Search results for "sun: activity"
showing 10 items of 21 documents
Post-flare evolution of AR 10923 with Hinode/XRT
2010
Flares are dynamic events which involve rapid changes in coronal magnetic topology end energy release. Even if they may be localized phenomena, the magnetic disturbance at their origin may propagate and be effective in a larger part of the active region. We investigate the temporal evolution of a flaring active region with respect to the loops morphology, the temperature, and emission measure distributions. We consider $Hinode/XRT$ data of a the 2006 November 12th C1.1 flare. We inspect the evolution of the morphology of the flaring region also with the aid of TRACE data. XRT filter ratios are used to derive temperature and emission measure maps and evolution. The analyzed flare includes se…
HINODE /EIS SPECTROSCOPIC VALIDATION OF VERY HOT PLASMA IMAGED WITH THE SOLAR DYNAMICS OBSERVATORY IN NON-FLARING ACTIVE REGION CORES
2012
We use coronal imaging observations with SDO/AIA, and Hinode/EIS spectral data, to explore the potential of narrow band EUV imaging data for diagnosing the presence of hot (T >~5MK) coronal plasma in active regions. We analyze observations of two active regions (AR 11281, AR 11289) with simultaneous AIA imaging, and EIS spectral data, including the CaXVII line (at 192.8A) which is one of the few lines in the EIS spectral bands sensitive to hot coronal plasma even outside flares. After careful coalignment of the imaging and spectral data, we compare the morphology in a 3 color image combining the 171, 335, and 94A AIA spectral bands, with the image obtained for CaXVII emission from the an…
Temperature Distribution of a Non-flaring Active Region from Simultaneous Hinode XRT and EIS Observations
2011
We analyze coordinated Hinode XRT and EIS observations of a non-flaring active region to investigate the thermal properties of coronal plasma taking advantage of the complementary diagnostics provided by the two instruments. In particular we want to explore the presence of hot plasma in non-flaring regions. Independent temperature analyses from the XRT multi-filter dataset, and the EIS spectra, including the instrument entire wavelength range, provide a cross-check of the different temperature diagnostics techniques applicable to broad-band and spectral data respectively, and insights into cross-calibration of the two instruments. The emission measure distribution, EM(T), we derive from the…
Evidence of Widespread Hot Plasma in a Nonflaring Coronal Active Region from Hinode/X-Ray Telescope
2009
Nanoflares, short and intense heat pulses within spatially unresolved magnetic strands, are now considered a leading candidate to solve the coronal heating problem. However, the frequent occurrence of nanoflares requires that flare-hot plasma be present in the corona at all times. Its detection has proved elusive until now, in part because the intensities are predicted to be very faint. Here, we report on the analysis of an active region observed with five filters by Hinode/X-Ray Telescope (XRT) in 2006 November. We have used the filter ratio method to derive maps of temperature and emission measure (EM) both in soft and hard ratios. These maps are approximate in that the plasma is assumed …
Photospheric response to an ellerman bomb-like event—an analogy of Sunrise/IMaX observations and MHD simulations
2017
S. Danilovic et. al.
TIME-RESOLVED EMISSION FROM BRIGHT HOT PIXELS OF AN ACTIVE REGION OBSERVED IN THE EUV BAND WITH SDO/AIA AND MULTI-STRANDED LOOP MODELING
2015
Evidence for small amounts of very hot plasma has been found in active regions and might be the indication of an impulsive heating, released at spatial scales smaller than the cross section of a single loop. We investigate the heating and substructure of coronal loops in the core of one such active region by analyzing the light curves in the smallest resolution elements of solar observations in two EUV channels (94 A and 335 A) from the Atmospheric Imaging Assembly on-board the Solar Dynamics Observatory. We model the evolution of a bundle of strands heated by a storm of nanoflares by means of a hydrodynamic 0D loop model (EBTEL). The light curves obtained from the random combination of tho…
The Sun as an X-ray star: Active region evolution, rotational modulation, and implications for stellar X-ray variability
2004
We study the contribution of an active region and its core to the luminosity and the spectrum of the Sun in the X-ray band and to the relevant solar emission measure vs. temperature distribution, EM(T). We also study the relevant changes in the course of four solar rotations, and the solar rotational modulation due to this active region, the only one present at that time. To this end, we have used a large sample of full-disk Yohkoh/SXT observations taken between July and October 1996, covering most of the active region evolution. From the Yohkoh/SXT data we have synthesized the X-ray spectra of the whole solar corona, and the focal plane data as they would be collected with Rosat/PSPC, XMM-…
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…
Asymmetric Twisting of Coronal Loops
2023
The bright solar corona entirely consists of closed magnetic loops rooted in the photosphere. Photospheric motions are important drivers of magnetic stressing, which eventually leads to energy release into heat. These motions are chaotic and obviously different from one footpoint to the other, and in fact, there is strong evidence that loops are finely stranded. One may also expect strong transient variations along the field lines, but at a glance, coronal loops ever appear more or less uniformly bright from one footpoint to the other. We aim to understand how much coronal loops can preserve their own symmetry against asymmetric boundary motions that are expected to occur at loop footpoints…
Sphinx measurements of the 2009 solar minimum x-ray emission
2012
The SphinX X-ray spectrophotometer on the CORONAS-PHOTON spacecraft measured soft X-ray emission in the 1-15 keV energy range during the deep solar minimum of 2009 with a sensitivity much greater than GOES. Several intervals are identified when the X-ray flux was exceptionally low, and the flux and solar X-ray luminosity are estimated. Spectral fits to the emission at these times give temperatures of 1.7-1.9 MK and emission measures between 4 x 10^47 cm^-3 and 1.1 x 10^48 cm^-3. Comparing SphinX emission with that from the Hinode X-ray Telescope, we deduce that most of the emission is from general coronal structures rather than confined features like bright points. For one of 27 intervals o…