Mesoscale Plasma Convection Perturbations in the High‐Latitude Ionosphere

Chen, Yun‐Ju; Heelis, R. A.

doi:10.1029/2018ja025716

Cited by 10 publications

(21 citation statements)

References 40 publications

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“…It is worth noting that the satellite measurement involves both spatial and temporal variations. However, if it is assumed that structures the satellite encounters are stationary for a short period (~1–2 min), the time series data from the satellite can be converted to spatial data by using the speed of the satellite (Chen & Heelis, ). Since DE‐2 travels 500 km in ~63 s, we believe that most of the variabilities extracted by the 500‐km moving window are spatial variability below 500 km.…”

Section: Resultsmentioning

confidence: 99%

Small‐Scale and Mesoscale Variabilities in the Electric Field and Particle Precipitation and Their Impacts on Joule Heating

et al. 2018

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In this study, the electric field and the particle precipitation at different spatial scale sizes have been investigated by utilizing the Dynamic Explorer 2 satellite data set, focusing on conditions of moderately strong southward interplanetary magnetic field. Dynamic Explorer 2 data from the period between 1981 and 1983, from all universal times, seasons, and both hemispheres, have been processed and binned over geomagnetic latitude and local time. It is found that, as compared with the large-scale (>500 km) average electric field and particle precipitation, the variabilities (i.e., departures from the large-scale average) of electric field and particle precipitation are not negligible. Moreover, the electric field variability tends to be anticorrelated with the particle precipitation variability in the auroral regions on small scale and mesoscale (<500 km). The impacts associated with the small-scale and mesoscale electric field and particle precipitation variabilities on Joule heating have also been addressed in this study by using the Global Ionosphere and Thermosphere Model. It is found that although Joule heating can be significantly enhanced by the small-scale and mesoscale electric field variabilities (~27% globally), the corresponding change in the particle precipitation tends to depress such enhancement (À5% globally), which is not negligible on the dusk side (up to À17.5% locally). It is the first time that the correlation between electric field and particle precipitation variabilities on small scale and mesoscale has been quantified. Furthermore, the impact on Joule heating associated with the correlation between the small-scale and mesoscale electric field and particle precipitation variabilities has been evaluated unprecedentedly in a general circulation model. Plain Language SummaryAt high latitudes, the electromagnetic energy from the magnetosphere dissipates into Earth's upper atmosphere, leading to both local and global changes. The accuracy of numerical simulation of Earth's upper atmosphere depends on the accuracy of the estimation of such energy input or heating, which is always challenging. The heating is closely related with the ionospheric electric field and precipitating particles from the magnetosphere. Part of the difficulty of determining the heating is that the knowledge about their structures below the model resolution (i.e., small-scale and mesoscale variabilities) is still limited, especially about their correlation. Therefore, it is still unclear to what extent such correlation can impact the heating estimation. In this study, the correlation between small-scale and mesoscale electric field and particle precipitation variabilities has been quantified for the first time by utilizing satellite observations. Furthermore, the impact of small-scale and mesoscale variabilities and their correlation on the heating estimation has been evaluated unprecedentedly using a general circulation model. It is found that there can be a large localized overestimation of heating if the correlation b...

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Section: Resultsmentioning

confidence: 99%

Small‐Scale and Mesoscale Variabilities in the Electric Field and Particle Precipitation and Their Impacts on Joule Heating

et al. 2018

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“…Previous observations of the flow perturbations (Chen & Heelis, 2018) show that they are quite uniformly distributed in local time and most frequently occupy the high-latitude extreme of the auroral oval and the 10.1029/2018JA026128 Journal of Geophysical Research: Space Physics region just poleward of the convection reversal boundary. Since most perturbations are identified from latitudinal variations of the plasma velocity, the observations specify the latitudinal dimensions of the flow perturbations with high fidelity but restrict our knowledge of their longitudinal dimensions.…”

Section: Discussionmentioning

confidence: 97%

“…In this case the apparently different characteristic times can be produced by different spatial distributions for the flows at the leading and trailing edges of the structure. Previous work by Chen and Heelis (2018) suggests that flow perturbations are embedded in the background flow with a median magnitude of 500 m/s. If perturbations move with the background flow, these perturbations can contribute to the large differences in characteristic times for growth and decay.…”

Section: 1029/2018ja026128mentioning

confidence: 98%

Temporal Characteristic of the Mesoscale Plasma Flow Perturbations in the High‐Latitude Ionosphere

Chen

Heelis

2019

JGR Space Physics

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The spatial characteristics of mesoscale plasma perturbations in the high‐latitude ionosphere are important considerations for a more complete description of the energy deposition from the magnetosphere. In this study, ion drift and particle precipitation measurements from the Defense Meteorological Satellite Program F17 satellite during local summer seasons in 2012 are used to examine the flow perturbations and their closure paths and the particle precipitation associated with them. The closed circulation associated with a flow perturbation is identified from the potential distribution and can be described by a single‐cell or a two‐cell configuration with characteristic spatial scale sizes between 100 and 600 km and 200 and 1,200 km, respectively. Observations suggest that an asymmetry in space and flow speed is frequently seen with faster flows in a narrower region and slower return flows in wider adjacent regions. For a single‐cell configuration, the faster flows are preferentially sunward and in the same direction as the background convection, and the weaker return flows are preferentially duskward/dawnward of the potential maxima/minimum. For a two‐cell configuration, the faster flow is seen in the central region and also tends to follow the background convection with weaker return flows on the two sides. Except in the region poleward of the convection reversal boundary, 0.5–3 keV electron precipitation, displaying the same spatial asymmetry as the flow perturbation, is frequently seen in a single cell around a potential minimum on the dusk side.

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“…However, advances in computational capabilities allow adjustable time steps and adaptable grids in space to incorporate smaller scale convection features more explicitly (Zhu et al, 2018). Advances in defining multiscale features in the ionospheric plasma motions and the field-aligned currents associated with them are now being made (Chen & Heelis, 2018;Gabrielse et al, 2018;McGranaghan et al, 2017). At the present time our descriptions of the spatial and temporal variations in the observed plasma velocity structure are rather primitive, and observations of auroral emissions that are associated with spatial structures with scales of 100 to 500 km show that many times, these features are moving (e.g., Kim et al, 2017;Zou et al, 2014, and references therein).…”

Section: Multiple Scalesmentioning

confidence: 99%

Challenges to Understanding the Earth's Ionosphere and Thermosphere

Heelis¹,

Maute

2020

JGR Space Physics

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We discuss, in a limited way, some of the challenges to advancing our understanding and description of the coupled plasma and neutral gas that make up the ionosphere and thermosphere (I‐T). The I‐T is strongly influenced by wave motions of the neutral atmosphere from the lower atmosphere and is coupled to the magnetosphere, which supplies energetic particle precipitation and field‐aligned currents at high latitudes. The resulting plasma dynamics are associated with currents generated by solar heating and upward propagating waves, by heating from energetic particles and electromagnetic energy from the magnetosphere and by the closure of the field‐aligned currents applied at high latitudes. These three contributors to the current are functions of position, magnetic activity, and other variables that must be unraveled to understand how the I‐T responds to coupling from the surrounding regions of geospace. We have captured the challenges to this understanding in four major themes associated with coupling to the lower atmosphere, the generation and flow of currents within the I‐T region, the coupling to the magnetosphere, and the response of the I‐T region reflected in the neutral and plasma density changes. Addressing these challenges requires advances in observing the neutral density, composition, and velocity and simultaneous observations of the plasma density and motions as well as the particles and field‐aligned current describing the magnetospheric energy inputs. Additionally, our modeling capability must advance to include better descriptions of the processes affecting the I‐T region and incorporate coupling to below and above at smaller spatial and temporal scales.

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Mesoscale Plasma Convection Perturbations in the High‐Latitude Ionosphere

Cited by 10 publications

References 40 publications

Small‐Scale and Mesoscale Variabilities in the Electric Field and Particle Precipitation and Their Impacts on Joule Heating

Small‐Scale and Mesoscale Variabilities in the Electric Field and Particle Precipitation and Their Impacts on Joule Heating

Temporal Characteristic of the Mesoscale Plasma Flow Perturbations in the High‐Latitude Ionosphere

Challenges to Understanding the Earth's Ionosphere and Thermosphere

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