In this study we use the ordinal logistic regression method to establish a prediction model, which estimates the probability for each solar active region to produce X-, M-, or Cclass flares during the next 1-day time period. The three predictive parameters are (1) the total unsigned magnetic flux T flux , which is a measure of an active region's size, (2) the length of the strong-gradient neutral line L gnl , which describes the global nonpotentiality of an active region, and (3) the total magnetic dissipation E diss , which is another proxy of an active region's nonpotentiality. These parameters are all derived from SOHO MDI magnetograms. The ordinal response variable is the different level of solar flare magnitude. By analyzing 174 active regions, L gnl is proven to be the most powerful predictor, if only one predictor is chosen. Compared with the current prediction methods used by the Solar Monitor at the Solar Data Analysis Center (SDAC) and NOAA's Space Weather Prediction Center (SWPC), the ordinal logistic model using L gnl , T flux , and E diss as predictors demonstrated its automatic functionality, simplicity, and fairly high prediction accuracy. To our knowledge, this is the first time the ordinal logistic regression model has been used in solar physics to predict solar flares.

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Using line-of-sight Michelson Doppler Imager (MDI ) magnetograms of 89 active regions and Solar Geophysical Data (SGD) flare reports, we explored, for the first time, the magnitude scaling correlations between three parameters of magnetic fields and the flare productivity of solar active regions. These parameters are (1) the mean value of spatial magnetic gradients at strong-gradient magnetic neutral lines, (9B z ) NL ; (2) the length of strong-gradient magnetic neutral lines, L GNL ; and (3) the total magnetic energy, R (B z ) dA, dissipated in a layer of 1 m during 1 s over the active region's area. The MDI magnetograms of active regions used for our analysis are close to the solar central meridian (within AE10 ). The flare productivity of active regions was quantified by the soft X-ray flare index for different time windows from the time interval of the entire disk passage down to +1 day from the time of the analyzed magnetogram. Our results explicitly indicate positive correlations between the parameters and the overall flare productivity of active regions, and imminent flare production as well. The correlations confirm the dependence of flare productivity on the degree of nonpotentiality of active regions.

To study the three-dimensional (3D) magnetic field topology and its long-term evolution associated with the X3.4 flare of 2006 December 13, we investigate the coronal relative magnetic helicity in the flaring active region (AR) NOAA 10930 during the time period of December 8-14. The coronal helicity is calculated based on the 3D nonlinear force-free magnetic fields reconstructed by the weighted optimization method of Wiegelmann, and is compared with the amount of helicity injected through the photospheric surface of the AR. The helicity injection is determined from the magnetic helicity flux density proposed by Pariat et al. using Solar and Heliospheric Observatory/Michelson Doppler Imager magnetograms. The major findings of this study are the following. (1) The time profile of the coronal helicity shows a good correlation with that of the helicity accumulation by injection through the surface. (2) The coronal helicity of the AR is estimated to be −4.3×10 43 Mx 2 just before the X3.4 flare. (3) This flare is preceded not only by a large increase of negative helicity, −3.2×10 43 Mx 2 , in the corona over ∼1.5 days but also by noticeable injections of positive helicity though the photospheric surface around the flaring magnetic polarity inversion line during the time period of the channel structure development. We conjecture that the occurrence of the X3.4 flare is involved with the positive helicity injection into an existing system of negative helicity.

The concept of ''magnetic channel'' was first introduced by Zirin & Wang. They were defined as a series of oppositely directed vertical-field inversions separated by extremely narrow elongated transverse fields. In this paper, we utilized unprecedented filtergraph and spectropolarimetry observations from Hinode, and studied the evolution and physical properties of channel structure of AR 10930 in detail. We found the following: (1) Channels are associated with new flux emergence in the middle of existing penumbra connecting the sunspot. (2) The width of each channel is in the order of 1 00 or less. (3) The line-of-sight magnetic gradient is highest in the channel, 2.4Y4.9 G km À1. (4) The fields are highly sheared and inclined with a median shear angle around 64 and inclination angle around 25. (5) Using nonlinear force-free field (NLFF) extrapolation, we derive a near surface current system carrying electric current in the order of 5 ; 10 11 A. (6) The X3.4 flare on 2006 December 13 occurred during the period that the channels rapidly formed, but a few hours before the maximum phase of channel structure development. Based on the observational evidence, we propose that the channels are formed during the emergence of a sequence of magnetic bipoles that are squeezed in the compact penumbra of the sunspot and they are highly nonpotential. Formation of channels might be a precursor of major flares.

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Four flow-through experiments at 150°C were conducted on intact cores of basalt to assess alteration and mass transfer during reaction with CO 2-rich fluid. Two experiments used a flow rate of 0.1 ml/min, and two used a flow rate of 0.01 ml/min. Permeability increased for both experiments at the higher flow rate, but decreased for the lower flow rate experiments. The

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