Mesospheric dust and its secondary effects as observed by the ESPRIT payload
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<sup>9</sup> e m<sup...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2009-03-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/27/1119/2009/angeo-27-1119-2009.pdf |
| Summary: | 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<sup>9</sup> e m<sup>−3</sup> 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>I</I><sub>DC</sub>=−10<sup>−11</sup> 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<sup>8</sup> e m<sup>−3</sup>. This demonstrates
that PMSE can be formed even if the ratio of the dust charge density
to the electron density <I>P</I>=<I>N<sub>d</sub>Z<sub>d</sub> /n_e</I>≲0.01.
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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<sub><I>i</I></sub>≳20–35°. This again lends support to
the suggested model for NLC and PMSE dust particles (Havnes and
Næsheim, 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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| ISSN: | 0992-7689 1432-0576 |