The nightside poleward boundary of the auroral oval as seen by DMSP and the Ultraviolet Imager

Baker, J. B.; Clauer, C. R.; Ridley, A. J.; Papitashvili, V. O.; Brittnacher, M.; Newell, P. T.

doi:10.1029/1999ja000363

Cited by 48 publications

(74 citation statements)

References 27 publications

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“…This poleward boundary can be measured using Polar UVI LBHl and IMAGE FUV WIC data. Baker et al (2000) compared the auroral boundary as measured by Polar UVI LBHl to that of DMSP data. They found that a cutoff brightness of approximately 4.3 photons/cm 2 /sr (∼130 Rayleighs) compares well to the DMSP open-closed boundary.…”

Section: Methodsmentioning

confidence: 99%

Balanced reconnection intervals: four case studies

2008

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Abstract. During steady magnetospheric convection (SMC) events the magnetosphere is active, yet there are no data signatures of a large scale reconfiguration, such as a substorm. While this definition has been used for years it fails to elucidate the true physics that is occurring within the magnetosphere, which is that the dayside merging rate and the nightside reconnection rate balance. Thus, it is suggested that these events be renamed Balanced Reconnection Intervals (BRIs). This paper investigates four diverse BRI events that support the idea that new name for these events is needed. The 3–4 February 1998 event falls well into the classic definition of an SMC set forth by Sergeev et al. (1996), while the other challenge some previous notions about SMCs. The 15 February 1998 event fails to end with a substorm expansion and concludes as the magnetospheric activity slowly quiets. The third event, 22–23 December 2000, begins with a slow build up of magnetospheric activity, thus there is no initiating substorm expansion. The last event, 17 February 1998, is more active (larger AE, AL and cross polar cap potential) than previously studied SMCs. It also has more small scale activity than the other events studied here.

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Section: Methodsmentioning

confidence: 99%

Balanced reconnection intervals: four case studies

2008

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“…Consequently, it is desirable to compare the open-closed PPBs with estimates of the OCB made by other instruments that have greater spatial coverage and higher temporal resolution. Studies to date have included comparisons with boundaries measured by ground-based imagers (Blanchard et al, 1995(Blanchard et al, , 1997 and UltraViolet Imagers (UVI) on spacecraft (Kauristie et al, 1999;Baker et al, 2000). The most comprehensive investigation of this type is that of Carbary et al (2003).…”

Section: Introductionmentioning

confidence: 99%

A statistical comparison of SuperDARN spectral width boundaries and DMSP particle precipitation boundaries in the morning sector ionosphere

et al. 2005

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Abstract. Determining reliable proxies for the ionospheric signature of the open-closed field line boundary (OCB) is crucial for making accurate ionospheric measurements of many magnetospheric processes (e.g. magnetic reconnection). This study compares the latitudes of Spectral Width Boundaries (SWBs), identified in the morning sector ionosphere using the Super Dual Auroral Radar Network (SuperDARN), with Particle Precipitation Boundaries (PPBs) determined using the low-altitude Defense Meteorological Satellite Program (DMSP) spacecraft, in order to determine whether the SWB represents a good proxy for the ionospheric projection of the OCB. The latitudes of SWBs and PPBs were identified using automated algorithms applied to 5 years (1997)(1998)(1999)(2000)(2001) of data measured in the 00:00-12:00 Magnetic Local Time (MLT) range. A latitudinal difference was measured between each PPB and the nearest SWB within a ±10 min Universal Time (UT) window and within a ±1 h MLT window. The results show that the SWB represents a good proxy for the OCB close to midnight (∼00:00-02:00 MLT) and noon (∼08:00-12:00 MLT), but is located some distance (∼2 • -4 • ) equatorward of the OCB across much of the morning sector ionosphere (∼02:00-08:00 MLT). On the basis of this and other studies we deduce that the SWB is correlated with the poleward boundary of auroral emissions in the Lyman-Birge-Hopfield "Long" (LBHL) UV emission range and hence, that spectral width is inversely correlated with the energy flux of precipitating electrons. We further conclude that the combination of two factors may explain the spatial distribution of spectral width values in the polar ionospheres. The small-scale structure of the convection electric field leads to an enhancement in spectral width in regions close to the OCB, whereas increases in ionospheric conductivity (relating to the level of incident electron energy flux) lead to a reduction in spectral width in regions just equatorward of the OCB.

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“…It marks the ionospheric trace of the surface separating the closed field line region from the so-called open field lines close to the geomagnetic poles. Only space-borne optical imaging by satellites provides the possibility to observe the PCB globally (Baker et al, 2000;Milan et al, 2003;Hubert et al, 2006). In addition, several local methods exist, based on observations of the auroral emissions (Blanchard et al, 1995), in situ particle detection (Newell et al, 1996a,b), analysis of coherent radar backscatter (Chisham et al, 2004), or electron temperature from incoherent scatter radar (Østgaard et al, 2005;Aikio et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

IMF effect on the polar cap contraction and expansion during a period of substorms

et al. 2013

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The polar cap boundary (PCB) location and motion in the nightside ionosphere has been studied by using measurements from the EISCAT radars and the MIRACLE magnetometers during a period of four substorms on 18 February 2004. The OMNI database has been used for observations of the solar wind and the Geotail satellite for magnetospheric measurements. In addition, the event was modelled by the GUMICS-4 MHD simulation. The simulation of the PCB location was in a rather good agreement with the experimental estimates at the EISCAT longitude. During the first three substorm expansion phases, neither the local observations nor the global simulation showed any poleward motions of the PCB, even though the electrojets intensified. Rapid poleward motions of the PCB took place only in the early recovery phases of the substorms. Hence, in these cases the nightside reconnection rate was locally higher in the recovery phase than in the expansion phase.

In addition, we suggest that the IMF B_z component correlated with the nightside tail inclination angle and the PCB location with about a 17-min delay from the bow shock. By taking the delay into account, the IMF northward turnings were associated with dipolarizations of the magnetotail and poleward motions of the PCB in the recovery phase. The mechanism behind this effect should be studied further

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The nightside poleward boundary of the auroral oval as seen by DMSP and the Ultraviolet Imager

Cited by 48 publications

References 27 publications

Balanced reconnection intervals: four case studies

Balanced reconnection intervals: four case studies

A statistical comparison of SuperDARN spectral width boundaries and DMSP particle precipitation boundaries in the morning sector ionosphere

IMF effect on the polar cap contraction and expansion during a period of substorms

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