Ion Upflow Research Articles

Statistical Properties of Ion Upflow Associated With Subauroral Ion Drift (SAID) in the Northern and Southern Hemispheres

AbstractThe ion upflow has great significance for the transport and exchange of particles during magnetosphere‐ionosphere coupling process. Previous studies focus on the ion upflow in the polar region, and find that ion upflow has hemispheric asymmetries. In subauroral region, the ion upflow is closely related with subauroral ion drift (SAID). However, the characteristics of ion upflow associated with SAID in both northern and southern hemispheres are still unknown. Based on the observation of DMSP satellites F16‐F18 from 2010 to 2020, we investigate the north‐south hemisphere distributions of ion upflow associated with SAID during quiet and disturbed time. The ion upflow rate presents localized features in both hemispheres. The ion upflow rate in the southern hemisphere is slightly higher/lower than that in the northern hemisphere before/after 1900 MLT. The ion upflow velocity in the southern hemisphere shows a clear dependence on magnetic local time (MLT). Furthermore, We find that the hemispheric asymmetry of ion upflow is closely related to the asymmetric configuration of the ionospheric parameters such as plasma density, conductance and solar elevation angle during magnetosphere‐ionosphere coupling process. The result also indicates that SAID and sunlight condition play important roles in the ion upflow in subauroral region.

A statistical analysis and comparison of the fine structures of the ion upflow associated with the double-peak subauroral ion drift

The ion upflow associated with the subauroral ion drift (SAID) is a crucial component in the exchange of particles between the ionosphere and the ring currents. The ion upflow associated with the double-peak subauroral ion drift (DSAID), which is a subclass of the SAID, is more complex compared to SAID. In this study, we conducted a statistical analysis of the ion upflow associated with DSAID using Defense Meteorological Satellite Program (DMSP) F16–F18 data spanning 11 years (2010–2020) in the Northern Hemisphere. Our findings revealed that ion upflow associated with DSAID can exhibit either a double-peak or a one-peak upflow. The statistical characteristics of these two types of events displayed significant differences. In DSAID with a double-peak upflow event, the velocity of DSAID around the high-latitude peak was greater than that around the low-latitude peak. However, in DSAID with a one-peak upflow event, the DSAID velocities around the two peaks were very similar. Based on the formation mechanism of DSAID and the process of frictional heating in the ionosphere, we proposed that the formation of DSAID with a double-peak upflow and DSAID with a one-peak upflow are likely related to the formation process of DSAID.

Interhemispheric asymmetries of neutral upwelling and ion upflow

This work addresses interhemispheric differences in cusp-related neutral density enhancements. The focus is on enhancements that are driven by Poleward Moving Auroral Forms (PMAF), which provide a repetitive sequence of soft electron precipitation to the ionosphere. Because the time-scales of the resultant electron heating, ion upflow and neutral upwelling range from a few seconds to tens of minutes, i.e., longer than the time required for the thermosphere to return to its relaxed state, each subsequent PMAF encounters different initial conditions. With this in mind, our study investigates the role of a dark versus daylight ionosphere, using 3 different scenarios. The first case compares this effect during solar minimum at Longyearbyen, Svalbard, an ideal location for observing cusp dynamics. The second case addresses solar maximum at Longyearbyen and the third case compares Longyearbyen to its magnetically conjugate Zhongshan Station in Antarctica. We conclude 1) for each of the 3 scenarios ion upflow speeds, neutral upwelling speeds and neutral density enhancements are all significantly greater in a dark ionosphere, by perhaps as much as a factor or 2 or 3, relative to a sunlit ionosphere, 2) that upflowing ions are the driver of neutral upwelling via ion-neutral collisions (momentum transfer), with fast-moving ions transferring upward momentum to slow-moving neutrals, and 3) the ratios of neutral upflow speeds to ion upflow speeds, vnSunlit/viSunlit is the order of 0.07 for all stations (at 800 km) in the first and second cases studied, but only 0.02 at Zhongshan in the 3rd case studied, a factor of ∼3 less than the other locations. This is thought to be due to an increased thermospheric density at Zhongshan, which essentially provides a greater total mass for the upflowing ions to lift.

History of EISCAT – Part 6: the participation of Japan in the EISCAT Scientific Association

Abstract. In Sect. 1, the original planning of Japanese Svalbard IS (incoherent scatter) radar with phased-array antennas is described. In 1988, this plan was proposed as one of the major projects for the forthcoming Solar–Terrestrial Environment Laboratory, Nagoya University, Japan, to be reorganized by the Research Institute of Atmospherics at Nagoya University. On the other hand, in 1989, UK scientists proposed a plan of polar cap radar with parabolic dish antennas in Longyearbyen to the EISCAT (European incoherent scatter) Council. In Sect. 2, the circumstances leading to Japan's participation in the EISCAT Scientific Association, with details of its processes with strong collaborations with Norwegian scientists and the EISCAT Scientific Association are described. In 1995, Japan participated EISCAT Scientific Association as the seventh member country with funds contributing to the second dish antenna of the EISCAT Svalbard Radar. In Sect. 3, a summary of the EISCAT-related achievement by Japanese scientists is described, where major interests are the lower thermosphere wind dynamics, the magnetosphere–ionosphere–thermosphere coupling, characteristics, and driving mechanisms of ion upflow, electrodynamics of current, electric field and particles, characteristics and production mechanisms of auroras, such as pulsating aurora, and aurora tomography. In Sect. 4, a summary of the scientific collaborations between Japan and Europe, particularly those between Japan and Norway, and hopes for the forthcoming EISCAT_3D and further collaboration with EISCAT community are described.

A Comparative Study on the Hot Dense Plasma and Cold Patch by Using Multi‐Instrument Observations

AbstractThe polar cap hot patch is an enhanced density structure which is associated with particle precipitation, ion upflow and flow shears. Based on combined observations from DMSP satellites, EISCAT radar, and all‐sky imager at the Chinese Yellow River Station, the plasma characteristics and evolution of hot dense plasma and classical polar cap patch are investigated. Both of them show enhanced F region density, but the hot dense plasma is associated with higher electron temperature and enhanced E region electron density caused by particle precipitation. Compared to the cold patch, the hot dense plasma is closer to the cusp region and is associated with strong auroral emissions. Based on the joint observations, the evolution of the hot/cold dense plasma is discussed. In the initial phase the dense plasma comes from the sunlit lower latitude region, or from particle precipitation in the duskside auroral oval, and is heated locally by poleward moving auroral structures in the dayside auroral oval. Next the patches move poleward into the polar cap where a decaying electron temperature (i.e., less precipitation) gradually transform them into a cold patch.

Light ion dynamics in the topside ionosphere and plasmasphere during geomagnetic storms

Storm-time topside ionosphere plasma composition, especially the light ion fraction, is an important parameter which controls magnetosphere–ionosphere coupling, plays a part in the growth of local instabilities, and provides information about the ring current, ion upflow, movement of ionization and other important physical processes and parameters. Ion composition is difficult to estimate on fine scales as empirical models tend to be parametrized by fixed inputs, ignoring the role of memory in plasma, and to preferentially capture large scales, while ground radars have limited coverage. In particular, ionospheric composition measurements at mid-latitude are lacking. Here we show, using the new Swarm SLIDEM effective ion mass measurement, a superposed epoch analysis of storm-time dayside and nightside effective ion mass changes, demonstrating the extent and timescales of motion of the [O+]/[H+] transition height with the main phase of geomagnetic storms, as well as directly observing evidence for the latitude dependence of these dynamics.Graphical

Classification and Distribution of the Dayside Ion Upflows Associated with Auroral Particle Precipitation

Two important phenomena of the solar wind–magnetosphere–ionosphere coupling are auroral particle precipitation and the formation of ions flowing upward from the ionosphere. They have opposite transport directions of energy and substance. Based on the observations of particle precipitation and ion drift from the DMSP F13 satellite in January and July 2005, the ionospheric ion upflows in dayside auroral oval (0600–1800 MLT) can be divided into five types according to the velocity of ion upflows and the spectrum characteristics of auroral particle precipitation, and the distribution for different types of ion upflows is studied. The results show that the ion upflows mainly occur in the geomagnetic latitude (MLAT) range of 70–80°.The main magnetospheric source region of ion upflows (type A and D) caused by the accelerated electron (mainly the soft electron) corresponds to Low Latitude Boundary Layer (LLBL) and Cusp, and ion upflows of type B and C (related to the process of ambipolar diffusion caused by electron acceleration) mainly occur in LLBL and Boundary Plasma Sheet (BPS), while ion upflows of type E without electron acceleration mainly occur in the central plasma sheet (CPS).The dawn–dusk asymmetry is obvious in the winter season, with the ion upflows mainly occurring on the dawn/dusk side ionosphere. However, the ion upflows in summer mainly occur at the magnetic noon, with a symmetric distribution centered at the magnetic noon. The occurrence of ion upflow in winter is significantly higher than that in summer, and it is significantly enhanced during the period of moderate geomagnetic activity. The upward region expands to the lower latitude when the geomagnetic activity is enhanced. The effect of interplanetary magnetic field (IMF) components has also been studied in this paper. When IMF Bx is negative, the upflow occurrence increases in the region of 1500–1800 MLT and 0600–0900 MLT, with the MLAT range below 70°. The direction of IMF By may lead to the high-incidence area reverse at the prenoon or postnoon region. The occurrence of ion upflows with the MLAT range below 75° increases significantly when IMF is southward. Type A ion upflow has the highest velocity of ion upflows, followed by type E, and type D has the lowest. The average velocity of ion upflows in winter is significantly higher than that in summer.

Observations for the Ionosphere Using European Incoherent Scatter (EISCAT) in the Dayside Polar Cap/Cusp and Auroral Region

Korea Polar Research Institute (KOPRI) and Korea Astronomy and Space Institute (KASI) have been participating in the European Incoherent Scatter (EISCAT) Scientific Association as an affiliate institution in order to observe the polar ionosphere since 2015. During the period of December 16–21, 2016 and January 3–9, 2018, the observations for the polar ionospheric parameters such as the electron density profiles, ion drift, and electron/ion temperature are carried out in the polar cap/cusp region by the EISCAT Svalbard radar (ESR). The purpose of the observations is to investigate the characteristic of the winter ionosphere in the dayside polar cap/cusp region. In this paper, we briefly report the results of the ESR observations for winter daytime ionosphere and also the simultaneous observations for the ionosphere-thermosphere system together with the balloon-borne instrument High-Altitude Interferometer WIND Experiment (HIWIND) performed by the High Altitude Observatory (HAO), National Center for Atmospheric Research (NCAR). We further introduce our research activities using long-term EISCAT observations for the occurrence of ion upflow and the climatology of the polar ionospheric density profiles in comparison with the mid-latitude ionosphere. Finally, our future research plans will briefly be introduced.

A Statistical Study of Ion Upflow during Periods of Dawnside Auroral Polarization Streams and Subauroral Polarization Streams

We have investigated the effect of the dawnside subauroral polarization stream (SAPS) and dawnside auroral polarization stream (DAPS) on the ionospheric ion upflow in the Northern Hemisphere by using four years of Defense Meteorological Satellite Program (DMSP) observations. The occurrence rate of DAPS is higher than that of dawnside SAPS. Obvious ion upflow occurs in the topside ionosphere around the DAPS region. The effect of the dawnside SAPS on the vertical flow is weakened when geomagnetic activity increases. There are prominent upflow fluxes around the DAPS, while there are insignificant upflow fluxes around the SAPS region. The plasma density trough during SAPS periods becomes shallower with increasing magnetic activity. These variations with magnetic activity might be due to the weakened ion-neutral collision heating efficiency during highly disturbed periods. There is no obvious plasma density trough or ion temperature drop around the DAPS region at the altitude of ~800 km. The ion temperature around the SAPS area decreases, while the electron temperature increases around the DAPS and SAPS regions.

Explaining Ionospheric Ion Upflow in the Subauroral Polarization Streams

Ionospheric ion upflow is an important process for magnetosphere-ionosphere coupling via O+ source for the magnetosphere. This process occurs frequently in the subauroral polarization stream (SAPS) region where the SAPS-enhanced ion-neutral frictional heating tends to push ions upward because of enhanced upward pressure gradient force. However, the SAPS-induced neutral wind transport by ion-neutral friction may also play an important role in triggering ion upflow, which has been rarely studied. In this work, the thermosphere-ionosphere-electrodynamics general circulation model (TIEGCM) with/without an empirical SAPS model has been employed to investigate the impacts of SAPS on ion upflow in the topside ionosphere. Our results separate different transport processes in the ion continuity equation, showing that SAPS can accelerate upward ambipolar diffusion along its channel because of ion-neutral frictional heating, but SAPS-induced horizontal neutral wind may have a comparable or even larger contribution to vertical ion drift when SAPS are fully developed. In addition, the neutral wind can induce both upward and downward ion drift in the SAPS region, depending on the direction of the neutral wind and the local geomagnetic declination and inclination.

Observations of ion upflow and 630.0 nm emission during pulsating aurora

In this study, we report observations made by filtered (557.7 and 630.0 nm) All-Sky Imagers located at Poker Flat, Alaska alongside Poker Flat Incoherent Scatter Radar data for an event observed on 5 February 2017. Together, the data indicate ion upflow in the vicinity of pulsating aurora. Additionally, the data show a strong 630.0 nm (red-line) auroral emission. Observations of pulsating aurora are typically reported at 557.7 and 427.8 nm, as these wavelengths are more sensitive to high-energy (∼ tens of keV) electron precipitation. In contrast, 630.0 nm emission is generated preferentially by low-energy soft electron precipitation (∼ hundreds of eV), and is less commonly observed. The All-Sky Imager data discussed here are unusual in that they suggest regions of enhanced soft electron precipitation in conjunction with enhanced ambipolar electric fields, which are a known factor contributing to ion outflow.

Connecting Energy Input With Ionospheric Upflow and Outflow

AbstractThe connection between energy inputs and the generation of ion upflows and outflows is a topic of keen scientific interest and the subject of a number of empirical studies. Despite this interest, it remains uncertain how different ion species respond to energy input, what defines the upper and lower bounds of the ion flux, and what role solar illumination plays in regulating the relationship between energy input and ion upflows/outflows. This work simulates how ion flux scales with low and high altitude energization, and to a combination of both. Furthermore, we examine the influence of solar illumination on these relationships by considering how the scaling of ion flux with energy input changes over the solar cycle, comparing solar minimum and maximum, as well as how they change from day to night conditions. We find O+ flux tends to respond more strongly to energy inputs than H+ flux, with the O+ flux often exhibiting a lower activation energy and a greater dynamic range. The lower bound of the ion flux at 4,000 km is typically defined by the polar wind H+, although O+ upflows can dominate at low altitudes in the presence of significant frictional heating of the ion gas or soft electron precipitation. However, when significant soft electron precipitation and wave‐particle interactions are present simultaneously the lower bound of the ion flux at 4,000 km is defined by the O+. Finally, we find a difference between the steady state response of the outflow to energy input and the peak response.

Explaining Solar Flare‐Induced Ionospheric Ion Upflow at Millstone Hill (42.6°N)

AbstractPrevious studies have shown that solar flares can significantly affect Earth's ionosphere and induce ion upflow with a magnitude of ∼110 m/s in the topside ionosphere (∼570 km) at Millstone Hill (42.61°N, 71.48°W). We use simulations from the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) and observations from Incoherent Scatter Radar (ISR) at Millstone Hill to reveal the mechanism of ionospheric ion upflow near the X9.3 flare peak (07:16 LT) on 6 September 2017. The ISR observed ionospheric upflow was captured by the TIEGCM in both magnitude and morphology. The term analysis of the F‐region ion continuity equation during the solar flare shows that the ambipolar diffusion enhancement is the main driver for the upflow in the topside ionosphere, while ion drifts caused by electric fields and neutral winds play a secondary role. Further decomposition of the ambipolar diffusive velocity illustrates that flare‐induced changes in the vertical plasma density gradient is responsible for ion upflow. The changes in the vertical plasma density gradient are mainly due to solar extreme ultraviolet (EUV, 15.5–79.8 nm) induced electron density and temperature enhancements at the F2‐region ionosphere with a minor and indirectly contribution from X‐ray (0–15.5 nm) and ultraviolet (UV, 79.8–102.7 nm).

Data of TIEGCM Simulation for manuscript "Explaining Solar Flare-Induced Ionospheric Ion Upflow at Millstone Hill (42.6° N)"

Data of TIEGCM Simulation for manuscript "Explaining Solar Flare-Induced Ionospheric Ion Upflow at Millstone Hill (42.6° N)"

Impact of Storm-Enhanced Density (SED) on Ion Upflow Fluxes During Geomagnetic Storm

The impact of the dynamic evolution of the Storm-Enhanced Density (SED) on the upward ion fluxes during the March 06, 2016 geomagnetic storm is studied using comprehensive multi-scale datasets. This storm was powered by a Corotating Interaction Region (CIR), and the minimum Sym-H reached ∼−110 nT. During the ionospheric positive storm phase, the SED formed and the associated plume and polar cap patches occasionally drifted anti-sunward across the polar cap. When these high-density structures encountered positive vertical flows, large ion upward fluxes were produced, with the largest upward flux reaching 3 × 1014 m−2s−1. These upflows were either the type-1 ion upflow associated with fast flow channels, such as the subauroral polarization stream (SAPS) channel, or the type-2 ion upflow due to soft particle precipitations in the cusp region. The total SED-associated upflow flux in the dayside cusp can be comparable to the total upflow flux in the nightside auroral zone despite the much smaller cusp area compared with the auroral zone. During the ionospheric negative storm phase, the ionospheric densities within the SED and plume decreased significantly and thus led to largely reduced upward fluxes. This event analysis demonstrates the critical role of the ionospheric high-density structures in creating large ion upward fluxes. It also suggests that the dynamic processes in the coupled ionosphere-thermosphere system and the resulting state of the ionospheric storm are crucial for understanding the temporal and spatial variations of ion upflow fluxes and thus should be incorporated into coupled geospace models for improving our holistic understanding of the role of ionospheric plasma in the geospace system.

Data of TIEGCM Simulation for manuscript "Solar Flare-Induced Ionospheric Ion Upflow at Millstone Hill"

Data of TIEGCM Simulation for manuscript "Solar Flare-Induced Ionospheric Ion Upflow at Millstone Hill"

Low‐Altitude Ion Upflow Observed by EISCAT and its Effects on Supply of Molecular Ions in the Ring Current Detected by Arase (ERG)

AbstractDuring the magnetic storm starting on September 7, 2017, the MEP‐i instrument onboard the Arase (ERG) satellite observed molecular ions (O2+/NO+/N2+) in the ring current. The molecular ions were observed by Arase in four orbits during this magnetic storm. This indicates that there was a continuous molecular ion supply from the ionosphere. During the storm main phase around the second Dst minimum (∼−100 nT) on September 8, 2017, the European Incoherent Scatter (EISCAT) radar observed the ion upflow (∼50–150 m s−1) in the low‐altitude (250–350 km) ionosphere together with strong ion heating up to >2,000 K. The convective electric field derived from the electron heating observed by EISCAT at an altitude of approximately 110 km was also enhanced by a factor of 2. The observations suggest that the additional ion heating at low altitudes helps to cause the fast upflow and transport molecular ions upward. The flux decreases from 280 to 350 km altitudes due to the dissociative recombination was estimated to be approximately two orders of magnitude. This resulted in significant molecular ion flux remaining at 350 km altitude. These results suggest that the low‐altitude ion upflow caused by the ion frictional heating enables molecular ions to escape to space against rapid loss by the dissociative recombination.

Statistical Study of Ion Upflow and Downflow Observed by PFISR

AbstractIon upflow in the F region and topside ionosphere can greatly influence the ion density and fluxes at higher altitudes and thus has significant impact on ion outflow. We investigated the statistical characteristics of ion upflow and downflow using a 3‐year (2011–2013) data set from the Poker Flat Incoherent Scatter Radar (PFISR). Ion upflow is twice more likely to occur on the nightside than on the dayside in PFISR observations, while downflow events occur more often in the afternoon sector. Upflow and downflow on the dayside tend to occur at altitudes ~500 km, higher than those on the nightside. Both upflow and downflow occur more frequently as ion convection speed increases. Upflow observed from 16 to 6 magnetic local time through midnight is associated with temperature and density enhancements. Occurrence rates of upflow on the nightside and downflow on the dayside increase with geomagnetic activity level. On the nightside, occurrence rate of ion upflow increases with enhanced solar wind and interplanetary magnetic field (IMF) drivers as well as southwestward local magnetic perturbations. The lack of correlation of upflow on the dayside with the solar wind and IMF parameters is because PFISR is usually equatorward of the dayside auroral zone. Occurrence rate of downflow does not show strong dependence on the solar wind and IMF conditions. However, it occurs much more frequently on the dayside when the IMF By > 10 nT and the IMF Bz < −10 nT, which we suggest is associated with the decaying of the dayside storm‐enhanced density (SED) and the SED plume.

Statistical Study of the Relationship Between Ion Upflow and Field‐Aligned Current in the Topside Ionosphere for Both Hemispheres During Geomagnetic Disturbed and Quiet Time

AbstractA statistical study of ion upflow and field‐aligned currents (FACs) has been performed in the topside ionosphere of both hemispheres for magnetic quiet and disturbed times by using DMSP satellite observations from 2010–2013. Distributions in MLT/MLat reveal that ion upflow occurrence shows a dawn‐dusk asymmetry distribution that matches well with the Region 1 FACs. In addition, there are highest occurrence regions near noon and within the midnight auroral disturbance area, corresponding to dayside cusp and nightside auroral disturbance regions, respectively. Both the ion upflow occurrence and FAC regions expand equatorward to a wider area during disturbed times.

Statistical Study of Ion Upflow Associated with Subauroral Polarization Streams (SAPS) at Substorm Time

AbstractWe present a statistical study of the ion upflow associated with subauroral polarization streams (SAPS) in the ionospheric subauroral region at different substorm times using three Defense Meteorological Satellite Program satellite (F16–F18) data for five years (2010–2014) in the Northern Hemisphere. The results show similarities between SAPS and the ion upflow at different intensity of substorms both in occurrence rate distribution and velocity distribution. In comparison to SAPS, the distribution of the ion upflow shows the smaller occurrence region and lower velocity. We also find that frictional heating plays an important role in ion upflow from the SAPS region. The intense substorms can trigger strong SAPS channels, enhanced frictional heating, and large ion upflow. In addition, there is a moderate linear correlation between SAPS velocity and field‐aligned velocity that is consistent with some previous findings. Our results also show that frictional heating can gradually dominate the ion upflow process in intense substorms, while it may not be the only factor to affect the whole upflow process.