One of the most important unsolved problems in solar physics is to understand the mechanism of the solar cycle. Sunspots provided the first evidence for the 11-year cycle of solar activity and continue to provide key indicators of the level and nature of solar activity. Solar flares, prominence eruptions, and coronal mass ejections increase in frequency as the number of sunspots increases during the rising phase of the solar cycle. The total irradiance of the Sun and its irradiance in ultraviolet light and X-rays also increase as the sunspot number increases. On the other hand, the flux of galactic cosmic rays reaching Earth decreases as the sunspot number increases. While flares and coronal mass ejections pose a serious hazard to astronauts, satellites, polar air-traffic, electric power grids, and telecommunications facilities on short timescales ranging from hours to days, the solar radiative output affects planetary and global climate on much longer time scales (from decades to stellar evolutionary time scales).

We invite authors to contribute original research articles as well as review articles that will stimulate the continuing efforts to understand the solar cycle and its impact on space weather and global climate. Potential topics include, but are not limited to:

• Solar magnetic dynamo mechanisms
• Evolutions of the Sun's large-scale magnetic field and large-scale flows
• Solar shape variations and astrophysical consequences
• Solar irradiance variations and solar activity impact on space weather and global climate

Before submission authors should carefully read over the journal's Author Guidelines, which are located at http://www.hindawi.com/journals/aa/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/ according to the following timetable: