Monitoring Space Weather with GPS

Anthea J. Coster

USES OF GPSUSES OF GPS

NAVIGATIONNAVIGATION STEERING GOLF CARTS, ROUTES FOR TAXI CABSSTEERING GOLF CARTS, ROUTES FOR TAXI CABS FAA/AIR TRAFFIC CONTROL (WAAS and LAAS)FAA/AIR TRAFFIC CONTROL (WAAS and LAAS) Tracking pigeons!Tracking pigeons!

GEODETICGEODETIC EARTHQUAKE PREDICTION/MONITORING PLATE MOTIONEARTHQUAKE PREDICTION/MONITORING PLATE MOTION ICEBERG TRACKING AND OFFSHORE OIL EXPLORATIONICEBERG TRACKING AND OFFSHORE OIL EXPLORATION PRECISE SURVEYINGPRECISE SURVEYING

EARTH SCIENCEEARTH SCIENCE WATER VAPOR MEASUREMENTS WATER VAPOR MEASUREMENTS IONOSPHERIC MAPPING, STUDIES OF TIDS (TRAVELING IONOSPHERIC MAPPING, STUDIES OF TIDS (TRAVELING

IONOSPHERIC DISTURBANCES)IONOSPHERIC DISTURBANCES)

Block II/IIA

Block IIR

GPS Space SegmentGPS Space Segment

24-satellite (nominal) constellation24-satellite (nominal) constellation Six orbital planes, four satellites per planeSix orbital planes, four satellites per plane

- 55 deg inclination55 deg inclination Semi-synchronous, circular orbits (~20,000 Semi-synchronous, circular orbits (~20,000

km altitude)km altitude)

Global Positioning SystemGlobal Positioning System

ERROR SOURCES

• GPS CLOCK ERROR

• RECEIVER NOISE

• MULTIPATH

•TROPOSPHERE

•IONOSPHERE

x,y,z,t

Atmospheric PropagationAtmospheric Propagation

Illustration of Atmospheric EffectsIllustration of Atmospheric Effects

Elevation Refraction Range Delay

Ionospheric Delay as a Function of Frequency

Types of GPS ProcessingTypes of GPS Processing

SPS - Standard Position Service (L1 frequency only)SPS - Standard Position Service (L1 frequency only) pseudorange measurements made by single, simple stand- alone pseudorange measurements made by single, simple stand- alone

receiverreceiver

PPS - Precise Positioning Service (L1 and L2)PPS - Precise Positioning Service (L1 and L2) encrypted P-code (Y-code) available to authorized usersencrypted P-code (Y-code) available to authorized users synthesized P-code synthesized P-code

(pseudoranges plus (pseudoranges plus

L2 carrierL2 carrier available)available) DGPS and RTK – DGPS and RTK –

Differential GPS and

Real-time kinematic

Map of GPS Sites Map of GPS Sites Scripps Orbit and Permanent Array Scripps Orbit and Permanent Array

Center (SOPAC)Center (SOPAC)

Distributed Distributed networks of networks of

sensors yield sensors yield global physics global physics unattainable unattainable with single-with single-

point point measurementsmeasurements

Global Positioning System:Global Positioning System:Very Precise NavigationVery Precise Navigation

By measuringDelay (path length)to each satellite…

N 42.61950° E 288.50827°

Receiver has a simple ionospheric thickness model

Global Positioning System…Global Positioning System…Affected By Space Weather!Affected By Space Weather!

Ionospheric density changes - so delay changes (locally).

Receiver doesn’t know this…

Wrong position…

But – we can turn it around and deriveIonospheric information! (Total Electron Content)

Solar Flare of 14 July 2000Solar Flare of 14 July 2000Biggest Solar Storm in Nine Years

Strikes Earth

Est. Planetary Kp (3 Hr.) Begin: 2000 Jul 14 0000 UT es

NOAA/SEC Boulder, CO USA

GPS Loss of Lock at Millstone HillGPS Loss of Lock at Millstone Hill

Florida siteFlorida site

TEC Disturbances on 15 July 2000

GPS Total Electron Content MapGPS Total Electron Content MapIllustration of Storm Enhanced DensityIllustration of Storm Enhanced Density

A Decade Of Storm Enhanced DensityA Decade Of Storm Enhanced Density

Day 77, 1990

Day 149, 2003Day 101, 2001

Day 90, 2001

Nov 2003Nov 2003Space Space

WeatherWeatherEffectsEffectsGPS derived mapsof Total Electron Content (TEC) in Earth’s Upper Atmosphere

>1000 GPS Receivers Global Storm Response Using GPS Data

Apr 2001Apr 2001Space Space

WeatherWeatherEffectsEffectsGPS derived mapsof Total Electron Content (TEC) in Earth’s Upper Atmosphere

>1000 GPS Receivers Global Storm Response Using GPS Data

Northern Europe and American Sector Northern Europe and American Sector SED PlumesSED Plumes

NorthernEurope

AmericanSector

20 Nov 2003 18:20 UT20 Nov 2003 18:20 UT

High Latitude

Mid-Latitude

Low Latitude

Storm-time Electric FieldsStorm-time Electric Fields Cross-tail electric fields energize and inject particles Cross-tail electric fields energize and inject particles

into the inner magnetosphere forming the into the inner magnetosphere forming the disturbance Ring Currentdisturbance Ring Current

Strong storm-time penetration eastward electric field Strong storm-time penetration eastward electric field uplifts equatorial ionosphereuplifts equatorial ionosphere

Enhances the Equatorial anomaly Enhances the Equatorial anomaly

Sub-auroral polarization Stream forms – which is an Sub-auroral polarization Stream forms – which is an electric field that is radially outward at the equator electric field that is radially outward at the equator and poleward at higher latitudes. Where the SAPS and poleward at higher latitudes. Where the SAPS field overlaps the region of enhanced electron field overlaps the region of enhanced electron density in the mid-latitudesdensity in the mid-latitudes

Storm-Enhanced Density (SED) Storm-Enhanced Density (SED)

AURORAL OVAL

LOW

SAPS E FIELD

Ring Current / SAPS/ SED PlumeRing Current / SAPS/ SED Plume(Sub Auroral Polarization Stream Electric Field)(Sub Auroral Polarization Stream Electric Field)

Duskside Region-2 FACs Duskside Region-2 FACs close poleward across low-close poleward across low-conductance gapconductance gap

SAPS: Strong poleward SAPS: Strong poleward Electric Fields are set up Electric Fields are set up across the sub-auroral across the sub-auroral ionosphereionosphere

SAPS erodes the cold SAPS erodes the cold plasma of the ionosphere plasma of the ionosphere and the outer plasmasphereand the outer plasmasphere

Figure courtesy of J. Foster

21:00 UT

Uplift

Downwelling

Guiana

Key West

Polar ConvectionPolar Convection

E

E x B

Dusk Dawn

• The SAPS electric field produces a westward plasma flow at subauroral latitudes

• Some plasma travels through dayside cusp into polar regions where it becomes entrained in the polar convection and carried over the pole

Plasmasphere

extension of ionosphere and part of the inner magnetosphere.

filled with ionospheric plasma from the mid- and low latitudes

plasma gas pressure is equalized along the entire field line.

plasma co-rotates with the Earth and its motion is dominated by the geomagnetic field.

Plasma on magnetic field lines associated with higher latitudes (~ above 60 deg. geomagnetic lat.) is convected to the magnetopause

Quiet conditions - plasmapause may extend to ~ 7 Earth radii

Disturbed conditions – plasmapause can contract to ~3 or less Earth radii.

PlasmaspherePlasmasphere

Plasmaspheric Tails and Storm Plasmaspheric Tails and Storm Enhanced DensityEnhanced Density

IMAGE Data of IMAGE Data of PlasmaspherePlasmasphere

Conjugacy ExamplesConjugacy Examples

Conjugacy ExamplesConjugacy Examples

Conjugacy ExamplesConjugacy Examples

Aurora in New Brunswick, CanadaAurora in New Brunswick, Canada30 October 2003

Aurora as seen in Big Bend, TexasAurora as seen in Big Bend, Texas30 October 2003

SUMMARY

Electric Fields generated in the magnetosphere are imposed on the ionosphere during geomagnetic storms and dramatically rearrange ionospheric plasma and “empty out” the plasmasphere

Networks of ground-based receivers can contribute to our understanding of these processes

We are excited about the developing networks of atmospheric sensors in Africa