Flare Observations Benz, Arnold O.
Living reviews in solar physics,
12/2017, Letnik:
14, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Solar flares are observed at all wavelengths from decameter radio waves to gamma-rays beyond 1 GeV. This review focuses on recent observations in EUV, soft and hard X-rays, white light, and radio ...waves. Space missions such as RHESSI, Yohkoh, TRACE, SOHO, and more recently Hinode and SDO have enlarged widely the observational base. They have revealed a number of surprises: Coronal sources appear before the hard X-ray emission in chromospheric footpoints, major flare acceleration sites appear to be independent of coronal mass ejections, electrons, and ions may be accelerated at different sites, there are at least 3 different magnetic topologies, and basic characteristics vary from small to large flares. Recent progress also includes improved insights into the flare energy partition, on the location(s) of energy release, tests of energy release scenarios and particle acceleration. The interplay of observations with theory is important to deduce the geometry and to disentangle the various processes involved. There is increasing evidence supporting magnetic reconnection as the basic cause. While this process has become generally accepted as the trigger, it is still controversial how it converts a considerable fraction of the energy into non-thermal particles. Flare-like processes may be responsible for large-scale restructuring of the magnetic field in the corona as well as for its heating. Large flares influence interplanetary space and substantially affect the Earth’s ionosphere. Flare scenarios have slowly converged over the past decades, but every new observation still reveals major unexpected results, demonstrating that solar flares, after 150 years since their discovery, remain a complex problem of astrophysics including major unsolved questions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The first flare on the Sun was observed exactly 150 years ago. During most of the long history, only secondary effects have been noticed, so flares remained a riddle. Now the primary flare products, ...high-energy electrons and ions, can be spatially resolved in hard X-rays (HXRs) and gamma rays on the Sun. Soft X-rays (SXRs) are observed from most stars, including young stellar objects. Structure and bulk motions of the corona are imaged on the Sun in high temperature lines and are inferred from line shifts in stellar coronae. Magnetic reconnection is the trigger for reorganization of the magnetic field into a lower energy configuration. A large fraction of the energy is converted into nonthermal particles that transport the energy to higher density gas, heating it to SXR-emitting temperatures. Flares on young stars are several orders of magnitude more luminous and more frequent; they significantly ionize protoplanetary disks and planetary ionospheres. PUBLICATION ABSTRACT
Flare Observations Benz, Arnold O.
Living reviews in solar physics,
01/2008, Letnik:
5, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Solar flares are observed at all wavelengths from decameter radio waves to gamma-rays at 100 MeV. This review focuses on recent observations in EUV, soft and hard X-rays, white light, and radio ...waves. Space missions such as RHESSI, Yohkoh, TRACE, and SOHO have enlarged widely the observational base. They have revealed a number of surprises: Coronal sources appear before the hard X-ray emission in chromospheric footpoints, major flare acceleration sites appear to be independent of coronal mass ejections (CMEs), electrons, and ions may be accelerated at different sites, there are at least 3 different magnetic topologies, and basic characteristics vary from small to large flares. Recent progress also includes improved insights into the flare energy partition, on the location(s) of energy release, tests of energy release scenarios and particle acceleration. The interplay of observations with theory is important to deduce the geometry and to disentangle the various processes involved. There is increasing evidence supporting reconnection of magnetic field lines as the basic cause. While this process has become generally accepted as the trigger, it is still controversial how it converts a considerable fraction of the energy into non-thermal particles. Flare-like processes may be responsible for large-scale restructuring of the magnetic field in the corona as well as for its heating. Large flares influence interplanetary space and substantially affect the Earth’s lower ionosphere. While flare scenarios have slowly converged over the past decades, every new observation still reveals major unexpected results, demonstrating that solar flares, after 150 years since their discovery, remain a complex problem of astrophysics including major unsolved questions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Although some pharmacokinetic studies have tested a higher than usual amount of grapefruit juice to determine the maximum effect, this should not be interpreted to mean that a relevant ...pharmacokinetic interaction will only occur with high levels of consumption. Indeed, a single usual amount (i.e., 200-250 mL juice or a whole grapefruit) has sufficient potency to cause a pertinent pharmacokinetic interaction.8,11,12 For example, felodipine combined with such a quantity of grapefruit had an average systemic drug concentration that was 3-fold that seen with water.8,11With twice the amount of grapefruit, there was only a modestly greater increase in the systemic concentration of felodipine, showing that a near-maximal pharmacokinetic interaction had already occurred with the consumption of the single quantity.11 With repeated ingestion of grapefruit (250 mL of juice, 3 times/d for 6 d), a single dose of felodipine increased to 5 times the systemic concentration seen with water, suggesting that frequent consumption of a usual quantity daily augmented the pharmacokinetic effect moreso than the lone quantity.8 Taking atorvastatin in the evening and drinking grapefruit juice in the morning (300 mL/d from a specific lot prepared by the Florida Department of Citrus) resulted in drug serum concentrations that were 119%-126% of those seen with no consumption of grapefruit, with no evidence of skeletal muscle toxicity (e.g., elevated creatine phosphokinase, myalgia).43 In addition, pravastatin does not produce a pharmacokinetic interaction with grapefruit,39,40 rosuvastatin is eliminated unchanged,35 and fluvastatin is metabolized by an enzyme (cytochrome P450 2C9) that is not affected by grapefruit.35 Although staggering the ingestion of atorvastatin and grapefruit may reduce risk, substituting pravastatin, rosuvastatin or fluvastatin, or eliminating grapefruit juice from the diet, appears more preferable. We conducted a comprehensive search of the PubMed database for all available scientifically valid evidence using the keyword "grapefruit" and the following additional terms: "drug," "drug interaction," "pharmacokinetics," "cytochrome P450," "CYP3A4," "case report" or "review." In addition, we obtained product monographs and prescribing information for drugs recently introduced (i.e., in the last 4 yr) to the Canadian market. We assessed the following sections of these documents for relevant information: "Summary Product Information," "Warnings and Precautions," "Contraindications," "Adverse Reactions," "Drug Interactions" and "Action and Clinical Pharmacology." We identified 190 relevant publications (161 articles from PubMed; 29 product monographs or prescribing information sheets). Most of the information was from randomized controlled clinical trials (n = 102). The measured outcome from these studies was change in drug pharmacokinetics, and this was used to assess the potential for adverse clinical consequences.
We present a new analysis framework called “Correlation Analysis Tool using the Schrödinger equation” (CATS) which computes the two-particle femtoscopy correlation function
C
(
k
), with
k
being the ...relative momentum for the particle pair. Any local interaction potential and emission source function can be used as an input and the wave function is evaluated exactly. In this paper we present a study on the sensitivity of
C
(
k
) to the interaction potential for different particle pairs: p–p, p–
Λ
,
K
-
–p,
K
+
–p, p–
Ξ
-
and
Λ
–
Λ
. For the p–p Argonne
v
18
and Reid Soft-Core potentials have been tested. For the other pair systems we present results based on strong potentials obtained from effective Lagrangians such as
χ
EFT for p–
Λ
, Jülich models for
K
(
K
¯
)
–N and Nijmegen models for
Λ
–
Λ
. For the p–
Ξ
-
pairs we employ the latest lattice results from the HAL QCD collaboration. Our detailed study of different interacting particle pairs as a function of the source size and different potentials shows that femtoscopic measurements can be exploited in order to constrain the final state interactions among hadrons. In particular, small collision systems of the order of 1 fm, as produced in pp collisions at the LHC, seem to provide a suitable environment for quantitative studies of this kind.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Our recent study demonstrated that Rac1 and NADPH oxidase activation contributes to cardiomyocyte apoptosis in short-term diabetes. This study was undertaken to investigate if disruption of Rac1 and ...inhibition of NADPH oxidase would prevent myocardial remodeling in chronic diabetes.
Diabetes was induced by injection of streptozotocin in mice with cardiomyocyte-specific Rac1 knockout and their wild-type littermates. In a separate experiment, wild-type diabetic mice were treated with vehicle or apocynin in drinking water. Myocardial hypertrophy, fibrosis, endoplasmic reticulum (ER) stress, inflammatory response, and myocardial function were investigated after 2 months of diabetes. Isolated adult rat cardiomyocytes were cultured and stimulated with high glucose.
In diabetic hearts, NADPH oxidase activation, its subunits' expression, and reactive oxygen species production were inhibited by Rac1 knockout or apocynin treatment. Myocardial collagen deposition and cardiomyocyte cross-sectional areas were significantly increased in diabetic mice, which were accompanied by elevated expression of pro-fibrotic genes and hypertrophic genes. Deficiency of Rac1 or apocynin administration reduced myocardial fibrosis and hypertrophy, resulting in improved myocardial function. These effects were associated with a normalization of ER stress markers' expression and inflammatory response in diabetic hearts. In cultured cardiomyocytes, high glucose-induced ER stress was inhibited by blocking Rac1 or NADPH oxidase.
Rac1 via NADPH oxidase activation induces myocardial remodeling and dysfunction in diabetic mice. The role of Rac1 signaling may be associated with ER stress and inflammation. Thus, targeting inhibition of Rac1 and NADPH oxidase may be a therapeutic approach for diabetic cardiomyopathy.
About 10 μs after the Big Bang, the universe was filled—in addition to photons and leptons—with strong-interaction matter consisting of quarks and gluons, which transitioned to hadrons at ...temperatures close to kT = 150 MeV and densities several times higher than those found in nuclei. This quantum chromodynamics (QCD) matter can be created in the laboratory as a transient state by colliding heavy ions at relativistic energies. The different phases in which QCD matter may exist depend for example on temperature, pressure or baryochemical potential, and can be probed by studying the emission of electromagnetic radiation. Electron–positron pairs emerge from the decay of virtual photons, which immediately decouple from the strong interaction, and thus provide information about the properties of QCD matter at various stages. Here, we report the observation of virtual photon emission from baryon-rich QCD matter. The spectral distribution of the electron–positron pairs is nearly exponential, providing evidence for a source of temperature in excess of 70 MeV with constituents whose properties have been modified, thus reflecting peculiarities of strong-interaction QCD matter. Its bulk properties are similar to the dense matter formed in the final state of a neutron star merger, as apparent from recent multimessenger observation.
The preflare phase of the flare SOL2011-08-09T03:52 is unique in its long duration, in that it was covered by the
Reuven Ramaty High Energy Solar Spectroscopic Imager
(RHESSI) and the
Nobeyama ...Radioheliograph
, and because it showed three well-developed soft X-ray (SXR) peaks. No hard X-rays (HXR) are observed in the preflare phase. Here we report that no associated radio emission at 17 GHz was found either, despite the higher sensitivity of the radio instrument. The ratio between the SXR peaks and the upper limit of the radio peaks is higher by more than one order of magnitude than the ratio in regular flares. The result suggests that the ratio between acceleration and heating in the preflare phase was different than in regular flares. Acceleration to relativistic energies, if any, occurred with lower efficiency.
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