1. Tracking of ENA Emissions Jörg-Micha Jahn P. C. Brandt M. G. Henderson D. McComas D. Mitchell C. J. Pollock, G. D. Reeves R. Skoug M. F. Thomsen P. Valek Yosemite Workshop 07 Feb 2002

2. Overview Radial propagation and substorm timing. “Azimuthal” propagation at low energies. Correlating precipitating with drifting particles.

3. Determine the injection speed by two-spacecraft time delay measure- ments using CRRES and LANL/Geo. Extend beyond geosynchronous => increase in speed expected.

4. Method: Elliptical Grid Centered on Earth Superimpose a polar grid over ENA images and track emission intensity as a function of time for fixed grid regions (i.e. grid cell clusters). Comparison of clusters yields spatial sym- metries and emission propagations.

5. 24 Sep 2000 onset 24 Sep 2000 Explanation of Plot Format Individual traces correspond to different pixel clusters, orga- nized in decreasing angular distance from the image center from bottom to top or black to red, respectively.

6. 24 Sep 2000 onset Radial Propagation Inside geosynchronous injections will move with 25-50 km/s radially, i.e. at least 0.5 R E per spin.

7. Angular distance in ENA images does not necessarily translate in radial distance in units of L! This may lead to apparent outward propagation. Apparent Radial Plasma Motion of ENA Emissions

9. Substorm timing Determine onset time with integrated ENA fluxes at various energies. Onset is less abrupt than in auroral or in situ data. Onset times for MENA, FUV, and LANL EP for a random set of events. 1.0 - 2.3 keV 2.3 - 5.3 kev 5.2 - 12.0 kev 11.6 - 27 kev 19 Sep 2000 {

10. Radial propagation is not “sharp” Compressed ENA view at higher latitude field lines makes it difficult to see radial propagation. But … ENA propagation direction in raw images is not necessarily known a priori. (?) Substorm timing Onset times can be determined from integrated ENA measurements. Initial increase is gradual compared to auroral and in situ data. Onset time compares remarkably well, considering the difficulties. There is a systematic MENA to LANL offset.

11. Azimuthal propagation of (M)ENA’s Is there a detectable drift of particles below 10 keV? 11:40 UT Measuring the drift speed gives L-shell of population  provides a consistency check with inversion results. Will not work below ~10 keV! 11:00 UT

12. “Azimuthal” propagation of (M)ENA’s

14. Correlating precipitating and drifting particles keogram rebinning

15. Correlating precipitating and drifting particles

17. Using resampled ENA images to track the development of emissions. We measure: spatial properties, propagation, and timing of events. A limiting factor is the uncertainty of the emission source location due to the line-of-sight character of ENA measurements. Radial propagation cannot be consistently shown with images alone (exception PS?), but it may show with IMAGE – in situ comparisons. Timing of event onset can be done well and consistently. Onset ENA flux is initially weak, it has a long rise time and slow decay. For the first time we observe significant low E flows (1.0 keV and above). Comparison to FUV images: onset timing, local time distribution / timing. => next: comparing inverted ion distributions with mapped FUV data. Summary