Sources of Ion Outflow in the High Latitude Ionosphere

Yau, A. W.; André, Mats

doi:10.1007/978-94-009-0045-5_1

Cited by 223 publications

(310 citation statements)

References 52 publications

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“…S1f) within these events. As upflowing ions from the ionosphere normally consist of a large oxygen ion component 7,34 , this provides further evidence that the dominant portion of these ions (protons) is derived from the magnetosheath and not from the ionosphere. The data suggests, therefore, that these populations have entered at the high-latitude magnetopause during northward IMF (Fig.…”

Section: Resultsmentioning

confidence: 76%

“…Additionally, event selection was made according to the particle energy flux in the lobe: we require that the energy band between 700 ev and 2 keV, and at least one order of magnitude for all energy bands, contain a particle energy flux greater than 8 Â 10 4 keVs À 1 cm À 2 si À 1 keV À 1 . Based on these criteria, only events with magnetosheath or cusp-like 35,36 ions with energy around 1 keV were selected, and the upflowing ions with lower energy 29,34 from the ionosphere were excluded.…”

Section: Resultsmentioning

confidence: 99%

“…A total of 104 events was found, with 45 and 59 occurring in the southern and northern hemispheres, respectively. Figure 3a shows that the plasma density of these events is greater than 0.05 cm À 3 , which is much higher than the lobe background level 29,34 . The bulk ion flow speeds are below 60 km s À 1 (not shown).…”

Section: Nature Communications | Doimentioning

confidence: 87%

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Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times

et al. 2013

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An understanding of the transport of solar wind plasma into and throughout the terrestrial magnetosphere is crucial to space science and space weather. For non-active periods, there is little agreement on where and how plasma entry into the magnetosphere might occur. Moreover, behaviour in the high-latitude region behind the magnetospheric cusps, for example, the lobes, is poorly understood, partly because of lack of coverage by previous space missions. Here, using Cluster multi-spacecraft data, we report an unexpected discovery of regions of solar wind entry into the Earth's high-latitude magnetosphere tailward of the cusps. From statistical observational facts and simulation analysis we suggest that these regions are most likely produced by magnetic reconnection at the high-latitude magnetopause, although other processes, such as impulsive penetration, may not be ruled out entirely. We find that the degree of entry can be significant for solar wind transport into the magnetosphere during such quiet times.

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Section: Resultsmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 99%

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Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times

et al. 2013

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“…The classical picture of the polar wind is as an ambipolar flow in which H + and He + escape the Earth's gravity at supersonic speeds but the heavier O + does not [Axford, 1968;Banks and Holzer, 1968, 1969a, 1969b. The nonclassical polar wind includes other energization processes which can accelerate O + to escape energies and create nonthermal ion beams and conics (see Yau and André [1997], André and Yau [1997] Moore et al [1999], and Yau et al [2011] for reviews). Both the amount of light ions outflowing in the classical polar wind and the amount of heavy ions upflowing to regions where energization processes could be important are controlled by the plasma densities and temperatures in the F region and topside ionosphere [e.g., Schunk, 2007].…”

Section: Introductionmentioning

confidence: 99%

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

2014

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Photoelectrons escape from the ionosphere on sunlit polar cap field lines. In order for those field lines to carry zero current without significant heavy ion outflow or cold electron inflow, field-aligned potential drops must form to reflect a portion of the escaping photoelectron population back to the ionosphere. Using a 1-D ionosphere-polar wind model and measurements from the Resolute Bay Incoherent Scatter Radar (RISR-N), this paper shows that these reflected photoelectrons are a significant source of heat for the sunlit polar cap ionosphere. The model includes a kinetic suprathermal electron transport solver, and it allows energy input from the upper boundary in three different ways: thermal conduction, soft precipitation, and potentials that reflect photoelectrons. The simulations confirm that reflection potentials of several tens of eV are required to prevent cold electron inflow and demonstrate that the flux tube integrated change in electron heating rate (FTICEHR) associated with reflected photoelectrons can reach 10 9 eV cm −2 s −1 . Soft precipitation can produce FTICEHR of comparable magnitudes, but this extra heating is divided among more electrons as a result of electron impact ionization. Simulations with no reflected photoelectrons and with downward field-aligned currents (FAC) primarily carried by the escaping photoelectrons have electron temperatures which are ∼250-500 K lower than the RISR-N measurements in the 300-600 km region; however, simulations with reflected photoelectrons, zero FAC, and no other form of heat flux through the upper boundary can satisfactorily reproduce the RISR-N data.

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“…Out¯ow could be reproduced during conditions of very strong heating. Satellite observations and theory of ion out¯ow were recently reviewed by Yau and AndreÂ (1997), AndreÂ and Yau (1997), and Horwitz and Moore (1997).…”

Section: Introductionmentioning

confidence: 99%

Ion upflow and downflow at the topside ionosphere observed by the EISCAT VHF radar

Endo¹,

Fujii²,

Ogawa³

et al. 2000

Annales Geophysicae

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Abstract. We have determined the MLT distribution and K P dependence of the ion up¯ow and down¯ow of the thermal bulk oxygen ion population based on a data analysis using the EISCAT VHF radar CP-7 data obtained at Tromsù during the period between 1990 and 1996: (1) both ion up¯ow and down¯ow events can be observed at any local time (MLT), irrespective of dayside and nightside, and under any magnetic disturbance level, irrespective of quiet and disturbed levels; (2) these up¯ow and down¯ow events are more frequently observed in the nightside than in the dayside; (3) the up¯ow events are more frequently observed than the down¯ow events at any local time except midnight and at any K P level and the di erence of the occurrence frequencies between the up¯ow and down¯ow events is smaller around midnight; and (4) the occurrence frequencies of both the ion up¯ow and down¯ow events appear to increase with increasing K P level, while the occurrence frequency of the down¯ow appears to stop increasing at some K P level.

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Sources of Ion Outflow in the High Latitude Ionosphere

Cited by 223 publications

References 52 publications

Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times

Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

Ion upflow and downflow at the topside ionosphere observed by the EISCAT VHF radar

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