[GEM] THE GEM MESSENGER, Volume 25, Number 37

Newsletter Editor editor at igpp.ucla.edu
Wed Sep 9 09:40:30 PDT 2015


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     THE GEM MESSENGER
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Volume 25, Number 37
September 9, 2015

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2015 Summer Workshop Report: Tail-Inner Magnetosphere Interactions Focus Group
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From: Frank Toffoletto (toffo at rice.edu), Vassilis Angelopoulos, John Lyon, and Stan Sazykin

The TIMI focus group had 4 breakout sessions during the 2015 workshop.  2 sessions were joint with other focus groups. The first session was joint with the Magnetic Reconnection in the Magnetosphere focus group was held on Tuesday June 16. The report for this session was kindly provided by the reconnection focus group and can be found in their report. The second session was also joint with the Storm-Time Inner Magnetosphere-Ionosphere Convection (SMIC) focus group was held on the morning of Thursday, June 18. 

Joint SMIC/TIMI session – Thursday, June 18

Co-Chairs: Stan Sazykin (Rice), Joe Baker (Virginia Tech) and Frank Toffoletto (Rice).

Mike Wiltberger (NCAR/HAO) presented published (in press, JGR) analysis of bubbles (BBFs) in LFM simulations. He traces these flow channels back to originating reconnection spots in the tail and also did statistics using simulations to compare with Geotail data published by Shin Ohtani and found quite good agreement.

Mike Henderson (LANL) made a presentation on PBIs and the evolution of north-south aligned forms-auroral streamers and showed that omega bands were related to flow bursts. Sometimes injections at geosynchronous and can be related to streamers but this is uncommon.

George Khazanov (GSFC) presented a new self-consistent model of auroral precipitation that emphasizes the importance of superthermal electrons and interhemispheric flows. 

Natalia Ganushkina (U. Michigan) presented a new empirical model for plasma sheet electron fluxes using THEMIS data between 6 and 10 Re. Motivation is to specify outer boundary conditions for magnetospheric electrons. Data includes ESA (up to 30 keV) and SST (50 keV—a few MeV) instruments as well as electron temperature as a function of L and solar wind velocity.

Sean Chen (GSFC) along with Mei-Ching Fok looked at the penetration of large electric fields into the inner magnetosphere using Van Allen Probes data between 9/18/2012 and 12/31/2014. He showed statistical patterns of Ey (dawn to dusk) in corotating frame for various Kp levels. Results seem similar to Rowland and Weygant 1998. Some simulations from the comprehensive inner magnetosphere ionosphere (CIMI) model were also presented.

Matina Gkioulidou (JHU/APL) show observations for 3/17/2013 event when she finds multiple injections in the ring current from using Van Allen Probe ring current ion data. Lower energy particles (pressure) are correlated with Dst, but higher-energy particles are not. Pitch-angle distributions were found to be mostly isotropic.

Shin Ohtani (JHU/APL) discussed adiabatic transport in the plasma sheet and reported that the Harang discontinuity is the solution to the pressure balance problem.

X. Shu (Virginia Tech) showed SuperDarn observations of Pi2 pulsations in the SAPS region. He suggested that this is a response to a BBF, showing THEMIS flow data to support this.

Bing Yang (U. Calgary) showed GRL (in press) results using auroral patches to estimate convection flows. 

Doug Cramer (UNH) Doug showed OpenGGCM-RCM simulations of 3/17/2013 and 11/01/2012 events, both appear to show a SAPS channel and electric field penetration in the inner magnetosphere.

Jian Yang (Rice) Showed RCM-E idealized simulations indicating that bubbles are important for ring current injection.

TIMI Focus group, Thursday June 18.

The final two TIMI Focus sessions were held on the afternoon of Thursday, June 18. Co-chairs: Vassilis Angelopoulos (UCLA), John Lyon (Dartmouth) and Frank Toffoletto (Rice)

Doug Cramer (UNH) Found that using the OpenGGCM-RCM coupled model, they have identified SAPS events in the March 17, 2013 and November 1, 2012 geomagnetic storms. During these events, the peak of the poleward electric filed was found to be near a magnetic local time of 17. 

Jian Yang (Rice) Using RCM-E simulations, he showed that bubbles can contribute about 60% of the ring current energy for intense storms. He also showed an RCM-E simulation without bubble injections through the tailward boundary, which produced roughly the same large-scale ring current pressure distribution as the run with bubbles.

Drew Turner (Aerospace): Presented results from his recently published GRL article (2015) of Van Allen Probes observations of energetic electron injections deep into the inner magnetosphere.  Their evidence apparently link sudden injections of 10s to 100s electrons into the slot region and inner radiation belt to classic substorm injections and activity at higher L-shells, though the injection mechanism at such low L remains an open question.

Sasha Ukhorskiy (JHU/APL) Reported on recent analysis of ion measurements from the RBSPICE experiment of the Van Allen Probes mission showed that the buildup of plasma pressure in the inner magnetosphere largely occurs in the form of localized discrete injections similar to dipolarization fronts observed in the magnetotail. His analysis is based on three-dimensional test-particle simulation in an analytical model of the electric and magnetic field perturbations associated with the injection fronts showed that the proton acceleration is produced by stable particle trapping and subsequent earthward propagation along with the front.

Chih-Ping Wang (UCLA) He examined how far BBFs can transport high-energy electrons (~100 keV) earthward using simultaneous measurements from 3 THEMIS probes and one RBSP probe aligned along similar Y from X ~ –12 to –5 Re. BBFs preconditioned by stronger large-scale convection, thus larger ring current and lower magnetic field strength in the inner magnetosphere, can transport high-energy electrons (~100 keV) further earthward.

Christine Gabrielse (UCLA) Presented results from analytical modeling of electron injections via localized, transient dipolarizing flux bundles demonstrated that the source of electrons depends on the spacecraft location relative to the DFB front as well as the DFB properties. In many scenarios, the electron source is the plasma sheet; however, if the field magnitudes are large and the spacecraft crosses the dawnside of the front, electrons may arrive from the reconnection region due to enhanced earthward transport via sharp, localized gradients in the DFB's magnetic field.

Larry Lyons (UCLA). Showed that localized channels of enhanced polar cap flow are traceable in red line via polar cap arcs and patches. Tracing indicates that the flow channels not only drive plasma sheet/auroral oval flow channels, PBIs, streamers, and substorm onset, but they also feed the westward surge and poleward expansion of the substorm bulge. Features are traceable across the polar cap for up to ~1-1.5 hr.

Yin Zhou (UCLA). Showed that based on ground-based observation, nightside auroral oval disturbances are found to be preceded by localized and fast flows in the polar cap traced by polar cap arcs. These disturbances are major disturbances within a few hours and they only initiate after the impingement of polar cap arcs on the auroral poleward boundary and right at the impinging longitude, suggesting them to be triggered by meso-scale flows from polar cap.

Toshi Nishimura (UCLA) presented MHD simulation results of driven reconnection by localized flow channels impinging on the plasma sheet. He suggested that magnetotail reconnection can be triggered by fast flow channels originating in the dayside.

Jodie Barker Ream (UCLA) show that using both the UCLA and LFM global MHD models, they find that as flows slow down in the braking region a Pi2 period compressional wave begins to run ahead of the flows into the inner magnetosphere. However, the ionospheric conductance models play a large part in determining how far earthward those compressional waves are able to travel.

Aaron Schutza (Rice) gave a presentation describing his thin filament simulations of interchange oscillations in the Earth’s magnetotail. His simulations show evidence of mode coupling between tail flapping and interchange oscillations.

Roxanne Katus (Univ. Michigan) presented initial result of a 10 minute resolution magnetospheric ion temperatures derived from TWINS MENA flux data. The ion temperature data were examined statistically as a function of storm time.

Zhengwei Chen (UNH) performed a case study with in situ magnetic field and plasma measurements from the Cluster to examine the FAC carriers in the magnetotail during a substorm recovery phase. This study provides a method to study the FAC carriers in a feasible way by using Cluster multi-instrument (FGM, PEACE, CIS) data.

Jiang Lu (UCLA) showed results of a statistical study, where he found that dipolarizing flux bundles (DFBs) in the magnetotail carry asymmetric region-1-sense field-aligned currents (FACs). These asymmetric FACs allow ~10 DFBs to comprise the substorm current wedge (SCW), so that each DFB acts as a "wedgelet", the building element of the SCW.

Plans for the coming year

2016 will final year for the TIMI focus group. We hope to use the final year to recap the progress that has been made during the existence of the TIMI focus group and map out future plans that can be taken on by existing or future focus groups. This is a focus area that continues to attract a lot of interest and with the recent MMS mission along with the recently formed Heliophysics/Geospace System Observatory (HGSO) group we expect more exciting science to come.


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