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"Solar activity."
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Solar storms
Presents a range of views about the extent and type of damage that could result from solar storms. Proposed warning systems and other protective measures are also addressed.
Book
A 22 yr Cycle of the Network Topology of Solar Active Regions
In this paper, solar cycles 21–24 were compared using complex network analysis. A network was constructed for these four solar cycles to facilitate the comparison. In these networks, the nodes represent the active regions of the Sun that emit flares, and the connections correspond to the sequence of solar flares over time. This resulted in a directed network with self-connections allowed. The model proposed by Abe and Suzuki for earthquake networks was followed. The incoming degree for each node was calculated, and the degree distribution was analyzed. It was found that for each solar cycle, the degree distribution follows a power law, indicating that solar flares tend to appear in correlated active zones rather than being evenly distributed. Additionally, a variation in the characteristic exponent γ for each cycle was observed, with higher values in even cycles compared to odd cycles. A more detailed analysis was performed by constructing 11 yr networks and shifting them in 1 yr intervals. This revealed that the characteristic exponent shows a period of approximately 22 yr coincident with the Hale cycle, suggesting that the complex networks provide information about the solar magnetic activity.
Journal Article
The sun is kind of a big deal
A \"picture book from Awkward Yeti creator Nick Seluk [that] explains every part of the Sun's big job: keeping our solar system together, giving Earth day and night, keeping us warm, and more\"-- Provided by publisher.
Book
Changes of Magnetic Energy and Helicity in Solar Active Regions from Major Flares
Magnetic free energy powers solar flares and coronal mass ejections, and the buildup of magnetic helicity might play a role in the development of unstable structures that subsequently erupt. To better understand the roles of energy and helicity in large flares and eruptions, we have characterized the evolution of magnetic energy and helicity associated with 21 X-class flares from 2010 to 2017. Our sample includes both confined and eruptive events, with 6 and 15 in each category, respectively. Using the Helioseismic and Magnetic Imager vector magnetic field observations from several hours before to several hours after each event, we employ (a) the Differential Affine Velocity Estimator for Vector Magnetograms to determine the photospheric fluxes of energy and helicity, and (b) nonlinear force-free field extrapolations to estimate the coronal content of energy and helicity in source-region fields. Using superposed epoch analysis, we find, on average, the following: (1) decreases in both magnetic energy and helicity, in both photospheric fluxes and coronal content, that persist for a few hours after eruptions, but no clear changes, notably in relative helicity, for confined events; (2) significant increases in the twist of photospheric fields in eruptive events, with twist uncertainties too large in confined events to constrain twist changes (and lower overall twist in confined events); and (3) on longer timescales (event time +12 hr), replenishment of free magnetic energy and helicity content to near preevent levels for eruptive events. For eruptive events, magnetic helicity and free energy in coronal models clearly decrease after flares, with the amounts of decrease proportional to each region’s pre-flare content.
Journal Article
Rebel star : our quest to solve the great mysteries of the sun
In 1869, a solar mystery was uncovered - astronomers observed a total solar eclipse, and for the first time saw the faint glow of the solar corona, the sun's outer atmosphere. Measurements of a previously unknown wavelength that made up this solar light sparked hot debate among scientists about its chemical components, and it wasn't until 1930 that scientists discovered that this wavelength was in fact iron being burned at 3,000,000 degrees Celsius. With the sun's surface at a mere 6,000 degrees C, the real mystery was born - what was heating the sun's corona? Our sun appeared to defy the laws of physics and nature. Since then, the sun has proved difficult to study, and its mysteries largely persist. But in summer 2018 and spring 2019, NASA and then the European Space Agency (ESA) are launching two of their most ambitious space missions to date, repeatedly diving closer to the sun than any previous spacecraft in history. These essential missions promise to provide important information about the sun's corona, and the unpredictable and destructive nature of solar wind. This timely and essential guide will examine our long-held fascination with the Red Giant, from ancient beliefs, to early scientific studies, right up to our present-day understanding, taking the lay reader on an absorbing and thrilling journey to the centre of our solar system.
Book
A Comprehensive Radiative Magnetohydrodynamics Simulation of Active Region Scale Flux Emergence from the Convection Zone to the Corona
We present a comprehensive radiative magnetohydrodynamic simulation of the quiet Sun and large solar active regions. The 197 Mm wide simulation domain spans from 18(10) Mm beneath the photosphere to 113 Mm in the solar corona. Radiative transfer assuming local thermal equilibrium, optically thin radiative losses, and anisotropic conduction transport provide the necessary realism for synthesizing observables to compare with remote-sensing observations of the photosphere and corona. This model self-consistently reproduces observed features of the quiet Sun, emerging and developed active regions, and solar flares up to M class. Here, we report an overview of the first results. The surface magneto-convection yields an upward Poynting flux that is dissipated in the corona and heats the plasma to over 1 MK. The quiescent corona also presents ubiquitous propagating waves, jets, and bright points with sizes down to 2 Mm. Magnetic flux bundles emerge into the photosphere and give rise to strong and complex active regions with over 1023 Mx magnetic flux. The coronal free magnetic energy, which is approximately 18% of the total magnetic energy, accumulates to approximately 1033 erg. The coronal magnetic field is clearly non-force-free, as the Lorentz force needs to balance the pressure force and viscous stress as well as drive magnetic field evolution. The emission measure from log10T=4.5 to log10T>7 provides a comprehensive view of the active region corona, such as coronal loops of various lengths and temperatures, mass circulation by evaporation and condensation, and eruptions from jets to large-scale mass ejections.
Journal Article
Extraterrestrial influence on climate change
An attempt is being made here to understand the influence of extraterrestrial activities as one of the important factors of climate change has been attempted here. The influence of Sun and distant stars on the environment of the earth has been studied during the cyclic changes in the Sun as well as episodic changes in the environment due to the effect of other celestial objects in between Sun-Earth environment. The study has been carried out based on the changes within the Sun as well as changes during the solar eclipse. During these extraterrestrial changes it has been observed that the earth changes in its atmosphere as well as geosphere, which may have local effect but the increase of these local effect in large scale may contribute to the climate change. Solar radiation drives atmospheric circulation. Since solar radiation represents almost all the energy available to the Earth, accounting for solar radiation and how it interacts with the atmosphere and the Earth's surface is fundamental to understanding the Earth's energy budget.
Book
On the Connection between Rieger-type and Magneto-Rossby Waves Driving the Frequency of the Large Solar Eruptions during Solar Cycles 19–25
Global solar activity variation mainly occurs over about an 11 yr cycle. However, both longer and shorter periodicities than the solar cycle are also present in many different solar activity indices. The longer timescales may be up to hundreds of years, while the shorter timescales for global solar variability could be within 0.5–2 yr, which include, e.g., from the Rieger-type periods (150–160 days) to quasi-biennial oscillations of 2 yr. The most likely origin of this short-timescale quasi-periodicity is attributed to magnetic Rossby waves, which have periods of 0.8–2.4 yr. In this work, we present findings of a unique evolution of identified shorter periodicities, like the Rieger-type, arising from magnetic Rossby waves, throughout Solar Cycles 19–25. We report further observational evidence of the strong relationship between the Rieger-type periodicity, magneto-Rossby waves, and major solar flare activity. Moreover, this study also reveals that the global solar magnetic field has a continuous periodic longitudinal conveyor belt motion along the solar equator, together with an up-and-down movement in the latitudinal directions. We found that when these longitudinal and latitudinal movements have Rieger-type periodicity and magneto-Rossby waves during the same period of a solar cycle, major flare activity is present.
Journal Article
The science behind wonders of the sun : sun dogs, lunar eclipses, and green flash
\"Scientific explanations of natural phenomena caused by the Sun\"-- Provided by publisher.
Book
Hemispheric Distribution of Solar Active Regions during Solar Cycles 23–25
Solar active regions (ARs) are crucial for understanding the long-term evolution of solar activities and predicting eruptive phenomena, including solar flares and coronal mass ejections. However, the cycle-dependent properties in the north–south asymmetry of ARs are not fully understood. In this study, we investigate the hemispheric distribution of ARs from Carrington rotations 1909–2278 (between 1996 May and 2023 November) by using three parameters that describe the magnetic field distribution of ARs: number, area, and flux. The main findings are as follows: (1) The three AR parameters show significant hemispheric asymmetry in cycles 23–25. The strong correlation between the AR area and flux indicates that they can better reflect the intrinsic properties of the solar magnetic field. (2) The correlation between sunspot activity and AR parameters varies in the two hemispheres across the different cycles. The AR parameters provide additional information for the variations in sunspot activity, which can better predict the intensity and cyclical changes of solar activity. (3) The variation in the fitting slope sign of the asymmetry index for AR parameters reflects periodic changes in hemispheric ARs, providing valuable insights into the activity of other stars. (4) Both the dominant hemisphere and the cumulative trend of AR parameters display a cycle-dependent behavior. Moreover, the trend variations in the AR area and flux are similar, reflecting the long-term evolutionary characteristics of the solar magnetic field. Our analysis results are relevant for understanding the hemispheric coupling of solar magnetic activity and its cyclic evolutionary patterns.
Journal Article