Earth's ion upflow associated with polar cap patches: Global and in situ observations

Abstract

We report simultaneous global monitoring of a patch of ionization and in situ observation of ion upflow at the center of the polar cap region during a geomagnetic storm. Our observations indicate strong fluxes of upwelling O+ ions originating from frictional heating produced by rapid antisunward flow of the plasma patch. The statistical results from the crossings of the central polar cap region by Defense Meteorological Satellite Program F16–F18 from 2010 to 2013 confirm that the field‐aligned flow can turn upward when rapid antisunward flows appear, with consequent significant frictional heating of the ions, which overcomes the gravity effect. We suggest that such rapidly moving patches can provide an important source of upwelling ions in a region where downward flows are usually expected. These observations give new insight into the processes of ionosphere‐magnetosphere coupling.

The Ion/Electron Temperature Characteristics of Polar Cap Classical and Hot Patches and Their Influence on Ion Upflow

“…As the convection speed increases, upflows may be seen when the electron temperature is not elevated above the ion temperature. These observations were assigned to frictional heating described previously by Zhang et al (2016), which only occur when the plasma convection speed exceeds 1,000 m/s. Many more upflow events associated with plasma patches occur when the electron temperature exceeds the ion temperature.…”

“…As the T i / T e ratio or the T i ‐ T e difference increases, which implies that the patches are turning from hot patches to classical patches, the vertical flux turns from upward to downward. The vertical flux also increases with the increasing convection speed, which corresponds to frictional heating and patch evolution (Ma et al, ; Zhang et al, ) and localized field‐aligned current associated with electron heating (Strangeway et al, ). When T i / T e = 0.8, or T e = T i + 600 K, we see a transition between upward and downward flux in the DMSP data set.…”

“…Patches around 75° MLAT are associated with significant field‐aligned current, strong convection speed, and higher electron temperature ( T i / T e < 0.8) and appear to be the polar cap hot patches (Zhang et al, ). The upflow occurrence is higher in the hot patches, possibly due to the electron precipitation which moves ions upward through the ambipolar electric field (Strangeway et al, ) with additional contributions from frictional heating associated with strong convection speed (Figure b; around 800 m/s antisunward) associated with frictional heating (Zhang et al, ). Compared to the hot patches that have high convection speed and strong field‐aligned current, the classical patches in the central polar cap generally show lower convection speed, weaker current, and lower electron temperature compared to the ion temperature.…”

Observations of ion‐neutral coupling associated with strong electrodynamic disturbances during the 2015 St. Patrick's Day storm

“…Yeh and Foster [] reported a supersonic ion outflow speed at 800 km altitude during a great storm event with a maximum K p of 9, and a speed of 400–500 m/s at 400 to 500 km altitude. Zhang et al [] also indicated the correlation between the horizontal ion drift and the vertical ion drift at the DMSP satellite altitude in the polar cap, suggesting effects of frictinal heating. In addition to frictional heating effects, the study also suggested that localized heating produced by precipitating O + could account for observed ion outflows.…”

Chinese ionospheric investigations in 2016–2017

“…Zhang QH et al (2016a) reported simultaneous global monitoring of a patch of ionization and in situ observations of ion upflow at the center of the polar cap region during a geomagnetic storm. These observations indicate strong fluxes of upwelling O + ions originating from frictional heating produced by rapid antisunward flows of the plasma patch.…”