A significant depletion of ionospheric plasma was produced by a chemical release experiment in the F-layer ionosphere over Hawaii. The results of measurements of the hole produced in the ionospheric plasma are reported. (GHT

Pongratz, M.B.

Smith, G.M.

Sutherland, C.D.

Zinn, J.

Pongratz, M. B.

Smith, G. M.

Sutherland, C. D.

UNT Digital Library

IJILA-UR-77-2743TWO F-REGION IONOSPHERICDEPLETIONEXPERIMENTSTITLE: }AGOPEDO- ~AUTHOR(S):SUBMITTEDMorris B(ernard) Pongratz, Gordon M(eade) Smith,C(lair) Dexter Sutherland, John ZinnTO: Naval Research LaboratoryBy ncceptassce of this article for publication, thepublisher recognizes the Oovemment’s (license) rightsinanycopyright andthetivernment anditsauthorir.asfrepresentatives have unrestricted right to reproduce inwhole or in part said article under any copyrightsecswedby the publisher.The Los Alamoe ‘Scientific Laboratoryrequests that thepublisher identify this article ●swork performed underthe auspicee of the USERDA.Ieamos~iermtificlaboratoryoftho Unboidty ofcaliforniaLOS ALAMOS, NEW MEXIC087646An Affirmative Action/Equal Opportunity EmployorMaflcfllhh r+on w ~~d u in wcount of work$W~$d h the Unhcd states Gmemmt. Ndther theUmud Slit:8 nor the Unmd .%tatcs Dtparw=en! ofFAWSY, nw my of their empfoyw, nor my Ordwhcant maws, tutamusctc.m, or tlwr cmployew, rrnkciany winmy, exprw m implkd, w WKMS any I@Ikbtlxy or mpotiIMy for the accutwy, cm+eltmaf.x wlufnegi of any in f.arnutpan, apparatus, pmdw MPIO.W8 dbdoitd, or repmienu that iu u would notmfrbw wivatefy owd ndtu.UNITEDbI’ATESENERGYRESEARCH ANDDEVELA)PMENT ADMINISTRATIONCCNTRACTW.74M.EN(3. a6/bLAGOPEDO - TWO F-REGION IONOSPHERIC DEPLETION EXPERIMENTSMorris B. Pongratz,GordonM. Smith,C. Dexter Sutherland and John ZinnUniversity of California, Los Alamos Scientific LaboratoryLos Alamos, New MexicoI. IntroductionAt this Symposium on the effects of theionospherewe would like tfireport on a veryrecent experiment wherein we turned the ta~lesand produced an effect upon the ionosphere.The effect pr~duced was a significant depletionof ionospheric plasma within a roughly spheri-cal volume of approximately 100 km diameter.In cooperationwith Sandia Laboratories,Albuquerque, Group J-10 of the Los AlamosScientific Laboratory conducted two chemicalrelease experiments Into the F-1ayer ionosphereover the Hawaiian Islands in early September1977. These experiments, codenamed Lagopedo(Spanish for ptarmigan), were directed to aninvestigationof the chemical kinetics whichfollow an injection of certain molecularspecies (H20, C02) into the F-layer. Previouswork by Mendillo et al (1975) and Bernhardt(1976) had suggested that such an injectionwould great:‘ enhance the 0+ loss ratebecause molecular charge exchange with theseartificial species proceeds at rates severalorders of magnitude larger than the ambient,natural loss rates. Enhanced electrondepletion would follow via the rapid dis-sociative recombination of electrons andmolecular ions. Because the loss rates aremuch larger than production rates the neteffect would be plasma depletion and a holein the ionospheric plasma.The questions about the hole we sought toanswer were:1. Would a plasma depletion hole form?2. What are the spatial characteristicsof the hole?3. How long does it take to make thehole and how long does it persist?4. What airglow emissions result fromthe hole formation?5. Are the sides of the hole smooth o?irregular?6. What are the effects of a hole in theionosphere?The answers to these questions wbre func-tions of the characteristics of the expansionof the molecular vapors nd the chemistry.To model the chemistry we needed to know thevelocity and spatial distribution of thevapors as a function of time. He also neededto know whether or not the releas~.dgasesclustered and froze, and if they did, whatwas the characteristic time for sublimationhack to the vapor state?The experiment was an excellent test ofthe techniques used in computer programs tomodel the chemical kinetics of the atmosphere,both during the natural, near equilibrium,variations and after perturbations of varyinqmagnitudes. Before the experiment theemphasis in the chemical modeling was uponfeatures which lent themselves to experimentalobservation such as airglow emission. Modelpredictions were also used as input foroperational decisions such as release heightand necessary ionospheric conditions for launch.II. Theory of Plasma De@etions—. —We used the diffu:ive model of Bernhardtto characterize the expansion of the molecularvapors-H20 and C02 In our theoreticalcalculations we ass:lmedthat none of thevapurs clustered and froze.In the F-region th[ dominant chemicalreactions should be 0+ charge exchange -0+ + H20 !’ H20+ + (1 (1)kl % 2.3 x 10-g cm-3s-lk2a+ + C02 + 02+ +Co (2)k2 w 1.1 x 10-9 CM-35-1followed rapidiy by dissociative recombination.‘3 OH + HH20+ + e .+ (3)k3 % 1.7 x 10-7 cm-3s-102+ + e !$4O + 0(1D) (4)k4 % 1.89 x 10-7 cm-3s-l.1,,, ,nThese reactions and species, as well asmany others, were included in our 78-species,1484-reaction chemistry code (Sutherland andZinn, 1975). Our theoretical effort has notyet included cha~”gedparticle transport alongmagnetic field lines. .The model calculations begin by selectingan altitude and starting the code off withCIRA1965 values for the concentrations of thedominant neutral species for that altitude.inftfally the ion and electron concentrationsare zero. The model does include the effectsof solar photons. Consequently as the modelproceeds forward in time and the sun risesand sets an ionosphere forms self-consistentwith the solar input and the 7$species and1484-reactions. After several model days ofself-consistentlycalculating an ionosphere weIntroduce the artificial LaqopeQrelease ~vapors. The model the%-calculates thetemporal variations of the neutral, “onic andelectron concentrations at various distancesfrom the release point.The calculations indicate a rapiddepletion of O+ and electrons. The concen-trations of t120+,H30+ and 02+ rise followingthe release. By integrating along a columnin space we were able to determine O (lD) andO (1$) column densities, and the 630,0 nmand 557.7 nm photon emission rates from these01 metastable states. We did not calculateexpected levels of other airglow features suchas OH band emissions which might result fromreaction (3). We suspect that the excessenergy resulting from reaction (3) couldappear as hydrogen atoms with kinetic energyin excess of 5eV.liehave also compared the prt?dictionsofthe many species, many reactions model withthe predictions of a model with very simplechemistry. In the complex chemistry modelreactions (1) and (3) are the dominant reac-tions, and because of the rapid rate constantfor dissociative recombination in our simplemodel we assume that electrons are removed ata rate given by.--wde . -kl [e][HN]where [e] is the electron concentration and[H20] is the water vapor concentration.Uith this one equation chemistry audEernhardt’s solutfon to the diffusionequation we can rapidly calculate the temporaland spatial effects of the release. Compar-ison of the results of the simple model showsthat, although at ear?y times the simple modelpredicts more electron removal, after about100 s the two models agree in their electronconcentration predictions. The simple modelis useful for generating two dimensionalpictures of the electron hole at many dfffer-ent times, but the complex model earlbe usedto check theory with experiment on detailssuch as airglow intensity or H30+ concentration.We are quite impressed by tne fact thatthe calculated temporal and spatial concentra-tion profiles are very sensitive to the charac-teristics of the expansion cf the molecularvapors. Consequently significant improvementin the theory will come from better definitionof the expansion characteristics.III. Experiment DescriptionThe two Lagop~o experiment payloads were ~lofted to allitude stove the Kauai Test Facil-ity, Hawaii, by Terrier-Sandhawk rocket systems.The total scientific payload mass was 200 kg,of which 88 kg was a mixture of the highexplosives Iiitromethaneand ammonium nitratewhi:k yield only H20, C02 and N2 in an idealdetonation. About 2500 moles of H20 and 500moles of C02 were produced and dispersed by thehigh explosive detonation.On board the Sandhawk second stage (butspring separated from the high explosivepackage after motor burnout and prior todetonation) were four experiments designed toquantitatively measure the effects of therelease. These instruments passed through thev~’lumesurrounding the detonation secondsafter the event.A thermal ion detector (TID~, similar tothat which detected ion dropout on the Buaroshaped charge barium injection experiment,was provided by Brian Whalen of the CanadianNational Research Council at Ottawa. The TIDmeasured ion flux with good directional butmodest (1 in 16) mass resolution, To comple-ment the TID measurements, Charlie Johnsonand Gary Sjolander from Ed Szuszczewicz’sgroup at NRL provided Bennett-type ion massspectrometers with sensitivity in the 9-40AMU range.The two additional experiments containedin the Sandhawk section were designed tomeasure electron properties, Langmuir probeswere flown by Dave Winningham of the Univer-sity of Texas, Dallas, and measured electronconcentration and temperature iv situ. A. V.da Rosa and Paul Bernhardt of StanfordUniversity flew dual Frequencv (137,35 and412,05 MHZ), phase coherent beacon transmitters.Using ground based receivers and differentialDoppler techniques, electron column densitieswere measured,Because of the dynamic nature of theF-layer ionosphere, it was necessary tomonitor electron concentration as a functionof altitude in real time, Bill ‘ qht of NOAABoulder installed a Dynasonde on islandof Kauai. The Dynasonde is a st. of-the-artionospheric sounder with computer control anddata processing. During the countdown theK)ynasondeprovfded minute by minute values ofthree parameters ([e] ax, h,ax and thickness)ustJ to describe the !’onosp\ere. A necess(~rycondition for lallnchwas that calculations2 ,,,,.\. M. B. b’Qfl~t%LZ, b. m. mlm, b. v. 2ULIWI ICIIIU, U. LIIIII.indicate that a threshold number”tiielectronswould be removed by the release effects. Thisnumber required that hmax not be far beyondrocket apogee, that the thickness parameter,or scale height, be greater than about 25 km,and that [e]max not be too low. The Dynasondewas also used to detect the hole created by therdleases. It was able to monitor the late timeexistence and motion of the hole.Jim Clynch of the University of Texas atAustin andAFGL personnel monitored totalelectron content between French Frigate Shoals,small islands northwest of Kauai, and the syn-chronous satellites ATS-3 and SMS-1 byobserving the Faraday rotation of the VHFtransmitter signals from these satellites. Byfortunate coincidence the island ground stat-ion, the two ionospheric holes and thesatellites were colinear. The effects of thedepletions were variations of the amplitude andphase of the electromagnetic waves transmittedfrom satellites.Walt Chesnut of SRI International operateda HF-radar on the island of Hawaii. The radarprobed the release region in a geometry suchthat the rqdar line of sight was perpendicularto the geomagnetic field lines through thehole. With this geometry the radar couldobserve scattering from field aligned irreg-ularities that were predicted by theorieswhich treated the hole as a “negative bariumcloud” which would be subject to the gradientdrift instability because of the motion ofneutrals across the electron density gradient.Optical ground stations instrumented toobserve the airglow resulting from the chem-i;try, and the expansion of the sunlit icecloud were on the islands of Kauai and Maui,These ground stations were operated by LASLand EG&G personnel. The details of theinstrumentationand results of the experimentswill be discussed in the next section.IV. Lagopedo Results———Necessary conditions regarding clear weather,the parameters of t~e ionosphere, functioninginstrumentationand communications complicatedthe operational decisions. In satisfying theminimum requirements of all participatingexperimenterswe had to Illakecompromises withthe ideal conditions for some experimenters.Neverthelesswe were able to complete two(of two) quite succesful launches and releases.The release and ionospheric parameters of theLagopedo Uno and DOS experiments are given intable 1.Although investigators from otherinstitutionscooperated in providing a widi”variety of diagnostics for Ldgopedoexperiments, in this report we shall limitthe presentation of results to our ownoptical observations. However, we think it isappropriate to note that the observations ourcolleagues have reported to us are consistentIIwith the theory of hole formation via thecharge exchange-dissociative recombinationmechanism proposed “byBernhardt.Table IusReleaseParameterstvent he (UT) 0S54:00 9J2171tvent Altitude 261.22 kmEvent LJtltude(geodetic) 22.279° NEvent Longitude 159.9620NReleasedin 5unlight YesIonosphericParametersPtak ElectronOensity l.O x 106 ●/cm3Heightof Ptak 275 kmF2 L4yer ScaleHeight 42 kmStability StAble13604:IU91i2171222.86km22.262°N160.3510uNo3.4 x 106 elcm3323 km65 kmUeak SpreadFiceOn Lagopedo Uno the expanding cloud ofcrystals was observed with instrumentationatop Mt. Haleakala on Maui. For Lagopedo Doswhich was not release? in sun ight no icecloud was observed. The early time(t < E + 30s) spectrograph data is dominatedby the solar continuum spectrum reflected bythe cloud. Intensified imaging cameras wereequipped with 455.4 nm interference filtersto measure the scattered sunlight. No naturalairglow emission lines are in this region ofthe spectrum. The ice cloud was observedabove background for about 100 s. The shapewas generally spherical. The apparent(optical) diameterof the ice cloud as afunction of time hds been fit b:forrnuladiameter = (37 km) t0”42The ice cloud diameter was overthan 30 s!a power ?awt.< 305) .100 km in lessAssuming that the ice cloud expandsdiffusively in a CIRA 1965 neutral atmospherewe ffnd that the diffusion constant needed toexplain the observations is0=7.7 x101acm2/s .This value of O is five times larger than thediffusion coefficient for }~atervamr-calculated using Bernhardt’s formula and a1965 CIRA atmosphere,Because fce cloud brightness decreasedIn time faster than the l/t decrease incolumn density giver by diffusion we ~ssumethat the fce clusters sublimated, and themolecules returned to the vapor state. Welet the number of molecules per cluster, g,vary asg . go e-ti~where go is the number in a cluster of initialradius, r.. As the molecules sublimate the.>-% ... M. B. Pongratz, G. M. Smith, C. D. Sutherland, J. Zinncluster radius gets smaller and the cross-sectlon for scattering sunlight, a : anr2,decreases, and the ice cloud brightnessdecreases faster than the column density n.The value of? necessary to fit the data is-T= 16.5s. The absolute value of the bright-ness requires the relationshipcaXOk= O.I/micronrwhere x. is the fraction of the H20 moleculeswhich form clusters and freeze.Me in,ferthat r. < .3 microns because thespectral measurements indicate increasingspectral radiance with decreasing wavelength.Because ml we conclude that less than 3% ofthe vapor clustered and froze.The airglow measurements are also con-sistent with a large hole diameter. Thespectrographicmeasurements indicate enharve-ment of the 01 emission lines at 557.7 nm and630.0 nm. OH band emissions were not observedby either of two spectrographs or twointensified imaging cameras equipped withOH near IR-interference filters.The 9(1D) emission to the ground stateof 01 provided oramatic confirmation of theprediction? of>he complex chemistry code.Because 0( D) 1s a metastable state itsradiative lifetime is longer than 100 s.This, coupled with the fact that not all theO(lD) states are produced promptl,yat event,gives a theoretical temporal profile for630.Onm emi,sion with a slow rise to amaximum level some 90 s after the release andthen a similar decay back to pre-releaseReferencesM. Mendillo, G. S. Hawkins, and J. A.Klobuchar, “A Large-Scale Hole in theIonosphere Caused by the Launch of Skylab,”Science~, 343 (1975).P. A. Bernhardt, “The Response of the Iono-sphere to the injection of ChemicallyReactive Vapors,” Stanford Electronicradiav The actual measured 630.0 nmradiance from both-stations for both experi-ments does reach a maximum value some 90-120 safter the release. Naturally the signal tonoise and the confidence level is quite highwhen one detonates the explosive and thenobserves peak signal some 90-120 s later!The spatial profile and peak radiance ofthe airglow emission at 630.0 nm also supportthe temporal profile evidence that anionospheric hole was formed by chemical effects.The emitting region expanded to overfill thefields-of-view of all the imaging instruments.This region was at least 125 km in diameter.The shape was generally spherical. TheLagopedo Uno peak radiance was about akilorayleigh above background. The Lagopedo00s peak radiance was about 300 Rayleighsabove background.v. ConclusionsEven though the experiments were perform~only ‘!astSeptember we are able to giveprelir,linaryanswers to our questions. Aplasma depletior~hole in the ionospherewas formed via the predicted chemicalprocesses. The hole is nearly isotropic andGaussian in profile with a thickness at halfdepletion of 60 km. The hole is formed inless than 5 minutes and persists for nearly ahalf hour. Only atomic oxygen airglow wasobserved. No irregularities were observedalong the sides of the hole. In the nearfuture we anticipate publishing more completeand more detailed results of this first SU(cessful experiment directed towards produca hole in the ionosphere.Laboratories Technical Report No. 17, Mayng975.C. Dexter Sutherland and John Zinn, “Chan+stryComputations for Irradiated Hot Air,” LosAlamos Scientific Laboratory reportLA-6055-MS, September 1975.

Lagopedo: two F-region ionospheric depletion experiments

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