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Substorm Parameters: A Progress Report

Substorm Parameters: A Progress Report. Christine Gabrielse cgabrielse@ucla.edu Sergey Apatenkov, Nathaniel Frissell, Stefan Kiehas, Jiang Liu, Kyle Murphy, Jonathan Rae, Geoff Reeves, Andrei Runov, Victor Sergeev, Emma Spanswick, Taku Takada Thursday, June 25, 2009 GEM.

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Substorm Parameters: A Progress Report

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  1. Substorm Parameters: A Progress Report Christine Gabrielse cgabrielse@ucla.edu Sergey Apatenkov, Nathaniel Frissell, Stefan Kiehas, Jiang Liu, Kyle Murphy, Jonathan Rae, Geoff Reeves, Andrei Runov, Victor Sergeev, Emma Spanswick, Taku Takada Thursday, June 25, 2009 GEM 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 ~40 events • Events: only looked at substorms during major & minor THEMIS conjunctions • Today • Progress Report • Explain criteria

  4. T0: Auroral Intensification • Criteria: When at least one bin sees a sudden, sharp increase in intensity Mean Brightness (Counts) over time

  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. Bz Variation Onset Selection Examples No disturbance 3 min prior Bz disturbance lasts 3 minutes THA: start of variation that goes above background THD: 20 % criteria

  7. 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

  8. (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

  9. 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

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

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

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

  13. Substorm Parameters: A Progress Report Christine Gabrielse cgabrielse@ucla.edu Sergey Apatenkov, Nathaniel Frissell, Stefan Kiehas, Jiang Liu, Kyle Murphy, Jonathan Rae, Taku Takada, Andrei Runov, Victor Sergeev, Emma Spanswick Thursday, June 25, 2009 GEM www.igpp.ucla.edu/themis/events

  14. 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

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