Table of Contents ====================================================================== 1. 2014 WORKSHOP REPORT: The Magnetic Reconnection in the Magnetosphere Focus Group 2. Deadline for Early Bird Registration: October 23, 2014 IMC III workshop, March 23-27, UCLA ====================================================================== *************************** ** THE GEM MESSENGER ** *************************** Volume 24, Number 30 October 7, 2014 ---------------------------------------------------------------------- 1. 2014 WORKSHOP REPORT: The Magnetic Reconnection in the Magnetosphere Focus Group ---------------------------------------------------------------------- From: Co-Chairs Paul Cassak (WVU), Andrei Runov (UCLA), and Homa Karimabadi (UCSD) In year two for the focus group on Magnetic Reconnection in the Magnetosphere, four sessions were convened. Two were independent sessions with close to 100 people in attendance. Two joint sessions with other focus groups were also convened - one with the “Tail-Inner Magnetosphere Interactions” focus group and one with the “Magnetosheath” focus group. Each session had two “scene-setting” talks to provide an overview of the relevant topics, followed by discussion and shorter contributed presentations on both observations and theory/simulations to guide discussion. Summaries of each session follow, with a discussion of future plans. Session 1 - What controls the rate of dayside reconnection? - Monday, June 16, 10:30am-12:15pm The first set of scene-setting talks had researchers with opposing views on what controls the rate of dayside reconnection, which sparked interesting discussion. Joe Borovsky argued that the reconnection rate at the dayside magnetopause is controlled by the local plasma parameters on both sides (magnetosheath and magnetosphere) of the reconnection site. The solar-wind flow pattern around the magnetosphere largely controls those critical plasma parameters. Meanwhile, Ramon Lopez argued that the rate of magnetic merging on the dayside between the solar wind magnetic field and the geomagnetic field is identically the rate that flux is transported across the dayside merging line by the magnetosheath flow. This global transport is controlled by the net force acting on the flow in the magnetosheath (which is in turn dependent on the solar wind conditions as well as ionopsheric conductivity) and not by the local microphysics. For example, changes in plasma density at the magnetopause due to phenomena such as plasmaspheric plumes may reduce the local merging rate, however the flux being pushed into the merging line by the solar wind will simply pile up in adjoining sectors, increasing the merging rate in those sectors so that the integrated global merging rate does not change. Shan Wang used Cluster observations to show that the local reconnection rate of the dayside magnetopause generally follows the Cassak-Shay formula. For individual events, the contribution of O+ and cold ions from the magnetosphere can be comparable with that of the magnetosheath H+, but statistically the variation of the local reconnection rate is dominated by the variation of the magnetosheath/solar wind conditions. Alex Glocer presented a new, efficient algorithm for tracking magnetic separators in global magnetosphere simulations. The method does not require the presence of magnetic nulls and can handle very complex topologies (e.g., Flux Transfer Events). John Dorelli derived an expression for the subsolar magnetopause reconnection rate showing how Faraday’s law in the steady state limit weakens the dependence of the reconnection electric field on the state of the magnetosphere. The essential physics is that magnetic flux pileup in the sheath compensates for decreases in the Alfven speed just upstream of the diffusion region. Session 1 - General Contributions - Monday, June 16, 10:30am-12:15pm Michael Hesse showed PIC simulations of planar, asymmetric reconnection. He showed that the reconnection electric field is provided by electron inertia effects; yet, pressure tensor nongyrotropies are essential to obtaining a viable reconnection electric field distribution. Particle distributions are composed of meandering and rather simple, drifting populations. Jason Shuster showed electron distributions from the electron diffusion region (EDR) of a collisionless, symmetric, antiparallel particle-in- cell simulation of magnetic reconnection, which were discovered to exhibit intricate spatiotemporal evolution. Moving from the X-line to the end of the electron outflow jet, he reported that (1) the discrete, striated populations of X-line distributions retain their discrete structure as they coherently rotate through velocity space, and (2) the discrete striations fade in time as reconnection proceeds, predictions which are immediately relevant to the Magnetospheric Multi-Scale mission to observe and understand the electron-scale physics of magnetic reconnection. Colby Haggerty showed that electrons in anti-parallel reconnection are heated through a Fermi bounce mechanism at the point of sharpest magnetic curvature. This mechanism is enhanced by a parallel electric potential, which results in a mass independent scaling of the change in temperature which is proportional to the upstream Alfvén speed squared. Ruilong Guo analyzed Cluster data, finding two spiral magnetic null points connected by their common spine line, which has not been studied before. During the formation of the two-spiral-null- point structure, a secondary island was generated, which were flux ropes that magnetic field lines rotated around the spine line. Session 2 - How is magnetotail reconnection modulated by dayside reconnection? What is the nature of magnetotail reconnection onset and transients? - Monday, June 16, 1:30pm-3:30pm Toshi Nishimura showed simultaneous day and night observations by all- sky imagers; radars revealed that a dayside poleward-moving auroral form (PMAF, an ionospheric signature of dayside reconnection) evolved into a polar cap airglow patch that propagated across the polar cap and was then followed by nightside poleward boundary intensifications (PBIs, nightside reconnection). The propagation across the polar cap and the subsequent PBIs suggest that the flow channel originated from dayside reconnection and then reached the nightside open-closed boundary, triggering localized nightside reconnection and flow bursts within the plasma sheet. Ying Zou found localized polar cap flow enhancements are found to colocate and propagate with airglow patches, indicating that these meso-scale flows can be traced by airglow patches in an all sky imager. Using airglow patches as flow tracers, we found that as airglow patches propagate across the polar cap and approach the nightside auroral poleward boundary, they are followed by and connected to PBI/streamers. Vassilis Angelopoulos discussed plans for the THEMIS mission to be in the magnetotail when MMS is at the dayside, potentially giving an unprecedented opportunity to study both simultaneously. Session 2 - What determines the cross-tail scale of reconnection jets? - Monday, June 16, 1:30-3:30pm Phil Pritchett reviewed what is known from a theoretical perspective regarding the cross-tail extent of reconnection jets in the magnetotail. While many 3D models, including fully kinetic, hybrid, two-fluid, and MHD, are able to produce structure on the scale of 15 - 30 ion inertial lengths, there is little consensus regarding the physics that determines these scales. Clearly, additional work is needed to provide a more definitive understanding of the jet width. Jiang Liu showed observations showing that dipolarizing flux bundles expand in the cross tail direction as they propagate earthward. This expansion allows them to cause global effects. Yi-Hsin Liu showed that the ion-ion kink instability seems to be unavoidable in tail equilibria. He demonstrated that the imprint of pre-existing kink structure under slow driving can produce a patchy onset of reconnection and hence patchy outflows, which may explain the cross- tail size of BBFs. Session 3 - Joint with "Tail-Inner Magnetosphere Interactions" Focus Group - Monday, June 16, 3:30-5:00pm Misha Sitnov showed results from 3D PIC simulations with open boundaries showing that spontaneous reconnection, including the formation of new large-scale X-lines in the dawn-dusk direction, is possible in the magnetotail. However, it is manifested primarily by the formation and acceleration of dipolarization fronts rather than by the X-line formation. Buoyancy and flapping motions significantly disturb the dipolarization front but neither destroy it nor change the near-2D picture of the front evolution critically. Andrei Runov showed average properties of dipolarizing flux bundle (DFB) plasma revealed from statistical studies of 271 events observed by THEMIS. He was found that the average temperature in DFBs increases with respect to the background value by ~1.2 - 1.5 for ions and ~1.5 - 1.7 for electrons, with larger values closer to the Earth. The Ti/Te- ratio depends on distance and reaches ~1 at R < 12 R_E and T > 10 keV. Average ion energy spectra show power-law (J~W^-k) energetic tails with k ~ 3 to 4. Average electron spectra show kappa-like distributions with kappa ~4 to 6. Mike Shay examined the basic properties of 3D reconnection in the magnetotail using a Sweet-Parker-like theory and two-fluid simulations. He found that for a three-dimensional X-line, the "ends" act as an energy sink, reducing the free energy available to create fast outflows. For X-lines smaller than around 10 ion inertial lengths, reconnection is no longer energetically favorable. This minimum length is consistent with typical cross-tail scale sizes of BBFs. Jim Drake presented the results of 3D PIC simulations of the structure of reconnection-driven flow bursts relevant to the magnetotail. He found that for reconnection jets that are around 3 R_E in cross-tail extent that (1) the jets are deflected in both the dawn and dusk directions at the front and (2) the body of the jet behind the front breaks up, producing large variations in Bz as seen in most of the satellite observations. The mechanism for the breakup is presently being explored. Heli Hietala discussed ion temperature anisotropy profiles across reconnection exhausts using both ARTEMIS observations from the Earth's magnetotail at lunar distances and 2.5 dimensional Particle-In-Cell simulations. She found excellent agreement between the observations and simulations: the temperature parallel to the magnetic field dominates at the edges of the exhaust and the firehose instability threshold is often greatly exceeded, yet the perpendicular temperature dominates at the neutral plane. Session 4 - Joint with "The Magnetosheath" Focus Group - Thursday, June 19, 3:30-5:00pm Please see the summary in the Magnetosheath section. Future Directions The discussions at the 2014 GEM Workshop exposed interesting and important areas where a consensus has not yet been formed. Future work on what sets the rate of dayside reconnection, what sets the scale of transient structures in the magnetotail, and the relative importance of reconnection vs. interchange type modes in magnetotail dynamics will continue to be discussed at future GEM meetings. In 2015, we expect exciting sessions on the kinetic physics of reconnection in conjunction with the launch of MMS in early 2015. Outstanding questions such as heating and particle acceleration at electron scales will be addressed. ---------------------------------------------------------------------- 2. Deadline for Early Bird Registration: October 23, 2014 IMC III workshop, March 23-27, UCLA ---------------------------------------------------------------------- From: Yuri Shprits The third Inner Magnetosphere Coupling (IMC-III) workshop will be held at the University of California, Los Angeles on March 23 – 27 (Monday –Friday), 2015. The IMC-III workshop will bring together researchers to examine and discuss the strongly coupled inner magnetospheric system and how disturbances from the Sun can propagate to the inner magnetosphere, radically altering the plasma and wave distributions, and ultimately influence the ionosphere and upper atmosphere. The meeting will follow the format of the previous two IMC meetings (IMC-I in Espoo, Finland in 2008 and IMC-II at UCLA in 2012) and will be organized around a set of discussion topics each led by discussion leaders. The workshop focuses on open and informal discussion, with each speaker's presentation being followed by an equal length discussion time. The meeting website is located at: http://www.i-mp.org/conference/i- mp_2015/ IMPORTANT DEADLINES Deadline for early bird registration: 23 Oct 2014 Deadline for regular registration: 20 Dec 2014 Deadline for abstracts: 20 Dec 2014 TUTORIAL SPEAKERS Mark Moldwin, Ramona Kessel DISCUSSION TOPICS: DISCUSSION LEADERS Solar wind and magnetosphere: D. Baker, T. Pulkkinen Plasmasphere, ring current, and radiation belts: M. Chen, M. Liemohn Plasma and magnetic field: C. Lemon, V. Jordanova Waves in plasma: N. Meredith, W. Li Plasma sheet injections: B. Lavraud, M. Gkioulidou Combining models and observations: M. Hudson, S. Elkington Innovative methods for data analysis: D. Turner, S. Claudepierre Mission Synergy: Y. Miyoshi, A. Runov, H. Spence Ionosphere-Thermosphere-Magnetosphere: M. Moldwin, D. Welling Space Weather and Applications: J. Green, M. 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