The relationship between suprathermal heavy ion outflow and auroral electron energy deposition: Polar/Ultraviolet Imager and Fast Auroral Snapshot/Time‐of‐Flight Energy Angle Mass Spectrometer observations

Wilson, G. R.; Ober, D. M.; Lund, E. J.

doi:10.1029/2000ja000434

Cited by 21 publications

(26 citation statements)

References 23 publications

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“…This can be compared with our earlier results [Wilson et al, 2001] for just O + where we saw a factor of about 200 increase in the flux for a similar change in luminosity. Part of the reason for this difference is that our earlier results consisted mainly of data from the premidnight sector while this data set includes many points from the dawn sector.…”

Section: First Approachmentioning

confidence: 54%

“…However, these events can be observed any time the aurora is active, regardless of whether or not a nearby onset can be identified. In our work with some of the same data [Wilson et al, 2001] we note a strong correlation between large O + upflow fluxes observed by FAST and the intensity of the aurora at the foot point of the field line on which the fluxes were observed. For an increase from 0 to 4 kR in the LBH-l band (1600 -1800 Å ) emissions, the O + outflow flux can increase by a factor of 100 [Wilson et al, 2001].…”

mentioning

confidence: 48%

“…The basic approach here is to sort the ion flux measurements by the intensity of the aurora at the foot point of the field line, along the lines of what was done in our previous study [Wilson et al, 2001]. When the luminosity exceeds 0.1 kR this approach can readily identify points that are in the auroral zone.…”

Section: First Approachmentioning

confidence: 99%

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Nightside auroral zone and polar cap ion outflow as a function of substorm size and phase

Wilson¹,

Ober²,

Germany

et al. 2004

J. Geophys. Res.

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[1] Because the high latitude ionosphere is an important source of plasma for the magnetosphere under active conditions, we have undertaken a study of the way ion outflow from the nightside auroral zone and polar cap respond to substorm activity. We have combined data from the Ultraviolet Imager (UVI) on Polar with ion upflow measurements from the TEAMS instrument on the FAST spacecraft to construct a picture of ion upflow from these regions as a function of substorm size and as a function of time relative to substorm onset. We use data taken during solar minimum in the northern hemisphere between December 1996 and February 1997. We find that the total nightside auroral zone ion outflow rate (averaged over substorm phase) depends on the size of the substorm, increasing by about a factor of 10 for both O + and H + from the smallest to the largest substorms in our study. The combined outflow rate from both the polar cap and the nightside auroral zone goes up by a factor of 7 for both ions for the same change in conditions. Regardless of storm size, the nightside auroral zone outflow rate increases by about a factor of 2 after onset, reaching its peak level after about 20 min. These results indicate that the change in the nightside auroral zone ion outflow rate that accompanies substorm onset is not as significant as the change from low to high magnetic activity. As a consequence, the prompt increase in the near earth plasma sheet energy density of O + and H + ions that accompanies onset [Daglis and Axford, 1996] is likely due to local energization of ions already present rather than to the sudden arrival and energization of fresh ionospheric plasma.

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Section: First Approachmentioning

confidence: 54%

mentioning

confidence: 48%

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Nightside auroral zone and polar cap ion outflow as a function of substorm size and phase

Wilson¹,

Ober²,

Germany

et al. 2004

J. Geophys. Res.

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120

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“…Ion outflows as a function of location, season, solar and magnetic activity have been studied in several papers (see e.g. Yau and Andre, 1997, and Wilson et al, 2001, and references therein). Substorm effects on ion outflows have been studied by Wilson et al (2004), who find that regardless of substorm size, the nightside auroral zone outflow rate increases by about a factor of 2 after onset, reaching its peak level after about 20 min.…”

Section: Phenomena Occurring In the Vicinity Of The Nightside Polar Cmentioning

confidence: 99%

“…Yau and Andre, 1997, and Wilson et al, 2001, and references therein). Substorm effects on ion outflows have been studied by Wilson et al (2004), who find that regardless of substorm size, the nightside auroral zone outflow rate increases by about a factor of 2 after onset, reaching its peak level after about 20 min. The PSBL, especially during substorms, is an important source of upflowing ions in the nightside (Tung et al, 2001;Ober et al, 2001).…”

Section: Phenomena Occurring In the Vicinity Of The Nightside Polar Cmentioning

confidence: 99%

EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary

Aikio

Pitkänen

Fontaine³

et al. 2008

Ann. Geophys.

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Abstract. The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromsø (66.6 • cgmLat) and Longyearbyen (75.2 • cgmLat) on 27 February 2004 by using the coordinated EIS-CAT incoherent scatter radar, MIRACLE magnetometer and Cluster satellite measurements. During the late substorm expansion/early recovery phase, the polar cap boundary (PCB) made zig-zag-type motion with amplitude of 2.5 • cgmLat and period of about 30 min near magnetic midnight. We suggest that the poleward motions of the PCB were produced by bursts of enhanced reconnection at the near-Earth neutral line (NENL). The subsequent equatorward motions of the PCB would then represent the recovery of the merging line towards the equilibrium state (Cowley and Lockwood, 1992). The observed bursts of enhanced westward electrojet just equatorward of the polar cap boundary during poleward expansions were produced plausibly by particles accelerated in the vicinity of the neutral line and thus lend evidence to the Cowley-Lockwood paradigm.During the substorm recovery phase, the footpoints of the Cluster satellites at a geocentric distance of 4.4 R E mapped in the vicinity of EISCAT measurements. Cluster data indicate that outflow of H + and O + ions took place within the plasma sheet boundary layer (PSBL) as noted in some earlier studies as well. We show that in this case the PSBL corresponded to a region of enhanced electron temperature in the ionospheric F region. It is suggested that the ion outflow originates from the F region as a result of increased ambipolar diffusion. At higher altitudes, the ions could be furtherCorrespondence to: A. T. Aikio (anita.aikio@oulu.fi) energized by waves, which at Cluster altitudes were observed as BBELF (broad band extra low frequency) fluctuations.The four-satellite configuration of Cluster revealed a sudden poleward expansion of the PSBL by 2 • during ∼5 min. The beginning of the poleward motion of the PCB was associated with an intensification of the downward FAC at the boundary. We suggest that the downward FAC sheet at the PCB is the high-altitude counterpart of the Earthward flowing FAC produced in the vicinity of the magnetotail neutral line by the Hall effect (Sonnerup, 1979) during a short-lived reconnection pulse.

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Relationship between auroral substorm and ion upflow in the nightside polar ionosphere

et al. 2013

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[1] We investigated ionospheric ion upflow during an auroral substorm using simultaneous European Incoherent Scatter radar and IMAGE satellite data. Approximately 6 min after an initial brightening identified with data from the IMAGE wideband imaging camera instrument, ion upflow was seen and the electron temperature became enhanced, too. The ion upflow, with a velocity of about 150 m/s, and the electron temperature enhancement lasted for about 25 min. During the poleward expansion phase, surges of large upward ion velocity and flux, and high ion and electron temperatures occurred over Longyearbyen. The upward ion flux reached 2 × 10 14 m À2 s À1. Naturally enhanced ion-acoustic lines (NEIALs) were seen near the poleward edge of the expanded auroral oval both near the end of expansion phase 17 min after onset and also later in the recovery phase. The NEIALs seemed to be accompanied by another type of enhanced echoes, obliquely to the local geomagnetic field. Data from the Low Energy Neutral Atom instrument on the IMAGE satellite show that energetic neutral oxygen reaches the IMAGE satellite about 40 min after the initial brightening, and oxygen continues to get detected during the recovery phase. We propose that ion upflow at the poleward edge of the auroral oval during the expansion phase is related to ion/neutral outflow with energy below 18-27 eV, whereas during the recovery phase of a substorm upward ions are accelerated up to about 60 eV and flow out in the entire polar region.

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The relationship between suprathermal heavy ion outflow and auroral electron energy deposition: Polar/Ultraviolet Imager and Fast Auroral Snapshot/Time‐of‐Flight Energy Angle Mass Spectrometer observations

Cited by 21 publications

References 23 publications

Nightside auroral zone and polar cap ion outflow as a function of substorm size and phase

Nightside auroral zone and polar cap ion outflow as a function of substorm size and phase

EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary

Relationship between auroral substorm and ion upflow in the nightside polar ionosphere

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