Polar/Toroidal Imaging Mass‐Angle Spectrograph survey of earthward field‐aligned proton flows from the near‐midnight tail

Lennartsson, O. W.; Trattner, K. J.; Collin, H. L.; Peterson, W. K.

doi:10.1029/2000ja003014

Cited by 19 publications

(42 citation statements)

References 39 publications

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“…[4] This study is an outgrowth of recent observations of velocity-dispersed ion flows in the tail by the Toroidal Imaging Mass-Angle Spectrograph (TIMAS) instrument on the Polar satellite [Lennartsson et al, 2001]. These appear to be the same kind of flows that have been equated with a plasma sheet high-latitude ''boundary layer'' in the literature, the PSBL [e.g., Forbes et al, 1981;Eastman et al, 1985;Bosqued et al, 1993;Onsager and Mukai, 1995 and references therein].…”

Section: Present Contextmentioning

confidence: 99%

“…fragmented by spatial inhomogeneities, tend to repeat a pattern of energy dispersion of a few minutes duration, indicating a down-tail source distance of a few tens of R E [Lennartsson et al, 2001]. This duration is typical, but slower dispersion does occur.…”

Section: Smpmentioning

confidence: 99%

“…[9] Figure 1 shows, at 12-s time resolution (paired Polar spin cycles), H + and O + number flux spectra during two SMP consecutive 2-hour near-midnight crossings from the central plasma sheet into the northern lobe (one orbit apart; see Figure 1 in Lennartsson et al [2001] for typical orbital geometry). The spectra of main interest begin about 1925 UT on 23 October and 1245 UT on 24 October.…”

Section: Ion Observationsmentioning

confidence: 99%

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In situ Polar observation of transverse cold‐ion acceleration: Evidence that electric field generation is a hot‐ion finite gyroradii effect

Lennartsson

2003

J. Geophys. Res.

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[1] Recent results with the Polar TIMAS instrument (ion mass spectrometer) have revealed that earthward magnetic field-aligned and velocity-dispersed flows of 1-to 33-keV protons (and other ions) from the outer magnetosphere are inherently ''blast-like'' and exhibit a complex filamentary structure where transverse scale sizes may often be a few proton gyroradii. These velocity-dispersed protons (and accompanying hot electrons) have been found to have a close association with enhanced large pitch angle outflow of accelerated (sometimes to more than 10 keV) ionospheric ions (H + , O + , and He + ) at Polar. Theoretical considerations suggest a mechanism by which the difference in gyroradii between hot ions and electrons in earthward plasma bursts generates charge imbalance and strong transverse electric fields at density gradients, as the bursts move into an increasingly strong magnetic field, which in turn accelerate the ambient cold ions. Model electric fields greater than 1 V m À1 at Polar are readily generated with density gradient scale lengths of a few earth radii in an equatorial source region of the bursts, assuming that the magnetic moments of the burst protons are preserved. The nonadiabatic acceleration of cold ions may act to reduce these fields to the ca 0.1-V m À1 amplitude and few-second period fluctuations actually observed. Sample TIMAS data are shown to be consistent with the transverse acceleration of cold O + ions to keV energy on a timescale of less than a single gyroperiod.

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Section: Present Contextmentioning

confidence: 99%

Section: Smpmentioning

confidence: 99%

Section: Ion Observationsmentioning

confidence: 99%

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In situ Polar observation of transverse cold‐ion acceleration: Evidence that electric field generation is a hot‐ion finite gyroradii effect

Lennartsson

2003

J. Geophys. Res.

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“…[14] As illustrated by Lennartsson et al [2001], the ion flux observed in the Polar frame of reference, by the TIMAS instrument, may vary substantially on a timescale of 12 s, often by orders of magnitude, suggesting large variations on even shorter timescales. Since the flow density sums contain terms from different spin phases, the apparent flow may reflect spatial gradients rather than local anisotropy.…”

Section: False Outward Flow Samplingsmentioning

confidence: 99%

Solar wind control of Earth's H⁺ and O⁺ outflow rates in the 15‐eV to 33‐keV energy range

2004

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[1] Earth's high-latitude outflow of H + and O + ions has been examined with the Toroidal Imaging Mass-Angle Spectrograph instrument on the Polar satellite in the 15-eV to 33-keV energy range over an almost 3-year period near solar minimum (1996)(1997)(1998). This outflow is compared with solar wind plasma and interplanetary magnetic field (IMF) data from the Wind spacecraft, the latter having been time shifted to the subsolar magnetopause and averaged for 15 min prior to each sampling of Earth's magnetic fieldaligned ion flow densities. When the flow data are arranged according to the polarity of the IMF B z (in GSM coordinates) and limited to times with B z > 3 nT or B z < À3 nT, the total rate of ion outflow is seen to be significantly enhanced with negative B z , typically by factors of 2.5-3 for the O + and 1.5-2 for the H + , more than previously reported from similar but less extensive comparisons. With either IMF B z polarity the rate of ion outflow is well correlated with the solar wind energy flow density, especially well with the density of kinetic energy flow. The rate of ion outflow within the instrument's energy range is a strong function of the Polar satellite altitude, increasing almost threefold from perigee (R $ 2 R E ) toward apogee (R $ 4-9 R E ) for O + ions, i.e., up to 10 26 ions s À1 or more per hemisphere. The apogee enhancement may be still larger for the H + , but it is obscured by mantle flow of cusp origin solar H + . Ion mean energy also increases with altitude, leading to about a twentyfold increase in the O + energy flow rate from Polar perigee to apogee altitude, reaching values of 20 GW or more per hemisphere. While the perigee outflow of H + has little or no seasonal modulation, in terms of ions s À1 the O + outflow rates at both altitudes do increase during local summer and so does the rate of cusp origin H + flow near apogee. The latter rate, in fact, has very similar seasonal modulation as the O + rates, suggesting that it has a significant influence on the O + outflow.

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“…Many studies have characterized their properties from low altitudes out to the distant magnetotail (e.g., Forbes et al, 1981;Eastman et al, 1984;Parks et al, 1984Parks et al, , 1998Takahashi and Hones, 1988;Zelenyi et al, 1990;Bosqued et al, 1993;Hirahara et al, 1997;Sauvaud et al, 1999;Sergeev et al, 2000;Lennartsson et al, 2001;Grigorenko et al, 2002;Kazama and Mukai, 2003). To explain their existence, various processes have been proposed for the energization of ions in the Published by Copernicus GmbH on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

Energy-dispersed ions in the plasma sheet boundary layer and associated phenomena: Ion heating, electron acceleration, Alfvén waves, broadband waves, perpendicular electric field spikes, and auroral emissions

Keiling

Parks

Rème³

et al. 2006

Ann. Geophys.

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Abstract. Recent Cluster studies reported properties of multiple energy-dispersed ion structures in the plasma sheet boundary layer (PSBL) that showed substructure with several well separated ion beamlets, covering energies from 3 keV up to 100 keV (Keiling et al., 2004a, b). Here we report observations from two PSBL crossings, which show a number of identified one-to-one correlations between this beamlet substructure and several plasma-field characteristics: (a) bimodal ion conics (<1 keV), (b) field-aligned electron flow (<1 keV), (c) perpendicular electric field spikes (∼20 mV/m), (d) broadband electrostatic ELF wave packets (<12.5 Hz), and (e) enhanced broadband electromagnetic waves (<4 kHz). The one-to-one correlations strongly suggest that these phenomena were energetically driven by the ion beamlets, also noting that the energy flux of the ion beamlets was 1-2 orders of magnitude larger than, for example, the energy flux of the ion outflow. In addition, several more loosely associated correspondences were observed within the extended region containing the beamlets: (f) electrostatic waves (BEN) (up to 4 kHz), (g) traveling and standing ULF Alfvén waves, (h) field-aligned currents (FAC), and (i) auroral emissions on conjugate magnetic field lines. Possible generation scenarios for these phenomena are discussed. In conclusion, it is argued that the free energy of magnetotail ion beamlets drove a variety of phenomena and that the spatial fine structure of the beamlets dictated the locaCorrespondence to: A. Keiling (keiling@ssl.berkeley.edu) tions of where some of these phenomena occurred. This emphasizes the notion that PSBL ion beams are important for magnetosphere-ionosphere coupling. However, it is also shown that the dissipation of electromagnetic energy flux (at altitudes below Cluster) of the simultaneously occurring Alfvén waves and FAC was larger (FAC being the largest) than the dissipation of beam kinetic energy flux, and thus these two energy carriers contributed more to the energy transport on PSBL field lines from the distant magnetotail to the ionosphere than the ion beams.

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Polar/Toroidal Imaging Mass‐Angle Spectrograph survey of earthward field‐aligned proton flows from the near‐midnight tail

Cited by 19 publications

References 39 publications

In situ Polar observation of transverse cold‐ion acceleration: Evidence that electric field generation is a hot‐ion finite gyroradii effect

In situ Polar observation of transverse cold‐ion acceleration: Evidence that electric field generation is a hot‐ion finite gyroradii effect

Solar wind control of Earth's H⁺ and O⁺ outflow rates in the 15‐eV to 33‐keV energy range

Energy-dispersed ions in the plasma sheet boundary layer and associated phenomena: Ion heating, electron acceleration, Alfvén waves, broadband waves, perpendicular electric field spikes, and auroral emissions

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Polar/Toroidal Imaging Mass‐Angle Spectrograph survey of earthward field‐aligned proton flows from the near‐midnight tail

Cited by 19 publications

References 39 publications

In situ Polar observation of transverse cold‐ion acceleration: Evidence that electric field generation is a hot‐ion finite gyroradii effect

In situ Polar observation of transverse cold‐ion acceleration: Evidence that electric field generation is a hot‐ion finite gyroradii effect

Solar wind control of Earth's H+ and O+ outflow rates in the 15‐eV to 33‐keV energy range

Energy-dispersed ions in the plasma sheet boundary layer and associated phenomena: Ion heating, electron acceleration, Alfvén waves, broadband waves, perpendicular electric field spikes, and auroral emissions

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Solar wind control of Earth's H⁺ and O⁺ outflow rates in the 15‐eV to 33‐keV energy range