The elemental composition in energetic particle events at high heliospheric latitudes

The relative abundances of low energy ions (0.6–2.0 MeV/n) in solar energetic particle (SEP) and corotating interaction region (CIR) events have been measured by the EPAC experiment aboard Ulysses since launch in October 1990 until the present time. We give an overview of the abundances of heavy ions (He, C, Ne, Fe) relative to oxygen during energetic particle events lasting longer than 5 days during the in- and out-of-ecliptic phase of the mission. While the period Oct. 1990 to Aug. 1992 was dominated by high solar activity the Ulysses out of ecliptic passage at solar latitudes up to 45° went parallel to the declining phase of solar activity. Thus a very clear structure of corotating interaction regions was observed. While the in-ecliptic composition is in general agreement with measurements made near the Earth, the development of the CIR-composition shows two phases: From Aug. 1992 to May 1993 the C/O-ratio is 0.55–0.70, afterwards it increases to 0.8–0.9. This increase is correlated to the disappearance of the current sheet at 30° solar latitude reported by Smithet al. (1993).     

Using Precise Solar Limb Shape Measurements to Study the Solar Cycle

Despite 20 years of total solar irradiance measurements from space, the lack of high precision spatially resolved observations limits definitive answers to even simple questions like ``Are the solar irradiance changes caused solely by magnetic fields perturbing the radiative flux at the photosphere?" More subtle questions like how the aspheric structure of the sun changes with the magnetic cycle are only now beginning to be addressed with new tools like p-mode helioseismology. Solar 5-min oscillation studies have yielded precise information on the mean radial interior solar structure and some knowledge about the rotational and thermal solar asphericity. Unfortunately this progress has not been enough to generate a self-consistent theory for why the solar irradiance and luminosity vary with the magnetic cycle. We need sharper tools to describe and understand the sun's global aspheric response to its internal dynamo, and we need to be able to measure the solar cycle manifestation of the magnetic cycle on entropy transport from the interior to the photosphere in much the same way that we study the fundamentally more complex problem of magnetic flux transport from the solar interior. A space experiment called the Solar Physics Explorer for Radius, Irradiance and Shape (SPHERIS) and in particular its Astrometric and Photometric Telescope (APT) component will accomplish these goals.

     

Determination of aerosol optical depth from ground measurements

The methods used to determine the aerosol optical depth as a function of wavelength are briefly described and discussed. Some results from the operational network of the World Meteorological Organization and other, more research oriented studies, are reviewed and critically analysed to assess the reliability and accuracy of such determinations and their value as ground truth measurements for space applications.     

Energetic particle observations at high heliographic latitudes

Energetic particles, accelerated in shocks which were associated with recurrent fast solar wind streams, were observed in high heliographic latitudes; fifteen such steams were included in the present study. Intensity variations ranged up to four orders of magnitude. Energy spectra were typically steeper near forward shocks than near reverse shocks. Electrons were observed only lated to the reverse shocks. Composition ratios in accelerated streams resembled those observed in fast CIR's. In periods between the recurrent acceleration regions elemental abundance ratios were similar to those of the anomalous cosmic rays (ACR). The intensity of the accelerated particles declined as the latitude of ULYSSES increased, probably due to the weakening of the shocks.     

The PROCESS experiment: amino and carboxylic acids under Mars-like surface UV radiation conditions in low-earth orbit

The search for organic molecules at the surface of Mars is a top priority of the next Mars exploration space missions: Mars Science Laboratory (NASA) and ExoMars (ESA). The detection of organic matter could provide information about the presence of a prebiotic chemistry or even biological activity on this planet. Therefore, a key step in interpretation of future data collected by these missions is to understand the preservation of organic matter in the martian environment. Several laboratory experiments have been devoted to quantifying and qualifying the evolution of organic molecules under simulated environmental conditions of Mars. However, these laboratory simulations are limited, and one major constraint is the reproduction of the UV spectrum that reaches the surface of Mars. As part of the PROCESS experiment of the European EXPOSE-E mission on board the International Space Station, a study was performed on the photodegradation of organics under filtered extraterrestrial solar electromagnetic radiation that mimics Mars-like surface UV radiation conditions. Glycine, serine, phthalic acid, phthalic acid in the presence of a mineral phase, and mellitic acid were exposed to these conditions for 1.5 years, and their evolution was determined by Fourier transform infrared spectroscopy after their retrieval. The results were compared with data from laboratory experiments. A 1.5-year exposure to Mars-like surface UV radiation conditions in space resulted in complete degradation of the organic compounds. Half-lives between 50 and 150?h for martian surface conditions were calculated from both laboratory and low-Earth orbit experiments. The results highlight that none of those organics are stable under low-Earth orbit solar UV radiation conditions.     

The Theory of Gamma-Ray Bursts

This chapter gives a brief review on the theory of gamma-ray bursts (GRBs), including the models of multi-messengers (e.g., prompt multiwavelength electromagnetic emissions, high-energy neutrinos, ultra-high-energy cosmic rays, and gravitational waves) and central engines (in particular, mergers of binary neutron stars for short GRBs). For detailed reviews, please see (Piran in Phys. Rep. 314:575, 1999; Rev. Mod. Phys. 76:1143, 2004; Mészáros in Annu. Rev. Astron. Astrophys. 40:137, 2002; Rep. Prog. Phys. 69:2259, 2006; Zhang and Mészáros in Int. J. Mod. Phys. A 19:2385, 2004; Zhang in Chin. J. Astron. Astrophys. 7:1, 2007; Nakar in Phys. Rep. 442:166, 2007; Kumar and Zhang in Phys. Rep. 561:1, 2015).     

Lessons learned from the dynamic identification/qualification tests on the ESC-A upper stage model

The dynamic qualification of the new cryogenic upper stage ESC-A of the ARIANE 5 is supported by several tests in order to verify the assumptions and the modeling approach made at the beginning of the development. The stage contains a large amount of equipment such as propellant lines, acceleration rockets, batteries, fluid control equipment etc. For the low frequency domain the verification of the equipment responses in the integrated state was done by a sine vibration test, excited to levels representing the predicted flight loads including a qualification factor. Acoustic tests with the upper stage were performed to verify the random vibration responses in the frequency range up to 2000 Hz. To verify the shock response level induced by stage separation (pyro-shock) a stage separation test was performed. The paper concentrates on the experience made with the modal identification and sine vibration test of the stage. For the sine vibration test an electro-dynamic multi-shaker table was used. It was able to produce the required input precisely up to as specified, not an easy task for a test set-up of 20 tons weight. The paper presents the approach of how the dynamic qualification was reached successfully and highlights the experience accomplished.     

Solar variability for periods of days to months

The time series of total solar irradiance determinations from ACRIM on the Solar Maximum Mission satellite (SMM) of 270 days and from the ERB experiment on NIMBUS 7 of 1445 days are analysed for periods greater than a few days. Comparison of the spectra of both with the spectrum of projected sunspot area over the corresponding time periods show high coherence for periods of 7 to about 25 days and for periods longer than about 30 to 35 days. In the vicinity and at the 27-day rotational period of the Sun, however, the coherence between sunspot area and irradiance is small, although both spectra show significant power at and around this period. This means that there is a signal in the irradiance which cannot be due to the sunspot area and the assumption of a straight forward sunspot blocking seems to be over simplified. This irradiance signal at 27 days has an amplitude of about ±0.012 per cent and is an enhancement.     

Total Solar Irradiance: What Have We Learned from the Last Three Cycles and the Recent Minimum?

The record of total solar irradiance (TSI) during the past 35 years shows similarities of the three solar cycles, but also important differences. During the recent minimum with an unusually long periods with no sunspots, TSI was also extremely low, namely 25% of a typical cycle amplitude lower than in 1996. Together with the values during the previous minima this points to a long-term change related to the strength of solar activity. On the other hand, activity indices as the 10.7?cm radio flux (F10.7), the CaII and MgII indices and also the Ly-α irradiance, show a much smaller decrease. This means that proxy models for TSI based on the photometric sunspot index (PSI), and on e.g. MgII index to represent faculae and network have to be complemented by a further component for the long-term change. TSI values at minima are correlated with the simultaneous values of the open magnetic field of the Sun at 1 AU and thus, these values may be used as a surrogate for the long-term change component. Such a 4-component model explains almost 85% of the variance of TSI over the three solar cycles available. This result supports also the idea that the long-term change of TSI is not due to manifestations of surface magnetism as the solar cycle modulation, but due to a change of the global temperature of Sun modulated by the strength of activity—being lower during low activity. To explain the difference between the minima in 1996 and 2008 we need a change of only 0.25?K.