Dust ablation laboratory experiments to measure the plasma...
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Dust ablation laboratory experiments to measure the plasma and light production of meteoroids in the atmosphere Z. Sternovsky, M. DeLuca, D. Janches, R. A. Marshall., T. Munsat, J.M.C. Plane, M. Horanyi IMPACT, University of Colorado, Boulder, CO 80303 Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 Physics Department, University of Colorado, Boulder, CO 80304 Aerospace Engineering Sciences, University of Colorado, Boulder, CO 80309 Space Weather Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA. School of Chemistry, University of Leeds, Leeds, UK.
Transcript of Dust ablation laboratory experiments to measure the plasma...
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:[email protected]
