 |
| Titel |
On the efficiency of rocket-borne particle detection in the mesosphere |
| VerfasserIn |
J. Hedin, J. Gumbel, M. Rapp |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 7, no. 14 ; Nr. 7, no. 14 (2007-07-16), S.3701-3711 |
| Datensatznummer |
250005133
|
| Publikation (Nr.) |
 copernicus.org/acp-7-3701-2007.pdf |
|
|
|
|
|
| Zusammenfassung |
| Meteoric smoke particles have been proposed as a key player in the formation
and evolution of mesospheric phenomena. Despite their apparent importance
still very little is known about these particles. Important questions
concern the smoke number density and size distribution as a function of
altitude as well as the fraction of charged particles. Sounding rockets are
used to measure smoke in situ, but aerodynamics has remained a major
challenge. Basically, the small smoke particles tend to follow the gas flow
around the payload rather than reaching the detector if aerodynamics is not
considered carefully in the detector design. So far only indirect evidence
for the existence of meteoric smoke has been available from measurements of
heavy charge carriers. Quantitative ways are needed that relate these
measured particle population to the atmospheric particle population. This
requires in particular knowledge about the size-dependent,
altitude-dependent and charge-dependent detection efficiency for a given
instrument. In this paper, we investigate the aerodynamics for a typical
electrostatic detector design. We first quantify the flow field of the
background gas, then introduce particles in the flow field and determine
their trajectories around the payload structure. We use two different models
to trace particles in the flow field, a Continuous motion model and a
Brownian motion model. Brownian motion is shown to be of basic importance
for the smallest particles. Detection efficiencies are determined for three
detector designs, including two with ventilation holes to allow airflow
through the detector. Results from this investigation show that rocket-borne
smoke detection with conventional detectors is largely limited to altitudes
above 75 km. The flow through a ventilated detector has to be relatively
large in order to significantly improve the detection efficiency. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|