Search results for "Nanoflares"
showing 5 items of 15 documents
Nonequilibrium of Ionization and the Detection of Hot Plasma in Nanoflare‐heated Coronal Loops
2008
Impulsive nanoflares are expected to transiently heat the plasma confined in coronal loops to temperatures of the order of 10 MK. Such hot plasma is hardly detected in quiet and active regions, outside flares. During rapid and short heat pulses in rarified loops the plasma can be highly out of equilibrium of ionization. Here we investigate the effects of the non-equilibrium of ionization (NEI) on the detection of hot plasma in coronal loops. Time-dependent loop hydrodynamic simulations are specifically devoted to this task, including saturated thermal conduction, and coupled to the detailed solution of the equations of ionization rate for several abundant elements. In our simulations, initi…
Coronal Magnetic Field Measurements Through Quasi-Transverse Propagation
2004
The QT-propagation of microwaves as a means to measure coronal magnetic fields and the inversion of circular polarization as an observational proof of the QT-propagation are discussed. The first part of the chapter briefly outlines the relevant geometry and mathematical relations. Then the state of the art in the coronal magnetography and some possibilities are demonstrated. We discuss use of the technique for coronal magnetography and give some estimates concerning the coronal magnetography with the forthcoming Frequency Agile Solar Radiotelescope.
Widespread Nanoflare Variability Detected with Hinode/X-Ray Telescope in a Solar Active Region
2011
It is generally agreed that small impulsive energy bursts called nanoflares are responsible for at least some of the Sun's hot corona, but whether they are the explanation for most of the multimillion-degree plasma has been a matter of ongoing debate. We present here evidence that nanoflares are widespread in an active region observed by the X-Ray Telescope on board the Hinode mission. The distributions of intensity fluctuations have small but important asymmetries, whether taken from individual pixels, multipixel subregions, or the entire active region. Negative fluctuations (corresponding to reduced intensity) are greater in number but weaker in amplitude, so that the median fluctuation i…
Magnetohydrodynamic simulations of the ejection of a magnetic flux rope
2013
Context. Coronal mass ejections (CME's) are one of the most violent phenomena found on the Sun. One model to explain their occurrence is the flux rope ejection model. In this model, magnetic flux ropes form slowly over time periods of days to weeks. They then lose equilibrium and are ejected from the solar corona over a few hours. The contrasting time scales of formation and ejection pose a serious problem for numerical simulations. Aims: We simulate the whole life span of a flux rope from slow formation to rapid ejection and investigate whether magnetic flux ropes formed from a continuous magnetic field distribution, during a quasi-static evolution, can erupt to produce a CME. Methods: To …
Numerical Simulations of a Flux Rope Ejection
2015
Coronal mass ejections (CMEs) are the most violent phenomena observed on the Sun. One of the most successful models to explain CMEs is the flux rope ejection model, where a magnetic flux rope is expelled from the solar corona after a long phase along which the flux rope stays in equilibrium while magnetic energy is being accumulated. However, still many questions are outstanding on the detailed mechanism of the ejection and observations continuously provide new data to interpret and put in the context. Currently, extreme ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) are providing new insights into the early phase of CME evo…