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Substorm Parameters: A Progress Report. Christine Gabrielse [email protected] 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. - PowerPoint PPT Presentation
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Substorm Parameters: A Progress Report
Christine [email protected]
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, 2009GEM
www.igpp.ucla.edu/themis/events
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 2nd
AE Onset
– Note 1st onset matches in-
situ observed onsets In-situ Onset example
Flux Transport
Pi2s
Pi2s
AE
Bx
Bz
Vx
Ey: efs
Ey: -vxB
Pt & PbVx
Flux Transport(Int Ey)
Ey(-vxB)
Bz Variation Onset Selection Examples
THD: 20 % criteriaTHA: start of variation that goes above background
No disturbance 3 min priorBz 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 velocityVx (total)
Peak velocityVx (perp)
Ts-3min to Ts+3min
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(a) Timings are different, but polarity is the same
(b) Timings are different, and polarity are opposite
Bxyz [nT]GSM
Vxyz [km/s]GSM (mom)
Vpxyz [km/s]GSM
Vxyz [km/s]GSM (reduced)
Observations: midlatitude observatories 20-55° CGLata) <55° to avoid influence of complicated auroral currents
b) >20° to avoid SQ variation influence
Input data: INTERMAGNET + THEMIS GBO best coverage at 04-09 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
P2P3P4P5
Ygsm limit: -7 to 7 Re
AE
Bz
Vx
Flux
Ey
AE
Bz
Vx
Ey
AE
Bz
VxFlux
Ey
AE
T0 = Auroral Intensification
Bz
T0 = 1st AE Onset
Bz
Vx
Flux
Ey
Bz
Vx
Flux
Ey
Ygsm limit: -5 to 5 Re
Substorm Parameters: A Progress Report
Christine [email protected]
Sergey Apatenkov, Nathaniel Frissell, Stefan Kiehas, Jiang Liu, Kyle Murphy, Jonathan Rae, Taku Takada, Andrei Runov, Victor
Sergeev, Emma Spanswick
Thursday, June 25, 2009GEM
www.igpp.ucla.edu/themis/events
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