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Drivers of Upper Atmosphere Climate Change

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A Juno Era Model of the Jovian Magnetosphere

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Rocket Mission Conjures a Ghostly Noctilucent Cloud

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Open access

A Low Signal Detection of X‐Rays From Uranus

  •  31 March 2021

Key Points

  • A Chandra ACIS observation reveals a 10.3 sigma detection of X‐rays from Uranus with a probability of chance occurrence of 10−6–10−7

  • Uranus' X‐rays are concentrated between 0.6 and 1.1 keV, consistent with emission observed from Jupiter and Saturn

  • The X‐ray fluxes seem to exceed scattered solar emission alone, which may suggest X‐ray aurora and/or X‐ray fluorescence from the rings

Global Hybrid Simulations of Interaction Between Interplanetary Rotational Discontinuity and Bow Shock/Magnetosphere: Can Ion‐Scale Magnetic Reconnection be Driven by Rotational Discontinuity Downstream of Quasi‐Parallel Shock?

  •  27 March 2021

Key Points

  • Magnetosheath reconnection is driven by interaction of the interplanetary rotational discontinuity (RD) with the bow shock/magnetosheath

  • The existent and structure of reconnection depending on the solar wind Alfvén Mach number and the propagation direction of the RD

  • Large‐amplitude low‐frequency waves downstream of the Q‐|| shock play an important role in triggering reconnection inside the RD

Van Allen Probe Observations of Disappearance, Recovery and Patchiness of Plasmaspheric Hiss Following Two Consecutive Interplanetary Shocks: First Results

  •  24 March 2021

Key Points

  • First report on plasmaspheric hiss variability in response to two successive interplanetary shocks observed by the Van Allen probes

  • Both the shocks triggered substorms that played important roles in the variability of plasmaspheric hiss

  • Based on detailed electron phase space density and wave growth rate analyses, the observed hiss variations are explained

New Measurement of the Vertical Atmospheric Density Profile From Occultations of the Crab Nebula With X‐Ray Astronomy Satellites Suzaku and Hitomi

  •  24 March 2021

Key Points

  • Combined O and N densities at altitudes 70–200 km are measured with X‐ray astronomy satellites Suzaku and Hitomi

  • The vertical density profile agrees with a prediction of the NRL model, except for altitudes 70–110 km showing significant density deficit

  • The density deficit could be due to either long‐term radiative cooling of the upper atmosphere or imperfect modeling

Open access

Tailward Flows in the Vicinity of Fast Earthward Flows

  •  24 March 2021

Key Points

  • Tailward flows around BBFs (TWABs) can frequently be observed. They have high |V| and plasma properties similar to bursty bulk flows (BBFs) compared to the general tailward flows

  • It is more common to observe a TWAB succeeding than preceding a BBF. However, there is no distinctive difference between them

  • TWABs are likely the “freshly” rebounded BBFs. They may represent the early stage of the evolution of tailward flows in the plasma sheet

Open access

ULF Wave Driven Radial Diffusion During Geomagnetic Storms: A Statistical Analysis of Van Allen Probes Observations

  •  24 March 2021

Key Points

  • Radial diffusion is enhanced from the late initial storm phase and peaks in the late main phase

  • Enhancements are due to external driving and internal sources of Ultra Low Frequency wave power

  • Storm time magnetic field diffusion coefficients are underestimated by Ozeke et al. (2014)

Energy Dissipation via Magnetic Reconnection Within the Coherent Structures of the Magnetosheath Turbulence

  •  23 March 2021

Key Points

  • A thin electron current layer is embedded within a broader ion‐scale current layer in the trailing part of magnetosheath magnetic peak

  • Direct evidence of magnetic reconnection is found inside the thin electron current layer of magnetic peak

  • Electrons are significantly heated in two regions of peaks: reconnecting current layer and trailing edges, in different mechanisms

Data‐Driven Simulation of Rapid Flux Enhancement of Energetic Electrons With an Upper‐Band Whistler Burst

  •  23 March 2021

Key Points

  • The data‐driven simulation of rapid flux enhancement has been performed using plasma/particle and wave data obtained by Arase

  • The simulation results reproduce the observed temporal variations of energetic electron flux distributions

  • The nonlinear phase trapping contributes to the flux enhancement of electrons above 20 keV

free access

Issue Information

  •  22 March 2021

From Bow Waves to Traveling Atmospheric Disturbances: Thermospheric Perturbations Along Solar Eclipse Trajectory

  •  22 March 2021

Key Points

  • Thermospheric perturbations evolve from fast bow waves to slow large‐scale TADs as eclipse progresses

  • Eclipse trajectory affects global patterns of eclipse‐induced thermospheric disturbances, which depends on season and latitude

more >

Parker Solar Probe FIELDS instrument charging in the near Sun environment: Part II – Comparison of In‐Flight Data and Modeling Results

  •  5 April 2021

Key Points

  • We predict the floating potentials of the Parker Solar Probe FIELDS antennas.

  • We analyze the model antenna I‐V curves to determine the optimal current and voltage biases for maximum sensor sensitivity.

  • We compare the theoretical predictions with mission flight data and find qualitative agreement, but some quantitative differences.

Energy transfer between hot protons and electromagnetic ion cyclotron waves in compressional Pc5 ultra‐low frequency waves

  •  5 April 2021

Key Points

  • Electromagnetic ion cyclotron wave enhancements were detected in a compressional ultra‐low frequency wave.

  • Troughs of magnetic field intensity of the ultra‐low frequency wave are preferential locations for the cyclotron resonant energy transfer.

  • Due to compressional ultra‐low frequency wave, regions of the cyclotron resonant energy transfer can be narrow in magnetic local time.

PATCH:Particle Arrival Time Correlation for Heliophysics

  •  5 April 2021

Key Points

  • We develop a new algorithm, PATCH, to quantify wave‐particle energy transfer onboard spacecraft.

  • We qualitatively assess how PATCH can resolve the velocity‐space signature of ion Landau damping.

  • We quantify the error of the PATCH method as the particle count rate varies.

Open access

Seven decades of neutron monitors (1951 – 2019): Overview and evaluation of data sources

  •  5 April 2021

Key Points

  • The quality of hourly data of almost 300 datasets for 147 neutron monitors was assessed.

  • Individual neutron monitor datasets across multiple sources were cross‐compared and the best source(s) for each monitor were determined.

  • An up‐to‐date assessment of all available neutron monitor data was conducted.

Laboratory study of antenna signals generated by dust impacts on spacecraft

  •  5 April 2021

Key Points

  • A simple model based on induced charging is shown to reproduce dust impact signals detected by antenna instruments.

  • Key parameters of the dust impact plasma are obtained from fitting the model to data from laboratory measurements.

  • The presented model is applicable to a range of space missions with antenna instruments.

Electron Trapping in Magnetic Mirror Structures at the edge of Magnetopause Flux Ropes

  •  5 April 2021

Key Points

  • MMS observations show magnetic mirror structures on the edge of magnetopause flux ropes

  • Mirror structures trap electrons and have extended 3D structure

  • Evolution of mirror structures could facilitate particle acceleration

Study of a quasi‐27‐day wave in the MLT region during recurrent geomagnetic storms in autumn 2018

  •  4 April 2021

Key Points

  • A strong quasi‐27‐day wave (Q27DW) is observed in MLT zonal winds over Beijing during recurrent geomagnetic storms.

  • Solar radiation and seasonal variation are not the main reason for generating the observed Q27DW.

  • It is very likely that the observed Q27DW is excited due to the effect of the recurrent geomagnetic storms.

Open access

Bursty ion escape fluxes at Mars

  •  4 April 2021

Key Points

  • Fluxes of oxygen ions escaping the Martianionosphere with values exceeding their median values by more than a factor of 100 are observed.

  • Burst fluxes of the high‐energy oxygen ions are often related with high values of the simultaneously measured fluxes of the solar wind.

  • High fluxes of the low‐energy oxygen ions are often related with over dense ion clouds observed in the top‐side ionosphere of Mars.

The Cusp Plasma Imaging Detector (CuPID) CubeSat Observatory: Mission Overview

  •  4 April 2021

Key Points

  • The CuPID CubeSat Observatory is a small satellite built to study soft X‐rays in space

  • CuPID is a pioneering wide field‐of‐view soft X‐ray imager in orbit

  • CuPID studies solar wind‐magnetosphere coupling and magnetopause reconnection

The TEC enhancement before seismic events is an artifact

  •  3 April 2021

Key Points

  • VTEC residuals for several stations depend highly on selected time window

  • VTEC residuals for station LYAR vary significantly for choice of polynomial fit

  • TEC enhancement as an earthquake precursor is an artifact

more >
free access

NRLMSISE‐00 empirical model of the atmosphere: Statistical comparisons and scientific issues

What is a geomagnetic storm?

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Solar wind spatial scales in and comparisons of hourly Wind and ACE plasma and magnetic field data

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Modeling the dynamics of the inner magnetosphere during strong geomagnetic storms

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Magnetopause location under extreme solar wind conditions

Magnetic loop behind an interplanetary shock: Voyager, Helios, and IMP 8 observations

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Geospace Environmental Modeling (GEM) Magnetic Reconnection Challenge

The ionospheric disturbance dynamo

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A catalog of white light coronal mass ejections observed by the SOHO spacecraft

Collision frequency of artificial satellites: The creation of a debris belt

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free access

Possible modification of the cooling index of interstellar helium pickup ions by electron impact ionization in the inner heliosphere

Key Points

  • The influence of electron impact ionization is negligible
  • Its influence is also small even in the compressions

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Interhourly variability index of geomagnetic activity and its use in deriving the long‐term variation of solar wind speed

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Effect of the altitudinal variation of the gravitational acceleration on the thermosphere simulation

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Correcting the Dst index: Consequences for absolute level and correlations

Open access

A Low Signal Detection of X‐Rays From Uranus

Key Points

  • A Chandra ACIS observation reveals a 10.3 sigma detection of X‐rays from Uranus with a probability of chance occurrence of 10−6–10−7

  • Uranus' X‐rays are concentrated between 0.6 and 1.1 keV, consistent with emission observed from Jupiter and Saturn

  • The X‐ray fluxes seem to exceed scattered solar emission alone, which may suggest X‐ray aurora and/or X‐ray fluorescence from the rings

free access

Reexamination of the coronal index of solar activity

free access

Earth's Van Allen Radiation Belts: From Discovery to the Van Allen Probes Era

Key Points

  • A brief historical background on the discovery of the Van Allen radiation belts and their response to solar activity is introduced
  • Recent advances in understanding mechanisms responsible for radiation belt electron acceleration, transport, and loss are reviewed
  • Outstanding challenges for developing future radiation belt models are summarized

Plain Language Summary

Discovery of the Earth's Van Allen radiation belts by instruments flown on Explorer 1 in 1958 was the first major discovery of the Space Age. The dynamic properties of trapped outer zone electrons and the outer boundary of the inner zone proton population, along with source populations, have recently been studied in great detail by instruments on National Aeronautics and Space Administration's Van Allen Probes spacecraft, as well as other data sources like operational spacecraft designed for navigation and terrestrial weather forecasting. The vulnerability of the myriad of spacecraft that is strongly affected by space weather disruptions, as compared to 1958, has motivated the radiation belt community to develop essential improved models for forecasting the space environment we will inhabit in the 21st century and evaluate its impacts on our technological society. In this paper, we provide a review on historical background and recent advances in understanding and modeling acceleration, transport, and loss processes of energetic particles in the Earth's Van Allen radiation belts, followed by outstanding challenges for developing future radiation belt models. The findings on the fundamental physics of the Van Allen radiation belts potentially provide insights into understanding energetic particle dynamics at other magnetized planets in the solar system, exoplanets throughout the universe, as well as in astrophysical and laboratory plasmas. Given the potential Space Weather impact of radiation belt variability on technological systems, these new radiation belt models are expected to play a critical role in our technological society in the future much as meteorological models do today.

free access

NRLMSISE‐00 empirical model of the atmosphere: Statistical comparisons and scientific issues

free access

Wavelet‐based index of magnetic storm activity

Open access

System Identification and Data‐Driven Forecasting of AE Index and Prediction Uncertainty Analysis Using a New Cloud‐NARX Model

Key Points

  • A novel cloud‐NARX model is presented for modeling and forecasting of AE index with solar wind parameters as input variables
  • The cloud‐NARX model generates 1‐hr‐ahead prediction of AE index with a confidence interval
  • The uncertainty of model structure, parameters, and predictions can be quantified by the cloud‐NARX model, and the model robustness can be improved

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