Observations of astronomical sources provide information that can significantly enhance the utility of auroral data for scientific studies. This report presents results obtained by using Jupiter for field cross calibration of four multispectral auroral meridian scanning photometers during the 2011–2015 Northern Hemisphere winters. Seasonal average optical field-of-view and local orientation estimates are obtained with uncertainties of 0.01 and 0.1°, respectively. Estimates of absolute sensitivity are repeatable to roughly 5 % from one month to the next, while the relative response between different wavelength channels is stable to better than 1 %. Astronomical field calibrations and darkroom calibration differences are on the order of 10 %. Atmospheric variability is the primary source of uncertainty; this may be reduced with complementary data from co-located instruments.

First-light measurements from the Canadian face of the Resolute Bay Incoherent Scatter Radar (RISR-C) were taken in August of 2015. Data were taken for roughly 25 h on both RISR-C and the North face of the Resolute Bay radar (RISR-N) in an 11-beam World Day mode. Overall, the measurements from the RISR-C radar are of high quality and consistent with results from the RISR-N radar. During the 25 h period analyzed in this study, the ionosphere responded to changes in orientation of the interplanetary magnetic field . During one particular event, a change from Bz negative to positive and By positive to negative caused the antisunward flow to stall, and a strong dawn-to-dusk flow, with decreased electron density and increased ion temperature, replaced it in the RISR-C field of view. Overall, it is clear that measurements from the RISR-C radar will complement and greatly expand the scope of ionospheric polar cap measurements.

The structure and dynamics of the Martian ionosphere are believed to be strongly dependent on the nature, magnitude, and topology of its magnetic field, and whether or not Mars has an intrinsic magnetic field. Due to the weak magnetic field on Mars, the Martian ionosphere interacts directly with the solar wind, resulting in significant outflows of keV ion beams and lower-energy "pick-up" ions. We discuss the planned study of ion drifts and solar wind interactions in the Martian ionosphere using the Planet-B Thermal Plasma Analyzer.

The Freja Cold Plasma Analyzer (CPA) is a hemispherical electrostatic analyzer which forms 2-D, energy/arrival angle images of low-energy (< 200 eV) particle distribution functions. In addition to its 2-D imaging capability, the CPA is unique in that its sensor head is displaced from the spacecraft on a 2 m boom which allows control of the probe-to-plasma potential, thereby compensating for variations in spacecraft potential. Furthermore, the detector biases can be set to measure either positively or negatively charged particle species. This study emphasizes temperature measurements of the core electron population (∼ 1 eV) which are difficult to make since, among other reasons, they are affected by spacecraft charging and are susceptible to contamination from photoelectrons and finite gyroradius effects. We demonstrate that the CPA sensor does detect the core population by showing that probe-to-plasma potential changes of only a fraction of 1 V cause large changes in the electron flux measured at the detector anode. The relation between detector current and sensor bias comprises a modified Langmuir curve, which in contrast to standard Langmuir measurements results from a single particle species only (electrons) and from particles which are restricted in energy (0-70 eV) and in arrival angle to within ±4° of the detector plane. The modified Langmuir curve can be compared to a standard Langmuir curve formed by measuring current onto the external skin of the sensor, which contains contributions from both electrons and ions at all energies and over a wide angular acceptance. Somewhat surprisingly, the two methods agree fairly well in the sunlit portion of a sample orbit, i.e. in the presence of a background photoelectron population, but differ by up to a factor of two in the dark part of the orbit.

This chapter contains sections titled: Introduction Instrument Response Plasma Parameter Measurements Summary and Discussions

Coordinated observations of ionospheric variability near the geomagnetic pole using the Resolute Bay Incoherent Scatter Radar (RISR‐N), Super Dual Auroral Radar Network (SuperDARN) High Frequency (HF) radars, and all‐sky imagers have clarified the relative contribution of structuring mechanisms operating on polar plasma patches. From the multipoint RISR‐N observations, a three dimensional image can be constructed of the plasma parameters. The colocated coherent echoes from the SuperDARN radars provide information on field aligned irregularities, and from all‐sky imagers located in Resolute Bay, Canada and Qaanaaq, Greenland, information is obtained on the emission brightness at different wavelengths. A good correlation is found between the location of the coherent, incoherent and optical signals of patches. From the SuperDARN radar data it is evident that plasma irregularities seem to be present throughout the region of enhanced electron density. The patches are observed to be formed in the cusp region due to bursty flux transfer events and are then transported across the polar cap. During the time period of about 10 minutes when a patch drifted through the RISR‐N field of view, the patch seemed to undergo significant deformation in all three spatial dimensions, with density fluctuations of about 10% and spatial variations leading to stretching and tilting of the patch. The findings show that plasma structuring can likely occur within polar cap patches, which support previous suggestions that a patch is highly variable as it drifts across the polar cap, with a faster spread of irregularities throughout the patch as a result.

On the nightside, the bright proton aurora forms a several degrees in latitude band of diffuse aurora near the equatorward boundary of the electron auroral oval. The precipitation is due to strong pitch angle diffusion that is thought to be the result of nonadiabatic motion of sub-keV to tens of keV central plasma sheet (CPS) protons as they traverse the tightly curved magnetic field topology in the vicinity of the neutral sheet. In this paper, we provide an overview of the relationship between the spatiotemp oral evolution of the proton aurora and magneto spheric dynamics. We focus on the equatorward boundary of the proton aurora, the latitude of which has been shown to be strongly correlated with magnetic field line stretching in the inner CPS, and provide the first-ever identification of the position of the ion isotropy boundary relative to equatorial magnetospheric spacecraft.

Based on observations by a high‐resolution narrow field‐of‐view CCD camera, we found small‐scale (5–25 km) finger‐like structures at the western boundary of auroral patches in images obtained at Gillam (geomagnetic latitude: 65.5°N), Canada, in January 2008. Since shear motion was not observed along the boundary of the patches, we suggest that these structures are formed by macroscopic Rayleigh‐Taylor type plasma instability arising in the magnetospheric equatorial plane from the force balancing of the (eastward) magnetic tension force and the (westward) pressure gradient force.

We show four auroral initial brightening events at substorm onsets focusing on fine structures and their longitudinal dynamics, which were observed by all-sky TV cameras (30-Hz sampling) on January 2008, in Canada. For two initial brightenings started in the field of views of the cameras, we found that they started at longitudinal segments with a size of less than ~30–60 km. One brightening expanded with wavy structures and the other expanded as a straight arc. Although the two events had different structures, both brightening auroras expanded with an average speed of ~20 km/s in the first 10 s, and ~10 km/s in the following 10 s. The other two events show that brightening auroras developed with periodic structures, with longitudinal wavelengths of ~100–200 km. Assuming that the brightening auroras are mapped to the physical processes occurring in the plasma sheet, we found that the scale size (30–60 km) and the expanding speed (20 km/s) of brightening auroras correspond to the order of ion gyro radii (~500–1400 km) and Alfvén speed or fast ion-flow speed (~400 km/s), respectively, in the plasma sheet.

We present simultaneous THEMIS-ground observations of longitudinal (eastward) extension of a substorm initial-brightening arc at Gillam (magnetic latitude: 65.6°) at 08:13 UT on 10 January 2008. The speed of the eastward arc extension was ~2.7 km/s. The extension took place very close to the footprints of the longitudinally separated THEMIS E and D satellites at ~12 RE. The THEMIS satellites observed field dipolarization, weak earthward flow, and pressure increase, which propagated eastward from E to D at a speed of ~50 km/s. The THEMIS A satellite, located at 1.6 RE earthward of THEMIS E, observed fluctuating magnetic field during and after the dipolarization. The THEMIS E/D observations suggest that the longitudinal extension of the brightening arc at substorm onset is caused by earthward flow braking processes which produce field dipolarization and pressure increase propagating in longitude in the near-earth plasma sheet.

We present ground‐based and in situ observations from March 13, 2007. The THEMIS satellites were in the evening sector conjugate to THEMIS ground‐based imagers. At ∼0507 UT there was an optical onset on inner CPS field lines. This involved near‐simultaneous brightening of 1 MLT hour longitudinal segment of the onset arc. The part of the arc that brightened was that closest to the equatorward boundary of the diffuse (proton) aurora. Within one minute, a dipolarization front moved across four THEMIS satellites. Based on their locations, the order in which they detected the dipolarization front, and the auroral evolution, we assert that the expansion phase began earthward of the four satellites and evolved radially outwards. We conclude that this onset occurred in an azimuthally localized region of highly stretched field lines.

The comprehensive THEMIS approach to solving the substorm problem calls for monitoring the nightside auroral oval with low-cost, robust white-light imagers and magnetometers that can deliver high time resolution data (0.33 and 2 Hz, respectively). A network of 20 Ground-Based Observatories (GBOs) are deployed across Canada and Alaska to support the collection of data from these instruments. Here we describe the system design of the observatory, with emphasis on how the design meets the environmental and data-collection requirements. We also review the design of the All Sky Imager (ASI), discuss how it was built to survive Arctic deployments, and summarize the optical characterizations performed to qualify the design to meet THEMIS mission requirements.

The NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) project is intended to investigate magnetospheric substorm phenomena, which are the manifestations of a basic instability of the magnetosphere and a dominant mechanism of plasma transport and explosive energy release. The major controversy in substorm science is the uncertainty as to whether the instability is initiated near the Earth, or in the more distant >20 Re magnetic tail. THEMIS will discriminate between the two possibilities by using five in-situ satellites and ground-based all-sky imagers and magnetometers, and inferring the propagation direction by timing the observation of the substorm initiation at multiple locations in the magnetosphere. An array of stations, consisting of 20 all-sky imagers (ASIs) and 30-plus magnetometers, has been developed and deployed in the North American continent, from Alaska to Labrador, for the broad coverage of the nightside magnetosphere. Each ground-based observatory (GBO) contains a white light imager that takes auroral images at a 3-second repetition rate (“cadence”) and a magnetometer that records the 3 axis variation of the magnetic field at 2 Hz frequency. The stations return compressed images, “thumbnails,” to two central databases: one located at UC Berkeley and the other at the University of Calgary, Canada. The full images are recorded at each station on hard drives, and these devices are physically returned to the two data centers for data copying. All data are made available for public use by scientists in “browse products,” accessible by using internet browsers or in the form of downloadable CDF data files (the “browse products” are described in detail in a later section). Twenty all-sky imager stations are installed and running at the time of this publication. An example of a substorm was observed on the 23rd of December 2006, and from the THEMIS GBO data, we found that the substorm onset brightening of the equatorward arc was a gradual process (>27 seconds), with minimal morphology changes until the arc breaks up. The breakup was timed to the nearest frame (<3 s) and located to the nearest latitude degree at about ±3oE in longitude. The data also showed that a similar breakup occurred in Alaska ∼10 minutes later, highlighting the need for an array to distinguish prime onset.

Article draft. Author list indicative and roughly corresponds to amount of contribution to the article to date.