scholarly journals AC and DC global electric circuit properties and the height profile of atmospheric conductivity

2016 ◽  
Vol 59 (5) ◽  
Author(s):  
Irina G. Kudintseva ◽  
Alexander P. Nickolaenko ◽  
Michael J. Rycroft ◽  
Anna Odzimek
Keyword(s):  
Gamma Ray ◽  
Middle Atmosphere ◽  
Electric Circuit ◽  
Height Profile ◽  
Full Wave ◽  
D Region ◽  
Order Of Magnitude ◽  
Atmospheric Conductivity ◽  
Physical Reasons ◽  
Meteoric Material

An apparent discrepancy is pointed out - at all heights, and by up to an order of magnitude - between the height profiles of atmospheric conductivity derived at AC using ELF propagation studies, especially from information on Schumann resonance of the Earth-ionosphere cavity, and using a model of the DC global atmospheric electric circuit. This serious issue is resolved by creating a hybrid profile of these two mid-latitude profiles, the first of which refers to conditions by day and the second by night. This hybrid profile is thus a first order attempt to represent globally averaged conditions. Close to the Earth’s surface, where the resistance of the atmosphere is largest, the properties of the DC global model exert the greatest influence, whereas in the middle atmosphere, at heights between 40 and 100 km, full wave computations show that the AC results are the more crucial. The globally averaged hybrid profile presented here has some limitations, and the physical reasons for these are addressed. They are due to the presence of aerosol particles of ice and/or of meteoric material which reduce the ionospheric D-region conductivity by an order of magnitude over only ~2 km of height, thereby causing ledges of ionisation. In the context of the globally averaged profile, published observations of the ionospheric effects of the giant gamma-ray flare from SGR 1806-20 (a neutron star having an enormously large magnetic field) occurring at 21:30 U.T. on December 27, 2004, are briefly discussed.

scholarly journals Constraints on Lorentz Invariance Violation with Multiwavelength Polarized Astrophysical Sources

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 44
Author(s):  
Qi-Qi Zhou ◽  
Shuang-Xi Yi ◽  
Jun-Jie Wei ◽  
Xue-Feng Wu
Keyword(s):  
Gamma Ray ◽  
Lorentz Invariance ◽  
Polarized Light ◽  
Polarization Plane ◽  
Polarization Angle ◽  
Intrinsic Polarization ◽  
Frequency Dependent ◽  
Invariance Violation ◽  
Linearly Polarized ◽  
Order Of Magnitude

Possible violations of Lorentz invariance (LIV) can produce vacuum birefringence, which results in a frequency-dependent rotation of the polarization plane of linearly polarized light from distant sources. In this paper, we try to search for a frequency-dependent change of the linear polarization angle arising from vacuum birefringence in the spectropolarimetric data of astrophysical sources. We collect five blazars with multiwavelength polarization measurements in different optical bands (UBVRI). Taking into account the observed polarization angle contributions from both the intrinsic polarization angle and the rotation angle induced by LIV, and assuming that the intrinsic polarization angle is an unknown constant, we obtain new constraints on LIV by directly fitting the multiwavelength polarimetric data of the five blazars. Here, we show that the birefringence parameter η quantifying the broken degree of Lorentz invariance is limited to be in the range of −9.63×10−8<η<6.55×10−6 at the 2σ confidence level, which is as good as or represents one order of magnitude improvement over the results previously obtained from ultraviolet/optical polarization observations. Much stronger limits can be obtained by future multiwavelength observations in the gamma-ray energy band.

scholarly journals The Electrical Activity of Saharan Dust as perceived from Surface Electric Field Observations in Greece

2020 ◽  
Author(s):  
Vasiliki Daskalopoulou ◽  
Sotirios A. Mallios ◽  
Zbigniew Ulanowski ◽  
George Hloupis ◽  
Anna Gialitaki ◽  
...  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Field Enhancement ◽  
Electric Circuit ◽  
Saharan Dust ◽  
Backscatter Coefficient ◽  
Lidar System ◽  
Realistic Description ◽  
Atmospheric Conductivity

Abstract. We report on the electric field variations during Saharan dust advection over two atmospheric remote stations in Greece, using synergistic observations of the vertical atmospheric electric field strength (Ez) at ground and the lidar-derived particle backscatter coefficient profiles. Both parameters were monitored for the first time with the simultaneous deployment of a ground-based field mill electrometer and a multiwavelength lidar system. The field mill timeseries are processed to extract the diurnal variations of the Global Electric Circuit and remove fast field perturbations due to peak lightning activity. In order to identify the influence of the elevated dust layers on the ground Ez, we extract a Localized Reference Electric Field from the timeseries that reflects the local fair weather activity. Then, we compare it with the reconstructed daily average behaviour of the electric field and the Saharan dust layers' evolution, as depicted by the lidar system. Reported cases of enhanced vertical electric field for detached pure dust layers suggest the presence of in-layer electric charges. Although higher dust loads are expected to result in electric field enhancement, episodic cases that reduce the electric field are also observed. To quantitatively approach our results, we examine the dependency of Ez against theoretical assumptions for the distribution of separated charges within the electrified dust layer. Electrically neutral dust is approximated by atmospheric conductivity reduction, while charge separation areas within electrically active dust layers are approximated as finite extent cylinders. This physical approximation constitutes a more realistic description of the distribution of charges, as opposed to infinite extent geometries, and allows for analytical solutions of the electric field strength, so that observed electric field variations during the monitored dust outbreaks can be explained.

scholarly journals Improvements to a long-term Rayleigh-scatter lidar temperature climatology by using an optimal estimation method

2018 ◽  
Vol 11 (11) ◽  
pp. 6043-6058 ◽  
Author(s):  
Ali Jalali ◽  
Robert J. Sica ◽  
Alexander Haefele
Keyword(s):  
Traditional Method ◽  
Middle Atmosphere ◽  
Density Measurement ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Temperature Profiles ◽  
Vertical Resolution ◽  
Order Of Magnitude ◽  
Lidar Equation ◽  
Model Temperature

Abstract. Hauchecorne and Chanin (1980) developed a robust method to calculate middle-atmosphere temperature profiles using measurements from Rayleigh-scatter lidars. This traditional method has been successfully used to greatly improve our understanding of middle-atmospheric dynamics, but the method has some shortcomings regarding the calculation of systematic uncertainties and the vertical resolution of the retrieval. Sica and Haefele (2015) have shown that the optimal estimation method (OEM) addresses these shortcomings and allows temperatures to be retrieved with confidence over a greater range of heights than the traditional method. We have calculated a temperature climatology from 519 nights of Purple Crow Lidar Rayleigh-scatter measurements using an OEM. Our OEM retrieval is a first-principle retrieval in which the forward model is the lidar equation and the measurements are the level-0 count returns. It includes a quantitative determination of the top altitude of the retrieved temperature profiles, the evaluation of nine systematic plus random uncertainties, and the vertical resolution of the retrieval on a profile-by-profile basis. Our OEM retrieval allows for the vertical resolution to vary with height, extending the retrieval in altitude 5 to 10 km higher than the traditional method. It also allows the comparison of the traditional method's sensitivity to two in-principle equivalent methods of specifying the seed pressure: using a model pressure seed versus using a model temperature combined with the lidar's density measurement to calculate the seed pressure. We found that the seed pressure method is superior to using a model temperature combined with the lidar-derived density. The increased altitude capability of our OEM retrievals allows for a comparison of the Rayleigh-scatter lidar temperatures throughout the entire altitude range of the sodium lidar temperature measurements. Our OEM-derived Rayleigh temperatures are shown to have improved agreement relative to our previous comparisons using the traditional method, and the agreement of the OEM-derived temperatures is the same as the agreement between existing sodium lidar temperature climatologies. This detailed study of the calculation of the new Purple Crow Lidar temperature climatology using the OEM establishes that it is both highly advantageous and practical to reprocess existing Rayleigh-scatter lidar measurements that cover long time periods, during which time the lidar may have undergone several significant equipment upgrades, while gaining an upper limit to useful temperature retrievals equivalent to an order of magnitude increase in power-aperture product due to the use of an OEM.

scholarly journals Neutron Star Mergers, Disks Around Black Holes, and Gamma-Ray Bursts

1997 ◽  
Vol 163 ◽  
pp. 384-387 ◽  
Author(s):  
H.-Th. Janka ◽  
M. Ruffert
Keyword(s):  
Neutron Stars ◽  
Energy Deposition ◽  
Gamma Ray ◽  
Three Dimensional ◽  
Energy Output ◽  
Central Black Hole ◽  
Order Of Magnitude ◽  
Hydrodynamical Simulations ◽  
Piecewise Parabolic ◽  
Favorable Conditions

AbstractWe have performed three-dimensional hydrodynamical simulations of the coalescence of binary neutron stars taking into account the emission and backreaction of gravitational waves in the Newtonian code based on the “Piecewise Parabolic Method”. The use of the physical equation of state (EOS) of Lattimer & Swesty (1991) allowed us to calculate the production of neutrinos. We evaluated our models for the efficiency of v⊽ annihilation in the surroundings of the coalescing neutron stars. The corresponding energy deposition prior to and during merging turned out to be 2–3 orders of magnitude too small to power a typical γ-ray burst (GRB) with an energy output of ~ (1051/4π) erg/sterad at cosmological distances. Analytical estimates of the subsequent evolution of the disk which possibly surrounds the central black hole showed that even under the most favorable conditions the energy provided by v⊽ → e−e+ → γγ falls short by at least an order of magnitude. We discuss the implications of our results and speculate about possibilities how v⊽ annihilation might still be a viable energy source for GRBs.

scholarly journals Time-Domain Astronomy with Swift, Fermi and Lobster

2011 ◽  
Vol 7 (S285) ◽  
pp. 41-46 ◽  
Author(s):  
Neil Gehrels ◽  
Scott D. Barthelmy ◽  
John K. Cannizzo
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Tidal Disruption ◽  
X Ray ◽  
Order Of Magnitude ◽  
New Type ◽  
The Crab Nebula ◽  
High Energy Emission ◽  
Higher Sensitivity

AbstractThe dynamic transient gamma-ray sky is revealing many interesting results, largely due to findings by Fermi and Swift. The list includes new twists on gamma-ray bursts (GRBs), a GeV flare from a symbiotic star, GeV flares from the Crab Nebula, high-energy emission from novae and supernovae, and, within the last year, a new type of object discovered by Swift—a jetted tidal disruption event. In this review we present highlights of these exciting discoveries. A new mission concept called Lobster is also described; it would monitor the X-ray sky at order-of-magnitude higher sensitivity than current missions can.

scholarly journals Experimental study of H<sub>2</sub>SO<sub>4</sub> aerosol nucleation at high ionization levels

2018 ◽  
Vol 18 (8) ◽  
pp. 5921-5930 ◽  
Author(s):  
Maja Tomicic ◽  
Martin Bødker Enghoff ◽  
Henrik Svensmark
Keyword(s):  
Sulfuric Acid ◽  
Gamma Ray ◽  
Reaction Chamber ◽  
Critical Cluster ◽  
H2so4 Concentration ◽  
Ion Concentrations ◽  
High Ionization ◽  
Direct Measurements ◽  
Mobility Diameter ◽  
Order Of Magnitude

Abstract. One hundred and ten direct measurements of aerosol nucleation rate at high ionization levels were performed in an 8 m3 reaction chamber. Neutral and ion-induced particle formation from sulfuric acid (H2SO4) was studied as a function of ionization and H2SO4 concentration. Other species that could have participated in the nucleation, such as NH3 or organic compounds, were not measured but assumed constant, and the concentration was estimated based on the parameterization by Gordon et al. (2017). Our parameter space is thus [H2SO4] =4×106-3×107 cm−3, [NH3+ org] = 2.2 ppb, T=295 K, RH = 38 %, and ion concentrations of 1700–19 000 cm−3. The ion concentrations, which correspond to levels caused by a nearby supernova, were achieved with gamma ray sources. Nucleation rates were directly measured with a particle size magnifier (PSM Airmodus A10) at a size close to critical cluster size (mobility diameter of ∼ 1.4 nm) and formation rates at a mobility diameter of ∼ 4 nm were measured with a CPC (TSI model 3775). The measurements show that nucleation increases by around an order of magnitude when the ionization increases from background to supernova levels under fixed gas conditions. The results expand the parameterization presented in Dunne et al. (2016) and Gordon et al. (2017) (for [NH3+org] = 2.2 ppb and T=295 K) to lower sulfuric acid concentrations and higher ion concentrations. The results make it possible to expand the parameterization presented in Dunne et al. (2016) and Gordon et al. (2017) to higher ionization levels.

scholarly journals The initial evolution of millisecond magnetars: an analytical solution

2020 ◽  
Vol 496 (2) ◽  
pp. 2183-2190
Author(s):  
S Çıkıntoğlu ◽  
S Şaşmaz Muş ◽  
K Yavuz Ekşi
Keyword(s):  
Dipole Moment ◽  
Analytical Solution ◽  
Magnetic Dipole ◽  
Inclination Angle ◽  
Magnetic Dipole Moment ◽  
Gamma Ray ◽  
Plateau Phase ◽  
Central Engine ◽  
Initial Evolution ◽  
Order Of Magnitude

ABSTRACT Millisecond magnetars are often invoked as the central engine of some gamma-ray bursts (GRBs), specifically the ones showing a plateau phase. We argue that an apparent plateau phase may not be realized if the magnetic field of the nascent magnetar is in a transient rapid decay stage. Some GRBs that lack a clear plateau phase may also be hosting millisecond magnetars. We present an approximate analytical solution of the coupled set of equations describing the evolution of the angular velocity and the inclination angle between rotation and magnetic axes of a neutron star in the presence of a corotating plasma. We also show how the solution can be generalized to the case of evolving magnetic fields. We determine the evolution of the spin period, inclination angle, magnetic dipole moment, and braking index of six putative magnetars associated with GRB 091018, GRB 070318, GRB 080430, GRB 090618, GRB 110715A, and GRB 140206A through fitting, via Bayesian analysis, the X-ray afterglow light curves by using our recent model. We find that within the first day following the formation of the millisecond magnetar, the inclination angle aligns rapidly, the magnetic dipole moment may decay by a few times, and the braking index varies by an order of magnitude.

Future prospects for y-ray astronomy

1981 ◽  
Vol 301 (1462) ◽  
pp. 693-701 ◽  
Keyword(s):  
Gamma Ray ◽  
Dynamic Pressure ◽  
High Energy ◽  
Compact Objects ◽  
Pressure Effects ◽  
Very High Energy ◽  
Order Of Magnitude ◽  
High Energy Particles ◽  
Nuclear Processes ◽  
The Universe

As y-ray astronomy moves from the discovery to the exploratory phase, the promise of y-ray astrophysics noted by theorists in the late 1940s and 1950s is beginning to be realized. In the future, satellites should carry instruments that will have over an order of magnitude greater sensitivity than those flown thus far, and, for at least some portions of the y-ray energy range, these detectors will also have substantially improved energy and angular resolution. The information to be obtained from these experiments should greatly enhance our knowledge of several astrophysical phenomena including the very energetic and nuclear processes associated with compact objects, astrophysical nucleosynthesis, solar particle acceleration, the chemical composition of the planets and other bodies of the Solar System, the structure of our Galaxy, the origin and dynamic pressure effects of the cosmic rays, high energy particles and energetic processes in other galaxies especially active ones, and the degree of matter-antimatter symmetry of the Universe. The y-ray results of the forthcoming programs such as Gamma-I, the Gamma Ray Observatory, the y-ray burst network, Solar Polar, and very high energy y-ray telescopes on the ground will almost certainly provide justification for more sophisticated telescopes. These advanced instruments might be placed on the Space Platform currently under study by N.A.S.A.

scholarly journals Statistical signature of active D-region HF heating in IRIS riometer data from 1994–2004

2007 ◽  
Vol 25 (2) ◽  
pp. 407-415 ◽  
Author(s):  
A. Kero ◽  
C.-F. Enell ◽  
Th. Ulich ◽  
E. Turunen ◽  
M. T. Rietveld ◽  
...  
Keyword(s):  
Present Theory ◽  
Cosmic Radio ◽  
Radio Noise ◽  
3 Dimensional ◽  
Noise Absorption ◽  
D Region ◽  
Order Of Magnitude ◽  
Representative Model ◽  
Vertical Beam ◽  
Hf Heating

Abstract. In this paper we study the effect of artificial HF heating on cosmic radio noise absorption in the D-region ionosphere. The effect has earlier been studied theoretically in idealised cases and without experimental verification. Here we present a 3-dimensional modelling of the effect, taking into account the directivity patterns of the vertical beam of the EISCAT Heater at Tromsø, Norway, and the intersecting beam of the IRIS imaging riometer at Kilpisjärvi, Finland. The heater-induced enhancement of cosmic radio noise absorption at the IRIS frequency (38.2 MHz) is estimated to be between 0.02 dB and 0.05 dB in the most representative model cases. However, a statistical study of IRIS data from a selected set of heating experiments carried out during the years 1994–2004 shows that the median effect is between 0.002 dB and 0.004 dB, i.e. an order of magnitude less than theoretically predicted. This indicates that the actual HF heating effect at D-region altitudes is substantially overestimated by the present theory.

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