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DEMETER observations of manmade waves that

propagate in the ionosphere

Michel Parrot

To cite this version:

Michel Parrot.

DEMETER observations of manmade waves that propagate in the ionosphere.

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Contents lists available atScienceDirect

Comptes

Rendus

Physique

www.sciencedirect.com

Radio science for Humanity / Radiosciences au service de l’humanité

DEMETER

observations

of

manmade

waves

that

propagate

in the ionosphere

Observations

par

Demeter

d’ondes

d’origine

humaine

se

propageant

dans l’ionosphère

Michel Parrot

Universitéd’Orléans,LPC2E/CNRS,3A,avenuedelaRecherche-Scientifique,45071Orléanscedex2,France

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Articlehistory:

Availableonline6February2018

Keywords: Ionosphere Manmadewaves Propagation Mots-clés : Ionosphère

Ondesd’originehumaine Propagation

ThispaperisareviewofmanmadewavesobservedbytheionosphericsatelliteDEMETER. Itconcernswavesemittedbytheground-basedVLFandELFtransmitters,bybroadcasting stations, by the power line harmonic radiation, by industrial noise, and by active experiments. Examples are shown including, for the first time, the record of a wave comingfromanELF transmitter.Thesewaves propagateupwardsin themagnetosphere andtheycanbeobservedinthemagneticallyconjugatedregionofemission.Depending ontheirfrequencies,theyperturbtheionosphereandtheparticlesintheradiationbelts, andadditionalemissionsaretriggered.

©2018Académiedessciences.PublishedbyElsevierMassonSAS.Thisisanopenaccess articleundertheCCBY-NC-NDlicense (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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Cet article constitue une revue des ondes d’origine humaine observées par le satellite ionosphérique Demeter. Cela concerne les ondes émises par les émetteurs TBF et EBF, parlesstationsderadio,parlerayonnementdeslignesélectriquesetparlesexpériences actives.Des exemplessont présentésdont,pourla premièrefois,l’enregistrementd’une onde émise par un émetteur EBF. Ces ondes se propagent vers la magnétosphère, et ellespeuvent être observées au point conjugué magnétique de leur région d’émission. Selonleursfréquences,ellesperturbent l’ionosphèreetles particulesdans lesceintures deradiation,etdenouvellesémissionssontdéclenchées.

©2018Académiedessciences.PublishedbyElsevierMassonSAS.Thisisanopenaccess articleundertheCCBY-NC-NDlicense (http://creativecommons.org/licenses/by-nc-nd/4.0/).

E-mailaddress:mparrot@cnrs-orleans.fr. https://doi.org/10.1016/j.crhy.2018.02.001

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1. Introduction

DEMETERwas an ionosphericmicro-satellite inoperationbetweenJune 2004andDecember 2010.Its orbitwas circu-lar(660 km),polar,andnearly sun-synchronous(10.30 LTand22.30 LT). Its payloadmeasured electromagneticwavesin differentfrequency ranges fromULFto MF, andalso plasma parameters (for example theelectron andion density).The descriptionoftheexperimentscanbe foundin[1].TheVLFelectricandmagneticspectrogramswerealwaysonboard cal-culatedwithalowtime (2s)andfrequency(19Hz) resolutionall aroundtheEarth,exceptintheauroralzone(invariant latitude

>

65◦).TheMFelectricfieldspectrogram(upto3MHz)isalsocontinuouslyrecorded.Fromtimetotime,the mag-neticandelectricfield experimentsare switchedinburstmodewherewaveformsare registeredupto20kHzinorderto haveabetterfrequencyandbettertimeresolutions.

Normallythefieldstrengthoftheelectromagneticwavesdecreaseswithdistancefromthesource,butintheionosphere orthemagnetosphere it couldbe enhanced duetointeraction withenergetic particles.The aimofthispaperisto show examplesofmanmadewavesemittedfromthegroundandrecordedintheionospherebyDEMETERatvariousfrequencies. Wavesemittedby VLFtransmittersarepresentedinsection 2,by ELFtransmittersinsection3,andbyelectricity net-works insection 4.Section 5displays examples ofELF waves generatedat highlatitudes by powerfulHF emissionsfor scientificpurpose.Conclusionsaregiveninsection6.

2. VLFtransmitters

Ground-based VLFtransmitters areused forcommunicationsby thearmy in differentcountries. Theyarepowerful in order that the signal can be received at very large distances. Normally, the emitted wave propagates in the waveguide formed bytheEarthsurface andthebottomof theionosphere,butthiswave canescapein theionosphere.Theireffects havebeenstudiedforalongtimebecausethewavepropagatesinthemagnetospheremainlyalongthemagneticfieldlines

Fig. 1. Thetoppanelrepresentsthespectrogramofanelectricfieldcomponentrecordedon30September2006between07:38and07:43UT.Thefrequency rangeisupto20kHz.Theintensityiscolorcodedaccordingtothecolorscaleontheright.Themiddle(bottom)paneldisplaystheelectrondensity (temperature).Below,thegeographiclatitudeandlongitudeareindicated,togetherwiththeL-valueandthegeomagneticlatitude.

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Fig. 2. ThemapshowsthelocationoftheVLFtransmitterNPM.ThepartoftheDEMETERorbitwheredataofFig. 1arerecordedisindicatedbytheblack line,whichisenlargedatthetimeoftheperturbation.

Fig. 2. Cettecartemontrelapositiondel’émetteurTBFNPM.Lapartiedel’orbitedeDemeteroùlesdonnéesdelaFig. 1sontrecueilliesestindiquéepar lalignenoire,quiestélargieàl’endroitdelaperturbation.

andcanprecipitate theparticleswhichareintheradiationbelts[2].DEMETERhasobservedtheseperturbations downin theionosphere[3–5].AfurtherexampleispresentedinFig. 1,whichdisplaystheelectricspectrogram,theelectrondensity, and the electron temperature recorded on 30September 2006close to the NPM transmitter(see Fig. 2). NPM is a VLF ground-based transmitterthatislocatedat21.42◦Nand158.15◦Wandemitsat21.4kHz.Duetoanaliasingproblem(the slope of the cut-off electronic filter isvery sharp,butNPM is very powerful), the transmitterfrequency lineappears at 18.6 kHzinthespectrogram.Onecanseealargeperturbationoftheelectrondensityandtemperaturewhichoccurssouth ofthetransmitter,becausetheemittedwavemainlyfollowsthemagneticfieldline.Simultaneouslyelectrostaticturbulence canbeobservedatlowfrequencies(

<

200 Hz)inthespectrogram.

DisturbancesduetoNPMhavebeenalsoshownin[6]and[7].OtherunexpectedeventsrelatedtotheinteractionofVLF transmitterwaveswiththeionospherecanbeseenin[8].

At higher frequencies, DEMETER observes also other transmitters, but their frequencies have less interaction with the ionosphericplasma. For example,the LORAN(Long-RAnge Navigation)transmittersin the northernhemisphere emit 100 kHzradiowavesformarinenavigation,whichcanberegisteredattheDEMETERaltitude[9].Broadcastingstationscan even bedetected inspace. Fig. 3 showsa map oftheEarthwheretheintensityoftheelectricfield recordedat162kHz is displayed.It isthe frequencyoftheFrench stationnamed“France Inter”ofwhichthe transmitterislocatedatAllouis (47◦10N,2◦12E).Itcanbeseenthatthespotcorrespondingtothetransmitterlocationisequatorwardshiftedduetothe magneticfield.Onecanalsoobserveothertransmittersatthesamefrequencyineasterncountries.

At HF frequencies not surveyedby DEMETER, it isalso possibleto record emissionscoming fromthe Earth’ssurface. Forexample,theexperimentWAVESonboardWINDhasobservedmanmaderadiotransmissionsat10.375MHz[10].Based on suchobservations,the authorsclaimedthatan extraterrestrialradioastronomerwillconcludethat theEarthplanetis populated.

3. ELFtransmitters

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Fig. 3. ThemapshowstheMFintensityoftheelectricfieldrecordedat162kHzbyDEMETER.Itcorrespondstoanaveragevalueoverthreeyears(2005, 2006,and2007).Theintensityiscolorcodedaccordingtothecolorscaleontheright.

Fig. 3. Lacartemontrel’intensitéduchampélectriqueenregistréedanslagammeFMà162kHzparDemeter.C’estunevaleurmoyennéesurtroisans (2005,2006,et2007).L’intensitéestcodéeencouleursuivantl’échelledecouleuràdroite.

Fig. 4. Spectrogramsofoneelectriccomponent(toppanel)andonemagneticcomponent(bottompanel)recordedon8December2007between18:44 and18:45UT.Thefrequencyrangeisupto300Hz.Theintensityiscolorcodedaccordingtothecolorscalesontheright.Inthebottom,thegeographic latitudeandlongitudeareindicated,togetherwiththeL-value.

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Fig. 5. MapoftheMurmanskarea.TheorbitofDEMETERisindicatedbytheblackline.ThethickpartcorrespondstothedatashowninFig. 4.Theinsert (enlargedinthetoprightcorner)isissuedfromtheWikipediawebpageoftheZEVStransmitter.Itshowsthelocationofthegroundantennae(orange lines).

Fig. 5. CartedelarégiondeMourmansk.L’orbitedeDemeterestindiquéeparunelignenoire.LapartieépaissiecorrespondauxdonnéesdelaFig. 4. L’insert(agrandidanslecoinenhautàdroite)vientdusiteWikipédiadel’émetteurZevs.Ilmontrel’emplacementausoldel’antenne(lignesorange).

Fig. 6. Spectrogramofanelectricfieldcomponentrecordedon1January2006between11:05:45and11:06:30UT.Thefrequencyrangeisupto2.2kHz. Theintensityiscolorcodedaccordingtothecolorscaleontheright.Inthebottom,thegeographiclatitudeandlongitudeareindicated,togetherwiththe

L-valueandthegeomagneticlatitude.

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Fig. 7. Spectrogramofanelectricfieldcomponentrecordedon6January2010between03:01:30and03:02:30UT.Thefrequencyrangeisupto5kHz. Theintensityiscolorcodedaccordingtothecolorscaleontheright.Inthebottom,thegeographiclatitudeandlongitudeareindicated,togetherwiththe

L-valueandthegeomagneticlatitude.

Fig. 7. Spectrogrammed’unecomposanteduchampélectriqueenregistréle6janvier2010entre03:01:30 et03:02:30 TU.Lagammedefréquencevarie jusqu’à5kHz.L’intensitéestcodéeencouleursuivantl’échelledecouleuràdroite.Lesvaleursdelalatitudeetdelalongitudegéographiquesontdonnées enbasainsiquelesvaleursdeL etdelalatitudegéomagnétique.

the night along the orbitshownin Fig. 5. The emission at82 Hzis clearly seen in the two panels,although there is a lotofelectrostaticturbulence(low-frequencywave)intheelectricspectrogrambecausethesatelliteisclosetotheauroral zone.ThiswavepropagatesatverylongdistancesintheEarth–ionospherewaveguide[11,12],butathigheraltitudesinthe ionosphere,thewaveisonlyobservedwhenthesatelliteisclosetotheemissionarea.

4. PLHR

Power Line Harmonic Radiation (PLHR) consists of ELF and VLF waves at the harmonic frequencies of 50 or 60 Hz radiated by electricpower systems on the ground. The frequency–time spectrograms of these events consist of several horizontal lines withseparation of 50/100 or60/120 Hz. Evidence of PLHR propagationin the magnetosphere was first obtainedfrom ground-based observations[13].A systematicstudy ofPLHR observationsby themicro-satellite DEMETER was performedin[14–17](see alsoreferencestoother observations therein).Theyshowedthatthe frequencyspacingof thelinescorrespondswelltothepowersystemfrequencyinpossiblegenerationregions.

Fig. 6presentsaneventrecordedaboveSpainon1January2006.Linesatfrequenciescloseto1846Hzand1946Hzcan beobservedaround11.06UT.Theintensebandofnoisewithafrequencybelow550Hzisnaturalandusuallyobservedby DEMETER.

AnotherexampleofPLHRsisgiveninFig. 7,whereparallellinesatfrequenciescloseto4227Hz,4327Hz,and4428Hz canbe observedaboveChina.The verticallinescorrespondtowaves(calledwhistlers)emittedinalarge frequencyrange andinducedbylightningstrokesintheatmospherebelowthesatellite.

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Fig. 8. Spectrogramofanelectricfieldcomponentrecordedon3October2009between15:19:30and15:20:30UT.Thefrequencyrangeisupto5kHz. Theintensityiscolorcodedaccordingtothecolorscaleontheright.Inthebottom,thegeographiclatitudeandlongitudeareindicated,togetherwiththe

L-valueandthegeomagneticlatitude.

Fig. 8. Spectrogrammed’unecomposanteduchampélectriqueenregistréle3octobre2009entre15:19:30 et15:20:30 TU.Lagammedefréquencevarie jusqu’à5kHz.L’intensitéestcodéeencouleursuivantl’échelledecouleuràdroite.Lesvaleursdelalatitudeetdelalongitudegéographiquesontdonnées enbasainsiquelesvaleursdeL etdelalatitudegéomagnétique.

Thevariationcanbeevenlargerforislandsnotconnectedtothenetwork:50Hz

±

2%(i.e.49Hzto51Hz)during95%of thetime,and50Hz

±

15%(42.5Hzto57.5Hz)duringtherestofthetime.

Sometimes PLHRs cannot be firmly distinguished, butnon-natural emissions are present, which can be attributed to industrial noiseoccurringbelowthesatellite. Anexampleis givenin thespectrograminFig. 8, whichhasbeenrecorded aboveChina(seealso[20]).Onecanseetheindustrialnoisebetween15:19:45and15:20:10UTupto3kHz.Verticallines areduetowhistlers.OtherexamplesrecordedaboveEuropecanbeseenin[21].

ThedatashowninFig. 9isrecordedintheSouthernHemisphereatalocationthatismagneticallyconjugatedtoFinland wheremanyPLHRscanbeobserved.Onecanseeseveraltriggeredemissionsandhooksthatseemtobeemittedataparent linefrequencycloseto1765Hz.ItmeansthatPLHRspropagateinthemagnetosphereandcantriggernewemissionsatthe equator dueto interactionwithparticles.Attheendthey areobservedinthehemisphereoppositetothePLHR emission. Thesehooksareverysimilartothosedetectedonthegroundin[18,19,22].

5. Activeexperiments

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Fig. 9. Spectrogramofanelectricfieldcomponentrecordedon17December2009between18:13:10and18:14:10UT.Thefrequencyrangeisupto4kHz. Theintensityiscolorcodedaccordingtothecolorscaleontheright.Inthebottom,thegeographiclatitudeandlongitudeareindicated,togetherwiththe

L-valueandthegeomagneticlatitude.

Fig. 9. Spectrogrammed’unecomposanteduchampélectriqueenregistréle17décembre2009entre18:13:10 et18:14:10 TU.Lagammedefréquencevarie jusqu’à4kHz.L’intensitéestcodéeencouleursuivantl’échelledecouleuràdroite.Lesvaleursdelalatitudeetdelalongitudegéographiquesontdonnées enbas,ainsiquelesvaleursdeL etdelalatitudegéomagnétique.

ThedatashowninFig. 10isrecordedcloseto themagneticallyconjugatedpoint ofHAARP.At2 kHz, onecanseethe regularpulsestriggeredbytheHAARPheatingexperimentintheNorthernHemisphere(rampsarealsoemittedfrom1to 2 kHz). Butafter propagationinthe Southern Hemisphere,it is shownthat thesepulsestrigger hooks almostsimilar to thosetriggeredbyPHLRs,whicharedisplayedinFig. 9.

6. Conclusions

IthasbeenshownthatmanydifferentmanmadewaveswereemittedinawidefrequencyrangefromtheEarth’ssurface. Theypropagateintheionosphereandtheninthemagnetosphere.Dependingontheirfrequencies,theycaninteractinthe magnetospherewithparticlesornot.Thecorrespondinginteractionmechanismsarewellknown(see,forexample,[25]and referencestherein).Theimportanceofthesemanmadewavesincomparisonwithnaturalwavesmustbeevaluated.Inthe past,some examples havebeenpresented [26,27].It isclearthat VLF transmittersperturbthe radiationbelts[4,28], but ithasbeen shownin[17] thatPLHRs donot haveaglobalinfluenceon theVLFwave activityinthe ionosphere,even if wehaveexamplesoftriggeredemissions.ThisVLFwaveactivityismainlyrelatedtothethunderstormactivity(whistlers). AnotherexplanationisthatPLHRmayinfluencethisthunderstormactivity,butitisnotconfirmed.

Acknowledgements

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Fig. 10. Spectrogramofanelectricfieldcomponentrecordedon23August2007between22:04and22:05UT.Thefrequencyrangeisupto4 kHz.The intensityiscolorcodedaccordingtothecolorscaleontheright.Inthebottom,thegeographiclatitudeandlongitudeareindicated,togetherwiththe

L-valueandthegeomagneticlatitude.

Fig. 10. Spectrogrammed’unecomposanteduchampélectriqueenregistréle23août2007entre22:04 et22:05 TU.Lagammedefréquencevariejusqu’à 4 kHz.L’intensitéestcodéeencouleursuivantl’échelledecouleuràdroite.Lesvaleursdelalatitudeetdelalongitudegéographiquesontdonnéesenbas, ainsiquelesvaleursdeL etdelalatitudegéomagnétique.

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[13]R.A.Helliwell,etal.,VLFlineradiationintheEarth’smagnetosphereanditsassociationwithpowersystemradiation,J.Geophys.Res.80 (31)(1975) 4249–4258.

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