Geospace Electrodynamic Connections (GEC) Mission Definition Joseph M. Grebowsky, GSFC Jan J. Sojka, USU Rod A. Heelis, UTD On Behalf of the Entire GEC-STDT (Visit our website at http://sec.gsfc.nasa.gov/gec.htm) Huntsville 2000 A New View of Geospace (October 31, 2000)
Joseph M. Grebowsky, GSFC
Jan J. Sojka, USU
Rod A. Heelis, UTD
On Behalf of the Entire GEC-STDT
(Visit our website at http://sec.gsfc.nasa.gov/gec.htm)
A New View of Geospace
(October 31, 2000)
Geospace Electrodynamic Connections
Jan J. Sojka*
Utah State University
Rod A. Heelis*
William A. Bristow
Geophysical Res. Inst.
James H. Clemmons
John C. Foster
Michele M. Gates
Robert S. Jankovsky
NASA/Lewis Res. Ctr.
Tim L. Killeen
* STDT Chairs
Univ. of Iowa
Larry J. Paxton
William K. Peterson
Robert F. Pfaff, Jr.
Art D. Richmond
Jeff P. Thayer
Janette C. Gervin
Joseph M. Grebowsky
GSFC Study Scientist
James F. Spann
HQ Program Scientist
Joule HeatingGravity Waves Auroral Arcs Sub-auroral DriftsField FluctuationsConvection BoundariesStorms and Substorms
Few seconds to > hour
< 1 km to > 1000 km
Single satellite measurements cannot resolve space and time variations.
GEC’s multi-point measurements will reveal the spatial and temporal variations.
Electromagnetic Energy Transfer Rate
The ionosphere provides a Hall and Pedersen conductivity layer to enable closure of magnetosphere currents and energy exchange between the magnetosphere and the I-T system.
The closure process involves collisional interactions that change the conductivity and thus the energy exchange between the magnetosphere and the I-T system.
How Does the I-T System Respond to Magnetospheric Forcing?
• Largest Effects are below 300 km
• No Global Picture below 300 km
• Different physics above and below 300 km
1) How is the magnetospheric E field and particle input into the I-T system structured in space and time?
2) How does Joule heating affect the I-T system?
3) How do E fields affect winds and composition in the I-T system?
4) How do magnetospheric influences extend to middle and low latitudes?
Above 300 km described by DE
To answer these questions GEC must:Discover the spatial and temporal scales for the magnetospheric inputs.Determine the spatial and temporal scales for the response.Quantify the altitude dependence of the response.
How is the I-T System Dynamically Coupled to the Magnetosphere?
1) How do atmospheric dynamo processes modify the energy flow between the magnetosphere and the I-T system?
2) What controls the connections between horizontal gradients in conductivity, electric fields, currents, and neutral winds?
3) How does the I-T system affect field-aligned currents and Alfven waves that connect it to the magnetosphere?
To answer these questions GEC must:Discover The important spatial and temporal scales that change the energy flow between the I-T system and the magnetosphere.
Determine which altitude regions in the I-T system contribute to coupling at different spatial and temporal scales.
Why Deep Dipping to 130 km or Lower?
At 130 km
Ion Collision Frequency equals Ion Gyrofrequency
Pedersen conductivity peaks
Joule heating energy deposition peaks
Ion velocity vector departs from E B direction by about 45
Science - to - Mission Requirements
R=Required ; E=Enhances Science Objective ; N=Not Required for Science Objective
Dips to 130 km perigee and Petal orbits for altitude discrimination are required to fully achieve the science objectives.
GEC’S SPACECRAFT MULTIPLE SCALE MEASUREMENTS
Since 4th s/c follows 1st we have effectively:
Pearls-on-a-string configuration with uneven spacing obtains information on many time/spatial scales
In Situ Neutral/Plasma Detectors
Cylindrical Shape, Rounded Front Face
Body-mounted Solar Arrays
E&M Field Instruments on Deployable Booms
Large Propellant Tanks
Pearls-on-a-String Orbit Configuration
Plot is for 2000X130 km orbit, perigee at 65o.
Traversal time plotted ~ 14 minutes.
Plot is for 2000X130 km orbits with arguments of perigee at 65, 60 , 55 and 50 degrees.
Nominal 2000 X 185 km orbit in blue. Dips to 130 km in red
October 2000 Status
GEC SCHEDULE (9/08) Launch)