Large-scale Coronal Heating, Clustering of Coronal Bright Points, and Concentration of Magnetic Flux

By combining quiet-region Fe XII coronal images from SOHO/EIT with magnetograms from NSO/Kitt Peak and from SOHO/MDI, we show that the population of network coronal bright points and the magnetic flux content of the network are both markedly greater under the bright half of the large-scale quiet corona than under the dim half. These results (1) support the view that the heating of the entire corona in quiet regions and coronal holes is driven by fine-scale magnetic activity (microflares, explosive events, spicules) seated low in the magnetic network, and (2) suggest that this large-scale modulation of the magnetic flux and coronal heating is a signature of giant convection cells. This revised version was published online in June 2006 with corrections to the Cover Date.     

Lava cave microbial communities within mats and secondary mineral deposits: implications for life detection on other planets

Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai'i) that is blue-green in color and contains reticulated and fuzzy filament morphologies. In the Azores, lava tubes contain iron-oxide formations, a soft ooze-like coating, and pink hexagons on basaltic glass, while gold-colored deposits are found in lava caves in New Mexico and Hawai'i. A combination of scanning electron microscopy (SEM) and molecular techniques was used to analyze these communities. Molecular analyses of the microbial mats and secondary mineral deposits revealed a community that contains 14 phyla of bacteria across three locations: the Azores, New Mexico, and Hawai'i. Similarities exist between bacterial phyla found in microbial mats and secondary minerals, but marked differences also occur, such as the lack of Actinobacteria in two-thirds of the secondary mineral deposits. The discovery that such deposits contain abundant life can help guide our detection of life on extraterrestrial bodies.     

Solar Cycle Forecasting

Predicting the behavior of a solar cycle after it is well underway (2–3 years after minimum) can be done with a fair degree of skill using auto-regression and curve fitting techniques that don’t require any knowledge of the physics involved. Predicting the amplitude of a solar cycle near, or before, the time of solar cycle minimum can be done using precursors such as geomagnetic activity and polar fields that do have some connection to the physics but the connections are uncertain and the precursors provide less reliable forecasts. Predictions for the amplitude of cycle 24 using these precursor techniques give drastically different values. Recently, dynamo models have been used directly with assimilated data to predict the amplitude of sunspot cycle 24 but have also given significantly different predictions. While others have questioned both the predictability of the solar cycle and the ability of current dynamo models to provide predictions, it is clear that cycle 24 will help to discriminate between some opposing dynamo models.