Dustablationlaboratoryexperimentstomeasuretheplasmaandlightproduction

ofmeteoroidsintheatmosphereZ.Sternovsky,M.DeLuca,D.Janches,

R.A.Marshall.,T.Munsat,J.M.C.Plane,M.HoranyiIMPACT,UniversityofColorado,Boulder,CO80303LaboratoryforAtmosphericandSpacePhysics,UniversityofColorado,Boulder,CO80303PhysicsDepartment,UniversityofColorado,Boulder,CO80304AerospaceEngineeringSciences,UniversityofColorado,Boulder,CO80309SpaceWeatherLaboratory,NASAGoddardSpaceFlightCenter,Greenbelt,Maryland,USA.SchoolofChemistry,UniversityofLeeds,Leeds,UK.

Outline

• Theunderstandingofmicrophysicalprocessesinmeteoricablationisneededfor:– Interpretingmeteorradarmeasurements– Confiningthetotalmassinputofcosmicmaterialintothe

atmosphere– Understandingtheoriginanddistributionofinterplanetarydust

• Theablationprocessisstudiedexperimentallyatauniquedustacceleratorfacility (Univ.ofColorado)

• Mainresultsfromrecentmeasurementcampaigns:– TheionizationefficienciesofFeandAlmeasuredovertheawide

rangeofvelocities,andtheyarenotsmall.– Firstmeasurementsofparticledecelerationandcalculatingthe

moleculardragcoefficient

Aremeteorradardatainterpretedcorrectly?

ZodiacalDustCloudmodel

Radarmeasurement

Nesvorny elal.2010,Janchesetal.,2014 • DisagreementbetweenmodeledandmeasuredIDPvelocitydistribution

• Dailycosmicmassinflux3-300t/d(Plane,2012)• Radars:~5t/d(Mathewsetal.2001)

Ablation/ionizationmodelsneedexperimentalverification

FeinputratesintotheatmosphereModeledandmeasuredvelocitydistributions

Stateoftheartablationmodel(afterVondrak etal.,2008)

Momentumequation,Γ =moleculardragcoefficient

Masslossrate,γ =uptakecoefficient

Energyconservation(heating)equationΛ – heattransfercoefficient

Ionizationrate:(dm/dt)× β(v)

β(v)=Ionizationefficiency,functionofvelocity

ThedustacceleratorfacilityoperatedattheUniv.ofColorado

FundedbyNASA,SolarSystemExplorationResearchVirtualInstitute(SSERVI)program

3MVPelletronAccelerateddust:• 0.1-2micron• 1-100km/s• Fe,Al,C,minerals….

Particlemassvs.velocitydistribution

Velocityrangeofinterest

~1micronsize

Theablationfacility

DustDifferentialpumpingAblationchamber(~40cm)

15– 200mTorr

Measuringtherateofchargegeneration

E

Segmentedandelectricallybiasedchargecollectors

𝛽 = TotalcollectedchargeDustmass(#atoms)

Forcompleteablation:

Improvingthefacilitywithvelocitymeasurementcapability

Highvelocitydust:FourPMTdetectorsmonitorthevelocityoftheablatingparticleLowvelocitydust:Pickuptubeandimpactdetectorsprovidevelocityandslowdown

Thomasetal.,RevSci Instrum 88,034501(2017)DeLucaetal.,inpreparation(2018)

Pickup-tubedetectors

PMT

Impactdetector

Initialresultsof𝛽measurements

E.Thomasetal.,GRL(2016)&RSI(2017)

• Fedustparticles• Differenttargetgases• Limitedto≥20km/s

• Previousmeasurements(Friichtenicht etal.,1967)

• FittingdatawiththeJonesmodel(1997)

β- stateoftheart(Vondrak etal.,2008)FromVondrak etal.,2008,forionizationinN2

SlatteryandFriichtenicht (1967)data

€

β0 =c(v − v0 )

2v0.8

1 + c(v − v0 )2v0.8

€

v02 =

2(m + M )mM

ϕIE

TheJonesmodel(1997)

PMTmeasurementsconfirmlimitedslowdownPM

Tchanne

lsinse

quen

ce

Measurementconfirmthattheparticleslowdownissmall(<1-2km/s)

𝛽measurementsextendedtolowervelocities(inair)

Aluminum Iron

• n =1.6isgoodfitforAl&Fe• v0 =9.1km/s(Al)• v0 =8.95ks (Fe)• c– fittingparameter

DeLucaetal.,PSS(2017)

Slowdownexperiments– measuringthedragcoefficient

Measureddata

Air:𝚪 = 𝟏. 𝟑𝟐 ± 𝟎. 𝟏𝟐

N2:𝚪 = 𝟏. 𝟑𝟒 ± 𝟎. 𝟎𝟖

Ar:𝚪 = 𝟏. 𝟐𝟗 ± 𝟎. 𝟏𝟎

CO2:𝚪 = 𝟏. 𝟐𝟖 ± 𝟎. 𝟏𝟑

𝑑𝑣𝑑𝑡 = −

3𝚪𝑣2𝜌4564𝑅𝜌9:;:<6

• 𝚪 =0.5– 1assumed• Aluminumparticles• 1– 10km/s

Timingoftheeventsw/wogasfillingyields𝚪

DeLucaetal.,inprep.(2017)

Nextchallenge:matchingthemeasuredablationprofileswithmodels

• Velocity: 25.1km/s• Radius: 58nm• Material: Fe• Gas: N2• Pressure: 49mTorr

Measureddata

Modelcalculations

Summary/Conclusions

• Dustacceleratorfacility- enabledtheexperimentalinvestigationoftheablationprocess

• Ionizationefficiencycanbedirectlymeasured• Lowionizationefficiencyisnotthereasonforradarinsensitivity

• Dragcoefficientmeasurementsinprogress• Contact:Zoltan.Sternovsky@colorado.edu