detection of charged aerosol particles in the …...detection of charged aerosol particles in the...

Detection of Charged Aerosol

Particles in the Mesosphere by

Rocket-borne Probes

Scott Robertson & Scott Knappmiller University of Colorado, Boulder

ARR, October 2011

2

Collaborators

• University of Colorado – Zoltan Sternovsky

– Mihaly Horanyi

• University of Washington – Robert Holzworth

– Michael Shimogawa

• Tech. Univ. Graz-Austria – Martin Friedrich

• ARR/ALOMAR-Norway – Michael Gausa

• Stockholm Univ. – Jörg Gumbel

– Misha Khaplanov

– Linda Megner

• FFI/UiOslo – Ulf-Peter Hoppe

• IAP-Germany – Gerd Baumgarten

– Ralph Latteck

– Markus Rapp

3

Outline

1. Noctilucent Clouds

2. Instruments

3. MASS data, 2007

4. CHAMPS payload 2011

5. Summary

1. NOCTILUCENT CLOUDS

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5

Noctilucent Clouds (NLC) “Night Shining

Clouds”

NLC seen from

Space are called

“Polar

Mesospheric

Clouds (PMC).”

6

NLC Environment/Background

D

NLC (140 K)

• NLC are composed of ice

particles.

• Water vapor condenses due to

temperature minimum

(mesopause).

• NLC particles charge in the D-

region of the ionosphere.

• Charging of NLC particles

related to anomalous radar

echoes (Polar Mesospheric

Summer Echoes, PMSE).

7

NLC Science Question:

Meteoric smoke particle

formation

Homogeneous nucleation requires lower temperature

Condensation nuclei are required

What are the nuclei?

Meteoric smoke particles

Sulfate particles

Soot particles

Molecular ions

Water cluster ions

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• NLC particles grow to 50 nm in radius, large enough to scatter sufficient light to be visible.

• Mie scattering scales with r6.

NLC detection (1)

ALOMAR lidar Rocket-borne photometer

Stockholm University

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AIM satellite was dedicated to NLC with many instruments

NLC detection (2)

Cloud Imaging Particle

Size Experiment (CIPS)

Solar

Occultation

For Ice

Experiment

(SOFIE)

10

NLC detection (3) In-Situ Particle Detectors

• Blunt cup probe [Havnes et al., 1996]

• Faraday cup [Blix et al., 1990]

• Quadrupole Mass Spectrometer [Viggiano and Hunton, 1999]

• Magnetically Shielded Detectors (Colorado Dust Detectors) [Smiley et al., 2002]

• Gerdien Condenser [Croskey et al., 2001]

• Mesospheric Aerosol Mass Spectrometer (MASS) S. Knappmiller, S. Robertson, Z. Sternovsky, and M. Friedrich: A rocket-borne mass analyzer for charged aerosol particles inthe mesosphere, Rev. Sci. Instrum., 79, 104502-1, 2008.

1. Rocket aerodynamics limit collection of smallest particles

2. Only detect one polarity of charge

3. Limited mass resolution

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Science Questions for MASS

rocket campaign - 2007

Idea: fly a mass spectrometer for heavy particles

• How numerous are the particles?

• How does the number density vary with altitude?

• Do positive and negative particles coexist?

2. MASS INSTRUMENT

MESOSPHERIC AEROSOL SAMPLING SPECTROMETER

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• Have separate detectors for different sizes of particles – (a low-resolution mass spectrometer)

• Have separate detectors for positive and negatively charged particles.

• Avoid aerodynamic drag effects that select particles (air flows through).

Instrument Objectives

The MASS instrument Mesospheric Aerosol Sampling Spectrometer

4 pairs

voltage-

biased

collectors

Air exit

windows

Air sampling

slit ~ 25 cm2

•1ST plate <0.5nm

•2nd plate 0.5-1nm

•3rd plate 1-2nm

•4th plate >3nm

Assuming Ice density

r = 930 kg/m3

Measures each

polarity of charge on

separate collection

plates

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Currents to electrodes are converted to number density:

I = n Zq v A

n = number density Zq = charge on particle

v = rocket velocity, 1050 m/s A = inlet area, 25 cm2

Z = 1 assumed q = electron charge

n = I / (Zq v A)

Resolution: 1 pA = 2.5 cm-3

electrical noise 8pA n = 20 cm-3

Vertical Resolution: 1 meter

MASS data Conversion

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MASS Aerodynamic Design

• Aerodynamic inlet minimizes shock wave above MASS instrument.

• Exit windows mitigates static build-up of pressure within the instrument.

• Verified by DSMC aerodynamic simulations and particle trajectory program.

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Particle Trajectory Simulation

• Input static electric field

• Input number density, temperature, and velocity distribution from DSMC.

• Specify test particle’s initial position, velocity, and mass.

• Calculate a collision frequency.

• Determine if collision has occurred using differential time step.

• Compute collision with air molecule using momentum conservation.

• Calculate collection efficiency for each collection plate.

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101

102

103

104

105

106

0

20

40

60

80

10087.5 km, Pos. Particles, -1 V

Radius [nm]

C

olle

ctio

n E

ffic

iency

[%

]

MASS [amu]

1

2

3

4

NO+

Ions

1 10

B

Calibration Results

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Payload

Forward nosecone is spring-deployed

Aft rocket skin falls away with rocket motor

Two rocket motors: Terrier Mk12 – Improved Orion

Apogee: 133 km

Attitude Control

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Forward Payload Section

MASS Instrument

Faraday Rotation

Antennas

Electric Field Booms

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Aft Payload Section

Electric Field Booms

Photometer

3. MASS DATA

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Conditions at 1st launch

Date of launch: 3 August 2007

Time of launch: 22:51 UTC

Time of AIM overpass: 22:25 UTC

Solar zenith angle: 93.2 degrees

Location: Andøya Rocket Range

ALWIN radar: PMSE observed

ALOMAR lidar: NLC observed earlier

Trondheim webcam: NLC observed

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ALWIN Radar

• Broad PMSE from 81-89 km.

• Two PMSE maxima, 83 km & 88 km.

ALOMAR RMR Lidar

• Cloud peaks at 83 km.

• Resolution 50 m.

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MASS Data Launch I Upleg

Graph A:

Positive

and

Negative

Ions

Graph C:

1-2 nm

Particles

+ & -

Coexist.

Graph B:

0.5-1 nm

Particles,

No

negative

Graph D:

>3 nm

All

negative

particles.

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MASS Data Results

• First time simultaneous measurements of both

positive and negative charge densities

• First mass distribution of NLC particles

– 0.5 - 1nm particles are positive.

– 1 - 2nm equal parts of negative and positive.

– > 3nm all particles are negative.

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Charge Model

• Include photodetachment and photoionization

rates, needed to explain positive particles.

• Model multiple materials:

– Pure NLC ice particles

– Fe2O3 (Hematite) as possible condensation nuclei.

– Spherical Hematite cores coated with monolayers of

ice as large NLC particles.

• High aerosol density case vs. low aerosol

density case relative to electron and ion density

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Kinetic Charge Model

r

en

Z

ZrN ,

Z Charge number

Radius

Number density

Electron density

Ion density

Rate particle charges negatively

Rate particle charges positively

Z

Charge Model used

many times before:

Jensen and Thomas

(1991), Rapp and

Lübken (1999), Rapp,

(2000), Rapp and

Lübken (2001), Draine

and Sutin (1987),

Weingartner and Draine

(2001), and Draine and

Sutin (1987).

1,1,,,,1,1,

,

ZrZrZr

e

ZreZrZr

e

Zre

ZrNNnNn

dt

dN

in

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Charge Model

-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 60.0

0.2

0.4

0.6

0.8

1.0

BPure Ice

Photodetachment

SZA = 93

ne = n

i = 3162 cm

-3

Charg

e P

robability D

istr

ibution P

r,Z

Charge Number Z

Radius

10 nm

20 nm

60 nm

100 nm

4. CHAMPS PAYLOAD

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What are the

NLC condensation nuclei? Meteoric smoke particle

formation

Homogeneous nucleation requires lower temperature than is observed, hence condensation nuclei for heterogeneous nucleation are required.

What are the nuclei?

Meteoric smoke particles

Water cluster ions

Molecular ions

Sulfate particles

Soot particles

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NLC condenstion nuclei

Science Questions:

What can MASS instrument say about condensation nuclei:

1. Meteoric smoke particles are heavier than ions, they will

show up on 0.5 – 1 nm mass channels

2. MASS will find if the charge is positive or negative, or both

3. MASS will find altitude range of detectable particles

4. Day and night launches will reveal whether or not sunlight

changes the charge (photoelectric charging).

But, uncharged particles are not seen.

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Meteoric smoke particle detection

Active photoionization + Faraday cup

ECOMA instrument

[Rapp et al., 2009]

Forward Experimental Section

MASS

Instrumen

t

Pair of

Langmuir

Probes

Pair of

Positive Ion

Probes

Colorado

Dust

Detectors (4)

E-boxes for

MASS and the

Colorado

Dust

Detectors

E-boxes for

Positive Ion Probe

and Langmuir

Probe

Aft Experimental Section

Pirani

Pressure

Gauge

Faraday

Rotation

Antennas E-box for

Faraday

Photo Detectors

(4)

Photo Detectors

E-box

Channeltron

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Thank you!

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NLC Papers • M. Rapp, I. Strelnikova, B. Strelnikova, P. Hoffman, M. Friedrich, J.

Gumbel, L. Megner, U.-P. Hoppe, S. Robertson, S. Knappmiller, M. Wolff, and D. Marsh: Rocket-borne in-situ measurements of meteor smoke: charging properties and implications for seasonal variation, J. Geophys. Res., 115, D00I16, doi:10.1029/2009 JD012725, 2010.

• S. Robertson, M. Horanyi, S. Knappmiller, Z. Sternovsky, R. Holzworth, M. Shimogawa, M. Friedrich, K. Torkar, J. Gumbel, L. Megner, G. Baumgarten, R. Latteck, M. Rapp, U.-P. Hoppe, and M.E. Hervig: Mass analysis of charged aerosol particles in NLC and PMSE during the ECOMA/MASS campaign, Ann. Geophys., 27, 1213-1232, 2009.

• S. Knappmiller, S. Robertson, Z. Sternovsky, and M. Friedrich: A rocket-borne mass analyzer for charged aerosol particles in the mesosphere, Rev. of Sci. Inst., 79, 104502, 2008.

• K. Amyx, Z. Sternovsky, S. Knappmiller, S. Robertson, M. Horanyi, and J. Gumbel: In-situ measurement ofsmoke particles in the wintertime polar mesosphere between 80 and 85 km altitude, J.Atmos. and Solar Terr. Phys., 70, 61-70, 2008.