Magnetospheric source region of discrete auroras inferred from their relationship with isotropy boundaries of energetic particles

Yahnin, A. G.; Sergeev, V. A.; Gvozdevsky, B. B.; Vennerstrøm, S.

doi:10.1007/s005850050513

Cited by 11 publications

(14 citation statements)

References 11 publications

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“…Some authors consider the source located inside the current sheet, on stretched field lines (e.g. Yahnin et al, 1997), while some others argue that the source of substorm auroras is situated on dipole-like magnetic field lines (e.g. Lazutin, 1986;Shiokawa et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Indirect mapping of the source of the oppositely directed fast plasma flows in the plasma sheet onto the auroral display

et al. 2006

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Abstract. Data from Polar and Geotail spacecraft are combined to investigate the relationship between locations of active auroras and the magnetotail plasma sheet region where reversed fast plasma flows are generated during substorms. Using the magnetospheric magnetic field model, it is shown that at the beginning of the tailward fast flow the ionospheric footprint of the spacecraft measuring the flow tends to be located poleward of the auroral bulge. The spacecraft within the earthward flow is mapped equatorward of the poleward edge of the auroral bulge. We conclude that a source of the fast plasma flows is conjugated with the poleward edge of the auroral bulge. Analysis of the behavior of the plasma and the magnetic field in the vicinity of the source of the diverging flows allows us to conclude that the source region, interpreted as the magnetic reconnection site, coincides with the region of the cross-tail current reduction, and the tailward propagation of the region is associated with the tailward propagation of the current disruption front.

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Section: Introductionmentioning

confidence: 99%

Indirect mapping of the source of the oppositely directed fast plasma flows in the plasma sheet onto the auroral display

et al. 2006

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“…Arcs are a pervasive morphology, occurring at essentially all local times (e.g. Stringer and Belon (1967); Gustafsson (1967)), from the poleward boundary of the oval equatorward to the proton and/or electron isotropic boundaries (Lyons et al, 1988;Yahnin et al, 1997). Statistical studies indicate that arc occurrence peaks on the night side (i.e.…”

Section: Introductionmentioning

confidence: 99%

Diurnal auroral occurrence statistics obtained via machine vision

Syrjäsuo

Donovan

2004

Ann. Geophys.

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Abstract. Modern ground-based digital auroral All-Sky Imager (ASI) networks capture millions of images annually. Machine vision techniques are widely utilised in the retrieval of images from large data bases. Clearly, they can play an important scientific role in dealing with data from auroral ASI networks, facilitating both efficient searches and statistical studies. Furthermore, the development of automated techniques for identifying specific types of aurora opens up the potential of ASI control software that would change instrument operation in response to evolving geophysical conditions. In this paper, we describe machine vision techniques that we have developed for use on large auroral image data sets. We present the results of application of these techniques to a 350 000 image subset of the CANOPUS Gillam ASI in the years 1993-1998. In particular, we obtain occurrence statistics for auroral arcs, patches, and Omega-bands. These results agree with those of previous manual auroral surveys.

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“…tor (TED) and Medium Energy Proton and Electron Detector (MEPED) are described in Evans and Greer (2000). It should be noted that 1 erg/cm 2 sec str could be proxy for visible aurora (Yahnin et al, 1997). By 0640 UT, the cross polar cap potential is already increased (Fig.…”

Section: Simulation Resultsmentioning

confidence: 93%

A study of the storm event on October 21–22, 1999 by the MHD simulation

Park

Ogino

2006

Earth Planet Sp

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We carried out a high resolution three-dimensional magnetohydrodynamic (MHD) simulation of the interaction between the solar wind and the Earth's magnetosphere during a strong magnetic storm on October 21-22, 1999. The input to the simulation was from WIND solar wind observations. As the IMF is strongly southward (−20 nT to −30 nT) for 6 hours, the geomagnetic field lines in the dayside magnetopause are eroded to the geosynchronous orbit (GEO) region by reconnection. The associated magnetic flux is transferred from the dayside magnetosphere to the tail. The reconnection region still appears near GEO region on the dayside magnetopause, even though the IMF B z component becomes small or northward, because of the influence of the strong IMF B y (30 nT). IMF lines can successively reconnect with the naked and large geomagnetic field line in the dayside flank regions. Thus, the cross polar cap potential is maintained to be large value and convection in the ionosphere is enhanced. The cross polar cap potential is governed by IMF B y as well as B z (φ ∼ 250 kV for B z ∼ −20 nT and φ ∼ 300 kV for B z ∼ −30 nT), and it saturates during the strong southward IMF. A large energy flux enters the ionosphere at very low latitudes (50• ) and the inner edge of the plasma sheet becomes very close to the Earth (X = −3.2 R E ) for a strong magnetic storms. The open-closed boundary extends to 60• latitudes on the nightside, 72• on the dayside, 62• on dawn, and 66• on dusk. Enhanced energy flux appears at low latitudes (50• ) on the nightside in simulation. Moreover, the energy flux in the dusk region (19 MLT) appears down to 55• latitude in simulation, which is consistent with the low latitude boundary of the 0.02-20 keV particles detected by TED of the NOAA-15. A convective electric field, which is penetrating to the Earth-side of the NENL, is almost comparable to that of the solar wind. The present MHD simulation study give reasonable results even for extreme conditions and thereby its usefulness is demonstrated as a physical model for space weather studies.

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Magnetospheric source region of discrete auroras inferred from their relationship with isotropy boundaries of energetic particles

Cited by 11 publications

References 11 publications

Indirect mapping of the source of the oppositely directed fast plasma flows in the plasma sheet onto the auroral display

Indirect mapping of the source of the oppositely directed fast plasma flows in the plasma sheet onto the auroral display

Diurnal auroral occurrence statistics obtained via machine vision

A study of the storm event on October 21–22, 1999 by the MHD simulation

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