Two types of energy‐dispersed ion structures at the plasma sheet boundary

Sauvaud, J. A.

doi:10.1029/2003ja010333

Cited by 48 publications

(79 citation statements)

References 57 publications

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“…These Polar results were later confirmed with ion statistical data from the polar orbiting Interball-Auroral satellite by Sauvaud and Kovrazhkin (2004), data taken at altitudes of 2 to 3 R E , and with some event data (at R>4 R E ) from the Cluster satellites as well (Sauvaud and Kovrazhkin, 2004;Keiling et al, 2004). The Sauvaud and Kovrazhkin study treats the stepping up kind of events as a separate type (VDIS), based in part on their occurring during reduced magnetic activity and in association with less energetic electrons.…”

Section: Introductionsupporting

confidence: 64%

“…The source can be expected to be as close as the ∼19 R E Cluster apogees at times, or closer still (e.g. Lennartsson et al, 2001;Sauvaud and Kovrazhkin, 2004).…”

Section: Discussionmentioning

confidence: 99%

“…A large fraction of the plasma sheet-lobe boundary crossings in both the Polar (Lennartsson et al, 2001) and the Interball-Auroral (Sauvaud and Kovrazhkin, 2004) surveys, about 40% and 50%, respectively, did not reveal distinct energy dispersion in the proton spectra. One important reason, as deduced from the Polar TIMAS spectra, is that the proton flux and number density often have very steep gradients transverse to the magnetic field lines, with scale sizes comparable to local keV proton gyroradii.…”

Section: Introductionmentioning

confidence: 99%

“…The temporal variations include the same kind of proton energy dispersion that is familiar from observations closer to Earth (e.g. Lennartsson et al, 2001;Sauvaud and Kovrazhkin, 2004) and will be described briefly below.…”

Section: Plasma Sheet Filamentsmentioning

confidence: 99%

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Cluster view of the plasma sheet boundary layer and bursty bulk flow connection

2009

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Abstract. The high-latitude boundaries of the plasma sheet (PSBL) are dynamic latitude zones of recurring and transient (minutes to tens of minutes) earthward and magnetic fieldaligned bursts of plasma, each being more or less confined in longitude as well, whose ionic component is dominated by protons with flux, energies and density that are consistent with a central plasma sheet (CPS) source at varying distance (varying rates of energy time dispersion), sometimes as close as the ∼19 R E Cluster apogees, or closer still. The arguably most plausible source consists of so called "bursty bulk flows" (BBFs), i.e. proton bulk flow events with large, positive and bursty GSE v x . Known mainly from CPS observations made at GSE x>−30 R E , the BBF type events probably take place much further downtail as well. What makes the BBFs an especially plausible source are (1) their earthward bulk flow, which helps explain the lack of distinctive latitudinal PSBL energy dispersion, and (2) their association with a transient strong increase of the local tail B z component ("local dipolarization"). The enhanced B z provides intermittent access to higher latitudes for the CPS plasma, resulting in local density reductions in the tail midplane, as illustrated here by proton data from the Cluster CIS CODIF instruments. Another sign of kinship between the PSBL bursts and the BBFs is their similar spatial fine structure. The PSBL bursts have prominent filaments aligned along the magnetic field with transverse flux gradients that are often characterized by local ∼10 keV proton gyroradii scale size (or even smaller), as evidenced by Cluster measurements. The same kind of fine structure is also found during Cluster near-apogee traversals of the tail midplane, as illustrated here and implied by recently published statistics on BBFs obtained with Cluster multipoint observations at varying satellite separations. Altogether, the Cluster observations Correspondence to: O. W. Lennartsson (lenn@mailhost.spasci.com) described here mesh rather well with theories about so called plasma sheet "bubbles," i.e. earthward drifting closed magnetic flux tubes with reduced particle pressure and enhanced magnetic field strength at their apex. It is argued that such bubbles may be initiated by localized diamagnetic instabilities.

show abstract

Section: Introductionsupporting

confidence: 64%

“…The source can be expected to be as close as the ∼19 R E Cluster apogees at times, or closer still (e.g. Lennartsson et al, 2001;Sauvaud and Kovrazhkin, 2004).…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Plasma Sheet Filamentsmentioning

confidence: 99%

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Cluster view of the plasma sheet boundary layer and bursty bulk flow connection

2009

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“…It is possible and even likely that different types of ion beams are generated by different mechanisms under different conditions. For example, it was found that the active and quiet magnetotail can lead to ion beams with different properties giving justification for the existence of several energization mechanisms (Sauvaud and Kovrazhkin, 2004). In spite of ample observations, little has been conclusively confirmed about the impact of PSBL ion beams on auroral and magnetotail dynamics.…”

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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Time‐dispersed ion signatures observed in the Martian magnetosphere by MAVEN

Halekas

McFadden

Connerney

et al. 2015

Geophysical Research Letters

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Mars Atmosphere and Volatile EvolutioN mission's (MAVEN) high‐cadence measurements reveal the frequent occurrence of ion energy dispersion events inside the Martian magnetosphere. The systematics of observed dispersion signatures suggest time dispersion of a broad source spectrum over a flight distance of a few thousand kilometers and disfavor mechanisms involving spatial dispersion. Pickup of heavy planetary ions in strong variable electric fields provides one potential mechanism that could produce the observed time dispersion signatures. The periodicity of many observed dispersion signatures, with frequencies near the upstream proton cyclotron frequency, suggests a possible role for low‐frequency plasma waves in accelerating the observed ions from a source near the induced magnetospheric boundary to the observation location inside the magnetospheric tail lobes. The observed dispersion signatures may provide a new way to track the flow of energy from the upstream region through the magnetosphere and the role of waves in driving the escape of ions from the atmosphere.

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Two types of energy‐dispersed ion structures at the plasma sheet boundary

Cited by 48 publications

References 57 publications

Cluster view of the plasma sheet boundary layer and bursty bulk flow connection

Cluster view of the plasma sheet boundary layer and bursty bulk flow connection

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

Time‐dispersed ion signatures observed in the Martian magnetosphere by MAVEN

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