Statistical Characteristics of Polar Cap Patches Observed by RISR‐C

Ren, Jiaen; Zou, Shasha; Gillies, R. G.; Donovan, E.; Varney, R. H.

doi:10.1029/2018ja025621

Cited by 23 publications

(31 citation statements)

References 38 publications

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“…Note that this value might increase to 30% or less if a 60‐min sliding window de‐trending method is utilized (not shown here). Nevertheless, these amplitudes remain substantially smaller than typical patch amplitudes around 200% (Ren et al, ).…”

Section: Resultsmentioning

confidence: 72%

“…(2) The scale size of zonal wave fronts was persistently much larger than that of plasma structures such as polar patches. Nevertheless, these amplitudes remain substantially smaller than typical patch amplitudes around 200% (Ren et al, 2018). The wave fronts of these zonal structures formed almost continuous vertical lines in the keogram and were very well organized periodically, suggesting significant spatial coherence of the structures.…”

Section: High Latitudesmentioning

confidence: 79%

“…Note that this value might increase to 30% or less if a 60-min sliding window de-trending method is utilized (not shown here). Nevertheless, these amplitudes remain substantially smaller than typical patch amplitudes around 200% (Ren et al, 2018). To further demonstrate transpolar day-to-night meridional propagation of TIDs at high latitudes, we provide a few sets of keograms organized by pairs of local times (rather than longitudes in Figure 9).…”

Section: High Latitudesmentioning

confidence: 99%

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

et al. 2019

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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...

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Section: Resultsmentioning

confidence: 72%

Section: High Latitudesmentioning

confidence: 79%

Section: High Latitudesmentioning

confidence: 99%

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

et al. 2019

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“…Despite this, an automated method for the detection of patches in ISR data has yet to be developed, even though such algorithms have been created for other instruments and data sets (which we will discuss in the next section). (Authors note: Unbeknownst to the authors of this article, Ren et al () submitted a manuscript introducing a patch detection algorithm for the RISR‐C radar less than a month after the current article was first submitted.) The principal goals of the work reported here are (1) to remedy this ISR shortcoming by establishing an algorithm that effectively identifies patches within the field‐of‐view (FOV) of the RISR‐N and (2) to show first results emerging from this procedure.…”

Section: Introductionmentioning

confidence: 99%

A Polar‐Cap Patch Detection Algorithm for the Advanced Modular Incoherent Scatter Radar System

Perry

St.-Maurice

2018

Radio Science

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We introduce an algorithm to detect polar-cap patches in an Advanced Modular Incoherent Scatter Radar data set, using the Resolute Bay Incoherent Scatter Radar-North. Patches are detected by comparing plasma density (n e ) measurements along each radar beam to a 30-min running average of the median n e within the field-of-view. The algorithm is tested and shown to be an effective tool for polar-cap patch studies. It is then used to conduct a survey of patches over Resolute Bay for two separate periods of time centered on March and December of 2010. The survey shows that polar-cap patches are almost always present in both sunlit and nighttime conditions. However, the population is subdued during the day. The patch densities are found to vary by as much as an order of magnitude throughout the day. Their ion temperature is relatively constant, only varying by 100 K between the sunlit and nighttime conditions. By contrast, their electron temperature is very sensitive to the solar zenith angle and changes dramatically around sunrise. Plain Language SummaryWe introduce an algorithm to detect polar-cap patches in a radar data set. Patches are large-scale F region plasma density enhancements, positive plasma density perturbations above the background plasma density, and are typically observed at high latitudes. The patches are detected by comparing plasma density measurements at different points within the radar's field-of-view to a 30-min running average of the median plasma density within the field-of-view. The algorithm is tested and validated and used to analyze data collected by the Resolute Bay Incoherent Scatter Radar-North over several days in March and December 2010. Our analysis reveals that the density of detected patches varies by as much as an order of magnitude throughout the day, and their electron temperature is very sensitive to whether or not the patch is sunlit and changes dramatically around sunrise.

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“…While earlier such studies were focusing on the patch density (e.g., Coley & Heelis, 1998;David et al, 2016;Jin et al, 2019;Moen et al, 2007Moen et al, , 2015Ren et al, 2018;Sojka et al, 1994). While earlier such studies were focusing on the patch density (e.g., Coley & Heelis, 1998;David et al, 2016;Jin et al, 2019;Moen et al, 2007Moen et al, , 2015Ren et al, 2018;Sojka et al, 1994).…”

Section: 1029/2019ja027020mentioning

confidence: 99%

Polar Ionospheric Large‐Scale Structures and Dynamics Revealed by TEC Keogram Extracted From TEC Maps

Wang

Zhang

et al. 2020

JGR Space Physics

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A method named total electron content (TEC) keogram is introduced for surveying the large-scale irregularities continuously in the polar ionosphere. The TEC keogram is developed from a movie of TEC maps along various meridian lines from the dayside to the nightside across the magnetic pole, trying to identify and track several types of ionospheric structures. Through two examples, a clear train of polar cap patches are identified from TEC keogram and confirmed by SuperDARN radar observations. The motion speed of these patches estimated from this tool agrees with SuperDARN radar measurements. Then, the motions of patches relative to the background convection through the whole polar cap are statistically studied for the first time. Moreover, the occurrence dependence of fully tracked patches on months, UT hours, and interplanetary magnetic field conditions is generally consistent with previous reports. These results suggest that the TEC keogram offers a power tool for continuous monitoring and studying of large-scale plasma irregularities in the polar ionosphere.

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Statistical Characteristics of Polar Cap Patches Observed by RISR‐C

Cited by 23 publications

References 38 publications

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

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

A Polar‐Cap Patch Detection Algorithm for the Advanced Modular Incoherent Scatter Radar System

Polar Ionospheric Large‐Scale Structures and Dynamics Revealed by TEC Keogram Extracted From TEC Maps

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