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

Storms cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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

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 cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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] cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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 cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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

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] cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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

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

Substorm Phases cgabrielse@ucla.edu GEM Student Day, 2013 June 16

Gem Focus Groups Substorm Expansion Onset: The First 10 Minutes: Tuesday, 10:30 - 12:15, 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, 10:30 - 12:15, Cathedral Peak cgabrielse@ucla.edu GEM Student Day, 2013 June 16

References Slide 1 Aurora Image: http://thewatchers.adorraeli.com/2012/03/18/aurora-sub-storm-march-1516-2012-timelapse-and-gallery/ Kyoto AE/AL Indices: http://wdc.kugi.kyoto-u.ac.jp/ae_provisional/200802/index.html 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: http://asterisk.apod.com/viewtopic.php?f=29&t=23109 By Kwon, O. Chul. Taken by fish-eye lens at Yellowknife, Canada. 2011-02-23. Slide 4 Ground Magnetometer Map: http://supermag.uib.no/ SuperMAG cgabrielse@ucla.edu GEM Student Day, 2013 June 16

References Omega Band image: http://ham.space.umn.edu/spacephys/aurora_gallery/aurora_answers.html 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: http://www.sos.noaa.gov/Datasets/dataset.php?id=380 NOAA cgabrielse@ucla.edu GEM Student Day, 2013 June 16

Substorms Extra cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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

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). cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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 cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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. cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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. cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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. cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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 cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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] cgabrielse@ucla.edu GEM Student Day, 2013 June 16

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)