Table of Contents ====================================================================== 1. GEM 2014 Mini-Workshop Agenda 2. 2014 WORKSHOP REPORT: Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures Focus Group ====================================================================== *************************** ** THE GEM MESSENGER ** *************************** Volume 24, Number 34 October 17, 2014 ---------------------------------------------------------------------- 1. GEM 2014 Mini-Workshop Agenda ---------------------------------------------------------------------- From: Xia Cai (xcai@vt.edu) The GEM 2014 Mini-Workshop will be held on December 14th at Westin San Francisco Market Street in San Francisco, CA. It is the Sunday right before the 2014 Fall AGU Meeting. The registration is free. The workshop agenda is accessible from the front page of GemWiki. The direct web link is: http://spc.igpp.ucla.edu/gem/pdf/2014GEM_mini_agenda.pdf . Please contact Xia (xcai@vt.edu) if you have any questions regarding the Workshop. ---------------------------------------------------------------------- 2. 2014 WORKSHOP REPORT: Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures Focus Group ---------------------------------------------------------------------- From: Hui Zhang , Q.-G. Zong, Michael Ruohoniemi, and David Murr The "Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures" focus group held three sessions with 19 presentations. The sessions were organized as follows: 1. Foreshock Phenomena 2. Magnetopause Phenomena 3. Ground Signatures Session 1 – Wednesday, June 18, 1:30-3:00pm (Foreshock Phenomena) Various foreshock phenomena including hot flow anomaly (HFA), spontaneous hot flow anomalies (SHFAs), and foreshock bubbles (FBs) were investigated by this focus group using both in-situ observations and global hybrid simulations. Turner et al. discussed particle acceleration in transient ion foreshock phenomena. They showed the evolution of the ion and electron pitch angle distributions inside an HFA and a foreshock bubble and concluded that transient ion foreshock phenomena are particularly efficient for both ion and electron acceleration. Liu et al. calculated the expansion speed of an HFA and a foreshock bubble using 5-point THEMIS observations. They found that the foreshock bubble is expanding at a speed of 168km/s, faster than that of the HFA (76km/s). However, the expanding rate of the foreshock bubble is much smaller than that of the HFA because the foreshock bubble is much larger than the HFA. Great progress has been made on SHFA studies. Using global hybrid simulations, Omidi et al. investigated the parametric dependencies of SHFAs. They demonstrated that SHFAs are formed sporadically at MA = 3 and SHFAs are formed frequently at higher Mach numbers. They also found that the size of SHFAs and the level of ion heating increase with MA. They also showed that SHFAs can form at cone angles as large as 90 degree as long as MA > 3. Statistical studies on HFAs have been done using Cluster and THEMIS datasets. Chu et al. presented a statistical study of both HFAs and SHFAs using THEMIS data. They showed that both mature and young HFAs are more prevalent when there is an approximately radial interplanetary magnetic field. They also found that no HFAs or SHFAs were observed when the Mach number was less than 5, suggesting there is a minimum threshold Mach number for HFAs and SHFAs to form. Zong et al. identified more than 600 HFAs from Cluster-C1 observations from 2001 to 2012. These HFAs were classified into four categories (“-+”, “+-”, “M”, and “W”) according their dynamic pressure profile. HFAs were classified as young and mature according to the ion distributions. They found that most “W” type HFAs are mature HFAs and most “-+” and “+-” type HFAs are young HFAs. They also found that mature HFAs are pressure balanced while the pressure is higher inside young HFAs than that outside. Otto et al. investigated bow shock interaction with transient solar wind structures using an MHD simulation. They found that the interaction of the bow shock with a density depletion structure in the solar wind results in a sunward flow, which may provide an alternate mechanism for the formation of HFAs. Session 2 – Wednesday, June 18, 3:30-5:00pm (Magnetopause Phenomena) The broad topics of this session were (1) density enhancements in the magnetosheath, (2) plasma transport into the magnetosphere due to Kelvin-Helmholtz instabilities (KHI) and magnetic reconnection, and (3) the effect of cold ions (plasmaspheric plume or ionospheric outflow) and cusp ions on reconnection and KHI at the magnetopause. Gutynska et al. investigated the density enhancements in the magnetosheath using THEMIS observations and compared their results with those from global hybrid simulations. They found that density enhancements are mostly observed for small core and Theta BN angles. They also noted an anti-correlation between the density and ion temperature within these structures. Connor et al. presented OpenGGCM-LTPT simulation results of cusp ion signatures and their relation to dayside reconnection during four IMF clock angles. They found that during northward IMF, both northern and southern magnetic reconnection produce ion precipitation into the northern cusp. They also found that during 120° clock angle, the coexistence of component and anti-parallel reconnection produces a flat and dispersed signature. During 60° clock angle, repetitive FTE formation on the southern magnetopause causes double reserve dispersions. Lee et al. presented asymmetric ionospheric outflows observed at the dayside magnetopause by the Cluster spacecraft. They found that the cold ions are originated from the southern ionosphere and may affect the reconnection dynamics at the magnetopause. Hwang et al. discussed the effect of plasmaspheric plume on magnetic reconnection and KHI. They pointed out that plasmaspheric plume may reduce the reconnection rate while it facilitates the excitation of the KHI, thus it may play an important role in controlling the competition between reconnection and KHI during southward IMF. They further pointed out that the plasmaspheric plume (mainly located on the dusk side) can lead to the dawn-dusk asymmetry of the KHI. Kavosi et al. conducted a survey of KHI using THEMIS data. They found that KH waves are present at the magnetopause approximately 21% of the time. They also showed increasing KHI occurrences with increasing solar velocity and Mach number. They also found that KH waves were more frequently observed under southward IMF condition than they expected. Session 3 – Thursday, June 19, 10:30 am - 12:15 pm (Ground Signatures) The foreshock phenomena may have significant impacts on the Earth’s Magnetosphere-Ionosphere System. Presentations in this session used a variety of space- and ground-based measurements to examine the response of the magnetosphere to solar wind transients and various foreshock phenomena. Zhang et al. presented THEMIS observations of an extreme HFA which lasted 17 mins near the prenoon bow shock. They showed that this HFA deformed the magnetopause by at least 4 RE. Observations of the IMAGE magnetometer network at 9 MLT show clear response to this extreme HFA. Cluster located in the dawnside magnetotail also observed a clear response to this extreme HFA. Hartinger et al. demonstrated that large, rapid magnetopause displacements are effective drivers of non- sinusoidal ULF waves in dayside magnetosphere. They pointed out that these perturbations are a substantial fraction of background values, therefore we cannot necessarily assume linear ULF response of magnetosphere during periods with substantial magnetopause motion (e.g., caused by HFAs, FBs, large solar wind pressure pulses). However, Murr et al. showed that not all foreshock transients cause ground signatures. This is not surprising but it means that we will now need to focus some effort on studying how different foreshock transients deform the magnetopause and which deformations are effective in driving field-aligned current systems in the MI system. Chi et al. investigated the magnetospheric response to interplanetary field enhancements (IFE) using coordinated ground-based and space- based observations. They found that the IFE-induced ionospheric current vortices are opposite to those induced by sudden impulses. Kim et al. presented conjugate observations of TCVs and EMIC waves associated with transient events at the magnetopause. They showed MIEs/TCVs observed by Greenland and Canadian magnetometers and their conjugate network in Antarctica in response to the solar wind pressure impulse events. They found that EMIC waves (identified as Pc1-2 on the ground) were also observed in conjunction with the TCV events from the ground network. In addition, SuperDARN observed enhanced convection associated with MIEs. There were two talks on optical observations. Motoba et al. discussed the dayside transient aurora at South Pole Station. Mende showed that persistently occurring dayside transients in the aurora are Pole-ward Moving Auroral Forms (PMAF-s) which occur regularly regardless of the direction of the IMF Bz component. Oliveira et al. investigated the geoeffectiveness of IP shock impact angles using global MHD simulations. They concluded that the Earth’s magnetosphere and ionosphere respond to IP shocks in different ways depending on the shock impact angle. +-------------------------------------------------------------------+ | To broadcast announcements to the GEM community, please contact | | Peter Chi, GEM Communications Coordinator, at: | | | | | | Please submit your announcements in plain text or Word document. | | | | To subscribe the GEM Messenger, send an e-mail to | | | | with the following command in the body of your e-mail message: | | subscribe gem | | To remove yourself from the mailing list, the command is: | | unsubscribe gem | | | | GEM Messenger is also posted online via newsfeed at | | http://heliophysics.blogspot.com and | | http://www.facebook.com/heliophysics | | | | Back issues are available at: | | http://www-ssc.igpp.ucla.edu/gemwiki/messenger/ | | | | URL of GEM Home Page: http://aten.igpp.ucla.edu/gemwiki | | Workshop Information: http://www.cpe.vt.edu/gem/index.html | +-------------------------------------------------------------------+