Intermittent thermal plasma acceleration linked to sporadic motions of the magnetopause, first Cluster results

Sauvaud, J. A.; Lundin, R.; Rème, H.; McFadden, J. P.; Carlson, C. W.; Parks, G. K.; Möbius, E.; Kistler, L. M.; Klecker, B.; Amata, E.; DiLellis, A. M.; Formisano, V.; Bosqued, J. M.; Dandouras, I.; Décréau, Pierrette; Dunlop, M. W.; Eliasson, L.; Korth, A.; Lavraud, B.; McCarthy, Michael

doi:10.5194/angeo-19-1523-2001

Cited by 57 publications

(75 citation statements)

References 27 publications

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“…Dense ionospheric ion bursts present in the shell immediately earthward to the magnetopause have been reported previously in observations by Cluster (Sauvaud et al, 2001) and Polar (Chen and Moore, 2004). Their density reached ∼1-100 cm −3 and the velocity reached ∼100 km/s in the direction perpendicular to the local magnetic field.…”

Section: Discussionmentioning

confidence: 66%

Coordinated polar spacecraft, geosynchronous spacecraft, and ground-based observations of magnetopause processes and their coupling to the ionosphere

Chen

Zheng

et al. 2004

Ann. Geophys.

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Abstract. In this paper, we present in-situ observations of processes occurring at the magnetopause and vicinity, including surface waves, oscillatory magnetospheric field lines, and flux transfer events, and coordinated observations at geosynchronous orbit by the GOES spacecraft, and on the ground by CANOPUS and 210 • Magnetic Meridian (210 MM) magnetometer arrays. On 7 February 2002, during a high-speed solar wind stream, the Polar spacecraft was skimming the magnetopause in a post-noon meridian plane for ∼3 h. During this interval, it made two short excursions and a few partial crossings into the magnetosheath and observed quasi-periodic cold ion bursts in the region adjacent to the magnetopause current layer. The multiple magnetopause crossings, as well as the velocity of the cold ion bursts, indicate that the magnetopause was oscillating with an ∼6-min period. Simultaneous observations of Pc5 waves at geosynchronous orbit by the GOES spacecraft and on the ground by the CANOPUS magnetometer array reveal that these magnetospheric pulsations were forced oscillations of magnetic field lines directly driven by the magnetopause oscillations. The magnetospheric pulsations occurred only in a limited longitudinal region in the post-noon dayside sector, and were not a global phenomenon, as one would expect for global field line resonance. Thus, the magnetopause oscillations at the source were also limited to a localized region spanning ∼4 h in local time. These observations suggest that it is unlikely that the Kelvin-Helmholz instability and/or fluctuations in the solar wind dynamic pressure were the direct driving mechanisms for the observed boundary oscillations.Correspondence to: G. Le (guan.le@nasa.gov) Instead, the likely mechanism for the localized boundary oscillations was pulsed reconnection at the magnetopause occurring along the X-line extending over the same 4-h region. The Pc5 band pressure fluctuations commonly seen in high-speed solar wind streams may modulate the reconnection rate as an indirect cause of the observed Pc5 pulsations. During the same interval, two flux transfer events were also observed in the magnetosphere near the oscillating magnetopause. Their ground signatures were identified in the CANOPUS data. The time delays of the FTE signatures from the Polar spacecraft to the ground stations enable us to estimate that the longitudinal extent of the reconnection X-line at the magnetopause was ∼43 • or ∼5.2 R E . The coordinated in-situ and ground-based observations suggest that FTEs are produced by transient reconnection taking place along a single extended X-line at the magnetopause, as suggested in the models by Scholer (1988) and Southwood et al. (1988). The observations from this study suggest that the reconnection occurred in two different forms simultaneously in the same general region at the dayside magnetopause: 1) continuous reconnection with a pulsed reconnection rate, and 2) transient reconnection as flux transfer events.

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Section: Discussionmentioning

confidence: 66%

Coordinated polar spacecraft, geosynchronous spacecraft, and ground-based observations of magnetopause processes and their coupling to the ionosphere

Chen

Zheng

et al. 2004

Ann. Geophys.

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“…[3] Observations from the Cluster mission [Sauvaud et al, 2001] have cited the presence of dense populations of thermal ionospheric ions in a region adjacent to the magnetopause on the magnetospheric side, following weak magnetic activity. Recurrent motions of the magnetopause produced the appearance of ionospheric ions with energies in the 5 -1000 eV range.…”

Section: Introductionmentioning

confidence: 99%

Observations of the geopause at the equatorial magnetopause: Density and temperature

Chandler

Moore

2003

Geophysical Research Letters

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Magnetic flux tubes containing plasmaspheric ion density and composition have been observed in the region between the classical plasmapause and the magnetopause. New observations show that these ion distributions exist at the equatorial, post‐noon magnetopause. Comparison to observations of similar distributions at geosynchronous orbit and to simulations leads to the conclusion that these ions are convected from these regions to the magnetopause. This represents an extension of the geopause to the outer edge of the magnetosphere on the dayside. The presence of ion densities >10cm−3 in this region must have profound impact on the nature of plasma processes that occur there.

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“…However, outside the events, the ion densities are lower than the electron densities. That may be due to the presence of cold ions hidden to the CIS instruments when the ion flow velocity is low (Sauvaud et al, 2001). As discussed above (Fig.…”

Section: Single-point Observationsmentioning

confidence: 99%

Cluster observations of a structured magnetospheric cusp

et al. 2006

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Abstract. On 18 April 2002 the Cluster spacecraft crossed through the northern outer magnetospheric cusp region during 16:25-17:55 UT when the solar wind dynamic pressure was rather low (<2 nPa) and IMF B z was more negative than IMF B y . The Cluster data from the FGM, CIS, PEACE, EFW, WHISPER and STAFF instruments reveal that the cusp is structured with three anti-sunward ion flow events of durations ≈1.5, 17.5 and 19.0 min, with bulk plasma flow roughly parallel to the magnetopause toward north. The ion and electron densities within the events are much greater than those outside. The zonal electric field in the ion flow events turns eastward as expected from V ×B effect. The sharp inward boundaries of the ion flow events cross the four spacecraft in one time sequence, and the outward boundaries of the events cross the spacecraft in the reverse time sequence. The observations studied using magnetosphere and magnetopause models suggest that the structured cusp is a temporal feature that arises due to three inward and outward movements of the magnetopause by about 1.5 R E so that Cluster, while crossing through the cusp, happened to be in the magnetosheath (ion flow event) and cusp alternately. The magnetopause moved due to the changes in the solar wind dynamic pressure by up to 100%.

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Intermittent thermal plasma acceleration linked to sporadic motions of the magnetopause, first Cluster results

Cited by 57 publications

References 27 publications

Coordinated polar spacecraft, geosynchronous spacecraft, and ground-based observations of magnetopause processes and their coupling to the ionosphere

Coordinated polar spacecraft, geosynchronous spacecraft, and ground-based observations of magnetopause processes and their coupling to the ionosphere

Observations of the geopause at the equatorial magnetopause: Density and temperature

Cluster observations of a structured magnetospheric cusp

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