Auroral precipitation/ion upwelling as a driver of neutral density enhancement in the cusp

Sadler, B.; Lessard, M.; Lund, E. J.; Otto, A.; Lühr, H.

doi:10.1016/j.jastp.2012.03.003

Cited by 28 publications

(45 citation statements)

References 48 publications

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“…However, for the case of 24 June 2009, when Clusters 3 and 4 were less than or at about 2 R E from the Earth and when solar wind dynamic pressure was high (about 8 nPa), we could detect oxygen density as high as 4 cm −3 with velocities up to 20 km s −1 antiparallel to the magnetic field. These velocities correspond to results from Sadler et al (2012). This may be an indication that thermosphere upwelling (neutral density increase) is associated also with ion outflow.…”

Section: Discussionsupporting

confidence: 83%

“…Similar study was done by Sadler et al (2012) who studied a conjunction between FAST and CHAMP satellite. Their conclusion was that thermospheric density enhancements were a combination of soft particle precipitation and ion outflow, which further, drove neutrals to the CHAMP altitude.…”

Section: T žIvković Et Al: Energy Deposition Through the Cuspmentioning

confidence: 55%

“…The quantitative analysis for all three events presented in Table 1 indicate that stronger soft electron precipitation is accompanied by stronger density enhancements in the thermosphere, which further strengthens the importance of soft electron precipitation in thermospheric upwellings. Further arguments that support this can be found in Clemmons et al (2008) and Sadler et al (2012). Clemmons et al (2008) has explained density enhancements as a result of direct energy transfer from soft electrons to neutrals.…”

Section: Discussionmentioning

confidence: 82%

“…Clemmons et al (2008) has explained density enhancements as a result of direct energy transfer from soft electrons to neutrals. On the other hand, Sadler et al (2012) suggested that density enhancements could be explained as a combination of soft electrons which heat electrons in the thermosphere, and cause ion outflow.…”

Section: Discussionmentioning

confidence: 99%

“…We see densities up to 4 cm −3 together with velocities up to 20 km s −1 in the period before 17:42 UT. Oxygen ions coming from the ionosphere could be a result of both Joule heating from the E region, but also from the charge imbalance produced through soft electron precipitation (Sadler et al, 2012).…”

Section: June 2009 Cusp Eventmentioning

confidence: 99%

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Investigation of energy transport and thermospheric upwelling during quiet magnetospheric and ionospheric conditions from the studies of low- and middle-altitude cusp

et al. 2015

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Abstract. We investigate energy fluxes and small, kilometrescale Birkeland currents in the magnetospheric cusp at a 1-3 Earth radii altitude and in the ionosphere using satellites when they were, according to the Tsyganenko model, in magnetic conjunction within 50-60 km and up to 15 min apart. We use Cluster and CHAMP satellites, and study three conjunction events that occurred in 2008 and 2009, when the Cluster spacecraft were crossing the cusps at only a few Earth radii altitude. Our goal is to understand better the influence of processes in the magnetospheric cusp on the upper thermosphere and its upwelling which was usually observed by the CHAMP satellite passing the cusp. Three studied events occurred under relatively quiet and steady magnetospheric and ionospheric conditions, which explains why observed thermospheric density enhancements were rather low. Our findings point out that for each studied event soft electron precipitation influences thermospheric density enhancements in a way that stronger electron precipitation produces stronger thermospheric upwelling. Therefore, in the case of these weak events, soft electron precipitation seems to be more important cause of the observed, thermospheric density enhancements than is the Joule heating.

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Section: Discussionsupporting

confidence: 83%

Section: T žIvković Et Al: Energy Deposition Through the Cuspmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: June 2009 Cusp Eventmentioning

confidence: 99%

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Investigation of energy transport and thermospheric upwelling during quiet magnetospheric and ionospheric conditions from the studies of low- and middle-altitude cusp

et al. 2015

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Solar wind control of auroral Alfvénic power generated in the magnetotail

et al. 2014

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The effects of solar wind driving conditions on the polar distribution of large‐scale, nondispersive Alfvénic Poynting flux at low altitude during steady magnetosphere convections are studied using three‐dimensional global simulations of the solar wind‐magnetosphere‐ionosphere interaction. Results from 18 test simulations driven by steady upstream solar wind (SW) and interplanetary magnetic field (IMF) conditions are used to investigate the relationship between SW/IMF driving and low‐altitude signatures of large‐scale Alfvénic Poynting flux. When the IMF is southward, the intensity of the Alfvénic Poynting flux increases, and the hemispheric integrated Alfvénic Poynting flux exhibits a linear relation with the SW electric field. When the IMF has a By component, the simulated hemispheric Alfvénic power does not fit to the same linear relation. During steady IMF By driving conditions, the low‐altitude regions with enhanced Alfvénic Poynting flux are magnetically connected with magnetospheric dynamo regions on both open and closed field lines. The physical origin of low‐altitude Alfvénic Poynting flux connecting to the closed field line region is similar with that during southward IMF Bz driving. However, the Alfvénic Poynting flux flowing from the open field line dynamo region may be related to the physical process on the magnetopause, and only shear‐mode waves are generated.

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Which cusp upflow events can possibly turn into outflows?

2014

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Two sequences, before and after magnetic noon, respectively, of poleward moving auroral forms with associated upflows situated above the European Incoherent Scatter Svalbard Radar allowed close study of ion upflow dynamics. We find that flux intensity is correlated with plasma temperature and that upflowing plasma undergoes acceleration proportional to the slope of the velocity profile and to the velocity at each altitude. The potential for upflows to lift thermal plasma to regions where broadband extremely low frequency electric field activity can cause nonthermal acceleration leading to outflow is examined. Equations for estimating the travel time of upflowing plasma are presented. We find that around 40% of the observed upflow profiles with a unit number flux greater than 1 × 10 13 m À2 s À1 can transport plasma from 500 to 800 km altitude in less than 10 min, approximately the typical lifetime of pulsed upflow events. Almost all such profiles can transport plasma from 600 to 800 km in the same time span. Typical transport times for other altitude ranges are also presented. Post magnetic noon the background electron density was somewhat higher than prenoon due to transport of EUV-enhanced plasma, and the postnoon ion flux was somewhat weaker than prenoon.

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Auroral precipitation/ion upwelling as a driver of neutral density enhancement in the cusp

Cited by 28 publications

References 48 publications

Investigation of energy transport and thermospheric upwelling during quiet magnetospheric and ionospheric conditions from the studies of low- and middle-altitude cusp

Investigation of energy transport and thermospheric upwelling during quiet magnetospheric and ionospheric conditions from the studies of low- and middle-altitude cusp

Solar wind control of auroral Alfvénic power generated in the magnetotail

Which cusp upflow events can possibly turn into outflows?

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