Journal of Geophysical Research: Space Physics

Commentary— A series of studies during the last decade have shown clear evidence of solar wind‐related periodicities in the variations of different parameters of the lower (troposphere/stratosphere) and upper (thermosphere/ionosphere) atmosphere, over the high‐latitude regions. This commentary is prompted by a recent study of the fluctuations of neutral density, winds, and temperatures near 90 km, which provides evidence of such a solar wind‐related response in the mesosphere as well. It i Continue reading >

Research Spotlight— Japan’s Hisaki satellite takes measurements of faint oxygen emissions from Io. Lakes of lava and hundreds of volcanoes dot the surface of Jupiter’s moon Io, some spewing lava dozens of kilometers into the air. Only slightly larger than our own planet’s moon, Io is the most volcanically active place in the solar system. Its thin atmosphere is made up largely of sulfur oxides. As Io orbits, neutral gas particles escape its atmosphere Continue reading >

Research Spotlight— High-speed particles cause indentations in the magnetopause to form “throat auroras.” Roughly every other day at the Arctic Yellow River Station in Svalbard, Norway, astronomers observe a mysterious feature of the aurora borealis, the glowing ring of energetic particles around Earth’s magnetic North Pole. One edge of the aurora briefly erupts in a fanning starburst of light, which can span up to 6,400 kilometers, or 3 times Earth&rs Continue reading >

Editors' Highlight— A new empirical model of energetic electrons from Van Allen Probes data includes pitch angle analysis, revealing insights about radiation belt energization and loss processes. The two satellites of NASA’s Van Allen Probes mission have provided a wealth of data suitable for statistical analysis to build up data-based empirical models of the charged particles near Earth. Zhao et al. [2018] provide such a model of the energetic electrons in the radiation be Continue reading >

Editors' Highlight— Pancaking and erosion can explain a lot of the structural change in magnetic flux ropes as they fly evolve during their supersonic flight through the inner solar system. The Sun regularly launches material and magnetism into the solar system, and occasionally the structure of these disturbances is neatly coiled into a magnetic flux rope. These are not static structures, and definitely not stationary—moving at supersonic speeds of hundreds of kilometers per second, Continue reading >

Research Spotlight— A new study reveals that low-frequency electromagnetic waves accompany intense heating events at low altitudes. On 17 December 1971, scientists observed a bizarre new phenomenon in the outermost region of Earth’s atmosphere, where the planet’s magnetic fieldorchestrates the flow of charged particles and produces such phenomena as auroras. In the midst of a massive geomagnetic storm induced by a surge of solar radiation, satellites detecte Continue reading >

Editors' Vox— A recent celebration of the 60th anniversary of the launch of Explorer 1 reflected on the incredible progress and scientific insights from this and subsequent space missions. The International Geophysical Year (IGY) of 1957-58 was a watershed period in the history of science. Together with the profound understanding of Earth’s atmosphere, oceans, and polar regions (especially the Antarctic) that emerged from the IGY, this worldwide program also gave birth to the ‘ Continue reading >

Editors' Highlight— Most fast coronal mass ejections will be decelerated into ambient solar wind quickly in the inner heliosphere, but some of them continue the deceleration with an even larger amplitude beyond 1 AU. Interplanetary coronal mass ejections (ICMEs) are the major drivers of severe space weather near Earth and other planets. Freiherr von Forstner et al. [2018] provide multi-spacecraft observations of a set of ICMEs, associated shocks and resultant decreases of the flu Continue reading >

Editors' Highlight— Imperfect knowledge of high-latitude forcing of the coupled ionosphere-theremosphere system translates into uncertainty in the low-latitude and midlatitude response to a geomagnetic storm. Geomagnetic storms produce large changes in the Earth’s ionosphere and thermosphere that can impact communications, satellite orbits, and navigation systems, as well as electric power grids. The capability of numerical models to reproduce the ionospheric disturbance during a geo Continue reading >

Blog— The elusive “footprint” of Jupiter’s moon Callisto has been spotted for the first time near the south pole of the giant planet, according to a new study. Such footprints – bright patches of ultraviolet light – are created by the four largest moons of Jupiter as the planet’s powerful magnetic field sweeps past them. The moons pluck the invisible magnetic field lines of Jupiter like strings on a guitar, sending high-energy electrons flowing along the Continue reading >

Research Spotlight—Scientists measure how the aurora affects winds in the upper atmosphere.When a dazzling aurora lights up the polar skies, it’s a sign of a disturbance in Earth’s magnetosphere, the magnetic shield that protects our planet from solar radiation. The aurora borealis and aurora australis—also known as the northern and southern lights—occur when solar particles penetrate Earth’s magnetic field and collide with oxygen and nitrogen, Continue reading >

Editors' Highlight—When it comes to Saturn’s space environment, summer wins over winter in controlling the periodic flows of electrically charged particles and magnetic fields.In 2017, the Cassini spacecraft ended its orbital tour of Saturn, its moons, and its space environment. At the end, as it came closer and closer to Saturn for its final plunge into the atmosphere, it collected a unique set of data that is just beginning to analyzed for new insights about how this planet works. Carbary et Continue reading >

Editors' Highlight—A comprehensive look at how the solar wind is diverted around Mars, including the relative strength of the three biggest forces at work in this region.Mars, without a strong internal dipole magnetic field, is a place where the supersonic solar wind directly contacts the planet’s upper atmosphere. Using a large set of data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, Halekas et al. [2017] examine some properties of the solar wind in that interaction region, Continue reading >

Editors' Highlight—Most boundaries in space are governed by magnetic fields, but not far behind the Earth, where the field change across the magnetopause plays very little role in the pressure balance relationship.Space physicists like to focus on regional boundaries that are magnetized. Artemyev et al. [2017] examine a boundary where magnetic fields play only a marginal role: the far-downtail magnetopause. At distances from 50 to 200 RE downtail, they find that the pressure balance is dominate Continue reading >

Research Spotlight—A new study uses satellite data to examine a worldwide system of electric currents in greater detail than ever before.The fact that planet Earth is essentially a giant magnet is not a great secret: A compass works because either end of its magnetized needle is constantly being drawn toward the North and South poles. Scientists believe that the Earth’s magnetization is caused by a sea of liquid metal flowing past its solid iron core, creating electric currents and, in turn, ma Continue reading >

Editors' Vox—We are approaching the 40-year anniversary of the two Voyager spacecraft making their 1979 flybys of the planet Jupiter. Jupiter’s magnetosphere is big. The satellites were moving fast, and each one only spent a few days passing through the magnetic bubble around this planet so two flybys does not seem like much of an opportunity to gather data. But the plasma science instruments on the spacecraft were high quality sensors that led to numerous p Continue reading >

Editors' Vox—We are approaching the 40-year anniversary of the two Voyager spacecraft making their 1979 flybys of the planet Jupiter. Jupiter’s magnetosphere is big. The satellites were moving fast, and each one only spent a few days passing through the magnetic bubble around this planet so two flybys does not seem like much of an opportunity to gather data. But the plasma science instruments on the spacecraft were high quality sensors that led to numerous papers on the magnetospheric structure Continue reading >

Editor’s Highlight— This paper presents an analysis of a 3D fully-kinetic simulation of Kelvin-Helmholz vortices along Earth’s magnetopause. The results of the simulation are compared to observations from NASA's Magnetospheric Multiscale (MMS) mission. The authors present evidence of secondary, turbulent reconnection, a preference for reconnection on one side of the mixing layer between the two plasmas, and formation of a new mixing layer with strong electron parallel heating. This work shows h Continue reading >

Editor’s Highlight— Solar flare emission at X-ray and extreme ultraviolet energies cause substantial enhancements in the electron concentration in Earth’s lower ionosphere (about 60-90 km altitude). Flares often show quasi-period emission (QPPs) with periods ranging minutes to tens of minutes. This paper shows, for the first time, that the lower ionosphere responds to these QPPs. The authors measure the incoming solar radiation with satellite data at geostationary altitude. The impact of the QP Continue reading >

Editor’s Highlight—A mechanism of mid-latitude noontime foE long-term variations inferred from European observationsThe study of long-term trends and in long-term variations in thermospheric and ionospheric parameters are currently very popular, and conclusions of these studies differ substantially. The authors of this paper demonstrate that the main source of long-term variations of ionospheric parameters in critical frequencies of E layer is long-term variations in solar activity. From Eos.or Continue reading >