The Ionosphere and its Impact on Communications and Navigation

Tim Fuller-RowellNOAA Space Environment Center and

CIRES, University of Colorado

Customers for Ionospheric Information

High Frequency (HF) Communication (3-30MHz) ground-to-ground or air-to-ground communication establish accurate maximum useable frequencies support automatic link establishment systems

e.g., civilian aviation, maritime, frequency managers

Single Frequency GPS Positioning and Navigation single frequency potential sub-meter accuracy positioning

e.g., civil aviation, advanced vehicle tracking, potential for E911improvements

Dual Frequency GPS Positioning and Navigation decimeter accuracy 10-50 cm

e.g., real-time kinematic (RTK), autonomous transportation, off-shoredrilling and exploration

rapid centimeter accuracy positioning 1-2 cm e.g., surveyors, possible InSAR (land radar) applications

Customers for Ionospheric Information Satellite Communication

specification and forecast of scintillation activity e.g., satellite operators, drilling companies

Situational Awareness Depressed maximum useable frequencies

Steep horizontal gradients

Unusual propagation paths

Larger positioning errors

High probability of loss of radio signals

The Thermosphere and Ionosphere

Electron Density Profile

Vertical profile of electron density from GPS/MET comparedwith Millstone Hill incoherent scatter radar observations

0

1 0 0

2 0 0

400

5 0 0

6 0 0

7 0 0

1.0E+

3

1.0E+

4

1.0E+

5

1.0E+

6

Altit

ude (

km)

E le c tro n D e n s ity ( 1 /cm ^3 )

M ills t o n e ( P L = 4 4 8 ) , 4 2 . 6 N , 7 1 . 5 W , 1 3 : 2 8 : 0 0 U T C

G P S / M E T , # 0 0 0 3 , 4 6 . 9 N , 5 7 . 5 W , 1 3 : 2 9 : 3 2 U T C

P IM ( @ # 0 0 0 3 )

300

Courtesy:Chris Rocken

NCAR

Solar Flares

Coronal Mass Ejections

Solar Proton Events

Solar Flares Increased X-ray fluxD-region ionization

Arrival time: 8 minutesDuration: 1-2 hours

Effects:HF absorptionDisruption of low frequencynavigationGPS navigation

Users: mariners, coast guard,HF frequency managers,commercial aviation, military

Solar Proton EventsHigh energy particles

Arrival time: 15 mins to few hoursDuration: several days

Effects:Single event upsets (SEU)Deep dielectric chargingHF absorptionLow frequency navigation outageRadiation hazard

Users: satellite operators, HFfrequency managers, commercialaviation, mariners, astronauts, ..

Coronal Mass EjectionsGeomagnetic Storm

Arrival time: 1-3 daysDuration: 1-2 days

Effects:Spacecraft chargingSatellite dragHF CommunicationsGPS NavigationInduced currents

Users: Power companies,satellite operators, HF frequencymanagers, FAA, military, GPS,...

Effect of Solar X-rays on D-Region and HF Propagation.

D-Region Absorption Product based on GOES X-Ray Flux (SEC Product) The map shows regions affected by the increased D-region ionization resulting

from enhanced x-ray flux during magnitude X-1 Flare

Solar X-raysGOES

Dayside responseZenith angle dependenceTime scale follows source

SHORTWAVEFADE (SWF)

00 241812

MAXIMUMUSEABLEFREQUENCY

LOWESTUSEABLEFREQUENCY

X-RAY EVENT

06

TIME

FR

EQ

UE

NC

Y(M

Hz)

0

5

10

15

USEABLEFREQUENCYWINDOW

Solar Flares:HF AbsorptionRadio Blackout

Radio Wave PropagationFort Collins, CO to Cedar Rapids, ID

Signal Strengthat 10 MHz

00 241812060

5

10

15dusk dawn

night day

Radio Wave PropagationFort Collins, CO to Cedar Rapids, ID

Signal Strengthat 10 MHz

00 241812060

5

10

15dusk dawn

Flare

TEC GPS Differential Phase measurements

Equatorial African station, near noon

X17

Solar Protons

PCA depends on solar illuminationO2 - e- attachment process in the D-region

Combined X-ray and PCA

Coronal Mass Ejection

A single eruption can release a billion tons ofmaterial into the solar windSpeeds can exceed several million miles perhourEnergetic particles accelerated by shocks cause bright flashes inthe image (andin DNA!)

Increased energy input to the upperatmosphere: auroral particleprecipitation and magnetosphericconvection electric field

Epc 10 - 300 kV in minutes

Large temperature and circulation changesin the upper atmosphere

Oxygen Depletions Imaged from Space

wipe out ionosphere

Strong correlation betweenO/N2 and ionospheric

depletions

STORM product

The geomagnetic storm onMonday August 18th 2003wiped out the normaldaytime peak in TEC andelectron density over NorthAmerica

Normal quiet-day maximumon August 17th

Ionospheric depletion onthe 18th during the storm

Ionospheric TEC using data assimilation techniques

Electrodynamics

Penetration and dynamoelectric fields can strengthenthe EIA and deepen equatorialholes.

Ring current polarizationelectric fields can transportionospheric plasma andproduce troughs

Huge gradients in plasmadensity ensue.

CHAMP (400 km) OSEC: HalloweenMannucci et al. 2005

One of the challenges:

October 29th, 2003stationary walls of TECcompromise integrity of

LAAS

TEC walls:130 TEC units over 50 km

20 m of GPS delay;walls move 100 to 500 m/s

SED?wall

Courtesy: Tom Dehel, FAA

Steep TEC gradients increaseGPS positioning errors

5m

High correlation betweendisruption of WAASavailability and TEC gradients

The Kalman Filter andextracting information

Primary Product: Vertical TECReal-time ionospheric maps of total electron

content every 15 minutes

Slant-Path TEC Maps2-D maps of of slant path TEC over the CONUSfor each GPS satellite in view updated every 15minutes

Applications:1. Ionospheric correction for single frequency GPS and NDGPS positioning2. Dual-frequency integer ambiguity resolution for rapid centimeter accuracypositioning

Sat. 1

Sat. 5

Sat. 14

Sat. 29

.etc

A

A

A

A B

B

B

B

C

C

C

C

C

Scintillations

Distribution of high scintillation events

Courtesy:Paul Straus

Aerospace Corporation

and Maps

Signal-to-noise ratio

Electron Density [log/m3]

Storm

Quiet

4.4LT

Basu et al. 2001

Bite-outs

HeavyFluid

LightFluid

Ionosphere

Steep bottomside densitygradient during / after sunset

Fluid instability analog(Rayleigh-Taylor instability)

ScintillationsHeavyFluid

LightFluid

Plasma Bubbles

WBMOD: empirical model

physicalmodeling

GUVI Nighttime FUV IonosphereObservations

I = ne2 dse + O+ O* (135 nm)

Longitude

Latit

ude

Depleted Flux Tubes

App

leto

n A

nom

aly

Magnetic Equator

CourtesyAPL

Motivation: Planetary wave periodicities in daysideionosphere? H inferred Drifts using a Neural Network algorithm between March 13 (73) and April 14 (105), 2004

-30

-20

-10

0

10

20

30

40

50

0 4 8 12 16 20 24

Local Time (hours)

Dri

fts

(m/s

)

DOY = 73DOY = 74

DOY = 75

DOY = 76

DOY = 77DOY = 78

DOY = 79

DOY = 80DOY = 81

DOY = 82

DOY = 83DOY = 84

DOY = 85

DOY = 86DOY = 87

DOY = 88

DOY = 89

DOY = 90DOY = 91

DOY = 92

DOY = 93DOY = 94

DOY = 95

DOY = 96DOY = 97

DOY = 98

DOY = 99DOY = 100

DOY = 101

DOY = 102DOY = 103

DOY = 104

DOY = 105

Avg.Avg._IFM

Dayside electrodynamics during 2001

Possible PW signaturesElectrodynamics drives plasma transport

Courtesy D. Anderson & A. Anghel (2006)

Mid-latitude day-to-day variability inionospheric total electron content

El Nio

GW

PW

Tides

QBOSA

O

Electrodynamics

Scintillations

Ionospheric Bubbles

Courtesy of Rashid Akmaev

Tidal signatures in nightside EquatorialIonospheric Anomaly

IMAGE composite of 135.6-nm O airglow (350-400 km) for March-April 2002 andmagnitude of tidal temperature oscillations at 115 km (Immel et al., 2006).

Many of the space weather effectson communication and navigationare a consequence of the responseof the upper atmosphere to solarflares, coronal mass ejections, andsolar proton events

Day-to-day variability can alsoarise from the connectionsbetween terrestrial and spaceweather

Conclusion