1. THEMIS SRR 1 UCB/SSL, July 8-9,2003 THEMIS Science Requirements Dr. Vassilis Angelopoulos Principal Investigator Space Sciences Laboratory University of California, Berkeley

2. THEMIS SRR 2 UCB/SSL, July 8-9,2003 THEMIS primary objectives Aurora Understand substorm onset and evolution (baseline mission, primary objective) As a minimum: Where does substorm eruption start? (ionosphere, CD, Rx ?). MAGNETOSPHERE SOLAR WIND EQUATORIAL PLANE Themis overcomes: Meridional onset confinement (GBOs) Mapping distortions (in situ probes) Global timing (GBOs-probes)

3. THEMIS SRR 3 UCB/SSL, July 8-9,2003 Events that comprise the substorm Current Disruption Auroral Eruption Reconnection

4. THEMIS SRR 4 UCB/SSL, July 8-9,2003 Flows Primary Objectives, Goals and Means Onset and evolution of substorms Time History of Events (Onset)… –Delineate cause and effect Measure When  Where … and Macroscale Interactions during Substorms (Evolution) –Coupling in the magnetosphere Measure plasma flows and waves –Coupling to the ionosphere Measure currents and structures Distinguishes among competing models: impartially answers a well-posed question… Current Disruption Model timeEvent 0 secCurrent Disruption 30 secAuroral Eruption 60 secReconnection Reconnection Model timeEvent 0 secReconnection 90 secCurrent Disruption 120 secAuroral Eruption ? ? Rarefaction wave ? P1 P2 P3 P4 P5 GBO …as implied by Themis, goddess of impartial justice

5. THEMIS SRR 5 UCB/SSL, July 8-9,2003 Mission elements Probe conjunctions along Sun-Earth line recur once per 4 days over North America. Ground based observatories completely cover North American sector; determine auroral breakup within 1-3s … … while THEMIS’s space-based probes determine onset of Current Disruption and Reconnection each within <10s. : Ground Based Observatory

6. THEMIS SRR 6 UCB/SSL, July 8-9,2003 First bonus: What produces storm-time “killer” MeV electrons? Affect satellites and humans in space Source: – Radially inward diffusion? – Wave acceleration at radiation belt? THEMIS: –Tracks radial motion of electrons Measures source and diffusion Frequent crossings –Measures E, B waves locally ANIK telecommunication satellites lost for days to weeks during space storm

7. THEMIS SRR 7 UCB/SSL, July 8-9,2003 Second bonus: What controls efficiency of solar wind – magnetosphere coupling? Important for solar wind energy transfer in Geospace Need to determine how: – Localized pristine solar wind features… – …interact with magnetosphere THEMIS: – Alignments track evolution of solar wind – Inner probes determine entry type/size

8. THEMIS SRR 8 UCB/SSL, July 8-9,2003 Mission Science Objectives in a Nutshell Minimum mission CSR, Table E-1

9. THEMIS SRR 9 UCB/SSL, July 8-9,2003 Ground Rules Mission LevelScienceAdherence to requirement Minimum missionPrimaryPerformance floor PrimaryDesign driver Ancillary (HF modes)Design goal BaselinemissionSecondary (Rad Belt)Design goal Tertiary(Dayside)Design goal Extended mission3 rd yearbaseline orbitsAt negligible impact if on target Phase F mission4 th, 5 th year shock/pauseAt negligible impact if on target Explicitly included In Level1 Req’s