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Introduction, THEMIS overview Overview of orbits First THEMIS tail results from 2008

THEMIS Observations from the First tail season. Introduction, THEMIS overview Overview of orbits First THEMIS tail results from 2008 Westward expansion Typical signatures at 20-30Re Local time effects Neutral sheet proximity History of tail activity Simultaneity of tail phenomena

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Introduction, THEMIS overview Overview of orbits First THEMIS tail results from 2008

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  1. THEMIS Observations from the First tail season • Introduction, THEMIS overview • Overview of orbits • First THEMIS tail results from 2008 • Westward expansion • Typical signatures at 20-30Re • Local time effects • Neutral sheet proximity • History of tail activity • Simultaneity of tail phenomena • The first few minutes • Rapid M-I coupling

  2. Maximizing Substorm Science on THEMIS:Probe Alignments and Ground Conjunctions Simulation: J. Raeder, UNH Visualization: Tom Bridgman,GSFC/SVS Vassilis Angelopoulos, UCLA ESS April 13, 2006

  3. P1 P2 P3 P4 P5 TH-B TH-C TH-D TH-E TH-A 2007-03-23 2007-06-03 Launch=2007-02-17 YGSE 2007-07-15 XGSE 2007-08-30 2007-12-04 First 10 months Angelopoulos, 2008 Space Sci. Rev. In Press http://themis.ssl.berkeley.edu/

  4. TH-B TH-C TH-D TH-E TH-A P1 P2 P3 P4 P5 First year baseline orbit YGSE Dayside 12008-08-08 XGSE Tail 12008-02-02 Angelopoulos, 2008 Space Sci. Rev. In Press

  5. First light: Nature’s welcome. Substorm captured on March 23, 2007 V ~ 350km/s Angelopoulos et al., First Results from THEMIS, SSR, 2008 Raeder et al., Open GGCM simulations for ..THEMIS…, SSR, 2008 Keiling et al., Correlation of substorm injections…, GRL, 2008 Keiling et al., Multiple intensifications inside the … bulge…, JGR, submitted 2008 Speed: 1MLT/min

  6. Conclusions on March 23, 2007 event • Westward expansion speed on the ground ~ 1 MLT hrs/minMaps to 10RE as 200-300km/s westward • Westward observed speed in space (D - E) is ~250km/sConsistent with mapping the speed from the ground up • Summary: First Observations of Westward Traveling Surge in Space • Similar papers establish the nature of substorm expansion in space: • Zhang, H. et al., JGR, 2008 [February 28, 2007 substorm; FGM only] • Donovan, H., et al., GRL, 2008 [March 13, 2007 substorm; TH-A ESA] In 2009-2012 THEMIS probes will again be at 1000-3000km in the plasma sheetWill map over Siberia/Alaska and Greenland/Iceland/ScandinaviaExpect to do microphysics of current disruption and study field aligned current generation

  7. 2008 tail season Midnight Pre-midnight Feb-26 Mar-01 Feb-22 Feb-18 Feb-14 Feb-10 Feb-6 Jan-29 Feb-2 Feb-26 Jan-29

  8. Jan 29, 2008 substorms07:14 UT onset/precursor? 07:38 UT onset 08:31 UT intensification AU, AL 2008 January 29 100 0 P3(D) P2(C) P1(B) 0831 X GSM P4(E) -100 P5(A) –30 R 10 R E E -200 0714 0738 07:00 07:30 08:00 08:30 09:00 10 R E Y GSM

  9. Jan 29, 2008 substorm AU, AL 2008 January 29 100 0 P3(D) P2(C) P1(B) 0831 X GSM P4(E) -100 P5(A) –30 R 10 R E E -200 0714 0738 07:00 07:30 08:00 08:30 09:00 10 R E Y GSM P5(A) Too far West for all onsets (1-2RE)

  10. Jan 29, 2008 substorm AU, AL 2008 January 29 100 0 P3(D) P2(C) P1(B) 0831 X GSM P4(E) -100 P5(A) –30 R 10 R E E -200 0714 0738 07:00 07:30 08:00 08:30 09:00 10 R E Y GSM P4(E) Near 1st onset East of 2nd and 3rd onsets (1RE)

  11. Jan 29, 2008 substorm AU, AL 2008 January 29 100 0 P3(D) P2(C) P1(B) 0831 X GSM P4(E) -100 P5(A) –30 R 10 R E E -200 0714 0738 07:00 07:30 08:00 08:30 09:00 10 R E Y GSM P3(D) Right-on for 1st onset East of 2nd and 3rd onsets (1RE) Each onset preconditions (relaxes) tail

  12. Jan 29, 2008 substorm AU, AL 2008 January 29 100 0 P3(D) P2(C) P1(B) 0831 X GSM P4(E) -100 P5(A) –30 R 10 R E E -200 0714 0738 07:00 07:30 08:00 08:30 09:00 10 R E Y GSM P2(C) At right MLT but at outer plasma sheet South turning during 1st onset (Rx?) Within ~1min from onset South-then-North turning during 2nd Only Northward turning during 3rd Dipolarization/CD moves tailward

  13. Jan 29, 2008 substorm AU, AL 2008 January 29 100 0 P3(D) P2(C) P1(B) 0831 X GSM P4(E) -100 P5(A) –30 R 10 R E E -200 0714 0738 07:00 07:30 08:00 08:30 09:00 10 R E Y GSM P1(B) At right MLT but at PSBL/Lobe South turning during 1st onset (Rx?) Within ~1min from onset South-then-North turning during 2nd Only Northward turning during 3rd onset Expansion/Dipolarization/CD moves tailward

  14. Event summary: Jan 29 • January 29, 7-8 UT substorms (P1,2 Zns~3-5RE) • Localization in Y demands good space-ground mapping • Within 1RE or better in space, within <5o in the ionosphere • Substorms are sequences of activations: • Precursor, main onset, intensification • Each activation preconditions the tail sector within which it occurred • At 10-12RE, all activations at onset meridian have Northward field/Earthward flows • At 15-20RE, initial activations accompanied by Southward – then Northward field • Subsequent activations accompanied by Northward field/Earthward flows • At 20-30RE, initial activations accompanied by Southward, or bipolar field • No flows or beams if away from the neutral sheet even if at the plasma sheet boundary • If at the right meridian, P1, P2 show clear signatures within ~1min of onset • Weak signatures of fast flows, no intense beams away from the neutral sheet • If anything is happening to the plasma it is probably happening closer to the neutral sheet

  15. Mar 1, 2008 substorms01:48:52 UT precursor? 01:54:30 UT onset 01:48:52UT 01:54:30UT

  16. Signatures seen at TH-C (P2) first… … then at TH-B (P1) Bipolar Bz (+/-) Tailward flows 1st event: FAC (dBy) at P3, P4 At large distance from a thin CS Field aligned current below 2nd event: Expansion Accompanied by FAC No sharp dipolarization

  17. Event summary: Mar 1 • Mar 01, 01:48:52UT, 01:54:30UT onsets (See: Runov, A. et al JGR) • P1, P2 at 0. 5RE from nominal neutral sheet • At 17-23RE, onsets accompanied by tailward flows, southward fields • Flows started inside of TH-C (P2, < 17RE) first, then moved to TH-B (P1, at 23RE) • Tailward beams seen at TH-C ahead of flows • Flows (and energetic particles at TH-C (P2) – not shown) within 1 min from onset • P3, P4 at 1RE from nominal neutral sheet • Far from an extremely thin neutral sheet • Observe FAC below satellite during 1st event • Observe FAC during plasma sheet recovery during 2nd event

  18. THEMIS Summary • Substorms have lived up to their notoriety: tough to crack • Start from localized (1RE scale), expand azimuthally and tailward • Start deep inside a thin plasma sheet near an extremely thin current sheet • Azimuthal expansion of WTS can be tracked in space shown to match ground • Must select events when probes are both in right Y and Z location • THEMIS observed classical substorm signatures at all altitudes, but: • Signatures are seen near-simultaneously at multiple altitudes • When at right meridian, all probes respond to ~1 min of ground onset • Response varies with substorm history: • Earliest onset (pseudobreakup, precursor, small substorm or onset) has: • At 20-30RE: • Southward Bz consistent with tailward moving plasmoid when Zns > 2-3RE • Tailward beams or flows when Zns < 1RE from nominal neutral sheet • At 10-20RE: Northward Bz consistent with Earthward moving flux rope • Field aligned current signatures when Zns > 2-3RE • Fast Earthward flows when Zns < 2RE • Follow-on onsets (2nd, 3rd) have: • Earthward flows seen further down the tail near (~1min) of onset • Dipolarization and plasma sheet expansion accompany them • The 1min scale response is shorter than typical Alfvén transit times • Only electrons can provide fast coupling • May be excited by a kinetic Aflvénic pulse but run ahead of waves

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