Terrestrial Ionosphere(s)

Jan J Sojka

Center for Atmospheric and Space Sciences Utah State University, Logan, Utah 84322

• PART I: Local Ionospheric processes, and terrestrial ionospheres • PART II: global I/T system

Heliophysics Summer School XI: Boulder, Colorado 7 August, 2017

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Material adopted from the following authors.

• HSS lecture notes prepared by Professor Tim Fuller-Rowell (volume 1 HSS text book) • HSS Chapter 13 volume 3 text book by Professor Stan Solomon. • Robert Schunk and Andrew Nagy: their text “Ionospheres”, a Cambridge press Atmospheric and Space Science Series book.

Thanks also to Dana Longcope upon whose presentaon I will build. The take-away message from this talk would be an appreciaon of how important a narrow layer in our ionosphere is for various heliophysics processes.

This layer has various names:

SAIR (definions will come later) E-layer Turbopause Pedersen and Hall conducvity layer Altudes from 100 to 120 km

Heck it even applies to the Sun! Neutral Atmospheres

• All ionospheres exist in an atmosphere. • The thermosphere-ionosphere forms the neutral to plasma interface between planets with atmospheres and space. • The composion of the ionosphere is governed by the atmosphere, chemistry, and the ionizing radiaon. • The atmospheric dynamics influences the Apart from photons what ionosphere. other forms of ionizing radiaon are there?

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 470

420 O O o H 2 He N LATITUDE = 45 2 LOCAL TIME = 15:00 370

320

270 ALTITUDE (km) ALTITUDE 220

170

120 104 105 106 107 108 109 1010 1011 DENSITY (cm-3)

The Earth’s thermospheric composion: the basis for the ionosphere

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Earth’ s Upper Atmosphere’s dependence upon the Sun’s solar cycle and our Seasonal and day-night cycles. [ courtesy of NRLMSIS-00E ]

The solar cycle is effecve only above 100 to 120 km!

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 160

140 THERMOSPHERE 120 112 km 102 km 94 km 100 100 to 120 km Altitude (km) 80 Mauersberger et al. (1968) Kasprzak et al. (1968) DeVries et al. (1970) 60 MESOSPHERE

40 0.01 0.1 1 10

n(Ar) /n(N2 ) ( relative scale ) Lower atmosphere has turbulent mixing which leads to constant composion.

Above the turbopause the neutral species are in their own hydrostac equilibrium.

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Neat fact about the upper atmosphere

140 n(O) / n(O2) K AT 120 km cm2 s-1 130 2.0 2.3 x 106 1.0 4.5 x 106 120 0.5 9.0 x 106

110

N2

ALTITUDE (km) ALTITUDE 100

LOCAL O 90 PHOTOCHEMICAL 2 EQUILIBRIUM O

80 1010 1011 1012 1013 1014 CONCENTRATION (cm -3 )

In the terrestrial upper atmosphere atomic oxygen is produced.

Atomic oxygen is associated with its own chemistry reacons.

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Venus and Mars are viewed as having terrestrial ionospheres hence they need terrestrial atmospheres.

A lot of CO2 and then a different chemistry produces atomic O.

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Ionospheres • Ionospheres exist in a neutral gas. • The relave plasma to neutral density is variable, for terrestrial planets it is less than 1%. • The dayme plasma is mainly produced by solar EUV and so X-ray ionizaon. • The night me plasma is created by resonantly scaered sun light, Star light, Cosmic Ray ionizaon. • Auroral charged parcles from the magnetosphere produce ionizaon, hence plasma. • The ionosphere is electrically coupled to the magnetosphere by providing electrical conducvity If you had to guess at channels. what altudes are these conducvity channels?

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 What does the Earth’s ionosphere look like?

+ + 900 He , H

800 PROTONOSPHERE

700

600 500

400 IONOSPHERE + F2 o ALTITUDE (km) ALTITUDE 300

200 F1 + + + E O2 ,N2 ,NO 100 D 0 In what way does the 103 104 ionosphere corrupt GPS 105 106 ELECTRON DENSITY (cm-3) geolocaon accuracy?

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 800 Atomic O+: F2-Layer is the main layer for 700 Earth’s Ionosphere. 600

Above the peak it is in diffusive equilibrium with its plasma scale 500 height. 400 Below the peak chemistry ALTITUDE (km) ALTITUDE dominates, but molecular 300 chemical composion creates a large equilibrium range of chemical reacons and diffusive temperature dependencies. 200 equilibrium 103 104 105 106 107 ELECTRON DENSITY (cm-3)

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Earth’s ionosphere chemistry-simplified

Are reacon rates between specific species constant values?

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 360

+ + 320 CO2 H

280 NO+ O + Mars has an 240 2 Ionosphere! 200 Altitude (km) 160 O+ 120 The ionosphere is 101 102 103 104 105 dominated by the Number Density (cm-3) molecular ion O2+. On the Earth the molecular ion peak is called the E-region.

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Venus also has an ionosphere.

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Photoionizaon

• The Solar EUV irradiance is key. • Only recently has the short wavelength component become rounely observable. • Proxy indices are less than sasfactory! • NASA: satellites TIMED(SEE) and SDO(EVE) have provided high resoluon spectral and now temporal informaon about EUV irradiance variability.

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Solar EUV and Soft X-Ray Flux photoelectron escape flux

photodissociation photoionization; ion- electron pair production incoming EUV particle flux So X-rays spectrum secondary & tertiary ionization 1 nm to 10 nm to excited species; chemistry 10nm 120 nm

transport processes ( e. g. molecular diffusion, thermal conduction)

airglow

NO and CO2 are very neutral gas heating ion heating electron heating effecve IR radiators that cool the upper- energy loss to the atmosphere. mesosphere

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Would someone like to describe the purpose of this slide?

h ! Z

atmosphere Solar Zenith angle geometry planetary surface

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Normalized wicked Chapman producon rate profiles for various solar zenith angles.

Relave Producon Rate

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 800 800

720 Tn Tn 700 Ti 640 Ti 600 560 Te

480 Te 500

400 400

HEIGHT (km) HEIGHT 320 (km) HEIGHT 300 240 200 160 200 800 1400 2000 2600 3200 120 400 800 1200 1600 2000 2400 2800 3200 TEMPERATURE (°K) TEMPERATURE (°K) Dayme thermal profiles for the thermosphere and ionosphere at Millstone Hill, MA. A midlatude locaon: le panel 14:22 LT, right panel 02:22 LT at What does Exospheric equinox in 1970. Temperature refer to?

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 If the planet has no significant magnec field, hence devoid of a magnetosphere, the atmosphere with photoionizaon is the PHYSICS needed to generate the ionosphere.

But we on Earth are lucky and have a magnetosphere hence we get even more PHYSICS to complicate our ionosphere!!!

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Lets take a break Auroral Ionizaon

• The magnetosphere generates ionizaon via energec parcles, usually electrons. • These parcles are energized in the magnetosphere and create ionizaon and heang in the thermosphere-ionosphere. • Auroral displays are the manifestaon of this process. • Ionospheric conducvity is a dynamic “resistor” in the M-I electro-dynamics (MHD).

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 6 different auroral electron populaons and their deposion altudes

Standard auroral displays have characterisc energies between 3 and 8 keV.

At what altudes do the 3 to 8 keV The altude of ionizaon depends upon the energy of the auroral parcles auroral electrons produce most of their ionizaon? Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405

Electric Fields and Winds

• In the F-region the electric field (and neutral winds) can induce plasma dris to raise and lower the F-Layer. • This modifies the plasma diffusion balance and hence density and profile shape. • Joule heang of the atmosphere depends on the Pedersen conducvity and the square of the electric field. • At all latudes E X B can transport plasma At what altudes perpendicular to the magnec field line. would Joule Heang be maximized?

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 What process are charged parcles obeying that prevents them following the wind or electric field? An Eastward Electric field together with the magnetic field creates an upward plasma drift.

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 EQUATOR

The low latude day me ionosphere is dominated by transport caused by the Eastward electric field. This results in plasma redistribuon and the formaon of the Appleton Anomaly (equatorial anomaly).

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 800 EQUATOR 5.20 5.60 5.405.20 700 5.40 5.00 5.80 5.60 5.60 5.80 600 5.80 6.00 5.80 500 6.00 6.00 6.20 6.20 6.00

400 6.00 6.40 ALTITUDE (km) ALTITUDE 300

200 -24 -18 -12 -60 6 12 18 24 S DIP LATITUDE N The Appleton anomalies also known as the Equatorial anomalies.

The F-region densies are shown as Log10 Ne (cm**-3)

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 POLARCAP-AURORAL LATITUDES

12 DE-2 orbit tracks 70o

-0.1 18:00 MLT 18 6 06:00 MLT

0 Midnight

Observed ionospheric plasma dri velocies measured from DE-2 over-layed with a corresponding 2-cell electric field paern

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 POLARCAP-AURORAL LATITUDES

O+ F2-layer is the dominant ionospheric layer under quiet geomagnec condions. The height is about 300 km.

100 mV/m electric field, large!

However, during very disturbed geomagnec condions the rapid conversion of O+ into NO+ leads to a E/F1 layer becoming dominant. The peak height drops to 150 km!

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 • Morphology of the global ionosphere is a systems level problem. • Many physics processes operate together as a system but in different latude regions. • Historically studies aempted to understand these processes individually and then “assimilate” their net effects……. NOT A GOOD APPROACH not a linear superposion problem!

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Auroral Precipitation Joule Dissipation Solar EUV Plasmaspheric Downflow Starlight & Scattered Radiation Meteors UV Radiation X-rays Very Energetic Particle Precipitation F1 - Region E - Region Lower Thermosphere

D-Region Mesosphere

Tides and Gravity Waves

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405

1200 MLTMT

Even simple E X B is complex because there are two separate sources of E

The ionosphere co-rotates, 1800 0600 implying an E field, and 3 then the magnetosphere’s 80 8 7 E field maps into the 2 4 5 1 70 6 ionosphere and an 60 atmospheric dynamo generated yet 50 Another E field. 0000

LABEL 1 2345678 CIRCULATION 1.00 1.01 0.10 1.34 0.50 0.31 0.18 0.11 PERIOD (day)

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 GEOGRAPHIC LOCAL TIME COORDINATES

The F-region plasma as seen in a geographic local me from executes very complicated trajectories!

This means that a ground based observatory at high latudes is not monitoring the same plasma flux tube connually, and hence the observer is not seeing the plasma evoluon!

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405

STORM on 7/8 January 2005 Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Can you list important properes of the Earth’s ionosphere between 100 and 120 km?

SAIR : Sun Atmosphere Interacon Region

But also

SAIR: Space Atmosphere Interacon Region

340 O 300 260

NO O 220 2 CO Altitude (km) 180 CO2 140 N2 100 102 104 106 108 1010 1012 Number Density (cm-3)

MARS, it also has an atmosphere!

Atomic oxygen is also present, as is a lot of carbon dioxide. hmF2 EQUIVALENT PARABOLIC LAYER ym F2 foF2

E-F VALLEY Height E-F REGION foF1

hmE E LAYER

ho foE Plasma Frequency

Nomenclature and simple mathemacal funcons for the ionosphere. Neat fact about the ionospheres SMIN vercal profile 5 400 4 (a) 350 3 Tn Ti 300 2 T ns HEIGHT (km) 1 250 Te 0 200 ZP -1 -2 150 -3 -4 120 -5 -6 100 -7 SMAX 5 Tn T 4 (b) i 500 3 400 2 350 1 300 HEIGHT (km) 0 250 200 ZP -1 Tns -2 Te 150 -3 -4 120 -5 -6 100 -70 200 400 600 800 10001200140016001800 TEMPERATURE (°K)

A natural coordinate for the atmosphere is the pressure level! (a)

(b) The Earths magnec field is a poor dipole!

But many models sll use a dipole representaon! 1200 MLT

1800 0600 -5 -15 -25 25 15 5 80 70 60 50

0000

Schemac polar plot of the electric field called a 2-cell paern.

The F-region plasma E X B dri trajectory direcons are shown by the arrows. The effect of the E X B induced electric field (or wind) on the ionospheric ALTITUDE (km) 500 600 700 800 100 200 300 400 10 3 density and profile. ION DENSITY (cm ) 10 a 4 b 10 5 c -3 10 6 UT = 19.00 Z = 2.0 AVE HT = 286.3 90

60

30

0

LATITUDE -30

-60

-90 (a) -180 -150-120 -90 -60 -300 30 60 90 120 150 180 LONGITUDE 400 m/s 90

60

30

0

LATITUDE -30

-60

-90 (b) -180 -150-120 -90 -60 -300 30 60 90 120 150 180 LONGITUDE

Thermospheric wind field are altude dependent and responsive to Changes in magnetospheric energy input, STORMS.

12-24-68 at 1217 Ti Te 400 6-26-68 at 1225

300

ne Ti Te 200

ALTITUDE (km) ALTITUDE 100

0 0 500 1000 1500 2000 0 4 8 12 16 5 -3 TEMPERATURE (°K) ELECTRON DENSITY ( x 10 cm )

The auroral electrons precipitaon leads to heang and density increases/decreases in the ionosphere

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Back of envelope calculaon!

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405 Thermal Energy Density

Combining neutral density and temperature produces the altitude distributions of the thermal energy density. Deposition region

Altitude [km]

3 Log10 Thermal Energy Density [J/m ]

Ctr. Atmos. Space Science, 4405 Old Main Hill, Logan, UT 84322-4405