Some low‐altitude cusp dependencies on the interplanetary magnetic field

Newell, P. T.; Meng, C.‐I.; Sibeck, D. G.; Lepping, R. P.

doi:10.1029/ja094ia07p08921

Cited by 338 publications

(297 citation statements)

References 48 publications

Supporting

Mentioning

250

Contrasting

Order By: Relevance

“…6a) shown here is seen in previous surveys of cusp precipitation (e.g. Burch, 1973;Newell et al, 1989) and in 630 nm cusp aurora (Horwitz and Akasofu, 1977;Sandholt et al, 1999) and is expected as the low-altitude signature of magnetopause erosion by magnetic reconnection during southward IMF.…”

Section: Drift Shellssupporting

confidence: 64%

Dawn-dusk asymmetry in particles of solar wind origin within the magnetosphere

et al. 2001

View full text Add to dashboard Cite

Abstract. Solar wind/magnetosheath plasma in the magnetosphere can be identified using a component that has a higher charge state, lower density and, at least soon after their entry into the magnetosphere, lower energy than plasma from a terrestrial source. We survey here observations taken over 3 years of He 2+ ions made by the Magnetospheric Ion Composition Sensor (MICS) of the Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE) instrument aboard POLAR. The occurrence probability of these solar wind ions is then plotted as a function of Magnetic Local Time (MLT) and invariant latitude ( ) for various energy ranges. For all energies observed by MICS (1.8-21.4 keV) and all solar wind conditions, the occurrence probabilities peaked around the cusp region and along the dawn flank. The solar wind conditions were filtered to see if this dawnward asymmetry is controlled by the Svalgaard-Mansurov effect (and so depends on the B Y component of the interplanetary magnetic field, IMF) or by Fermi acceleration of He 2+ at the bow shock (and so depends on the IMF ratio B X /B Y ). It is shown that the asymmetry remained persistently on the dawn flank, suggesting it was not due to effects associated with direct entry into the magnetosphere. This asymmetry, with enhanced fluxes on the dawn flank, persisted for lower energy ions (below a "cross-over" energy of about 23 keV) but reversed sense to give higher fluxes on the dusk flank at higher energies. This can be explained by the competing effects of gradient/curvature drifts and the convection electric field on ions that are convecting sunward on re-closed field lines. The lower-energy He 2+ ions E × B drift dawnwards as they move earthward, whereas the higher energy ions curvature/gradient drift towards dusk. The convection electric field in the tail is weaker for northward IMF. Ions then need less energy to drift to the dusk flank, so that the cross-over energy, at which the asymmetry changes sense, is reduced.

show abstract

Section: Drift Shellssupporting

confidence: 64%

Dawn-dusk asymmetry in particles of solar wind origin within the magnetosphere

et al. 2001

View full text Add to dashboard Cite

show abstract

“…The northern cusp, displaced into the post-noon sector, is thus connected with the southern cusp which is displaced pre-noon. This is the sense of displacement of the main cusp as determined by Newell et al (1989) from DMSP particle precipitation data. A burst of magnetopause reconnection starting at noon (component reconnection in the subsolar region) will first map into the post-noon sector in the Northern Hemisphere, followed by propagation away from this centre both west and east, towards higher latitudes.…”

Section: Discussionmentioning

confidence: 99%

Multi-site observations of the association between aurora and plasma convection in the cusp/polar cap during a southeastward(By ~ |Bz|) IMF orientation

et al. 2003

View full text Add to dashboard Cite

Abstract. In a case study we demonstrate the spatiotemporal structure of aurora and plasma convection in the cusp/polar cap when the interplanetary magnetic field (IMF) B z < 0 and B y |B z | (clock angle in GSM Y − Z plane: 135 • ). This IMF orientation elicited a response different from that corresponding to strongly northward and southward IMF. Our study of this "intermediate state" is based on a combination of ground observations of optical auroral emissions and ionospheric plasma convection. Utilizing allsky cameras at NyÅlesund, Svalbard and Heiss Island (Russian arctic), we are able to monitor the high-latitude auroral activity within the ∼10:00-15:00 MLT sector. Information on plasma convection is obtained from the SuperDARN radars, with emphasis placed on line of sight observations from the radar situated in Hankasalmi, Finland (Cutlass). A central feature of the auroral observations in the cusp/polar cap region is a ∼30-min long sequence of four brightening events, some of which consists of latitudinally and longitudinally separated forms, which are found to be associated with pulsed ionospheric flows in merging and lobe convection cells. The auroral/convection events may be separated into different forms/cells and phases, reflecting a spatiotemporal evolution of the reconnection process on the dayside magnetopause. The initial phase consists of a brightening in the postnoon sector (∼12:00-14:00 MLT) at ∼73 • MLAT, accompanied by a pulse of enhanced westward convection in the postnoon merging cell. Thereafter, the event evolution comprises two phenomena which occur almost simultaneously: (1) westward expansion of the auroral brightening (equatorward boundary intensification) across noon, into the ∼10:00-12:00 MLT sector, where the plasma convection subsequently turns almost due north, in the convecCorrespondence to: P. E. Sandholt (p.e.sandholt@fys.uio.no) tion throat, and where classical poleward moving auroral forms (PMAFs) are observed; and (2) auroral brightening at slightly higher latitudes (∼75 • MLAT) in the postnoon lobe cell, with expansion towards noon, giving rise to a clear cusp bifurcation. The fading phase of PMAFs is accompanied by a "patch" of enhanced (∼1 km/s) poleward-directed merging cell convection at high latitudes (75-82 • MLAT), e.g. more than 500 km poleward of the cusp equatorward boundary. The major aurora/convection events are recurring at ∼5-10 min intervals.

show abstract

“…At these altitudes the cusp is generally identified by intense fluxes of low-energy ions, mostly in the few hundred eV to few keV range, but intense fluxes of low-energy By [Newell et al, 1989;Aparicio et al, 1991]. It may therefore appear somewhat untimely that despite the contemporary view of a strong electromagnetic coupling between the magnetosphere and the solar wind there are still certain issues where "old" gas dynamics appear to play an equally important role for the morphology and dynamics of the cusp.…”

Section: Introductionmentioning

confidence: 99%