TheEarthsIonosphere and
the EISCATradar
AnjaStrømme
NorwegianSpaceCenter/UNIS
Outline
• Some basic radarconcepts
• Theionosphere
• Radarmeasurements andphenomenas inthe Earthsionosphere
Radar
• RADAR(RAdio DetectionAndRanging)
• isatechniquefordetectingandstudying
remotetargetsbytransmittingaradiowave
inthedirectionofthetargetandobserving
thereflectionofthewave.
• Radar isanobjectdetectionsystemwhich
usesradiowavestodeterminetherange,
altitude,direction,orspeedofobjects.
(wikipedia)
DopplerRadar
• Inordertodetect the velocity of the targetwe are takingadvantage
of aconcept called DopplerShifts
• We are rather familiar with itwhen if comes tosoundwaves
DopplerShift
• Ifthe target(car)isdrivingtoward the
observer,the soundwaves are
compressed,andthe frequency of the
car hornappears higher
• Ifthe target(car)isdrivingaway from
the observerthe soundwaves are
elongated andthe frequency of the
car hornappears lower
• Asthe target(car)passesthe observer
the frequency of the car hornseem to
change frequency (drop tolower
frequency)
Incoherent=Random, viz. Incoherent scatter is the process by which
radiowaves are randomly scattered by electrons in the ionosphere
DopplerRadar– timedomain
DopplerRadar– frequencydomain
f0
f0
DopplerRadar– frequencydomain
f0
f0 Man Dog
f0
f0
f0
?
f0
f0
f0
Howcan we use this method here?
...andhere?
Photo:AnjaStrømme
Scatteringfromchargedparticles
• When acharged paraticle is
subjected toanelectriomagnetic
wave,itstartoccilating with the
wave
• When acharged particle occilates
if emitts enelectromagnetic wave
• Sobyradiating anelectron with a
radarwave,the electron
becomes atiny antennaitself and
radiates power inalldirections
Thermalfluctuatingelectrons
Wherearetheionosphericelectrons
comingfrom?
Likemostthings on Earth– itallstartson the Sun...
UVradiation
UVandEUVradiation isdrivingEarthsenergy balance,andare responsible for
anionosphere with charged particles inthe upper partof our atmosphere.
15.02.2017
19
ElectronDensityprofile
A complex balance
between the ionization
and recombination and
diffusion results in an
altitude dependent
electron (and ion) density
profile.
TheSunisanactive star!
15.02.2017
TheSunisanactive star...Mostdays...!
15.02.2017
Athighlatitudeselectron(andproton)withsolarwindorigincreates
additionalionization,seenasauroraborealis/australis dispays
Athighlatitudeselectron(andproton)withsolarwindorigincreates
additionalionization,seenasauroraborealis/australis dispays
Athighlatitudeselectron(andproton)withsolarwindorigincreates
additionalionization,seenasauroraborealis/australis dispays
Athighlatitudeselectron(andproton)withsolarwindorigincreates
additionalionization,seenasauroraborealis/australis dispays
Athighlatitudeselectron(andproton)withsolarwindorigincreates
additionalionization,seenasauroraborealis/australis dispays
OpticalversusRadarAurora
Radarssees
this
Cameras sees
this
EISCATSvalbardRadar(ESR)
EISCATMeasurements
EISCATMeasurements
EISCATMeasurements
EISCATMeasurements
Daytimeandnight timeAurora– the Auroral ovaland
the Polarcusp
Daytimeandnight timeAurora– the Auroral ovaland
the Polarcusp
EISCATMeasurements
Typicalmodes:Scans
Movie: Craig Heinselman
Resolvedvelocity,electrondensity,ionandelectron
temperaturefromSondrestrom
Space/Timeambiguity
ALTITUDE(km)
800
RawNe
Typicalmodes:dwells
Ne Temperature
ni
400
0
1010 1011 10121010 1011 1012 200 400
Ne (m–3)
Ne (m–3)
TEMP(K)
–400 0 400
ni (ms–1)
Stationary antenna– active aurora
Some scienceexamples
Substorm
Substorm
Substorm
Substorm
Substorm
Substorm
PolarMesospheric SummerEchoes (PMSE)
PolarMesospheric SummerEchoes (PMSE)
Sedimentationofaerosols
gravity
altitude
~88 km; the mesopause, T < 100º
K
~82 km; NLC altitude, T ≈ 150º
K
temperature
Sedimentationofaerosols
gravity
altitude
~88 km; the mesopause, T < 100º
K
Subvisible charged ice
aerosols
Visible charged ice
aerosols
~82 km; NLC altitude, T ≈ 150º
K
temperature
Withthenakedeye,wecanonlysee
thetipoftheiceberg
Withthenakedeye,wecanonlysee
thetipoftheiceberg
PMSE
NLC
RelativelocationofNLCandPMSE
Eclipse1.August2008
Sondrestrom,~76%at~09:05UT
ESR,~93%at~09:40UT
EISCATVHF,~76%at~09:40UT
URSI2008GAChicago
Eclipse 20.March 2015
Eclipse 20.March 2015
?
Spring,Summer,Autumn,Winter
EISCATSvalbardRadarIPYdata
LocationofhighlatitudeIncoherentScatterRadars
AnjaStrømme,CEDARUtah,16.June
2008