Excitation of transient lobe cell convection and auroral arc at the cusp poleward boundary during a transition of the interplanetary magnetic field from south to north

Sandholt, P. E.; Farrugia, Charles J.; Cowley, S. W. H.; Lester, M.; Cerisier, J. C.

doi:10.5194/angeo-19-487-2001

Cited by 18 publications

(23 citation statements)

References 20 publications

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“…This is consistent with the radar observations in Figures 2 and 3. The Lshell-aligned flow in Figure 2 might be partially caused by lobe reconnection, similar to the observations during transition of the IMF from southward to northward reported by Sandholt et al [12]. This is illustrated by the diagram in Figure 4, which shows that the dayside reconnection (Southern Hemisphere) and lobe reconnection (Northern Hemisphere) may be simultaneous.…”

Section: Interpretation and Discussionsupporting

confidence: 66%

Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity V Y

Wei

Zong

et al. 2011

Chin. Sci. Bull.

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It is believed that a southward interplanetary magnetic field (IMF) is mainly responsible for the energy input from solar wind into the magnetosphere. This paper presents an unusual case of strong anti-sunward plasma flow (up to 2 km/s) in the polar cap ionosphere and large cross-polar cap potential (CPCP) during a period of horizontal IMF (|B Z | < 2 nT) observed by both ACE (at the L1 point) and Geotail (on the dusk flank of the magnetosheath). The CPCP is even higher than that under preceding B Z ≈ -23 nT. Furthermore, GOES8 observed that the magnetosheath field turns northward as the anti-sunward plasma flow and CPCP start to increase, which implies that the magnetosheath field interacting with the Earth's magnetopause has significantly rotated and differs from the IMF observed by ACE and Geotail. In accordance with previous theoretical work, we suggest that the magnetic field line draping produces a southward magnetosheath field and enhances anti-sunward plasma flow and the CPCP. magnetic field draping, ionospheric convection, magnetosphere-ionosphere coupling Citation: Wei Y, Zong Q G, Pu Z Y, et al. Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity V Y .

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Section: Interpretation and Discussionsupporting

confidence: 66%

Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity V Y

Wei

Zong

et al. 2011

Chin. Sci. Bull.

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“…Auroral arcs at the poleward boundary of the northward IMF cusp were investigated immediately after a northward IMF turning [ Sandholt et al , 2002]. Coordinated ground (aurora) and satellite observations (particle precipitation and field‐aligned current information from DMSP F13) of multiple arcs (1–5 keV electrons) excited at the poleward boundary of the northward IMF cusp aurora were found where the field‐aligned current is directed out of the ionosphere (see also [ Sandholt et al , 2001]. These papers indicate that a similar auroral phenomenon as discussed in the present paper is excited under normal solar wind dynamic pressure conditions during “cusp transition states” associated with northward turnings of the IMF.…”

Section: Discussionmentioning

confidence: 99%

Properties of localized, high latitude, dayside aurora

Frey

Immel

et al. 2003

J. Geophys. Res.

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[1] The FUV instrument on the IMAGE spacecraft frequently observes intense ultraviolet (UV) emission from a localized dayside region poleward of the general auroral oval location. One type of these emissions has been described as the signature of direct proton precipitation into the cusp after lobe reconnection during northward interplanetary magnetic field (IMF) and high solar wind dynamic pressure periods . Here we describe a completely different type of high latitude aurora, which does not show any signature of precipitating protons. It also occurs during northward IMF conditions however, only during periods of very low solar wind dynamic pressure. It occurs at a much higher geomagnetic latitude than the normal cusp location and only during periods of positive IMF B y . The intensity of the UV emission is somewhat anti-correlated with the solar wind dynamic pressure, much in contrast to the cusp emission. The brightness of the localized emission changes rapidly on time scales between 30 and 70 minutes without corresponding changes in solar wind properties. Coincident measurements by the FAST spacecraft verify that this is not the cusp, that ion precipitation is absent in these regions, and that strong precipitation of field-aligned accelerated electrons causes the aurora. We interpret this aurora as the optical signature of electron precipitation in the upward leg of a current system which closes the downward leg of the current system into the cusp in the ionosphere.

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“…In the present case this may be inferred from the strong green line intensity. We suggest two possible reasons: (i) different acceleration mechanisms at high and low magnetopause latitudes Østgaard et al, 2003), and (ii) the presence of polar arcs at the cusp poleward boundary during northward IMF orientation (Sandholt et al, 2001(Sandholt et al, , 2002b. The latter is due to current continuity requirements (see, e.g.…”

Section: Elements Of Interpretationmentioning

confidence: 99%

Dayside aurora and the role of IMF ∣By∣/∣Bz∣: detailed morphology and response to magnetopause reconnection

2004

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Abstract. We document the detailed spatio-temporal structure of the dayside aurora during intervals of ongoing dayside magnetopause reconnection, primarily during interplanetary magnetic field (IMF) B z ≤0 conditions. The present study is based on ground auroral observations in combination with particle precipitation data from a DMSP spacecraft. We describe auroral forms corresponding to the following particle precipitation regimes identified by Newell and Meng (1994): (i) central plasma sheet (CPS), (ii) precipitation void, (iii) dayside boundary plasma sheet (BPS), and (iv) cusp (LLBL/cusp/mantle). Two distinctly different auroral configurations are observed, corresponding to different regimes of the IMF clock angle (θ ) and the |B y |/|B z | ratio. Two regimes are defined. In regime (I) θ lies within ∼ 90-135 • and |B y |/|B z |>1 (B y -dominated), while in regime (II) θ is in the range 135 • -180 • and |B y |/|B z |<1 (B z -dominated). Within regime (I) the auroral response to reconnection events typically progresses from lower to higher latitudes in stages as indicated below: (A) equatorward boundary intensifications (EBIs): sequential brightenings of closely spaced, fragmented, rayed bands (BPS aurora) within the ∼08:00-15:00 MLT sector, each of which are moving noonward/sunward, (B) poleward moving auroral forms (PMAFs): forms expanding westward from the postnoon side (B y >0) and later appearing as a poleward expanding form in the convection throat in the ∼09:00-12:00 MLT sector, with a fading phase in the regime of mantle precipitation. During strongly southward IMF conditions (regime II), the intense PMAF activity is replaced by a more latitudinally restricted, but longitudinally wide aurora of moderate intensity. The latter auroral state is accompanied by a 2-cell convection pattern which is rather symmetrical about noon. This state is very different from the convection/FAC configuration present during IMF regime (I), with its strong zonal flows (convection current), more intense FAC sheets and PMAF activity in the midday sector. The strong Correspondence to: P. E. Sandholt (p.e.sandholt@fys.uio.no) IMF regulation of the dayside BPS aurora, consisting of keV electrons, and its location with respect to the green line auroral gap (precipitation void), indicate that it is an important signature of the reconnection process, located on open boundary layer field lines. The observed longitudinal bifurcation of the auroral brightenings (EBIs) preceding PMAFs is consistent with antiparallel magnetopause reconnection.

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Excitation of transient lobe cell convection and auroral arc at the cusp poleward boundary during a transition of the interplanetary magnetic field from south to north

Cited by 18 publications

References 20 publications

Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity V Y

Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity V Y

Properties of localized, high latitude, dayside aurora

Dayside aurora and the role of IMF ∣<i>B<sub>y</sub></i>∣/∣<i>B<sub>z</sub></i>∣: detailed morphology and response to magnetopause reconnection

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Excitation of transient lobe cell convection and auroral arc at the cusp poleward boundary during a transition of the interplanetary magnetic field from south to north

Cited by 18 publications

References 20 publications

Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity V Y

Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity V Y

Properties of localized, high latitude, dayside aurora

Dayside aurora and the role of IMF ∣&lt;i&gt;B&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt;∣/∣&lt;i&gt;B&lt;sub&gt;z&lt;/sub&gt;&lt;/i&gt;∣: detailed morphology and response to magnetopause reconnection

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Dayside aurora and the role of IMF ∣<i>B<sub>y</sub></i>∣/∣<i>B<sub>z</sub></i>∣: detailed morphology and response to magnetopause reconnection