Coordinated ground-based and Cluster observations of large amplitude global magnetospheric oscillations during a fast solar wind speed interval

Mann, I. R.; Voronkov, I.; Dunlop, M. W.; Donovan, E.; Yeoman, T. K.; Milling, D. K.; Wild, J. A.; Kauristie, Kirsti; Amm, O.; Bale, S. D.; Balogh, A.; Viljanen, A.; Opgenoorth, H. J.

doi:10.5194/angeo-20-405-2002

Cited by 56 publications

(52 citation statements)

References 61 publications

(68 reference statements)

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“…Sarafopoulos et al, 2001;Mann et al, 2002). However, in our study, we do not consider the Kelvin-Helmholz instability to be the cause of the observed surface waves and magnetopause oscillations since their occurrence characteristics did not suggest so.…”

Section: Discussionmentioning

confidence: 99%

“…In some cases, reconnection was ruled out and it was concluded that the K-H instability was the most likely excitation mechanism (Sarafoupoulos et al, 2001;Mann et al, 2002;Pitout et al, 2003). The rationale to rule out reconnection is that these observations were either during northward IMF, which does not favor reconnection, or during high-speed solar wind which favors the K-H instability.…”

Section: Introductionmentioning

confidence: 99%

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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: 99%

Section: Introductionmentioning

confidence: 99%

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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“…Internal excitation mechanisms can involve resonance with energetic particle sources (e.g., Southwood et al, 1969), or coupling to fundamental plasma instabilities such as the drift-mirror mode (e.g., Pokhotelov et al, 1985Pokhotelov et al, , 1986Woch et al, 1988;. External FLR sources have been shown to be related to either solar wind discontinuity driven cavity/waveguide modes (e.g., Allan et al, 1986;Wright, 1994) or the Kelvin-Helmholtz instability on the magnetopause flanks (e.g., Southwood, 1974;Chen and Hasegawa, 1974;Southwood, 1985, 1986;Mann et al, 2002;Rae et al, 2005 -herein after referred to as R05). Many of these studies invoked a form of the magnetospheric waveguide in order to explain their results, where the magnetopause forms the outer boundary of the waveguide, and a strong gradient in the Alfvén speed forms the inner boundary for the compressional mode waves.…”

Section: Introductionmentioning

confidence: 99%

Energy deposition in the ionosphere through a global field line resonance

et al. 2007

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Abstract.We present an interval whereby we can estimate the energy dissipation in the ionosphere through an externally-driven field line resonance. In this paper, we utilise an interval described in general by Rae et al. (2005), where the global magnetospheric cavity was shown to be energised via a high solar wind speed stream. Using the ground-based instrumentation available, we estimate the spatial extent of the generated pulsations to be at least 10 • in latitude and 65 • in longitude, a sizeable fraction of the dusksector ionosphere. Using a fortuitous conjunction with the Polar spacecraft, we compare point measurements of the net downward Poynting vector to the estimated Joule heating rate in the ionosphere, and find that model values of the Pedersen conductance are reasonable. In the interval of interest, we estimate the total dissipation rate during a global field line resonance to be comparable to that reported in substorm studies. Previous studies have estimated the total energy deposition via field line resonance to be up to 4% of that deposited during a small substorm. However, in this paper we find that the total energy deposited via Joule heating may actually be 30% or more of the energy deposited in the ionosphere during a substorm cycle using a conservative estimate of the pulsation duration.+

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“…The waves are important because they are thought to cause momentum, energy, and perhaps mass transfer into the magnetosphere. They also may be a source of Pc 5 magnetospheric waves that are believed to energize trapped electrons [e.g., O'Brien and McPherron, 2003;Li and Temerin, 2001;Mann et al, 2002].…”

Section: Introductionmentioning

confidence: 99%

Waves on the dusk flank boundary layer during very northward interplanetary magnetic field conditions: Observations and simulation

et al. 2007

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[1] The Geotail spacecraft made an inbound passage perpendicular to the dusk equatorial magnetopause on 1 August 1998 when the interplanetary magnetic field had been very northward for more than 10 hours. As the spacecraft moved through the low-latitude boundary layer, it detected waves with $3 min period that caused transitions between cool dense magnetosheath plasma and mixed magnetosheath and magnetosphere plasmas. A region of highly fluctuating magnetic fields with variations up to 50 nT/s was observed on leaving the magnetosheath plasma but not on its return to this region. This observation suggests that the boundary region is not laminar but more likely consists of KelvinHelmholtz vortices. Such fluctuations are probably caused by twisting of the field by the vortices, and they could be important in transporting plasma to the magnetosphere where densities of 5/cc were observed. A global MHD simulation of the event reproduced the observed low-frequency waves, their counterclockwise polarization, and a region of high-velocity magnetosheath flow outside the magnetopause. This flow was associated with a decreased density and increased field strength which are characteristics of a plasma depletion layer. When Geotail moved further inward into the magnetosphere, it detected waves that are probably the magnetotail vortices which had been detected earlier by the ISEE spacecraft.

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Coordinated ground-based and Cluster observations of large amplitude global magnetospheric oscillations during a fast solar wind speed interval

Cited by 56 publications

References 61 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

Energy deposition in the ionosphere through a global field line resonance

Waves on the dusk flank boundary layer during very northward interplanetary magnetic field conditions: Observations and simulation

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