Substorm Parameters: A Progress Report Christine Gabrielse 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

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 ~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

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

 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)

AE Index  Automated  Initial rise time –Max AE w/in 5 min –Max AE of that rise  Secondary rise time –Secondary max AE values

 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 Bz Variation Onset Selection

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

 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 Using THEMIS footpoints can determine if s/c are within the SCW

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 Vx Ey

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

P1 P2 P3 P4 P5

Substorm Parameters: A Progress Report Christine Gabrielse 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

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

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