SOFIE Measurements of Cosmic Dust in the Mesosphere

1
SOFIE Measurements of Cosmic Dust in the
Mesosphere

• Mark Hervig
• GATS Inc.

2
Dust Smoke overview

• Cosmic dust particles are constantly entering the
  Earths atmosphere
• Heating during atmospheric entry vaporizes 70
  of them at 80 - 100 km altitude
• Ablation products (vapor) condense to form
  smoke particles

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
3
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 ?m3 cm3
4
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 O2

• 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

5
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
6
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 106 cm-3
• Cumulative over radii from 1 - 3 nm and altitude
  from 76.7 - 93.5
• CARMA model (Markus Rapp) gives cumulative
  concentrations of 2.2 ? 104 cm-3
• MAGIC concentrations are 46 times greater than
  CARMA model

7
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
8
The Endbackup slides follow
9
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) -Atmosphe
ric collection (aircraft, rockets) number,
size, composition Remote -Lidar mesospheric
sodium and iron layers, meteor trails -Radar
meteors, meteor trails