Testing the three-dimensional IRI-SIRMUP-P mapping of the ionosphere for disturbed periods

This paper describes the three-dimensional (3-D) electron density mapping of the ionosphere given as output by the assimilative IRI-SIRMUP-P (ISP) model for three different geomagnetic storms. Results of the 3-D model are shown by comparing the electron density profiles given by the model with the ones measured at two testing ionospheric stations: Roquetes (40.8°N, 0.5°E), Spain, and San Vito (40.6°N, 17.8°E), Italy. The reference ionospheric stations from which the autoscaled foF2 and M(3000)F2 data as well as the real-time vertical electron density profiles are assimilated by the ISP model are those of El Arenosillo (37.1°N, 353.3°E), Spain, Rome (41.8°N, 12.5°E), and Gibilmanna (37.9°N, 14.0°E), Italy. Overall, the representation of the ionosphere made by the ISP model is better than the climatological representation made by only the IRI-URSI and the IRI-CCIR models. However, there are few cases for which the assimilation of the autoscaled data from the reference stations causes either a strong underestimation or a strong overestimation of the real conditions of the ionosphere, which is in these cases better represented by only the IRI-URSI model. This ISP misrepresentation is mainly due to the fact that the reference ionospheric stations covering the region mapped by the model turn out to be few, especially for disturbed periods when the ionosphere is very variable both in time and in space and hence a larger number of stations would be required. The inclusion of new additional reference ionospheric stations could surely smooth out this concern.     

Seasonally steady planetary disturbances in the troposphere and stratosphere as seen in 30 years of NCEP reanalysis data

Zonal velocity and temperature daily global reanalysis data of 30 years are used to search seasonally steady planetary disturbances in the middle troposphere (400 hPa) and middle stratosphere (10 hPa). Significant wavenumber 1, 2 and 3 modes are found. Constant phase lines of zonal velocity 1 modes exhibit significant inclination angles with respect to the meridians. The winter hemisphere generally shows a more significant presence of structures. The Northern Hemisphere (NH) exhibits all over the year a larger amount of structures and more intense amplitudes than the Southern Hemisphere (SH). Middle latitudes exhibit the most significant cases and low latitudes the least significant ones. Longitudinally oriented land–sea transitions at ±$\pm$65° and −35° latitudes appear to play a significant role for the presence of steady planetary modes. The stratosphere exhibits a much simpler picture than the troposphere. Large scale structures with respectively NE–SW (NH) and NW–SE (SH) tilts in the observed temperature and zonal velocity constant phase lines recall the quasi-stationary Rossby wave trains that favor the poleward transport of angular momentum.     

Design and performance of a vacuum-UV simulator for material testing under space conditions

This paper describes the construction and performance of a VUV-simulator that has been designed to study degradation of materials under space conditions. It is part of the Complex Irradiation Facility at DLR in Bremen, Germany, that has been built for testing of material under irradiation in the complete UV-range as well as under proton and electron irradiation. Presently available UV-sources used for material tests do not allow the irradiation with wavelengths smaller than about 115 nm where common Deuterium lamps show an intensity cut-off. The VUV-simulator generates radiation by excitation of a gas-flow with an electron beam. The intensity of the radiation can be varied by manipulating the gas-flow and/or the electron beam.     

In situ analysis of Europa ices by short-range melting probes

A key aspect for understanding the astrobiological potential of planets and moons in the Solar system is the analysis of material embedded in or underneath icy layers on the surface. In particular in case of the icy crust of Jupiters moon Europa such investigation would be of greatest interest. For a Europa lander to be launched in the 2020–2030 timeframe, we propose to use a simplified instrumented melting probe which is able to access and sample depths of a few meters without the necessity of heavy and complicated drilling equipment.     

Spatial variation of the supersonic thermal plasma flow downstream of the termination shock

In this paper we start from the most recently observed fact that the solar wind plasma after passage over the termination shock is still supersonic with a Mach number of about 2. To explain this unexpected phenomenon and to predict the evolution of properties of the downstream plasma flow we here consider a two-fluid proton plasma with pick-up protons as a separate suprathermal, second proton fluid. We then formulate a self-consistent system of hydrodynamical conservation equations coupling the two fluids by dynamical and thermodynamical coupling terms and taking into account the effects of newly incorporated protons due to charge exchange with the H-atoms in the heliosheath. This then allows us to predict that in the most probable case the solar wind protons will become subsonic over a distance of about 30 AU downstream of the shock. As we can also show, it may, however, happen that the plasma mixture later again reconverts to a supersonic signature and has to undergo a second shock before meeting the heliopause.     

Response of Hainan GPS ionospheric scintillations to the different strong magnetic storm conditions

Using the GPS ionospheric scintillation data at Hainan station (19.5°N, 109.1°E) in the eastern Asia equatorial regions and relevant ionospheric and geomagnetic data from July 2003 to June 2005, we investigate the response of L-band ionospheric scintillation activity over this region to different strong magnetic storm conditions (Dst < −100 nT) during the descending phase of the solar cycle. These strong storms and corresponding scintillations mainly took place in winter and summer seasons. When the main phase developed rapidly and reached the maximum near 20–21 LT (LT = UT + 8) after sunset, scintillations might occur in the following recovery phase. When the main phase maximum occurred shortly after midnight near 01–02 LT, following the strong scintillations in the pre-midnight main phase, scintillations might also occur in the post-midnight recovery phase. When the main phase maximum took place after 03 LT to the early morning hours no any scintillation could be observed in the latter of the night. Moreover, when the main phase maximum occurred during the daytime hours, scintillations could also hardly be observed in the following nighttime recovery phase, which might last until the end of recovery phase. Occasionally, scintillations also took place in the initial phase of the storm. During those scintillations associated with the nighttime magnetic storms, the height of F layer base (h’F) was evidently increased. However, the increase of F layer base height does not always cause the occurrence of scintillations, which indicates the complex interaction of various disturbance processes in ionosphere and thermosphere systems during the storms.     

Spectroscopic analysis of the solar flare event on 2002 August 3 with the use of RHESSI and RESIK data

We use simultaneous observations from RESIK and RHESSI instruments to compare plasma properties of a major solar flare in its rise and gradual phase. This event occurred on 2002 August 3 (peak time at 19:06 UT). The flare had a very good coverage with RESIK data and well-resolved soft and hard X-ray sources were seen in RHESSI images. Spectra of X-ray radiation from RHESSI images are studied and compared with RESIK measurements in different flare phases. Result shows large differences in flare morphology and spectra between flare rise and gradual phase.     

Relative amplitude of the total electron content variations depending on geomagnetic activity

We developed a method of estimation of a relative amplitude dI/I of the total electron content (TEC) variations in the ionosphere as deduced from the data of the global GPS receivers network. To obtain statistically significant results we picked out three latitudinal belts provided in the Internet by the maximum number of GPS sites. They are high-latitudinal belt (50–80°N, 200–300°E; 59 sites), mid latitude belt (20–50°N, 200–300°E; 817 sites), and equatorial belt (±20°N, 0–360°E; 76 sites). The results of the analysis of the diurnal and latitudinal dependencies of dI/I and dI/I distribution probability for 52 days with different levels of geomagnetic activity are presented. It was found that on average the relative amplitude of the TEC variations varies within the range 0–10% proportionally to the value of the K_p geomagnetic index. In quiet conditions the relative amplitude dI/I of the TEC variations at night significantly exceeds the daytime relative amplitude. At high levels of magnetic field disturbances, the geomagnetic control of the amplitude of TEC variations at high and middle latitudes is much more significant than the regular diurnal variations. At the equatorial belt, on average, the amplitude of TEC variations in quiet and disturbed periods almost does not differ. The obtained results may be useful for development of the theory of ionospheric irregularities.     

Influence of the 27-day solar flux variations on the ionosphere parameters measured at Irkutsk in 2003–2005

We present an investigation of the influence of the 27-day solar flux variations, caused by solar rotation, on the ionosphere parameters such as the F2 layer critical frequency (foF2) and the total electron content (TEC). Our observational data were obtained with the Irkutsk Digisonde (DPS-4) located at 52.3 North and 104.3 East during the period from 2003 to 2005. In addition, we use TEC data from the Global Ionosphere Maps (GIM) based on Global Positioning System (GPS) satellites. The solar radiation flux at a wavelength of 10.7 cm (F10.7 index) is used as an index characterizing the solar activity level. A good correlation between observed ionosphere parameters and solar activity variations is found especially in autumn-to-winter season. We estimate the impact of the 27-day solar flux variations on the day-to-day variability and determine the time delay of the ionosphere response.