Observations of the low solar corona in the extreme ultraviolet and in soft X-rays evidence a close relationship of coronal dimmings and coronal mass ejections (CMEs). Dimmings are usually interpreted as places of plasma evacuation during a CME. We characterize a CME by the apparent angular extent of associated dimmings above the solar limb and define a global CME as a CME with the total apparent extent of limb dimmings of more than 180Њ. Several examples of global CMEs are discussed. All the global CMEs identified up to now are fast fullhalo CMEs associated with X-class flares (if they originate on the front side of the Sun). We demonstrate that global CMEs involve an eruption of several magnetic flux systems distributed on a large spatial scale comparable to one-half of the solar disk (true angular width around 180Њ). We discuss possible interpretations of the global CME phenomenon and challenges it presents to CME modeling. Our results suggest a nonlocal nature of the CME eruption mechanism.

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We present study of the complex event consisting of several solar wind transients detected by Advanced Composition Explorer (ACE) on 4 -7 August 2011, that caused a geomagnetic storm with Dst= −110 nT. The supposed coronal sources -three flares and coronal mass ejections (CMEs) occurred on 2 -4 August 2011 in the active region (AR) 11261. To investigate the solar origin and formation of these transients we studied kinematic and thermodynamic properties of the expanding coronal structures using the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) EUV images and the differential emission measure (DEM) diagnostics. The Helioseismic and Magnetic Imager (HMI) magnetic field maps were used as the input data for the 3D magnetohydrodynamic (MHD) model to describe the flux rope ejection (Pagano, Mackay, and Poedts, 2013b). We characterize the early phase of the flux rope ejection in the corona, where the usual three-component CME structure formed. The flux rope ejected with a speed of about 200 km s −1 to the height of 0.25 R ⊙ . The kinematics of the modeled CME front agrees well with the Solar Terrestrial Relations Observatory (STEREO) EUV measurements. Using the results of the plasma diagnostics and MHD modeling, we calculated the ion charge ratios of carbon and oxygen as well as the mean charge state of iron ions of the 2 August 2011 CME, taking into account the processes of heating, cooling, expansion, ionization, and recombination of the moving plasma in the corona up to the frozen-in region. We estimated a probable heating rate of the CME plasma in the low corona by matching the calculated ion composition parameters of the CME with those measured in situ for the solar wind transients. We also consider the similarities and discrepancies between the results of the MHD simulation and the observations.

[1] We investigate the average properties of geomagnetic storms using the global and local Dxt indices at four Dst stations in 1932Dst stations in -2009. Imposing the condition of complete data availability during storms, our study includes 1268/362/134/59 storms with Dxt minimum less than À50/À100/À150/À200 nT, respectively. The global Dxt minima were, on an average, À94/À156/À216/À275 nT, while deepest storm-time local Dxt minima were À137/À214/À285/À350 nT. Accordingly, the local Dxt minima are typically 25-30% stronger than the global Dxt minima. The distribution of largest storm-time disturbances is strongly peaked at 18 local time (LT), challenging local midnight as the dominant ion source. Relative timing of local minima verifies that stations at earlier LT hour observe their minimum a couple of hours after the deepest minimum, in agreement with westward drift of ions. Storm-time maximum asymmetries were found to increase with storm intensity level from about 70 nT to 150 nT for À50 to À200 nT storms. However, strong storms are relatively more symmetric than weak storms when compared to the typical level of local disturbance. During individual storms the asymmetry can be more than 200 nT. The rate of evolution of storm-time asymmetry is found to be roughly twice as fast for large storms. We emphasize that the unique database of local Dxt indices proves to be very useful in studying the average spatial distribution and temporal evolution of storms.

Mercury's surface is thought to be covered with highly space-weathered silicate material. The regolith is composed of material accumulated during the time of planetary formation, and subsequently from comets, meteorites, and the Sun. Ground-based observations indicate a heterogeneous surface composition with SiO 2 content ranging from 39 to 57 wt%. Visible and near-infrared spectra, multi-spectral imaging, and modeling indicate expanses A. Sprague ( ) Lunar and A. Sprague et al.of feldspathic, well-comminuted surface with some smooth regions that are likely to be magmatic in origin with many widely distributed crystalline impact ejecta rays and blocky deposits. Pyroxene spectral signatures have been recorded at four locations. Although highly space weathered, there is little evidence for the conversion of FeO to nanophase metallic iron particles (npFe 0 ), or "iron blebs," as at the Moon. Near-and mid-infrared spectroscopy indicate clino-and ortho-pyroxene are present at different locations. There is some evidence for no-or low-iron alkali basalts and feldspathoids. All evidence, including microwave studies, point to a low iron and low titanium surface. There may be a link between the surface and the exosphere that may be diagnostic of the true crustal composition of Mercury. A structural global dichotomy exists with a huge basin on the side not imaged by Mariner 10. This paper briefly describes the implications for this dichotomy on the magnetic field and the 3 : 2 spin : orbit coupling. All other points made above are detailed here with an account of the observations, the analysis of the observations, and theoretical modeling, where appropriate, that supports the stated conclusions.

Mercury's surface is thought to be covered with highly space-weathered silicate material. The regolith is composed of material accumulated during the time of planetary formation, and subsequently from comets, meteorites, and the Sun. Ground-based observations indicate a heterogeneous surface composition with SiO 2 content ranging from 39 to 57 wt%. Visible and near-infrared spectra, multi-spectral imaging, and modeling indicate expanses A. Sprague ( )

The dayside magnetosphere and proton radiation belt were analyzed during unusual magnetic storm on 21 January 2005. We have found that from 1712 to 2400 UT, the subsolar magnetopause was continuously located inside geosynchronous orbit due to strong compression. The compression was extremely strong from 1846 to 2035 UT when the dense plasma of fast erupting filament produced the solar wind dynamic pressure that peaked up to > 100 nPa, and during the first time, the upstream solar wind was observed at geosynchronous orbit for almost 2 h. Under the extreme compression, the outer magnetosphere at L > 5 was pushed inward, and the outer radiation belt particles moved earthward, became adiabatically accelerated, and accumulated in the inner magnetosphere at L < 4 that produced the intensified ring current with an exceptionally long lifetime. The observations were compared with predictions of various empirical and first-principles models. All the models failed to predict the magnetospheric dynamics under the extreme compression when the minimal magnetopause distance was estimated to be~3 RE. The inconsistencies might result from distortions of plasma measurements by extreme heliospheric conditions consisting in very fast solar wind streams and intense fluxes of solar energetic particles. We speculated that anomalous dynamics of the magnetosphere could be well described by the models if the He abundance in the solar wind was assumed to be > 20%, which is well appropriate for erupting filaments and which is in agreement with the upper 27% threshold for the He/H ratio obtained from Cluster measurements.

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