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Journal of Geophysical Research. Space Physics

Yi-Hsin Liu, M Hesse, T C Li, M Kuznetsova, A Le
The orientation and stability of the reconnection x line in asymmetric geometry is studied using three-dimensional (3-D) particle-in-cell simulations. We initiate reconnection at the center of a large simulation domain to minimize the boundary effect. The resulting x line has sufficient freedom to develop along an optimal orientation, and it remains laminar. Companion 2-D simulations indicate that this x line orientation maximizes the reconnection rate. The divergence of the nongyrotropic pressure tensor breaks the frozen-in condition, consistent with its 2-D counterpart...
June 2018: Journal of Geophysical Research. Space Physics
Romina Nikoukar, David J Lawrence, Patrick N Peplowski, Ryan M Dewey, Haje Korth, Daniel N Baker, Ralph L McNutt
We present results from a statistical analysis of Mercury's energetic electron (EE) events as observed by the gamma-ray and neutron spectrometer instrument onboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. The main objective of this study is to investigate possible anisotropic behavior of EE events using multiple data sets from MESSENGER instruments. We study the data from the neutron spectrometer (NS) and the gamma-ray spectrometer anticoincidence shield (ACS) because they use the same type of borated plastic scintillator and, hence, they have very similar response functions, and their large surface areas make them more sensitive to low-intensity EE events than MESSENGER's particle instrumentation...
June 2018: Journal of Geophysical Research. Space Physics
X Shi, J M Ruohoniemi, J B H Baker, D Lin, E C Bland, M D Hartinger, W A Scales
Ionospheric signatures of ultra-low frequency (ULF) wave in the Pc3-5 band (1.7-40.0 mHz) were surveyed using ~6 s resolution data from Super Dual Auroral Radar Network (SuperDARN) radars in the northern hemisphere from 2010 to 2016. Numerical experiments were conducted to derive wave period dependent thresholds for automated detection of ULF waves using the Lomb-Scargle periodogram technique. The spatial occurrence distribution, frequency characteristics, seasonal effects, solar wind condition and geomagnetic activity level dependence have been studied...
May 2018: Journal of Geophysical Research. Space Physics
Chih-Ping Wang, Xiaoyan Xing, Yi-Hsin Liu, Andrei Runov
We report the first observations that connect a burst of fast flows and Pi2 fluctuations in the midtail current sheet at X ~-60 R E with ground magnetic negative bays and Pi2 pulsations at high latitudes near 70°. Both the flow burst and negative bays occurred around midnight and were isolated and lasted for ~10 min. The flow burst had the characteristics of a low-density plasma bubble. It was moving earthward at ~340 km/s and was accompanied by field-aligned currents. The timing and equatorward motion of magnetic bays can be accounted for by this earthward moving bubble...
March 2018: Journal of Geophysical Research. Space Physics
E Astafyeva, I Zakharenkova, K Hozumi, P Alken, P Coïsson, M R Hairston, W R Coley
We use a set of ground-based instruments (Global Positioning System receivers, ionosondes, magnetometers) along with data of multiple satellite missions (Swarm, C/NOFS, DMSP, GUVI) to analyze the equatorial and low-latitude electrodynamic and ionospheric disturbances caused by the geomagnetic storm of 22-23 June 2015, which is the second largest storm in the current solar cycle. Our results show that at the beginning of the storm, the equatorial electrojet (EEJ) and the equatorial zonal electric fields were largely impacted by the prompt penetration electric fields (PPEF)...
March 2018: Journal of Geophysical Research. Space Physics
Stefan J Hofmeister, Astrid Veronig, Manuela Temmer, Susanne Vennerstrom, Bernd Heber, Bojan Vršnak
We study the properties of 115 coronal holes in the time range from August 2010 to March 2017, the peak velocities of the corresponding high-speed streams as measured in the ecliptic at 1 AU, and the corresponding changes of the Kp index as marker of their geoeffectiveness. We find that the peak velocities of high-speed streams depend strongly on both the areas and the co-latitudes of their solar source coronal holes with regard to the heliospheric latitude of the satellites. Therefore, the co-latitude of their source coronal hole is an important parameter for the prediction of the high-speed stream properties near the Earth...
March 2018: Journal of Geophysical Research. Space Physics
S A Kiehas, A Runov, V Angelopolos, H Hietala, D Korovinksiy
As a direct result of magnetic reconnection, plasma sheet fast flows act as primary transporter of mass, flux, and energy in the Earth's magnetotail. During the last decades, these flows were mainly studied within X GSM >-60 R E , as observations near or beyond lunar orbit were limited. By using 5 years (2011-2015) of ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moons Interaction with the Sun) data, we statistically investigate earthward and tailward flows at around 60  R E downtail...
March 2018: Journal of Geophysical Research. Space Physics
Rumi Nakamura, Ali Varsani, Kevin J Genestreti, Olivier Le Contel, Takuma Nakamura, Wolfgang Baumjohann, Tsugunobu Nagai, Anton Artemyev, Joachim Birn, Victor A Sergeev, Sergey Apatenkov, Robert E Ergun, Stephen A Fuselier, Daniel J Gershman, Barbara J Giles, Yuri V Khotyaintsev, Per-Arne Lindqvist, Werner Magnes, Barry Mauk, Anatoli Petrukovich, Christopher T Russell, Julia Stawarz, Robert J Strangeway, Brian Anderson, James L Burch, Ken R Bromund, Ian Cohen, David Fischer, Allison Jaynes, Laurence Kepko, Guan Le, Ferdinand Plaschke, Geoff Reeves, Howard J Singer, James A Slavin, Roy B Torbert, Drew L Turner
We present characteristics of current layers in the off-equatorial near-Earth plasma sheet boundary observed with high time-resolution measurements from the Magnetospheric Multiscale mission during an intense substorm associated with multiple dipolarizations. The four Magnetospheric Multiscale spacecraft, separated by distances of about 50 km, were located in the southern hemisphere in the dusk portion of a substorm current wedge. They observed fast flow disturbances (up to about 500 km/s), most intense in the dawn-dusk direction...
February 2018: Journal of Geophysical Research. Space Physics
J L Burch, J M Webster, K J Genestreti, R B Torbert, B L Giles, S A Fuselier, J C Dorelli, A C Rager, T D Phan, R C Allen, L-J Chen, S Wang, O Le Contel, C T Russell, R J Strangeway, R E Ergun, A N Jaynes, P-A Lindqvist, D B Graham, F D Wilder, K-J Hwang, J Goldstein
This paper reports on Magnetospheric Multiscale observations of whistler mode chorus and higher-frequency electrostatic waves near and within a reconnection diffusion region on 23 November 2016. The diffusion region is bounded by crescent-shaped electron distributions and associated dissipation just upstream of the X-line and by magnetic field-aligned currents and electric fields leading to dissipation near the electron stagnation point. Measurements were made southward of the X-line as determined by southward directed ion and electron jets...
February 2018: Journal of Geophysical Research. Space Physics
H K Knight, I A Galkin, B W Reinisch, Y Zhang
A large number (~1000) of coincident auroral far ultraviolet (FUV) and ground-based ionosonde observations are compared. This is the largest study to date of coincident satellite-based FUV and ground-based observations of the auroral E region. FUV radiance values from the NASA Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) Global Ultraviolet Imager (GUVI) and the Defense Meteorological Satellite Program (DMSP) F16 and F18 Special Sensor Ultraviolet Spectrographic Imager (SSUSI) are included in the study...
2018: Journal of Geophysical Research. Space Physics
E Astafyeva, I Zakharenkova, J D Huba, E Doornbos, J van den IJssel
By using data from multiple instruments, we investigate ionospheric/thermospheric behavior during the period from 21 to 23 June 2015, when three interplanetary shocks (IS) of different intensities arrived at Earth. The first IS was registered at 16:45 UT on 21 June and caused ~50 nT increase in the SYM-H index. The second IS arrived at 5:45 UT on 22 June and induced an enhancement of the auroral/substorm activity that led to rapid increase of thermospheric neutral mass density and ionospheric vertical total electron content at high latitudes...
November 2017: Journal of Geophysical Research. Space Physics
A Varsani, R Nakamura, V A Sergeev, W Baumjohann, C J Owen, A A Petrukovich, Z Yao, T K M Nakamura, M V Kubyshkina, T Sotirelis, J L Burch, K J Genestreti, Z Vörös, M Andriopoulou, D J Gershman, L A Avanov, W Magnes, C T Russell, F Plaschke, Y V Khotyaintsev, B L Giles, V N Coffey, J C Dorelli, R J Strangeway, R B Torbert, P-A Lindqvist, R Ergun
During a magnetic storm on 23 June 2015, several very intense substorms took place, with signatures observed by multiple spacecraft including DMSP and Magnetospheric Multiscale (MMS). At the time of interest, DMSP F18 crossed inbound through a poleward expanding auroral bulge boundary at 23.5 h magnetic local time (MLT), while MMS was located duskward of 22 h MLT during an inward crossing of the expanding plasma sheet boundary. The two spacecraft observed a consistent set of signatures as they simultaneously crossed the reconnection separatrix layer during this very intense reconnection event...
November 2017: Journal of Geophysical Research. Space Physics
R T Desai, M M Cowee, H Wei, X Fu, S P Gary, M Volwerk, A J Coates
In the vicinity of Europa, Galileo observed bursty Alfvén-cyclotron wave power at the gyrofrequencies of a number of species including K+ , O 2+, Na+ , and Cl+ , indicating the localized pickup of these species. Additional evidence for the presence of chlorine was the occurrence of both left-hand (LH) and right-hand (RH) polarized transverse wave power near the Cl+ gyrofrequency, thought to be due to the pickup of both Cl+ and the easily formed chlorine anion, Cl- . To test this hypothesis, we use one-dimensional hybrid (kinetic ion, massless fluid electron) simulations for both positive and negative pickup ions and self-consistently reproduce the growth of both LH and RH Alfvén-cyclotron waves in agreement with linear theory...
October 2017: Journal of Geophysical Research. Space Physics
L B Wilson, A Koval, A Szabo, M L Stevens, J C Kasper, C A Cattell, V V Krasnoselskikh
A study of the structure of 145 low-Mach number ( M ≤ 3), low-beta ( β ≤ 1), quasi-perpendicular interplanetary collisionless shock waves observed by the Wind spacecraft has provided strong evidence that these shocks have large-amplitude whistler precursors. The common occurrence and large amplitudes of the precursors raise doubts about the standard assumption that such shocks can be classified as laminar structures. This directly contradicts standard models. In 113 of the 145 shocks (~78%), we observe clear evidence of magnetosonic-whistler precursor fluctuations with frequencies ~0...
September 2017: Journal of Geophysical Research. Space Physics
Philip A Fernandes, Brian A Larsen, Michelle F Thomsen, Ruth M Skoug, Geoffrey D Reeves, Michael H Denton, Reinhard H W Friedel, Herbert O Funsten, Jerry Goldstein, Michael G Henderson, Jörg-Micha Jahn, Elizabeth A MacDonald, David K Olson
The two full precessions in local time completed by the Van Allen Probes enable global specification of the near-equatorial inner magnetosphere plasma environment. Observations by the Helium-Oxygen-Proton-Electron (HOPE) mass spectrometers provide detailed insight into the global spatial distribution of electrons, H+ , He+ , and O+ . Near-equatorial omnidirectional fluxes and abundance ratios at energies 0.1-30 keV are presented for 2 ≤ L ≤ 6 as a function of L shell, magnetic local time (MLT), and geomagnetic activity...
September 2017: Journal of Geophysical Research. Space Physics
Liam M Kilcommons, Robert J Redmon, Delores J Knipp
We have developed a method for reprocessing the multi-decadal, multi-spacecraft Defense Meteorological Satellite Program Magnetometer (DMSP SSM) dataset and have applied it to fifteen spacecraft-years of data (DMSP Flight 16-18, 2010-2014). This Level-2 dataset improves on other available SSM datasets with recalculated spacecraft locations and magnetic perturbations, artifact signal removal, representations of the observations in geomagnetic coordinates, and in-situ auroral boundaries. Spacecraft locations have been recalculated using ground-tracking information...
August 2017: Journal of Geophysical Research. Space Physics
Robert J Redmon, William F Denig, Liam M Kilcommons, Delores J Knipp
Since the mid 1970's, the Defense Meteorological Satellite Program (DMSP) spacecraft have operated instruments for monitoring the space environment from low earth orbit. As the program evolved, so to have the measurement capabilities such that modern DMSP spacecraft include a comprehensive suite of instruments providing estimates of precipitating electron and ion fluxes, cold/bulk plasma composition and moments, the geomagnetic field, and optical emissions in the far and extreme ultraviolet. We describe the creation of a new public database of precipitating electrons and ions from the Special Sensor J (SSJ) instrument, complete with original counts, calibrated differential fluxes adjusted for penetrating radiation, estimates of the total kinetic energy flux and characteristic energy, uncertainty estimates, and accurate ephemerides...
August 2017: Journal of Geophysical Research. Space Physics
Ping Yin, Ya-Nan Zheng, Cathryn N Mitchell, Bo Li
Ionospheric tomography has been widely employed in imaging the large-scale ionospheric structures at both quiet and storm times. However, the tomographic algorithms to date have not been very effective in imaging of medium- and small-scale ionospheric structures due to limitations of uneven ground-based data distributions and the algorithm itself. Further, the effect of the density and quantity of Global Navigation Satellite Systems data that could help improve the tomographic results for the certain algorithm remains unclear in much of the literature...
June 2017: Journal of Geophysical Research. Space Physics
Mike Lockwood, Mathew J Owens, Suzanne M Imber, Matthew K James, Emma J Bunce, Timothy K Yeoman
Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar flux (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle...
June 2017: Journal of Geophysical Research. Space Physics
S A Kiehas, N N Volkonskaya, V S Semenov, N V Erkaev, I V Kubyshkin, I V Zaitsev
We evaluate the large-scale energy budget of magnetic reconnection utilizing an analytical time-dependent impulsive reconnection model and a numerical 2-D MHD simulation. With the generalization to compressible plasma, we can investigate changes in the thermal, kinetic, and magnetic energies. We study these changes in three different regions: (a) the region defined by the outflowing plasma (outflow region, OR), (b) the region of compressed magnetic fields above/below the OR (traveling compression region, TCR), and (c) the region trailing the OR and TCR (wake)...
March 2017: Journal of Geophysical Research. Space Physics
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