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THEMIS T IME H ISTORY OF E VENTS AND M ACROSCALE I NTERACTIONS DURING S UBSTORMS

THEMIS T IME H ISTORY OF E VENTS AND M ACROSCALE I NTERACTIONS DURING S UBSTORMS RESOLVING THE MYSTERY OF WHERE, WHEN AND HOW AURORAL ERUPTIONS START The THEMIS mission approach to addressing the substorm question Fall AGU, Dec 5, 2005.

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THEMIS T IME H ISTORY OF E VENTS AND M ACROSCALE I NTERACTIONS DURING S UBSTORMS

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  1. THEMIS TIME HISTORY OF EVENTS AND MACROSCALE INTERACTIONS DURING SUBSTORMS RESOLVING THE MYSTERY OF WHERE, WHEN AND HOW AURORAL ERUPTIONS START The THEMIS mission approach to addressing the substorm question Fall AGU, Dec 5, 2005

  2. TIME HISTORY OF EVENTS AND MACROSCALE INTERACTIONS DURING SUBSTORMS (THEMIS) • SCIENCE GOALS: • Primary: • “How do substorms operate?” • One of the oldest and most important questions in Geophysics • A turning point in our understanding of the dynamic magnetosphere • First bonus science: • “What accelerates storm-time ‘killer’ electrons?” • A significant contribution to space weather science • Second bonus science: • “What controls efficiency of solar wind – magnetosphere coupling?” • Provides global context of Solar Wind – Magnetosphere interaction • PROGRAMMATIC: • Selected in March 2002 for Phase A studies • Selected in April 2003 to proceed to Phase B: MIDEX#5 • Confirmed in May 2004 to full mission development • Critical design review, June 2004 • Launch no later than March 2007 on a D2925 • Current launch date: October 19, 2006 • 2YR mission; prime seasons: February 2007; February 2008. RESOLVING THE PHYSICS OF ONSET AND EVOLUTION OF SUBSTORMS Principal Investigator Vassilis Angelopoulos, UCB Project Manager Peter Harvey, UCB Industrial Partner SWALES Aerospace EPO Lead Nahide Craig, UCB

  3. THEMIS is an international program Science Team FGM ESA/IDPU SCM EFI/SPB ASI SST

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

  5. ? ? ? P1 P2 P3 P4 P5 Rarefaction wave Flows GBO Substorm phenomena THEMIS will address • Timing between current disruption,reconnection and ground onset withing 30s time resolution • Macroscale Interactions (causal relationship) • Capture outward motion (1600km/s) of rarefaction wave and inward motion of flows and boundary layer poynting flux • Ionospheric coupling • Cross-tail current reduction (P5u/P4) vs flows • Field aligned current generation by Rx flow vorticity, pressure gradients (dP/dz, dP/dx). • Cross-scale coupling to local modes • Field line resonances (10Re, 5min) • Ballooning modes, KH waves (1Re, 1min) • Weibel, CCI, kinetic Alfven waves (0.1Re, 6Hz)

  6. CD detection CD triangulation and onset determination as on AMPTE/CCE [Lui et al, 1988]. To Tail THEMIS CCE Spin axis To Earth To Sun Method exploits finite iongyroradius to remotely senseapproaching ion boundary and measure boundary speed (V⊥)

  7. Remote Sensing by Ion Sounding • Separation of 1 hr MLT on the ground corresponds roughly to ~ 2.6 Re at a geocentric distance of ~ 10 Re. • A ~1 hr MLT worst-case separation between ground onset and projected spacecraft location (mapping uncertainty) can be mitigated by using ~200 keV ion sounding. • Triangulation of the expansion velocity measured at two nearby locations assuming a nearby source (V=1.5Re/min = constant over ~2min => need ~3Re proximity).

  8. The 3D nature of the CD process Lopez & Lui [1990] • GOES 6 detected dB at ~08:30 UT, GOES 5 at ~08:33 UT, and CCE (R ~ 8.0 Re) at ~08:35 UT

  9. The 3D nature of the Rx process 0204UT JGR [Angelopoulos et al, 1995] Substorm Onset: ~0202UT Ygsm Xgsm 0215UT Ygsm

  10. Remote sensing of Rx onset • Based on techniques derived to determine location and onset time of plasmoid release from ISEE3 energetic particle data (X=-220Re) [Richardson and Cowley, JGR 1985] • Resolved paradox of earlier findings by Scholer et al 1984 that energetic particle acceleration was derived (assuming temporal interpretation) to be at distances inconsistent with plasmoid release. • Needed to invoke electric field pushing particles away from boundary • Needed to invoke spatial interpretation of dispersion

  11. …Remote sensing of Rx onset • Rx detection via time-of-flight ofenergetic particles. dt versus 1/V.Spatial or temporal? • Temporal is easy:LTEMPORAL = slope (dt versus 1/V) • Spatial: LACTUAL=LTEMPORAL*(VE/VB) • Assuming local E-field maps to reconnection E-field • VE=average convection speed, VB=boundary speed from finite gyroradius • VE ,VB not constant (measured) unless distance to Rx is small (~5-10RE) • Richardson and Cowley had VB but not VE • Computed V assuming L was consistent with Near-Earth source • Showed it is consistent with E-fields observed in Near-Earth tail • Determination of Rx location requires a-priori assurances of source proximity • Need to bracket Rx site with 2 spacecraft • This measured VE/VB will be average value from source to observation

  12. …Remote sensing: example from Geotail data • Determination of VB • To be done by THEMIS SST • Mounting very similar to GT ICS/EPIC • Determination of L • E.g., Sarris et al., JGG 1996

  13. Mission designer predictscompliance with requirements • Substorm recurrence = 3.75 hrs • Encounter probability = 1/5 • Residence needed = 19hrs/substorm • Over North America • Probes <±2RE of each other • In plasma sheet (inc<9o) • Limit shadows < 3hrs . Courtesy: R. Nemzek • THEMIS’s minimum requirement is to study >5 substorms with 4-probes • Need 94 hrs total; have >200hrs / year for 2 year mission • THEMIS’s baseline requirement is to study > 10 substorms with 4-probes while using 5th probe in a variety of dX, dY, dZ configurations • Need 188 hrs / year; have >200hrs / year

  14. …. regardless of launch day 4-probes Tail Season #1 5-probes

  15. Conjunctions and their quality look good (pre-midnight ones are best)……. Tail Season #1 Tail Season #2

  16. Story may be more complex: Energy dissipation via Alfvén waves? [e.g., Nakamura et al., 2005] THEMIS’s 3D electric field measurementsmay be able to answer this question as well

  17. First bonus: What producesstorm-time “killer” MeV electrons? Affect satellites and humans in space ANIK telecommunicationsatellites lost for days to weeksduring space storm • 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 • Prelude to RBSP? • SST can do crude O+ detection, with proper calibration

  18. Second bonus: What controls efficiencyof 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

  19. 0800 Wednesday Morning 1 SM31A-0398 MCC Level 1 THEMIS Orbit Design and Its Science Potential; *S Frey, et al. POSTER [Abstract] …additional potential for dawn/dusksector conjunctions over 2-5RE scales See Sabine Frey poster Wednesday Morning

  20. … as well as potential conjunctions w/ Cluster • THEMIS will launch in 2006 with 1st tail season in February 2007. • Potential for Cluster correlative studies: 2007-Jan-28 2007-Feb-28 2007-Mar-23 THEMIS can benefit from Cluster’s Solar Wind and ionospheric monitoring; Cluster can benefit from THEMIS’s upstream, sheath and m-pause monitoring.

  21. EFIs EFIa SCM ESA BGS SST Operations UCB FGM Tspin=3s Instrument I&T UCB Ground Mission overview: Constellationand instrument redundancy D2925-10 @ CCAS Release Encapsulation & launch Mission I&T UCB Probe instruments: ESA: Thermal plasmaSST: Super-thermal plasmaFGM: Low frequency magnetic fieldSCM: High frequency magnetic field EFI: Electric field

  22. 0800 THEMIS Ground Based Observatories *B Jackel, E Donovan, M Greffen, V Angelopoulos, S Mende, S Harris, W Rachelson, C Russell, D Pierce, D Dearborne POSTER [Abstract] Tuesday Morning 1 SM21A-0362 MCC Level 1 Ground observatory progress • 10/20 UCB&UCLA built GBOs deployed, providing data & experience • All (10) UCLA-provided EPO stations deployed in the US

  23. Probe flight hardware progress • First bus pre-integrated at Swales Aerospace, delivered to UCB, 11/30. • F1-3 instrument suites assembled, suite TV tested, delivered to MI&T • F4-5 instrument suites assembled, in TV testing, expect delivery 12/16 • Known issues: electron ESA m-channel plates a bit noisier than FAST • - Have time/replacement plates to address as MI&T is progressing

  24. Probe Carrier progress nominal

  25. Achievements and Potential • All instruments meet requirements and have been delivered • Spacecraft design meets requirements (mass, power and telemetry) • Spacecraft is magnetically and electrostatically clean • SST science bonus: • Low energy <30keV, good overlap w/ ESA (@ 40keV max) • SST may be able to discriminate 60-400keV O+ • In summary: THEMIS has state of the art, comprehensive instrumentation, that is fully capable of answering its science objectives and of becoming a very powerful observation platform when combined with other missions. • Looking forward to engaging the entire community in an exciting science program ahead of us!

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