Ionospheric signatures of the low-latitude boundary layer under  conditions of northward IMF and small clock angle

Pryse, S. E.; Sims, R. W.; Moen, J.; Oksavik, K.

doi:10.5194/angeo-24-2169-2006

Cited by 4 publications

(4 citation statements)

References 33 publications

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“…Since these tubes are filled with magnetosheath plasma, the process is referred to as magnetosheath plasma "capture" by the geomagnetic field. The concept of lobe reconnection was supported by case studies using in-situ spacecraft measurements (Onsager et al, 2001) and ground based observations (Pryse et al, 2006). The expected consequences of such plasma capture are poleward displacements of the cusp and the open/closed field line boundary (OCFLB) near noon.…”

Section: Introductionmentioning

confidence: 93%

Optical, radar, and magnetic observations of magnetosheath plasma capture during a positive IMF Bz impulse

et al. 2008

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Abstract. We present a multi-instrument study of the ionospheric response to a northward turning of the IMF. The observations were made in the near-noon (11:00 MLT) sector on Svalbard (at 75 • MLAT). The data set includes auroral observations, ionospheric flows obtained from the EISCAT and CUTLASS radars, the spectral width of the HF radar backscatter, particle precipitation and plasma flow data from the DMSP F13 satellite, and Pc1 frequency band pulsations observed by induction magnetometers. Careful collocation of all the observations has been made with the HF radar backscatter located by a ray-tracing procedure utilizing the elevation angle of arrival of the signals and an ionospheric plasma density profile. Prior to IMF turning northward, three auroral arcs were observed at the poleward boundary of the closed llbl, inside the llbl, and in the equatorward part of the llbl, respectively. The northward IMF turning was accompanied by enhanced HF radar returns with a broad Doppler spectrum collocated with the arcs. The auroral arcs shifted poleward whereas the backscatter region moved in the opposite direction, which is consistent, respectively, with reconnection beyond the cusp and the capturing of magnetosheath plasma during northward IMF. Locally, magnetic noise enhancement in the Pc1 frequency band occurred simultaneously with the anomalous radar backscatter, and the absence of such signals at more remote magnetic observatories indicates a local generation of the Pc1 turbulence, which is colloCorrespondence to: V. Safargaleev

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Section: Introductionmentioning

confidence: 93%

Optical, radar, and magnetic observations of magnetosheath plasma capture during a positive IMF Bz impulse

et al. 2008

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“…The three components of the IMF, in GSM coordinates, are shown in panels (b) to (d). The lower panel (e) presents the IMF clock angle, θ, defined as (Pryse et al, 2006),…”

Section: Solar Wind and Imf Observationsmentioning

confidence: 99%

Cusp observations during a sequence of fast IMF BZ reversals

et al. 2009

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Abstract. In recent years, a large number of papers have reported the response of the cusp to solar wind variations under conditions of northward or southward Interplanetary Magnetic Field (IMF) Z-component (B Z ). These studies have shown the importance of both temporal and spatial factors in determining the extent and morphology of the cusp and the changes in its location, connected to variations in the reconnection geometry. Here we present a comparative study of the cusp, focusing on an interval characterised by a series of rapid reversals in the B Z -dominated IMF, based on observations from space-borne and ground-based instrumentation. During this interval, from 08:00 to 12:00 UT on 12 February 2003, the IMF B Z component underwent four reversals, remaining for around 30 min in each orientation. The Cluster spacecraft were, at the time, on an outbound trajectory through the Northern Hemisphere magnetosphere, whilst the mainland VHF and Svalbard (ESR) radars of the EISCAT facility were operating in support of the Cluster mission. Both Cluster and the EISCAT were, on occasion during the interval, observing the cusp region. The series of IMF reversals resulted in a sequence of poleward and equatorward motions of the cusp; consequently Cluster crossed the highaltitude cusp twice before finally exiting the dayside magnetopause, both times under conditions of northward IMF B Z . The first magnetospheric cusp encounter, by all four Cluster spacecraft, showed reverse ion dispersion typical of lobe reconnection; subsequently, Cluster spacecraft 1 and 3 (only) crossed the cusp for a second time. We suggest that, during this second cusp crossing, these two spacecraft were likely to have been on newly closed field lines, which were first reconnected (opened) at low latitudes and later reconnected again (re-closed) poleward of the northern cusp.Correspondence to: H. T. Cai (htcai@whu.edu.cn) At ionospheric altitudes, the latitudinal excursions of the cusp/cleft region in response to the series of the IMF polarity changes were clearly captured by both the ESR and the Pykkvibaer radar of the SuperDARN HF network. The Open-Closed field-line Boundary (OCB) inferred from the HF radar observations underwent latitudinal variations in response to the IMF polarity changes that are in accordance with those predicted by Newell et al. (1989). Furthermore, variations in the ionospheric parameters yielded by the EIS-CAT VHF and ESR radars are basically consistent with inferences drawn from the HF radar observations. We conclude that Cluster spacecraft 1 and 3 crossed the cusp for a second time as a result of the latitudinal migration of the cusp in response to the IMF polarity reversals; at that time, however, the cusp lay poleward of spacecraft 4. Snapshots of the cusp from two DMSP satellite passes provide further support for this interpretation.

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“…The PEACE [28] and CIS [29] HIA data recorded by SC1 are displayed in Figure 2, as well as the lagged IMF clock angle from the ACE satellite in GSE. The clock angle is defined as [30] = tan…”

Section: Observationsmentioning

confidence: 99%

Cluster observations of high-altitude cusp during multiple fast-turning IMF

Cai

Dunlop

et al. 2010

Chin. Sci. Bull.

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Using coordinated observations from the Cluster, DMSP and ESR radar, high-altitude cusp was investigated for a time period characterized by four fast reversals of the IMF B Z . On February 12, 2003, Cluster was flying sunward at duskside over the Northern Hemisphere, across the high-altitude northern cusp twice. Both the two crossings are during steady northward IMF interval, whereas ion fluxes detected during the time period are quite different. The cusp in the first crossing is a "typical" northward-IMF one, with short-lived ion injections of evident "reversed" dispersion signatures. In the second crossing, however, the cusp appears to be a region reminiscent of the Stagnant Exterior Cusp (SEC). In addition, evident upward-flowing O + ion bursts, possibly original from polar ionosphere, are also detected during the second cusp crossing, together with enhancement of trapped magnetospheric-like electron fluxes. We suggest that the SEC-like cusp is likely on newly closed field lines, which were first reconnected (being opened) at low latitudes and later reconnected again (being closed) poleward of the northern cusp. Stagnant Exterior Cusp, magnetic reconnection, interplanetary magnetic field, Cluster Citation:Cai H T, Ma S Y, Dunlop M W, et al. Cluster observations of high-altitude cusp during multiple fast-turning IMF.

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Ionospheric signatures of the low-latitude boundary layer under conditions of northward IMF and small clock angle

Cited by 4 publications

References 33 publications

Optical, radar, and magnetic observations of magnetosheath plasma capture during a positive IMF <I>B<sub>z</sub></I> impulse

Optical, radar, and magnetic observations of magnetosheath plasma capture during a positive IMF <I>B<sub>z</sub></I> impulse

Cusp observations during a sequence of fast IMF <I>B<sub>Z</sub></I> reversals

Cluster observations of high-altitude cusp during multiple fast-turning IMF

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Ionospheric signatures of the low-latitude boundary layer under conditions of northward IMF and small clock angle

Cited by 4 publications

References 33 publications

Optical, radar, and magnetic observations of magnetosheath plasma capture during a positive IMF &lt;I&gt;B&lt;sub&gt;z&lt;/sub&gt;&lt;/I&gt; impulse

Optical, radar, and magnetic observations of magnetosheath plasma capture during a positive IMF &lt;I&gt;B&lt;sub&gt;z&lt;/sub&gt;&lt;/I&gt; impulse

Cusp observations during a sequence of fast IMF &lt;I&gt;B&lt;sub&gt;Z&lt;/sub&gt;&lt;/I&gt; reversals

Cluster observations of high-altitude cusp during multiple fast-turning IMF

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Optical, radar, and magnetic observations of magnetosheath plasma capture during a positive IMF <I>B<sub>z</sub></I> impulse

Optical, radar, and magnetic observations of magnetosheath plasma capture during a positive IMF <I>B<sub>z</sub></I> impulse

Cusp observations during a sequence of fast IMF <I>B<sub>Z</sub></I> reversals