[GEM] THE GEM MESSENGER, Volume 25, Number 36

Newsletter Editor editor at igpp.ucla.edu
Mon Sep 7 08:55:59 PDT 2015


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     THE GEM MESSENGER
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Volume 25, Number 36
September 7, 2015

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Table of Contents

1. Dear Colleague Letter: NSF/AGS, Geospace Section Program Directors Search (modified 8/27/2015)

2. 2015 Summer Workshop Report: Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures Focus Group
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1. Dear Colleague Letter: NSF/AGS, Geospace Section Program Directors Search (modified 8/27/2015)
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From: Janet Kozyra (jkozyra at nsf.gov)

Employment Opportunity--Dear Colleague Letter Date: July 17, 2015, modified August 27, 2015

Dear Colleague:

The Division of Atmospheric and Geospace Sciences (AGS) announces a nationwide search to fill several Program Director rotator positions within the Geospace Section. This is a modified version of the original DCL (released July 17, 2015) to include the possibility of a broader range in types of rotator and temporary assignments considered and to indicate scientific areas that are the intended focus for the initial open positions. Rotator positions can be either Intergovernmental Personnel Assignment (IPA) or Visiting Scientist, Engineer, and Educator (VSEE) assignments. For more information regarding rotator assignments and eligibility, visit our website at https://www.nsf.gov/careers/rotator/. Fed Temp employment is also a possibility.

The current position of highest priority is Aeronomy Program Director. However, a second program director with broad knowledge of geospace science, to enable contribution to multiple programs within the Geospace Section is also desired. In the longer term, this letter is intended to serve as an ongoing mechanism for recruiting program directors to fill positions vacated by rotators who have returned to their home institutions.

For more details about the requirements for the positions, see the full text of the DCL at http://www.nsf.gov/pubs/2015/ags15001/ags15001.jsp?WT.mc_id=USNSF_147 .

Formal consideration of interested applicants began August 17, 2015, as specified in an earlier version of this DCL, and will continue until selection is made. Individuals interested in applying for this position should send a current CV and letter of interest to:

Janet Kozyra, Acting Section Head
Division of Atmospheric and Geospace Sciences, Suite 775
National Science Foundation 4201 Wilson Blvd.
Arlington, VA 22230
Phone: 703-292-8519
Fax: 703-292-9022
Email: jkozyra at nsf.gov

Those who have already applied in response to the earlier version of the DCL need not re-apply. Questions about the positions can be directed to the above or any of the Geospace program directors:

Therese Moretto Jorgensen, Space Weather <tjorgens at nsf.gov>
Ilia Roussev, Solar-Terrestrial Relations <iroussev at nsf.gov>
Sunanda Basu, Aeronomy <sbasu at nsf.gov>
John Meriwether, Geospace Facilities <jmeriwet at nsf.gov>

NSF IS AN EQUAL OPPORTUNITY EMPLOYER

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2. 2015 Summer Workshop Report: Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures Focus Group
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From: Hui Zhang (hzhang14 at alaska.edu), Q.-G. Zong, David Murr, and Michael Ruohoniemi

The "Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures" focus group held three sessions with 14 presentations covering the following research areas: 1. Foreshock Phenomena 2. Magnetosheath and Magnetopause Phenomena 3. Ground Signatures 

1. 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. 

Liu et al. presented a hypothesis about the tangential discontinuity (TD)-driven FB formation and supported their hypothesis by THEMIS observations. They suggested that a statistical study should be applied to compare RD- vs. TD-driven FBs in order to fully understand how FBs are formed. In addition, their observational results should be examined with global hybrid simulations to further validate the premise and the process of FB formation by TDs.

Statistical studies on HFAs have been done using Cluster and THEMIS datasets. Zhang et al. identified 199 classical HFAs from Cluster observations from 2001 to 2010. 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” and “M” type HFAs are mature HFAs and most “-+” and “+-” type HFAs are young HFAs, indicating that “M” and “W” type HFAs may be the later evolution stages of “-+” and “+-” type HFAs. They also found that variations of plasma parameters and magnetic field of mature HFAs are more dramatic than those of young HFAs, except for temperature. They suggested that the four categories of HFAs may also be due to the fact that the spacecraft crossed an HFA structure along different paths. 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 HFAs were observed up to 6.3 RE upstream from the bow shock and their occurrence decreases with distance upstream from the bow shock. 

Using global hybrid simulations, Omidi et al. investigated impacts of SHFAs on the magnetosheath and magnetopause. They demonstrated that in addition to the formation of Magnetosheath Filamentary Structures (MFS), SHFAs results in the formation of large-scale cavities in the magnetosheath which are associated with decreases in density and magnetic field strength and an increase in ion temperature. They also showed regions of high flow speeds form as a result of SHFAs which may correspond to magnetosheath jets observed by spacecraft. They also showed that SHFAs can cause in and out motion of the magnetopause.  

2. Magnetosheath and Magnetopause Phenomena

The broad topics of this session were (1) phenomena 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 an anti-correlation between the density and ion temperature within these structures which are consistent with the MFS in hybrid simulations.

Ahmadi et al. investigated effects of electron anisotropy on mirror instability evolution in the magnetosheath using PIC simulation. They found that electron distribution becomes isotropic before proton instabilities can grow, because electron whistler instability grows much faster than proton cyclotron or proton mirror instabilities. They also found that in expanding box simulations, electrons become anisotropic same as protons but electron whistler instability starts growing quicker than proton instabilities and keeps electron distribution close to equilibrium.

Sibeck introduced a recently selected mission called Solar wind Magnetosphere Ionosphere Link Explorer (SMILE). This is a joint mission between European Space Agency and Chinese Academy of Sciences studying interaction between Earth's magnetosphere and solar wind. SMILE will be able to simultaneously capture images and movies of the magnetopause, polar cusps, and aurora. 

Wang et al. presented ARTEMIS observations of the hot electron enhancement in mid-tail magnetosheath and its dawn-dusk asymmetry. They found that hot electron enhancements occur 3-4 times more often on dawnside magnetosheath than duskside magnetosheath and fluxes of hot electron enhancements are twice larger on the dawnside than on the duskside. They suggested that the dawn-dusk asymmetry may be caused by processes at quasi-parallel bow shock.

Wash et al. proposed a new theory to explain the dawn-dusk asymmetry (more at dusk) of the Kelvin-Helmholtz waves at the dayside magnetopause. They proposed that the high plasma density associated with the plasmaspheric plumes at the dusk side of the dayside magnetosphere make the Kelvin-Helmholtz waves more likely to occur at the dusk side magnetopause. 

Hartinger et al. investigated the global structure and time evolution of dayside magnetopause surface eigenmodes. They found that magnetopause surface eigenmodes are a potential source of ULF waves below 2 mHz and magnetopause surface eigenmodes can seed tailward propagating surface waves via the Kelvin-Helmholtz instability.

Lee et al. presented statistical studies on the characteristics of the cold dense ions observed at the dayside magnetopause by using the Cluster spacecraft datasets. They found that the occurrence rate of plasmaspheric plume or ionospheric plasma strongly depends on the solar wind/IMF conditions. In particular, plasmaspheric plumes tend to occur during southward IMF, whereas ionospheric outflows tends to occur during northward IMF. The occurrence rate of the plasmaspheric plumes is significantly higher on the duskside than that on the dawnside.  

3. 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. 

Hartinger et al. presented observational results on the effect of northern-southern hemisphere conductivity asymmetries on ground magnetic responses during a large solar wind transient. They showed that magnetic perturbations excited by a solar wind pressure increase were observed at magnetically conjugate stations in the northern and southern hemispheres. These perturbations have essentially the same amplitude and timing, contrary to expectations for solstice conditions – i.e., ionospheric conductivity does not appear to affect the properties of the magnetic perturbations, which differs from previous studies showing large inter-hemispheric differences.

Connor et al. presented OpenGGCM-CTIM simulation results of thermospheric heating in the high-latitude dayside regions after the sudden enhancement of solar wind pressure. They showed that the coupled MIT model produces localized increase of electric field and aurora precipitation in the high-latitude dayside region after the solar wind dynamic pressure impact, which in turn effectively heat the thermosphere and causes the neutral density increases at 400 km altitude. Their model results demonstrate that the physics-based magnetospheric energy input is critical to improve ionosphere-thermosphere model predictions.

Oliveira et al. investigated the geoeffectiveness of IP shock impact angles using global MHD simulations and observations. They found that the Earth’s magnetosphere and ionosphere respond to IP shocks in different ways depending on the shock impact angle. In general, strong (high speed) and almost frontal (small impact angle) shocks are more geoeffective than inclined shocks with low speed. They attribute this result to the fact that frontal shocks compress the magnetosphere symmetrically from all sides, which is a favorable condition for the release of magnetic energy stored in the magnetotail, which can produce moderate to strong substorms and magnetic field perturbations observed by ground-based magnetometers.

Finally, we discussed post summer work group plan. This focus group is supposed to end in the summer of 2016. Considering that MMS-Cluster-THEMIS conjunctions in 2016 will provide excellent opportunities for this focus group, people suggest that we ask for a 1-year extension.


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