Sensitivity of meteoric smoke distribution to microphysical properties and atmospheric conditions

Megner, Linda; Rapp, Markus; Gumbel, J.

doi:10.5194/acpd-6-5357-2006

Cited by 30 publications

(68 citation statements)

References 24 publications

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“…If the original small Hunten particles are also covered by a condensed ice-layer, this will lower the accretion rate and therefore also require a higher density N H , in order to yield the same embedded density. Recent calculations on the ablation and condensation of meteoric material confirm that densities of N H U comparable to our requirements may well be present (Megner et al, 2006). Considering the capture of the smallest Hunten particles with a radius of just a fraction of a nanometer, they find that densities of N H U (0.2 nm)∼10 11 m −3 may be present.…”

Section: Discussionmentioning

confidence: 84%

On the secondary charging effects and structure of mesospheric dust particles impacting on rocket probes

Havnes

Næsheim

2007

Ann. Geophys.

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Abstract. The dust probe DUSTY, first launched during the summer of 1994 (flights ECT-02 and ECT-07) from Andøya Rocket Range, northern Norway, was the first probe to unambiguously detect heavy charged mesospheric aerosols, from hereon referred to as dust. In ECT-02 the probe detected negatively charged dust particles in the height interval of 83 to 88.5 km. In this flight, the lower grid in the detector (Grid 2) measures both positive and negative currents in various regions, and we find that the relationship between the current measurements of Grid 2 and the bottom plate can only be explained by influence from secondary charge production on Grid 2. In ECT-07, which had a large coning, positive currents reaching the top grid of the probe were interpreted as due to the impact of positively charged dust particles. We have now reanalyzed the data from ECT-07 and arrived at the conclusion that the measured positive currents to this grid must have been mainly due to secondary charging effects from the impacting dust particles. The grid consists of a set of parallel wires crossed with an identical set of wires on top of it, and we find that if the observed currents were created from the direct impact of charged dust particles, then they should be very weakly modulated at four times the rocket spin rate ω R . Observations show, however, that the observed currents are strongly modulated at 2ω R . We cannot reproduce the observed large modulations of the impact currents in the dust layer if the currents are due only to the transfer of the charges on the impacted dust particles. Based on the results of recent ice cluster impact secondary charging experiments by Tomsic (2003), which found that a small fraction of the ice clusters, when impacting with nearly grazing incidence, carried away one negative charge −1e, we have arrived at the conclusion that similar, but significantly more effective, charging effects must be predominantly responsible for the positive currents measured by the top grid in ECT-07 and their large rotational modulation at 2ω R .Correspondence to: O. Havnes (ove.havnes@phys.uit.no) Since the secondary effect is dependent on the size of the impacting dust, this opens up for the possibility of mapping the relative dust sizes throughout a dust layer by comparing the observed direct and secondary currents.

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Section: Discussionmentioning

confidence: 84%

On the secondary charging effects and structure of mesospheric dust particles impacting on rocket probes

Havnes

Næsheim

2007

Ann. Geophys.

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“…5 where it is argued that the occurrence of positive particles at the smallest sizes is more consistent with the growth of ice on positively charged condensation nuclei than with either photoelectric charging or the capture of positive ions by neutral aerosol particles. The condensation nuclei being ions rather than meteoric dust is also supported by recent circulation models that show number densities of sufficiently-large meteoric particles that are too low to account for the number densities of charged aerosol particles (Megner et al, 2006(Megner et al, , 2008Bardeen et al, 2008). Section 6 is a short summary and conclusion.…”

Section: Introductionmentioning

confidence: 79%

“…Recent modeling of meteoric smoke production and circulation shows that the smoke particles are carried away from the summer pole by circulation (Megner et al, 2006(Megner et al, , 2008Bardeen et al, 2008). Models for condensation require a minimum particle radius near 0.5 nm for typical conditions (Keesee, 1989;Megner et al, 2008;Gumbel and Megner, 2009;Winkler et al, 2008).…”

Section: Positive Charge On the Smallest Particlesmentioning

confidence: 99%

Mass analysis of charged aerosol particles in NLC and PMSE during the ECOMA/MASS campaign

et al. 2009

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Abstract. MASS (Mesospheric Aerosol Sampling Spectrometer) is a multichannel mass spectrometer for charged aerosol particles, which was flown from the Andøya Rocket Range, Norway, through NLC and PMSE on 3 August 2007 and through PMSE on 6 August 2007. The eight-channel analyzers provided for the first time simultaneous measurements of the charge density residing on aerosol particles in four mass ranges, corresponding to ice particles with radii <0.5 nm (including ions), 0.5-1 nm, 1-2 nm, and >3 nm (approximately). Positive and negative particles were recorded on separate channels. Faraday rotation measurements provided electron density and a means of checking charge density measurements made by the spectrometer. Additional complementary measurements were made by rocket-borne dust impact detectors, electric field booms, a photometer and ground-based radar and lidar. The MASS data from the first flight showed negative charge number densities of 1500-3000 cm −3 for particles with radii >3 nm from 83-88 km approximately coincident with PMSE observed by the ALWIN radar and NLC observed by the ALOMAR lidar. For particles in the 1-2 nm range, number densities of positive and negative charge were similar in magnitude (∼2000 cm −3 ) and for smaller particles, 0.5-1 nm in radius, positive charge was dominant. The occurrence of positive charge on the aerosol particles of the smallest size and predominately negative charge on the particles of largest size suggests that nucleCorrespondence to: S. Knappmiller (knappmil@colorado.edu) ation occurs on positive condensation nuclei and is followed by collection of negative charge during subsequent growth to larger size. Faraday rotation measurements show a bite-out in electron density that increases the time for positive aerosol particles to be neutralized and charged negatively. The larger particles (>3 nm) are observed throughout the NLC region, 83-88 km, and the smaller particles are observed primarily at the high end of the range, 86-88 km. The second flight into PMSE alone at 84-88 km, found only small number densities (∼500 cm −3 ) of particles >3 nm in a narrow altitude range, 86.5-87.5 km. Both positive (∼2000 cm −3 ) and negative (∼4500 cm −3 ) particles with radii 1-2 nm were detected from 85-87.5 km.

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“…The reason for the comparatively high value of the impact angles found in the experiments, compared to those required for mesospheric dust particles, is most likely that the pure ice particles in the experiments will totally sublimate at lower impact angles (Tomsic, 2001). On the other hand, mesospheric ice particles may contain many small meteoric particles (Rosinski and Snow, 1961;Hunten et al, 1980;Megner et al, 2006) which probably do not sublimate. Havnes and Naesheim (2007) suggested that mesospheric dust particles fragment during impact and that much or all of the ice within which the meteoric smoke particles are embedded, sublimates, while the meteoric smoke particles carry away charge from the surface where the impact takes place.…”

Section: Secondary Charge Production In the Nlc/pmse And Pmse Layermentioning

confidence: 99%

“…The required effectivity for the secondary charge production of the mesospheric dust is much larger than what is observed for pure water-ice particles in experiments. This, combined with a modelling of the impacts on the dust probe grids as a function of payload spin rotation angle, led Havnes and Naesheim (2007) to conclude that a model for the mesospheric dust could be a fairly loosely bound ice particle in which a considerable number of small meteoric particles (Rosinski and Snow, 1961;Hunten et al, 1980;Megner et al, 2006) of radius 1 nm are embedded. Upon impact, the large dust particle was assumed to fragment into many small subparticles each containing one or more meteoric smoke particle.…”

Section: Introductionmentioning

confidence: 99%

Mesospheric dust and its secondary effects as observed by the ESPRIT payload

Havnes

Surdal²,

Philbrick

2009

Ann. Geophys.

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Abstract. The dust detector on the ESPRIT rocket detected two extended dust/aerosol layers during the launch on 1 July 2006. The lower layer at height ∼81.5-83 km coincided with a strong NLC and PMSE layer. The maximum dust charge density was ∼−3.5×10 9 e m −3 and the dust layer was characterized by a few strong dust layers where the dust charge density at the upper edges changed by factors 2-3 over a distance of 10 m, while the same change at their lower edges were much more gradual. The upper edge of this layer is also sharp, with a change in the probe current from zero to I DC =−10 −11 A over ∼10 m, while the same change at the low edge occurs over ∼500 m. The second dust layer at ∼85-92 km was in the height range of a comparatively weak PMSE layer and the maximum dust charge density was ∼−10 8 e m −3 . This demonstrates that PMSE can be formed even if the ratio of the dust charge density to the electron density P =N d Z d /n e 0.01.In spite of the dust detector being constructed to reduce possible secondary charging effects from dust impacts, it was found that they were clearly present during the passage through both layers. The measured secondary charging effects confirm recent results that dust in the NLC and PMSE layers can be very effective in producing secondary charges with up to ∼50 to 100 electron charges being rubbed off by one impacting large dust particle, if the impact angle is θ i 20-35 • . This again lends support to the suggested model for NLC and PMSE dust particles (Havnes and Naesheim, 2007) as a loosely bound water-ice clump interspersed with a considerable number of sub-nanometer-sized meteoric smoke particles, possibly also contaminated with meteoric atomic species.

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Sensitivity of meteoric smoke distribution to microphysical properties and atmospheric conditions

Cited by 30 publications

References 24 publications

On the secondary charging effects and structure of mesospheric dust particles impacting on rocket probes

On the secondary charging effects and structure of mesospheric dust particles impacting on rocket probes

Mass analysis of charged aerosol particles in NLC and PMSE during the ECOMA/MASS campaign

Mesospheric dust and its secondary effects as observed by the ESPRIT payload

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