Which cusp upflow events can possibly turn into outflows?

Skjæveland, Åsmund; Moen, J.; Carlson, H. C.

doi:10.1002/2013ja019495

Cited by 18 publications

(24 citation statements)

References 65 publications

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“…Furthermore, ion upflow with a high speed that is larger than 200 m/s is an important process in ionosphere-magnetosphere coupling. It is frequently seen in the cusp and auroral regions, as well as inside the polar cap (e.g., Coley et al, 2003Coley et al, , 2006Loranc et al, 1991;Moore et al, 1997;Moore & Horwitz, 2007;Skjaeveland et al, 2014;Yau et al, 2007Yau et al, , 2011. However, the largerscale spatial and temporal structures of the vertical ion motion and associated processes have not been well understood so far.…”

Section: Introductionmentioning

confidence: 99%

A Long‐Term Data Set of Vertical Ion Drift Velocity at High Latitudes Constructed From DMSP Measurements

Liu

Zhang

et al. 2018

JGR Space Physics

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Observations of vertical ion drift velocities (Vz) at the topside of the ionosphere by Defense Meteorological Satellite Program (DMSP) satellites have been accumulated over decades and provide us a unique opportunity to study the vertical ion drifts through the ionosphere on different temporal and spatial scales. In this paper, Vz data of F13, which are of high quality, are taken as the reference to rescale the measurements of DMSP F11, F12, F14, F15, and F16 at high latitudes from 50°N/S to 90°N/S, which show significant differences from each other in magnitudes. Through rescaling, all Vz data of F11–F16 are in a similar order of magnitudes. Moreover, their spatial and temporal distributions resemble each other on average and are consistent with the excepted averaged behaviors reported in previous studies. Thus, the rescaling is basically effective, which provides an opportunity to construct a data set of Vz from 1995 to 2014 that covers nearly two solar cycles for further statistical analysis. Meanwhile, it should be noted that the rescaling results are qualitative/semiqualitative with some uncertainty, which needs more detailed discussion and analysis in future studies.

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Section: Introductionmentioning

confidence: 99%

A Long‐Term Data Set of Vertical Ion Drift Velocity at High Latitudes Constructed From DMSP Measurements

Liu

Zhang

et al. 2018

JGR Space Physics

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“…Wahlund and Opgenoorth () defined a minimum threshold of 10 13 m −2 s −1 for an ion flux having the potential of becoming an outflow, while Skjæveland et al () referred to the same class of events as “strong upflow flux” with plasma temperatures >2,800 K enhancing the possibility of ion escape. Based on the study by Wahlund and Opgenoorth (), which found that potential outflow usually correlates with ion upflow fluxes of magnitude 10 13 m −2 s −1 and above, a further filter was applied to remove negative values and fluxes below 10 13 m −2 s −1 .…”

Section: Data Source and Criteria For Data Selectionmentioning

confidence: 99%

A Study of Observations of Ionospheric Upwelling Made by the EISCAT Svalbard Radar During the International Polar Year Campaign of 2007

et al. 2018

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We have used EISCAT Svalbard Radar data, obtained during the International Polar Year 2007 campaign, to study ionospheric upflow events with fluxes exceeding 1013 m−2 s−1. In this study, we have classified the upflow events into low, medium, and high flux upflows, and we report on the incidence and seasonal distribution of these different classes. It is observed that high upflow fluxes are comparatively rare and low flux upflow events are a frequent phenomenon. Analysis shows that occurrence peaks around local noon at 31%, 16%, and 2% for low, medium, and high‐flux upflow, respectively, during geomagnetically disturbed periods. In agreement with previous studies on vertical and field‐aligned flows, ion upflow is observed to take place over a wide range of geomagnetic conditions, with downflow flux occurrence being lower than upflow occurrence. In contrast to previous observations, however, the upflow occurrence is greater around noon during highly disturbed geomagnetic conditions than for moderate geomagnetic conditions. Analysis of the seasonal distribution reveals that, while high‐flux upflow has its peak around local noon in the summer, with its occurrence being driven predominantly by high geomagnetic disturbance, the occurrence of low‐flux upflow is broadly distributed across all seasons, geomagnetic activity conditions, and times of day. The medium‐flux upflow events, although distributed across all seasons, show an occurrence peak strongly related to high Kp. Furthermore, during highly disturbed conditions, the low‐flux and medium‐flux upflow events show a minimum occurrence during the winter, whereas minimum occurrence for the high‐flux upflow events occurs in autumn.

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“…Observations by a similar IDM instrument onboard the HILAT satellite showed upflow velocities as high as 1.6 km/s at 800 km altitude [Tsunoda et al, 1989]. At topside ionosphere altitudes, numerous ground-based radar observations have been conducted and the velocity values were in the range of 100-1000 m/s in the cleft/cusp region [Endo et al, 2000;Ogawa et al, 2000Ogawa et al, , 2008Skjaeveland et al, 2014]. Also, Burchill et al [2010] observed ion upflow up to 500 m/s using the CUSP-2002 sounding rocket's suprathermal ion imager (SII) data at around 700 km.…”

Section: 1002/2016ja022532mentioning

confidence: 99%

Strong ambipolar‐driven ion upflow within the cleft ion fountain during low geomagnetic activity

et al. 2016

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We investigate low‐energy (<10 eV) ion upflows (mainly O+) within the cleft ion fountain (CIF) using conjunctions of the Enhanced Polar Outflow Probe (e‐POP) satellite, the DMSP F16 satellite, the SuperDARN radar, and the Resolute Bay Incoherent Scatter Radar North (RISR‐N). The SEI instrument on board e‐POP enables us to derive ion upflow velocities from the 2‐D images of ion distribution functions with a frame rate of 100 images per second, and with a velocity resolution of the order of 25 m/s. We identify three cleft ion fountain events with very intense (>1.6 km/s) ion upflow velocities near 1000 km altitude during quiet geomagnetic activity (Kp < 3). Such large ion upflow velocities have been reported previously at or below 1000 km, but only during active periods. Analysis of the core ion distribution images allows us to demonstrate that the ion temperature within the CIF does not rise by more than 0.3 eV relative to background values, which is consistent with RISR‐N observations in the F region. The presence of soft electron precipitation seen by DMSP and lack of significant ion heating indicate that the ion upflows we observe near 1000 km altitude are primarily driven by ambipolar electric fields. DC field‐aligned currents (FACs) and convection velocity gradients accompany these events. The strongest ion upflows are associated with downward current regions, which is consistent with some (although not all) previously published results. The moderate correlation coefficient (0.51) between upflow velocities and currents implies that FACs serve as indirect energy inputs to the ion upflow process.

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Which cusp upflow events can possibly turn into outflows?

Cited by 18 publications

References 65 publications

A Long‐Term Data Set of Vertical Ion Drift Velocity at High Latitudes Constructed From DMSP Measurements

A Long‐Term Data Set of Vertical Ion Drift Velocity at High Latitudes Constructed From DMSP Measurements

A Study of Observations of Ionospheric Upwelling Made by the EISCAT Svalbard Radar During the International Polar Year Campaign of 2007

Strong ambipolar‐driven ion upflow within the cleft ion fountain during low geomagnetic activity

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