The Fast Imaging Solar Spectrograph (FISS) is being operated on the New Solar Telescope of the Big Bear Solar Observatory. It simultaneously records spectra of Hα and Ca
ii
8542 Å lines, and this ...dual-spectra measurement provides an estimate of the temperature and nonthermal speed components. We observed a loop structure in AR 11305 using the FISS, SDO/AIA, and STEREO/EUVI in 304 Å, and found plasma material falling along the loop from a coronal height into the umbra of a sunspot, which accelerated up to 80 km s
−1
. We also observed C2 and C7 flare events near the loop. The temperature of the downflows was in the range of 10 000 – 33 000 K, increasing toward the umbra. The temperature of the flow varied with time, and the temperature near the footpoint rose immediately after the C7 flare, but the temperature toward the umbra remained the same. There seemed to be a temporal correlation between the amount of downflow material and the observed C-class flares. The downflows decreased gradually soon after the flares and then increased after a few hours. These high-speed red-shift events occurred continuously during the observations. The flows observed on-disk in Hα and Ca
ii
8542 Å appeared as fragmented, fuzzy condensed material falling from the coronal heights when seen off-limb with STEREO/EUVI at 304 Å. Based on these observations, we propose that these flows were an on-disk signature of coronal rain.
In this paper, we present the radio and hard X-ray evidence of chromospheric evaporation during an M1.0 flare which occurred on 2004 December 1. The radio emission was observed by the Solar Broadband ...Radio Dynamic Spectrometer in China, which yielded dynamic spectra of decimetric emission. The hard X-ray emission was observed by RHESSI. In the radio spectra, the burst is characterized by two groups of parallel-drifting structures, some of which change their drifting rates from positive to negative. Based on the standard flare model, we may explain these decimetric bursts in terms of chromospheric evaporation. On the other hand, RHESSI observations show that the hard X-ray emission in the energy range of 10-15 keV tends to rise from two footpoints to the looptop and eventually merges into a single looptop source, which is accepted as evidence of hard X-ray chromospheric evaporation. Such processes happened twice in this event. The drifting radio structures occurred between them, at the same time as the third hard X-ray peak was observed at 25-50 keV.
Using multi-wavelength observations, we analysed magnetic field variations associated with a gradual X1.2 flare that erupted on January 7, 2014 in active region (AR) NOAA 11944 located near the disk ...center. A fast coronal mass ejection (CME) was observed following the flare, which was noticeably deflected in the south-west direction. A chromospheric filament was observed at the eruption site prior to and after the flare. We used SDO/HMI data to perform non-linear force-free field extrapolation of coronal magnetic fields above the AR and to study the evolution of AR magnetic fields prior to the eruption. The extrapolated data allowed us to detect signatures of several magnetic flux ropes present at the eruption site several hours before the event. The eruption site was located under slanted sunspot fields with a varying decay index of 1.0-1.5. That might have caused the erupting fields to slide along this slanted magnetic boundary rather than vertically erupt, thus explaining the slow rise of the flare as well as the observed direction of the resulting CME. We employed sign-singularity tools to quantify the evolutionary changes in the model twist and observed current helicity data, and found rapid and coordinated variations of current systems in both data sets prior to the event as well as their rapid exhaustion after the event onset.
We observed two X-class white-light flares (WLFs) on 2003 October 29 (620:40 UT) and November 2 (617:16 UT) using the Dunn Solar Telescope (DST) and its High-Order Adaptive Optics (HOAO) system in ...several wavelengths. The spatial resolution was close to the diffraction limit of DST's 76 cm aperture, and the cadence was as high as 2 s. This is the first time that WLFs have been observed in the near-infrared (NIR) wavelength region. We present a detailed study in this paper comparing photospheric continuum observations during the two events with corresponding line-of-sight magnetograms from the Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) and hard X-ray (HXR) data from the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). We also discuss several models that provide possible mechanisms to explain these continuum enhancements, especially in the NIR.
This Letter is to investigate the physics of a newly discovered phenomenon-contracting flare loops in the early phase of solar flares. In classical flare models, which were constructed based on the ...phenomenon of the expansion of flare loops, an energy releasing site is put above flare loops. These models can predict that there is a vertical temperature gradient in the top of flare loops due to heat conduction and cooling effects. Therefore, the centroid of an X-ray loop-top source at higher energy bands will be higher in altitude, which we can define as the normal temperature distribution. With observations made by RHESSI, we analyzed 10 M- or X-class flares (9 limb flares). For all these flares, the movement of loop-top sources shows an obvious U-shaped trajectory, which we take as the signature of contraction- to-expansion of flare loops. We find that, for all these flares, a normal temperature distribution does exist, but only along the path of expansion. The temperature distribution along the path of contraction is abnormal, showing no spatial order at all. The result suggests that magnetic reconnection processes in the contraction and expansion phases of these solar flares are different.
Abstract
Multiple solar instrument observation campaigns are increasingly popular among the solar physics and space science communities. Scientists organize high-resolution ground-based telescopes ...and spacecraft to study the evolution of the complex solar atmosphere and the origin of space weather. Image registration and coalignment between different instruments are vital for accurate data product comparison. We developed a Python language package for registration of ground-based high-resolution imaging data acquired by the Goode Solar Telescope (GST) to space-based full-disk continuum intensity data provided by the Solar Dynamics Observatory (SDO) with the scale-invariant feature transform method. The package also includes tools to align data sets obtained in different wavelengths and at different times utilizing the optical flow method. We present the image registration and coalignment workflow. The aliment accuracy of each alignment method is tested with the aid of radiative magnetohydrodynamics simulation data. We update the pointing information in GST data fits headers and generate GST and SDO imaging data products as science-ready four-dimensional (
x
,
y
,
λ
,
t
) data cubes.
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