An investigation of ionospheric F region response in the Brazilian sector to the super geomagnetic storm of May 2005

In this paper, we have investigated the responses of the ionospheric F region at equatorial and low latitude regions in the Brazilian sector during the super geomagnetic storm on 15–16 May 2005. The geomagnetic storm reached a minimum Dst of −263 nT at 0900 UT on 15 May. In this paper, we present vertical total electron content (vTEC) and phase fluctuations (in TECU/min) from Global Positioning System (GPS) observations obtained at Belém, Brasília, Presidente Prudente, and Porto Alegre, Brazil, during the period 14–17 May 2005. Also, we present ionospheric parameters h’F, hpF2, and foF2, using the Canadian Advanced Digital Ionosonde (CADI) obtained at Palmas and São José dos Campos, Brazil, for the same period. The super geomagnetic storm has fast decrease in the Dst index soon after SSC at 0239 UT on 15 May. It is a good possibility of prompt penetration of electric field of magnetospheric origin resulting in uplifting of the F region. The vTEC observations show a trough at BELE and a crest above UEPP, soon after SSC, indicating strengthening of nighttime equatorial anomaly. During the daytime on 15 and 16 May, in the recovery phase, the variations in foF2 at SJC and the vTEC observations, particularly at BRAZ, UEPP, and POAL, show large positive ionospheric storm. There is ESF on the all nights at PAL, in the post-midnight (UT) sector, and phase fluctuations only on the night of 14–15 May at BRAZ, after the SSC. No phase fluctuations are observed at the equatorial station BELE and low latitude stations (BRAZ, UEPP, and POAL) at all other times. This indicates that the plasma bubbles are generated and confined on this magnetically disturbed night only up to the low magnetic latitude and drifted possibly to west.     

方柱-强旋组合旋涡脱落机制研究

强旋流和钝体绕流均可构造低速回流区以利于高速气体稳定燃烧,本文通过在钝体中心开孔通入旋流气体模拟研究了旋流流动对钝体绕流旋涡脱落的影响规律。计算结果表明,在旋流作用下,钝体绕流涡脱规律更加复杂,涡脱由上下边界层失稳主导变为由旋流管中的旋流涡主导,并且形成的涡尺度增大,在脱落过程中会由于旋涡的破碎产生"点潭"以增强周围涡强度。同时,柱体涡和旋流涡的相互作用可以减小流动阻力,增加回流区长度和回流质量流量,从而强化传热传质,起到强化燃烧增加燃烧稳定性的效果。     

Prevention of muscle fibers atrophy during gravitational unloading: The effect of l-arginine administration

Gravitational unloading results in pronounced atrophy of m.soleus. Probably, the output of NO is controlled by the muscle activity. We hypothesized that NO may be involved in the protein metabolism and increase of its concentration in muscle can prevent atrophic changes induced by gravitational unloading. In order to test the hypothesis we applied NO donor l-arginine during gravitational unloading. 2.5-month-old male Wistar rats weighing 220–230g were divided into sedentary control group (CTR, n=7), 14-day hindlimb suspension (HS, n=7), 14 days of hindlimb suspension+l-arginine (HSL, n=7) (with a daily supplementation of 500 mg/kg wt l-arginine) and 14 days of hindlimb suspension+l-NAME (HSN, n=7) (90 mg/kg wt during 14 days). Cross sectional area (CSA) of slow twitch (ST) and fast twitch (FT) soleus muscle fibers decreased by 45% and 28% in the HS group (p<0.05) and 40% and 25% in the HSN group, as compared to the CTR group (p<0.05), respectively. CSA of ST and FT muscle fibers were 25% and 16% larger in the HSL group in comparison with the HS group (p<0.05), respectively. The atrophy of FT muscle fibers in the HSL group was completely prevented since FT fiber CSA had no significant differences from the CTR group. In HS group, the percentage of fibers revealing either gaps/disruption of the dystrophin layer of the myofiber surface membrane increased by 27% and 17%, respectively, as compared to the controls (CTR group, p<0.05). The destructions in dystrophin layer integrity and reductions of desmin content were significantly prevented in HSL group. NO concentration decreased by 60% in the HS group (as well as HSN group) and at the same time no changes were detectable in the HSL group. This fact indicates the compensation of NO content in the unloaded muscle under l-arginine administration. The levels of atrogin-1 mRNA were considerably altered in suspended animals (HS group: plus 27%, HSL group: minus 13%) as compared to the control level. Conclusion: l-arginine administration allows maintaining NO concentration in m.soleus at the level of cage control group, prevents from dystrophin layer destruction, decreases the atrogin mRNA concentration in the muscle and atrophy level under gravitational unloading.     

GRAS radio occultation on-board of Metop

The GRAS radio occultation instrument is flying on Metop-A and belongs to the EPS (EUMETSAT Polar System). GRAS observes GPS satellites in occultation. Within this work, validation of GRAS closed-loop bending angle data against co-located ECMWF profiles extracted from model fields and occultations from the COSMIC constellation of radio occultation instruments is shown. Results confirm the high data quality and robustness, where GRAS shows lower bending angle noise against ECMWF than COSMIC and in terms of occultations per day, one GRAS ≈ two COSMIC satellites. This is partly due to the operational setup of EPS. For the investigation we focus on two observation periods where updates in the ECMWF (March 2009) and COSMIC processing (October 2009) have improved the statistics further. Bending angles biases agree to within 0.5% against ECMWF and to within 0.1% against COSMIC after the updates for altitudes between 8 and 40 km. In addition, we also analyze the impact of the Metop orbit processing on the derived GRAS bending angle data, where different GPS and Metop orbit solutions are analyzed. Results show that a batch based orbit processing would improve in particular the bending angle bias behavior at higher altitudes. Requirements for the operational processing of GRAS data are briefly outlined, options to ease the use of other positioning system satellites in the near future are discussed. A simplified analysis on the observation of several of these systems, e.g. GPS and Galileo, from one platform shows that about 16% of occultations are found within 300 km, ±3 h, thus providing similar information. A constellation of 2 GRAS like instruments would have only about 10% close-by.     

Solar system planets observed with Suzaku

Recent results of solar system planets observed with the Japanese X-ray astronomy satellite Suzaku are reviewed. Thanks to the low instrumental background and good energy resolution, X-ray CCDs onboard Suzaku are one of the best probes to study diffuse X-ray emission. An overview of the Suzaku data of Jupiter and Earth is presented, along with preliminary results of Mars. Firstly, diffuse hard X-ray emission is discovered in 1–5 keV at Jovian radiation belts. Its spectrum is represented by a power-law continuum with a photon index of ∼1.4. This emission could originate from inverse-Compton scattering of solar photons by tens MeV electrons. Secondly, variable diffuse soft X-rays are serendipitously found during observations in the directions of the north ecliptic pole and galactic ridge. Good time correlations with the solar wind and emission lines found in the X-ray spectra are firm evidences of a solar wind charge exchange emission with Earth’s exosphere. Thirdly, diffuse X-ray emission from Martian exosphere via the solar wind charge exchange is investigated for the first time at solar minimum. A stringent upper limit on the density of the Martian exosphere is placed from the Suzaku data.     

Lunar exosphere influence on lunar-based near-ultraviolet astronomical observations

The potential effect of the lunar exosphere on the near-ultraviolet sky background emission is predicted for Lunar-based Ultraviolet Telescope (LUT: a funded Chinese scientific payload for the Chang’e-III mission). Using the upper limit on the OH concentration inferred from the recent MIP CHACE results, our calculations show that the sky brightness due to the illuminated exosphere is <8.7 photons⁻¹ cm⁻² arcsec⁻² within the wavelength range 245–340 nm. By evaluating the signal-to-noise ratios of observations of an AB = 13 mag point source at a series of sky background levels, our analysis indicates that the detection performance of LUT can be moderately degraded by the lunar exosphere emission in most cases. An AB = 13 mag point source can still be detected by the telescope at a signal-to-noise ratio more than 8 when the OH concentration is less than 2 × 10⁸ molecules cm⁻³. However, the effect on the performance is considerable when the exosphere is as dense as suggested by CHACE.     

Warm and Hot Gas in the Local ISM

I present a short review of the physical properties and relationships between warm partially ionized and hot and highly ionized gas in the local interstellar-medium (ISM). The majority of the measurements reviewed have been obtained through ultraviolet absorption spectroscopy recorded towards stellar targets located within ～150 pc of the Sun. Many questions still remain to be answered concerning the location, temperature, density and source of ionization of both of these phases of the diffuse interstellar gas. In particular, we focus on absorption observations of the ions of C IV λ 1550 Å and Si IV λ 1394 Å and discuss if highly ionized gas (as traced by the O VI λ 1032 Å ion) has in fact actually been detected within the Local Cavity.     

Emitter number estimation from pulse trains using the GIC

An information theoretic criterion based approach for estimating the number of emitters from a set of interleaved pulse trains is proposed. In the approach, a new pulse signal model is formulated to handle large number of pulses. The approach is based on the application of the general information criteria (GIC) and has the advantage of not requiring any threshold setting procedures. When compared with classical information theoretic criterion based approaches, the GIC-based approach is more flexible, and it does not involve any computationally sophisticated maximum likelihood estimator. Computer simulations are used to demonstrate the effectiveness of the proposed approach.     

Sliding mode control of the space nuclear reactor system

The automatic control system (ACS) of the space nuclear reactor power system TOPAZ II that generates electricity from nuclear heat using in-core thermionic converters is considered. Sliding mode control technique is applied to the reactor system controller design in order to improve robustness and accuracy of tracking of a thermal power reference profile in a start-up regime and a payload current reference profile in an operation regime. Extensive simulations of the TOPAZ II reactor system with the designed sliding mode controller showed an improvement of the reactor system performance     

Imaging spectroscopy of the Venus 1.27-μm O2 airglow with ground-based telescopes

Several ground-based observations of the Venus 1.27-μm O₂ airglow were carried out from 2002 to 2005. Spectral image cubes were taken with the Okayama Astrophysical Observatory/infrared imaging spectrometer (superOASIS), the Gunma Astronomical Observatory/Cassegrain Near-Infrared Camera and NASA’s Infrared Telescope Facility/cryogenic echelle spectrograph (CSHELL). The brightest airglow features were found at around the anti-solar point, which is in agreement with previous studies. We derived the rotational temperature distributions on the nightside hemisphere from observed airglow spectra. The temperature shows a weak positive correlation with the airglow intensity. The result indicates the bright region is heated chemically and/or dynamically, and supports the existing scenario for the Venus O₂ airglow. That is, the airglow is excited by the descending oxygen transported from the dayside.