Bibliography

Comments on “A new method to subtract dayglow for auroral observation of SSUSI in LBH ranges based on the improved AURIC” by Wang et al. (2021)

A paper A new method to subtract dayglow for auroral observation of SSUSI in LBH ranges based on the improved AURIC reports a new method to estimate the dayglow intensities in DMSP/SSUSI LBH bands using an improved AURIC model. It is claimed that the new method offers a better alternative than the SSUSI operational algorithm which uses a data based table. The paper showed a few examples and compared them with SSSUI operational results. The comparison indicated that the new method didn t offer any improvement and provided net auroral images with strong residual dayglow. On the other hand, the auroral oval can be easily recognized in the SSUSI data using the operational algorithm, despite some weak residual background which is expected due to count errors in the data. There are likely a few reasons why the method led to poor results: (1) dayglow contribution in SSUSI data covers solar zenith angles (SZA) beyond 90° and the AURIC model is limited to SZA ≤90°, (2) In addition to SZA, SSUSI radiances also depend on look angle (along and cross track pixels). Such a look-angle effect was apparently not reported in the paper. (3) The localized peaks in the plots (radiance versus SZA) were likely due to changes in solar EUV flux, SZA as well as noises caused Southern Atlantic Anomaly, MeV particles at sub-auroral latitude and glint in the Ap dependent data bins. The examples in the paper indicate that the new algorithm is not appropriate to estimate net SSUSI dayglow intensity.

Zhang, Yongliang; Paxton, Larry; Schaefer, Robert;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: mar

YEAR: 2022     DOI: 10.1016/j.jastp.2022.105833

AURORA; dayglow; far ultraviolet emission

AMICal Sat: A sparse RGB imager on board a 2U cubesat to study the aurora

AMICal sat, a dedicated 2U cubesat, has been developed, in order to monitor the auroral emissions, with a dedicated imager. It aims to help to reconstruct the low energy electrons fluxes up to 30 keV in Earth auroral regions. It includes an imager entirely designed in Grenoble University Space Center. The imager uses a 1.3 Mpixels sparse RGB CMOS detector and a wide field objective (f=22.5 mm). The satellite platform has been built by the polish company Satrevolution. Launched September, 3rd, 2020 from Kuru (French Guyana) on board the Vega flight 16, it produces its first images in October 2020. The aim of this paper is to describe the design of the payload especially the optics and the proximity electronics, to describe the use of the payload for space weather purpose. A preliminary analysis of a first image showing the relevance of such an instrument for auroral monitoring is performed. This analysis allowed to reconstruct from one of the first images the local electron input flux at the top of the atmosphere during the exposure time.

Barthelemy, Mathieu; Robert, Elisa; Kalegaev, Vladimir; Grennerat, Vincent; Sequies, Thierry; Bourdarot, Guillaume; Le Coarer, Etienne; Correia, Jean-Jacques; Rabou, Patrick;

Published by: IEEE Journal on Miniaturization for Air and Space Systems      Published on:

YEAR: 2022     DOI: 10.1109/JMASS.2022.3187147

Aerospace electronics; AURORA; cubesat; Detectors; imager; Instruments; Ion radiation effects; magnetosphere; Monitoring; Satellites

A new method to subtract dayglow for auroral observation of SSUSI in LBH ranges based on the improved AURIC

A new method to remove the dayglow components for auroral observations from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) aboard the Defense Meteorological Satellite Program (DMSP) F16 in Lyman-Birge-Hopfield (LBH) ranges based on the improved Atmospheric Ultraviolet Radiance Integrated Code (AURIC) algorithm is proposed in this study. This method is developed by determining the coefficients between the dayglow intensities calculated by the improved AURIC algorithm and the dayglow components from SSUSI in the whole 2005. The least-square polynomials are used to fit the calculations to the observations and the coefficients of the polynomials are divided by Ap indices and solar zenith angles (SZA). This algorithm can be used to simulate the dayglow intensity in the northern polar region at an altitude of 110 Km. Three examples with Ap indices 5, 27, 154 are tested to verify the effectiveness of the algorithm. The consistency between the original AURIC and the improved AURIC at nadir direction, the derived auroral images and the simulated dayglow images, also the fitting precisions and deviations between the dayglow intensities from improved AURIC and the dayglow intensities from SSUSI, demonstrate that this method is feasible and reliable. The proposed method provides us with a useful tool to separate the dayglow and aurora for space FUV observation.

Wang, JiaKe; Ding, GuangXing; Yu, Miao; Wang, HaiFeng;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: jan

YEAR: 2021     DOI: 10.1016/j.jastp.2020.105517

AURIC; AURORA; dayglow; FUV observation

The Dynamics of the Alfvénic Oval

The auroral oval is a well-established concept, introduced more than five decades ago. The Alfvénic oval, on the other hand, is a very recent concept, which has been revealed in both observational and numerical studies. This is the first review of the global Alfvénic oval, while also defining primary, secondary and tertiary layers of the Alfvénic oval. The focus lies on the large-scale dynamic properties of the global Alfvénic oval in relation to the AE index, substorm phases, storm phases and solar wind/IMF conditions. Statistical data recorded above and below the nominal auroral acceleration region are reviewed, together with results from global simulation studies. The Alfvénic oval s relation to the auroral oval is also reviewed. This review demonstrates that the Alfvénic oval is well enough defined and investigated to give it its name, and it demonstrates that our understanding allows for the prediction of the Alfvénic oval under various conditions.

Keiling, Andreas;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: aug

YEAR: 2021     DOI: 10.1016/j.jastp.2021.105616

AURORA; Alfven wave; Energy transport; geomagnetic activity; magnetosphere-ionosphere coupling; Wave-particle interaction

Evaluating Auroral Forecasts Against Satellite Observations

The aurora is a readily visible phenomenon of interest to many members of the public. However, the aurora and associated phenomena can also significantly impact communications, ground-based infrastructure, and high-altitude radiation exposure. Forecasting the location of the auroral oval is therefore a key component of space weather forecast operations. A version of the OVATION-Prime 2013 auroral precipitation model (Newell et al., 2014, https://doi.org/10.1002/2014sw001056) was used by the UK Met Office Space Weather Operations Centre (MOSWOC). The operational implementation of the OVATION-Prime 2013 model at the UK Met Office delivered a 30-min forecast of the location of the auroral oval and the probability of observing the aurora. Using weather forecast evaluation techniques, we evaluate the ability of the OVATION-Prime 2013 model forecasts to predict the location and probability of the aurora occurring by comparing the forecasts with auroral boundaries determined from data from the IMAGE satellite between 2000 and 2002. Our analysis shows that the operational model performs well at predicting the location of the auroral oval, with a relative operating characteristic (ROC) score of 0.82. The model performance is reduced in the dayside local time sectors (ROC score = 0.59) and during periods of higher geomagnetic activity (ROC score of 0.55 for Kp = 8). As a probabilistic forecast, OVATION-Prime 2013 tends to underpredict the occurrence of aurora by a factor of 1.1–6, while probabilities of over 90\% are overpredicted.

Mooney, M.; Marsh, M.; Forsyth, C.; Sharpe, M.; Hughes, T.; Bingham, S.; Jackson, D.; Rae, I.; Chisham, G.;

Published by: Space Weather      Published on:

YEAR: 2021     DOI: 10.1029/2020SW002688

AURORA; auroral forecasting; forecast verification; OVATION-Prime 2013; ROC scores; space weather

Temporal evolution of substorm-driven global Alfv\ en wave power above the auroral acceleration region

The onset of substorms is associated with bursty enhancements of Alfv\ en wave power throughout the magnetotail. While impossible to assess the total Alfv\ en wave power in the entire magnetotail, we have instead monitored waves that are funneled into the auroral acceleration region, in order to assess the temporal evolution of Alfv\ en wave power above the nightside auroral zone in relation to substorm phases. The substorms were grouped by three conditions: nonstorm periods, storm periods, and all (unconditioned) periods. Using superposed epoch analysis, we found that the global magnetohydrodynamic Alfv\ en wave power increased significantly at onset for all three conditions, while a power decrease to pre-onset values occurred within 2 h. Specifically, the peak inflowing power during the expansion phase was 5.7 GW for unconditioned substorms, 5.6 GW for nonstorm-time substorms, and 7.8 GW for storm-time substorms. These results correspond to power increases with respect to pre-onset values of 138\%, 366\%, and 200\%, respectively. Additional analysis in relation to the aurora was performed for nonstorm-time substorms only. During the expansion phase, about 50\% of the Alfv\ en wave power over the entire nightside auroral zone is collocated with the auroral bulge region. Furthermore, the total inflowing Alfv\ en wave power over the entire nightside auroral zone is 17\% of the conjugate auroral power, while the inflowing power over the auroral bulge region is 32\% of the conjugate aurora. However, allowing for a finite absorption efficiency inside the auroral acceleration region, the likely average Alfv\ enic contributions to the aurora are approximately 10\% and 18\%,respectively.

Keiling, Andreas; Thaller, Scott; Dombeck, John; Wygant, John;

Published by: Journal of Geophysical Research: Space Physics      Published on: 03/2020

YEAR: 2020     DOI: 10.1029/2019JA027444

Alfven wave; Alfvenic electron; AURORA; auroral acceleration; magnetotail; Substorm

Auroral Structure and Dynamics From GOLD

The Global-scale Observations of the Limb and Disk (GOLD) mission data contain significant quantitative information about the aurora on a global scale. Here we present techniques for quantifying such information, including the temporal development of the structure within the auroral oval using the GOLD images. These techniques are applied to auroral observations in the GOLD data, in particular showing an example of how the longitudinal structure within the aurora varies over the course of six consecutive days with differing levels of geomagnetic activity. A simple model of the solar-induced airglow is presented that is used to remove the sunlight contamination from the dayside auroral observations. Comparisons to ground-based auroral imaging are used for the overall auroral context and to make estimates of the proportionality between the intensities of the green line (557.7\ nm) emission in the visible and the 135.6\ nm emissions in the GOLD data. These observations are consistent with the intensity of the 135.6\ nm auroral emission being on the same order as the intensity of the 557.7\ nm auroral emission. They were both found to be around 1\ kR for a stable auroral arc on a day with low geomagnetic activity (3 November 2018) and around 10\ kR for an active auroral display on a day with higher levels of geomagnetic activity (5 November 2018). This could have important implications for making direct comparisons between space-based ultraviolet auroral imaging and ground-based visible-light auroral imaging and the total energy input estimates that are derived from them.

Michell, R.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2020

YEAR: 2020     DOI: 10.1029/2019JA027650

AURORA; GOLD; GUVI

Local Geomagnetic Indices and the Prediction of Auroral Power

The aurora has been related to magnetometer observations for centuries, and to geomagnetic indices for decades. As the number of stations and data processing power increases, just how auroral power (AP) relates to geomagnetic observations becomes a more tractable question. This paper compares Polar UVI AP observations during 1997 with a variety of indices. Local time (LT) versions of the SuperMAG auroral electrojet (SME) are introduced and examined, along with the corresponding upper and lower envelopes (SMU and SML). Also, the East\textendashwest component, B_E, is investigated. We also consider whether using any of the local indices is actually better at predicting local AP than a single global index. Each index is separated into 24 LT indices with a sliding 3-h MLT window. The ability to predict AP varies greatly with LT, peaking at 1900 MLT, where about 75\% of the variance (r²) is predicted at 1-min cadence. The aurora is fairly predictable from 1700 MLT \textendash 0400 MLT, roughly the region in which substorms occur. AP is poorly predicted from auroral electrojet indices from 0500 MLT \textendash 1500 MLT, with the minimum at 1000\textendash1300 MLT. In the region of high predictability, the local index which works best is B_E (East\textendashwest), in contrast to long-standing expectations. However using global SME is better than any local index. AP is best predicted by combining global SME with a local index: B_E from 1500\textendash0300 MLT, and either SMU or SML from 0300\textendash1500 MLT. In the region of the diffuse aurora, it is better to use a 30 min average than the cotemporaneous 1-min SME value, while from 1500\textendash0200 MLT the cotemporaneous 1-min SME works best, suggesting a more direct physical relationship with the auroral circuit. These results suggest a significant role for discrete auroral currents closing locally with Pedersen currents.

Newell, P.; Gjerloev, J.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 12/2014

YEAR: 2014     DOI: 10.1002/2014JA020524

AURORA; auroral electrojet; indices; Pedersen current; Prediction

OVATION Prime-2013: Extension of auroral precipitation model to higher disturbance levels

OVATION Prime (OP) is an auroral precipitation model parameterized by solar wind driving. Distinguishing features of the model include an optimized solar wind-magnetosphere coupling function (dΦ_MP/dt) which predicts auroral power significantly better than\ Kp\ or other traditional parameters, the separation of aurora into categories (diffuse aurora, monoenergetic, broadband, and ion), the inclusion of seasonal variations, and separate parameter fits for each magnetic latitude (MLAT) \texttimes magnetic local time (MLT) bin, thus permitting each type of aurora and each location to have differing responses to season and solar wind input\textemdashas indeed they do. We here introduce OVATION Prime-2013, an upgrade to the 2010 version currently widely available. The most notable advantage of OP-2013 is that it uses UV images from the GUVI instrument on the satellite TIMED for high disturbance levels (dΦ_MP/dt \> 1.2 MWb/s which roughly corresponds toKp = 5+ or 6-). The range of validity is approximately 0 \< dΦ_MP/dt <= 3.0 MWb/s (Kp\ about 8+). Other upgrades include a reduced susceptibility to salt-and-pepper noise, and smoother interpolation across the postmidnight data gap. The model is tested against an independent data set of hemispheric auroral power from Polar UVI. Over the common range of validity of OP-2010 and OP-2013, the two models predict auroral power essentially identically, primarily because hemispheric power calculations were done in a way to minimize the impact of OP-2010s noise. To quantitatively demonstrate the improvement at high disturbance levels would require multiple very large substorms, which are rare, and insufficiently present in the limited data set of Polar UVI hemispheric power values. Nonetheless, although OP-2010 breaks down in a variety of ways above\ Kp = 5+ or 6-, OP-2013 continues to show the auroral oval advancing equatorward, at least to 55\textdegree MLAT or a bit less, and OP-2013 does not develop spurious large noise patches. We will also discuss the advantages and disadvantages of other precipitation models more generally, as no one model fits best all possible uses.

Newell, P.; Liou, K.; Zhang, Y.; Sotirelis, T.; Paxton, L.; Mitchell, E.;

Published by: Space Weather      Published on: 06/2014

YEAR: 2014     DOI: 10.1002/swe.v12.610.1002/2014SW001056

AURORA; precipitation; forecasting

GNSS radio occultation (RO) derived electron density quality in high latitude and polar region: NCAR-TIEGCM simulation and real data evaluation

Global Navigation Satellite System (GNSS) based radio occultation (RO) technique has shown powerful ability in ionospheric electron density profiling in the past decade. The most frequently used Abel inversion method in electron density retrieval has some biases because of the used spherical symmetry assumption. Our previous series simulations and evaluations mainly concentrated in the middle and low latitude regions have shown some systematical bias especially in lower altitude of low latitude region. However, the RO derived electron density quality in the high latitude and polar region is rarely investigated and not quantitatively clear yet. In this study, the Abel inversion error over high latitude and polar regions are systematically investigated for the first time based on NCAR-TIEGCM simulations and real data evaluations. The TIMED data driven NCAR-TIEGCM modeled electron density during 2008 are used to simulate the COSMIC RO events. The Abel inversion error can then be estimated by comparing Abel retrievals from TIEGCM simulated occultation with the original TIEGCM simulations. The Abel inversion can reproduce the season, altitude, latitude, and local time variation patterns of electron density and auroral zone electron density nighttime enhancement well in high latitude and polar region. The Abel inversion tends to underestimate the electron density in the auroral zone and overestimate it on both the equatorward and poleward sides of the auroral zone. As simulated by the TIEGCM model, the significant relative error (\>25\%) mainly occurs in lower altitude (\<250\ km) inside and around auroral zone region. Above 250\ km, the relative error mostly is less than 25\%. Specifically, RMSE (root mean square error) of NmF2 error from simulation is \~8.5\%. The Abel error under real ionosphere situation would be worse because the ionosphere could be more complicated and noisier than the model simulation. The error distribution and its seasonal, local time and latitude variations can be explained by the spherical symmetry assumption used in the Abel inversion associated with the corresponding ionospheric electron density variations. The comparisons between PFISR and COSMIC RO electron density during 2007\textendash2011 and some previous validation studies agree well with our simulation results. We hope these results can stimulate more studies in high latitude ionospheric research using RO data.

Yue, Xinan; Schreiner, William; Kuo, Ying-Hwa; Wu, Qian; Deng, Yue; Wang, Wenbin;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 06/2013

YEAR: 2013     DOI: 10.1016/j.jastp.2013.03.009

Abel inversion; AURORA; COSMIC; Electron density; GNSS radio occultation; TIEGCM

Empirical STORM-E model: II. Geomagnetic corrections to nighttime ionospheric E-region electron densities

Auroral nighttime infrared emission observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere\textendashIonosphere\textendashMesosphere Energetics and Dynamics (TIMED) satellite is used to develop an empirical model of geomagnetic storm enhancements to E-region electron densities. The empirical model is called STORM-E and will be incorporated into the 2012 release of the International Reference Ionosphere (IRI). The proxy for characterizing the E-region response to geomagnetic forcing is NO⁺(v) Volume Emission Rates (VER) derived from the TIMED/SABER 4.3\ μm channel limb radiance measurements. The storm-time response of the NO⁺(v) 4.3\ μm VER is most sensitive to auroral particle precipitation. A statistical database of storm-time to climatological quiet-time ratios of SABER-observed NO⁺(v) 4.3\ μm VER are fit to widely available geomagnetic indices using the theoretical framework of linear impulse-response theory. The STORM-E model provides a dynamic storm-time correction factor to adjust a known nighttime quiescent E-region electron density peak concentration for geomagnetic enhancements due to auroral particle precipitation. Part I of this series gives a detailed description of the algorithms and methodologies used to derive NO⁺(v) VER from SABER 4.3\ μm limb emission measurements. In this paper, Part II of the series, the development of the E-region electron density storm-time correction factor is described. The STORM-E storm-time correction factor is fit to a single geomagnetic index. There are four versions of the STORM-E model, which are currently independent of magnetic local time. Each version is fit to one of the following indices: HP, AE, Ap, or Dst. High-latitude Incoherent Scatter Radar (ISR) E-region electron density measurements are compared to STORM-E predictions for various geomagnetic storm periods during solar cycle 23. These comparisons show that STORM-E significantly improves the prediction of E-region electron density enhancements due to auroral particle precipitation, in comparison to the nominal IRI model or to the quiet-time baseline electron density concentrations measured by ISR. The STORM-E/ISR comparisons indicate that the STORM-E fits to the Ap-, AE-, and HP-indices are comparable in both absolute accuracy and relative dynamical response. Contrarily, the Dst-index does not appear to be a suitable input driver to parameterize the E-region electron density response to geomagnetic activity.

Mertens, Christopher; Xu, Xiaojing; Bilitza, Dieter; Mlynczak, Martin; Russell, James;

Published by: Advances in Space Research      Published on: 02/2013

YEAR: 2013     DOI: 10.1016/j.asr.2012.09.014

AURORA; Auroral particle precipitation; E-region; Infrared remote sensing; Ionosphere; Magnetic storm; TIMED

Evaluation of OVATION Prime as a forecast model for visible aurorae

This study evaluates the ability of the OVATION Prime auroral precipitation model to provide operational forecasts of the visible aurora. An operational implementation would primarily provide the general public with some guidance for viewing the aurora. We evaluate the likelihood that if aurorae are predicted to be visible at a location, they will be seen there within the hour. Nighttime model forecasts were validated with Polar Ultraviolet Imager data for Kp >= 3 and for the years 1997 and 1998. The overall forecasts for a visible aurora to occur or to not occur were correct 77\% of the time. The most important prediction for public auroral viewing is that the visible aurora will occur, and these forecasts were correct 86\% of the time.

Machol, Janet; Green, Janet; Redmon, Robert; Viereck, Rodney; Newell, Patrick;

Published by: Space Weather: The International Journal of Research and Applications      Published on: 09/2012

YEAR: 2012     DOI: 10.1029/2011SW000746

AURORA; model

Contributions of imaging Echelle spectrographs to daytime optical aeronomy

We present a brief overview of the contributions made by high spectral resolution imaging spectrographs that are capable of obtaining daytime airglow and auroral emissions in the presence of scattered solar background continuum, to the advancement in our understanding of the dynamics in daytime upper atmosphere. By making use of ground-based OI 6300 angstrom daytime emissions from various geomagnetic latitudes this technique has succeeded in demonstrating many interesting and first of their kind results ranging from ionosphere–thermosphere coupling, space weather interactions to magnetosphere–thermosphere–ionosphere coupling. Finally, in view of the promising results by this technique we propose future advancements in both instrumentation and strategic observational planning with optical spectrographs.

Pallamraju, D.; Chakrabarti, S.;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on:

YEAR: 2006     DOI: https://doi.org/10.1016/j.jastp.2005.05.013

dayglow; AURORA; Spectroscopy; Optical techniques; Thermosphere–ionosphere coupling; space weather

Compact FUV camera concept for space weather applications

Far ultraviolet (FUV) images of Earth from space have proven invaluable in revealing contextual phenomena associated with space weather in the high latitude auroral regions and in the mid and equatorial regions. Images of this nature can be used to investigate compelling questions associated with the interaction of the ionosphere/mesosphere-magnetosphere-solar wind. Observations using images that lead to quantitative analyses are required to significantly advance the state of knowledge with regard to the affects of space weather and the interaction between and within these regions of Geospace. Current available image data sets are sufficient for qualitative analysis and morphological investigations, and while quantitative analyses are possible, they are difficult and limited to few events at best^1,2. In order to qualitatively access the time, spatial, and causal phenomena on global scales, simultaneous images of various FUV emissions with a combination of better spatial, temporal and spectral resolution and sensitivity than currently available are required. We present an instrument concept that is being developed to improve the spatial, temporal and spectral resolution and sensitivity needed to perform the quantitative analysis that enable significant advancement in our understanding of the impact of space weather on Geospace. The approach is to use the "self-filtering" concept³ that combines the imaging and filtering functions and thus reduces the size of the 4-mirror off-axis optical system. The optical and filter design will de described.

Spann, James; Fineschi, Silvano; Viereck, Rodney;

Published by:       Published on:

YEAR: 2005     DOI: 10.1117/12.615201

Camera; Filters; far ultraviolet; space weather; MI coupling; Ionosphere; AURORA; Geospace

Initial observations with the Global Ultraviolet Imager (GUVI) in the NASA TIMED satellite mission

The Global Ultraviolet Imager (GUVI) instrument carried aboard the NASA TIMED satellite measures the spectral radiance of the Earth\textquoterights far ultraviolet airglow in the spectral region from 120 to 180 nm using a cross-track scanning spectrometer design. Continuous operation of the instrument provides images of the Earth\textquoterights disk and limb in five selectable spectral bands. Also, spectra at fixed scanning mirror position can be obtained. Initial results demonstrate the quantitative functionality of the instrument for studies of the Earth\textquoterights dayglow, aurora, and ionosphere. Moreover, through forward modeling, the abundance of the major constituents of the thermosphere, O, N₂, and O₂\ and thermospheric temperatures can be retrieved from observations of the limb radiance. Variations of the column O/N₂\ ratio can be deduced from sunlit disk observations. In regions of auroral precipitation not only can the aurora regions be geographically located and the auroral boundaries identified, but also the energy flux Q, the characteristic energy E_o, and a parameter f_o\ that scales the abundance of neutral atomic oxygen can be derived. Radiance due to radiative recombination in the ionospheric F region is evident from both dayside and nightside observations of the Earth\textquoterights limb and disk, respectively. Regions of depleted F-region electron density are evident in the tropical Appleton anomaly regions, associated with so-called ionospheric \textquotedblleftbubbles.\textquotedblright Access to the GUVI data is provided through the GUVI website\ www.timed.jhuapl.edu\guvi.

Christensen, AB; Paxton, LJ; Avery, S; Craven, J; Crowley, G; Humm, DC; Kil, H; Meier, RR; Meng, C-I; Morrison, D; , others;

Published by: Journal of Geophysical Research: Space Physics (1978\textendash2012)      Published on:

YEAR: 2003     DOI: 10.1029/2003JA009918

airglow; AURORA; ultraviolet; imaging; satellite; atmosphere

Sudden solar wind dynamic pressure enhancements and dayside detached auroras: IMAGE and DMSP observations

Dayside detached auroras (DDA) refer to auroras observed separate from the equatorward edge of the main oval on the dayside. They are studied here using IMAGE FUV and DMSP particle data. Occurrence of these DDA appears to be correlated with sudden solar wind dynamic pressure enhancements and northward interplanetary magnetic field, as monitored by the Wind satellite. They are usually very dynamic and short-lived with a lifetime of the order of 10 minutes. Out of the three FUV instrument channels on IMAGE, DDA are best detected by the IMAGE FUV SI-12 instrument, which measures intensities of the Doppler red-shifted Hydrogen Lyman Alpha line. This indicates that energetic proton precipitation is the major component. Simultaneous DMSP particle observations confirm that energetic protons (\>10 keV) in the dayside inner magnetosphere are the primary source of those DDA detected by the SI-12 instrument. DMSP also detected significant electron fluxes associated with the DDA, but the electron precipitations have little or no contribution to the DDA intensities detected by the SI-12 instrument. Precipitations of energetic protons (electrons) which caused DDA could be explained by enhanced cyclotron instability which arose from adiabatic compression following sudden solar wind dynamic pressure enhancements.

Zhang, Y.; Paxton, L.J.; Immel, T.; Frey, H.;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2002     DOI: 10.1029/2002JA009355

AURORA; dayside detached aurora; proton precipitation; solar wind pressure enhancement