1. THEMIS and ARTEMIS David G. Sibeck THEMIS Project Scientist NASA/GSFC 2/17/2007 Cape Canaveral

2. Outline Substorms NASA’s THEMIS mission Recent results Status and Future plans

3. Earth’s Magnetosphere SW Earth’s dipole magnetic field carves out a cavity in the oncoming supersonic solar wind..... J B B

4. Solar Wind Pressure Variations Variations in the solar wind dynamic pressure (nMV 2 ) buffet the magnetosphere,

5. But the IMF Orientation Controls the Interaction… …which generally turns out to be unsteady….

6. Our own Dedicated Array of THEMIS Ground Observatories Shows Just how Unsteady!

7. Themis Mission Objective: Distinguish Between Two Substorm Models … Current Disruption Reconnection Implosion near Earth Equatorward arc brightens Explosion far from Earth Poleward arc brightens

8. Flows ? Rarefaction wave ? P2 P3 P4 P5 GBO P1 THEMIS Mission Objective: Pinpoint When, Where, How Energy Stored in Magnetotail is Released First distant magnetotail and poleward arc Or First near magnetotail and equatorward arc?

9. SPACECRAFT AND INSTRUMENTS SST ESA EFIa EFIs FGM SCM T spin =3s FIVE IDENTICALLY-INSTRUMENTED SPACECRAFT (128 kg), EACH CARRYING: ESA: Electrostatic analyzer measures 0.003-30 keV ions/electrons (UCB) SST: Solid state telescopes measures 0.03-6 MeV ions and electrons (UCB) FGM: Fluxgate magnetometer measures magnetic field to 128 Hz (Germany) SCM: Search coil magnetometer measures 0.001 - 4 kHz magnetic field (France) EFI: Electric field instrument on wires and axial booms 0.0003 - 400 kHz (UCB)

10. 5 THEMIS Spacecraft Line Up Once/4 Days in Tail Sun

11. Case study addressed our primary objective: Argued that distant tail reconnection triggers substorm onset (not vice-versa) Vassilis Angelopoulos et al. [2008] “I see flows consistent with reconnection in the distant tail followed by auroral brightening, currents, and pulsations at the ground, and then dipolarization in the near-Earth tail. This indicates reconnection drives substorms“ …but see comment [Lui, 2009], reply [Angelopoulous, 2009]

12. T Rx T AI T CD 3 rd 1 st 2 nd 3 rd 1 st 2 nd Timing of ground and space: Vz 123123 TIMELINE Time the wiggles and demonstrate their sense is consistent with reconnection. What about arcs? ?

13. If the substorm begins far from Earth, why does the most equatorward arc (mapping to near Earth) often appear to brighten first? Nishimura et al. [2009] argue that it doesn’t! 1 Initial Brightening 2 3 Equatorward arc

14. Nishimura et al. propose this model to resolve contradiction Aurora FeatureMagnetotail Feature 1Poleward boundary intensifiesReconnection begins in distant tail 2N/S arc moves equatorwardEarthward flow 3Contact with existing arcContact with near-Earth plasma sheet 4Azimuthal drift along growth phase arc Azimuthal drift in response to increasing pressure gradient 5BreakupInstability in near-Earth tail Out In Hi-Lat Low-Lat

15. [Runov et al., 2009] Earthward-moving Observations prompt Simulations Earthward Match old MHD simulations [Hesse et al., 1998] and prompt new full particle simulations [Sitnov et al., 2009]

16. Pc1 Waves Propagate Outward From Footprint on the Ground Model Observations Audience: Please Help Remind Speaker To Show Movie NOW! Magnetoseismology with Pc 1 (1 Hz) Waves [Rae et al., 2009 Spring AGU Press Release]

17. Direct Evidence for Magnetic Field Lines Resonating at Individual Frequencies Multiple spacecraft validate the magnetic field line resonance model [Sarris et al. Feb 2009]: Disturbances cause each field line to oscillate at its own natural frequency, determined by its length and the mass it carries 1-30 mHz

18. What Comes Next? THEMIS and ARTEMIS P1=TH-B P2=TH-C P3=TH-D P4=TH-E P5=TH-A Daily orbits, new interspacecraft separations in meridional plane Lissajous and Lunar orbits

19. How ARTEMIS Reaches the Moon

20. What ARTEMIS will do at the Moon For Heliophysics When Moon is in the Magnetosphere: –Reconnection, particle acceleration, turbulence When Moon is in the Solar Wind: –Reconnection, particle acceleration, turbulence Near the Moon: –Lunar wake, electric fields, particle acceleration

21. If Planetary has funding, ARTEMIS will optimize orbits and operations to study…. Dust Levitation in Electric Fields: –Monitor input and study lunar electric field –Use reflectometry to study surface electric field –Provide local electric field, particles to LADEE LADEE dust detector detects response to input Lunar Exosphere –Composition, distribution of: exospheric ions sputtered ions regolith –Exospheric variations with solar activity, cycle Lunar Surface and Interior –Crustal magnetic fields –Conductivity depth profile –Surface charging P1 P2 LADEE Exospheric or Sputtered ions Secondary and photo-electrons reveal regolith properties Core? P2P1 Conductivity

22. ARTEMIS and Exploration First operational use of Lunar Lissajous orbits (LL1 & LL2), useful for: –Staging lunar landings –Positioning communications relay stations at the moon (Station-keeping requirements thus far unknown) ARTEMIS’s 6 month residence in LL1&LL2 provides: –Good estimate of station-keeping fuel requirements –Proof of operational requirements (frequency/magnitude of thrusts) needed –Rapid transition of knowledge to NASA centers for future planning LL1LL2 ~120000 km To Earth Moon TOP VIEW SIDE VIEW Moon

23. Summary THEMIS –A mission to determine the cause of geomagnetic substorms employing 5 S/C and a dedicated array of ground observatories… –Case studies addressing primary objective completed, statistical studies underway! Recent results from the extended THEMIS mission –Working on reconciling conflicting substorm observations Future plans –Outer two THEMIS spacecraft go to the Moon: ARTEMIS –Inner three THEMIS S/C continue core mission All data public: Need your help analyzing!