Coordinated Ionospheric Reconstruction CubeSat Experiment (CIRCE), In situ and Remote Ionospheric Sensing (IRIS) suite

The UK’s Defence Science and Technology Laboratory (Dstl) is partnering with the US Naval Research Laboratory (NRL) on a joint mission to launch miniature sensors that will advance space weather measurement and modelling capabilities. The Coordinated Ionospheric Reconstruction Cubesat Experiment (CIRCE) comprises two 6U cube-satellites that will be launched into a near-polar low earth orbit (LEO), targeting 500 km altitude, in 2021. The UK contribution to CIRCE is the In situ and Remote Ionospheric Sensing (IRIS) suite, complementary to NRL sensors, and comprising three highly miniaturised payloads provided to Dstl by University College London (UCL), University of Bath, and University of Surrey/Surrey Satellite Technology Ltd (SSTL). One IRIS suite will be flown on each satellite, and incorporates an ion/neutral mass spectrometer, a tri-band global positioning system (GPS) receiver for ionospheric remote sensing, and a radiation environment monitor. From the US, NRL have provided two 1U Triple Tiny Ionospheric Photometers (Tri-TIPs) on each satellite (Nicholas et al., 2019), observing the ultraviolet 135.6 nm emission of atomic oxygen at night-time to characterize the two-dimensional distribution of electrons

Far‐UV emissions from the SL9 impacts with Jupiter

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95348/1/grl8617.pd

Middle ultraviolet remote sensing of the equatorial thermosphere during a geomagnetic storm

We present measurements of the equatorial middle ultraviolet airglow taken during the week of 21-28 May 2000, including a strong geomagnetic storm on 24 May. Limb spectra were taken by the Ionospheric Spectroscopy and Atmospheric Chemistry (ISAAC) experiment on the Advanced Research and Global Observation Satellite (ARGOS). OII lines near 247.0nm and NII lines near 214.3nm provide a measure of thermospheric O and N2 changes, respectively. Our results show increases in airglow brightness of both emissions during the storm that we interpret as increases in the concentrations of both species, but the ratio of intensities that correspond to O/N2 is lower than expected during and after the storm. We also invert the emission profiles using discrete inverse theory, to obtain a measure of thermospheric neutral temperatures during this time. Although temperatures increase after the main phase of the storm, the increases do not correlate with the observed features in the intensity ratio. These data could be explained by vertical winds and tides modifying the equatorial neutral composition during storms, in addition to common heating responses

Modeled and observed N-2 Lyman-Birge-Hopfield band emissions: A comparison

A thorough understanding of how the N-2 Lyman-Birge-Hopfield (LBH) band emissions vary with altitude is essential to the use of this emission by space-based remote sensors. In this paper, model-to-model comparisons are first performed to elucidate the influence of the solar irradiance spectrum, intrasystem cascade excitation, and O-2 photoabsorption on the limb profile. Next, the observed LBH emissions measured by the High resolution Ionospheric and Thermospheric Spectrograph aboard the Advanced Research and Global Observation Satellite are compared with modeled LBH limb profiles to determine which combination of parameters provides the best agreement. The analysis concentrates on the altitude dependence of the LBH (1,1) band, the brightest LBH emission in the observations. In the analysis, satellite drag data are used to constrain the neutral densities used for the data-to-model comparisons. For the average limb profiles on two of the three days analyzed (28, 29, and 30 July 2001), calculations using direct excitation alone give slightly better agreement with the observations than did calculations with cascading between the singlet electronic N-2 states (a(1)Pi(g), a\u27Sigma(-)(u), and w(1)Delta(u)); however, the differences between the observed profiles and either model are possibly greater than the differences between the models. Nevertheless, both models give excellent agreement with the observations, indicating that current models provide an adequate description of the altitude variation of the N-2 LBH (1,1) band emissions. Consequently, when using the LBH bands to remotely sense thermospheric temperatures, which can be used to provide an unprecedented view of the thermosphere, the temperatures derived have a negligible dependence on the model used

Remote sensing of neutral temperatures in the Earth\u27s thermosphere using the Lyman-Birge-Hopfield bands of N-2: Comparisons with satellite drag data

This paper presents remotely sensed neutral temperatures obtained from ultraviolet observations and compares them with temperatures from the NRLMSISE-00 version of the Mass Spectrometer and Incoherent Scatter (MSIS) model (unconstrained and constrained to match the total densities from satellite drag). Latitudinal profiles of the temperatures in the Earth\u27s thermosphere are obtained by inversion of high-resolution (similar to 1.3 angstrom) observations of the (1,1) and (5,4) Lyman-Birge-Hopfield (LBH) bands of N-2. The spectra are from the High resolution Ionospheric and Thermospheric Spectrograph (HITS) instrument aboard the Advanced Research and Global Observation Satellite (ARGOS). The results indicate that on each day examined there was consistency between the remotely sensed thermospheric temperatures, the densities from coincident satellite drag measurements at adjacent altitudes, and the NRLMSISE-00 model

Doppler Profiles of Proton Auroral Emissions Derived From High Resolution FUV Spectra

In this paper we present new FUV observations of Doppler-shifted Lyman-ë± emissions from proton aurorae obtained from the High-resolution Ionospheric and Thermospheric Spectrograph (HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS). The Doppler profiles of the Lyman-ë± auroral emissions serve as proxies for the energy spectra of precipitating protons in the ionosphere. These observations remedy two previous shortcomings in proton aurora studies. There have been few spectral measurements of Doppler-shifted H/H[SUP]+[/SUP] emission profiles with which to validate existing models of proton flux transport in the ionosphere. Even fewer are spectral measurements of this kind over large spatial scales that would extend our understanding of proton aurora to a global level. The HITS instrument observes the Doppler shifted H Lyman-ë± emissions from proton precipitation at 0.5 Ì· resolution over the width of the auroral oval traversed by the ARGOS spacecraft. The measured Doppler spectra of proton emissions are then modeled using a Monte Carlo simulation of proton flux transport. The model parameters which include the incoming proton energy, pitch angle, and energy flux distributions are adjusted until the predicted Lyman-ë± Doppler profiles match the observations. This technique allows us to quantify the evolution of proton precipitation during varying levels of auroral activity with both spectral information and large-scale spatial coverage. We present our analysis of proton auroral observations for an isolated substorm event as an example

On the Characteristics and Source Regions of Dayside Proton Precipitation

audience: researcher, professionalThe source regions of precipitating protons on the dayside and their dependence on solar wind conditions are studied using far-ultraviolet (FUV) spectral observations and imaging. The High-resolution Ionospheric and Thermospheric Spectrograph (HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS) observes Doppler-shifted H Lyman-α emissions from precipitating protons with a spectral resolution of 1.5 Angstroms. The shapes of these Doppler spectra are indicative of the energy and pitch angle distributions of the proton precipitation. Global images of H Lyman-α emissions obtained by the SI-12 instrument on the IMAGE spacecraft are examined to relate the spectral observations to the dayside morphology of the proton aurora. During periods of sustained southward interplanetary magnetic field (IMF), the dayside proton aurora spectra exhibit broad Doppler shifts and are similar to those observed on the nightside with inferred mean energies typical of plasma sheet protons of magnetospheric origin. Global images of proton aurorae under these conditions show continuous regions of H Lyman-α emissions across the dayside extending from the nightside. In contrast, during periods of northward or variable IMF, proton aurora emissions on the dayside often appear in an isolated spot in the noon to late afternoon MLT sector. The Doppler-spectra of the proton emissions in these regions are narrow, indicating precipitation with low mean energies and from a different origin than that observed in the southward IMF cases. These spectra may be indicative of magnetosheath protons that have direct access to the ionosphere through high-latitude dayside reconnection. This study further quantifies the characteristics of dayside proton precipitation under various states of the magnetosphere and highlights the importance of IMF orientation on the coupling between the high-latitude, dayside ionosphere and its plasma sources at higher altitudes

High-Resolution Limb Observations of Proton Aurora

The interaction of precipitating protons in the upper atmosphere involves charge exchange, ionization, elastic and inelastic collisions, and the deposition of energy from the bottom of the F-region to the D-region of the ionosphere. These processes and the transport of incident protons through this range of altitudes has been described through a variety of modeling techniques but there has been a dearth of altitude-resolved observations of proton precipitation with which to validate such models. We present new limb observations of Doppler-shifted Lyman-α proton aurora emissions obtained by the High-resolution Ionospheric and Thermospheric Spectrograph (HITS) aboard the Advanced Research and Global Observation Satellite (ARGOS) that fill this niche. HITS performs limb scans that include tangent altitudes between 90 km and 400 km with approximately 5 km vertical resolution. The Doppler shifts of the proton aurora Lyman-α emissions are measured with 1.5 Angstrom resolution and are used to infer mean energies of the incident protons as a function of altitude. Observed energy-range (dE/dz) relations are compared to those predicted by a Monte Carlo simulation of proton transport in the upper atmosphere