Birkeland current system key parameters derived from Iridium observations: Method and initial validation results

Anderson, B. J.; Takahashi, Kazue; Kamei, T.; Waters, C. L.; Toth, Bruce A.

doi:10.1029/2001ja000080

Cited by 109 publications

(120 citation statements)

References 23 publications

(37 reference statements)

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“…For this event the DMSP F15 satellite did not observe significant magnetic or electric fields following 06:00 UT until after 15:00 UT even though the Iridium key parameter data (cf. Anderson et al, 2002) show that the magnetic perturbations were present throughout this time from 75 • MLAT to the pole and were in fact stronger than during the interval analyzed here. If one based analysis on F15 only one would not have detected energy transport prior to 15:00 UT even though it appears to have been more intense than that reported here.…”

Section: Discussion and Summarymentioning

confidence: 94%

High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

et al. 2005

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Abstract. We present a case study of a prolonged interval of strongly northward orientation of the interplanetary magnetic field on 16 July 2000, 16:00-19:00 UT to characterize the energy exchange between the magnetosphere and ionosphere for conditions associated with minimum solar windmagnetosphere coupling. With reconnection occurring tailward of the cusp under northward IMF conditions, the reconnection dynamo should be separated from the viscous dynamo, presumably driven by the Kelvin-Helmholtz (KH) instability. Thus, these conditions are also ideal for evaluating the contribution of a viscous interaction to the coupling process. We derive the two-dimensional distribution of the Poynting vector radial component in the northern sunlit polar ionosphere from magnetic field observations by the constellation of Iridium satellites together with drift meter and magnetometer observations from the Defense Meteorological Satellite Program (DMSP) F13 and F15 satellites. The electromagnetic energy flux is then compared with the particle energy flux obtained from auroral images taken by the far-ultraviolet (FUV) instrument on the Imager for Magnetopause to Aurora Global Exploration (IMAGE) spacecraft. The electromagnetic energy input to the ionosphere of 51 GW calculated from the Iridium/DMSP observations is eight times larger than the 6 GW due to particle precipitation all poleward of 78 • MLAT. This result indicates that the energy transport is significant, particularly as it is concentrated in a small region near the magnetic pole, even under conditions traditionally considered to be quiet and is dominated by the electromagnetic flux. We estimate the contributions of the high and mid-latitude dynamos to both the Birkeland currents and electric potentials finding that highlatitude reconnection accounts for 0.8 MA and 45 kV while we attribute <0.2 MA and ∼5 kV to an interaction at lower latitudes having the sense of a viscous interaction. Given that these conditions are ideal for the occurrence of the KH instability at the magnetopause and hence the viscous interaction, Correspondence to: H. Korth (haje.korth@jhuapl.edu) this result suggests that the viscous interaction is a small contributor to coupling solar wind energy to the magnetosphereionosphere system.

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Section: Discussion and Summarymentioning

confidence: 94%

High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

et al. 2005

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“…It is now possible to regularly have such simultaneous observations because of the global coverage of Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) [Anderson et al, 2000[Anderson et al, , 2002.…”

Section: à2mentioning

confidence: 99%

“…Magnetic perturbations measured by the Iridium satellites have been processed using spherical harmonic procedures [Anderson et al, 2000[Anderson et al, , 2002] to obtain the FACs distribution at 1 h magnetic local time (MLT) and 1°magnetic latitude resolutions from 40°to 90°MLAT in AACGM coordinates.…”

Section: Amperementioning

confidence: 99%

On the generation/decay of the storm‐enhanced density plumes: Role of the convection flow and field‐aligned ion flow

et al. 2014

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Storm-enhanced density (SED) plumes are prominent ionospheric electron density increases at the dayside middle and high latitudes. The generation and decay mechanisms of the plumes are still not clear. We present observations of SED plumes during six storms between 2010 and 2013 and comprehensively analyze the associated ionospheric parameters within the plumes, including vertical ion flow, field-aligned ion flow and flux, plasma temperature, and field-aligned currents, obtained from multiple instruments, including GPS total electron content (TEC), Poker Flat Incoherent Scatter Radar (PFISR), Super Dual Auroral Radar Network, and Active Magnetosphere and Planetary Electrodynamics Response Experiment. The TEC increase within the SED plumes at the PFISR site can be 1.4-5.5 times their quiet time value. The plumes are usually associated with northwestward E × B flows ranging from a couple of hundred m s À1 to > 1 km s À1. Upward vertical flows due to the projection of these E × B drifts are mainly responsible for lifting the plasma in sunlit regions to higher altitude and thus leading to plume density enhancement. The upward vertical flows near the poleward part of the plumes are more persistent, while those near the equatorward part are more patchy. In addition, the plumes can be collocated with either upward or downward field-aligned currents (FACs) but are usually observed equatorward of the peak of the Region 1 upward FAC, suggesting that the northwestward flows collocated with plumes can be either subauroral or auroral flows. Furthermore, during the decay phase of the plume, large downward ion flows, as large as~200 m s À1, and downward fluxes, as large as 10 14 m À2 s À1, are often observed within the plumes. In our study of six storms, enhanced ambipolar diffusion due to an elevated pressure gradient is able to explain two of the four large downward flow/flux cases, but this mechanism is not sufficient for the other two cases where the flows are of larger magnitude. For the latter two cases, enhanced poleward thermospheric wind is suggested to be another mechanism for pushing the plasma downward along the field line. These downward flows should be an important mechanism for the decay of the SED plumes. IntroductionDuring enhanced geomagnetic activity periods, in particular storms, significant electron density enhancements are often observed in the midlatitude and subauroral region, which are named storm-enhanced densities (SEDs) [Foster, 1993]. Often, SEDs extend northwestward to higher latitudes and form a plume. This plume can occasionally be entrained into the cusp region and then enter the polar cap, where it is termed the tongueof-ionization (TOI) or, if it is not continuous, a polar cap patch, depending on the shape and spatial coverage of the high-density region there [e.g., Foster et al., 2005;Moen et al., 2013]. The SED plume is suggested to be the ionospheric projection of a plasmaspheric plume in the magnetospheric equatorial plane . Within the magnetosphere, plasmaspheric plumes can play...

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“…The Active Magnetosphere and Planetary Electrodynamics Experiment (AMPERE) infers maps of field-aligned current density in the northern and southern polar regions at a 10 min cadence, fitting a spherical harmonic expansion to the horizontal magnetic perturbations measured by the 66 spacecraft of the Iridium® telecommunications constellation (Anderson et al 2000(Anderson et al , 2002Waters et al 2001;Green et al 2006). The spacecraft are arranged in six polar orbital planes uniformly spaced in local time, eleven spacecraft to each orbit at an altitude of 780 km.…”

Section: Datasetsmentioning

confidence: 99%

Overview of Solar Wind–Magnetosphere–Ionosphere–Atmosphere Coupling and the Generation of Magnetospheric Currents

Milan¹,

Clausen²,

Coxon³

et al. 2017

Earth's Magnetic Field

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We review the morphology and dynamics of the electrical current systems of the terrestrial magnetosphere and ionosphere. Observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) over the three years 2010 to 2012 are employed to illustrate the variability of the field-aligned currents that couple the magnetosphere and ionosphere, on timescales from minutes to years, in response to the impact of solar wind disturbances on the magnetosphere and changes in the level of solar illumination of the polar ionospheres. The variability is discussed within the context of the occurrence of magnetic reconnection between the solar wind and terrestrial magnetic fields at the magnetopause, the transport of magnetic flux within the magnetosphere, and the onset of magnetic reconnection in the magnetotail. The conditions under which the currents are expected to be weak, and hence minimally contaminate measurements of the internallyproduced magnetic field of the Earth, are briefly outlined.

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Birkeland current system key parameters derived from Iridium observations: Method and initial validation results

Cited by 109 publications

References 23 publications

High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF

On the generation/decay of the storm‐enhanced density plumes: Role of the convection flow and field‐aligned ion flow

Overview of Solar Wind–Magnetosphere–Ionosphere–Atmosphere Coupling and the Generation of Magnetospheric Currents

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