Mechanisms and Observations of Coronal Dimming for the 2010 August 7 Event

Coronal dimming of extreme ultraviolet (EUV) emission has the potential to be a useful forecaster of coronal mass ejections (CMEs). As emitting material leaves the corona, a temporary void is left behind which can be observed in spectral images and irradiance measurements. The velocity and mass of the CMEs should impact the character of those observations. However, other physical processes can confuse the observations. We describe these processes and the expected observational signature, with special emphasis placed on the differences. We then apply this understanding to a coronal dimming event with an associated CME that occurred on 2010 August 7. Data from the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) and EUV Variability Experiment (EVE) are used for observations of the dimming, while the Solar and Heliospheric Observatory's (SOHO) Large Angle and Spectrometric Coronagraph (LASCO) and the Solar Terrestrial Relations Observatory's (STEREO) COR1 and COR2 are used to obtain velocity and mass estimates for the associated CME. We develop a technique for mitigating temperature effects in coronal dimming from full-disk irradiance measurements taken by EVE. We find that for this event, nearly 100% of the dimming is due to mass loss in the corona

Reconciling specific and unspecific risk factors: the interplay between theory and data

Contains fulltext : 89487.pdf (publisher's version ) (Closed access)1 juni 201

Study of Time Evolution of Thermal and Non-Thermal Emission from an M-Class Solar Flare

We conduct a wide-band X-ray spectral analysis in the energy range of 1.5-100 keV to study the time evolution of the M7.6 class flare of 2016 July 23, with the Miniature X-ray Solar Spectrometer (MinXSS) CubeSat and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft. With the combination of MinXSS for soft X-rays and RHESSI for hard X-rays, a non-thermal component and three-temperature multi-thermal component -- "cool" ($T \approx$ 3 MK), "hot" ($T \approx$ 15 MK), and "super-hot" ($T \approx$ 30 MK) -- were measured simultaneously. In addition, we successfully obtained the spectral evolution of the multi-thermal and non-thermal components with a 10 s cadence, which corresponds to the Alfv\'en time scale in the solar corona. We find that the emission measures of the cool and hot thermal components are drastically increasing more than hundreds of times and the super-hot thermal component is gradually appearing after the peak of the non-thermal emission. We also study the microwave spectra obtained by the Nobeyama Radio Polarimeters (NoRP), and we find that there is continuous gyro-synchrotron emission from mildly relativistic non-thermal electrons. In addition, we conducted a differential emission measure (DEM) analysis by using Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) and determine that the DEM of cool plasma increases within the flaring loop. We find that the cool and hot plasma components are associated with chromospheric evaporation. The super-hot plasma component could be explained by the thermalization of the non-thermal electrons trapped in the flaring loop.Comment: 20 pages, 12 figures, 1 tables. Accepted for publication in Ap

Probing microscopic origins of confined subdiffusion by first-passage observables

Subdiffusive motion of tracer particles in complex crowded environments, such as biological cells, has been shown to be widepsread. This deviation from brownian motion is usually characterized by a sublinear time dependence of the mean square displacement (MSD). However, subdiffusive behavior can stem from different microscopic scenarios, which can not be identified solely by the MSD data. In this paper we present a theoretical framework which permits to calculate analytically first-passage observables (mean first-passage times, splitting probabilities and occupation times distributions) in disordered media in any dimensions. This analysis is applied to two representative microscopic models of subdiffusion: continuous-time random walks with heavy tailed waiting times, and diffusion on fractals. Our results show that first-passage observables provide tools to unambiguously discriminate between the two possible microscopic scenarios of subdiffusion. Moreover we suggest experiments based on first-passage observables which could help in determining the origin of subdiffusion in complex media such as living cells, and discuss the implications of anomalous transport to reaction kinetics in cells.Comment: 21 pages, 3 figures. Submitted versio