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New understanding of the solar eclipse effects on geospace: The 21 August 2017 Solar Eclipse

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Last updated:
8 February 2018
A solar eclipse generates dramatic changes throughout the Earth's geospace due to the fast reduction and recovery of solar EUV irradiation. It modifies local and global energetics, dynamics, and the ionospheric ionization supply, leading to substantial changes in the coupled magnetosphere-ionosphere-thermosphere-mesosphere (geospace) system. It is an idealized "active experiment" to explore the impulse-response dynamics of geospace and to address some of the fundamental scientific questions in geospace. The 21 August 2017 solar eclipse provides an unprecedented opportunity for this because of the large amount of observational data obtained during the eclipse with recent major advances in sensitivity, spatial/temporal resolution, and global coverage of measurements, as well as the development of sophisticated geospace modeling tools. This special issue aims at quantifying the new understanding of the solar eclipse effects on geospace. This new understanding includes, but not limited to, global ionospheric and thermospheric changes, responses of neutral composition, temperature, and winds, traveling ionospheric disturbances, geomagnetic and electric field disturbances, localized and meso-scale structures,  lower ionospheric changes and associated impacts on VLF/LF/HF radio propagation.

The C/NOFS Mission

Published:
1 September 2009
O. de La Beaujardi
The Air Force's Communication/Navigation Outage Forecasting System (C/NOFS) satellite was launched in April 2008 into a 13\u00C2\u00B0 inclination low Earth orbit to study the equatorial ionosphere as well as spread\u00E2\u0080\u0090F and associated scintillation. C/NOFS is the first satellite to carry a comprehensive set of sensors specifically designed to monitor and forecast ionospheric conditions. Instruments measure electric fields, plasma characteristics, neutral winds, and the strength of scintillation\u00E2\u0080\u0090producing irregularities. Models use the spacecraft observations and combine them with ground\u00E2\u0080\u0090based and other satellite data to forecast the ion density and determine where ionospheric irregularities are likely to produce scintillation.

Saturn's Magnetosphere: First Results From Cassini

Published:
1 October 2005
T. Gombosi
Cassini/Huygens started orbiting Saturn on 1 July 2004, and some of the initial results are fascinating. This special section summarizes some of the new discoveries made with the particles and instruments onboard the Cassini orbiter. Among the interesting new discoveries are a new radiation belt, the tremendous amount of water in the magnetosphere, and the absence of expected nitrogen. This special collection is just the tip of the iceberg, and many more results and discoveries are still to come. Stay tuned.

First results from NASA's Magnetospheric Multiscale (MMS) Mission

Last updated:
5 February 2018
The Magnetospheric Multiscale (MMS) mission has been performing particle and electromagnetic field measurements in the near-Earth environment since its launch in March 2015. Thanks to data with unprecedented time resolution on four identical spacecraft in a close tetrahedron configuration (down to 10 km), MMS science goals are to probe and understand the electron-scale physics involved in the magnetic reconnection process. This collection provides a selection of key results obtained during the first phase of the mission at the dayside magnetopause. It includes new observations of the geometry and variability of the reconnection process, the detailed dynamics of particles, fields and waves in the vicinity of the reconnection region, the observation of small-scale signatures at current sheets formed in the magnetosheath, in Kevlin-Helmholtz vortices, or flux transfer events, as well as other small-scale features which are by-products of magnetic reconnection or not. These results open a new window for our understanding of magnetic reconnection in space, with direct and numerous implications for astrophysical and laboratory plasmas.

Large Geomagnetic Storms of Solar Cycle 23

Published:
1 March 2008

The MaCWAVE-MIDAS Program to Study the Polar Summer Mesosphere

Published:
1 April 2005
R. Goldberg
Gravity waves provide the dominant forcing of the mesosphere and lower thermosphere (MLT) via transports of energy and momentum from lower altitudes and their deposition arising from wave dissipation. The quantitative aspects of this forcing are poorly understood at present because of the diversity of wave sources, the complexity of their interactions and instabilities, and the challenges to quantifying such small-scale dynamics. The MaCWAVE-MIDAS collaborative rocket and ground-based measurements were performed in Northern Norway to address these issues under summer conditions. New results include demonstration of surprising MLT gravity wave and turbulence activity, lower thermospheric shears, plasma-neutral coupling, interannual variability, and inter-hemispheric connections.

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Featured Special Collection

A Census of Atmospheric Variability from Seconds to Decades 

The atmosphere varies naturally on all length scales from millimeters to thousands of kilometers, and on all time scales from seconds to decades and longer.  This special collection of Geophysical Research Letters synthesizes and summarizes that variability through a phenomenological census.  The collection brings together some of the most influential and definitive papers to have been published in this journal in recent years.  The topics covered include turbulence on time scales of seconds and minutes, gravity waves on time scales of hours, weather systems on time scales of days, atmospheric blocking on time scales of weeks, the Madden–Julian Oscillation on time scales of months, the Quasi-Biennial Oscillation and El Niño–Southern Oscillation on time scales of years, and the North Atlantic, Arctic, Antarctic, Pacific Decadal, and Atlantic Multi-decadal Oscillations on time scales of decades.  The collection is accompanied by a Commentary article, which provides an authoritative, concise, and accessible point of reference for the most important modes of atmospheric variability.

A Census of Atmospheric Variability from Seconds to Decades