1. REPRESENTATION OF PLASMA TEMPERATURES IN IRI
Vladimir Truhlik
Department of the Upper Atmosphere
Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic
Praha, Czech Republic

2. Outline Introduction Tools Data Theoretical model Plasma temperatures
Theory and basic processes
Representation in IRI
Electron temperature
Ion temperature
Swarm, LP data, access
Conclusions
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3. Introduction
Knowledge of characteristics of ionized part in the Earth‘s outer atmosphere is important for studying of many phenomena especially propagation of electromagnetic signals (artificial – GPS; natural - VLF - whistlers, emissions etc.)
Most important parameters which we study:
Electron density (Ne) (propagation of radio waves)
Ion composition (e.g., waves - whistler mode – LHR Lower Hybrid Resonance – important mean ion mass)
Plasma temperatures (thermal balance, important for transfer of energy, scale height etc.)
Electron temperature (Te)
Ion temperature (Ti)
Drifts etc.
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4. IRI model Ne electron density – parameter of prime interest
Electron temperature, ion temperature, ion composition (O+, H+, He+, molecular ions), drifts, ionospheric electron content (TEC), F1 and spread-F probability
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5. Tools – data Data base – satellite data
All available Te satellite data (source mainly NSSDC, ISAS, and PIs of individual experiments)
Year-altitude coverage of the data sets include in our data base. The curve at the top shows the solar 10.7 cm radio flux (F10.7 index – 3 months average).
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6. Tools – model Field Line Interhemispheric Plasma (FLIP) flow model
(e.g. Richards, 2001; Richards, 2002)
Includes:
Continuity and momentum equations along the field line for O+, H+, He+, and N+.
Energy balance equations for electrons and ions. Geometry of tilted offset dipole
Two stream photoelectron model
Photochemical equilibrium below 500km for ions NO+, O2+, N2+, O+(2P), and O+(2D)
Continuity and momentum equations for minor neutral species NO, O(1D), N(2D), and N(4S) from 100 to 500km in each hemisphere
ExB drift
Inputs:
EUV from EUVAC model
Horizontal winds from HWM model or from equivalent winds obtained from measured hmF2
Neutral densities and temperature from the MSIS model
Equatorial drift from e.g., Fejer-Scherliess model
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7. Ionospheric plasma
Ionosphere-plasmaphere system, part of the inner magnetosphere (interacts with regions below and above)
Ionization of neutral atmosphere by solar EUV or energetic particles precipitation
Energy of particles<1eV, high density (up to 1013 m-3)
Quasi-neutrality
Strong solar control, transport along magnetic field lines (upper ionosphere F2 region, topside ionosphere, plasmasphere, high latitude region)
ExB drifts (equatorial region, high latitudes)
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8. Plasma temperatures
Thermal motion of particles (electrons and ions) E=3/2kT
Electron temperature (Te)
Ion temperature(s)
Temperature of neutral particles – important (Tn) up to >500km
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9. Plasma temperatures
Equation of energy balance (for particle i – ions or electrons)
n-density
T-temperature
k-Boltzmann constant
κ- (kappa) thermal conductivity
Q-source and loss of energy
A – cross section of the flux tube
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10. Electron temperature
Equation of thermal balance (day, night – steady state - neglect changes with time)
Qe – heating (from photoelectrons)
local <350km
non-local plasmaspheric
Le – cooling – very complex – energy loss:
<350km neutral particles O, N2(r,v), O2 (r,v)
topside with ions O+, H+, He+ (Coulomb)
Ke – thermal conductivity
I – inclination of the geomagnetic field
FLIP electron cooling rates in the equtorial region up to 350km
as a function of altitude for various cooling terms (Coulomb —, rN2 —, rO2 —, vN2 —, vO2 —, fsO ……, O1D …..).
Coulomb cooling in the topside is dominant
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11. Electron temperature – altitude profiles in topside and plasmasphere
Thermal conductivity
Te profile – constant heat flux
Te0, G0 – electron temperature and gradient (e.g. at 500km)
LSA
HSA
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12. Ion temperature Equation (neglect time changes, neglect heat flux)
Qi – heating from electrons
(Coulomb heating)
Li – cooling:
neutral particles O, N2, O2
and other ions (O+, H+, He+ )
Resonant charge exchange
Polarization reactions
Rees and Roble, Rev. Geoph. and Sp. Ph., 1975
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13. IRI Te model Bil-1985- based on Brace and Theis Te maps (JASTP 1981)
coordinates diplat and solar local time
TTSA option (JASR 2001) replaced by new TBT-2012
(EPS, 2012)
IRI2012/IRI2016
JF(2)-.true./.false. - Te,Ti computed/not computed
JF(23)-.true./.false.-Bil-1985/TBT-2012
Ne/Te correlation (Brace and Theis, 1978)
- JF(10) -.true./.false.-Te – Standard /Te - Using Te/Ne correlation
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14. Ne/Te correlation
Brace and Theis, 1978
IRI 300 and 400km
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15. Ne/Te correlation validity? Hinotori, daytime, equatorial latitudes
Kakinami et al., JGR 2011
“U” shape
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16. TBT-2012 Te model Employs the all available satellite Te data
Include solar activity variation for day and night - an example for 550km and equinox:
Employs minimum of independent coordinates
to solve problem of limited data coverage
Longitudinal structure neglected when it is used latitude coordinate based on the configuration of the real magnetic field
coordinates invdip and magnetic local time
Te PF10.7=200
Te PF10.7=150
Te PF10.7=90
Corrected Te model
Data empirical profile
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17. Magnetic latitude coordinates
diplat:
where I is the dip angle or magnetic inclination
-longitudinal variation of Te reduced in equatorial latitudes
Invariant latitude – invl (e.g. Roederer 1970):
where the invariant radius R and the McIlwain L parameter obey
-longitudinal variation of Te reduced at mid-latitudes (Smilauer and Afonin, ASR 1985) – plasma distributed along magnetic field lines
invdip – combination of diplat and invl (Truhlik et al. 2001):
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18. invdip (or invdiplat) magnetic local time (MLT)
modified latitude – invdip (ASR Vol.27, No.1, 101,2001)
longitudinal variation reduced to a second order effect
____ invdip _ _ _ dip latitude
____ invdip _ _ _ invariant latitude
Configuration of the real geomagnetic field (IGRF 1990 at 600km)
in different latitude coordinates in steps of 10°
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19. Data base – satellite data
All available Te satellite data (source mainly NSSDC, ISAS, and PIs of individual experiments)
Year-altitude coverage of the data sets include in our data base. The curve at the top shows the solar 10.7 cm radio flux (F10.7 index – 3 months average).
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20. Te model - Data distribution
KOMPSAT
DMSP
ISIS 2 AE
ISIS 2
IK 24
ISIS 1
Hinotori
9 million points – non-uniform distribution
highest population corresponds to circularly orbiting satellites
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21. Main (core) Te model equinox solstice 350km 550km
Data grouped - altitudes: 350, 550, 850, 1400 and 2000km
seasons: equinox, solstice
A system of associated Legendre polynomials up to the 8th order was employed.
Plm = associated Legendre function
θ = invdip colatitude (0..π)
ϕ = magnetic local time (0..2π).
350km
550km
Te increases with altitude.
At low latitudes (±30 invl) during the nighttime the Te altitude gradient is very small.
Morning enhancement (morning overshoot) at equatorial latitudes and at low altitudes (350, 550 to 850 km)
For solstices its maximum is shifted to the the winter hemisphere
Dependence on invariant latitude is more prominent at lower altitudes (350 to 850 km).
Generally the lowest electron temperature is observed close to the equator and increases with increasing invariant latitude.
850km
1400km
2000km

22. Model of the solar activity variation
Solar activity variation of Te
Qe and Le depend on solar activity – increase with increasing solar activity
Te can increase, decrease or stay constant with increasing solar activity depending on altitude, latitude, local time and season
=>
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23. Model of the solar activity variation
Driven by PF10.7 index PF10.7=(F107A+F107D)/2
Normalized latitude profiles of Te for 3 levels of solar activity for day (13h MLT) and night (1h MLT):
a) low PF10.7 < 110
b) medium 110 <= PF10.7 < 180
c) high F10.7=>180)
Quadratic fit inside 110 <= PF10.7 < 180; Outside linear extrapolation
Local time dependence approximated by a harmonic function
Obtain a correction function TePF107(mlt,invdip,PF107)
For fixed altitude and local time Te(mlt,invdip,PF107)=Te(mlt,invdip)+TePF107(mlt,invdip,PF107)
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24. Solar activity correction function – example for 550km equinox
∆Te/K
PF10.7=(F10.7D+F10.781)/2
Solar activity correction function—an example for 550 km equinox. * represent the normalized values from the normalized latitudinal profiles for low, medium and high solar activity. The dashed line represents a mathematical interpolation/extrapolation in solar activity using the three values.
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25. Model of the solar activity variation of Te
To include solar activity variation instead of Ti data use FLIP simulated values and the similar way as for TBT-2012 to use following approach:
Driven by PF10.7 index PF10.7=(F107A+F107D)/2
Normalized latitude profiles of Ti for 3 levels of solar activity for day (13h MLT) and night (1h MLT) and also dawn (6h MLT) and dusk (18h MLT):
a) low PF10.7 < 110
b) medium 110 <= PF10.7 < 180
c) high F10.7=>180)
-Quadratic fit inside 110 <= PF10.7 < 180; Outside linear extrapolation
-Local time dependence approximated by a smooth function
-Obtain a correction function TePF107(mlt,invdip,PF107)
For fixed altitude and local time Ti(mlt,invdip,PF107)=Ti(mlt,invdip)+TiPF107(mlt,invdip,PF107)

26. Latitude profiles of Te
high medium low solar activity

27. Solar activity correction function – example for 550km equinox
∆T/K
PF10.7

28. IRI Ti representation Tn Ti Te Altitude profiles (e.g. Bilitza, 1990):
IRI-2012 or IRI-2016
Altitude profiles (e.g. Bilitza, 1990):
- at the altitude of 200km Ti = Tn
- Tn from MSIS(86) – includes solar activity variation
430km Ti from the AEROS A model (latitudinal profiles for day and night, Bilitza 1981)
Ti <= Te in topside
Tn <= Tn <=Te Tn Ti Te
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29. Ion temperature - proposed model
Data altitudes: 350km, 550km, 850km, 1000km
Latitude (invdip) and MLT
2 seasons, equinox no hemispheric differences
Modeling grid 9x18=162 bins
Spherical harmonics (orthogonal system) up to 8th order
Plm = associated Legendre function
θ = invdip colatitude (0..π)
ϕ = magnetic local time (0..2π).

30. Contour plots of Ti – new Ti model
equinox
solstice
Ti increases with altitude.
At low latitudes (±30deg invl) during the nighttime the Ti altitude gradient is very small.
Morning enhancement (morning overshoot) at equatorial latitudes (550, 850 km)
For solstices its maximum is shifted to the the winter hemisphere
Generally the lowest ion temperature is observed close to the equator and increases with increasing invariant latitude.
350km
550km
850km
1000km

31. Relation of Te, Ti and Tn
IRI Tn Tn Ti Ti Te
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32. New data access - Swarm mission
Project of ESA
Primary purpose – monitoring of the geomagnetic field
Launch date - 22 November 2013 (almost four years of data)
Constellation of three identical satellites
Satellite A (Alpha) + C (Charlie)
Altitude: ~480km, inclination: 87.4°
side-by-side flying (Δlon: 1.4°, ΔLT:6min)
160km distance at equator
Orbital delay: 6s
Satellite B (Bravo)
Altitude: ~520km, inclination: 88°
All satellites 270 days to cover all LT
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33. Swarm mission - orbit Satellite local time Orbit altitudes
Separation of the satellites - evolution
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34. Swarm mission – future plans
D. Sieg – Swarm DQW Oct. 2017
Preference - keep Swarm
alive at least one solar cycle
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35. Swarm mission - experiments
Payload
Vector Field Magnetometer (VFM)
Absolute Scalar Magnetometer (ASM)
Electric Field Instrument (EFI)
Accelerometer (ACC)
Laser Range Reflector (LRR)
Measurement of density, temperature, drift velocity and electric field
Thermal ion imager (TII)
Langmuir probes (LP)
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36. Langmuir probes - Swarm EFI
Developped by IRF Uppsala
2 probes:
Probe 1 in high gain, probe 2 in low
Probe 1 – nitrated titanium (TiN)
Probe 2 gold-plated titanium (Au)
Data from probes telemetred to ground
Principle: 128Hz applied to the I-V characteristics
Measure the resulting current
“ripple” technique, harmonic (sub)mode – used ~99%
1% classical sweep
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37. Langmuir probes – access to data
Various products released
0.5s Ne, Te - Provisional data set “PREL” (ASCII) (until July 2015) (harmonic mode, merged hi and low gain probes)
0.5s Ne, Te – Level 1b, Operational data set “OPER” (cdf) – (harmonic mode, high gain) from July 2015
16Hz Ne - Faceplate plasma density (limited interval) only for validation
0.5s Extended data set (both hi and low gain separately) only for validation
128s Ne, Te sweep mode - only for validation
ftp://swarm-diss.eo.esa.int/
Many products still in validation/correction/calibration process but it is already provided for scientific community - after registration
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38. Conclusions
Global models of electron and ion temperatures are included in IRI
These models include most important dependencies (on latitude, altitude, local time, and solar activity)
Only limited spatial resolution - up to the 8th order of spherical harmonics
More data is needed to better describe small scale features (anomalies, enhancements, troughs, longitudinal dependency etc.)
Better description of parameters depending on solar/magnetic activity variation especially during period of current very different solar cycles from those which were known during previous decades
It is important task to include independent Ti model
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