Search Publications
The Solar Cycle
Hathaway, David H.
The solar cycle is reviewed. The 11-year cycle of solar activity is characterized by the rise and fall in the numbers and surface area of sunspots. A number of other solar activity indicators also vary in association with the sunspots including; the 10.7 cm radio flux, the total solar irradiance, the magnetic field, flares and coronal mass ejectio…
The FIP and Inverse FIP Effects in Solar and Stellar Coronae
Laming, J. Martin
We review our state of knowledge of coronal element abundance anomalies in the Sun and stars. We concentrate on the first ionization potential (FIP) effect observed in the solar corona and slow-speed wind, and in the coronae of solar-like dwarf stars, and the "inverse FIP" effect seen in the corona of stars of later spectral type; specifically M d…
Evolution of Active Regions
van Driel-Gesztelyi, Lidia; Green, Lucie May
The evolution of active regions (AR) from their emergence through their long decay process is of fundamental importance in solar physics. Since large-scale flux is generated by the deep-seated dynamo, the observed characteristics of flux emergence and that of the subsequent decay provide vital clues as well as boundary conditions for dynamo models…
Ensemble Modeling of CMEs Using the WSA-ENLIL+Cone Model
Jian, L. K.; Odstrcil, D.; Zheng, Y. +8 more
Ensemble modeling of coronal mass ejections (CMEs) provides a probabilistic forecast of CME arrival time that includes an estimation of arrival-time uncertainty from the spread and distribution of predictions and forecast confidence in the likelihood of CME arrival. The real-time ensemble modeling of CME propagation uses the Wang-Sheeley-Arge (WSA…
Particle acceleration by a solar flare termination shock
Krucker, Säm; Chen, Bin; Gary, Dale E. +3 more
Solar flares—the most powerful explosions in the solar system—are also efficient particle accelerators, capable of energizing a large number of charged particles to relativistic speeds. A termination shock is often invoked in the standard model of solar flares as a possible driver for particle acceleration, yet its existence and role have remained…
Relationship between Solar Energetic Particles and Properties of Flares and CMEs: Statistical Analysis of Solar Cycle 23 Events
Dalla, S.; Malandraki, O.; Tziotziou, K. +5 more
A statistical analysis of the relationship between solar energetic particles (SEPs) and properties of solar flares and coronal mass ejections (CMEs) is presented. SEP events during Solar Cycle 23 are selected that are associated with solar flares originating in the visible hemisphere of the Sun and that are at least of magnitude M1. Taking into ac…
Large-scale Globally Propagating Coronal Waves
Warmuth, Alexander
Large-scale, globally propagating wave-like disturbances have been observed in the solar chromosphere and by inference in the corona since the 1960s. However, detailed analysis of these phenomena has only been conducted since the late 1990s. This was prompted by the availability of high-cadence coronal imaging data from numerous spaced-based instr…
The Confined X-class Flares of Solar Active Region 2192
Temmer, M.; Veronig, A. M.; Su, Y. +1 more
The unusually large active region (AR) NOAA 2192, observed in 2014 October, was outstanding in its productivity of major two-ribbon flares without coronal mass ejections. On a large scale, a predominantly north-south oriented magnetic system of arcade fields served as a strong top and lateral confinement for a series of large two-ribbon flares ori…
Flare-CME Models: An Observational Perspective (Invited Review)
Aulanier, G.; Vršnak, B.; Schmieder, B.
Eruptions, flares, and coronal mass ejection (CMEs) are due to physical phenomena mainly driven by an initially force-free current-carrying magnetic field. We review some key observations relevant to the current theoretical trigger mechanisms of the eruption and to the energy release via reconnection. Sigmoids observed in X-rays and UV, as well as…
From Coronal Observations to MHD Simulations, the Building Blocks for 3D Models of Solar Flares (Invited Review)
Aulanier, G.; Démoulin, P.; Janvier, M.
Solar flares are energetic events taking place in the Sun's atmosphere, and their effects can greatly impact the environment of the surrounding planets. In particular, eruptive flares, as opposed to confined flares, launch coronal mass ejections into the interplanetary medium, and as such, are one of the main drivers of space weather. After briefl…