Coronal shocks associated with CMEs and flares and their space weather consequences

We study the geoeffectiveness of a sample of complex events; each includes a coronal type II burst, accompanied by a GOES SXR flare and LASCO CME. The radio bursts were recorded by the ARTEMIS-IV radio spectrograph, in the 100-650 MHz range; the GOES SXR flares and SOHO/LASCO CMEs, were obtained from the Solar Geophysical Data (SGD) and the LASCO catalogue respectively. These are compared with changes of solar wind parameters and geomagnetic indices in order to establish a relationship between solar energetic events and their effects on geomagnetic activity.Comment: Universal Heliophysical Processes, Proceedings of the International Astronomical Union, IAU Symposium, Volume 257, p. 61-6

Relation between coronal type II bursts, associated flares and CMEs

We study a sample of complex events; each includes a coronal type II burst, accompanied by a GOES SXR flare and LASCO CME. The radio bursts were recorded by the ARTEMIS-IV radio spectrograph (100-650 MHz range); the GOES SXR flares and SOHO/LASCO CMEs, were obtained from the Solar Geophysical Data (SGD) and the LASCO lists respectively. The radio burst-flare-CME characteristics were compared and two groups of events with similar behavior were isolated. In the first the type II shock exciter appears to be a flare blast wave propagating in the wake of a CME. In the second the type II burst appears CME initiated though it is not always clear if it is driven by the bow or the flanks of the CME or if it is a reconnection shock.Comment: Universal Heliophysical Processes, Proceedings of the International Astronomical Union, IAU Symposium, Volume 257, p. 299-30

Candidate regions on titan as promising landing sites for future in situ missions

The highly successful and still on-going Cassini-Huygens mission to the Saturnian system points to the need for a return mission, with both remote and in situ instrumentation. The surface of Saturn’s moon Titan, hosts a complex environment in which many processes occur shaping its landscape. Several of its geological features resemble terrestrial ones, albeit constructed from different material and reflecting the interiorsurface-atmosphere exchanges. The resulting observed morphotectonic features and cryovolcanic candidate regions could benefit from further extensive exploration by a return mission that would focus on these aspects with adapted state-of-the-art instrumentation affording higher spectral and spatial resolution and in situ capabilities. We suggest that some features on Titan are more promising candidate locations for future landing and we present the case for Tui Regio, Hotei Regio and Sotra Patera as to why they could provide a wealth of new scientific results

Potentially active regions on Titan: New processing of Cassini/VIMS data

The Cassini Visual and Infrared Mapping Spectrometer (VIMS) obtained data of Titan's surface from flybys performed during the last seven years. In the 0.8-5.2 µm range, these spectro-imaging data showed that the surface consists of a multivariable geological terrain hosting complex geological processes. The data from the seven narrow methane spectral "windows" centered at 0.93, 1.08, 1.27, 1.59, 2.03, 2.8 and 5 µm provide some information on the lower atmospheric context and the surface parameters that we want to determine. Atmospheric scattering and absorption need to be clearly evaluated before we can extract the surface properties. We apply here a statistical method [1, 2] and a radiative transfer method [3, 1] on three potentially "active" regions on Titan, i.e. regions possibly subject to change over time (in brightness and/or in color etc) [4]: Tui Regio (20°S, 130°W) [5], a 1,500-km long flow-like figure, Hotei Regio (26°S, 78°W) [6], a 700-km wide volcanic-like terrain, and Sotra Facula (15°S, 42°W) [7], a 235-km in diameter area. With our method of Principal Component Analysis (PCA) we have managed to isolate specific regions of distinct and diverse chemical composition. We have tested this method on the previously studied Sinlap crater [8], delimitating compositional heterogeneous areas compatible with the published conclusions by Le Mouélic et al. (2008). Our follow-up method focuses on retrieving the surface albedo of the three areas and of the surrounding terrains with different spectral response by applying a radiative transfer (RT) code. We have used as input most of the Cassini HASI and DISR measurements, as well as new methane absorption coefficients [9], which are important to evaluate the atmospheric contribution and to allow us to better constrain the real surface alterations, by comparing the spectra of these regions. By superposing these results onto the PCA maps, we can correlate composition and morphology. As a test case, we used our RT code to verify the varying brightness of Hotei Regio reported by other investigators based on models lacking proper simulation of the atmospheric absorption [10]. Even though we have used exactly the same dataset, we did not detect any significant surface albedo variations over time; this led us to revise the definition of "active" regions: even if these regions have not visually changed over the course of the Cassini mission, the determination of the chemical composition and the correlation with the morphological structures [11] observed in these areas do not rule out that past and/or ongoing cryovolcanic processes are still a possible interpretation. [1] Solomonidou, A. et al. (2011). Potentially active regions on Titan: New processing of Cassini/VIMS data. In preparation. [2] Stephan, K. et al. (2008). Reduction of instrument-dependent noise in hyperspectral image data using the principal component analysis: Applications to Galileo NIMS data. Planetary and Space Science 56, 406-419. [3] Hirtzig, M. et al. (2011). Applications of a new methane linelist to Cassini/VIMS spectra of Titan in the 1.28-5.2 µm range . In preparation. [4] Wall, s. D. et al. (2009). Cassini RADAR images at Hotei Arcus and western Xanadu, Titan: Evidence for geologically recent cryovolcanic activity. Journal of Geophysical Research 36, L04203, [5] Barnes, J.W. et al. (2006). Cassini observations of flow-like features in western Tui Regio, Titan. Geophysical Research Letters 33, L16204. [6] Soderblom, L.A. et al. (2009). The geology of Hotei Regio, Titan: Correlation of Cassini VIMS and RADAR. Icarus 204, 610-618. [7] Lopes, R.M.C. et al. (2010). Distribution and interplay of geologic processes on Titan from Cassini radar data. Icarus 205, 540-558. [8] Le Mouélic et al. (2008). Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data. Journal of Geophysical Research 113, E04003. [9] Campargue, A. et al. (2011). An empirical line list for methane at 80 K and 296 K in the 1.26-1.71 µm region for planetary investigations. Application to Titan. Icarus. Submitted. [10] Nelson, R. et al (2009). Saturn's Titan: Surface change, ammonia, and implications for atmospheric and tectonic activity. Icarus 199, 429-441. [11] Solomonidou, A. et al. (2011). Possible morphotectonic features on Titan and their origin. Planetary and Space Science. Submitted

The Antikythera Mechanism: The oldest mechanical universe in its scientific milieu

In this review the oldest known advanced astronomical instrument and dedicated analogue computer is presented, in context. The Antikythera Mechanism a mysterious device, assumed to be ahead of its time, probably made around 150 to 100 BCE, has been found in a 1st century BCE shipwreck near the island of Antikythera, in a huge ship full of Greek treasures that were on their way to Rome. The Antikythera. Mechanism is a clock-like device made of bronze gears, which looks much more advanced than its contemporary technological achievements. It is based on mathematics attributed to the Hipparchus and possibly carries knowledge and tradition that goes back to Archimedes, who according to ancient texts constructed several automata, including astronomical devices, a mechanical planetarium and a celestial sphere. The Antikythera Mechanism probably had a beautiful and expensive box; looking possibly like a very elaborate miniature Greek Temple, perhaps decorated with golden ornaments, of an elegant Hellenistic style, even perhaps with automatic statuettes, ‘daemons’, functioning as pointers that performed some of its operations. Made out of appropriately tailored trains of gears that enable to perform specialised calculations, the mechanism carries concentric scales and pointers, in one side showing the position of the Sun in the ecliptic and the sky, possibly giving the time, hour of the clay or night, like a clock. The position of the Moon and its phase is also shown during the month. On the other side of the Mechanism, having probably the size of a box (main part 32 x 20 x 6 cm), are two large spiral scales with two pointers showing the time in two different very long calendars, the first one concerning the eclipses, and lasting 18 years 11 days and 8 hours, the Saros period, repeating the solar and lunar eclipses, and enabling their prediction, and the 19 year cycle of Meton, that is the period the Moon reappears in the same place of the sky, with the same phase. An additional four-year dial shows the year of all Greek Festivities, the so-called ‘games’ (Olympic, Pythian, Isthmian etc). Two additional dials give the Exeligmos, the 54 year and 34 day cycle, which provides a more accurate prediction of eclipses. It is possible that the Mechanism was also equipped with a planetary show display, as three of the planets and their motion (stationary points) are mentioned many times in the manual of the instrument, so it was also a planetarium. From the manual we have hints that the mechanism was probably also an observational instrument, as having instructions concerning a. viewfinder and possibly how to orient the viewfinder to pass a sunbeam through it, probably measuring the altitude of the Sun. There are fragmented sentences that probably give instructions on how to move the pointers to set the position of the Sun, the Moon and the planets in their initial places in the ecliptic, on a specific clay, or how to measure angular distances between two celestial bodies or their coordinates. This mechanism is definitely not the first one of its kind. The fact that it is accompanied with instructions means that the constructor had in its mind to be used by somebody else and one posits that he made at least another similar instrument

The maximum magnetic flux in an active region

The Photometric-Magnetic Dynamical model handles the evolution of air individual sunspot as an autonomous nonlinear, though integrable, dynamical system. The model considers the simultaneous interplay of two different interacted factors: The photometric and magnetic factors, respectively, characterizing the evolution of the sunspot visible area A oil tire photosphere, and the simultaneous evolution of the sunspot magnetic field strength B. All the possible sunspots are gathered in a, specific region of the phase space (A, B). The separatrix of this phase space region determines the upper limit of tire values of sunspot area and magnetic strength. Consequently, an upper limit of the magnetic flux in an active region is also determined, found to be approximate to 7.23 x 10(23) Mx. This value is phenomenologically equal to the magnetic flux concentrated in the totality of the granules of the quite Sun. Hence, the magnetic flux concentrated in an active region cannot, exceed the one concentrated in the whole photosphere

Enhanced Rieger type periodicities' detection in X-ray solar flares and statistical validation of Rossby waves' existence

The known Rieger Periodicity (ranging in literature from 150 up to 160 days) is obvious in numerous solar indices. Many sub-harmonic periodicities have also been observed (128-, 102-, 78-, and 51- days) in flare, sunspot, radio bursts, neutrino flux and flow data, coined as Rieger Type Periodicities (RTPs). Several attempts are focused to the discovery of their source, as well as the explanation of some intrinsic attributes that they present, such as their connection to extremely active flares, their temporal intermittency as well as their tendency to occur near solar maxima. In this paper, we link the X-ray flare observations made on Geosynchronous Operational Environmental Satellites (GOES) to an existing theoretical model (Lou 2000), suggesting that the mechanism behind the Rieger Type Periodicities is the Rossby Type Waves. The enhanced data analysis methods used in this article (Scargle-Lomb periodogram and Weighted Wavelet Z-Transform) provide the proper resolution needed to argue that. RTPs are present also in less energetic flares, contrary to what has been inferred from observations so far