Observations of whistler-type echoes on signals of a ground VLF transmitter on board the ‘iterkosmos-19’ satellite

Signals of VLF transmitters of the Omega navigation system located in the auroral zone (66.4°N, 13.2°E, L= 5) were recorded by the VLF receiving equipment of the Interkosmos 19 satellite. Signals at frequencies between 10.2 and 13.6 kHz were received in a region above the transmitters, frequently with whistler-type echoes. An analysis of these echoes has shown their predominating occurrence in periods of low geomagnetic activity (Kp<2+). The occurrence region of these phenomena in the outer ionosphere has the dimension of about 1000 km and its position is betweenL= 2.5 and L= 4.4. The delay of echo-signals is practically the same during one satellite pass but its values for different satellite revolutions lie between 2.5 and 3.5 s. The frequency spectrum of these signals can be broadened up to 100 Hz. On the basis of calculations made, it can be shown that the experimental results are generally in accordance with the hypothesis of nonlinear ducting of VLF waves in the magnetosphere.     

Why does the total pressure on the subsolar magnetopause differ from the solar wind dynamic pressure?

Based on analysis of MHD equations and the results of numerical simulation in the magneto-sheath it is demonstrated that the total pressure on the magnetopause differs from the solar wind dynamic pressure in the majority of cases. From the equation of motion it follows that the total pressure is reduced due to deflection from the Sun-Earth line. At the same time, it increases because of formation of a magnetic barrier. This result is consistent with experimentally observed expansion of the magnetosphere for the radial direction of the interplanetary magnetic field, when no magnetic barrier is formed. In this paper we compare the behavior of pressure along the Sun-Earth line for the northward and radial interplanetary field, using the results of numerical MHD simulation and observational data from THEMIS. In the isotropic MHD approximation, the difference between the total pressure on the subsolar magnetopause at northern and radial IMFs does not exceed 10–12 percent. However, in the anisotropic approximation this difference increases up to 15–20 percent. The results of anisotropic modeling well agree with observed averaged profiles of pressure components in the subsolar magnetosheath.     

Updating the Local Model of the TEC during the Solar Eclipse on August 11, 1999

A total solar eclipse with the locations and times of the pass well-known in advance can be used to update the local model of the TEC for these particular circumstances. The observations using GPS receivers at the Warsaw and Borowiec stations and the ionosonde in Warsaw were analyzed in order to justify the results given by the IRI theoretical predictions. The IRI program with this updating creates a useful tool for preparation of the corrections for the process of network adjustment using the GPS technique and for navigation using single frequency receivers.     

Integrating local multi-criteria evaluation with spatially explicit uncertainty-sensitivity analysis

The conventional methods of Multi-Criteria Evaluation (MCE) fail to account for local variability in criteria values and criteria preferences, disregarding local influence in spatial decision making. Moreover, understanding the interaction between MCE model input and output has paramount importance in terms of the level of confidence in the model results and their subsequent use in decision making. This research contributes to spatial MCE methodology by articulating the presence of uncertainty included in criteria weights and extending a local MCE technique with a spatially explicit uncertainty and sensitivity analysis. The article presents a methodology for multi-criteria evaluation extended by an integrated uncertainty-sensitivity analysis and illustrates it on the example of a land prioritization model for conservation practices.     

Revisiting the Ariel Trough Work for HF Telecommunication Purposes

Muldrew [1] was the pioneer who reported the midlatitude electron density trough at the topside ionosphere. For about ten to fifteen years the trough, its morphology, dynamical behavior, relationship to the equatorial plasmapause, and physical and chemical processes which lead to the trough formation had been extensively investigated. Then, the work on the trough had been slowed down gradually. As the new space systems have become more vulnerable to space weather effects, a need for robust programs and a long track record in space environment sensing and modeling to produce new space environment models and products that would meet high-priority defense and commercial needs arises naturally. In this context, it is intended to go over the reported trough work dating back to the 1970s and some typical findings of later developments briefly. Most of the aspects of the trough studies have been repeated with new data for newer physical models. From this point of view, the Ariel 3 and Ariel 4 satellite trough results are chosen since the work on the Ariel trough had been very original and very extensive quantitatively and qualitatively in the 1970s. The results reviewed here are based on more than 1000 beautiful selected trough cases. Due to the good quality and quantity of the Ariel satellite data, equal coverage in space and time were maintained, which makes the trough results very important. This paper will end with some reference to the trough models, results that establish a link between the topside and the F2 region of the ionosphere. As one typical application, HF radiocommunication is chosen to be the point of interest. In practical applications of the HF radiocommunications any model that does not include the trough is not complete.     

Forecasting of the Total Electron Content at a Single Location

The autocovariance prediction method previously used for the forecast of VI derived ionospheric characteristics has been used for forecast of one of the most important ionospheric—the total electron content (TEC)—at single locations. Quiet and disturbed conditions at different European stations were studied in regard to clarify the forecasting capabilities of the method for determination of the TEC. The accuracies of the method achieved in dependence on the time range of the forecast are demonstrated.     

Ionospheric oscillations caused by geomagnetic Pi2 pulsations and their observations by multipoint continuous Doppler sounding; first results

In 2004, we started operating a continuous Doppler sounding system to investigate ionospheric signatures of infrasonic, short period acoustic gravity waves and geomagnetic pulsations. Since January 2007, four stable 3.59 MHz transmitters have been in operation in the western part of the Czech Republic. Multipoint measurements enable us to investigate horizontal propagation of waves and disturbances in the ionosphere and to estimate horizontal distances over which these waves (disturbances) are correlated.     

First laser measurements to space debris in Poland

The Borowiec Satellite Laser Ranging station (BORL 7811, Borowiec) being a part of the Space Research Centre of the Polish Academy of Sciences (SRC PAS) went through modernization in 2014–2015. One of the main tasks of the modernization was the installation of a high-energy laser module dedicated to space debris tracking. Surelite III by Continuum is a Nd:YAG pulse laser with 10?Hz repetition rate, a pulse width of 3–5?ns and a pulse energy of 450?mJ for green (532?nm). This new laser unit was integrated with the SLR system at Borowiec performing standard satellite tracking. In 2016 BORL 7811 participated actively to the observational campaigns related to the space debris targets from LEO region managed by the Space Debris Study Group (SDSG) of the International Laser Ranging Service (ILRS).Currently, Borowiec station regularly tracks 36 space debris from the LEO regime, including typical rocket bodies (Russian/Chinese) and cooperative targets like the inactive TOPEX/Poseidon, ENVISAT, OICETS and others. In this paper the first results of space debris laser measurements obtained by the Borowiec station in period August 2016 – January 2017 are presented. The results gained by the SRC PAS Borowiec station confirm the rotation of the defunct TOPEX/Poseidon satellite which spins with a period of approximately 10?s. The novelty of this work is the presentation of the sample results of the Chinese CZ-2C R/B target (NORAD catalogue number 31114) which is equipped (probably) with retroreflectors. Laser measurements to space debris is a very desirable topic for the next years, especially in the context of the Space Surveillance and Tracking (SST) activity. Some targets are very easy to track like defunct ENVISAT or TOPEX/Poseidon. On the other hand, there is a big population of different LEO targets with different orbital and physical parameters, which are challenging for laser ranging like small irregular debris and rocket boosters.     

Study of the NGC 2770 interstellar medium through Hα, millimetric and optical polarimetric data of SN 2008D and SN 2007uy

We present the preliminary results of the recent H_α narrow-band imaging carried out for NGC 2770 with the Gran Telescopio Canarias (GTC) equipped with OSIRIS. We put the polarization measurements reported in Gorosabel et al. (2010) for SN 2007uy and SN 2008D in the context of the morphological information inferred from the H_α imaging. We estimated the orientation of the interstellar polarization (ISP) at the position of SN 2007uy and, most interestingly, at the site of SN 2008D which has been subject of an intensive debate due to its possible connection with Gamma-Ray Bursts (GRBs). The H_α imaging reveals a clumpy interstellar medium (ISM) composed of hundreds of compact emitting regions, for which we determined their sizes. The derived size for the H_α emitting region coincident with SN 2008D is consistent with the ISM cell size limits imposed by Gorosabel et al. (2010) based on millimetric data. A deeper data analysis is under way and will be published elsewhere. This article represents the first attempt to study the site of a possible GRB-like event combining millimetric, polarimetric and narrow-band data.