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

Makarevich, R. A.; Lamarche, Leslie; Nicolls, M. J.

doi:10.1002/2015ja021443

Cited by 11 publications

(14 citation statements)

References 41 publications

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“…This is consistent with the Doppler velocity measured by MCM within the patch (dark blue colors). Similar consistency between the patch drift and plasma convection velocities was observed by Bristow et al [] using MCM observations and, more recently, by Makarevich et al [] using direct observations of 2‐D convection velocity and density enhancements by RISR‐N in the northern polar cap. This implies that polar patches tend to move with the background convection, at least deep within the polar cap.…”

Section: Discussionsupporting

confidence: 87%

Solar control of F region radar backscatter: Further insights from observations in the southern polar cap

Lamarche

Makarevich

2015

JGR Space Physics

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The role of solar wind and illumination in production of small‐scale F region plasma irregularities is investigated using a 4 year data set collected by the Super Dual Auroral Radar Network (SuperDARN) facility at the McMurdo station, Antarctica (MCM). Statistical analysis of ionospheric echoes detected by MCM shows that radar backscatter from the polar F region occurs in wide and persistent bands in range that exhibit systematic changes with local time, season, and solar cycle. It is demonstrated that all variations considered together form a distinct pattern. A comparison with the F region model densities and ray tracing simulations shows that this pattern is largely controlled by the F region solar‐produced ionization during the day. During the night, however, MCM observations reveal a significant additional source of plasma density in the polar cap as compared with the model. An example of conjugate radar observations is presented that supports the idea of polar patches being an additional source of ionization on the nightside. Echo occurrence exhibits a clear peak near the solar terminator, which suggests that small‐scale irregularities form in turbulent cascade from large scales. Further, echo occurrence is enhanced for particular interplanetary magnetic field (IMF) orientations during the night. Observations indicate that solar illumination control of irregularity production is strong and not restricted to the nightside. Indirect solar wind control is also exerted by the IMF‐dependent convection pattern, since the gradient‐drift instability favors certain orientations between the plasma density gradients and convection velocity.

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Section: Discussionsupporting

confidence: 87%

Solar control of F region radar backscatter: Further insights from observations in the southern polar cap

Lamarche

Makarevich

2015

JGR Space Physics

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“…Particle precipitation is another process that can produce plasma enhancements (e.g., Oksavik et al, ) and change the background electron density within the structures brought to the polar cap by convection (Goodwin et al, ; Makarevich et al, ). It is common to divide the precipitation events in the polar ionosphere into three types: polar rain, polar showers, and polar squalls.…”

Section: Discussionmentioning

confidence: 99%

Statistical Analysis of the Electron Density Gradients in the Polar Cap F Region Using the Resolute Bay Incoherent Scatter Radar North

Forsythe

Makarevich

2018

JGR Space Physics

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Electron density gradients in the polar F region ionosphere are essential for the structuring processes through the gradient-drift instability (GDI). The information about the typical strength of gradients is important for the theoretical studies and modeling of the GDI waves, but rarely available because of significant experimental challenges in evaluation of the gradients, particularly at small scales and in 3-D. In this study, multipoint density measurements of the Resolute Bay Incoherent Scatter Radar North working in a special high-spatial-resolution mode are employed to address the above question in a systematical manner. The 3-D gradient vectors as well as their horizontal and vertical components are estimated for the first time and analyzed statistically utilizing a large Resolute Bay Incoherent Scatter Radar North data set. Statistical analysis of the gradient strength shows that the vertical components of the gradient strength vectors are larger than their horizontal counterparts, especially in the lower portion of the F region (below 220 km). The sharpness of the density gradients reveals a significant increase around magnetic midnight due to a decreased effect of the solar smoothing. Further, sharp density gradients occur during magnetically quiet times, possibly because of the presence of the polar holes and reduced plasma precipitation. The peak of occurrence for the horizontal components of the gradient strength vectors occurs at 0.5 × 10 −6 m −1 , whereas 15.5% of horizontal gradients exceeds 10 −5 m −1 . These gradients are strong enough for a direct generation of GDI waves at decameter scale (i.e. in linear regime), which implies that nonlinear turbulent cascade is not necessarily required for at least some GDI waves.

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“…The density criterion in this study is stricter in comparison to other studies. For example, Makarevich et al (2015) investigated events where 1% of RISR-N measurements at 300 km had N e < 4 × 10 10 m −3 and at least 10% of measurements with N e < 10 11 m −3 . Additionally, the study of Crowley et al (1993) indicated the polar hole in the Qanaq digisonde N m F 2 observations as a drop from 4 × 10 11 m −3 to 10 11 m −3 , which is not as deep as what was considered here.…”

Section: Observationsmentioning

confidence: 99%

Multi‐Instrument Investigation of the Polar Holes

2021

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During the solar minimum the F-region plasma density can become extremely low, and in some exceptional cases the F-layer can completely disappear. These F-region density depletions are particularly deep during geomagnetically quiet nights, when slow plasma convection creates polar holes, extending 100-1000 km in size, where the electron density is several orders of magnitude lower than the background values. Polar holes are believed to be formed during the periods of the very slow anti-sunward convection, when the plasma is trapped just poleward of the auroral oval in the absence of any ionization sources. At the same time, fast convection with rapid vertical plasma transport has also been associated with the polar hole formation. Combining the electron density measurements from the Resolute Bay Incoherent Scatter Radar (RISR) and Poker Flat ISR (PFISR), the state of art variational data assimilation tool Ionospheric Data Assimilation Four-Dimensional (IDA4D), and the convection data from the Super Dual Auroral Radar Network (SuperDARN) array, the polar hole formation and evolution are experimentally investigated. The F-region plasma is traced back in time prior to the polar hole formation to analyze the favorable conditions for the formation of the polar holes. The role of plasma convection in the formation of the polar holes is experimentally investigated. The results show that the polar holes can be formed in the twilight condition and without being trapped in the closed convection loops. The formation of the polar holes were equally possible during slow and strong convection flows, predominantly with a standard two-cell convection configuration. FORSYTHE ET AL.

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

Cited by 11 publications

References 41 publications

Solar control of F region radar backscatter: Further insights from observations in the southern polar cap

Solar control of F region radar backscatter: Further insights from observations in the southern polar cap

Statistical Analysis of the Electron Density Gradients in the Polar Cap F Region Using the Resolute Bay Incoherent Scatter Radar North

Multi‐Instrument Investigation of the Polar Holes

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