[1] A new three-dimensional asymmetric magnetopause model has been developed for corrected GSM coordinates and parameterized by the solar wind dynamic and magnetic pressures (P d + P m ), the interplanetary magnetic field (IMF) B z , and the dipole tilt angle. On the basis of the magnetopause crossings from Geotail, IMP 8, Interball, TC1, Time History of Events and Macroscale Interactions during Substorms (THEMIS), Wind, Cluster, Polar, Los Alamos National Laboratory (LANL), GOES, and Hawkeye, and the corresponding upstream solar wind parameters from ACE, Wind, or OMNI, this model is constructed by the Levenberg-Marquardt method for nonlinear multiparameter fitting step-by-step over the divided regions. The asymmetries of the magnetopause and the indentations near the cusps are appropriately described in this new model. In addition, the saturation effect of IMF B z on the subsolar distance and the extrapolation for the distant tail magnetopause are also considered. On the basis of this model, the power law index for the subsolar distance versus P d + P m is a bit less than −1/6, the northward IMF B z almost does not influence the magnetopause, and the dipole tilt angle is very important to the north-south asymmetry and the location of indentations. In comparison with the previous empirical magnetopause models based on our database, the new model improves prediction capability to describe the three-dimensional structure of the magnetopause. It is shown that this new model can be used to quantitatively study how P d + P m compresses the magnetopause, how the southward IMF B z erodes the magnetopause, and how the dipole tilt angle influences the north-south asymmetry and the indentations.

The influences of arbuscular mycorrhizal (AM) fungus on growth, gas exchange, chlorophyll concentration, chlorophyll fluorescence and water status of maize (Zea mays L.) plants were studied in pot culture under well-watered and drought stress conditions. The maize plants were grown in a sand and black soil mixture for 4 weeks, and then exposed to drought stress for 4 weeks. Drought stress significantly decreased AM colonization and total dry weight. AM symbioses notably enhanced net photosynthetic rate and transpiration rate, but decreased intercellular CO 2 concentration of maize plants regardless of water treatments. Mycorrhizal plants had higher stomatal conductance than non-mycorrhizal plants under drought stress. The concentrations of chlorophyll were higher in mycorrhizal than non-mycorrhizal plants under drought stress. AM colonization significantly increased maximal fluorescence, maximum quantum efficiency of PSII photochemistry and potential photochemical efficiency, but decreased primary fluorescence under well-watered and droughted conditions. Mycorrhizal maize plants had higher relative water content and water use efficiency under drought stress compared with non-mycorrhizal plants. The results indicated that AM symbiosis alleviates the toxic effect of drought stress via improving photosynthesis and water status of maize plants.

We report a subarcsecond penumbral transient brightening event with the high-spatial resolution observations from the 1.6 m New Solar Telescope (NST), Interface Region Imaging Spectrograph (IRIS), and the Solar Dynamics Observatory. The transient brightening, whose thermal energy is in the range of nanoflares, has signatures in the chromosphere, the transient region, and the corona. NST's Hα channel reveals the fine structure of the event with a width as narrow as 101 km (0.″14), which is much smaller than the width from the previous observation. The transient brightening lasts for about 3 minutes. It is associated with a redshift of about 17 km s−1, found in the Si iv 1402.77 Å line and exhibits an inward motion to the umbra with a speed of 87 km s−1. The small-scale energy released from the event has a multi-temperature component. Spectral analysis of the brightening region from IRIS shows that not only the transition region lines such as Si iv 1402.77 Å and C ii 1334.53 Å, but also the chromospheric Mg ii k 2796.35 Å line are significantly enhanced and broadened. In addition, the event can be found in all the extreme-ultraviolet passbands of the Atmospheric Imaging Assembly and the derived differential emission measure profile increases between 4 and 15 MK (or 6.6 ≤ log T ≤ 7.2) in the transient brightening phase. It is possible that the penumbral transient brightening event is caused by magnetic reconnection.

An extended data set of magnetopause crossings observed at geosynchronous orbit was collected for nine major magnetic storms that occurred from 2000 to 2005. The new set of geosynchronous magnetopause crossings (GMCs) was used for comparative analysis of several magnetopause models during severe, strong, and extremely strong magnetic storms. The analysis allowed verification of specific effects such as saturation of an influence of interplanetary magnetic field Bz and dawn‐dusk asymmetry. It was shown that the effects of saturation and duskward magnetopause skewing were important on the main phase of magnetic storms. Among the models considered, the most accurate prediction of GMCs was found for three models: Kuznetsov and Suvorova (1998a), Lin et al. (2010), and Dmitriev et al. (2011). The model by Lin et al. (2010) demonstrated the best capability of GMC prediction in a wide range of geomagnetic disturbances from severe to extremely strong magnetic storms.