Estimating Precipitating Energy Flux, Average Energy, and Hall Auroral Conductance From THEMIS All-Sky-Imagers With Focus on Mesoscales

Recent attention has been given to mesoscale phenomena across geospace (∼10 s km to 500 km in the ionosphere or ∼0.5 RE to several RE in the magnetosphere), as their contributions to the system global response are important yet remain uncharacterized mostly due to limitations in data resolution and coverage as well as in computational power. As data and models improve, it becomes increasingly valuable to advance understanding of the role of mesoscale phenomena contributions—specifically, in magnetosphere-ionosphere coupling. This paper describes a new method that utilizes the 2D array of Time History of Events and Macroscale Interactions during Substorms (THEMIS) white-light all-sky-imagers (ASI), in conjunction with meridian scanning photometers, to estimate the auroral scale sizes of intense precipitating energy fluxes and the associated Hall conductances. As an example of the technique, we investigated the role of precipitated energy flux and average energy on mesoscales as contrasted to large-scales for two back-to-back substorms, finding that mesoscale aurora contributes up to ∼80% (∼60%) of the total energy flux immediately after onset during the early expansion phase of the first (second) substorm, and continues to contribute ∼30–55% throughout the remainder of the substorm. The average energy estimated from the ASI mosaic field of view also peaked during the initial expansion phase. Using the measured energy flux and tables produced from the Boltzmann Three Constituent (B3C) auroral transport code (Strickland et al., 1976; 1993), we also estimated the 2D Hall conductance and compared it to Poker Flat Incoherent Scatter Radar conductance values, finding good agreement for both discrete and diffuse aurora.

Investigating magnetopause dynamics using global magnetosphere simulation

<p>Detailed 3D magnetopause surface is identified using field line and flow line tracing techniques on Space Weather Modeling Framework (SWMF) global magnetosphere simulation results. A total energy flux vector dominated by poynting flux is dotted with area element surface normals and integrated to determine energy transfer into the closed volume. Magnetopause characteristics, power and energy terms are compared with space weather indices such as Disturbance Storm-Time (Dst), Auroral Electrojet (AE), Cross Polar Cap Potential (CPCP) and emperical models such as Shue et al (1997) and Shue et al (1998) to investigate magnetopause dynamics. The storm event of Feb 18, 2014  is simulated with SWMF and analyzed. This event starts in the middle of a multi-CME impact, during a delay between the first and second CME's. While some preconditioning may have occured, it provides an excellent case for observing magnetopause variations. Results show close agreement with empirical models of integrated energy transfer through magnetopause surface. Energy accumulation inside magnetopause volume cuttoff at x=-20Re shows similar behavior to Dst.</p>

On the crucial role of atmospheric rivers in the two major Weddell Polynya events in 1973 and 2017 in Antarctica

This study reports the occurrence of intense atmospheric rivers (ARs) during the two large Weddell Polynya events in November 1973 and September 2017 and investigates their role in the opening events via their enhancement of sea ice melt. Few days before the polynya openings, persistent ARs maintained a sustained positive total energy flux at the surface, resulting in sea ice thinning and a decline in sea ice concentration in the Maud Rise region. The ARs were associated with anomalously high amounts of total precipitable water and cloud liquid water content exceeding 3 SDs above the climatological mean. The above-normal integrated water vapor transport (IVT above the 99th climatological percentile), as well as opaque cloud bands, warmed the surface (+10°C in skin and air temperature) via substantial increases (+250 W m−2) in downward longwave radiation and advection of warm air masses, resulting in sea ice melt and inhibited nighttime refreezing.

Neoclassical Navier–Stokes Equations Considering the Gyftopoulos–Beretta Exposition of Thermodynamics

The seminal Navier–Stokes equations were stated even before the creation of the foundations of thermodynamics and its first and second laws. There is a widespread opinion in the literature on thermodynamic cycles that the Navier–Stokes equations cannot be taken as a thermodynamically correct model of a local “working fluid”, which would be able to describe the conversion of “heating” into “working” (Carnot’s type cycles) and vice versa (Afanasjeva’s type cycles). Also, it is overall doubtful that “cycle work is converted into cycle heat” or vice versa. The underlying reason for this situation is that the Navier–Stokes equations come from a time when thermodynamic concepts such as “internal energy” were still poorly understood. Therefore, this paper presents a new exposition of thermodynamically consistent Navier–Stokes equations. Following that line of reasoning—and following Gyftopoulos and Beretta’s exposition of thermodynamics—we introduce the basic concepts of thermodynamics such as “heating” and “working” fluxes. We also develop the Gyftopoulos and Beretta approach from 0D into 3D continuum thermodynamics. The central role within our approach is played by “internal energy” and “energy conversion by fluxes.” Therefore, the main problem of exposition relates to the internal energy treated here as a form of “energy storage.” Within that context, different forms of energy are discussed. In the end, the balance of energy is presented as a sum of internal, kinetic, potential, chemical, electrical, magnetic, and radiation energies in the system. These are compensated by total energy flux composed of working, heating, chemical, electrical, magnetic, and radiation fluxes at the system boundaries. Therefore, the law of energy conservation can be considered to be the most important and superior to any other law of nature. This article develops and presents in detail the neoclassical set of Navier–Stokes equations forming a thermodynamically consistent model. This is followed by a comparison with the definition of entropy (for equilibrium and non-equilibrium states) within the context of available energy as proposed in the Gyftopoulos and Beretta monograph. The article also discusses new possibilities emerging from this “continual” Gyftopoulos–Beretta exposition with special emphasis on those relating to extended irreversible thermodynamics or Van’s “universal second law”.

Effects of the interplanetary magnetic field y component on the dayside aurora

A dawn–dusk asymmetry in many high-latitude ionospheric and magnetospheric phenomena, including the aurora, can be linked to the east–west (y) component of the interplanetary magnetic field (IMF). Owing to the scarcity of observations in the Southern Hemisphere, most of the previous findings are associated with the Northern Hemisphere. It has long been suspected that if the IMF By component also produces a dawn–dusk asymmetry and/or a mirror image in the Southern Hemisphere as predicted by some theories. The present study explores the effect of the IMF By component on the dayside aurora from both hemispheres by analyzing the auroral emission data from the Global UltraViolet scanning spectrograph Imager on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics mission spacecraft from 2002 to 2007. The data set comprises 28,774 partial images of the northern hemispheric oval and 29,742 partial images of the southern hemispheric oval, allowing for a statistical analysis. It is found that even though auroras in different regions of the dayside oval respond differently to the orientation of the IMF By component, their responses are opposite between the two hemispheres. For example, at ~ 1400–1600 MLT in the Northern Hemisphere, where the so-called 1500 MLT auroral hot spots occur, peak auroral energy flux is larger for negative IMF By comparing to positive IMF By. The response is reversed in the Southern Hemisphere. The present study also suggests that the total energy flux does not change with the IMF By orientation change. This result is consistent with a larger (smaller) convection vortex in the postnoon sector for IMF By < 0 (By > 0) resulting from anti-parallel merging.

Kinematics and Energetics of A Solar Jet from NOAA Active Region 12297

In this article, we have presented the study of a solar jet on March 14, 2015 recorded from the Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO) satellite. The jet was observed from the solar active region NOAA AR 12297. We have discussed the dynamics and calculated the various possible energy contents of the observed jet. The estimated total energy flux liberated during the jet ejection was 2.1 x 107 erg cm-2 s-1 .

Kinematics and Energetics of A Solar Jet from NOAA Active Region 12297

In this article, we have presented the study of a solar jet on March 14, 2015 recorded from the Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO) satellite. The jet was observed from the solar active region NOAA AR 12297. We have discussed the dynamics and calculated the various possible energy contents of the observed jet. The estimated total energy flux liberated during the jet ejection was 2.1 x 107 erg cm-2 s-1 .

Satellite Investigation of the M2 Internal Tide in the Tasman Sea

The M2 internal tide in the Tasman Sea is investigated using sea surface height measurements made by multiple altimeter missions from 1992 to 2012. Internal tidal waves are extracted by two-dimensional plane wave fits in 180 km by 180 km windows. The results show that the Macquarie Ridge radiates three internal tidal beams into the Tasman Sea. The northern and southern beams propagate respectively into the East Australian Current and the Antarctic Circumpolar Current and become undetectable to satellite altimetry. The central beam propagates across the Tasman Sea, impinges on the Tasmanian continental slope, and partially reflects. The observed propagation speeds agree well with theoretical values determined from climatological ocean stratification. Both the northern and central beams refract about 15° toward the equator because of the beta effect. Following a concave submarine ridge in the source region, the central beam first converges around 45.5°S, 155.5°E and then diverges beyond the focal region. The satellite results reveal two reflected internal tidal beams off the Tasmanian slope, consistent with previous numerical simulations and glider measurements. The total energy flux from the Macquarie Ridge into the Tasman Sea is about 2.2 GW, of which about half is contributed by the central beam. The central beam loses little energy in its first 1000-km propagation, for which the likely reasons include flat bottom topography and weak mesoscale eddies.

Spectrophotometrical researches of the subnuclear area of 46P/WIRTANEN comet

The observations and research of the short-period comet 46P/Wirtanen by optical spectra with an average resolution (λ/Δλ ≈ 1400) are presented. Spectra in January 2008 at the Peak Terskol mountain observatory with the Zeiss-2000 telescope (D = 2.0 m; F2 = 16 m) were obtained. On the basis of the received spectral material, the identification of emission bands was carried out. The distribution of the total energy flux, reflected energy flux and the spectrophotometric gradient in the spectral range λλ = 4850–7650 ÅÅ are constructed. The quality of the received spectral material allowed estimating with high accuracy the gas productivity of the molecules C2, NH2 and the relative dust productivity in cometary filters GC, RC. The relative dust productivity (Afρ), the gas productivity (Q) for the molecular emissions of C2 and NH2, as well as some other physical parameters of the neutral gas cometary atmosphere were evaluated. The resulting values of physical quantities are characteristic for Jupiter family comets. The gas productivity of 46P/Wirtanen during the observation period QC2 = 3.97–4.12 × 1025 mol/s, QNH2 = 2.06–2.97 × 1025 mol/s. The obtained values of gas and dust productivity characterize the cometary coma of 46P/Wirtanen as dust-rich. In comparison with the data of 1998, a significant decrease in production in the atmosphere of the comet of the NH2 molecule was recorded. The spectrophotometric gradient obtained for comet Wirtanen is characteristic for other JFC and is 8.6 % per 1000 Å. The relative dust productivity (Afρ) at the time of observations in January 2008 was significantly higher than in previous passages of perihelion. The obtained results may be the consequence of evolution of the upper layers of the cometary nucleus and require further experimental confirmation.

Internal wave generation by tidal flow over a two-dimensional ridge: energy flux asymmetries induced by a steady surface trapped current

The effects of a surface trapped steady background current on internal waves generated by tidal currents oscillating over a small symmetric ridge are investigated using a two-dimensional primitive equation model. A rigid lid is used with a linearly stratified fluid and the effects of rotation are not considered. We consider uni-directional background currents $\bar{U}(z)\geqslant 0$ confined to a surface layer lying well above the ridge. The current introduces asymmetries in the generated wave field. For sufficiently narrow ridges the upstream energy flux is larger than the downstream flux while the opposite is the case for sufficiently wide ridges. The total energy flux radiating away from the ridge is not significantly affected by the current. Mean second-order currents and pressure fields are shown to make important contributions to the total energy flux. A first-order linear theory, valid for a general stratification and surface current, which accurately predicts the wave field is also developed.