ALBERT

Description: Abstract Here we present some unique observations of reconnection at a quasi‐perpendicular bow shock as an interplanetary directional discontinuity (DD) is crossing it simultaneously with the Magnetospheric Multiscale (MMS) mission. There are no burst data, but available data show indications of ongoing reconnection at the shock southward of MMS: a bifurcated current sheet with signatures of Hall magnetic and electric fields, normal magnetic fields indicating a magnetic connection between the two reconnecting regions, field‐aligned currents and electric fields, E·J〉0 indicating a conversion of magnetic to kinetic energy, and {and sub‐spin resolution ion energy‐time spectrograms indicating ions being accelerated away from the X‐line. The DD is also observed by four upstream spacecraft (ACE, WIND, Geotail, and ARTEMIS P1) and one downstream in the magnetosheath (Cluster 4), but none of them resolve signatures of ongoing reconnection. We therefore suggest that reconnection was temporarily triggered as the DD was compressed by the shock. Reconnection at the bow shock is inevitably asymmetric with both the density and magnetic field strength being higher on one side of the X‐line (magnetosheath side) than on the other side where the plasma flow also is supersonic (solar wind side). This is different from the asymmetry exhibited at the more commonly studied case of asymmetric reconnection at the magnetopause. Asymmetric reconnection of the bow shock type has never been studied before, and the data discussed here present some first indications of the properties of the reconnection region for this type of reconnection.

Description: This study is the first to combine energetic neutral atom (ENA) observations from Two Wide-Angle Imaging Neutral-Atom Spectrometers (TWINS) and Interstellar Boundary Explorer (IBEX). Here we examine the arrival of an interplanetary shock and the subsequent geomagnetically effective substorm on 5 April 2010, which was associated with the Galaxy 15 communications satellite anomaly. IBEX shows sharply enhanced ENA emissions immediately upon compression of the dayside magnetosphere at 08:26:17+/−9 s UT. The compression drove a markedly different spectral shape for the dayside emissions, with a strong enhancement at energies 〉1 keV, which persisted for hours after the shock arrival, consistent with the higher solar wind speed, density, and dynamic pressure (∼10 nPa) after the shock. TWINS ENA observations indicate a slower response of the ring current and precipitation of ring current ions as low-altitude emissions ∼15 min later, with the 〉50 keV ion precipitation leading the 

Description: Abstract Using observations of Earth's bow shock by the Magnetospheric Multiscale mission, we show for the first time that active magnetic reconnection is occurring at current sheets embedded within the quasi‐parallel shock's transition layer. We observe an electron jet and heating but no ion response, suggesting we have observed an electron‐only mode. The lack of ion response is consistent with simulations showing reconnection onset on sub‐ion time scales. We also discuss the impact of electron heating in shocks via reconnection.

Description: Simulations of energetic neutral atom (ENA) maps predict flux magnitudes that are, in some cases, similar to those observed by the Interstellar Boundary Explorer (IBEX) spacecraft, but they miss the ribbon. Our model of the heliosphere indicates that the local interstellar medium (LISM) magnetic field (B(LISM)) is transverse to the line of sight (LOS) along the ribbon, suggesting that the ribbon may carry its imprint. The force-per-unit area on the heliopause from field line draping and the LISM ram pressure is comparable with the ribbon pressure if the LOS approximately 30 to 60 astronomical units and B(LISM) approximately 2.5 microgauss. Although various models have advantages in accounting for some of the observations, no model can explain all the dominant features, which probably requires a substantial change in our understanding of the processes that shape our heliosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schwadron, N A -- Bzowski, M -- Crew, G B -- Gruntman, M -- Fahr, H -- Fichtner, H -- Frisch, P C -- Funsten, H O -- Fuselier, S -- Heerikhuisen, J -- Izmodenov, V -- Kucharek, H -- Lee, M -- Livadiotis, G -- McComas, D J -- Moebius, E -- Moore, T -- Mukherjee, J -- Pogorelov, N V -- Prested, C -- Reisenfeld, D -- Roelof, E -- Zank, G P -- New York, N.Y. -- Science. 2009 Nov 13;326(5955):966-8. doi: 10.1126/science.1180986. Epub 2009 Oct 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, Boston University, Boston, MA 02215, USA. nathanas@bu.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19833915" target="_blank"〉PubMed〈/a〉

Description: We analyze plasma, magnetic and electric field data for a flux transfer event (FTE) to highlight improvements in our understanding of these transient reconnection signatures resulting from high resolution data. The ∼20 s-long, reverse FTE, which occurred south of the geomagnetic equator near dusk, was immersed in super-Alfvénic flow. The field line twist is illustrated by the behavior of flows parallel/perpendicular to the magnetic field. Four-spacecraft timing and energetic particle pitch angle anisotropies indicate a flux rope (FR) connected to the northern hemisphere and moving southeast. The flow forces evidently overcame the magnetic tension. The high-speed flows inside the FR were different from those outside. The external flows were perpendicular to the field as expected for draping of the external field around the FR. Modeling the FR analytically, we adopt a non-force free approach since the current perpendicular to the field is non-zero. It reproduces many features of the observations.

Description: The provenance of water and organic compounds on Earth and other terrestrial planets has been discussed for a long time without reaching a consensus. One of the best means to distinguish between different scenarios is by determining the deuterium-to-hydrogen (D/H) ratios in the reservoirs for comets and Earth's oceans. Here, we report the direct in situ measurement of the D/H ratio in the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA mass spectrometer aboard the European Space Agency's Rosetta spacecraft, which is found to be (5.3 +/- 0.7) x 10(-4)-that is, approximately three times the terrestrial value. Previous cometary measurements and our new finding suggest a wide range of D/H ratios in the water within Jupiter family objects and preclude the idea that this reservoir is solely composed of Earth ocean-like water.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Altwegg, K -- Balsiger, H -- Bar-Nun, A -- Berthelier, J J -- Bieler, A -- Bochsler, P -- Briois, C -- Calmonte, U -- Combi, M -- De Keyser, J -- Eberhardt, P -- Fiethe, B -- Fuselier, S -- Gasc, S -- Gombosi, T I -- Hansen, K C -- Hassig, M -- Jackel, A -- Kopp, E -- Korth, A -- LeRoy, L -- Mall, U -- Marty, B -- Mousis, O -- Neefs, E -- Owen, T -- Reme, H -- Rubin, M -- Semon, T -- Tzou, C-Y -- Waite, H -- Wurz, P -- New York, N.Y. -- Science. 2015 Jan 23;347(6220):1261952. doi: 10.1126/science.1261952. Epub 2014 Dec 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. altwegg@space.unibe.ch. ; Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. ; Department of Geosciences, Tel-Aviv University, Ramat-Aviv, Tel-Aviv, Israel. ; Laboratoire Atmospheres, Milieux, Observations Spatiales (LATMOS), 4 Avenue de Neptune, F-94100 Saint-Maur, France. ; Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward, Ann Arbor, MI 48109, USA. ; Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), UMR 6115 CNRS-Universite d'Orleans, France. ; Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward, Ann Arbor, MI 48109, USA. ; Space Physics Division, Belgisch Instituut voor Ruimte-Aeronomie (BIRA)-Institut d'Aeronomie Spatiale de Belgique (IASB), Ringlaan 3, B-1180 Brussels, Belgium. ; Institute of Computer and Network Engineering (IDA), Technicsche Universitat Braunschweig, Hans-Sommer-Strasse 66, D-38106 Braunschweig, Germany. ; Department of Space Science, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228, USA. ; Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. Department of Space Science, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228, USA. ; Max-Planck-Institut fur Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Gottingen, Germany. ; Centre de Recherches Petrographiques et Geochimiques, Centre de Recherches Petrographiques et Geochimiques (CRPG)-CNRS, Universite de Lorraine, 15 rue Notre Dame des Pauvres, BP 20, 54501 Vandoeuvre les Nancy, France. ; Universite de Franche-Comte, Institut Univers, Transport, Interfaces, Nanostructures, Atmosphere et Environnement, Molecules (UTINAM), CNRS/Institut National des Sciences de l'Univers (INSU), UMR 6213 Besancon Cedex, France. ; Institute for Astronomy, University of Hawaii, Honolulu, HI 96822, USA. ; Universite de Toulouse, Universite Paul Sabatier (UPS)-Observatoire Midi-Pyrenees (OMP), Institut de Recherche en Astrophysique et Planetologie (IRAP), Toulouse, France. CNRS, IRAP, 9 Avenue du Colonel Roche, BP 44346, F-31028 Toulouse cedex 4, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25501976" target="_blank"〉PubMed〈/a〉

Description: Abstract Cold plasma (up to few tens of eV) of ionospheric origin is present most of the time, in most of the regions of the Earth's magnetosphere. However, characterizing it using in‐situ measurements is difficult, owing to spacecraft electrostatic charging, as often this charging is at levels comparable to or even higher than the equivalent energy of the cold plasma. To overcome this difficulty, active potential control devices are usually placed on spacecraft that artificially reduce spacecraft charging. The electrostatic potential structure around the spacecraft is often assumed to be spherically symmetric, and corrections are applied to the measured particle distribution functions. In this work, we show that large deviations from the spherical model are present, owing to the presence of long electric field booms. We show examples using MMS spacecraft measurements of the electrostatic potential structure and its effect on the measurement of cold ion beams. Overall, we find that particle detectors underestimate the cold ion density under certain conditions, even when their bulk kinetic energy exceeds the equivalent spacecraft potential energy and the ion beam reaches the spacecraft. Active potential control helps reducing this unwanted effect, but we show one event with large cold ion density (~10 cm‐3) where particle detectors provide density estimates a factor of 3‐5 below the density estimated from the plasma frequency. Understanding these wake effects indirectly constrains some properties of the magnetospheric cold ion component, such as their drift energy, direction and temperature.

Description: Observations by the Magnetospheric Multiscale spacecraft (MMS) of an unusual layer, located between the dayside magnetosheath and the magnetosphere, alternating with encounters with the magnetosheath during an extended time period between December 31, 2015 and January 01, 2016, when the interplanetary magnetic field was strongly southward and the Earth's dipole tilt large and negative, are presented. It appears to have been magnetically connected to both magnetosphere and magnetosheath. The layer appears to be located mostly on closed field lines and was bounded by a rotational discontinuity (RD) at its magnetosheath edge and by the magnetosphere on its earthward side. A separatrix layer, with heated magnetosheath electrons streaming unidirectionally along the field lines, was present sunward of the RD. We infer that the layer was started by a dominant reconnection site well north of the spacecraft and that it may have gained additional width, from a large drop in solar wind density and ram pressure, which preceded the beginning of the event by more than an hour. Relative to the magnetosheath, in which the magnetic field was strongly southward, this unusual layer was characterized by a less southward, more dawnward magnetic field of lower magnitude. The plasma density and flow speed in the region were lower than in the magnetosheath, albeit with Alfvénic jetting occurring at the magnetosheath edge as well as at the magnetospheric edge of the layer. The closing of the magnetic field lines requires the existence of another reconnection site, located southward/tailward of MMS.

Description: Key Points: Magnetopause encounter for strongly southward interplanetary magnetic field, low solar wind Alfvén Mach number, and large dipole tilt. Persistent and broad magnetopause layer with magnetospheric O+ and heated magnetosheath plasma. Inferred dominant reconnection site near northern cusp, far from the Magnetospheric Multiscale spacecraft location.

Description: MPE

Description: NASA http://dx.doi.org/10.13039/100000104

Description: Norwegian Research Council http://dx.doi.org/10.13039/501100005416