Optical effects in the aurora caused by ionospheric HF heating

Ionospheric heating experiments were done by the EISCAT Heater in Tromsø on 15–19 November, 1993. A low-light TV camera was installed at the VLF receiving station at Porojärvi about 100 km to the south-east of Tromsø. The spectral analysis of the auroral luminosity variations showed that the brightness of the aurora varied at the modulation frequency of the heating wave. The results of this analysis and the numerical simulations of the auroral luminosity variations caused by the HF heating are shown. The variations of the optical emission intensity at the heating frequency occur during the auroral ionosphere modification. The observed intensity variation of the auroral green line during the interval of enhanced electron temperature is explained by a decreasing rate of the O₂⁺ ion dissociative recombination when the electron temperature increases. The brightness variation depends on the characteristic energy and the intensity of the auroral electron flux and the heating wave parameters. The artificial luminosity pulsations caused by HF heating are estimated.     

Observations of Near-Earth Optical Transients with the Lomonosov Space Observatory

The results of observations with the MASTER-SHOK robotic wide-field optical cameras onboard the Lomonosov Space Observatory carried out in 2016 are presented. In all, the automated transient detection system transmitted 22 181 images of moving objects with signal-to-noise ratios greater than 5 to the Earth. Approximately 84% of these images are identified with well-known artificial Earth satellites (including repeated images of the same satellite) and fragments of such satellites (space debris), according to databases of known satellites. The remaining 16% of the images are relate to uncatalogued objects. This first experience in optical space-based monitoring of near-Earth space demonstrates the high efficiency and great potential of using large-aperture cameras in space, based on the software and technology of the MASTER robotic optical complexes (the Mobile Astronomical System of TElescope- Robots (MASTER) global network of robotic telescopes of Lomonosov Moscow State University).     

Measurement of the turbulence in the free atmosphere above Mt. Ma\overset{\lower0.5em\hbox{danak

Stellar scintillations were measured at Mt. Ma $\overset{\lower0.5em\hbox{$\overset{\lower0.5em\hbox{ danak during 42 nights in 1998–1999 in order to estimate the contribution of the free atmosphere to the seeing. The atmosphere above 1–2 km provides a median seeing of _boxclose_boxclose 390\mathop .\limits^{'} 39 , which is about one-third of the total seeing ( 0\mathop .^" 700\mathop .\limits^{'} 70 ). The characteristic altitudes of turbulent layers are from 3 to 11 km above the summit, and the appearance of layers at altitudes of 3–4 km is accompanied by a degradation of the free-atmosphere seeing. The median isoplanatic angle is q₀ = 2\mathop .^" 30\theta _0 = 2\mathop .\limits^{'} 30 (λ=500 nm, at the zenith). This is the first time that such data have been obtained for Ma $\overset{\lower0.5em\hbox{$\overset{\lower0.5em\hbox{ danak. The instruments used for these measurements—a modified four-channel photometer and a prototype of a double-aperture scintillation sensor—are described in detail. The data reduction was based on accurate corrections for photon-counting statistics and the use of theoretical weighting functions relating scintillation indices to the altitudes and intensities of turbulent layers. Simultaneous or quasi-simultaneous measurements of scintillation indices using apertures of different sizes having significantly different weighting functions enable estimation of the altitude and intensity of the equivalent turbulent layer. Despite the simplicity of this one-layer model, it provides fairly robust estimates of the integrated parameters of the real free atmosphere.     

Robotic optical telescopes global network MASTER II. Equipment, structure, algorithms

Presented paper describes the basic principles and features of the implementation of a robotic network of optical telescopes MASTER, designed to study the prompt (simultaneous with gamma radiation) optical emission of gamma-ray bursts and to perform the sky survey to detect unknown objects and transient phenomena. With joint efforts of Sternberg astronomical institute, High altitude astronomical station of the Pulkovo observatory, Ural state university, Irkutsk state university, Blagoveshchensk pedagogical university, the robotic telescopes MASTER?II near Kislovodsk, Yekaterinburg, Irkutsk and Blagoveshchensk were installed and tested. The network spread over the longitudes is greater than 6?h. A further expansion of the network is considered.     

The Concept of a Multi-Functional Astronomy Complex and Dynamically Integrated Database Applied to Multi-Channel Observations with the MASTER Global Network

Astronomy Reports - The concept of a multi-functional astronomical complex as applied to robotic astronomy networks and systems is formulated. The practical realization of this concept in the...     

Electric and magnetic components of ballooning perturbations in the magnetotail plasma sheet before breakup

Using data from THEMIS spacecraft we investigated transverse to the magnetic field mutually perpendicular electric and magnetic components of ballooning type perturbations with periods 60–240 s, which are observed in the magnetospheric plasma sheet during the period preceding substorm onset. With applying Hilbert transform, we analyzed the phase relations between them. It is shown that the perturbations are dominated by radial electric and azimuthal magnetic (that is, toroidal) components which are usually in phase or out-of-phase. Along with them, approximately 2.5 times less intense azimuthal electric and radial magnetic components are present, which are more often phase-shifted by π/2. It is concluded that the observed perturbations are not a simple consequence of the development of plasma sheet ballooning instability, leading to the growth of strongly elongated along the magnetotail ballooning structures. It is pointed out that this conclusion is confirmed by simultaneous ground-based observations of magnetically conjugate auroral structures.     

Algorithmic recognition of anomalous time intervals in sea-level observations

The problem of the algorithmic recognition of anomalous time intervals in the time series of the sea-level observations conducted by the Russian Tsunami Warning Survey (RTWS) is considered. The normal and anomalous sea-level observations are described. The polyharmonic models describing the sea-level fluctuations on the short time intervals are constructed, and sea-level forecasting based on these models is suggested. The algorithm for the recognition of anomalous time intervals is developed and its work is tested on the real RTWS data.     

Spatial-temporal dynamics of auroras during the magnetic storm main phase

The structure and dynamics of auroras in the midnight sector during substorms, which develop during the magnetic storm main phase as compared to the characteristics of a typical auroral substorm, have been studied using the ground-based and satellite observations. It has been found out that a difference from the classical substorm is observed in auroras during the magnetic storm main phase. At the beginning of the storm main phase, the series of pseudobreakups with the most pronounced jump-like motion toward the equator shifts to lower latitudes. The substorm expansion phase can be observed not only as arc jumps to higher latitudes but also as an explosive expansion of a bright diffuse luminosity in all directions. During the magnetic storm main phase, auroras are mainly characterized by the presence of stable extensive rayed structures and by the simultaneous existence of different auroral forms, typical of different substorm phases, in the TV camera field of view.     

Measurements of optical turbulence in the free atmosphere above Mount Maidanak in 2005–2007

We present the results of our 2005–2007 campaign to measure the vertical distribution of optical turbulence above Mount Maidanak. The measurements were performed with the MASS instrument, a multi-aperture scintillation sensor that has been widely used for such studies in recent years at many observatories worldwide. Analysis of the data shows that the median seeing in the free atmosphere (at an altitude of 0.5 km and higher) is 0 ″46, while the isoplanatic angle is 2″.47. Given the large time constant (about 7 ms at good seeing), such conditions are favorable for using adaptive optics and interferometric measurements in the visible and near-infrared spectral ranges.     

Optical observations of gamma-ray bursts, the discovery of supernovae 2005bv, 2005ee, and 2006ak, and searches for transients using the “MASTER” robotic telescope

We present the results of observations obtained using the MASTER robotic telescope in 2005–2006, including the earliest observations of the optical emission of the gamma-ray bursts GRB 050824 and GRB 060926. Together with later observations, these data yield the brightness-variation law t ^?0.55±0.05 for GRB 050824. An optical flare was detected in GRB 060926—a brightness enhancement that repeated the behavior observed in the X-ray variations. The spectrum of GRB 060926 is found to be F _E ～ E ^?β , where β = 1.0 ± 0.2. Limits on the optical brightnesses of 26 gamma-ray bursts have been derived, 9 of these for the first time. Data for more than 90% of the accessible sky down to 19 ^m were taken and reduced in real time during the survey. A database has been composed based on these data. Limits have been placed on the rate of optical flares that are not associated with detected gamma-ray bursts, and on the opening angle for the beams of gamma-ray bursts. Three new supernovae have been discovered: SN 2005bv (type Ia)—the first to be discovered on Russian territory, SN 2005ee—one of the most powerful type II supernovae known, and SN 2006ak (type Ia). We have obtained an image of SN 2006X during the growth stage and a light curve that fully describes the brightness maximum and exponential decay. A new method for searching for optical transients of gamma-ray bursts detected using triangulation from various spacecraft is proposed and tested.