Substorm Parameters: A Progress Report

1. Substorm Parameters: A Progress Report Christine Gabrielse cgabrielse@ucla.edu Sergey Apatenkov, Nathaniel Frissell, Stefan Kiehas, Jiang Liu, Kyle Murphy, Toshi Nishimura, Jonathan Rae, Geoff Reeves, Andrei Runov, Victor Sergeev, Emma Spanswick, Taku Takada Wednesday, September 16, 2009 THEMIS SWT Meeting, Annapolis www.igpp.ucla.edu/themis/events

2. Introduction • March THEMIS SWT meeting discussion • Much diversity between authors on the definition of terms • Substorm parameter table • General characterization of event/onset and of the geometry of conjunction • Characterization of auroral breakup • Characterization of potential signature of reconnection onset • Characterization of current disruption • Onset times (ie Bz variation, auroral intensification, Ey variation, |Vx| increase) • Values (ie Peak amplitude of Vx flow, s/c footpoint locations, s/c distance from neutralsheet, type of Bz variation, beta, flux transport, LANL injection data)

3. Introduction • March THEMIS SWT meeting discussion • T0: Want consistency among substorm community • T0 = Auroral intensification. Historical, everyone can agree • Epoch timing analysis • Committee formed • Young researchers having experience with timing • Define onset criteria: Consistent, objective “formula” • Now, ~80 parameters and ~124 events (2008 added since GEM) • Events: only looked at “substorms” during major & minor THEMIS conjunctions • Event added to table due to AE rise • Today • Progress Report • Explain criteria

4. T0: Auroral Intensification • 2009 Criteria: When at least one bin sees a sudden, sharp increase in intensity 2008 Criteria: Integrated over entire imager Mean Brightness (Counts) over time Integrated Intensity (Akin to & collaborating with Nishimura) Earlier Question: 90/250 Nishimura events during THM conjunction 19/86 of our 2007-08 chosen events

5. AE Pi2s • AE Onset Selection • If return to quiet, marked 2nd AE Onset • Note 1st onset matches in-situ observed onsets • In-situ Onset example Pi2s Bx Bz Ey (-vxB) Vx Flux Transport (Int Ey) Ey: efs Ey: -vxB Flux Transport Vx Pt & Pb

6. AE Index • Automated • Initial rise time • Max AE w/in 5 min • Max AE of that rise • Secondary rise time • Secondary max AE values

7. Bz Variation Onset Selection • Requirements: • No disturbance 3 min prior • Bz disturbance lasts 3 minutes • Onset selection: • Sharp change in Bz: dBz/dt • Onset of Bz that grows 20% past the previous 3 minutes & lasts 3 minutes • Onset where growth starts, not point where passes the background

8. Bz Variation Onset Selection Examples Objectivity is difficult; Analysis of P3 alters perception of P4 Sharp vs. gentle slope 20% criteria

9. Bxyz[nT] GSM Ts-3min to Ts+3min Vxyz[km/s] GSM (mom) Peak velocity Vx (total) Vpxyz[km/s] GSM Vxyz[km/s] GSM (reduced) Peak velocity Vx (perp) • C7ab/D7ab parameters • Peak amplitude of outflow Vx (perp/total) w/in 3 min of Ey increase (km/s) • Dataset • Bxyz in GSM: FGL data • Vxyz in GSM: ESA mom/ reduced data (TBD for ESA&SST) • Vpxyz: estimated from Bxyz{3s} & Vxyz

10. (a) Timings are different, but polarity is the same Bxyz[nT] GSM Vxyz[km/s] GSM (mom) Vpxyz[km/s] GSM Vxyz[km/s] GSM (reduced) • Problem: • Peak times are sometimes different for perp and total velocity (b) Timings are different, and polarity are opposite

11. Substorm current wedge parameters using midlatitude magnetometers. Observations:midlatitude observatories 20-55° CGLata) <55° to avoid influence of complicated auroral currentsb) >20° to avoid SQ variation influenceInput data: INTERMAGNET + THEMIS GBO best coverage at 04-09 UT In 2009 tail season SCW parameters can be determined for about 50% substorms during major / minor conjunctions Using THEMIS footpoints can determine if s/c are within the SCW

12. T0 = Auroral Intensification Ygsm limit: -7 to 7 Re AE AE Bz Bz Vx Vx Flux Flux Ey Ey AE AE Bz Bz Vx Vx Ey Ey

13. S/C Location & Distance from NS found using GSFC 4D Viewer Tipsod (Tsyganenko Model) P1 Preliminary Observations P2 P3 P4 P5

14. P5 P4 P3 P2 P1

15. www.igpp.ucla.edu/themis/events

16. Substorm Parameters: A Progress Report Christine Gabrielse cgabrielse@ucla.edu Sergey Apatenkov, Nathaniel Frissell, Stefan Kiehas, Jiang Liu, Kyle Murphy, Toshi Nishimura, Jonathan Rae, Geoff Reeves, Andrei Runov, Victor Sergeev, Emma Spanswick, Taku Takada Wednesday, September 16, 2009 THEMIS SWT Meeting, Annapolis www.igpp.ucla.edu/themis/events

17. T0 = 1st AE Onset Ygsm limit: -5 to 5 Re Bz Vx Flux Ey Bz Vx Flux Ey

19. Bz Variation Onset • Criteria • The time when Bz significantly changes with respect to the variations within the previous 3 minutes and this change leads to significant disturbances for the next 3 minutes • If there is a “sharp increase", i.e., dBz/dt, this is called the onset. • If not, onset is a change in DBz/B by at least 20% of the previous 3 minutes for more than 3 of the following minutes • 20% was used as the minimum for a first run through, but may be increased after more analysis • Onset defined when the Bz disturbance starts and not when it goes beyond/under the background, i.e., when the disturbance reaches a specific value