1. Christine Gabrielse, UCLA
Substorms
GEM Student tutorial
Christine Gabrielse, UCLA
June 16, 2013

2. Storms
GEM Student Day, 2013 June 16

3. Substorms cgabrielse@ucla.edu GEM Student Day, 2013 June 16
Several times a day, ~1.5 hours long
GEM Student Day, 2013 June 16

4. Substorms …in the ionosphere …on the ground …in space
Onset: auroral brightening
Onset: sharp perturbation in magnetometer observations
Onset: reconnection,
dipolarization
…in the ionosphere
…on the ground
…in space
GEM Student Day, 2013 June 16

5. The “Auroral Substorm”
T=0. Quiet arcs drift equatorward.
T=0-5 min. Onset: Sudden brightening of equatorward arc in premidnight sector
T=5-10 min. Expansion Phase: Bright, dynamic auroral bulge forms
T=10-30 min. Westward-traveling surge Omega bands form to the east
T=30-60 min. Pulsating patches appear at eastern equatorward edge
T= 1-2 hours. Recovery phase: Pulsating patches continue as auroral activity dims and quiet arcs return
Omega bands
During the International Geophysical Year (1957), arrays of all-sky cameras were placed around the auroral oval to record what auroral activity occurred. It was found that the aurora tends to
repeat globally (namely, all along the auroral oval) a particular type of activity every several hours. This gave rise to a phenomenological model describing the development of what was called “the auroral substorm” (Akasofu, 1964).
[Akasofu, 1964]
GEM Student Day, 2013 June 16

6. The “Auroral Substorm”
T=0. Quiet arcs drift equatorward.
T=0-5 min. Onset: Incoming streamer sudden brightening near midnight
T=5-10 min. Expansion Phase
T=10-30 min. Westward-traveling surge
T=30-60 min. Pulsating patches appear
North
South
During the International Geophysical Year (1957), arrays of all-sky cameras were placed around the auroral oval to record what auroral activity occurred. It was found that the aurora tends to
repeat globally (namely, all along the auroral oval) a particular type of activity every several hours. This gave rise to a phenomenological model describing the development of what was called “the auroral substorm” (Akasofu, 1964).
Credit:
University of Alaska, Fairbanks
South
Credit:
Nishimura et al., 2012
THEMIS All-sky-imagers
North
GEM Student Day, 2013 June 16

7. Substorms in Space cgabrielse@ucla.edu GEM Student Day, 2013 June 16
.mov works
GEM Student Day, 2013 June 16

8. Substorms in Space cgabrielse@ucla.edu GEM Student Day, 2013 June 16
NENL=Near-Earth
Neutral Line (X-line)
Localized phenomenon
Bursty bulk flows (BBFs) only few RE wide
Plasmoid
Modified from
Hones [1977]
GEM Student Day, 2013 June 16

9. Substorms in Space X AE [nT] -8RE B [nT] V [km/s] Dipolarization Earth
Fast flow from reconnection
Red=strong flow AE
[nT]
Psuedobreakup
-8RE B
[nT] Vz V
[km/s]
Tail stretching
Dipolarization
Earth Y V Vy Vx
Bursty Bulk Flows (BBFs) E
mV/m
Depleted flux tube
8RE Ni
[1/cc] X
-8RE
-23RE
From Figure 5 in Birn et al. [2011] eV eV
NENL
Particle InjectionsChorusPulsating aurora

10. Substorm Current Wedge
Ground
Observations
Substorm Current Wedge
SCW caused by FAC from incoming DF: Liu et al., [2013] jgra.50092
Figure 2. IMAGE Magnetometer chain. Figure 2 (a)-(c) demonstrate the x-, z-, and y-component of the magnetic field observed by six stations in Norway during the time surrounding the 18:12 substorm. The black vertical line in (a) and (c) marks the onset of the previous substorm simultaneously observed at all stations, implying the signature is more global, and the substorm is located further away. The red vertical lines mark the onset of the event we study at each individual station. Evidenced from the delayed onset times, we find the current propagates poleward from BJO to just north of HOR. (b) demonstrates this fact as the z-negative bay implies a current system to the north while a z-positive bay implies the system is to the south. The red horizontal line marks zero. (d) illustrates the locations of the different stations (the six northernmost).
Modified from Reistad,
UNIS AGF-345

11. Substorm Phases
GEM Student Day, 2013 June 16

12. Gem Focus Groups Substorm Expansion Onset: The First 10 Minutes:
Tuesday, 10: :15, 1:30-5:00, Salon D
Relative timing between onset signatures in space & on the ground
The role of magnetotail reconnection (distant and near-Earth) in substorms and substorm-related processes
Substorm-related processes in the tail-dipole transition region
Substorm onset mapping (joint with the Magnetic Mapping and Techniques Focus Group)
Modes of Solar Wind-Magnetosphere Energy Transfer:
Thursday, 10:30-12:15; 1:30-3:00, Cathedral Peak
Tail-Inner Magnetosphere Interactions:
Monday, all sessions, Cathedral Peak
Tuesday, 10: :15, Cathedral Peak
GEM Student Day, 2013 June 16

13. References
Slide 1 Aurora Image:
Kyoto AE/AL Indices:
Acknowledgments: We thank AE stations (Abisko [SGU, Sweden], Dixon Island, Cape Chelyuskin, Tixie Bay, Pebek [AARI, Russia], Barrow, College [USGS, USA], Yellowknife, Fort Churchill, Sanikiluaq (Poste-de-la-Baleine) [GSC, Canada], Narsarsuaq [DTU Space, Denmark], and Leirvogur [U. Iceland, Iceland]) as well as the RapidMAG team (NiCT, JHU/APL, UoA, AARI, and IDG) for their cooperations and efforts to operate these stations and to supply data with us for the provisional AE index.
Slide 4 Aurora Image:
By Kwon, O. Chul. Taken by fish-eye lens at Yellowknife, Canada
Slide 4 Ground Magnetometer Map:
SuperMAG
GEM Student Day, 2013 June 16

14. References
Omega Band image:
Ektachrome photo by John R. Winckler, 14 July 1991, from University of Minnesota O'Brien Observatory, Marine-on-the-St. Croix, Minnesota.
Slide 10 Substorm Current Wedge image from R. McPherron UCLA ESS 154 course
Slide 10 verbal reference to Liu et al., 2013 JGR (on the topic of dipolarization fronts carrying in field-aligned currents, resulting in the substorm current wedge).
Slide 11 from R. McPherron UCLA ESS 154 course and
Extra Slide Auroral Oval Image:
NOAA
GEM Student Day, 2013 June 16

15. Substorms
Extra
GEM Student Day, 2013 June 16

16. Auroral Oval Auroral oval “maps” to plasma sheet cgabrielse@ucla.edu
GEM Student Day, 2013 June 16

17. The “Auroral Substorm”
Use a movie from the THEMIS asi of a substorm
T=0. Quiet arcs drift equatorward.
T=0-5 min. Onset: Sudden brightening of equatorward arc in premidnight sector, expanding westward and poleward.
T=5-10 min. Expansion Phase: Bright, dynamic bulge of auroral disturbance forms near onset
T=10-30 min. Westward-traveling surge: Auroral bulge develops sharp kink at westward edge which propagates westward. Omega bands form to the east.
T=30-60 min. Pulsating patches of aurora appear at the equatorward edge in the east. Auroral activity dims.
T= 1-2 hours. Recovery phase: Pulsating patches continue as auroral activity dims and quiet arcs return.
During the International Geophysical Year (1957), arrays of all-sky cameras were placed around the auroral oval to record what auroral activity occurred. It was found that the aurora tends to
repeat globally (namely, all along the auroral oval) a particular type of activity every several hours. This gave rise to a phenomenological model describing the development of what was called “the auroral substorm” (Akasofu, 1964).
GEM Student Day, 2013 June 16

18. The “Auroral Substorm”
T=0. Quiet arcs drift equatorward.
T=0-5 min. Onset: Incoming streamer leads to sudden brightening of equatorward arc in premidnight sector
T=5-10 min. Expansion Phase: Bright, dynamic auroral bulge forms
T=10-30 min. Westward-traveling surge
North
During the International Geophysical Year (1957), arrays of all-sky cameras were placed around the auroral oval to record what auroral activity occurred. It was found that the aurora tends to
repeat globally (namely, all along the auroral oval) a particular type of activity every several hours. This gave rise to a phenomenological model describing the development of what was called “the auroral substorm” (Akasofu, 1964).
South
Credit:
Nishimura et al., 2012
THEMIS All-sky-imagers
GEM Student Day, 2013 June 16

19. The “Auroral Substorm”
T=0. Quiet arcs drift equatorward.
T=0-5 min. Onset: Sudden brightening of equatorward arc in premidnight sector
T=5-10 min. Expansion Phase: Bright, dynamic auroral bulge forms
T=10-30 min. Westward-traveling surge: Auroral bulge develops sharp kink, propagates westward. Omega bands form to the east.
T=30-60 min. Pulsating patches of aurora appear at eastern equatorward edge
T= 1-2 hours. Recovery phase: Pulsating patches continue as auroral activity dims and quiet arcs return.
South
During the International Geophysical Year (1957), arrays of all-sky cameras were placed around the auroral oval to record what auroral activity occurred. It was found that the aurora tends to
repeat globally (namely, all along the auroral oval) a particular type of activity every several hours. This gave rise to a phenomenological model describing the development of what was called “the auroral substorm” (Akasofu, 1964).
North
Credit:
University of Alaska, Fairbanks.
GEM Student Day, 2013 June 16

20. The “Auroral Substorm”
T=0. Quiet arcs drift equatorward.
T=0-5 min. Onset: Sudden brightening of equatorward arc in premidnight sector
T=5-10 min. Expansion Phase: Bright, dynamic auroral bulge forms
T=10-30 min. Westward-traveling surge Omega bands form to the east
T=30-60 min. Pulsating patches appear at eastern equatorward edge
T= 1-2 hours. Recovery phase: Pulsating patches continue as auroral activity dims and quiet arcs return
South
During the International Geophysical Year (1957), arrays of all-sky cameras were placed around the auroral oval to record what auroral activity occurred. It was found that the aurora tends to
repeat globally (namely, all along the auroral oval) a particular type of activity every several hours. This gave rise to a phenomenological model describing the development of what was called “the auroral substorm” (Akasofu, 1964).
North
Credit:
University of Alaska, Fairbanks.
GEM Student Day, 2013 June 16

21. The “Auroral Substorm”
T=0. Quiet arcs drift equatorward.
T=0-5 min. Onset: Sudden brightening of equatorward arc in premidnight sector
T=5-10 min. Expansion Phase: Bright, dynamic auroral bulge forms
T=10-30 min. Westward-traveling surge Omega bands form to the east
T=30-60 min. Pulsating patches appear at eastern equatorward edge
T= 1-2 hours. Recovery phase: Pulsating patches continue as auroral activity dims and quiet arcs return
South
During the International Geophysical Year (1957), arrays of all-sky cameras were placed around the auroral oval to record what auroral activity occurred. It was found that the aurora tends to
repeat globally (namely, all along the auroral oval) a particular type of activity every several hours. This gave rise to a phenomenological model describing the development of what was called “the auroral substorm” (Akasofu, 1964).
North
Credit:
University of Alaska, Fairbanks.
GEM Student Day, 2013 June 16

22. Sun’s magnetic field lines
Sun’s magnetic field lines reconnect to Earth’s and pulls them back.
Plasma sheet: dense region of plasma where acceleration and transport takes place
Reconnection occurs
Earth’s magnetic field lines Me
From Øieroset et al, 2001
GEM Student Day, 2013 June 16

23. Substorms in Space cgabrielse@ucla.edu GEM Student Day, 2013 June 16
NENL
Modified from Shiokawa [1998]
NENL=Near-Earth Neutral Line (X-line)
A localized phenomenon
Bursty bulk flows (BBFs) only few RE wide
Plasmoid
Modified from Hones [1977]
GEM Student Day, 2013 June 16

24. Substorms in Space E B E X AE [nT] -8RE B [nT] V [km/s] Dipolarization
Fast flow from reconnection
Red=strong flow AE
[nT]
Psuedobreakup E
-8RE B
[nT] B Vz V
[km/s]
Tail stretching
Dipolarization Y Vy Vx E
mV/m
Depleted flux tube
8RE Ni
[1/cc] X E
-8RE
-23RE
From Figure 5 in Birn et al. [2011] eV eV
Particle InjectionsChorusPulsating aurora
Bursty Bulk Flows (BBFs)