A Miniature Sensor for Electric Field Measurements in...

A Miniature Sensor for ElectricField Measurements in Dusty

Atmospheres

N. Renno, J. Kok, S. RogackiUniversity of Michigan

Ann Arbor, MI, USAand

H. KirkhamJet Propulsion Laboratory

Pasadena, CA, USA

March 28, 2007 Electrostatics 2007, Oxford, UK

OutlineOutline• Motivation

– Dusty plumes and vortices• Role on the global aerosol budget & climate

– Electrostatic Dust Lifting• In laboratory experiments• On dust devils• On the Moon and asteroids

– Effects of Dust Electrification• On saltation• On atmospheric chemistry

• The UM/JPL Electric Field Sensor• Conclusions


• Motivation– Dusty plumes and vortices

• Role on the global aerosol budget & climate– Electrostatic Dust Lifting

• In laboratory experiments• On dust devils• On the Moon and asteroids




Terrestrial Dust DevilsTerrestrial Dust DevilsUbiquitous in arid regionsUbiquitous in arid regionsfrom spring to fallfrom spring to fall


Dusty Convective PlumesDusty Convective PlumesUbiquitous in arid regionsUbiquitous in arid regionsfrom spring to fallfrom spring to fall


Large Terrestrial Dust StormsLarge Terrestrial Dust Storms

RelativelyRelativelyrare eventsrare events


Global Mineral Dust BudgetGlobal Mineral Dust Budget

13 ± 734 ± 19808TOTAL

*Based on an average global dust source area of 2.14 x 107 km2

3 ± 28 ± 6247Dusty Plumes

10 ± 626 ± 18561Dust Devils

Contribution of Dust Plumes and Vortices to Global Mineral Dust Budget*

Contribution toGlobal Mineral Dust

(%)Dust Flux

( 109 kg/year)

Contribution toGlobal Particle

Emission(%)

(Koch and Renno 2005)


Martian Dust Devils &Martian Dust Devils &StormsStorms

UbiquitousUbiquitous Relatively rareRelatively rare

Credit: NASA/JPL/MSS (Both Images)






• The UM/JPL Electric Field Sensor

• Conclusions


Dust Lifting by E-FieldsDust Lifting by E-Fields

(Kok and Renno 2006)


Threshold E-Field for DustThreshold E-Field for DustLiftingLifting

Ethr d( ) = 0.69!

1.37"#0d+$partdg

8.22#0


(Shao and Lu 2000)







• Conclusions


Electric Fields in Terrestrial DustElectric Fields in Terrestrial DustDevils (~ 1 m above ground)Devils (~ 1 m above ground)

(Farrell et al. 2004, Renno et al. 2004)


WhatWhat is the Chargeis the Charge DistributionDistributionin Dust Devils?in Dust Devils?

- -- --- -

- - -- - -- - - -- - --- - -+ + + +


Electrostatic CleaningElectrostatic Cleaning on on MER?MER?

Images taken on Sol 416 (March 5) and Sol 426 (March 15) respectively.Credit: NASA/JPL/Cornell







• Conclusions


The Surveyor (S-1 to S-7)The Surveyor (S-1 to S-7)MissionsMissions

Right: Surveyor 3 & Apollo 12


Lunar Horizon Glow (HG) wasLunar Horizon Glow (HG) wasObserved by S-1, S-5, S-6, S-7Observed by S-1, S-5, S-6, S-7

(Criswell 1973)


Composite ofComposite of Five SurveyorFive Surveyor 77ImagesImages

(Rennilson and Criswell 1974)

• The HG can explained by forward scattering from~ 50 particles/cm2 of d ~ 10 µm

• This is 107 more particles than ejected by micrometeorites


Crepuscular Rays onCrepuscular Rays on thetheMoon?Moon?

(McCoy 1973)The Lunohod-2 astrophotometer showed that the “twilight” lunar sky is 20 times brighter at visiblewavelengths than expected from star light (Severny 1975)

Terrestrial crepuscular rays


Lunar Eject And MeteoriteLunar Eject And Meteorite(LEAM) Experiment(LEAM) Experiment

• Most detection were near the terminator– Caused by impacts of charged dust particles

with velocities up to 1 km/s– Hypervelocity impacts from micrometeorites

were rare(Berg 1976)


Our Predictions for the MoonOur Predictions for the Moon• This suggeststhat cohesion is3 ordersof magnitudeweaker on thelunar regoliththan onterrestrial soils



Our Predictions for the MoonOur Predictions for the Moon• Electric fields of about 25 kV/m are

necessary to levitate lunar dust particles withdiameters d ~ 10 µm

• The smaller dust particles “observed by Apollo”astronauts at 1-100 km above the lunar surface:– Accelerate upwards at ~160 m/s2 (0.1 µm particles)– Could reach high altitudes, depending on the

structure of the electric field above the lunar surface


Ponded Ponded Deposits on AsteroidDeposits on AsteroidErosEros

(Robinson et al. 2001)

NEAR-Shoemaker Mission







• Conclusions


Electric Fields Measured inElectric Fields Measured inSaltationSaltation

(Schmidt el al. 1998)


Effect ofEffect of Large E-FieldsLarge E-Fields• Electrical forces can dramatically reduce the

wind speed necessary to maintain saltation

Kok and Renno 2006


Evidence of ElectricEvidence of Electric Activity onActivity onMarsMars

• Renno et al. (2003) assume that ~ 1% of theenergy dissipated is non-thermal radiation (alower bound based on thermalized channels)

• Dust storms with active regions covering ~10%of the Martian disk produce brightnesstemperature perturbations of ~10 K


Measurements of MarsMeasurements of MarsMicrowave Disk BrightnessMicrowave Disk Brightness

(Doherty et al. 1979,Renno et al. 2003)


VLA Observations of MarsVLA Observations of Mars


Chemical Implications of the BulkChemical Implications of the BulkElectric Fields Predicted on MarsElectric Fields Predicted on Mars

• Electric fields of ~20 kV/m leads to the production ofmore than two orders of magnitude H2O2 than UVradiation

(Atreya et al. 2006; Delory et al. 2006)


Predictions of Atreya, Wong,Predictions of Atreya, Wong,Renno Renno et al.et al. (2006) (2006)







• Conclusions


E-FieldE-Field Measurements inMeasurements inDusty PhenomenaDusty Phenomena

• Commercially available instrumentswere developed to measure space-charge-free fields– Charge accumulation cause large errors on

these instruments– The effects of the impact of charged dust

particles can not be distinguished fromthat of the space field

• A new instrument is required


Top Functional Requirement (FR)Top Functional Requirement (FR)and Design Parameter (DP)and Design Parameter (DP)

• FR1: To measure the near-surfacespace electric field within clouds ofcharged dust particles

• DP1: Cylindrical Electric Field Mill


Top Level RequirementsTop Level Requirements• [FR1.1]: To distinguish the ambient space field

from the effects of charged particles colliding withthe sensor

• [DP1.1]: Vary the rotation rate duringmeasurements (Maruvada et al. 1983)

• [DP1.2]: Add sharp points to limit the sensorpotential

• [FR1.2]: To measure the electric fields close(~ 1 cm) to the surface

• [DP1.2]: Instrument diameter ~ 1 cm


Theoretical Basis for DP1.1Theoretical Basis for DP1.1

i(t) = 4r!0(E

x" sin" t + E

y" cos" t)

+

1

2kr(I

xcos" t + I

ysin" t)

Isolation between the two 1/2-cylinder electrodes


Lower Level RequirementsLower Level Requirements• E-field range: 50 to 106 V/m• E-field resolution: 10 V/m to 1 kV/m• Time response: 1 Hz• Accuracy: 10%• Operation time: 24 Hz (without data download or battery

recharge)• Configuration: Up to 4 sensors staked above each other• Ground isolation: Isolated sensors to measure the local

field at various heights• Charged dust: The sensor must be able to make

measurements with accuracy of 10% inside clouds ofcharged dust particles


Our Our ββ-prototype -prototype E-Field SensorE-Field Sensor


Block diagram of the UM/JPLBlock diagram of the UM/JPLPrototype E-Field SensorPrototype E-Field Sensor


ConclusionsConclusions• Dust Electrification

– Produces large electric fields in dusty phenomena– Plays an important role on the chemistry of Marsʼ atmosphere– Produces non-thermal electromagnetic radiation

• Electrostatics play an important role on dust liftingand transport on Earth and beyond– It is important to measure the near surface electric field in dusty

environments (dust devils, dust storms, Mars, Moon, etc)

• The UM/JPL electric field sensor can be used toshed light on dust electrification on Earth andbeyond– The sensor characterization is ongoing– We are looking for an industrial partner to commercialize it


Thanks!Jasper Jasper KokKokHarold Harold KirkhamKirkhamStephen Stephen RogackiRogackiRobb GillespieRobb GillespieNSF & NASANSF & NASA


Effect of Charged Sensor onEffect of Charged Sensor onthe E-Fieldthe E-Field

A Miniature Sensor for Electric Field Measurements in...

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