1. Dynamics of the AMPERE R1 Oval during substorms and SMCs
L. B. N. Clausen1, J. B. H. Baker2, J. M. Ruohoniemi2, S. E. Milan3, B. J. Anderson4, and S. Wing4
1 Technical University of Braunschweig
2 Virginia Tech
3 University of Leicester
4 Johns Hopkins University Applied Physics Laboratory

2. Typical AMPERE Data: 2124-2134 UT on 12 December 2010
Clausen et al., 2012

3. Fitting a Bipolar Shape to Latitude Profiles of Current Density
Clausen et al., 2012

4. MLT Fits to the R1 Oval in Both Hemispheres
Northern Hemisphere
Southern Hemisphere
Strong Currents
Weak Currents
Clausen et al., 2012

5. R1 Oval Location vs. DMSP Particle Boundaries

6. Interhemispheric Variations of R1 Oval for Two Multi-day Events
Non-Storm
Storm-Time
IMF Bz
Sym-H AL
Jnorth L0
L0(error)
Jsouth L0
L0(error)
Clausen et al., 2012

7. R1 Oval & Magnetospheric Modes
Substorm (Themis list)
SMC (courtesy J. Kissinger)
Auroral Imager
R1 Oval size
Avg. R1 current
R1 flux
AU Index
AL Index
IMF Bz

8. Summary and Conclusions
The AMPERE dataset provides widespread continuous observations of field-aligned current densities in both hemispheres simultaneously.
A technique has been developed for fitting an MLT-profile to the Region-1 field-aligned currents to produce a radius for the “R1 oval”.
An superposed epoch analysis of the behavior of the R1 oval during substorms and SMC events confirms the standard paradigm:
The R1 oval expands and contracts during the substorm cycle
The R1 oval remains reasonably steady during SMC events
The R1 oval is therefore a valuable magnetospheric index!!!!

9. References
Clausen, L. B. N., J. B. H. Baker, J. M. Ruohoniemi, S. E. Milan, and B. J. Anderson, “Dynamics of the region 1 Birkeland current oval derived from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE)“ J. Geophys. Res., doi: /2012JA017666, in press, 2012.
Kissinger, J., R. L. McPherron, T.-S. Hsu, and V. Angelopoulos, “Steady magnetospheric convection and stream interfaces: Relationship over a solar cycle“, J. Geophys. Res., 116, A00I19, doi: /2010JA015763, 2011.

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