SOFIE Measurements of Cosmic Dust in the Mesosphere Mark Hervig GATS Inc.

Dust & Smoke overview Some definitions, just in case… Meteoroid: incoming interplanetary particle Meteorite: surviving portion of meteoroid Micrometeorite: too small to reach the boiling point Smoke: condensed ablation products Cosmic dust particles are constantly entering the Earth’s atmosphere Heating during atmospheric entry vaporizes ~70% of them at km altitude Ablation products (vapor) condense to form “smoke” particles

Distribution of smoke in size and altitude Measurements are sparse and incomplete Current understanding based on scant observations combined with theory e.g., Hunten et al. [1980], Kalashnikiva et al. [2000]; Rapp et al. [2002] PMC volume densities are about 0.08  m 3 cm 3

Smoke Composition and Optical Properties Smoke Particle Composition: Incident meteoroids contain: carbon, sodium, sulfur, silicon, magnesium, iron… Volatile compounds are oxidized by collision with atmospheric O 2 Particle refractive indices are required to model radiative signals Refractive indices have been measured for various smoke analogues [Jager et al., 1998; Henning and Mutschke, 1997]

Smoke Signals in SOFIE Data Predictions based on CARMA smoke model [Rapp et al., 2002] SOFIE channel #2 (0.86 & 1.03  m) radiometer signals are a factor of 5 below the digitization limit dV signal increases of 15 counts at peak

Implications of MAGIC Dust Measurements Mesospheric Aerosols Genesis Interaction and Composition (MAGIC) Rocket-borne particle collector using a carbon impact grid Lab analysis reveals particle size, concentration, and composition MAGIC flight over Wallops indicates cumulative smoke concentrations of 10 6 cm -3 Cumulative over radii from nm and altitude from CARMA model (Markus Rapp) gives cumulative concentrations of 2.2  10 4 cm -3 MAGIC concentrations are 46 times greater than CARMA model

SOFIE Signals Considering MAGIC Concentrations CARMA smoke concentrations were scaled by 46 at all sizes and altitudes SOFIE channel #2 (0.86 & 1.03  m) radiometer signals are now  8 times higher than digitization limit dV signal increases from 15 to 700 counts at peak

The End backup slides follow

Smoke Layer Why are Smoke and Dust Particles Important ? -Condensation nuclei for polar mesospheric clouds (PMCs), stratospheric aerosols -Water vapor production at 70 km altitude: O + H2 reaction on smoke particles -Creation of the sodium and iron layers in the lower thermosphere -Tracers of upper atmospheric temperature and dynamics What Measurements Exist ? Primarily meteor and dust measurements, not smoke ·In situ -Space-borne impactors: number, size, origin (flight path, composition) -Atmospheric collection (aircraft, rockets): number, size, composition ·Remote -Lidar: mesospheric sodium and iron layers, meteor trails -Radar: meteors, meteor trails