани, Н.; McWilliams, K. A.; Lester, M.

doi:10.1002/2014gl060301

Cited by 68 publications

(84 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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: 63%

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

2015

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionsupporting

confidence: 63%

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

2015

View full text Add to dashboard Cite

show abstract

“…It seems reasonable to ascribe the TID excitation to the cusp region heating processes during the storm, and storm time cusp or high-latitude heating could have been more efficient in exciting poleward TIDs than the substorm related auroral heating during this 8 September 2017 event. Dayside auroral intensification structures can subsequently move poleward as "poleward moving auroral forms" (PMAF, Nishimura et al, 2014). These structures were generally accompanied by very intense small-scale field-aligned current filaments, which may lead to significant Joule heating to the ionosphere-thermosphere system.…”

Section: High Latitudesmentioning

confidence: 99%

Subauroral and Polar Traveling Ionospheric Disturbances During the 7–9 September 2017 Storms

et al. 2019

View full text Add to dashboard Cite

This study provides new scenarios for storm time traveling ionospheric disturbance excitation and subsequent propagation at subauroral and polar latitudes. We used ground-based total electron content observations from Global Navigation Satellite System receivers combined with wide field, subauroral ionospheric plasma parameters measured with the Millstone Hill Incoherent Scatter Radar during strong September 2017 geospace storms. Observations provide the first evidence of significant influences on traveling ionospheric disturbance (TID) propagation and excitation caused by the presence of large subauroral polarization stream flow channels. Simultaneous large-and medium-scale TIDs evolved during the event in a broad subauroral and midlatitude area near dusk. Similar concurrent TIDs occurred near dawn sectors as well during a period of sustained southward Bz. Medium-scale TIDs at subauroral and midlatitudes had wave fronts aligned northwest-southeast near dusk, and northeast-southwest near dawn. These wave fronts were highly correlated with the direction of storm time large zonal plasma drift enhancements at these latitudes. At high latitudes, unexpected, predominant, and persistent storm time TIDs were identified with 2000+ km zonal wave fronts and 15% total electron content perturbation amplitudes, moving in transpolar propagation pathways from the dayside into the nightside. This propagation direction in the polar region was opposite to the normal assumption that TIDs originated in the nightside auroral region. Results suggest that significant dayside sources, such as cusp regions, can be efficient in generating transpolar TIDs during geospace storm intervals.Plain Language Summary This paper reports several new findings on the traveling ionospheric disturbances (TIDs) excited during geospace storms in 7-8 September 2017. Storm time TIDs provide pathway for momentum and energy dispersion from the solar wind-magnetosphere system to various components of the global ionosphere and thermosphere. Storm time large-scale TIDs (LSTIDs) have been identified by many studies as being initiated generally in the auroral zone where significant heating is injected, with subsequent propagation away from the source: equatorward into lower latitudes and poleward into high latitudes. Our study indicates that, during equatorward propagation, LSTIDs can encounter strong dynamic forcing at subauroral latitudes in the zonal direction. This westward velocity forcing is provided by a SAPS (subauroral polarization stream) channel and furthermore appears to be associated with the developing of medium-scale TIDs (MSTIDs). Thus, this paper provides the first causal link between these TIDs and SAPS flow channels. Concurrent LSTIDs and MSTIDs existed during the September storm in not only near dusk but also dawn sectors. In the polar cap region, conventionally anticipated poleward propagation away from the auroral zone was unexpectedly weak. In contrast, an opposite sense of transpolar propagation from the dayside into the nightside (i.e., eq...

show abstract

“…The similarities between mesoscale flow channels in the dayside cusp and within the nightside polar cap, as well as the patch propagation from the dayside to nightside polar cap, suggest that mesoscale fast flows in the dayside oval propagate deep into the polar cap (Wilder et al 2012 and references therein). In fact, a recent case study using airglow patch and radar flow observations by Nishimura et al (2014) showed a nearly continuous sequence from a dayside PMAF to nightside PBIs, across the polar cap, associated with mesoscale fast flows.…”

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

View full text Add to dashboard Cite

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.

show abstract

Day‐night coupling by a localized flow channel visualized by polar cap patch propagation

Cited by 68 publications

References 34 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

Subauroral and Polar Traveling Ionospheric Disturbances During the 7–9 September 2017 Storms

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

Contact Info

Product

Resources

About