Monitoring Space Weather with GPS
Anthea J. Coster
USES OF GPS
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NAVIGATION
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GEODETIC
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STEERING GOLF CARTS, ROUTES FOR TAXI CABS
FAA/AIR TRAFFIC CONTROL (WAAS and LAAS)
Tracking pigeons!
EARTHQUAKE PREDICTION/MONITORING PLATE MOTION
ICEBERG TRACKING AND OFFSHORE OIL EXPLORATION
PRECISE SURVEYING
EARTH SCIENCE
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WATER VAPOR MEASUREMENTS
IONOSPHERIC MAPPING, STUDIES OF TIDS (TRAVELING
IONOSPHERIC DISTURBANCES)
GPS Space Segment
Block II/IIA
Block IIR
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24-satellite (nominal) constellation
Six orbital planes, four satellites per
plane
- 55 deg inclination
Semi-synchronous, circular orbits
(~20,000 km altitude)
Global Positioning System
ERROR SOURCES
• GPS CLOCK ERROR
• RECEIVER NOISE
• MULTIPATH
•TROPOSPHERE
•IONOSPHERE
x,y,z,t
Atmospheric Propagation
Illustration of Atmospheric Effects
Elevation Refraction
Range Delay
Ionospheric Delay as a Function of Frequency
Types of GPS Processing
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SPS - Standard Position Service (L1 frequency only)
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pseudorange measurements made by single, simple standalone receiver
PPS - Precise Positioning Service (L1 and L2)
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encrypted P-code (Y-code) available to authorized users
synthesized P-code
(pseudoranges plus
L2 carrier available)
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DGPS and RTK –
Differential GPS and
Real-time kinematic
Map of GPS Sites
Scripps Orbit and Permanent Array
Center (SOPAC)
Distributed
networks of
sensors yield
global physics
unattainable
with singlepoint
measurements
Global Positioning System:
Very Precise Navigation
By measuring
Delay (path length)
to each satellite…
N 42.61950°
E 288.50827°
Receiver has a simple ionospheric thickness model
Global Positioning System…
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 derive
Ionospheric information! (Total Electron Content)
Solar Flare of 14 July 2000
Biggest Solar Storm in Nine Years
Strikes Earth
Est. Planetary Kp (3 Hr.)
Begin: 2000 Jul 14 0000 UT
NOAA/SEC Boulder, CO USA
es
GPS Loss of Lock at Millstone Hill
TEC Disturbances on 15 July 2000
Florida site
Florida site
GPS Total Electron Content Map
Illustration of Storm Enhanced Density
A Decade Of Storm Enhanced Density
Day 77, 1990
Day 101, 2001
Day 90, 2001
Day 149, 2003
Nov 2003
Space
Weather
Effects
GPS derived maps
of Total Electron
Content (TEC) in
Earth’s Upper
Atmosphere
>1000 GPS
Receivers
Global Storm Response Using GPS Data
Apr 2001
Space
Weather
Effects
GPS derived maps
of Total Electron
Content (TEC) in
Earth’s Upper
Atmosphere
>1000 GPS
Receivers
Global Storm Response Using GPS Data
Northern Europe and American Sector SED Plumes
Northern
Europe
American
Sector
20 Nov 2003 18:20 UT
High Latitude
Mid-Latitude
Low Latitude
Storm-time Electric Fields
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Cross-tail electric fields energize and inject particles
into the inner magnetosphere forming the
disturbance Ring Current
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Strong storm-time penetration eastward electric field
uplifts equatorial ionosphere
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Enhances the Equatorial anomaly
Sub-auroral polarization Stream forms – which is an
electric field that is radially outward at the equator
and poleward at higher latitudes. Where the SAPS
field overlaps the region of enhanced electron
density in the mid-latitudes
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Storm-Enhanced Density (SED)
Ring Current / SAPS/ SED Plume
(Sub Auroral Polarization Stream Electric Field)
Duskside Region-2 FACs
close poleward across lowconductance gap
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AURORAL
OVAL
SAPS: Strong poleward
Electric Fields are set up
across the sub-auroral
ionosphere
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SAPS erodes the cold
plasma of the ionosphere
and the outer plasmasphere
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LOW S
SAPS E FIELD
Figure courtesy of J. Foster
21:00 UT
Key West
Downwelling
Guiana
Uplift
Polar Convection
• 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
ExB
E
Dusk
Dawn
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.
Plasmasphere
Plasmaspheric Tails and Storm Enhanced
Density
IMAGE Data of Plasmasphere
Conjugacy Examples
Conjugacy Examples
Conjugacy Examples
Aurora in New Brunswick, Canada
30 October 2003
Aurora as seen in Big Bend, Texas
30 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