Experimental study of radial temperature gradient-reducing devices in GTE rotor disks

In this paper, we examine experimentally some devices the principle of action of which is based on using the dynamic pressure of air extracted to engine cooling and which are meant for reducing the radial temperature gradient in GTE rotor disks. We established that the devices equipped with the ejector channels make it possible to accelerate the process of the disk hub heating by hot air suction from the cavity periphery towards the rotor axis of rotation. Using the data of visualization studies, we show the possibility for efficient operation of ejector devices in the conditions of real GTE rotor circumferential velocities.     

The Solar Wind Charge-eXchange Contribution to the Local Soft X-ray Background

The major sources of the Soft X-ray Background (SXRB), besides distinct structures as supernovae and superbubbles (e.g. Loop I), are: (i) an absorbed extragalactic emission following a power law, (ii) an absorbed thermal component (～2×10⁶ K) from the galactic disk and halo, (iii) an unabsorbed thermal component, supposedly at 10⁶ K, attributed to the Local Bubble and (iv) the very recently identified unabsorbed Solar Wind Charge-eXchange (SWCX) emission from the heliosphere and the geocorona. We study the SWCX heliospheric component and its contribution to observed data. In a first part, we apply a SWCX heliospheric simulation to model the oxygen lines (3/4 keV) local intensities during shadowing observations of the MBM 12 molecular cloud and a dense filament in the south galactic hemisphere with Chandra, XMM-Newton, and Suzaku telescopes. In a second part, we present a preliminary comparison of SWCX model results with ROSAT and Wisconsin surveys data in the 1/4 keV band. We conclude that, in the 3/4 keV band, the total local intensity is entirely heliospheric, while in the 1/4 keV band, the heliospheric component seems to contribute significantly to the local SXRB intensity and has potentially a strong influence on the interpretation of the ROSAT and Wisconsin surveys data in terms of Local Bubble hot gas temperature.     

Qualitative estimation of magnetic storm efficiency in producing relativistic electron flux in the Earth’s outer radiation belt using geomagnetic pulsations data

It is well known that during many but not all of the geomagnetic storms enhanced fluxes of high-energy electrons are observed in the outer radiation belt. Here we examine relativistic (>2 MeV) electron fluxes measured by GOES at the synchronous orbit and on-ground observations of two types of ULF pulsations during 30 magnetic storms occurred during 1996–2000. To characterize the effectiveness of the chosen magnetic storms in producing relativistic electron fluxes, following to (Reeves, G.D., McAdams, K.L., Friedel, R.H.W., O’Brien, T.R. Acceleration and loss of relativistic electrons during geomagnetic storms. Geophys. Res. Lett. 30, doi:10.1029/2002GL016513, 2003), we calculate a ratio of the maximum daily-averaged electron flux measured during the recovery phase, to the mean pre-storm electron flux. A storm is considered an effective one if its ratio exceeds 2. We compare behavior of Pi1 and Pc5 geomagnetic pulsations during effective and non-effective storms and find a tendency for a storm efficiency to be higher when the mid-latitude Pi1 pulsations are observed for a long time during the magnetic storm main phase. We note also that the prolonged powerful Pc5 pulsation activity during the recovery phase of a magnetic storm is the necessary condition for the storm effectiveness. To interpret the found dependences, we suggest that there are two prerequisites for generating relativistic electron populations during a storm: (1) the availability of seed electrons in the magnetosphere, and Pi1 emissions are indicators of the mid-energy electron interaction with the ionosphere and (2) acceleration of the seed electrons to MeV energies, and interaction of electrons with the MHD wave activity in the Pc5 range is one of the most probable mechanisms proposed in the literature for this purpose.     

Mid-Latitude Pc1, 2 Pulsations Induced by Magnetospheric Compression in the Maximum and Early Recovery Phase of Geomagnetic Storms

We investigate the properties of interplanetary inhomogeneities generating long-lasting mid-latitude Pc1, 2 geomagnetic pulsations. The data from the Wind and IMP 8 spacecrafts, and from the Mondy and Borok midlatitude magnetic observatories are used in this study. The pulsations under investigation develop in the maximum and early recovery phase of magnetic storms. The pulsations have amplitudes from a few tens to several hundred pT andlast more than seven hours. A close association of the increase (decrease) in solar wind dynamic pressure (Psw) with the onset or enhancement (attenuation or decay) of these pulsations has been established. Contrary to high-latitude phenomena, there is a distinctive feature of the interplanetary inhomogeneities that are responsible for generation of long-lasting mid-latitude Pc1, 2. It is essential that the effect of the quasi-stationary negative Bz-component of the interplanetary magnetic field on the magnetosphere extends over 4 hours. Only then are the Psw pulses able to excite the above-mentioned type of mid-latitude geomagnetic pulsations. Model calculations show that in the cases under study the plasmapause can form in the vicinity of the magnetic observatory. This implies that the existence of an intense ring current resulting from the enhanced magnetospheric convection is necessary for the Pc1, 2 excitation. Further, the existence of the plasmapause above the observation point (as a waveguide) is necessary for long-lasting Pc1 waves to arrive at the ground.