• Issue
    Volume 123, Issue 8
    6103-7147
    August 2018

Issue Information

Free Access

Issue Information

  • Pages: 6103-6106
  • First Published: 27 September 2018

Research Articles

Solar and Heliospheric Physics

Free Access

A Moment-Based Quasilinear Theory for Electron Firehose Instability Driven by Solar Wind Core/Halo Electrons

  • Pages: 6107-6118
  • First Published: 10 July 2018
Key Points

  • Electron firehose instability regulation of solar wind core and halo electrons is explained
  • Macroscopic quasilinear analysis reproduces marginal stability condition for the electron firehose instability
  • Macroquasilinear method may be used within global kinetic solar wind model

Free Access

Comparison of Dust Impact and Solitary Wave Signatures Detected by Multiple Electric Field Antennas Onboard the MMS Spacecraft

  • Pages: 6119-6129
  • First Published: 17 July 2018
Key Points

  • Dust impact detection by multiple electric field antennas in the monopole and dipole configurations
  • Similarities in signatures of dust impacts and solitary waves are discussed
  • Data obtained during the impact of a millimeter-sized object are described in detail

Free Access

Understanding Magnetic Cloud Structure From Shock/Discontinuity Analysis

  • Pages: 6130-6147
  • First Published: 27 July 2018
Key Points

  • The interval of the magnetic cloud is identified by means of the heliospheric current sheet, which happens to be in the ambient region
  • The nature of the studied discontinuities is verified through multiple spacecraft observations
  • A novel method to evaluate the uncertainties of interplanetary tangential discontinuities is provided

Free Access

Comparing Two Intervals of Exceptionally Strong Solar Rotation Recurrence of Galactic Cosmic Rays

  • Pages: 6148-6160
  • First Published: 13 July 2018
Key Points

  • We compare two intervals of exceptionally strong GCR recurrence at solar rotation period, one in 2007–2008 and the other in 2014–2015
  • In both cases the source of solar rotation period recurrence was a coronal hole, but the coronal holes were located quite differently
  • The effect of the coronal hole to GCR intensity was different because of opposite solar polarities during the two intervals

Technical Reports: Methods

Solar and Heliospheric Physics

Open Access

Production of Negative Hydrogen Ions Within the MMS Fast Plasma Investigation Due to Solar Wind Bombardment

  • Pages: 6161-6170
  • First Published: 17 July 2018
Key Points

  • An anomalous population is observed by MMS's electron plasma instruments in the solar wind
  • The population is consistent with negative ions generated by charge exchange within the instrument
  • The errors in the calculation of the electron moments are estimated

Research Articles

Magnetospheric Physics

Free Access

Laser Remote Magnetometry Using Mesospheric Sodium

  • Pages: 6171-6188
  • First Published: 23 May 2018
Key Points

  • Remotely measured the geomagnetic field at a 90-km altitude, this is an altitude that was previously difficult to monitor
  • Measured geomagnetic field was 45,441 nT, comparable to geomagnetic models, with a sensitivity of 162 nT/√Hz
  • Several improvements to the present measurements are discussed; the sensitivity could be improved to better than 1 nT/√Hz

Free Access

Electron Flux Enhancements at L = 4.2 Observed by Global Positioning System Satellites: Relationship With Solar Wind and Geomagnetic Activity

  • Pages: 6189-6206
  • First Published: 25 June 2018
Key Points

  • Electron flux enhancements at 0.1 − 4 MeV are investigated based on 7-year GPS satellites data at L = 4.2
  • Statistics show electron flux enhancements outside the plasmasphere are likely related to chorus-induced energization
  • Electron flux enhancements generally start after the IMF Bz reaches a minimum

Free Access

Distribution of Plasma in the Io Plasma Torus as Seen by Radio Occultation During Juno Perijove 1

  • Pages: 6207-6222
  • First Published: 01 July 2018
Key Points

  • Juno saw the Io plasma torus during Perijove 1
  • The total electron content from the Juno Perijove 1 radio occultation of the Io plasma torus is used to determine the density distribution
  • The Io plasma torus has larger ion temperatures and densities than during the Voyager epoch

Free Access

Statistical Investigation of the Efficiency of EMIC Waves in Precipitating Relativistic Electrons

  • Pages: 6223-6230
  • First Published: 30 June 2018
Key Points

  • Only 127 out of 473 EMIC wave events are associated with REP when POES satellites go through the region conjugate to EMIC wave activity
  • The coincidence occurrence rate is about 10% higher than the random coincidence occurrence rate
  • Proportion of EMIC wave events that are associated with REP: H+ band and He+ band waves occurring simultaneously >H+ band >He+ band

Open Access

Cross-Phase Determination of Ultralow Frequency Wave Harmonic Frequencies and Their Associated Plasma Mass Density Distributions

  • Pages: 6231-6250
  • First Published: 17 July 2018
Key Points

  • We created an automated cross-phase search algorithm capable of detecting multiple harmonics simultaneously
  • We performed a statistical survey of harmonic modes and deduced only the odd modes were present
  • We modeled a bulge in equatorial plasma and showed that a power law was sufficient to describe the plasma mass density distribution

Free Access

MARSIS Observations of Field-Aligned Irregularities and Ducted Radio Propagation in the Martian Ionosphere

  • Pages: 6251-6263
  • First Published: 17 July 2018
Key Points

  • MARSIS on MEX observed both echoes from distant ionospheric irregularities as well as locally ducted echoes in close succession
  • Both effects are consistent with the presence of extended, small-scale field-aligned density irregularities
  • We suggest that these may be the direct result of strong electric fields present at ionospheric altitudes

Free Access

The Meridional Magnetic Field Lines of Saturn

  • Pages: 6264-6276
  • First Published: 19 July 2018
Key Points

  • The meridional magnetic field lines of Saturn were statistically determined using measurements from 2004 to 2016
  • The magnetic field is compressed on the dayside and elongated on the nightside, as expected from viscous interaction with the solar wind
  • The field lines can be represented by using an L extremum parameter divided by a power law expansion in sin (λ)

Free Access

Oxygen Ion Reflection at Earthward Propagating Dipolarization Fronts in the Magnetotail

  • Pages: 6277-6288
  • First Published: 12 July 2018
Key Points

  • The reflection of oxygen ions at the dipolarization front is studied in both observations and simulations
  • A flux dropout could be observed in the O+ spectrum, whose contour is energy dependent and highly correlated with the gyromotion of different energy O+
  • O+ can extend to a further position after the DF due to its larger gyro-radius than that of H+ with the same energy

Open Access

Saturn's Northern Auroras and Their Modulation by Rotating Current Systems During Late Northern Spring in Early 2014

  • Pages: 6289-6306
  • First Published: 13 July 2018
Key Points

  • The 2014 Hubble Space Telescope imagery of Saturn's northern FUV auroras provides updated picture of statistical boundary locations
  • Modulation of auroral intensity by rotating current systems was clearest at dawn local times during the north-south system coalescence
  • This questions the idea that auroral and SKR emission enhancements simply track the rotating current systems

Free Access

Global Three-Dimensional Simulation of the Earth's Magnetospheric and Ionospheric Responses to Small-Scale Magnetic Flux Ropes in the Solar Wind

  • Pages: 6307-6325
  • First Published: 14 July 2018
Key Points

  • MHD simulations are undertaken on the magnetospheric and ionospheric responses to four types of small-scale magnetic flux rope (SMFR)
  • Magnetospheric responses in terms of reconnection, plasma flow, electric field, and pressure are well distinguished among four SMFRs
  • The ionospheric convection pattern and cross-polar cap potential evolve in different ways depending on the impact of specific SMFRs

Free Access

Characterizing Ion Flows Across a Magnetotail Dipolarization Jet

  • Pages: 6326-6334
  • First Published: 17 July 2018
Key Points

  • The dependence of the structure of magnetotail dipolarization jets on cross-tail width is studied through 2-D Riemann simulations
  • For small widths the jet velocity falls well below expectations based on predictions of conventional reconnection models
  • In wide jets the self-generated Hall magnetic field reverses sign compared with traditional predictions on the dawn edge of the jet

Open Access

Dayside Magnetospheric and Ionospheric Responses to a Foreshock Transient on 25 June 2008: 1. FLR Observed by Satellite and Ground-Based Magnetometers

  • Pages: 6335-6346
  • First Published: 20 June 2018
Key Points

  • Both Pc 5 compressional and Alfvén waves are found to be generated by a foreshock transient
  • Magnetospheric responses in the Pc 5 range are localized with clear dawn-dusk asymmetry
  • The dawn-dusk asymmetry of wave power is consistent with the MLT location of the foreshock transient

Free Access

Dayside Magnetospheric and Ionospheric Responses to a Foreshock Transient on 25 June 2008: 2. 2-D Evolution Based on Dayside Auroral Imaging

  • Pages: 6347-6359
  • First Published: 19 June 2018
Key Points

  • We, for the first time, show auroral evolution due to a foreshock transient in high-resolution 2-D imaging
  • By mapping to the magnetosphere, the imaging was able to determine the size (a few Re in Y) and propagation (duskward)
  • Equivalent currents show a pair of FACs. Its duskward propagation is consistent with aurora. The response resembles sudden commencements

Open Access

Energetic Ion Injections Inside Geosynchronous Orbit: Convection- and Drift-Dominated, Charge-Dependent Adiabatic Energization (W = qEd)

  • Pages: 6360-6382
  • First Published: 26 June 2018
Key Points

  • Energetic ion acceleration in injections is proportional to charge state and independent of mass
  • Peak energy of high energy ions injected inside geosynchronous can be modeled as radial flow channels parameterized by their width and flow velocity
  • Ion composition measurements are critical to unraveling ion energization and drifts in injections

Free Access

Generation of Electron Whistler Waves at the Mirror Mode Magnetic Holes: MMS Observations and PIC Simulation

  • Pages: 6383-6393
  • First Published: 24 July 2018
Key Points

  • Electron whistler waves are generated at mirror mode magnetic holes in the magnetosheath
  • Electron temperature anisotropy is enhanced at the center of magnetic holes by trapping and at the edges by Fermi acceleration or deceleration of electrons
  • In deep magnetic holes, low energy electrons resonate with the electron whistler waves and are isotropized, while higher energy electrons remain anisotropic inside the magnetic holes

Free Access

EMIC Wave Events During the Four GEM QARBM Challenge Intervals

  • Pages: 6394-6423
  • First Published: 15 July 2018
Key Points

  • EMIC waves can rapidly deplete fluxes of ultrarelativistic electrons, but their occurrences are limited in both space and time
  • EMIC wave observations by magnetospheric spacecraft are supplemented by observations from ground-based magnetometers and POES satellites
  • Many but not all EMIC wave events correlated with major or minor depletions of ultrarelativistic electrons observed by the Van Allen Probes

Free Access

Spacecraft-Charging Mitigation of a High-Power Electron Beam Emitted by a Magnetospheric Spacecraft: Simple Theoretical Model for the Transient of the Spacecraft Potential

  • Pages: 6424-6442
  • First Published: 29 May 2018
Key Points

  • A theoretical model of spacecraft-charging mitigation for the emission of a relativistic electron beam by a magnetospheric spacecraft is presented
  • The model is in good agreement with particle-in-cell simulations
  • The model predicts the long-time value of the spacecraft potential, indicating that a relativistic beam would be easily emitted

Free Access

Modeling the Dawn/Dusk Asymmetry of Field Line Resonances

  • Pages: 6443-6456
  • First Published: 05 July 2018
Key Points

  • Simulations of a magnetospheric waveguide that is asymmetric about noon are presented
  • Fast mode refraction causes asymmetries in compressional waves to develop, along with the FLRs they excite
  • FLRs are excited with larger amplitude at dawn compared to dusk

Open Access

Determining the Mode, Frequency, and Azimuthal Wave Number of ULF Waves During a HSS and Moderate Geomagnetic Storm

  • Pages: 6457-6477
  • First Published: 23 May 2018
Key Points

  • ULF wave power is systematically characterized as discrete or broadband, and the azimuthal wave number of discrete ULF waves is determined
  • Storm time discrete ULF waves can couple with the core radiation belt electron population via the drift resonance
  • Storm time ULF waves are the result of both external (Kelvin-Helmholtz) and internal (plasma instabilities) generation mechanisms

Free Access

The Composition of Plasma inside Geostationary Orbit Based on Van Allen Probes Observations

  • Pages: 6478-6493
  • First Published: 24 July 2018
Key Points

  • We performed a statistical survey of plasma pressure and the relative contributions from ions and electrons with different energies
  • H+ of hundreds of keV is the main contributor of plasma pressure that dominates inside plasmapause during geomagnetically quiet time
  • The energy flux of H+ with 0.1 < E < 40 keV and O+ with 10 < E < 50 keV increase significantly on the nightside during high AE intervals

Free Access

Survey of Thermal Plasma Composition in Saturn's Magnetosphere Using Time-of-Flight Data From Cassini/CAPS

  • Pages: 6494-6513
  • First Published: 31 July 2018
Key Points

  • Data show an enhancement in the ratio between ions with mass per charge equal to 2 and protons in the dusk sector
  • Enhancement is independent of the location of the moons with respect to the spacecraft and of season
  • Plasma stagnation point occurs at earlier local time than suggested by previous modeling

Free Access

Enhancement of the Jovian Magnetospheric Plasma Circulation Caused by the Change in Plasma Supply From the Satellite Io

  • Pages: 6514-6532
  • First Published: 01 August 2018
Key Points

  • Evolution of Io plasma torus radial distribution caused by volcanic eruptions in Io was observed in early 2015
  • Outward plasma transport from the Io plasma torus through 8 RJ from Jupiter enhanced for approximately 2 months
  • An inner magnetosphere plasma source is shown to affect large-scale mass/energy radial circulation in rotationally dominant magnetosphere

Free Access

The Role of the Parallel Electric Field in Electron-Scale Dissipation at Reconnecting Currents in the Magnetosheath

  • Pages: 6533-6547
  • First Published: 10 July 2018
Key Points

  • We observe ion diffusion regions and electron jets in the magnetosheath for multiple events
  • The dissipation due to the parallel electric field becomes more significant at increasing guide magnetic field
  • This may be associated with a dissipative electric field along the direction of the electron jet

Free Access

Kelvin-Helmholtz Instability in the Geotail Low-Latitude Boundary Layer

  • Pages: 6548-6561
  • First Published: 20 July 2018
Key Points

  • The low-latitude boundary layer stability problem in the geotail is solved numerically
  • This study relies on a cylindrical model of the geotail, with a smooth boundary, enwrapped by a helical solar wind flow
  • Unstable surface waves generated in the low- to medium-speed solar wind have the largest growth rate

Free Access

Longitudinal Dependence of Whistler Mode Electromagnetic Waves in the Earth's Inner Magnetosphere

  • Pages: 6562-6575
  • First Published: 25 July 2018
Key Points

  • Longitudinal dependence of whistler mode waves in the inner magnetosphere is investigated
  • Significant longitudinal dependence at frequencies between about 0.4 and 2 kHz is found inside the plasmasphere
  • The dependence is primarily observed on the nightside and is likely related to lightning activity

Open Access

The Largest Electron Differential Energy Flux Observed at Mars by the Mars Express Spacecraft, 2004–2016

  • Pages: 6576-6590
  • First Published: 23 July 2018
Key Points

  • Top 10 orbit-selected electron energy spectra from Mars are identified from MEx ASPERA-3 ELS between 2004 and 2016
  • The Mars and Venus dayside electron spectra are similar, and a discrete “auroral” spectrum from the nightside tail of Mars is also similar
  • No more energy than that supplied by the solar wind-planet interaction is required to produce discrete auroral spectrum from the nightside tail of Mars

Free Access

Test of Ion Cyclotron Resonance Instability Using Proton Distributions Obtained From Van Allen Probe-A Observations

  • Pages: 6591-6610
  • First Published: 06 August 2018
Key Points

  • Proton anisotropy is often larger immediately after EMIC wave onsets than the times before EMIC wave onsets and non-EMIC wave times
  • The amount of anisotropy increase is small; nevertheless, a large fraction of EMIC waves satisfies the ion cyclotron instability criterion
  • Proton distributions often remain near a marginal state, with anisotropies close to threshold values for ion cyclotron instability

Free Access

Radial Transport and Plasma Heating in Jupiter's Magnetodisc

  • Pages: 6611-6620
  • First Published: 25 July 2018
Key Points

  • Jupiter's observed radial ion temperature profile is found to be consistent with heating by turbulent magnetic field fluctuations
  • An advective outflow approach for turbulent heating is reasonable beyond L = 10 where transport is rapid and dominated by large-scale motion
  • The turbulent heating rate density has been recalculated, resulting in much higher values for the region between L = 10 and 20

Free Access

How Different Are the Solar Wind-Interplanetary Conditions and the Consequent Geomagnetic Activity During the Ascending and Early Descending Phases of the Solar Cycles 23 and 24?

  • Pages: 6621-6638
  • First Published: 24 July 2018
Key Points

  • Approximately 75% (34%) reduction in intense (moderate) storm occurrence rate during ascending and early descending phases of cycle 24 compared to cycle 23 is observed
  • Cycle 24 showed no significant difference during equinoctial months for intense storms; however, cycle 23 exhibited equinoctial asymmetry
  • ICMEs and/or their SH are identified to be the dominant drivers for intense storms during cycle 24 (∼89%) and cycle 23 (∼64)

Free Access

Solar Wind Interaction With the Martian Upper Atmosphere: Roles of the Cold Thermosphere and Hot Oxygen Corona

  • Pages: 6639-6654
  • First Published: 28 June 2018
Key Points

  • Despite the similar ion loss rate calculated from 1-D and 3-D atmospheres, the latter are required to adequately reproduce MAVEN observations
  • The hot oxygen corona plays an important role in protecting the Martian ionosphere/thermosphere from the solar wind erosion
  • The thermospheric oxygen atom is the primary neutral source for O+ ion escape during the relatively weak solar cycle 24

Free Access

Kinetic Alfvén Waves Excited in Two-Dimensional Magnetic Reconnection

  • Pages: 6655-6669
  • First Published: 24 July 2018
Key Points

  • Particle-in-cell simulations reveal consistent characteristics of Hall fields as KAW physics
  • The simulated KAW propagates out from the reconnection site along separatrices, parallel to the magnetic field lines
  • Changes of the current sheet thickness affect the ratio of Hall fields in the current layer near the X line

Free Access

Ultrawideband Rising-Tone Chorus Waves Observed Inside the Oscillating Plasmapause

  • Pages: 6670-6678
  • First Published: 18 August 2018
Key Points

  • The dawnside plasmapause is highly oscillating during a substorm activity
  • Ultrawideband rising-tone chorus waves (fLHR ~ 0.5fce) are observed in the high-density region inside the oscillating plasmapause
  • The ultrawideband rising-tone chorus waves can be generated through the nonlinear process

Technical Reports: Methods

Magnetospheric Physics

Free Access

Determining Plasmaspheric Densities from Observations of Plasmaspheric Hiss

  • Pages: 6679-6691
  • First Published: 13 August 2018
Key Points

  • Observations of plasmaspheric hiss are used to provide estimates of the electron plasma density inside of the plasmasphere
  • Once hiss-inferred densities are calibrated against densities from upper hybrid, they offer high levels of both accuracy and data coverage
  • This new method provides a useful tool for inferring accurate event-specific densities for the calculation of diffusion coefficients

Research Articles

Ionosphere and Upper Atmosphere

Free Access

ULF Electromagnetic Field in the Upper Ionosphere Excited by Lightning

  • Pages: 6692-6702
  • First Published: 17 July 2018
Key Points

  • Spectra of ULF electromagnetic field excited by atmospheric lightning stroke reveal spectral multiband structure in the upper ionosphere
  • Spectral peaks associated with the ionospheric Alfven resonator are evident at ≤400 km
  • An electric discharge with the charge moment 106 C m produces at 500 km a pulse with amplitudes about 4 mV/m and 4 nT

Free Access

Summer Noontime hmF2 Long-Term Trends Inferred From foF1 and foF2 Ionosonde Observations in Europe

  • Pages: 6703-6713
  • First Published: 15 July 2018
Key Points

  • A new method to retrieve hmF2 from foF1 and foF2 ionosonde observations has been proposed
  • Negative hmF2 trends manifest a latitudinal dependence reflecting the corresponding dependence in vertical plasma drifts
  • Long-term increase of the Northward thermospheric wind reflects a long-term decrease in auroral heating

Free Access

Onset Condition of Plasma Density Enhancements: A Case Study for the Effects of Meridional Wind During 17–18 August 2003

  • Pages: 6714-6726
  • First Published: 16 July 2018
Key Points

  • The plasma depletions and enhancements were observed by ROCSAT-1 at different local time before midnight on 17 August 2003
  • The EIA displayed different characteristics during 17–18 August 2003 from CHAMP, GRACE, and TEC map, respectively
  • The effects of the meridional wind on the formation of plasma blobs are discussed

Free Access

Diurnal Variation of Height-Distributed Nitric Oxide Radiative Emission During November 2004 Superstorm

  • Pages: 6727-6736
  • First Published: 30 June 2018
Key Points

  • The nitric oxide infrared radiative flux (NO IRF) responds differently to November 2004 geomagnetic storm during day and nighttime
  • Maximum variation in NO IRF is observed in the altitude below 190 km
  • Nighttime NO IRF enhancement with respect to quiet time is higher compared to daytime enhancement

Free Access

FIRI-2018, an Updated Empirical Model of the Lower Ionosphere

  • Pages: 6737-6751
  • First Published: 21 July 2018
Key Points

  • A dedicated empirical model of the nonauroral ionosphere is presented
  • The 80- to 90-km region is found to be the most difficult to model
  • The model is valid for altitudes above 60 km and densities over 106 electrons per cubic meter

Free Access

On the Solstice Maxima and Azimuth-Dependent Characteristics of the 150-km Echoes Observed Using the Equatorial Atmosphere Radar

  • Pages: 6752-6759
  • First Published: 23 July 2018
Key Points

  • Statistical results of 150-km echoes based on 10 years of EAR observations are presented
  • Occurrence and SNR of 150-km echoes are remarkably higher in solstices than in equinoxes
  • Multibeam observations show remarkable azimuthal-dependent characteristics of the echoes

Free Access

Investigating High-Latitude Energy Deposition Events Occurring During the 17 January 2005 Geomagnetic Storm

  • Pages: 6760-6775
  • First Published: 27 July 2018
Key Points

  • CHAMP mostly detected neutral density increases over polar flow channels (FCs)
  • Locally maximized Poynting flux (S||) within polar FCs implies electromagnetic energy deposition via FCs
  • The main region or one of the main regions of high-latitude S|| deposition was the polar cap (>78 degrees MLAT)

Free Access

Ionospheric Tidal Waves Observed From Global Ionosphere Maps: Analysis of Total Electron Content

  • Pages: 6776-6797
  • First Published: 15 July 2018
Key Points

  • The power of TEC variations increases with solar activity containing 85–97% (2–10%, 0.4–4.2%) contributing to westward (eastward and standing) waves
  • The TEC local time variation can be approximated by a sech2 solitary wave structure, which can produce DW1, SW2, and TW3 modes
  • The wave powers of wave-1, wave-2, wave-3, wave-4, and wave-5 peak structures observed at a fixed local time are identified

Free Access

Statistical Properties of Mesoscale Plasma Flows in the Nightside High-Latitude Ionosphere

  • Pages: 6798-6820
  • First Published: 25 July 2018
Key Points

  • Nine years of SuperDARN data were used to build an empirical model of mesoscale ionospheric plasma flows and their characteristics
  • Polar cap flows have postmidnight preference like polar cap arcs. Auroral oval flows have premidnight preference like substorm phenomena
  • Flow orientation dependence on IMF BY suggests that mesoscale flows have a tendency to be aligned with large-scale background convection

Free Access

Constraints on Scale Lengths of Equatorial Electrojet and Counter Electrojet Phenomena From the Indian Sector

  • Pages: 6821-6835
  • First Published: 04 July 2018
Key Points

  • Variability of EEJ at shorter separation (5°) is expectedly small and greater at 15° and 20° separation
  • Major variability in CEJ strength is observed at closely spaced sites (5°), both in individual events and in monthly averaged values
  • The longitudinal trend of eastward increase in EEJ and westward increase in CEJ strength is observed and relatable with DE3 structure

Free Access

Effects of St. Patrick's Day Geomagnetic Storm of March 2015 and of June 2015 on Low-Equatorial D Region Ionosphere

  • Pages: 6836-6850
  • First Published: 04 August 2018
Key Points

  • Strong amplitude anomalies on NWC signal were observed during evening terminator time associated with the 17 March 2015 and the 25 June 2015 storms
  • Stronger and longer duration signal amplitude anomalies occurred due to the March storm as compared to the June storm
  • Wavelet analysis shows signature of AGWs/TIDs along the NWC Allahabad path associated with these storms

Free Access

Ionospheric Specification and Space Weather Forecasting With an HF Beacon Network in the Peruvian Sector

  • Pages: 6851-6864
  • First Published: 14 August 2018
Key Points

  • An expanding network of HF beacon transmitters and receivers is being deployed in Peru for purposes of ionospheric specification
  • Pseudorange and Doppler shift data from network observed at two frequencies are inverted to give a regional specification of F region
  • In a campaign in January 2018 the beacon data help explain why ESF occurred on one evening but not the next

Free Access

Electron Energy Spectrum and Auroral Power Estimation From Incoherent Scatter Radar Measurements

  • Pages: 6865-6887
  • First Published: 23 July 2018
Key Points

  • Electron energy spectra are estimated from incoherent scatter radar measurements by integrating the electron continuity equation
  • Estimates of upward field-aligned current and auroral power are integrated from the spectrum estimates
  • The results are validated using simulations and comparisons with satellite measurements

Free Access

Influence of Solar Activity on Penetration of Traveling Planetary-Scale Waves From the Troposphere Into the Thermosphere

  • Pages: 6888-6903
  • First Published: 06 August 2018
Key Points

  • The influence of thermospheric effects of solar activity on traveling planetary-scale waves generated in the troposphere is simulated
  • Changes in the zonal wind and temperature caused by solar activity variations can modify spatial distributions of the planetary-scale waves
  • Solar activity variations can significantly (up to 100%) change amplitudes of waves coming to the thermosphere from below

Free Access

Triangulation and Coupling of Gigantic Jets Near the Lower Ionosphere Altitudes

  • Pages: 6904-6916
  • First Published: 14 August 2018
Key Points

  • The radar reflectivity profile showed that most of the GJs occurred around the overshooting tops of the troposphere
  • A gigantic jet with a diffuse region on the top extended above 100 km
  • The rebrightened streamers and brighter beads in the follow-up GJ indicate that there are long-lasting residual electron patches

Free Access

MAVEN Observations of the Response of Martian Ionosphere to the Interplanetary Coronal Mass Ejections of March 2015

  • Pages: 6917-6929
  • First Published: 21 July 2018
Key Points

  • In situ observations of the response of Martian ionosphere to two adjacent solar disturbances show significant differences in the topside ionosphere
  • During both these events, the ionospheric boundary (ionopause-like density gradient) was observed at lower altitudes, with much lower ionopause on 3 March
  • The comparison of the dayside profiles of O+/O urn:x-wiley:jgra:media:jgra54435:jgra54435-math-0003 ratio shows significant enhancement from ∼220 km only on 3 March, indicating preferential removal of O urn:x-wiley:jgra:media:jgra54435:jgra54435-math-0004

Free Access

Statistical Analysis of the Phase Velocity Distribution of Mesospheric and Ionospheric Waves Observed in Airglow Images Over a 16-Year Period: Comparison Between Rikubetsu and Shigaraki, Japan

  • Pages: 6930-6947
  • First Published: 08 August 2018
Key Points

  • Long-term analysis of the horizontal velocity of waves was made for airglow images at two different latitudes
  • Seasonal variation in the atmospheric gravity wave propagation direction was analyzed at both observation stations
  • Negative correlation was found between medium-scale traveling ionospheric disturbances and solar activity

Free Access

Poynting Flux in the Dayside Polar Cap Boundary Regions From DMSP F15 Satellite Measurements

  • Pages: 6948-6956
  • First Published: 04 August 2018
Key Points

  • Statistical distributions of Poynting flux in the cusp and LLBL regions are presented
  • Dependence of Poynting flux in the cusp on IMF conditions has been studied
  • Correlation of Poynting flux and particle precipitation energy flux in the cusp and LLBL has been investigated

Free Access

On the Role of Thermospheric Winds and Sporadic E Layers in the Formation and Evolution of Electrified MSTIDs in Geomagnetic Conjugate Regions

  • Pages: 6957-6980
  • First Published: 01 August 2018
Key Points

  • Presence of significant sporadic E activity in at least one of the hemisphere is found to be necessary for formation of EMSTIDs
  • EMSTIDs form even when thermospheric winds are not favorable in one hemisphere as hemisphere coupled U × B electric fields are important
  • Amplitudes of EMSTIDs often differ between the hemispheres based on the thermospheric meridional winds

Free Access

Statistical Characteristics of Polar Cap Patches Observed by RISR-C

  • Pages: 6981-6995
  • First Published: 06 August 2018
Key Points

  • An automatic algorithm was developed to identify polar cap patches observed by the Resolute Bay Incoherent Scatter Radar-Canada
  • A peak of patch occurrence is found between 14 and 19 magnetic local time at Resolute Bay
  • Typical plasma characteristics within the patches include high density, low electron temperature, and downward ion fluxes

Free Access

Long-Term Estimation of Diurnal Vertical E × B Drift Velocities Using C/NOFS and Ground-Based Magnetometer Observations

  • Pages: 6996-7010
  • First Published: 06 August 2018
Key Points

  • A relationship between C/NOFS vertical E x B drifts and magnetometer-derived EEJ during 2008-2014 has been developed
  • At least 80% of the differences between observed and derived E x B lie within -5 m/s and 5 m/s when validated with radar observations
  • The developed relationship is applicable during quiet and disturbed conditions

Ionosphere and Upper Atmosphere (SIA)

Free Access

Global Longitudinal Behavior of IRI Bottomside Profile Parameters From FORMOSAT-3/COSMIC Ionospheric Occultations

  • Pages: 7011-7028
  • First Published: 25 June 2018
Key Points

  • Longitudinal variability of B0 and B1 is investigated from FORMOSAT-3/COSMIC occultation profiles
  • Longitudinal wave-like feature in B0 indicates nonmigrating tidal influences with latitudinal anticorrelation connection with NmF2
  • Discrepancy among the bottomside submodels in IRI is noticed with the relatively improved performance in ABT-2009

Ionosphere and Upper Atmosphere

Open Access

Seasonal and Solar Cycle Variations of Thermally Excited 630.0 nm Emissions in the Polar Ionosphere

  • Pages: 7029-7039
  • First Published: 09 August 2018
Key Points

  • Thermal emissions maximize during equinox and solar maximum
  • Thermal emissions are dominated by high electron temperatures at solar minimum and by high electron densities at solar maximum
  • There is an equinoctial asymmetry in the occurrence of thermal emissions at Svalbard, which reverses with the solar cycle

Free Access

Global Responses of the Coupled Thermosphere and Ionosphere System to the August 2017 Great American Solar Eclipse

  • Pages: 7040-7050
  • First Published: 16 August 2018
Key Points

  • The solar eclipse caused thermospheric and ionospheric changes over the entire globe
  • Large-scale TADs were triggered by the eclipse and caused TEC enhancements over South America after the eclipse
  • Ionospheric plasma drifts strongly responded to the solar eclipse due to global wind and electrodynamics coupling

Free Access

IPIM Modeling of the Ionospheric F2 Layer Depletion at High Latitudes During a High-Speed Stream Event

  • Pages: 7051-7066
  • First Published: 27 July 2018
Key Points

  • A summertime HSS event is successfully modeled with IPIM when compared with EISCAT and SuperDARN radars, ionosondes, and CHAMP satellite data
  • The ionosphere F2 region is depleted as atomic oxygen density is reduced due to enhanced polar cap convection and neutral atmosphere heating
  • Electrodynamics can explain the short-term depletion of the ionosphere, while long-term effects are due to neutral atmosphere perturbations

Free Access

Recognition of Meteor Showers From the Heights of Ionization Trails

  • Pages: 7067-7076
  • First Published: 06 August 2018
Key Points

  • Short-time (one to few days) elevations of the median and quartiles of the meteor trail height distribution are observed by the Sodankylä meteor radar
  • Meteoroids belonging to the showers produce ionization trails at altitudes noticeably exceeding those of sporadic background
  • The effect is due to different properties of the sporadic meteoroids and shower members

Free Access

U-Shaped Spectrograms Registered by the DEMETER Satellite: Observational Features and Formation Mechanism

  • Pages: 7077-7088
  • First Published: 13 August 2018
Key Points

  • U-shaped spectrum registered in the equatorial region of the upper ionosphere during nighttime is formed by lightning-induced whistler waves
  • Latitudinal dependence of the upper cutoff frequency is determined by the peculiarities of oblique wave propagation and attenuation
  • The wave attenuation can be calculated along the trajectories found from the equations of geometrical optics that disregard collisions

Ionosphere and Upper Atmosphere

Free Access

Observations of Spatial Variations in O/N2 During an Auroral Substorm Using the Multichannel Downlooking Camera on the VISIONS Rocket

  • Pages: 7089-7105
  • First Published: 11 July 2018
Key Points

  • Wide field imaging of three auroral emissions are obtained from rocket observations at up to 750-km altitude
  • Wide field observations show a rapid decrease in O/N2 over a large area from Fort Yukon to Kaktovik
  • Observations of the vertical profile of O/N2 are consistent with presence of low-energy electrons

Free Access

Short-Term and Interannual Variations of Migrating Diurnal and Semidiurnal Tides in the Mesosphere and Lower Thermosphere

  • Pages: 7106-7123
  • First Published: 13 August 2018
Key Points

  • Short-term and intra-annual variability in DW1 and SW2 tidal modes estimated from TIDI and NAVGEM-HA are in good agreement
  • The biennial oscillations in DW1 and SW2 modes are systematically correlated with equatorial stratospheric quasi-biennial oscillation
  • There is no clear evidence of any solar cycle dependence or long-term trend in either DW1 or SW2 modes

Technical Reports: Methods

Ionosphere and Upper Atmosphere

Free Access

MENTAT: A New Wind Model for Earth's Thermosphere

  • Pages: 7124-7147
  • First Published: 13 July 2018
Key Points

  • MENTAT is a new F-region thermospheric neutral wind model
  • The winds include hourly, diurnal, seasonal, and decadal variability
  • The model includes solar flux (F10.7A) dependence