Substorm Parameters: A Progress Report Christine Gabrielse 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

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)

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

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

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

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

 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 Peak velocity Vx (total) Peak velocity Vx (perp) Ts-3min to Ts+3min B xyz [nT] GSM V xyz [km/s] GSM (mom) Vp xyz [km/s] GSM V xyz [km/s] GSM (reduced)

 Problem: –Peak times are sometimes different for perp and total velocity (a) Timings are different, but polarity is the same (b) Timings are different, and polarity are opposite B xyz [nT] GSM V xyz [km/s] GSM (mom) Vp xyz [km/s] GSM Vxyz [km/s] GSM (reduced)

Observations: midlatitude observatories 20-55° CGLat a) 20° to avoid SQ variation influence Input data: INTERMAGNET + THEMIS GBO best coverage at UT Substorm current wedge parameters using midlatitude magnetometers. In 2009 tail season SCW parameters can be determined for about 50% substorms during major / minor conjunctions

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

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

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

Substorm Parameters: A Progress Report Christine Gabrielse 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

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