Parameters of the flare and surrounding medium and their evolution during 20 January 2005 solar event

NASA Astrophysics Data System (ADS)

Troitskaia, E.; Arkhangelskaja, I.; Arkhangelsky, A.; Gan, W.

2013-02-01

Basing on the data of AVS-F apparatus from SONG-D detector onboard CORONAS-F satellite, we have studied the extreme solar event of January 20, 2005 used the 2.223 MeV, 4.44 MeV and 6.13 MeV γ-lines temporal profiles. By the statistical modeling method we calculated the temporal profile of 2.223 MeV line too. Calculations have been performed in assumption of Bessel type of accelerated particles energy spectrum, different 3He content in the region of nuclear reactions and several density models of the solar atmosphere. Comparisons of the results of modeling with observational 2.223 MeV AVS-F/SONG-D data reveal the increasing of the ratio of 3He concentration to 1H one during the flare from 2× 10-5 at the rise phase of the gamma-ray flux up to 2× 10--4 at the decay one. During the same period the spectrum became harder and the density of solar atmosphere increased too. Averaged over full time of 2.223 MeV γ-emission concentration ratio of 3He/1H is equal to (1.40±0.15)×10--4, also the density model with enlarged density up to 2×1017 cm-3 in the lower chromosphere and through the whole photosphere is realized. Besides, we have estimated the spectral index αT that is close to 0.1 for accelerated protons in the range of 1-100 MeV. Using the AVS-F gamma-rays spectral data in the wide range up to 140 MeV, we have obtained the spectral index of s=2.5±0.1 in the case of power law spectrum for energies more than 300 MeV.

A simple model of chromospheric evaporation and condensation driven conductively in a solar flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longcope, D. W.

2014-11-01

Magnetic energy released in the corona by solar flares reaches the chromosphere where it drives characteristic upflows and downflows known as evaporation and condensation. These flows are studied here for the case where energy is transported to the chromosphere by thermal conduction. An analytic model is used to develop relations by which the density and velocity of each flow can be predicted from coronal parameters including the flare's energy flux F. These relations are explored and refined using a series of numerical investigations in which the transition region (TR) is represented by a simplified density jump. The maximum evaporation velocity,more » for example, is well approximated by v{sub e} ≅ 0.38(F/ρ{sub co,} {sub 0}){sup 1/3}, where ρ{sub co,} {sub 0} is the mass density of the pre-flare corona. This and the other relations are found to fit simulations using more realistic models of the TR both performed in this work, and taken from a variety of previously published investigations. These relations offer a novel and efficient means of simulating coronal reconnection without neglecting entirely the effects of evaporation.« less

The most powerful flaring activity from the NLSy1 PMN J0948+0022

NASA Astrophysics Data System (ADS)

D'Ammando, F.; Orienti, M.; Finke, J.; Raiteri, C. M.; Hovatta, T.; Larsson, J.; Max-Moerbeck, W.; Perkins, J.; Readhead, A. C. S.; Richards, J. L.; Beilicke, M.; Benbow, W.; Berger, K.; Bird, R.; Bugaev, V.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Ciupik, L.; Dickinson, H. J.; Eisch, J. D.; Errando, M.; Falcone, A.; Finley, J. P.; Fleischhack, H.; Fortin, P.; Fortson, L.; Furniss, A.; Gerard, L.; Gillanders, G. H.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Håkansson, N.; Holder, J.; Humensky, T. B.; Kar, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nieto, D.; de Bhróithe, A. O'Faoláin; Ong, R. A.; Otte, A. N.; Pohl, M.; Popkow, A.; Prokoph, H.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rousselle, J.; Santander, M.; Sembroski, G. H.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Vassiliev, V. V.; Wakely, S. P.; Weinstein, A.; Welsing, R.; Williams, D. A.; Zitzer, B.

2015-01-01

We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in γ-rays, PMN J0948+0022 (z = 0.5846). A γ-ray flare was observed by the Large Area Telescope on board Fermi during 2012 December-2013 January, reaching a daily peak flux in the 0.1-100 GeV energy range of (155 ± 31) × 10-8 ph cm-2 s-1 on 2013 January 1, corresponding to an apparent isotropic luminosity of ˜1.5 × 1048 erg s-1. The γ-ray flaring period triggered Swift and Very Energetic Radiation Imaging Telescope Array System (VERITAS) observations in addition to radio and optical monitoring by Owens Valley Radio Observatory, Monitoring Of Jets in Active galactic nuclei with VLBA Experiments, and Catalina Real-time Transient Survey. A strong flare was observed in optical, UV, and X-rays on 2012 December 30, quasi-simultaneously to the γ-ray flare, reaching a record flux for this source from optical to γ-rays. VERITAS observations at very high energy (E > 100 GeV) during 2013 January 6-17 resulted in an upper limit of F>0.2 TeV < 4.0 × 10-12 ph cm-2 s-1. We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field.

The Most Powerful Flaring Activity from the NLSy1 PMN J0948+0022

NASA Technical Reports Server (NTRS)

D'Ammando, F.; Orienti, M.; Finke, J.; Raiteri, C. M.; Hovatta, T.; Larsson, J.; Max-Moerbeck, W.; Perkins, J.; Readhead, A. C. S.; Richards, J. L.

2014-01-01

We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma rays, PMN J0948+0022 (z equal to 0.5846). A gamma-ray flare was observed by the Large Area Telescope on board Fermi during 2012 December-2013 January, reaching a daily peak flux in the 0.1-100 GeV energy range of (155 plus or minus 31)×10(exp -8) ph cm (exp -2) s (exp -1) on 2013 January 1, corresponding to an apparent isotropic luminosity of approximately 1.5×10)exp 48) erg s(exp -1). The gamma-ray flaring period triggered Swift and VERITAS observations in addition to radio and optical monitoring by OVRO, MOJAVE, and CRTS. A strong flare was observed in optical, UV, and X- rays on 2012 December 30, quasi-simultaneously to the gamma-ray flare, reaching a record flux for this source from optical to gamma rays. VERITAS observations at very high energy (E greater than 100 GeV) during 2013 January 6-17 resulted in an upper limit of F(sub greater than 0.2 TeV) less than 4.0 × 10(exp -12) ph cm(exp -2) s(exp -1). We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field.

WE-FG-202-05: Quantification of Bone Flare On [F-18] NaF PET/CT in Metastatic Prostate Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weisman, A; Harmon, S; Perk, T

Purpose: Bone flare has been observed on Tc-99m bone scans during early assessment in metastatic Castration-Resistant Prostate Cancer (mCRPC) patients receiving select androgen-signaling pathway (AR) targeted treatments, including CYP17-inhibitor Abiraterone. This study investigates the appearance and potential clinical impact of bone flare in mCRPC patients receiving CYP17-inhibitors using {sup 18}F-NaF PET/CT. Methods: Twenty-three mCRPC patients being treated with CYP17-inhibitors received NaF PET/CT scans at baseline, week 6, and week 12 of treatment. Individual lesions were identified using a SUV>15 threshold within skeletal regions and articulated bone registration was used to track lesions between scans. Standard SUV metrics were extracted globallymore » for each patient (pSUV) and for each individual lesion (iSUV). Differences in metrics across time-points were compared using Wilcoxon signed-rank tests. Cox proportional hazard regression analyses were conducted between global metrics and progression-free survival (PFS). Results: Nineteen patients (83%) showed increasing NaF PET global metrics at week 6, with pSUV{sub total} reflecting consensus change across other global metrics with median increase +33% (range +2 to 205%). Of these patients, 14 showed subsequent decrease in pSUV{sub total}, with a median of −17% (range −76 to −1%), indicating flare phenomenon. Increasing pSUV{sub mean} at week 6 correlated with extended clinical PFS (HR = 0.58, p=0.02). New lesions did not account for the initial increase in global NaF metrics. Lesion-level analysis reveals 316 lesions in the 14 patients exhibiting global flare. On average, 75% (sd: 22%) of lesions follow global trends with iSUV{sub total} increasing at week 6 and 65% (sd: 17%) showing iSUV{sub total} decrease at week 12. Conclusion: Bone flare was detected on NaF PET/CT in the first 6 weeks of treatment for mCRPC patients receiving CYP17-inhibitors, subsiding by week 12. Characterization provided in this study suggests prolonged PFS in patients showing bone flare early in select AR-directed treatments. Prostate Cancer Foundation.« less

The Width of a Solar Coronal Mass Ejection and the Source of the Driving Magnetic Explosion: A Test of the Standard Scenario for CME Production

NASA Technical Reports Server (NTRS)

Moore, Ronald L.; Sterling, Alphonse C.; Suess, Steven T.

2007-01-01

We show that the strength (B(sub F1are)) of the magnetic field in the area covered by the flare arcade following a CME-producing ejective solar eruption can be estimated from the final angular width (Final Theta(sub CME)) of the CME in the outer corona and the final angular width (Theta(sub Flare)) of the flare arcade: B(sub Flare) approx. equals 1.4[(Final Theta(sub CME)/Theta(sub Flare)] (exp 2)G. We assume (1) the flux-rope plasmoid ejected from the flare site becomes the interior of the CME plasmoid; (2) in the outer corona (R > 2 (solar radius)) the CME is roughly a "spherical plasmoid with legs" shaped like a lightbulb; and (3) beyond some height in or below the outer corona the CME plasmoid is in lateral pressure balance with the surrounding magnetic field. The strength of the nearly radial magnetic field in the outer corona is estimated from the radial component of the interplanetary magnetic field measured by Ulysses. We apply this model to three well-observed CMEs that exploded from flare regions of extremely different size and magnetic setting. One of these CMEs was an over-and-out CME, that is, in the outer corona the CME was laterally far offset from the flare-marked source of the driving magnetic explosion. In each event, the estimated source-region field strength is appropriate for the magnetic setting of the flare. This agreement (1) indicates that CMEs are propelled by the magnetic field of the CME plasmoid pushing against the surrounding magnetic field; (2) supports the magnetic-arch-blowout scenario for over-and-out CMEs; and (3) shows that a CME's final angular width in the outer corona can be estimated from the amount of magnetic flux covered by the source-region flare arcade.

The most powerful flaring activity from the NLSy1 PMN J0948+0022

DOE PAGES

D'Ammando, F.; Orienti, M.; Finke, J.; ...

2014-11-27

Here, we report on multifrequency observations performed during 2012 December–2013 August of the first narrow-line Seyfert 1 galaxy detected in γ-rays, PMN J0948+0022 (z = 0.5846). A γ-ray flare was observed by the Large Area Telescope on board Fermi during 2012 December–2013 January, reaching a daily peak flux in the 0.1–100 GeV energy range of (155 ± 31) × 10 –8 ph cm –2 s –1 on 2013 January 1, corresponding to an apparent isotropic luminosity of ~1.5 × 10 48 erg s –1. The γ-ray flaring period triggered Swift and Very Energetic Radiation Imaging Telescope Array System (VERITAS) observationsmore » in addition to radio and optical monitoring by Owens Valley Radio Observatory, Monitoring Of Jets in Active galactic nuclei with VLBA Experiments, and Catalina Real-time Transient Survey. A strong flare was observed in optical, UV, and X-rays on 2012 December 30, quasi-simultaneously to the γ-ray flare, reaching a record flux for this source from optical to γ-rays. VERITAS observations at very high energy (E > 100 GeV) during 2013 January 6–17 resulted in an upper limit of F >0.2 TeV < 4.0 × 10 –12 ph cm –2 s –1. We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. Here, the two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field.« less

Mental health, fatigue and function are associated with increased risk of disease flare following TNF inhibitor tapering in patients with rheumatoid arthritis: an exploratory analysis of data from the Optimizing TNF Tapering in RA (OPTTIRA) trial.

PubMed

Bechman, Katie; Sin, Fang En; Ibrahim, Fowzia; Norton, Sam; Matcham, Faith; Scott, David Lloyd; Cope, Andrew; Galloway, James

2018-01-01

Tapering of anti-tumour necrosis factor (TNF) therapy appears feasible, safe and effective in selected patients with rheumatoid arthritis (RA). Depression is highly prevalent in RA and may impact on flare incidence through various mechanisms. This study aims to investigate if psychological states predict flare in patients' dose tapering their anti-TNF therapy. This study is a post-hoc analysis of the Optimizing TNF Tapering in RA trial, a multicentre, randomised, open-label study investigating anti-TNF tapering in RA patients with sustained low disease activity. Patient-reported outcomes (Health Assessment Questionnaire, EuroQol 5-dimension scale, Functional Assessment of Chronic Illness Therapy fatigue scale (FACIT-F), 36-Item Short Form Survey (SF-36)) were collected at baseline. The primary outcome was flare, defined as an increase in 28-joint count Disease Activity Score (DAS28) ≥0.6 and ≥1 swollen joint. Discrete-time survival models were used to identify patient-reported outcomes that predict flare. Ninety-seven patients were randomised to taper their anti-TNF dose by either 33% or 66%. Forty-one patients flared. Higher baseline DAS28 score was associated with flare (adjusted HR 1.96 (95% CI 1.18 to 3.24), p=0.01). Disability (SF-36 physical component score), fatigue (FACIT-F) and mental health (SF-36 mental health subscale (MH)) predicted flare in unadjusted models. In multivariate analyses, only SF-36 MH remained a statistically significant predictor of flare (adjusted HR per 10 units 0.74 (95% CI 0.60 to 0.93), p=0.01). Baseline DAS28 and mental health status are independently associated with flare in patients who taper their anti-TNF therapy. Fatigue and function also associate with flare but the effect disappears when adjusting for confounders. Given these findings, mental health and functional status should be considered in anti-TNF tapering decisions in order to optimise the likelihood of success. EudraCT Number: 2010-020738-24; ISRCTN: 28955701; Post-results.

Mental health, fatigue and function are associated with increased risk of disease flare following TNF inhibitor tapering in patients with rheumatoid arthritis: an exploratory analysis of data from the Optimizing TNF Tapering in RA (OPTTIRA) trial

PubMed Central

Bechman, Katie; Sin, Fang En; Ibrahim, Fowzia; Norton, Sam; Matcham, Faith; Scott, David Lloyd; Cope, Andrew; Galloway, James

2018-01-01

Background Tapering of anti-tumour necrosis factor (TNF) therapy appears feasible, safe and effective in selected patients with rheumatoid arthritis (RA). Depression is highly prevalent in RA and may impact on flare incidence through various mechanisms. This study aims to investigate if psychological states predict flare in patients’ dose tapering their anti-TNF therapy. Methods This study is a post-hoc analysis of the Optimizing TNF Tapering in RA trial, a multicentre, randomised, open-label study investigating anti-TNF tapering in RA patients with sustained low disease activity. Patient-reported outcomes (Health Assessment Questionnaire, EuroQol 5-dimension scale, Functional Assessment of Chronic Illness Therapy fatigue scale (FACIT-F), 36-Item Short Form Survey (SF-36)) were collected at baseline. The primary outcome was flare, defined as an increase in 28-joint count Disease Activity Score (DAS28) ≥0.6 and ≥1 swollen joint. Discrete-time survival models were used to identify patient-reported outcomes that predict flare. Results Ninety-seven patients were randomised to taper their anti-TNF dose by either 33% or 66%. Forty-one patients flared. Higher baseline DAS28 score was associated with flare (adjusted HR 1.96 (95% CI 1.18 to 3.24), p=0.01). Disability (SF-36 physical component score), fatigue (FACIT-F) and mental health (SF-36 mental health subscale (MH)) predicted flare in unadjusted models. In multivariate analyses, only SF-36 MH remained a statistically significant predictor of flare (adjusted HR per 10 units 0.74 (95% CI 0.60 to 0.93), p=0.01). Conclusions Baseline DAS28 and mental health status are independently associated with flare in patients who taper their anti-TNF therapy. Fatigue and function also associate with flare but the effect disappears when adjusting for confounders. Given these findings, mental health and functional status should be considered in anti-TNF tapering decisions in order to optimise the likelihood of success. Trial registration numbers EudraCT Number: 2010-020738-24; ISRCTN: 28955701; Post-results. PMID:29862047

Solar-Terrestrial Predictions

NASA Astrophysics Data System (ADS)

Thompson, R. J.; Cole, D. G.; Wilkinson, P. J.; Shea, M. A.; Smart, D.

1990-11-01

Volume 1: The following subject areas are covered: the magnetosphere environment; forecasting magnetically quiet periods; radiation hazards to human in deep space (a summary with special reference to large solar particle events); solar proton events (review and status); problems of the physics of solar-terrestrial interactions; prediction of solar proton fluxes from x-ray signatures; rhythms in solar activity and the prediction of episodes of large flares; the role of persistence in the 24-hour flare forecast; on the relationship between the observed sunspot number and the number of solar flares; the latitudinal distribution of coronal holes and geomagnetic storms due to coronal holes; and the signatures of flares in the interplanetary medium at 1 AU. Volume 2: The following subject areas were covered: a probability forecast for geomagnetic activity; cost recovery in solar-terrestrial predictions; magnetospheric specification and forecasting models; a geomagnetic forecast and monitoring system for power system operation; some aspects of predicting magnetospheric storms; some similarities in ionospheric disturbance characteristics in equatorial, mid-latitude, and sub-auroral regions; ionospheric support for low-VHF radio transmission; a new approach to prediction of ionospheric storms; a comparison of the total electron content of the ionosphere around L=4 at low sunspot numbers with the IRI model; the French ionospheric radio propagation predictions; behavior of the F2 layer at mid-latitudes; and the design of modern ionosondes.

Survey of localized solar flare signatures in the ionosphere with GNSS, VLF, and GOES observations

NASA Astrophysics Data System (ADS)

Blevins, S. M.; Hayes, L.; Collado-Vega, Y. M.; Michael, B. P.; Noll, C. E.

2017-12-01

Global navigation satellite system (GNSS) phase measurements of the total electron content (TEC) and ionospheric delay are sensitive to sudden increases in electron density in the layers of the Earth's ionosphere. These sudden ionospheric disruptions, or SIDs, are due to enhanced X-ray and extreme ultraviolet radiation from a solar flare that drastically increases the electron density in localized regions. SIDs are solar flare signatures in the Earth's ionosphere and can be observed with very low frequency (VLF 3-30 kHz) monitors and dual-frequency GNSS (L1 = 1575.42 MHz, L2 = 1227.60 MHz) receivers that probe lower (D-region) to upper (F-region) ionospheric layers, respectively. Data from over 500 solar flare events, spanning April 2010 to July 2017, including GOES C-, M-, and X-class solar flares at various intensities, were collected from the Space Weather Database Of Notifications, Knowledge, Information (DONKI) developed at the NASA Goddard Space Flight Center (GSFC) Community Coordinated Modeling Center (CCMC). Historical GOES satellite (NOAA) X-ray flux (NASA GSFC CCMC integrated Space Weather Analysis system (iSWA)), and VLF SID (Stanford University Solar SID Space Weather Monitor program) time series data are available for all solar flare events of the sample set. We use GNSS data archived at the NASA GSFC Crustal Dynamics Data Information System (CDDIS) to characterize the F-region reactions to the increased ionization, complementing the ground-based D-region (VLF), and space-based X-ray observations (GOES). CDDIS provides GNSS data with 24-hour coverage at a temporal resolution of 30 seconds from over 500 stations. In our study we choose 63 stations, spanning 23 countries at a variety of geographic locations to provide continuous coverage for all solar flare events in the sample. This geographic distribution enables us to explore the effects of different solar flare intensities at localized regions in the Earths ionosphere around the globe. The GNSS observations are combined with VLF SID and GOES data to characterize and compare the impact of over 500 solar flare events through the upper and lower layers of the ionosphere. The sample set, data extraction and analysis methods, and preliminary results will be presented.

The emission in the region E>0.1MeV during disk and limb faint solar flares

NASA Astrophysics Data System (ADS)

Irene, Arkhangelskaja; Andrew, Arkhangelskiy; Yury, Kotov; Alexandr, Glyanenko; Maria, Kolchina; Alexey, Kirichenko

2013-06-01

Hard X-ray and gamma-ray emission in energy band E>50 keV was first observed by AVS-F apparatus onboard CORONAS-F satellite (detector SONG-D) during some solar flares with classes B and C by GOES classification. Such component registered in flares with duration less than 30 min. However γ-emission up to several tens of MeV was observed during some classes B and C events, which temporal profiles were not corresponded to Neupert effect. For example, during class B2.3 limb solar flare January 7, 2005 maximum observed energy was Emax˜36 MeV and during class B4.6 disk solar event January 12, 2005 maximum observed energy was Emax˜7 MeV. Properties of temporal profiles and energy spectra of faint solar flares, during which emission in the energy band of E>0.1 MeV were registered are discussed in the presented work. There is not any strong correlation between presence or absence of hard X-ray and γ-ray emission and the intensity of soft X-ray emission during solar flares. The one of illustration of this fact is the absence of any observed statistically significant count rate exceed above background level during some class M flares in the energy band E>0.1 MeV. The typical example of such flares is event November 8, 2001 (class M4.2, lasts from 14:59 UT up to 16:00 UT, maximum of soft X-ray emission was at 15:35 UT on GOES data).

Solar flare predictions and warnings

NASA Technical Reports Server (NTRS)

White, K. P., III

1972-01-01

The real-time solar monitoring information supplied to support SPARCS equipped rocket launches, the routine collection and analysis of 3.3-mm solar radio maps, short-term flare forecasts based on these maps, longer-term forecasts based on the recurrence of active regions, and an extension of the flare forecasting technique are summarized. Forecasts for expectation of a solar flare of class or = 2F are given and compared with observed flares. A total of 52 plage regions produced all the flares of class or = 1N during the study period. The following results are indicated: of the total of 21 positive forecasts, 3 were correct and 18 were incorrect; of the total of 31 negative forecasts, 3 were incorrect and 28 were correct; of a total of 6 plage regions producing large flares, 3 were correctly forecast and 3 were missed; and of 46 regions not producing any large flares, 18 were incorrectly forecast and 28 were correctly forecast.

Stellar Flares Observed in Long-cadence Data from the Kepler Mission

NASA Astrophysics Data System (ADS)

Van Doorsselaere, Tom; Shariati, Hoda; Debosscher, Jonas

2017-10-01

We aim to perform a statistical study of stellar flares observed by Kepler. We want to study the flare amplitude, duration, energy, and occurrence rates, and how they are related to the spectral type and rotation period. To that end, we have developed an automated flare detection and characterization algorithm. We have harvested the stellar parameters from the Kepler input catalog and the rotation periods from McQuillan et al. We find several new candidate A stars showing flaring activity. Moreover, we find 653 giants with flares. From the statistical distribution of flare properties, we find that the flare amplitude distribution has a similar behavior between F+G types and K+M types. The flare duration and flare energy seem to be grouped between G+K+M types versus F types and giants. We also detect a tail of stars with high flare occurrence rates across all spectral types (but most prominent in the late spectral types), and this is compatible with the existence of “flare stars.” Finally, we have found a strong correlation of the flare occurrence rate and the flare amplitude with the stellar rotation period: a quickly rotating star is more likely to flare often and has a higher chance of generating large flares.

Homologous Circular-ribbon Flares Driven by Twisted Flux Emergence

NASA Astrophysics Data System (ADS)

Xu, Z.; Yang, K.; Guo, Y.; Zhao, J.; Zhao, Z. J.; Kashapova, L.

2017-12-01

In this paper, we report two homologous circular-ribbon flares associated with two filament eruptions. They were well observed by the New Vacuum Solar Telescope and the Solar Dynamics Observatory on 2014 March 5. Prior to the flare, two small-scale filaments enclosed by a circular pre-flare brightening lie along the circular polarity inversion line around the parasitic polarity, which has shown a continuous rotation since its first appearance. Two filaments eventually erupt in sequence associated with two homologous circular-ribbon flares and display an apparent writhing signature. Supplemented by the nonlinear force-free field extrapolation and the magnetic field squashing factor investigation, the following are revealed. (1) This event involves the emergence of magnetic flux ropes into a pre-existing polarity area, which yields the formation of a 3D null-point topology in the corona. (2) Continuous input of the free energy in the form of a flux rope from beneath the photosphere may drive a breakout-type reconnection occurring high in the corona, supported by the pre-flare brightening. (3) This initiation reconnection could release the constraint on the flux rope and trigger the MHD instability to first make filament F1 lose equilibrium. The subsequent more violent magnetic reconnection with the overlying flux is driven during the filament rising. In return, the eruption of filament F2 is further facilitated by the reduction of the magnetic tension force above. These two processes form a positive feedback to each other to cause the energetic mass eruption and flare.

The ionosphere of Europe and North America before the magnetic storm of October 28, 2003

NASA Astrophysics Data System (ADS)

Blagoveshchensky, D. V.; Macdugall, J. W.; Pyatkova, A. V.

2006-05-01

The X17 solar flare occurred on October 28, 2003, and was followed by the X10 flare on October 29. These flares caused very strong geomagnetic storms (Halloween storms). The aim of the present study is to compare the variations in two main ionospheric parameters ( foF2 and hmF2) at two chains of ionosondes located in Europe and North America for the period October 23-28, 2003. This interval began immediately before the storm of October 28 and includes its commencement. Another task of the work is to detect ionospheric precursors of the storm or substorm expansion phase. An analysis is based on SPIDR data. The main results are as follows. The positive peak of δ foF2 (where δ is the difference between disturbed and quiet values) is observed several hours before the magnetic storm or substorm commencement. This peak can serve as a disturbance precursor. The amplitude of δ foF2 values varies from 20 to 100% of the foF2 values. The elements of similarity in the variations in the δ foF2 values at two chains are as follows: (a) the above δ foF2 peak is as a rule observed simultaneously at two chains before the disturbance; (b) the δ foF2 variations are similar at all midlatitude (or, correspondingly, high-latitude) ionosondes of the chain. The differences in the δ foF2 values are as follows: (a) the effect of the main phase and the phase of strong storm recovery at one chain differs from such an effect at another chain; (b) the manifestation of disturbances at high-latitude stations of the chain differ from the manifestations at midlatitude stations. The δ hmF2 variations are approximately opposite to the δ foF2 variations, and the δ hmF2 values lie in the interval 15-25% of the hmF2 values. The performed study is useful and significant in studying the problems of the space weather, especially in a short-term prediction of ionospheric disturbances caused by magnetospheric storms or substorms.

RECONCILIATION OF WAITING TIME STATISTICS OF SOLAR FLARES OBSERVED IN HARD X-RAYS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aschwanden, Markus J.; McTiernan, James M., E-mail: aschwanden@lmsal.co, E-mail: jimm@ssl.berkeley.ed

2010-07-10

We study the waiting time distributions of solar flares observed in hard X-rays with ISEE-3/ICE, HXRBS/SMM, WATCH/GRANAT, BATSE/CGRO, and RHESSI. Although discordant results and interpretations have been published earlier, based on relatively small ranges (<2 decades) of waiting times, we find that all observed distributions, spanning over 6 decades of waiting times ({Delta}t {approx} 10{sup -3}-10{sup 3} hr), can be reconciled with a single distribution function, N({Delta}t) {proportional_to} {lambda}{sub 0}(1 + {lambda}{sub 0{Delta}}t){sup -2}, which has a power-law slope of p {approx} 2.0 at large waiting times ({Delta}t {approx} 1-1000 hr) and flattens out at short waiting times {Delta}t {approx}

Multi-wavelength Observations of the Flaring Gamma-ray Blazar 3C 66A in 2008 October

NASA Astrophysics Data System (ADS)

Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Costamante, L.; Cutini, S.; Davis, D. S.; Dermer, C. D.; de Palma, F.; Digel, S. W.; do Couto e Silva, E.; Drell, P. S.; Dubois, R.; Dumora, D.; Favuzzi, C.; Fegan, S. J.; Fortin, P.; Frailis, M.; Fuhrmann, L.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nestoras, I.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reyes, L. C.; Ripken, J.; Ritz, S.; Romani, R. W.; Roth, M.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Scargle, J. D.; Sgrò, C.; Shaw, M. S.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ylinen, T.; Ziegler, M.; Acciari, V. A.; Aliu, E.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Böttcher, M.; Boltuch, D.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.; Christiansen, J. L.; Ciupik, L.; Cui, W.; de la Calle Perez, I.; Dickherber, R.; Errando, M.; Falcone, A.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Godambe, S.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Holder, J.; Hui, C. M.; Humensky, T. B.; Imran, A.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; LeBohec, S.; Maier, G.; McArthur, S.; McCann, A.; McCutcheon, M.; Moriarty, P.; Mukherjee, R.; Ong, R. A.; Otte, A. N.; Pandel, D.; Perkins, J. S.; Pichel, A.; Pohl, M.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Schroedter, M.; Sembroski, G. H.; Senturk, G. Demet; Smith, A. W.; Steele, D.; Swordy, S. P.; Tešić, G.; Theiling, M.; Thibadeau, S.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Williams, D. A.; Wissel, S.; Wood, M.; Villata, M.; Raiteri, C. M.; Gurwell, M. A.; Larionov, V. M.; Kurtanidze, O. M.; Aller, M. F.; Lähteenmäki, A.; Chen, W. P.; Berduygin, A.; Agudo, I.; Aller, H. D.; Arkharov, A. A.; Bach, U.; Bachev, R.; Beltrame, P.; Benítez, E.; Buemi, C. S.; Dashti, J.; Calcidese, P.; Capezzali, D.; Carosati, D.; Da Rio, D.; Di Paola, A.; Diltz, C.; Dolci, M.; Dultzin, D.; Forné, E.; Gómez, J. L.; Hagen-Thorn, V. A.; Halkola, A.; Heidt, J.; Hiriart, D.; Hovatta, T.; Hsiao, H.-Y.; Jorstad, S. G.; Kimeridze, G. N.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Leto, P.; Ligustri, R.; Lindfors, E.; Lopez, J. M.; Marscher, A. P.; Mommert, M.; Mujica, R.; Nikolashvili, M. G.; Nilsson, K.; Palma, N.; Pasanen, M.; Roca-Sogorb, M.; Ros, J. A.; Roustazadeh, P.; Sadun, A. C.; Saino, J.; Sigua, L. A.; Sillanää, A.; Sorcia, M.; Takalo, L. O.; Tornikoski, M.; Trigilio, C.; Turchetti, R.; Umana, G.; Belloni, T.; Blake, C. H.; Bloom, J. S.; Angelakis, E.; Fumagalli, M.; Hauser, M.; Prochaska, J. X.; Riquelme, D.; Sievers, A.; Starr, D. L.; Tagliaferri, G.; Ungerechts, H.; Wagner, S.; Zensus, J. A.; Fermi LAT Collaboration; VERITAS Collaboration; GASP-WEBT Consortium

2011-01-01

The BL Lacertae object 3C 66A was detected in a flaring state by the Fermi Large Area Telescope (LAT) and VERITAS in 2008 October. In addition to these gamma-ray observations, F-GAMMA, GASP-WEBT, PAIRITEL, MDM, ATOM, Swift, and Chandra provided radio to X-ray coverage. The available light curves show variability and, in particular, correlated flares are observed in the optical and Fermi-LAT gamma-ray band. The resulting spectral energy distribution can be well fitted using standard leptonic models with and without an external radiation field for inverse Compton scattering. It is found, however, that only the model with an external radiation field can accommodate the intra-night variability observed at optical wavelengths.

CHAIN RECONNECTIONS OBSERVED IN SYMPATHETIC ERUPTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, Navin Chandra; Magara, Tetsuya; Schmieder, Brigitte

2016-04-01

The nature of various plausible causal links between sympathetic events is still a controversial issue. In this work, we present multiwavelength observations of sympathetic eruptions, associated flares, and coronal mass ejections (CMEs) occurring on 2013 November 17 in two close active regions. Two filaments, i.e., F1 and F2, are observed in between the active regions. Successive magnetic reconnections, caused for different reasons (flux cancellation, shear, and expansion) have been identified during the whole event. The first reconnection occurred during the first eruption via flux cancellation between the sheared arcades overlying filament F2, creating a flux rope and leading to themore » first double-ribbon solar flare. During this phase, we observed the eruption of overlying arcades and coronal loops, which leads to the first CME. The second reconnection is believed to occur between the expanding flux rope of F2 and the overlying arcades of filament F1. We suggest that this reconnection destabilized the equilibrium of filament F1, which further facilitated its eruption. The third stage of reconnection occurred in the wake of the erupting filament F1 between the legs of the overlying arcades. This may create a flux rope and the second double-ribbon flare and a second CME. The fourth reconnection was between the expanding arcades of the erupting filament F1 and the nearby ambient field, which produced the bi-directional plasma flows both upward and downward. Observations and a nonlinear force-free field extrapolation confirm the possibility of reconnection and the causal link between the magnetic systems.« less

CORONAS-F observation of gamma-ray emission from the solar flare on 2003 October 29

NASA Astrophysics Data System (ADS)

Kurt, Victoria G.; Yushkov, Boris Yu.; Galkin, Vladimir I.; Kudela, Karel; Kashapova, Larisa K.

2017-10-01

Appreciable hard X-ray (HXR) and gamma-ray emissions in the 0.04-150 MeV energy range associated with the 2003 October 29 solar flare (X10/3B) were observed at 20:38-20:58 UT by the SONG instrument onboard the CORONAS-F mission. To restore flare gamma-ray spectra we fitted the SONG energy loss spectra with a three-component model of the incident spectrum: (1) a power law in energy, assumed to be due to electron bremsstrahlung; (2) a broad continuum produced by prompt nuclear de-excitation gamma-lines; and (3) a broad gamma-line generated from pion-decay. We also restored spectra from the RHESSI data, compared them with the SONG spectra and found a reasonable agreement between these spectra in the 0.1-10 MeV energy range. The pion-decay emission was observed from 20:44:20 UT and had its maximum at 20:48-20:51 UT. The power-law spectral index of accelerated protons estimated from the ratio between intensities of different components of gamma rays changed with time. The hardest spectrum with a power-law index S = -3.5 - 3.6 was observed at 20:48-20:51 UT. Time histories of the pion-decay emission and proton spectrum were compared with changes of the locations of flare energy release as shown by RHESSI hard X-ray images and remote and remote Hα brightenings. An apparent temporal correlation between processes of particle acceleration and restructuring of flare magnetic field was found. In particular, the protons were accelerated to subrelativistic energies after radical change of the character of footpoint motion from a converging motion to a separation motion.

Optical flare at RA 15:16:21.2 DEC -20:08:16

NASA Astrophysics Data System (ADS)

Nesci, Roberto; Falasca, Vincenzo; Fantaulli, Stefano

2015-06-01

On June 4 2015, while monitoring the occultation of the star HD 132885 by the asteroid 322 (Phaeo) in a session open to the public at the Foligno Observatory (IAU K56), we detected an optical flare with our Mintron intensified camera, mounted in parallel to the main telescope as electronic finder, with a 135mm F/2.5 objective.

The splitting and oscillator strengths for the 2S/2/S-2p/2/P/0/ doublet in lithium-like sulfur. [during Skylab observed solar flares

NASA Technical Reports Server (NTRS)

Pegg, D. J.; Forester, J. P.; Elston, S. B.; Griffin, P. M.; Peterson, R. S.; Thoe, R. S.; Vane, C. R.; Sellin, I. A.; Groeneveld, K.-O.

1977-01-01

The beam-foil technique has been used to study the 2S(2)S-2p(2)P(0) doublet in S XIV. The results confirm the doublet splitting measured aboard Skylab during solar flare events. In addition, the oscillator strengths for the resonance transitions comprising this doublet have been measured and found to agree well with recent relativistic f-value calculations.

Multi-wavelength observations of the flaring gamma-ray blazar 3C 66A in 2008 October

DOE PAGES

Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

2010-12-14

We report that Tthe BL Lacertae object 3C 66A was detected in a flaring state by the Fermi Large Area Telescope (LAT) and VERITAS in 2008 October. In addition to these gamma-ray observations, F-GAMMA, GASP-WEBT, PAIRITEL, MDM, ATOM, Swift, and Chandra provided radio to X-ray coverage. The available light curves show variability and, in particular, correlated flares are observed in the optical and Fermi-LAT gamma-ray band. The resulting spectral energy distribution can be well fitted using standard leptonic models with and without an external radiation field for inverse Compton scattering. It is found, however, that only the model with anmore » external radiation field can accommodate the intra-night variability observed at optical wavelengths.« less

Evidence for Magnetic Reconnection in Three Homologous Solar Flares Observed by RHESSI

NASA Technical Reports Server (NTRS)

Sui, Lin-Hui; Holman, Gordon D.; Dennis, Brian R.

2004-01-01

We present RHESSI observF5oss of three homologous flares, which occurred between April 14 and 16, 2002. We find that the RHESSI images of all three flares at energies between 6 and 25 keV had some common features: (1) A. separate coronal source up to approx. 30 deg. above the flare loop appeared in the early impulsive phase and stayed stationary for several minutes. (2) Before the flare loop moved upward; previously reported by others, the flare loop-top centroid moved downward for 2-4 minutes during the early impulsive phase of the Ears: falling by 13 - 30% of its initial height with a speed between 8 and 23 km/s. We conclude that these features are associated with the formation and development of a current sheet between the loop-top and the coronal source. In the April 14-15 flare, we find that the hard X-ray flux (greater than 25 keV) is correlated with the rate at which the flare loop moves upward, indicating that the faster the loop grows, the faster the reconnection rate, and therefore, the greater the flux of accelerated electrons. Subject headings: Sun: L'iaies-Sun: X-1-ay-s -

THE BRIGHTEST GAMMA-RAY FLARING BLAZAR IN THE SKY: AGILE AND MULTI-WAVELENGTH OBSERVATIONS OF 3C 454.3 DURING 2010 NOVEMBER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vercellone, S.; Romano, P.; Striani, E.

2011-08-01

Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during the last four years it has exhibited more than one {gamma}-ray flare per year, becoming the most active {gamma}-ray blazar in the sky. We present for the first time the multi-wavelength AGILE, Swift, INTEGRAL, and GASP-WEBT data collected in order to explain the extraordinary {gamma}-ray flare of 3C 454.3 which occurred in 2010 November. On 2010 November 20 (MJD 55520), 3C 454.3 reached a peak flux (E >100 MeV) of F{sup p}{sub {gamma}} = (6.8 {+-} 1.0) x 10{sup -5} photons cm{sup -2} s{supmore » -1} on a timescale of about 12 hr, more than a factor of six higher than the flux of the brightest steady {gamma}-ray source, the Vela pulsar, and more than a factor of three brighter than its previous super-flare on 2009 December 2-3. The multi-wavelength data make possible a thorough study of the present event: the comparison with the previous outbursts indicates a close similarity to the one that occurred in 2009. By comparing the broadband emission before, during, and after the {gamma}-ray flare, we find that the radio, optical, and X-ray emission varies within a factor of 2-3, whereas the {gamma}-ray flux by a factor of 10. This remarkable behavior is modeled by an external Compton component driven by a substantial local enhancement of soft seed photons.« less

Rotation of the optical polarization angle associated with the 2008 γ-ray flare of blazar W Comae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sorcia, Marco; Benítez, Erika; Cabrera, José I.

2014-10-10

An R-band photopolarimetric variability analysis of the TeV bright blazar W Comae between 2008 February 28 and 2013 May 17 is presented. The source showed a gradual tendency to decrease its mean flux level with a total change of 3 mJy. A maximum and minimum brightness states in the R band of 14.25 ± 0.04 and 16.52 ± 0.1 mag, respectively, were observed, corresponding to a maximum variation of ΔF = 5.40 mJy. We estimated a minimum variability timescale of Δt = 3.3 days. A maximum polarization degree P = 33.8% ± 1.6%, with a maximum variation of ΔP =more » 33.2%, was found. One of our main results is the detection of a large rotation of the polarization angle from 78° to 315° (Δθ ∼ 237°) that coincides in time with the γ-ray flare observed in 2008 June. This result indicates that both optical and γ-ray emission regions could be co-spatial. During this flare, a correlation between the R-band flux and polarization degree was found with a correlation coefficient of r {sub F} {sub –} {sub p} = 0.93 ± 0.11. From the Stokes parameters, we infer the existence of two optically thin synchrotron components that contribute to the polarized flux. One of them is stable with a constant polarization degree of 11%. Assuming a shock-in jet model during the 2008 flare, we estimated a maximum Doppler factor δ {sub D} ∼ 27 and a minimum of δ {sub D} ∼ 16; a minimum viewing angle of the jet ∼2.°0; and a magnetic field B ∼ 0.12 G.« less

X-ray variability of Pleiades late-type stars as observed with the ROSAT-PSPC

NASA Astrophysics Data System (ADS)

Marino, A.; Micela, G.; Peres, G.; Sciortino, S.

2003-08-01

We present a comprehensive analysis of X-ray variability of the late-type (dF7-dM) Pleiades stars, detected in all ROSAT-PSPC observations; X-ray variations on short (hours) and medium (months) time scales have been explored. We have grouped the stars in two samples: 89 observations of 42 distinct dF7-dK2 stars and 108 observations of 61 dK3-dM stars. The Kolmogorov-Smirnov test applied on all X-ray photon time series show that the percentage of cases of significant variability is quite similar on both samples, suggesting that the presence of variability does not depend on mass for the time scales and mass range explored. The comparison between the Time X-ray Amplitude Distribution functions (XAD) of the set of dF7-dK2 and of the dK3-dM show that, on short time scales, dK3-dM stars show larger variations than dF7-dK2. A subsample of eleven dF7-dK2 and eleven dK3-dM Pleiades stars allows the study of variability on longer time scales: we found that variability on medium - long time scales is relatively more common among dF7-dK2 stars than among dK3-dM ones. For both dF7-dK2 Pleiades stars and dF7-dK2 field stars, the variability on short time scales depends on Lx while this dependence has not been observed among dK3-dM stars. It may be that the variability among dK3-dM stars is dominated by flares that have a similar luminosity distribution for stars of different Lx, while flaring distribution in dF7-dK2 stars may depend on X-ray luminosity. The lowest mass stars show significant rapid variability (flares?) and no evidence of rotation modulation or cycles. On the contrary, dF7-dK2 Pleiades stars show both rapid variability and variations on longer time scales, likely associated with rotational modulation or cycles.

IS THE LINE-LIKE OPTICAL AFTERGLOW SED OF GRB 050709 DUE TO A FLARE?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Cong; Jin, Zhi-Ping; Wei, Da-Ming, E-mail: jin@pmo.ac.cn

Recently, Jin et al. reanalyzed the optical observation data of GRB 050709 and reported a line-like spectral energy distribution (SED) component observed by the Very Large Telescope at t  ∼ 2.5 days after the trigger of the burst, which had been interpreted as a broadened line signal arising from a macronova dominated by an iron group. In this work, we show that an optical flare origin of such a peculiar optical SED is still possible. Interestingly, even in such a model, an “unusual” origin of the late-time long-lasting Hubble Space Telescope F 814 W -band emission is still needed and a macronova/kilonovamore » is the natural interpretation.« less

An Optical and Infrared Time-domain Study of the Supergiant Fast X-Ray Transient Candidate IC 10 X-2

NASA Astrophysics Data System (ADS)

Kwan, Stephanie; Lau, Ryan M.; Jencson, Jacob; Kasliwal, Mansi M.; Boyer, Martha L.; Ofek, Eran; Masci, Frank; Laher, Russ

2018-03-01

We present an optical and infrared (IR) study of IC 10 X-2, a high-mass X-ray binary in the galaxy IC 10. Previous optical and X-ray studies suggest that X-2 is a Supergiant Fast X-ray Transient: a large-amplitude (factor of ∼100), short-duration (hours to weeks) X-ray outburst on 2010 May 21. We analyze R- and g-band light curves of X-2 from the intermediate Palomar Transient Factory taken between 2013 July 15 and 2017 February 14 that show high-amplitude (≳1 mag), short-duration (≲8 days) flares and dips (≳0.5 mag). Near-IR spectroscopy of X-2 from Palomar/TripleSpec show He I, Paschen-γ, and Paschen-β emission lines with similar shapes and amplitudes as those of luminous blue variables (LBVs) and LBV candidates (LBVc). Mid-IR colors and magnitudes from Spitzer/Infrared Array Camera photometry of X-2 resemble those of known LBV/LBVcs. We suggest that the stellar companion in X-2 is an LBV/LBVc and discuss possible origins of the optical flares. Dips in the optical light curve are indicative of eclipses from optically thick clumps formed in the winds of the stellar counterpart. Given the constraints on the flare duration (0.02–0.8 days) and the time between flares (15.1 ± 7.8 days), we estimate the clump volume filling factor in the stellar winds, f V , to be 0.01< {f}V< 0.71, which overlaps with values measured from massive star winds. In X-2, we interpret the origin of the optical flares as the accretion of clumps formed in the winds of an LBV/LBVc onto the compact object.

Results of solar observations by the CORONAS-F payload

NASA Astrophysics Data System (ADS)

Kuznetsov, V. D.; Sobelman, I. I.; Zhitnik, I. A.; Kuzin, S. V.; Kotov, Yu. D.; Charikov, Yu. E.; Kuznetsov, S. N.; Mazets, E. P.; Nusinov, A. A.; Pankov, A. M.; Sylwester, J.

2011-05-01

The CORONAS-F mission experiments and results have been reviewed. The observations with the DIFOS multi-channel photometer in a broad spectral range from 350 to 1500 nm have revealed the dependence of the relative amplitudes of p-modes of the global solar oscillations on the wavelength that agrees perfectly well with the earlier data obtained in a narrower spectral ranges. The SPIRIT EUV observations have enabled the study of various manifestations of solar activity and high-temperature events on the Sun. The data from the X-ray spectrometer RESIK, gamma spectrometer HELICON, flare spectrometer IRIS, amplitude-temporal spectrometer AVS-F, and X-ray spectrometer RPS-1 have been used to analyze the X- and gamma-ray emission from solar flares and for diagnostics of the flaring plasma. The absolute and relative content of various elements (such as potassium, argon, and sulfur) of solar plasma in flares has been determined for the first time with the X-ray spectrometer RESIK. The Solar Cosmic Ray Complex monitored the solar flare effects in the Earth's environment. The UV emission variations recorded during solar flares in the vicinity of the 120-nm wavelength have been analyzed and the amplitude of relative variations has been determined.

The X17.2 flare occurred in NOAA 10486: an example of filament destabilization caused by a domino effect

NASA Astrophysics Data System (ADS)

Zuccarello, F.; Romano, P.; Farnik, F.; Karlicky, M.; Contarino, L.; Battiato, V.; Guglielmino, S. L.; Comparato, M.; Ugarte-Urra, I.

2009-01-01

Context: It is now possible to distinguish between two main models describing the mechanisms responsible for eruptive flares : the standard model, which assumes that most of the energy is released, by magnetic reconnection, in the region hosting the core of a sheared magnetic field, and the breakout model, which assumes reconnection occurs at first in a magnetic arcade overlaying the eruptive features. Aims: We analyze the phenomena observed in NOAA 10486 before and during an X17.2 flare that occurred on 2003 October 28, to study the relationship between the pre-flare and flare phases and determine which model is the most suitable for interpreting this event. Methods: We performed an analysis of multiwavelength data set available for the event using radio data (0.8-4.5 GHz), images in the visible range (WL and Hα), EUV images (1600 and 195 Å), and X-ray data, as well as MDI longitudinal magnetograms. We determined the temporal sequence of events occurring before and during the X17.2 flare and the magnetic field configuration in the linear force-free field approximation. Results: The active region was characterized by a multiple arcade configuration and the X17.2 flare was preceded, by ~2 h, by the partial eruption of one filament. This eruption caused reconnection at null points located in the low atmosphere and a decrease in magnetic tension in the coronal field lines overlaying other filaments present in the active region. As a consequence, these filaments were destabilized and the X17.2 flare occurred. Conclusions: The phenomena observed in NOAA 10486 before and during the X17.2 flare cannot be explained by a simple scenario such as the standard or breakout model, but instead in terms of a so-called domino effect, involving a sequence of destabilizing processes that triggered the flare.

Origin of the 30 THz Emission Detected During the Solar Flare on 2012 March 13 at 17:20 UT

NASA Astrophysics Data System (ADS)

Trottet, G.; Raulin, J.-P.; Mackinnon, A.; Giménez de Castro, G.; Simões, P. J. A.; Cabezas, D.; de La Luz, V.; Luoni, M.; Kaufmann, P.

2015-10-01

Solar observations in the infrared domain can bring important clues on the response of the low solar atmosphere to primary energy released during flares. At present, the infrared continuum has been detected at 30 THz (10 μm) in only a few flares. SOL2012-03-13, which is one of these flares, has been presented and discussed in Kaufmann et al. ( Astrophys. J. 768, 134, 2013). No firm conclusions were drawn on the origin of the mid-infrared radiation. In this work we present a detailed multi-frequency analysis of the SOL2012-03-13 event, including observations at radio-millimeter and submillimeter wavelengths, in hard X-rays (HXR), gamma-rays (GR), Hα, and white light. The HXR/GR spectral analysis shows that SOL2012-03-13 is a GR line flare and allows estimating the numbers of and energy contents in electrons, protons, and α particles produced during the flare. The energy spectrum of the electrons producing the HXR/GR continuum is consistent with a broken power-law with an energy break at {˜} 800 keV. We show that the high-energy part (above {˜} 800 keV) of this distribution is responsible for the high-frequency radio emission ({>} 20 GHz) detected during the flare. By comparing the 30 THz emission expected from semi-empirical and time-independent models of the quiet and flare atmospheres, we find that most ({˜} 80 %) of the observed 30 THz radiation can be attributed to thermal free-free emission of an optically thin source. Using the F2 flare atmospheric model (Machado et al. in Astrophys. J. 242, 336, 1980), this thin source is found to be at temperatures T {˜} 8000 K and is located well above the minimum temperature region. We argue that the chromospheric heating, which results in 80 % of the 30 THz excess radiation, can be due to energy deposition by nonthermal flare-accelerated electrons, protons, and α particles. The remaining 20 % of the 30 THz excess emission is found to be radiated from an optically thick atmospheric layer at T {˜} 5000 K, below the temperature minimum region, where direct heating by nonthermal particles is insufficient to account for the observed infrared radiation.

2D MHD AND 1D HD MODELS OF A SOLAR FLARE—A COMPREHENSIVE COMPARISON OF THE RESULTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falewicz, R.; Rudawy, P.; Murawski, K.

Without any doubt, solar flaring loops possess a multithread internal structure that is poorly resolved, and there are no means to observe heating episodes and thermodynamic evolution of the individual threads. These limitations cause fundamental problems in numerical modeling of flaring loops, such as selection of a structure and a number of threads, and an implementation of a proper model of the energy deposition process. A set of one-dimensional (1D) hydrodynamic and two-dimensional (2D) magnetohydrodynamic models of a flaring loop are developed to compare energy redistribution and plasma dynamics in the course of a prototypical solar flare. Basic parameters ofmore » the modeled loop are set according to the progenitor M1.8 flare recorded in AR 10126 on 2002 September 20 between 09:21 UT and 09:50 UT. The nonideal 1D models include thermal conduction and radiative losses of the optically thin plasma as energy-loss mechanisms, while the nonideal 2D models take into account viscosity and thermal conduction as energy-loss mechanisms only. The 2D models have a continuous distribution of the parameters of the plasma across the loop and are powered by varying in time and space along and across the loop heating flux. We show that such 2D models are an extreme borderline case of a multithread internal structure of the flaring loop, with a filling factor equal to 1. Nevertheless, these simple models ensure the general correctness of the obtained results and can be adopted as a correct approximation of the real flaring structures.« less

The Study of the Cosmic Gamma-Emission Nonstationary Fluxes Characteristics by the AVS-F Apparatus Data

NASA Astrophysics Data System (ADS)

Kotov, Yu. D.; Arkhangelskaja, I. V.; Arkhangelsky, A. I.; Kuznetsov, S. N.; Glyanenko, A. S.; Kalmykov, P. A.; Amandzholova, D. B.; Samoylenko, V. T.; Yurov, V. N.; Pavlov, A. V.; Chervyakova, O. I.; Afonina, I. V.

The AVS-F apparatus (Russian abbreviation for Amplitude-Time Spectrometry of the Sun) is intended for the solar flares' hard X-ray and gamma-ray emission characteristic studies and for the search and detection of the gamma-ray bursts (GRB). At present over 1,100 events with duration more than 2 s without any coordinate relations to Earth Radiation Belts and South Atlantic Anomaly were separated on the results of preliminary analysis of AVS-F experiment database.About 68 % of the identified events were associated with quasistationary equatorial precipitations-15-30 % count rate increases in the low-energy gamma-band of the AVS-F apparatus over its average value obtained by approximation of these parts with polynomials discovered on some equatorial segments in the ranges of geographic latitude of 25∘ up to +30∘. Several short events with duration of 1-16 ms associated with terrestrial gamma-ray flashes were registered during the experiment. These events were detected above the powerful thunderstorm formations.Solar flares with classes stronger than M1.0 according to the GOES classification were about 7 % of the detected events. Solar flares' hard X-rays and γ-emission were mainly observed during the rise or maximum phases of the emission in the soft X-rays band according to the detectors on board the GOES series satellites data and duration of their registration is less than of the soft X-ray bands. According to the preliminary data analysis gamma-emission with energy over 10 MeV was registered during 12 % of the observed flares. The emission in the energy band E ¿ 100 keV was registered during over 60 faint solar flares (of B and C classes according to the GOES and from several ones γ-quanta with energy up to several tens of MeV were observed.Several spectral line complexes were observed in the spectra of some solar flares stronger than M1.0 in the low-energy gamma-range. Registered spectral features were corresponded to α α-lines, annihilation line, nuclear lines, and neutron capture line on1H (2.223 MeV). In the spectrum of the January 20, 2005 solar flare the feature in the range of 15-21 MeV was detected for the first time. It can be associated with lines of 15.11 MeV (12C +16O) or 20.58 MeV (from neutron radiative capture on3He), or with their combination. Also several e-dominant flares without any gamma-lines in energy spectra were identified. All detected faint solar flares were e-dominant according to the preliminary data analysis.Thin structure with characteristic timescale of 30-160 s was observed at 99 % significance level on some solar flares stronger than M1.0 temporal profiles in the low-energy gamma-band in the energy ranges corresponding to the identified spectral features or whole gamma-band energy boundaries. According to the results of the preliminary analysis during the flare of January 20, 2005, thin structure with timescale from 7 ms to 35 ms was detected at 99 % confidence level in the energy range of 0.1-20 MeV. Some thin structure with characteristic timescale 50-110 s was observed on temporal profiles of several faint events.About 3 % of the identified events were gamma-ray bursts. During some bursts high-energy gamma-emission was observed, for example Emax = 147 ± 3 MeV for GRB050525.

Measurements and Modeling of Total Solar Irradiance in X-class Solar Flares

NASA Technical Reports Server (NTRS)

Moore, Christopher S.; Chamberlin, Phillip Clyde; Hock, Rachel

2014-01-01

The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment can detect changes in the total solar irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-class solar flares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar flares presented in Woods et al., as well as an additional flare measured on 2006 December 6. The radiative outputs for both phases of these five flares are then compared to the vacuum ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-class flares. This model provides the basis for the bolometric energy estimates for the solar flares analyzed in the Emslie et al. study.

Which of Kepler's Stars Flare?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-12-01

The habitability of distant exoplanets is dependent upon many factors one of which is the activity of their host stars. To learn about which stars are most likely to flare, a recent study examines tens of thousands of stellar flares observed by Kepler.Need for a Broader SampleArtists rendering of a flaring dwarf star. [NASAs Goddard Space Flight Center/S. Wiessinger]Most of our understanding of what causes a star to flare is based on observations of the only star near enough to examine in detail the Sun. But in learning from a sample size of one, a challenge arises: we must determine which conclusions are unique to the Sun (or Sun-like stars), and which apply to other stellar types as well.Based on observations and modeling, astronomers think that stellar flares result from the reconnection of magnetic field lines in a stars outer atmosphere, the corona. The magnetic activity is thought to be driven by a dynamo caused by motions in the stars convective zone.HR diagram of the Kepler stars, with flaring main-sequence (yellow), giant (red) and A-star (green) stars in the authors sample indicated. [Van Doorsselaere et al. 2017]To test whether these ideas are true generally, we need to understand what types of stars exhibit flares, and what stellar properties correlate with flaring activity. A team of scientists led by Tom Van Doorsselaere (KU Leuven, Belgium) has now used an enormous sample of flares observed by Kepler to explore these statistics.Intriguing TrendsVan Doorsselaere and collaborators used a new automated flare detection and characterization algorithm to search through the raw light curves from Quarter 15 of the Kepler mission, building a sample of 16,850 flares on 6,662 stars. They then used these to study the dependence of the flare occurrence rate, duration, energy, and amplitude on the stellar spectral type and rotation period.This large statistical study led the authors to several interesting conclusions, including:Flare star incidence rate as a a function of Rossby number, which traces stellar rotation. Higher rotation rates correspond to lower Rossby numbers, so these data indicate that more rapidly rotating stars are more likely to exhibit flares. [Van Doorsselaere et al. 2017]Roughly 3.5% of Kepler stars in this sample are flaring stars.24 new A stars are found to show flaring activity. This is interesting because A stars arent thought to have an outer convective zone, which should prevent a magnetic dynamo from operating. Yet these flaring-star detections add to the body of evidence that at least some A stars do show magnetic activity.Most flaring stars in the sample are main-sequence stars, but 653 giants were found to have flaring activity. As with A stars, its unexpected that giant stars would have strong magnetic fields their increase in size and gradual spin-down over time should result in weakening of the surface fields. Nevertheless, it seems that the flare incidence of giant stars is similar to that of F or G main-sequence stars.All stellar types appear to have a small fraction of flare stars stars with an especially high rate of flare occurrence.Rapidly rotating stars are more likely to flare, tend to flare more often, and tend to have stronger flares than slowly rotating stars.As a next step, the authors plan to apply their flare detection algorithm to the larger sample of all Kepler data. In the meantime, this study has both deepened a few mysteries and moved us a step closer in our understanding of which stars flare and why.CitationTom Van Doorsselaere et al 2017 ApJS 232 26. doi:10.3847/1538-4365/aa8f9a

Energetic-particle abundances in impulsive solar flares

NASA Technical Reports Server (NTRS)

Reames, D. V.; Cane, H. V.; Von Rosenvinge, T. T.

1990-01-01

The abundances of elements and of He-3 in 90 solar electron events have been examined. It is found that the events fall into two distinct groups based upon their F/C ratio. Events in the F-rich group frequently have high He-3/He-4 ratios and are associated with type III and type V radio bursts in the parent flare. The F-poor events are associated with type IV bursts. These results on individual events support the conclusions of earlier work done with daily-averaged abundances.

F-22 Plus-Up Environmental Assessment Joint Base Elmendorf-Richardson, Alaska

DTIC Science & Technology

2011-06-01

Page 1-3 The F-22 has enhanced low visibilty, speed, maneuverability, electronics , and maintainability. The proposal is to beddown six primary...tactics, radar employment, identification, weapons employment, defensive response, electronic countermeasures, and electronic counter countermeasures...flare, and electronic countermeasures. Warning Area, MOA, and ATCAA 2,000 AGL to 60,000 MSL 0.75 to 1.5 hour F-22 Plus-Up Environmental

Deep Flare Net (DeFN) Model for Solar Flare Prediction

NASA Astrophysics Data System (ADS)

Nishizuka, N.; Sugiura, K.; Kubo, Y.; Den, M.; Ishii, M.

2018-05-01

We developed a solar flare prediction model using a deep neural network (DNN) named Deep Flare Net (DeFN). This model can calculate the probability of flares occurring in the following 24 hr in each active region, which is used to determine the most likely maximum classes of flares via a binary classification (e.g., ≥M class versus

The Origin of the EUV Late Phase: A Case Study of the C8.8 Flare on 2010 May 5

NASA Technical Reports Server (NTRS)

Hock, R. A.; Woods, T. N.; Klimchuk, J. A.; Eparvier, F. G.; Jones, A. R.

2012-01-01

Since the launch of NASA's Solar Dynamics Observatory on 2010 February 11, the Extreme ultraviolet Variability Experiment (EVE) has observed numerous flares. One interesting feature observed by EVE is that a subset of flares exhibit an additional enhancement of the 2-3 million K emission several hours after the flares soft X-ray emission. From the Atmospheric Imaging Assembly (AIA) images, we observe that this secondary emission, dubbed the EUV late phase, occurs in the same active region as the flare but not in the same coronal loops. Here, we examine the C8.8 flare that occurred on 2010 May 5 as a case study of EUV late phase flares. In addition to presenting detailed observations from both AIA and EVE, we develop a physical model of this flare and test it using the Enthalpy Based Thermal Evolution of Loops (EBTEL) model.

Plasma heating in solar flares and their soft and hard X-ray emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falewicz, R., E-mail: falewicz@astro.uni.wroc.pl

In this paper, the energy budgets of two single-loop-like flares observed in X-ray are analyzed under the assumption that nonthermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 February 20 and June 2, respectively. Using a one-dimensional (1D) hydrodynamic code for both flares, the energy deposited in the chromosphere was derived applying RHESSI observational data. The use of the Fokker-Planck formalism permits the calculation of distributions of the NTEs in flaring loops and thus spatial distributions of the X-ray nonthermal emissions and integralmore » fluxes for the selected energy ranges that were compared with the observed ones. Additionally, a comparative analysis of the spatial distributions of the signals in the RHESSI images was conducted for the footpoints and for all the flare loops in selected energy ranges with these quantities' fluxes obtained from the models. The best compatibility of the model and observations was obtained for the 2002 June 2 event in the 0.5-4 Å GOES range and total fluxes in the 6-12 keV, 12-25 keV, 20-25 keV, and 50-100 keV energy bands. Results of photometry of the individual flaring structures in a high energy range show that the best compliance occurred for the 2002 June 2 flare, where the synthesized emissions were at least 30% higher than the observed emissions. For the 2002 February 20 flare, synthesized emission is about four times lower than the observed one. However, in the low energy range the best conformity was obtained for the 2002 February 20 flare, where emission from the model is about 11% lower than the observed one. The larger inconsistency occurs for the 2002 June 2 solar flare, where synthesized emission is about 12 times greater or even more than the observed emission. Some part of these differences may be caused by inevitable flaws of the applied methodology, like by an assumption that the model of the flare is symmetric and there are no differences in the emissions originating from the feet of the flares loop and by relative simplicity of the applied numerical 1D code and procedures. No doubt a significant refinement of the applied numerical models and more sophisticated implementation of the various physical mechanisms involved are required to achieve a better agreement. Despite these problems, a collation of modeled results with observations shows that soft and hard X-ray emissions observed for analyzed single-loop-like events may be fully explained by electron-beam-driven evaporation only.« less

Plasma Heating in Solar Flares and their Soft and Hard X-Ray Emissions

NASA Astrophysics Data System (ADS)

Falewicz, R.

2014-07-01

In this paper, the energy budgets of two single-loop-like flares observed in X-ray are analyzed under the assumption that nonthermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 February 20 and June 2, respectively. Using a one-dimensional (1D) hydrodynamic code for both flares, the energy deposited in the chromosphere was derived applying RHESSI observational data. The use of the Fokker-Planck formalism permits the calculation of distributions of the NTEs in flaring loops and thus spatial distributions of the X-ray nonthermal emissions and integral fluxes for the selected energy ranges that were compared with the observed ones. Additionally, a comparative analysis of the spatial distributions of the signals in the RHESSI images was conducted for the footpoints and for all the flare loops in selected energy ranges with these quantities' fluxes obtained from the models. The best compatibility of the model and observations was obtained for the 2002 June 2 event in the 0.5-4 Å GOES range and total fluxes in the 6-12 keV, 12-25 keV, 20-25 keV, and 50-100 keV energy bands. Results of photometry of the individual flaring structures in a high energy range show that the best compliance occurred for the 2002 June 2 flare, where the synthesized emissions were at least 30% higher than the observed emissions. For the 2002 February 20 flare, synthesized emission is about four times lower than the observed one. However, in the low energy range the best conformity was obtained for the 2002 February 20 flare, where emission from the model is about 11% lower than the observed one. The larger inconsistency occurs for the 2002 June 2 solar flare, where synthesized emission is about 12 times greater or even more than the observed emission. Some part of these differences may be caused by inevitable flaws of the applied methodology, like by an assumption that the model of the flare is symmetric and there are no differences in the emissions originating from the feet of the flares loop and by relative simplicity of the applied numerical 1D code and procedures. No doubt a significant refinement of the applied numerical models and more sophisticated implementation of the various physical mechanisms involved are required to achieve a better agreement. Despite these problems, a collation of modeled results with observations shows that soft and hard X-ray emissions observed for analyzed single-loop-like events may be fully explained by electron-beam-driven evaporation only.

Time-Resolved Ultraviolet Spectroscopy of the M-Dwarf GJ 876 Exoplanetary System

NASA Technical Reports Server (NTRS)

France, Kevin; Linsky, Jeffrey L.; Tian, Feng; Froning, Cynthia S.; Roberge, Aki

2012-01-01

Extrasolar planets orbiting M-stars may represent our best chance to discover habitable worlds in the coming decade. The ultraviolet spectrum incident upon both Earth-like and Jovian planets is critically important for proper modeling of their atmospheric heating and chemistry. In order to provide more realistic inputs for atmospheric models of planets orbiting low-mass stars, we present new near- and far-ultraviolet (NUV and FUV) spectroscopy of the M-dwarf exoplanet host GJ 876 (U4V). Using the COS and STIS spectrographs aboard the Hubble Space Telescope, we have measured the 1150 - 3140 Ang. spectrum of GJ 876. We have reconstructed the stellar H I Ly-alpha emission line profile, and find that the integrated Ly-apha flux is roughly equal to the rest of the integrated flux (1150 - 1210 Ang + 1220 - 3140 Ang) in the entire ultraviolet bandpass (F(Ly-alpha)/F(FUV+NUV) approximately equals 0.7). This ratio is approximately 2500 x greater than the solar value. We describe the ultraviolet line spectrum and report surprisingly strong fluorescent emission from hot H2 (T(H2) > 2000 K). We show the light-curve of a chromospheric + transition region flare observed in several far-UV emission lines, with flare/ quiescent flux ratios :2: 10. The strong FUV radiation field of an M-star (and specifically Ly-alpha) is important for determining the abundance of O2 - and the formation of biomarkers - in the lower atmospheres of Earth-like planets in the habitable zones of low-mass stars.

Rapid variability of blazar 3C 279 during flaring states in 2013-2014 with joint FERMI-LAT, NuSTAR, SWIFT, and ground-based multi-wavelength observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayashida, M.; Nalewajko, K.; Madejski, G. M.

2015-07-02

Here we report the results of a multiband observing campaign on the famous blazar 3C 279 conducted during a phase of increased activity from 2013 December to 2014 April, including first observations of it with NuSTAR. The γ-ray emission of the source measured by Fermi-LAT showed multiple distinct flares reaching the highest flux level measured in this object since the beginning of the Fermi mission, with F(E>100 MeV) of 10 -5 photons cm -2 s -1, and with a flux-doubling time scale as short as 2 hr. The γ-ray spectrum during one of the flares was very hard, with an index of Γ γ =1.7±0.1, which is rarely seen in flat-spectrum radio quasars. The lack of concurrent optical variability implies a very high Compton dominance parameter L γ/L syn > 300. Two 1 day NuSTAR observations with accompanying Swift pointings were separated by 2 weeks, probing different levels of source activity. While the 0.5-70 keV X-ray spectrum obtained during the first pointing, and fitted jointly with Swift-XRT is well-described by a simple power law, the second joint observation showed an unusual spectral structure: the spectrum softens by ΔΓ xmore » $$\\simeq$$ 0.4 at ~ keV. Modeling the broadband spectral energy distribution during this flare with the standard synchrotron plus inverse-Compton model requires: (1) the location of the γ-ray emitting region is comparable with the broad-line region radius, (2) a very hard electron energy distribution index p $$\\simeq$$ 1, (3) total jet power significantly exceeding the accretion-disk luminosity L j/L d ≳ 10, and (4) extremely low jet magnetization with L B/L j ≲ 10 -4. In conclusion, we also find that single-zone models that match the observed γ-ray and optical spectra cannot satisfactorily explain the production of X-ray emission.« less

Response of the solar atmosphere to a simple flare burst: UV emission from the flare transition layer.

NASA Astrophysics Data System (ADS)

Shmeleva, O. P.

The flare transition layer exists as a relatively steady formation even during impulsive heating. It is maintained by a heat flow from the high-temperature plasma, where the major part of the electron beam energy is absorbed. The lifetime of this plasma is much greater than the impulsive heating time. Intensities of resonance UV lines are calculated using both the model of impulsive nonthermal heating by energetic electrons and the model of continuous thermal heating. The calculated line intensity is almost constant during a long time. The line Doppler shifts predicted by the former model match observations. This suggests that the model represents sufficiently well the actual dynamics of the flare plasma. The flare transition layer is a thin formation, its thickness being Δξ = 1021m-2. It is therefore described adequately within the p = const approximation though the picture of hydrodynamic response of the solar atmosphere to the impulsive heating by energy flows is rather complicated and nonsteady, of course. The intensities of the C IV λλ154.8, 155.1 nm and O VI λλ103.2, 103.8 nm lines are calculated within the scope of the model of continuous thermal heating, in which the conductive heating of the flare transition layer is balanced by radiative cooling. The line intensities are proportional to the pressure in the layer, which permits the pressure to be found from the observed line intensities. The analysis reveals that both heating models adequately represent the actual structure and dynamics of plasma in a flare. In the flare transition layer, the classical heat conduction always does work.

Solar flare induced cosmic noise absorption

NASA Astrophysics Data System (ADS)

Ogunmodimu, Olugbenga; Honary, Farideh; Rogers, Neil; Falayi, E. O.; Bolaji, O. S.

2018-06-01

Solar flare events are a major observing emphasis for space weather because they affect the ionosphere and can eject high-energy particles that can adversely affect Earth's technologies. In this study we model 38.2 MHz cosmic noise absorption (CNA) by utilising measurements from the Imaging Riometer for Ionospheric Studies (IRIS) at Kilpisjärvi, Finland obtained during solar cycle 23 (1996-2009). We utilised X-ray archive for the same period from the Geostationary Operational Environmental Satellite (GOES) to study solar flare induced cosmic noise absorption. We identified the threshold of flare (M4 class) that could bear significant influence on CNA. Through epoch analysis, we show the magnitude of absorption that each class of flare could produce. Using the parameters of flare and absorption we present a model that could provide the basis for nowcast of CNA induced by M and X-class solar flares.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osten, Rachel A.; Kowalski, Adam; Drake, Stephen A.

On 2014 April 23, the Swift satellite responded to a hard X-ray transient detected by its Burst Alert Telescope, which turned out to be a stellar flare from a nearby, young M dwarf binary DG CVn. We utilize observations at X-ray, UV, optical, and radio wavelengths to infer the properties of two large flares. The X-ray spectrum of the primary outburst can be described over the 0.3–100 keV bandpass by either a single very high-temperature plasma or a nonthermal thick-target bremsstrahlung model, and we rule out the nonthermal model based on energetic grounds. The temperatures were the highest seen spectroscopically inmore » a stellar flare, at T{sub X} of 290 MK. The first event was followed by a comparably energetic event almost a day later. We constrain the photospheric area involved in each of the two flares to be >10{sup 20} cm{sup 2}, and find evidence from flux ratios in the second event of contributions to the white light flare emission in addition to the usual hot, T  ∼ 10{sup 4} K blackbody emission seen in the impulsive phase of flares. The radiated energy in X-rays and white light reveal these events to be the two most energetic X-ray flares observed from an M dwarf, with X-ray radiated energies in the 0.3–10 keV bandpass of 4 × 10{sup 35} and 9 × 10{sup 35} erg, and optical flare energies at E{sub V} of 2.8 × 10{sup 34} and 5.2 × 10{sup 34} erg, respectively. The results presented here should be integrated into updated modeling of the astrophysical impact of large stellar flares on close-in exoplanetary atmospheres.« less

Reduced combustion mechanism for C1-C4 hydrocarbons and its application in computational fluid dynamics flare modeling.

PubMed

Damodara, Vijaya; Chen, Daniel H; Lou, Helen H; Rasel, Kader M A; Richmond, Peyton; Wang, Anan; Li, Xianchang

2017-05-01

Emissions from flares constitute unburned hydrocarbons, carbon monoxide (CO), soot, and other partially burned and altered hydrocarbons along with carbon dioxide (CO 2 ) and water. Soot or visible smoke is of particular concern for flare operators/regulatory agencies. The goal of the study is to develop a computational fluid dynamics (CFD) model capable of predicting flare combustion efficiency (CE) and soot emission. Since detailed combustion mechanisms are too complicated for (CFD) application, a 50-species reduced mechanism, LU 3.0.1, was developed. LU 3.0.1 is capable of handling C 4 hydrocarbons and soot precursor species (C 2 H 2 , C 2 H 4 , C 6 H 6 ). The new reduced mechanism LU 3.0.1 was first validated against experimental performance indicators: laminar flame speed, adiabatic flame temperature, and ignition delay. Further, CFD simulations using LU 3.0.1 were run to predict soot emission and CE of air-assisted flare tests conducted in 2010 in Tulsa, Oklahoma, using ANSYS Fluent software. Results of non-premixed probability density function (PDF) model and eddy dissipation concept (EDC) model are discussed. It is also noteworthy that when used in conjunction with the EDC turbulence-chemistry model, LU 3.0.1 can reasonably predict volatile organic compound (VOC) emissions as well. A reduced combustion mechanism containing 50 C 1 -C 4 species and soot precursors has been developed and validated against experimental data. The combustion mechanism is then employed in the computational fluid dynamics (CFD) of modeling of soot emission and combustion efficiency (CE) of controlled flares for which experimental soot and CE data are available. The validated CFD modeling tools are useful for oil, gas, and chemical industries to comply with U.S. Environmental Protection Agency's (EPA) mandate to achieve smokeless flaring with a high CE.

Evaluation of Applicability of a Flare Trigger Model Based on a Comparison of Geometric Structures

NASA Astrophysics Data System (ADS)

Bamba, Yumi; Kusano, Kanya

2018-03-01

The triggering mechanism(s) and critical condition(s) of solar flares are still not completely clarified, although various studies have attempted to elucidate them. We have also proposed a theoretical flare-trigger model based on MHD simulations in which two types of small-scale bipole fields, the so-called opposite polarity (OP) and reversed shear (RS), can trigger flares. In this study, we evaluated the applicability of our flare-trigger model to the observation of 32 flares that were observed by the Solar Dynamics Observatory, by focusing on geometrical structures. We classified the events into six types, including the OP and RS types, based on photospheric magnetic field configuration, presence of precursor brightenings, and shape of the initial flare ribbons. As a result, we found that approximately 30% of the flares were consistent with our flare-trigger model, and the number of RS-type triggered flares is larger than that of the OP type. We found that none of the sampled events contradict our flare model; though, we cannot clearly determine the trigger mechanism of 70% of the flares in this study. We carefully investigated the applicability of our flare-trigger model and the possibility that other models can explain the other 70% of the events. Consequently, we concluded that our flare-trigger model has certainly proposed important conditions for flare-triggering.

Deep Learning Based Solar Flare Forecasting Model. I. Results for Line-of-sight Magnetograms

NASA Astrophysics Data System (ADS)

Huang, Xin; Wang, Huaning; Xu, Long; Liu, Jinfu; Li, Rong; Dai, Xinghua

2018-03-01

Solar flares originate from the release of the energy stored in the magnetic field of solar active regions, the triggering mechanism for these flares, however, remains unknown. For this reason, the conventional solar flare forecast is essentially based on the statistic relationship between solar flares and measures extracted from observational data. In the current work, the deep learning method is applied to set up the solar flare forecasting model, in which forecasting patterns can be learned from line-of-sight magnetograms of solar active regions. In order to obtain a large amount of observational data to train the forecasting model and test its performance, a data set is created from line-of-sight magnetogarms of active regions observed by SOHO/MDI and SDO/HMI from 1996 April to 2015 October and corresponding soft X-ray solar flares observed by GOES. The testing results of the forecasting model indicate that (1) the forecasting patterns can be automatically reached with the MDI data and they can also be applied to the HMI data; furthermore, these forecasting patterns are robust to the noise in the observational data; (2) the performance of the deep learning forecasting model is not sensitive to the given forecasting periods (6, 12, 24, or 48 hr); (3) the performance of the proposed forecasting model is comparable to that of the state-of-the-art flare forecasting models, even if the duration of the total magnetograms continuously spans 19.5 years. Case analyses demonstrate that the deep learning based solar flare forecasting model pays attention to areas with the magnetic polarity-inversion line or the strong magnetic field in magnetograms of active regions.

The Effect of Magnetic Topology on the Escape of Flare Particles

NASA Technical Reports Server (NTRS)

Antiochos, S. K.; Masson, S.; DeVore, C. R.

2012-01-01

Magnetic reconnection in the solar atmosphere is believed to be the driver of most solar explosive phenomena. Therefore, the topology of the coronal magnetic field is central to understanding the solar drivers of space weather. Of particular importance to space weather are the impulsive Solar Energetic particles that are associated with some CME/eruptive flare events. Observationally, the magnetic configuration of active regions where solar eruptions originate appears to agree with the standard eruptive flare model. According to this model, particles accelerated at the flare reconnection site should remain trapped in the corona and the ejected plasmoid. However, flare-accelerated particles frequently reach the Earth long before the CME does. We present a model that may account for the injection of energetic particles onto open magnetic flux tubes connecting to the Earth. Our model is based on the well-known 2.5D breakout topology, which has a coronal null point (null line) and a four-flux system. A key new addition, however, is that we include an isothermal solar wind with open-flux regions. Depending on the location of the open flux with respect to the null point, we find that the flare reconnection can consist of two distinct phases. At first, the flare reconnection involves only closed field, but if the eruption occurs close to the open field, we find a second phase involving interchange reconnection between open and closed. We argue that this second reconnection episode is responsible for the injection of flare-accelerated particles into the interplanetary medium. We will report on our recent work toward understanding how flare particles escape to the heliosphere. This work uses high-resolution 2.5D MHD numerical simulations performed with the Adaptively Refined MHD Solver (ARMS).

Modelling a man-portable air-defence (MANPAD) system with a conical scan two-colour infrared (IR) seeker

NASA Astrophysics Data System (ADS)

Jackman, James; Richardson, Mark; Butters, Brian; Walmsley, Roy

2011-11-01

The use of flares of flares against 1st and 2nd generation man-portable air-defence (MANPAD) systems proved to be very effective. This naturally led to the development of counter-countermeasures (CCM) that could be incorporated into the MANPADs infrared (IR) seeker. One possible CCM is two-colour where the seeker detects in two separate IR bands. It is designed to exploit the different spectral characteristics of the target and flare. In this paper we describe the modelling process of a two-colour conical scan (conscan) IR seeker using CounterSim, a missile engagement and countermeasure simulation software tool developed by Chemring Countermeasures Ltd. It starts by explaining the signal processing needed to be able to reject the flare and track the target. The MANPAD model is then used in an engagement with a fast jet model and a transport aircraft model. Flares are first deployed reactively then released throughout an engagement to investigate the effect of flare release time and the viability of pre-emptive countermeasures.

ASASSN-18di: Discovery of a Powerful Flare on a Mid-M Dwarf

NASA Astrophysics Data System (ADS)

Rodríguez, R.; Schmidt, S. J.; Jayasinghe, T.; Stanek, K. Z.; Prieto, J. L.; Shappee, B.; Kochanek, C. S.; Thompson, Todd A.; Shields, J.; Holoien, T. W.-S.; Bersier, D.; Brimacombe, J.

2018-04-01

We report and characterize a white-light superflare on a previously undiscovered M dwarf detected by the ASAS-SN survey. Employing various color-magnitude and color-spectral type relationships, we estimate several stellar parameters, including the quiescent V-band magnitude, from which we derive a flare amplitude of $\\Delta V \\sim 10$. We determine an r-band absolute magnitude of $M_{r} = 11.4$, consistent with a mid-M dwarf, and an approximate distance to the source of $2.2$ kpc. Using classical-flare models, we infer a flare energy of $E_{V} \\simeq (4.1\\pm 2.2)\\times 10^{36}$ ergs, making this one of the strongest flares documented on an M dwarf.

40 CFR 265.1033 - Standards: Closed-vent systems and control devices.

Code of Federal Regulations, 2014 CFR

2014-07-01

... established as a requirement of § 265.1035(b)(4)(iii)(F). (h) An owner or operator using a carbon adsorption..., as determined by the methods specified in paragraph (f)(2)(iii) of this section. (3) A flare shall be... (60 ft/s), except as provided in paragraphs (d)(4) (ii) and (iii) of this section. (ii) A steam...

40 CFR 265.1033 - Standards: Closed-vent systems and control devices.

Code of Federal Regulations, 2013 CFR

2013-07-01

... established as a requirement of § 265.1035(b)(4)(iii)(F). (h) An owner or operator using a carbon adsorption..., as determined by the methods specified in paragraph (f)(2)(iii) of this section. (3) A flare shall be... (60 ft/s), except as provided in paragraphs (d)(4) (ii) and (iii) of this section. (ii) A steam...

40 CFR 265.1033 - Standards: Closed-vent systems and control devices.

Code of Federal Regulations, 2012 CFR

2012-07-01

... established as a requirement of § 265.1035(b)(4)(iii)(F). (h) An owner or operator using a carbon adsorption..., as determined by the methods specified in paragraph (f)(2)(iii) of this section. (3) A flare shall be... (60 ft/s), except as provided in paragraphs (d)(4) (ii) and (iii) of this section. (ii) A steam...

Evolution of flare ribbons, electric currents, and quasi-separatrix layers during an X-class flare

NASA Astrophysics Data System (ADS)

Janvier, M.; Savcheva, A.; Pariat, E.; Tassev, S.; Millholland, S.; Bommier, V.; McCauley, P.; McKillop, S.; Dougan, F.

2016-07-01

Context. The standard model for eruptive flares has been extended to three dimensions (3D) in the past few years. This model predicts typical J-shaped photospheric footprints of the coronal current layer, forming at similar locations as the quasi-separatrix layers (QSLs). Such a morphology is also found for flare ribbons observed in the extreme ultraviolet (EUV) band, and in nonlinear force-free field (NLFFF) magnetic field extrapolations and models. Aims: We study the evolution of the photospheric traces of the current density and flare ribbons, both obtained with the Solar Dynamics Observatory instruments. We aim to compare their morphology and their time evolution, before and during the flare, with the topological features found in a NLFFF model. Methods: We investigated the photospheric current evolution during the 06 September 2011 X-class flare (SOL2011-09-06T22:20) occurring in NOAA AR 11283 from observational data of the magnetic field obtained with the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory. We compared this evolution with that of the flare ribbons observed in the EUV filters of the Atmospheric Imager Assembly. We also compared the observed electric current density and the flare ribbon morphology with that of the QSLs computed from the flux rope insertion method-NLFFF model. Results: The NLFFF model shows the presence of a fan-spine configuration of overlying field lines, due to the presence of a parasitic polarity, embedding an elongated flux rope that appears in the observations as two parts of a filament. The QSL signatures of the fan configuration appear as a circular flare ribbon that encircles the J-shaped ribbons related to the filament ejection. The QSLs, evolved via a magnetofrictional method, also show similar morphology and evolution as both the current ribbons and the EUV flare ribbons obtained several times during the flare. Conclusions: For the first time, we propose a combined analysis of the photospheric traces of an eruptive flare, in a complex topology, with direct measurements of electric currents and QSLs from observational data and a magnetic field model. The results, obtained by two different and independent approaches 1) confirm previous results of current increase during the impulsive phase of the flare and 2) show how NLFFF models can capture the essential physical signatures of flares even in a complex magnetic field topology. A movie associated to Fig. 1 is available in electronic form at http://www.aanda.org

Multiband Observations of the Quasar PKS 2326–502 during Active and Quiescent Gamma-Ray States in 2010–2012

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutka, Michael S.; Carpenter, Bryce D.; Gehrels, Neil

2017-02-01

Quasi-simultaneous observations of the Flat Spectrum Radio Quasar PKS 2326−502 were carried out in the γ -ray, X-ray, UV, optical, near-infrared, and radio bands. Using these observations, we are able to characterize the spectral energy distribution (SED) of the source during two flaring and one quiescent γ -ray states. These data were used to constrain one-zone leptonic models of the SEDs of each flare and investigate the physical conditions giving rise to them. While modeling one flare required only changes in the electron spectrum compared to the quiescent state, modeling the other flare required changes in both the electron spectrummore » and the size of the emitting region. These results are consistent with an emerging pattern of two broad classes of flaring states seen in blazars. Type 1 flares are explained by changes solely in the electron distribution, whereas type 2 flares require a change in an additional parameter. This suggests that different flares, even in the same source, may result from different physical conditions or different regions in the jet.« less

Multiband Observations of the Quasar PKS 2326–502 during Active and Quiescent Gamma-Ray States in 2010–2012

DOE PAGES

Dutka, Michael S.; Carpenter, Bryce D.; Ojha, Roopesh; ...

2017-01-30

We present that quasi-simultaneous observations of the Flat Spectrum Radio Quasar PKS 2326-502 were carried out in the γ-ray, X-ray, UV, optical, near-infrared, and radio bands. Using these observations, we are able to characterize the spectral energy distribution (SED) of the source during two flaring and one quiescent γ-ray states. These data were used to constrain one-zone leptonic models of the SEDs of each flare and investigate the physical conditions giving rise to them. While modeling one flare required only changes in the electron spectrum compared to the quiescent state, modeling the other flare required changes in both the electronmore » spectrum and the size of the emitting region. These results are consistent with an emerging pattern of two broad classes of flaring states seen in blazars. Type 1 flares are explained by changes solely in the electron distribution, whereas type 2 flares require a change in an additional parameter. Finally, this suggests that different flares, even in the same source, may result from different physical conditions or different regions in the jet.« less

A Very Bright, Very Hot, and Very Long Flaring Event from the M Dwarf Binary System DG CVn

NASA Technical Reports Server (NTRS)

Osten, Rachel A.; Kowalski, Adam; Drake, Stephen; Krimm, Hans; Page, Kim; Gazeas, Kosmas; Page, Mathew; Miguel, Enrique De; Novak, Rudolf; Gehrels, Cornelis

2016-01-01

On 2014 April 23, the Swift satellite responded to a hard X-ray transient detected by its Burst Alert Telescope, which turned out to be a stellar flare from a nearby, young M dwarf binary DG CVn. We utilize observations at X-ray, UV, optical, and radio wavelengths to infer the properties of two large flares. The X-ray spectrum of the primary outburst can be described over the 0.3100 kiloelectron volts bandpass by either a single very high-temperature plasma or a nonthermal thick-target bremsstrahlung model, and we rule out the nonthermal model based on energetic grounds. The temperatures were the highest seen spectroscopically in a stellar flare, at T(sub x) of 290 megakelvin. The first event was followed by a comparably energetic event almost a day later. We constrain the photospheric area involved in each of the two flares to be greater than 10(exp 20) sq cm, and find evidence from flux ratios in the second event of contributions to the white light flare emission in addition to the usual hot, T approximately 10(exp 4) K blackbody emission seen in the impulsive phase of flares. The radiated energy in X-rays and white light reveal these events to be the two most energetic X-ray flares observed from an M dwarf, with X-ray radiated energies in the 0.3-10 kiloelectron volts bandpass of 4 x 10(exp 35) and 9 x 10(exp 35) erg, and optical flare energies at E(sub V) of 2.8 x 10(exp 34) and 5.2 x 10(exp 34) erg, respectively. The results presented here should be integrated into updated modeling of the astrophysical impact of large stellar flares on close-in exoplanetary atmospheres.

Energy Release in Solar Flares,

DTIC Science & Technology

1982-10-01

Plasma Research, Stanford University P. Kaufmanu CRAA/CNPq -Conseiho lacional de Desenvolvimento Cientifico e Tecnologico, Slo Paulo, SP, Brasil D.F...three phases of energy release in solar flares (Sturrock, 1980). However, a recent article by Feldman e a.. (1982) points to a significant

Computational fluid dynamics modeling of laboratory flames and an industrial flare.

PubMed

Singh, Kanwar Devesh; Gangadharan, Preeti; Chen, Daniel H; Lou, Helen H; Li, Xianchang; Richmond, Peyton

2014-11-01

A computational fluid dynamics (CFD) methodology for simulating the combustion process has been validated with experimental results. Three different types of experimental setups were used to validate the CFD model. These setups include an industrial-scale flare setups and two lab-scale flames. The CFD study also involved three different fuels: C3H6/CH/Air/N2, C2H4/O2/Ar and CH4/Air. In the first setup, flare efficiency data from the Texas Commission on Environmental Quality (TCEQ) 2010 field tests were used to validate the CFD model. In the second setup, a McKenna burner with flat flames was simulated. Temperature and mass fractions of important species were compared with the experimental data. Finally, results of an experimental study done at Sandia National Laboratories to generate a lifted jet flame were used for the purpose of validation. The reduced 50 species mechanism, LU 1.1, the realizable k-epsilon turbulence model, and the EDC turbulence-chemistry interaction model were usedfor this work. Flare efficiency, axial profiles of temperature, and mass fractions of various intermediate species obtained in the simulation were compared with experimental data and a good agreement between the profiles was clearly observed. In particular the simulation match with the TCEQ 2010 flare tests has been significantly improved (within 5% of the data) compared to the results reported by Singh et al. in 2012. Validation of the speciated flat flame data supports the view that flares can be a primary source offormaldehyde emission.

An Unstable Arch Model of a Solar Flare

DTIC Science & Technology

1976-08-10

where the Euler-Lagrange equation becomes singular. We now expand f(r) and g(r) around the singular point r. Thus k JA + - p x, (3.20) m where x...current layer, etc.) can result only from convection. The equations we will use are ()B E 2 - VX(vXB)- _ VX(1TV XB), (4.8) E+ vX B=77j (4.9) C and curl (P...d- curl (J ( curl B) X B+pg . (4.10) Since the treatment is principally concerned with resistive instabilities whose growth times are long compared to

Temporal and Spectral Characteristics of X-Ray Bright Pleiads

NASA Astrophysics Data System (ADS)

Caillault, J.-P.; Gagne, M.; Yglesias, J.; Hartmann, L.; Prosser, C.; Stauffer, J.

1993-05-01

ROSAT PSPC observations of the Pleiades have allowed us to analyze the spectral and temporal characteristics of the X-ray sources within the cluster. Of the ~ 300 sources detected within the images, ~ 20-30 of them seem to be variable at the 99% confidence level (chi (2) -test). Numerous flares have also been found, the light curves of which we display. In addition, we have fit two-temperature Raymond-Smith thermal plasma models to the spectra of the ~ 6 brightest sources and examined whether these sources behave in accordance with coronal loop models. We also demonstrate that the two-temperature fit changes during a flare. We have constructed composite spectra for both shallow and deep convective zone stars in order to see whether there is a systematic change of spectral characteristics from spectral type F to M. Finally, in an attempt to discern possible evolutionary effects, we compare our results with those from the older Hyades cluster (Stern et al. 1993). This research was supported by NASA Grants NAG5-1608 to UGA and NAG5-1849 & NAGW-2698 to the CfA.

Modelling blazar flaring using a time-dependent fluid jet emission model - an explanation for orphan flares and radio lags

NASA Astrophysics Data System (ADS)

Potter, William J.

2018-01-01

Blazar jets are renowned for their rapid violent variability and multiwavelength flares, however, the physical processes responsible for these flares are not well understood. In this paper, we develop a time-dependent inhomogeneous fluid jet emission model for blazars. We model optically thick radio flares for the first time and show that they are delayed with respect to the prompt optically thin emission by ∼months to decades, with a lag that increases with the jet power and observed wavelength. This lag is caused by a combination of the travel time of the flaring plasma to the optically thin radio emitting sections of the jet and the slow rise time of the radio flare. We predict two types of flares: symmetric flares - with the same rise and decay time, which occur for flares whose duration is shorter than both the radiative lifetime and the geometric path-length delay time-scale; extended flares - whose luminosity tracks the power of particle acceleration in the flare, which occur for flares with a duration longer than both the radiative lifetime and geometric delay. Our model naturally produces orphan X-ray and γ-ray flares. These are caused by flares that are only observable above the quiescent jet emission in a narrow band of frequencies. Our model is able to successfully fit to the observed multiwavelength flaring spectra and light curves of PKS1502+106 across all wavelengths, using a transient flaring front located within the broad-line region.

Spectral Evolution of Intensive Microwave Bursts at Centimeter-Millimeter Wavelengths

NASA Astrophysics Data System (ADS)

Melnikov, V. F.; Magun, A.

The dynamics of the frequency spectrum of intensive broad band microwave bursts with one spectral maximum and simple time profiles are investigated. The aim of the study is to correlate the temporal evolution of the microwave burst spectrum above and below the spectral peak frequency f_p, as well as to compare these features with theoretical expectations. The analysis was carried out by using the data from the patrol instruments of IAP, Bern University and NIRFI, Nizhnii Novgorod (10 fixed frequencies in the range 1-50 GHz). It has been found for the majority of these bursts that: a) during the rise phase of the burst flux there is an anticorrelation of the absolute values of the spectral indices above and below peak frequency whereas a good correlation during the decay phase was found; b) time delays between flux profiles at neighbouring frequencies change sign under the transition from low to high frequencies. As a rule the lower frequency emission is delayed at frequencies below f_p whereas at high frequencies (f>f_p) the higher frequency emission is delayed (see also Melnikov and Magun, 1998). Qualitatively these results fit well the calculated spectral evolution of the gyrosynchrotron if one takes into account the flattening of the electron energy spectrum in a flare loop (Melnikov and Magun, 1996) due to Coulomb collisions (Vilmer et al., 1982), and uses values for the background plasma density derived from hard X-ray data (Aschwanden et al., 1997). For some of the bursts, however, quantitative discrepancies with the predictions of the homogeneous model have been found. For these bursts the absolute value of the spectral index at low frequencies is remarkably smaller, and the time delay remarkably higher than expected. We have investigated several possibilities to obtain an agremeent between theory and observations. Special attention is paid to model calculations taking into account the dynamics of energetic electrons in flare loops with an inhomogeneous magnetic field and plasma density. In this context the capabilities of the models for the diagnostics of the physical conditions in flare loops using observations with high spatial

The 1991 October 24 flare: A challenge for standard models

NASA Technical Reports Server (NTRS)

Beaujardiere, J.-F. De LA; Canfield, R. C.; Hudson, H. S.; Wulser, J.-P.; Acton, L.; Kosugi, T.; Masuda, S.

1995-01-01

The M9.8 solar flare of 1991 October 24 22:30 UT presents several interesting characteristics: (1) energy release starts high in the corona; (2) the primary chromospheric ribbons are initially well separated and do not move apart at an observable rate; (3) no evidence is found for an erupting filament or other driver. To explain this flare, we consider several canonical flare models, including a filament eruption, a confined filament eruption, current interruption, and interacting loops. We conclude that none of these scenarios unequivocally explains this flare. Two possibilities which cannot be ruled out are (1) the eruption of a filament unobservable in H-alpha which starts high in the corona and produces no ribbon motions smaller than our detection threshold and no perceptible expansion of the coronal X-ray source, and (2) energy release due to spontaneous, propagating reconnection which allows the system to essentially brighten in place.

Watch Out for Falling Plasma

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

The path taken by the falling fragment in the June 2011 event. [Adapted from Petralia et al. 2016]Sometimes plasma emitted from the Sun doesnt escape into space, but instead comes crashing back down to the solar surface. What can observations and models of this process tell us about how the plasma falls and the local conditions on the Sun?Fallback from a FlareOn 7 June 2011, an M-class flare erupted from the solar surface. As the Solar Dynamics Observatorys Atmospheric Imaging Assembly looked on, plasma fragments from the flare arced away from the Sun and then fell back to the surface.Some fragments fell back where the Suns magnetic field was weak, returning directly to the surface. But others fell within active regions, where they crashed into the Suns magnetic field lines, brightening the channels and funneling along them through the dense corona and back to the Suns surface.The authors model of the falling blobs at several different times in their simulation. The blobs get disrupted when they encounter the field lines, and are then funneled along the channels to the solar surface. [Adapted from Petralia et al. 2016]This sort of flare and fall-back event is a common occurrence with the Sun, and SDOs observations of the June 2011 event present an excellent opportunity to understand the process better. A team of scientists led by Antonino Petralia (University of Palermo, Italy and INAF-OAPA) modeled this event in an effort to learn more about how the falling plasma interacts with strong magnetic fields above the solar surface.Magnetic Fields as GuidesPetralia and collaborators used three-dimensional magnetohydrodynamical modeling to attempt to reproduce the observations of this event. They simulated blobs of plasma as they fall back to the solar surface and interact with magnetic field lines over a range of different conditions.The team found that only simulations that assume a relatively strong magnetic field resulted in the blobs funneling along a channel to the Suns surface; with weaker fields the blobs to simply broke through the field lines.The observations were best reproduced by downfall channeled in a million-Kelvin coronal loop confined by a magnetic field of 1020 Gauss. In this scenario, a falling fragment is deviated from its path by the field and disrupted. Its then channeled along the magnetic flux tube, driving a shock and heating in the tube ahead of it which, the authors find, is the cause the observed brightening that occurs ahead of the actual plasma passage.Petralia and collaborators point out that this new mechanism for brightening downflows channeled by the magnetic field is applicable not only in our Sun, but also in young, accreting stars. Events like these can therefore work as probes of the ambient atmosphere of such stars, providing information about the local plasma density and magnetic field.BonusCheck out the two awesome videos below! In the first one, you can see the SDO/AIA observations of the plasma fragment falling back down and hitting a magnetic channel, which lights up as the shock propagates. In the second one, you can see one of the authors models of this process; this video renders the density of blobs of plasma as they fall and strike magnetic field lines.http://cdn.iopscience.com/images/0004-637X/832/1/2/Full/apjaa3f55f1_video.mp4http://cdn.iopscience.com/images/0004-637X/832/1/2/Full/apjaa3f55f5_video.mp4CitationA. Petralia et al 2016 ApJ 832 2. doi:10.3847/0004-637X/832/1/2

Influences of misprediction costs on solar flare prediction

NASA Astrophysics Data System (ADS)

Huang, Xin; Wang, HuaNing; Dai, XingHua

2012-10-01

The mispredictive costs of flaring and non-flaring samples are different for different applications of solar flare prediction. Hence, solar flare prediction is considered a cost sensitive problem. A cost sensitive solar flare prediction model is built by modifying the basic decision tree algorithm. Inconsistency rate with the exhaustive search strategy is used to determine the optimal combination of magnetic field parameters in an active region. These selected parameters are applied as the inputs of the solar flare prediction model. The performance of the cost sensitive solar flare prediction model is evaluated for the different thresholds of solar flares. It is found that more flaring samples are correctly predicted and more non-flaring samples are wrongly predicted with the increase of the cost for wrongly predicting flaring samples as non-flaring samples, and the larger cost of wrongly predicting flaring samples as non-flaring samples is required for the higher threshold of solar flares. This can be considered as the guide line for choosing proper cost to meet the requirements in different applications.

OBSERVATIONS OF LOW ENERGY SOLAR COSMIC RAYS FROM THE FLARE OF AUGUST 22, 1958

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, K.A.; Arnoldy, R.; Hoffman, R.

1959-10-31

Observations were made of protons at balloon altitudes in the energy range 100 to 300 Mev following a solar sequence of optical flare, r-f noise bursts, and long enduring noise storm. Other particles are shown to have low upper limits to their abundance. The flare particles continue to be observed for at least 2 days and arguments are given to show that their storage and emission takes place in the solar atmosphere. The differential energy spectrum is derived from ionization versus atmospheric depth data and is found to be E/sup -5/ dE. Observations by riometer and VHF scatter propagation pathsmore » over the polar regions indicate that solar acceleration of protons up to roughly 100 Mev energy is rather frequent. (auth)« less

Physics of Coupled CME and Flare Systems

DTIC Science & Technology

2016-12-21

AFRL-RV-PS- AFRL-RV-PS- TR-2016-0162 TR-2016-0162 PHYSICS OF COUPLED CME AND FLARE SYSTEMS K. S. Balasubramaniam, et al. 21 December 2016 Final...30 Sep 2016 4. TITLE AND SUBTITLE Physics of Coupled CME and Flare Systems 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61102F...objectives for this task were: (i) derive measureable physical properties and discernible structural circumstances in solar active regions that

Temporal and Spectral Analyses of SGRs Observed by HETE-2

NASA Astrophysics Data System (ADS)

Nakagawa, Y. E.; Yoshida, A.; Maetou, M.; Suzuki, M.; Tamagawa, T.; Sakamoto, T.; Kawai, N.; Shirasaki, Y.; Tanaka, K.; Matsuoka, M.; Fenimore, E. E.; Galassi, M.; Atteia, J.-L.; Hurley, K.; Ricker, G. R.

2006-05-01

HETE-2 localized 63 flares from SGR1806-20 and 6 flares from SGR1900+14 in the summer periods from June 18 2001 through August 7 2005. We report on the temporal and spectral analyses of short flares from those SGRs. The estimation of T90 durations in 2-30 keV and 30-100 keV revealed that there is no difference between them with a few exceptions. For these exceptional short flares, there seems softening or possibly hardening during flares, but these spectral evolution are not common. We also found a good linear correlation between the rise and decay time, and they do not depend on a peak flux. We also found that the spectra are well reproduced by a sum of two blackbody models for all short flares. The temperatures are lying around 4 keV and 11 keV which are consistent with previous studies. They are not depend on either the magnitude of flare, the event morphology or the source.

Acute low back pain is marked by variability: An internet-based pilot study

PubMed Central

2011-01-01

Background Pain variability in acute LBP has received limited study. The objectives of this pilot study were to characterize fluctuations in pain during acute LBP, to determine whether self-reported 'flares' of pain represent discrete periods of increased pain intensity, and to examine whether the frequency of flares was associated with back-related disability outcomes. Methods We conducted a cohort study of acute LBP patients utilizing frequent serial assessments and Internet-based data collection. Adults with acute LBP (lasting ≤3 months) completed questionnaires at the time of seeking care, and at both 3-day and 1-week intervals, for 6 weeks. Back pain was measured using a numerical pain rating scale (NPRS), and disability was measured using the Oswestry Disability Index (ODI). A pain flare was defined as 'a period of increased pain lasting at least 2 hours, when your pain intensity is distinctly worse than it has been recently'. We used mixed-effects linear regression to model longitudinal changes in pain intensity, and multivariate linear regression to model associations between flare frequency and disability outcomes. Results 42 of 47 participants (89%) reported pain flares, and the average number of discrete flare periods per patient was 3.5 over 6 weeks of follow-up. More than half of flares were less than 4 hours in duration, and about 75% of flares were less than one day in duration. A model with a quadratic trend for time best characterized improvements in pain. Pain decreased rapidly during the first 14 days after seeking care, and leveled off after about 28 days. Patients who reported a pain flare experienced an almost 3-point greater current NPRS than those not reporting a flare (mean difference [SD] 2.70 [0.11]; p < 0.0001). Higher flare frequency was independently associated with a higher final ODI score (ß [SE} 0.28 (0.08); p = 0.002). Conclusions Acute LBP is characterized by variability. Patients with acute LBP report multiple distinct flares of pain, which correspond to discrete increases in pain intensity. A higher flare frequency is associated with worse disability outcomes. PMID:21974962

The Flare/CME Connection

NASA Technical Reports Server (NTRS)

Moore, Ron; Falconer, David; Sterling, Alphonse

2008-01-01

We present evidence supporting the view that, while many flares are produced by a confined magnetic explosion that does not produce a CME, every CME is produced by an ejective magnetic explosion that also produces a flare. The evidence is that the observed heliocentric angular width of the full-blown CME plasmoid in the outer corona (at 3 to 20 solar radii) is about that predicted by the standard model for CME production, from the amount of magnetic flux covered by the co-produced flare arcade. In the standard model, sheared and twisted sigmoidal field in the core of an initially closed magnetic arcade erupts. As it erupts, tether-cutting reconnection, starting between the legs of the erupting sigmoid and continuing between the merging stretched legs of the enveloping arcade, simultaneously produces a growing flare arcade and unleashes the erupting sigmoid and arcade to become the low-beta plasmoid (magnetic bubble) that becomes the CME. The flare arcade is the downward product of the reconnection and the CME plasmoid is the upward product. The unleashed, expanding CME plasmoid is propelled into the outer corona and solar wind by its own magnetic field pushing on the surrounding field in the inner and outer corona. This tether-cutting scenario predicts that the amount of magnetic flux in the full-blown CME plasmoid nearly equals that covered by the full-grown flare arcade. This equality predicts (1) the field strength in the flare region from the ratio of the angular width of the CME in the outer corona to angular width of the full-grown flare arcade, and (2) an upper bound on the angular width of the CME in the outer corona from the total magnetic flux in the active region from which the CME explodes. We show that these predictions are fulfilled by observed CMEs. This agreement validates the standard model. The model explains (1) why most CMEs have much greater angular widths than their co-produced flares, and (2) why the radial path of a CME in the outer corona can be laterally far offset from the co-produced flare.

Thermal and Nonthermal Contributions to the Solar Flare X-Ray Flux

NASA Technical Reports Server (NTRS)

Dennis, Brian R.; Phillips, K. J. H.; Sylwester, Janusz; Sylwester, Barbara; Schwartz, Richard A.; Tolbert, A. Kimberley

2004-01-01

The relative thermal and nonthermal contributions to the total energy budget of a solar flare are being determined through analysis of RHESSI X-ray imaging and spectral observations in the energy range from approx. 5 to approx. 50 keV. The classic ways of differentiating between the thermal and nonthermal components - exponential vs. sources - can now be combined for individual flares. In addition, RHESSI's sensitivity down to approx. 4 keV and energy resolution of approx. 1 keV FWHM allow the intensities and equivalent widths of the complex of highly ionized iron lines at approx. 6.7 keV and the complex of highly ionized iron and nickel lines at approx. 8 keV to be measured as a function of time. Using the spectral line and continuum intensities from the Chianti (version 4.2) atomic code, the thermal component of the total flare emission can be more reliably separated from the nonthermal component in the measured X-ray spectrum. The abundance of iron can also be determined from RHESSI line-to-continuum measurements as a function of time during larger flares. Results will be shown of the intensity and equivalent widths of these line complexes for several flares and the temperatures, emission measures, and iron abundances derived from them. Comparisons will be made with 6.7-keV Fe-line fluxes measured with the RESIK bent crystal spectrometer on the Coronas-F spacecraft operating in third order during the peak times of three flares (2002 May 31 at 00:12 UT, 2002 December 2 at 19:26 UT, and 2003 April 26 at 03:OO UT). During the rise and decay of these flares, RESIK was operating in first order allowing the continuum flux to be measured between 2.9 and 3.7 keV for comparison with RHESSI fluxes at its low-energy end.

On a Solar Origin for the Cosmogenic Nuclide Event of 775 A.D.

NASA Technical Reports Server (NTRS)

Cliver, E. W.; Tylka, A. J.; Dietrich, W. F.; Ling, A. G.

2014-01-01

We explore requirements for a solar particle event (SPE) and flare capable of producing the cosmogenic nuclide event of 775 A.D., and review solar circumstances at that time. A solar source for 775 would require a greater than 1 GV spectrum approximately 45 times stronger than that of the intense high-energy SPE of 1956 February 23. This implies a greater than 30 MeV proton fluence (F(sub 30)) of approximately 8 × 10(exp 10) proton cm(exp -2), approximately 10 times larger than that of the strongest 3 month interval of SPE activity in the modern era. This inferred F(sub 30) value for the 775 SPE is inconsistent with the occurrence probability distribution for greater than 30 MeV solar proton events. The best guess value for the soft X-ray classification (total energy) of an associated flare is approximately X230 (approximately 9 × 10(exp 33) erg). For comparison, the flares on 2003 November 4 and 1859 September 1 had observed/inferred values of approximately X35 (approximately 10(exp 33) erg) and approximately X45 (approximately 2 × 10(exp 33) erg), respectively. The estimated size of the source active region for a approximately 10(exp 34) erg flare is approximately 2.5 times that of the largest region yet recorded. The 775 event occurred during a period of relatively low solar activity, with a peak smoothed amplitude about half that of the second half of the 20th century. The approximately 1945-1995 interval, the most active of the last approximately 2000 yr, failed to witness a SPE comparable to that required for the proposed solar event in 775. These considerations challenge a recent suggestion that the 775 event is likely of solar origin.

Wavelength Dependence of Solar Flare Irradiation and its Influence on the Thermosphere

NASA Technical Reports Server (NTRS)

Huang, Yanshi; Richmond, Arthur D.; Deng, Yue; Qian, L.; Solomon, S.; Chamberlin, P.

2012-01-01

The wavelength dependence of solar flare enhancement is one of the important factors determining how the Thermosphere-Ionosphere (T-I) system response to flares. To investigate the wavelength dependence of solar flare, the Flare Irradiance Spectral Model (FISM) has been run for 34 X-class flares. The results show that the percentage increases of solar irradiance at flare peak comparing to pre-flare condition have a clear wavelength dependence. In the wavelength range between 0 - 195 nm, it can vary from 1% to 10000%. The solar irradiance enhancement is largest ( 1000%) in the XUV range (0 - 25 nm), and is about 100% in EUV range (25 - 120 nm). The influence of different wavebands on the T-I system during the October 28th, 2003 flare (X17.2-class) has also been examined using the latest version of National Center for Atmospheric Research (NCAR) Thermosphere- Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). While the globally integrated solar energy deposition is largest in the 0 - 14 nm waveband, the impact of solar irradiance enhancement on the thermosphere at 400 km is largest for 25 - 105 nm waveband. The effect of 122 - 195 nm is small in magnitude, but it decays slowly.

Flare frequency, healthcare resource utilisation and costs among patients with gout in a managed care setting: a retrospective medical claims-based analysis.

PubMed

Jackson, Robert; Shiozawa, Aki; Buysman, Erin K; Altan, Aylin; Korrer, Stephanie; Choi, Hyon

2015-06-24

For most gout patients, excruciatingly painful gout attacks are the major clinical burden of the disease. The goal of this study was to assess the association of frequent gout flares with healthcare burden, and to quantify how much lower gout-related costs and resource use are for those with infrequent flares compared to frequent gout flares. Retrospective cohort study. Administrative claims data from a large US health plan. Patients aged 18 years or above, and with evidence of gout based on medical and pharmacy claims between January 2009 and April 2012 were eligible for inclusion. Patient characteristics were assessed during a 12-month baseline period. Frequency of gout flares, healthcare costs and resource utilisation were assessed in the 12 months following the first qualifying gout claim. Generalised linear models were employed to assess the impact of flare frequency on cost outcomes after adjusting for covariates. 102,703 patients with gout met study inclusion criteria; 89,201 had 0-1 gout flares, 9714 had 2 flares, and 3788 had 3+ flares. Average counts of gout-related inpatient stays, emergency room visits and ambulatory visits were higher among patients with 2 or 3+ flares, compared to those with 0-1 flares (all p<0.001). Adjusted annual gout-related costs were $1804, $3014 and $4363 in those with 0-1, 2 and 3+ gout flares, respectively (p<0.001 comparing 0-1 flares to 2 or 3+ flares). Gout-related costs and resource use were lower for those with infrequent flares, suggesting significant cost benefit to a gout management plan that has a goal of reducing flare frequency. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

40 CFR 49.4165 - Control equipment requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., except for § 60.18(c)(2) and (f)(2) for those utility flares operated with an electronically controlled...) Equipped with one of the following: (A) A continuous burning pilot flame. (B) An electronically controlled... electronically controlled automatic igniter, such as a chart recorder, data logger or similar devices; (vi...

40 CFR 49.4165 - Control equipment requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., except for § 60.18(c)(2) and (f)(2) for those utility flares operated with an electronically controlled...) Equipped with one of the following: (A) A continuous burning pilot flame. (B) An electronically controlled... electronically controlled automatic igniter, such as a chart recorder, data logger or similar devices; (vi...

KOI-256's Magnetic Activity Under the Influence of the White Dwarf

NASA Astrophysics Data System (ADS)

Yoldaş, Ezgi; Dal, Hasan Ali

2017-11-01

We present the findings about chromospheric activity nature of KOI-256 obtained from the Kepler Mission data. First, it was found that there are some sinusoidal variations out-of-eclipses due to cool spot activity. The sinusoidal variations modelled by the spotmodel program indicate that the active component has two different active regions. Their longitudinal variation revealed that one of them has a migration period of 3.95 yrs, while the other has a migration period of 8.37 yrs. Second, 225 flares were detected from the short cadence data in total. The parameters, such as increase (T r) and decay (T d) times, total flare time (T t), equivalent durations (P), were calculated for each flare. The distribution of equivalent durations versus total flare times in logarithmic scale is modelled to find flare activity level. The Plateau value known as the saturation level of the active component was calculated to be 2.3121 ± 0.0964 s, and the Half-life value, which is required flare total time to reach the saturation, was computed to be 2233.6 s. In addition, the frequency of N 1, which is the number of flares per an hour in the system, was found to be 0.05087 h-1, while the flare frequency N 2 that the flare-equivalent duration emitting per an hour was found to be 0.00051. Contrary to the spot activity, it has been found that the flares are in tends to appear at specific phases due to the white dwarf component.

MULTI-WAVELENGTH OBSERVATIONS OF THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES WITH AIA/SDO. I. UNIVERSAL SCALING LAWS OF SPACE AND TIME PARAMETERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aschwanden, Markus J.; Zhang, Jie; Liu, Kai, E-mail: aschwanden@lmsal.com, E-mail: jzhang7@gmu.edu

2013-09-20

We extend a previous statistical solar flare study of 155 GOES M- and X-class flares observed with AIA/SDO to all seven coronal wavelengths (94, 131, 171, 193, 211, 304, and 335 Å) to test the wavelength dependence of scaling laws and statistical distributions. Except for the 171 and 193 Å wavelengths, which are affected by EUV dimming caused by coronal mass ejections (CMEs), we find near-identical size distributions of geometric (lengths L, flare areas A, volumes V, and fractal dimension D{sub 2}), temporal (flare durations T), and spatio-temporal parameters (diffusion coefficient κ, spreading exponent β, and maximum expansion velocities v{submore » max}) in different wavelengths, which are consistent with the universal predictions of the fractal-diffusive avalanche model of a slowly driven, self-organized criticality (FD-SOC) system, i.e., N(L)∝L {sup –3}, N(A)∝A {sup –2}, N(V)∝V {sup –5/3}, N(T)∝T {sup –2}, and D{sub 2} = 3/2, for a Euclidean dimension d = 3. Empirically, we find also a new strong correlation κ∝L {sup 0.94±0.01} and the three-parameter scaling law L∝κ T {sup 0.1}, which is more consistent with the logistic-growth model than with classical diffusion. The findings suggest long-range correlation lengths in the FD-SOC system that operate in the vicinity of a critical state, which could be used for predictions of individual extreme events. We find also that eruptive flares (with accompanying CMEs) have larger volumes V, longer flare durations T, higher EUV and soft X-ray fluxes, and somewhat larger diffusion coefficients κ than confined flares (without CMEs)« less

FISM 2.0: Improved Spectral Range, Resolution, and Accuracy

NASA Technical Reports Server (NTRS)

Chamberlin, Phillip C.

2012-01-01

The Flare Irradiance Spectral Model (FISM) was first released in 2005 to provide accurate estimates of the solar VUV (0.1-190 nm) irradiance to the Space Weather community. This model was based on TIMED SEE as well as UARS and SORCE SOLSTICE measurements, and was the first model to include a 60 second temporal variation to estimate the variations due to solar flares. Along with flares, FISM also estimates the tradition solar cycle and solar rotational variations over months and decades back to 1947. This model has been highly successful in providing driving inputs to study the affect of solar irradiance variations on the Earth's ionosphere and thermosphere, lunar dust charging, as well as the Martian ionosphere. The second version of FISM, FISM2, is currently being updated to be based on the more accurate SDO/EVE data, which will provide much more accurate estimations in the 0.1-105 nm range, as well as extending the 'daily' model variation up to 300 nm based on the SOLSTICE measurements. with the spectral resolution of SDO/EVE along with SOLSTICE and the TIMED and SORCE XPS 'model' products, the entire range from 0.1-300 nm will also be available at 0.1 nm, allowing FISM2 to be improved a similar 0.1nm spectral bins. FISM also will have a TSI component that will estimate the total radiated energy during flares based on the few TSI flares observed to date. Presented here will be initial results of the FISM2 modeling efforts, as well as some challenges that will need to be overcome in order for FISM2 to accurately model the solar variations on time scales of seconds to decades.

Comparative efficacy of bilastine, desloratadine and rupatadine in the suppression of wheal and flare response induced by intradermal histamine in healthy volunteers.

PubMed

Antonijoan, Rosa; Coimbra, Jimena; García-Gea, Consuelo; Puntes, Montserrat; Gich, Ignasi; Campo, Cristina; Valiente, Román; Labeaga, Luis

2017-01-01

To compare the peripheral antihistaminic activity of bilastine, rupatadine and desloratadine in inhibiting the histamine-induced wheal and flare (W&F) response. Twenty-four healthy volunteers aged 18-40 years participated in this crossover, randomized, double-blind, placebo-controlled clinical study. Subjects received single doses of bilastine 20 mg, desloratadine 5 mg, rupatadine 10 mg and placebo. W&F responses induced by intradermal injection of histamine 5 μg were evaluated before treatment (basal value) and at 0.5, 1, 2, 4, 6, 9, 12 and 24 hours after treatment. Fifteen minutes after histamine injection, W&F surface areas (cm 2 ) were quantified using the Visitrak System. Itching sensation was evaluated using a 100 mm visual analog scale. EudraCT number: 2015-000790-13. The primary outcome measure was the percentage reduction in W&F areas after each active treatment compared with corresponding basal values. Bilastine induced the greatest inhibition in wheal area and was significantly superior to desloratadine and rupatadine from 1 to 12 hours (both p < .001). Rupatadine and desloratadine were better than placebo without differences between them. Maximum wheal inhibition occurred at 6 hours (bilastine 83%, desloratadine 38%, rupatadine 37%). Onset of action was 1 hour for bilastine and 4 hours for desloratadine and rupatadine. Bilastine was significantly superior to desloratadine and rupatadine for flare inhibition from 1-24 hours (both p < .001) with an onset of action at 30 minutes. Bilastine was significantly better than desloratadine (2-12 hours; at least p < .05) and rupatadine (2-9 hours; at least p < .01) for reducing itching sensation. Neither desloratadine nor rupatadine significantly reduced itching compared to placebo. All active treatments were well tolerated. Bilastine 20 mg induced significantly greater inhibition of the W&F response compared with desloratadine 5 mg and rupatadine 10 mg throughout the 24 hour study period, and had the fastest onset of action. Only bilastine significantly reduced itching sensation versus placebo.

Gas flaring and resultant air pollution: A review focusing on black carbon.

PubMed

Fawole, Olusegun G; Cai, X-M; MacKenzie, A R

2016-09-01

Gas flaring is a prominent source of VOCs, CO, CO2, SO2, PAH, NOX and soot (black carbon), all of which are important pollutants which interact, directly and indirectly, in the Earth's climatic processes. Globally, over 130 billion cubic metres of gas are flared annually. We review the contribution of gas flaring to air pollution on local, regional and global scales, with special emphasis on black carbon (BC, "soot"). The temporal and spatial characteristics of gas flaring distinguishes it from mobile combustion sources (transport), while the open-flame nature of gas flaring distinguishes it from industrial point-sources; the high temperature, flame control, and spatial compactness distinguishes gas flaring from both biomass burning and domestic fuel-use. All of these distinguishing factors influence the quantity and characteristics of BC production from gas flaring, so that it is important to consider this source separately in emissions inventories and environmental field studies. Estimate of the yield of pollutants from gas flaring have, to date, paid little or no attention to the emission of BC with the assumption often being made that flaring produces a smokeless flame. In gas flares, soot yield is known to depend on a number of factors, and there is a need to develop emission estimates and modelling frameworks that take these factors into consideration. Hence, emission inventories, especially of the soot yield from gas flaring should give adequate consideration to the variation of fuel gas composition, and to combustion characteristics, which are strong determinants of the nature and quantity of pollutants emitted. The buoyant nature of gas flaring plume, often at temperatures in the range of 2000 K, coupled with the height of the stack enables some of the pollutants to escape further into the free troposphere aiding their long-range transport, which is often not well-captured by model studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Flares assessed weekly in patients with rheumatoid arthritis or axial spondyloarthritis and relationship with physical activity measured using a connected activity tracker: a 3-month study.

PubMed

Jacquemin, Charlotte; Molto, Anna; Servy, Hervé; Sellam, Jérémie; Foltz, Violaine; Gandjbakhch, Frédérique; Hudry, Christophe; Mitrovic, Stéphane; Granger, Benjamin; Fautrel, Bruno; Gossec, Laure

2017-01-01

The evolution of rheumatoid arthritis (RA) and axial spondyloarthritis (axSpA) is marked by flares, although their frequency is unclear. Flares may impact physical activity. Activity can be assessed objectively using activity trackers. The objective was to assess longitudinally the frequency of flares and the association between flares and objective physical activity. This prospective observational study (ActConnect) included patients with definite clinician-confirmed RA or axSpA, owning a smartphone. During 3 months, physical activity was assessed continuously by number of steps/day, using an activity tracker, and disease flares were self-assessed weekly using a specific flare question and, if relevant, the duration of the flare. The relationship between flares and physical activity for each week (time point) was assessed by linear mixed models. In all, 170/178 patients (91 patients with RA and 79 patients with axSpA; 1553 time points) were analysed: mean age was 45.5±12.4 years, mean disease duration was 10.3±8.7 years, 60 (35.3%) were men and 90 (52.9%) received biologics. The disease was well-controlled (mean Disease Activity Score 28: 2.3±1.2; mean Bath Ankylosing Spondylitis Disease Activity Index score: 3.3±2.1). Patients self-reported flares in 28.2%±28.1% of the weekly assessments. Most flares (78.9%±31.4%) lasted ≤3 days. Persistent flares lasting more than 3 days were independently associated with less weekly physical activity (p=0.03), leading to a relative decrease of 12%-21% and an absolute decrease ranging from 836 to 1462 steps/day. Flares were frequent but usually of short duration in these stable patients with RA and axSpA. Persistent flares were related to a moderate decrease in physical activity, confirming objectively the functional impact of patient-reported flares.

Flares assessed weekly in patients with rheumatoid arthritis or axial spondyloarthritis and relationship with physical activity measured using a connected activity tracker: a 3-month study

PubMed Central

Jacquemin, Charlotte; Molto, Anna; Servy, Hervé; Sellam, Jérémie; Foltz, Violaine; Gandjbakhch, Frédérique; Hudry, Christophe; Mitrovic, Stéphane; Granger, Benjamin; Fautrel, Bruno; Gossec, Laure

2017-01-01

Background The evolution of rheumatoid arthritis (RA) and axial spondyloarthritis (axSpA) is marked by flares, although their frequency is unclear. Flares may impact physical activity. Activity can be assessed objectively using activity trackers. The objective was to assess longitudinally the frequency of flares and the association between flares and objective physical activity. Methods This prospective observational study (ActConnect) included patients with definite clinician-confirmed RA or axSpA, owning a smartphone. During 3 months, physical activity was assessed continuously by number of steps/day, using an activity tracker, and disease flares were self-assessed weekly using a specific flare question and, if relevant, the duration of the flare. The relationship between flares and physical activity for each week (time point) was assessed by linear mixed models. Results In all, 170/178 patients (91 patients with RA and 79 patients with axSpA; 1553 time points) were analysed: mean age was 45.5±12.4 years, mean disease duration was 10.3±8.7 years, 60 (35.3%) were men and 90 (52.9%) received biologics. The disease was well-controlled (mean Disease Activity Score 28: 2.3±1.2; mean Bath Ankylosing Spondylitis Disease Activity Index score: 3.3±2.1). Patients self-reported flares in 28.2%±28.1% of the weekly assessments. Most flares (78.9%±31.4%) lasted ≤3 days. Persistent flares lasting more than 3 days were independently associated with less weekly physical activity (p=0.03), leading to a relative decrease of 12%–21% and an absolute decrease ranging from 836 to 1462 steps/day. Conclusion Flares were frequent but usually of short duration in these stable patients with RA and axSpA. Persistent flares were related to a moderate decrease in physical activity, confirming objectively the functional impact of patient-reported flares. PMID:28879046

Effect of a Flared Renal Stent on the Performance of Fenestrated Stent-Grafts at Rest and Exercise Conditions.

PubMed

Kandail, Harkamaljot; Hamady, Mohamad; Xu, Xiao Yun

2016-10-01

To quantify the hemodynamic impact of a flared renal stent on the performance of fenestrated stent-grafts (FSGs) by analyzing flow patterns and wall shear stress-derived parameters in flared and nonflared FSGs in different physiologic scenarios. Hypothetical models of FSGs were created with and without flaring of the proximal portion of the renal stent. Flared FSGs with different dilation angles and protrusion lengths were examined, as well as a nonplanar flared FSG to account for lumbar curvature. Laminar and pulsatile blood flow was simulated by numerically solving Navier-Stokes equations. A physiologically realistic flow rate waveform was prescribed at the inlet, while downstream vasculature was modeled using a lumped parameter 3-element windkessel model. No slip boundary conditions were imposed at the FSG walls, which were assumed to be rigid. While resting simulations were performed on all the FSGs, exercise simulations were also performed on a flared FSG to quantify the effect of flaring in different physiologic scenarios. For cycle-averaged inflow of 2.94 L/min (rest) and 4.63 L/min (exercise), 27% of blood flow was channeled into each renal branch at rest and 21% under exercise for all the flared FSGs examined. Although the renal flow waveform was not affected by flaring, flow within the flared FSGs was disturbed. This flow disturbance led to high endothelial cell activation potential (ECAP) values at the renal ostia for all the flared geometries. Reducing the dilation angle or protrusion length and exercise lowered the ECAP values for flared FSGs. Flaring of renal stents has a negligible effect on the time dependence of renal flow rate waveforms and can maintain sufficient renal perfusion at rest and exercise. Local flow patterns are, however, strongly dependent on renal flaring, which creates a local flow disturbance and may increase the thrombogenicity at the renal ostia. Smaller dilation angles, shorter protrusion lengths, and moderate lower limb exercise are likely to reduce the risk of thrombosis in flared geometries. © The Author(s) 2016.

The Rise and Fall of μ Velorum: A Remarkable Flare on a Yellow Giant Star Observed with the Extreme Ultraviolet Explorer

NASA Astrophysics Data System (ADS)

Ayres, Thomas R.; Osten, Rachel A.; Brown, Alexander

1999-11-01

The close visual double μ Velorum (HD 93497; G6 III+dF) consists of a yellow giant and a fainter companion currently 2" apart. Recently μ Vel was the source of a large flare recorded by the Extreme Ultraviolet Explorer. The long 1.5 day decay phase was like the extremes seen on hyperactive RS CVn-type binaries. The primary, μ Vel A is a 3 Msolar star, in the ``rapid braking zone'' redward of G0 III. Yellow giants are not commonly reported as flare stars, perhaps because the first-crossers are relatively rare and not well represented in the observational samples. The secondary star is classified G2 V, but the 1700 Å energy distribution places it earlier on the main sequence, probably F4 or F5 V, in a class also not usually known for coronal variability. The long duration of the μ Vel event suggests that it occurred in a significantly elongated structure of moderate density, ne<~109 cm-3. If it was a magnetic plasmoid, like a coronal mass ejection on the Sun, then such events might play a role in shedding angular momentum from active evolved stars. The associated spin-down could control the activity survival time of red giants (in later stages of evolution than the first-crosser μ Vel) whose dynamos were rejunvenated by dredge-up of angular momentum from the interior, or more exotic sources, such as cannibalism of close-in substellar companions during the first or second ascent.

A new use of high resolution magnetograms. [solar activity and magnetic flux

NASA Technical Reports Server (NTRS)

Baum, P. J.; Bratenahl, A.

1978-01-01

Ground-based solar magnetograms are frequently in error by as much as twenty percent and contribute to the poor correlation between magnetic changes and solar flares. High resolution measurement of the magnetic field component, which is normal to the photosphere and measured at photospheric height, can be used to construct a magnetic flux partition function F. Therefore, dF/dt is an EMF which drives atmospheric currents in reconnecting solar active regions. With a high quality magnetograph, the solar probe can be used to obtain good estimates of F and dF/dt and thereby the energy stored as induced solar atmospheric currents during quiescent interflare periods. Should a flare occur during a favorable observing period, the present method of analysis should show characteristic signatures in F, DF/dt, and especially, in the stored flux computed from dF/dt.

Digging for Fossils in the Hertzsprung Gap

NASA Technical Reports Server (NTRS)

Ayres, Thomas R.

1999-01-01

Objective was to conduct deep (approx. 250 ks) pointings on two EUV sources, the early-F giant beta Cas and the mid-G giant mu Velorum; to obtain spectra in the range 70-300 A and to record Deep Survey light curves over the extensive duration of each observation. We have analyzed the DS lightcurve and the SW spectrum, breaking the latter lip into time slices corresponding to key phases of the observation: pre-flare, flare rise, and two segments of the flare decay.

The frequency of stellar X-ray flares from a large-scale XMM-Newton sample

NASA Astrophysics Data System (ADS)

Pye, John P.; Rosen, Simon

2015-08-01

We present a uniform, large-scale survey of X-ray flare emission, with emphasis on the corrections needed to arrive at estimates of flare occurrence rates. The XMM-Newton Serendipitous Source Catalogue has been used as the basis for a survey of X-ray flares from late-type (i.e. spectral type F-M) stars in the Hipparcos Tycho catalogue. The XMM catalogue and its associated data products provide an excellent basis for a comprehensive and sensitive survey of stellar flares - both from targeted active stars and from those observed serendipitously in the half-degree diameter field-of-view of each observation. Our sample contains ~130 flares with well-observed profiles; they range in duration from ~103 to ~104s, have peak X-ray fluxes from ~10-13 to ~10-11 erg cm-2 s-1, peak X-ray luminosities from ~1029 to ~1032 erg s-1 and X-ray energy output from ~1032 to ~1035 erg. Most of the serendipitously-observed stars have little previously reported information. We present flare frequency distributions from both target and serendipitous observations. The latter provide an unbiased (with respect to stellar activity) study of flare energetics. The serendipitous sample demonstrates the need for care when calculating flaring rates, especially when normalising the number of flares to a total exposure time, where it is important to consider both the stars seen to flare and those measured as non-variable, since in our survey, the latter outnumber the former by more than a factor ten. The serendipitous variable and non-variable stars appear very similar in terms of the distributions of general properties such as quiescent X-ray luminosity; from the available data, it is unclear whether the distinction by flaring is due to an additional, intrinsic property such as intra-system interactions in a close binary system, or is simply the result of limited observations of a random flaring process, with no real difference between the two samples. We discuss future observations and analyses aimed at resolving this issue.

Center-to-Limb Variability of Hot Coronal EUV Emissions During Solar Flares

NASA Astrophysics Data System (ADS)

Thiemann, E. M. B.; Chamberlin, P. C.; Eparvier, F. G.; Epp, L.

2018-02-01

It is generally accepted that densities of quiet-Sun and active region plasma are sufficiently low to justify the optically thin approximation, and this is commonly used in the analysis of line emissions from plasma in the solar corona. However, the densities of solar flare loops are substantially higher, compromising the optically thin approximation. This study begins with a radiative transfer model that uses typical solar flare densities and geometries to show that hot coronal emission lines are not generally optically thin. Furthermore, the model demonstrates that the observed line intensity should exhibit center-to-limb variability (CTLV), with flares observed near the limb being dimmer than those occurring near disk center. The model predictions are validated with an analysis of over 200 flares observed by the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO), which uses six lines, with peak formation temperatures between 8.9 and 15.8 MK, to show that limb flares are systematically dimmer than disk-center flares. The data are then used to show that the electron column density along the line of sight typically increases by 1.76 × 10^{19} cm^{-2} for limb flares over the disk-center flare value. It is shown that the CTLV of hot coronal emissions reduces the amount of ionizing radiation propagating into the solar system, and it changes the relative intensities of lines and bands commonly used for spectral analysis.

Flares from small to large: X-ray spectroscopy of Proxima Centauri with XMM-Newton

NASA Astrophysics Data System (ADS)

Güdel, M.; Audard, M.; Reale, F.; Skinner, S. L.; Linsky, J. L.

2004-03-01

We report results from a comprehensive study of the nearby M dwarf Proxima Centauri with the XMM-Newton satellite, using simultaneously its X-ray detectors and the Optical Monitor with its U band filter. We find strongly variable coronal X-ray emission, with flares ranging over a factor of 100 in peak flux. The low-level emission is found to be continuously variable on at least three time scales (a slow decay of several hours, modulation on a time scale of 1 hr, and weak flares with time scales of a few minutes). Several weak flares are characteristically preceded by an optical burst, compatible with predictions from standard solar flare models. We propose that the U band bursts are proxies for the elusive stellar non-thermal hard X-ray bursts suggested from solar observations. In the course of the observation, a very large X-ray flare started and was observed essentially in its entirety. Its peak luminosity reached 3.9× 1028 erg s-1 [0.15-10 keV], and the total X-ray energy released in the same band is derived to be 1.5× 1032 ergs. This flare has for the first time allowed to measure significant density variations across several phases of the flare from X-ray spectroscopy of the O VII He-like triplet; we find peak densities reaching up to 4× 1011 cm-3 for plasma of about 1-5 MK. Abundance ratios show little variability in time, with a tendency of elements with a high first ionization potential to be overabundant relative to solar photospheric values. Using Fe XVII lines with different oscillator strengths, we do not find significant effects due to opacity during the flare, indicating that large opacity increases are not the rule even in extreme flares. We model the large flare in terms of an analytic 2-Ribbon flare model and find that the flaring loop system should have large characteristic sizes (≈ 1R*) within the framework of this simplistic model. These results are supported by full hydrodynamic simulations. Comparing the large flare to flares of similar size occurring much more frequently on more active stars, we propose that the X-ray properties of active stars are a consequence of superimposed flares such as the example analyzed in this paper. Since larger flares produce hotter plasma, such a model also explains why, during episodes of low-level emission, more active stars show hotter plasma than less active stars. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).

A satellite-based analysis of the Val d'Agri Oil Center (southern Italy) gas flaring emissions

NASA Astrophysics Data System (ADS)

Faruolo, M.; Coviello, I.; Filizzola, C.; Lacava, T.; Pergola, N.; Tramutoli, V.

2014-10-01

In this paper, the robust satellite techniques (RST), a multi-temporal scheme of satellite data analysis, was implemented to analyze the flaring activity of the Val d'Agri Oil Center (COVA), the largest Italian gas and oil pre-treatment plant, owned by Ente Nazionale Idrocarburi (ENI). For this site, located in an anthropized area characterized by a large environmental complexity, flaring emissions are mainly related to emergency conditions (i.e., waste flaring), as industrial processes are regulated by strict regional laws. While regarding the peculiar characteristics of COVA flaring, the main aim of this work was to assess the performances of RST in terms of sensitivity and reliability in providing independent estimations of gas flaring volumes in such conditions. In detail, RST was implemented for 13 years of Moderate Resolution Imaging Spectroradiometer (MODIS) medium and thermal infrared data in order to identify the highly radiant records associated with the COVA flare emergency discharges. Then, using data provided by ENI about gas flaring volumes in the period 2003-2009, a MODIS-based regression model was developed and tested. The results achieved indicate that the such a model is able to estimate, with a good level of accuracy (R2 of 0.83), emitted gas flaring volumes at COVA.

A satellite-based analysis of the Val d'Agri (South of Italy) Oil Center gas flaring emissions

NASA Astrophysics Data System (ADS)

Faruolo, M.; Coviello, I.; Filizzola, C.; Lacava, T.; Pergola, N.; Tramutoli, V.

2014-06-01

In this paper the Robust Satellite Techniques (RST), a multi-temporal scheme of satellite data analysis, was implemented to analyze the flaring activity of the largest Italian gas and oil pre-treatment plant (i.e. the Ente Nazionale Idrocarburi - ENI - Val d'Agri Oil Center - COVA). For this site, located in an anthropized area characterized by a~large environmental complexity, flaring emissions are mainly related to emergency conditions (i.e. waste flaring), being the industrial process regulated by strict regional laws. With reference to the peculiar characteristics of COVA flaring, the main aim of this work was to assess the performances of RST in terms of sensitivity and reliability in providing independent estimations of gas flaring volumes in such conditions. In detail, RST was implemented on thirteen years of Moderate Resolution Imaging Spectroradiometer (MODIS) medium and thermal infrared data in order to identify the highly radiant records associated to the COVA flare emergency discharges. Then, exploiting data provided by ENI about gas flaring volumes in the period 2003-2009, a MODIS-based regression model was developed and tested. Achieved results indicate that such a model is able to estimate, with a good level of accuracy (R2 of 0.83), emitted gas flaring volumes at COVA.

Narrow-band radio flares from red dwarf stars

NASA Technical Reports Server (NTRS)

White, Stephen M.; Kundu, Mukul R.; Jackson, Peter D.

1986-01-01

VLA observations of narrow-band behavior in 20 cm flares from two red dwarf stars, L726 - 8A and AD Leo, are reported. The flare on L726 - 8A was observed at 1415 and 1515 MHz; the flux and the evolution differed significantly at the two frequencies. The flare on AD Leo lasted for 2 hr at 1415 MHz but did not appear at 1515 MHz. The AD Leo flare appears to rule out a source drifting through the stellar corona and is unlikely to be due to plasma emission. In the cyclotron maser model the narrow-band behavior reflects the range of magnetic fields present within the source. The apparent constancy of this field for 2 hr is difficult to understand if magnetic reconnection is the source of energy for the flare. The consistent polarization exhibited by red dwarf flares at 20 cm may be related to stellar activity cycles, and changes in this polarization will permit measuring the length of these cycles.

A New Paradigm for Flare Particle Acceleration

NASA Astrophysics Data System (ADS)

Guidoni, Silvina E.; Karpen, Judith T.; DeVore, C. Richard

2017-08-01

The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission and its spectra in solar flares is not well understood. Here, we propose a first-principle-based model of particle acceleration that produces energy spectra that closely resemble those derived from hard X-ray observations. Our mechanism uses contracting magnetic islands formed during fast reconnection in solar flares to accelerate electrons, as first proposed by Drake et al. (2006) for kinetic-scale plasmoids. We apply these ideas to MHD-scale islands formed during fast reconnection in a simulated eruptive flare. A simple analytic model based on the particles’ adiabatic invariants is used to calculate the energy gain of particles orbiting field lines in our ultrahigh-resolution, 2.5D, MHD numerical simulation of a solar eruption (flare + coronal mass ejection). Then, we analytically model electrons visiting multiple contracting islands to account for the observed high-energy flare emission. Our acceleration mechanism inherently produces sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each macroscopic island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare current sheet is a promising candidate for electron acceleration in solar eruptions. This work was supported in part by the NASA LWS and H-SR programs..

Statistical and observational research of solar flare for total spectra and geometrical features

NASA Astrophysics Data System (ADS)

Nishimoto, S.; Watanabe, K.; Imada, S.; Kawate, T.; Lee, K. S.

2017-12-01

Impulsive energy release phenomena such as solar flares, sometimes affect to the solar-terrestrial environment. Usually, we use soft X-ray flux (GOES class) as the index of flare scale. However, the magnitude of effect to the solar-terrestrial environment is not proportional to that scale. To identify the relationship between solar flare phenomena and influence to the solar-terrestrial environment, we need to understand the full spectrum of solar flares. There is the solar flare irradiance model named the Flare Irradiance Spectral Model (FISM) (Chamberlin et al., 2006, 2007, 2008). The FISM can estimate solar flare spectra with high wavelength resolution. However, this model can not express the time evolution of emitted plasma during the solar flare, and has low accuracy on short wavelength that strongly effects and/or controls the total flare spectra. For the purpose of obtaining the time evolution of total solar flare spectra, we are performing statistical analysis of the electromagnetic data of solar flares. In this study, we select solar flare events larger than M-class from the Hinode flare catalogue (Watanabe et al., 2012). First, we focus on the EUV emission observed by the SDO/EVE. We examined the intensities and time evolutions of five EUV lines of 55 flare events. As a result, we found positive correlation between the "soft X-ray flux" and the "EUV peak flux" for all EVU lines. Moreover, we found that hot lines peaked earlier than cool lines of the EUV light curves. We also examined the hard X-ray data obtained by RHESSI. When we analyzed 163 events, we found good correlation between the "hard X-ray intensity" and the "soft X-ray flux". Because it seems that the geometrical features of solar flares effect to those time evolutions, we also looked into flare ribbons observed by SDO/AIA. We examined 21 flare events, and found positive correlation between the "GOES duration" and the "ribbon length". We also found positive correlation between the "ribbon length" and the "ribbon distance", however, there was no remarkable correlation of the "ribbon width". To understand physical process of flare emission, we performed numerical simulation (Imada et al., 2015), and compared with the observational flare model. We also discuss the flare numerical model which can be fitted to the observational flare model.

The background model in the energy range from 0.1 MeV up to several MeV for low altitude and high inclination satellites.

NASA Astrophysics Data System (ADS)

Arkhangelskaja, I. V.; Arkhangelskiy, A. I.

2016-02-01

The gamma-ray background physical origin for low altitude orbits defined by: diffuse cosmic gamma-emission, atmospheric gamma-rays, gamma-emission formed in interactions of charged particles (both prompt and activation) and transient events such as electrons precipitations and solar flares. The background conditions in the energy range from 0.1 MeV up to several MeV for low altitude orbits differ due to frequency of Earth Radiation Belts - ERBs (included South Atlantic Anomaly - SAA) passes and cosmic rays rigidity. The detectors and satellite constructive elements are activated by trapped in ERBs and moving along magnetic lines charged particles. In this case we propose simplified polynomial model separately for polar and equatorial orbits parts: background count rate temporal profile approximation by 4-5 order polynomials in equatorial regions, and linear approximations, parabolas or constants in polar caps. The polynomials’ coefficients supposed to be similar for identical spectral channels for each analyzed equatorial part taken into account normalization coefficients defined due to Kp-indexes study within period corresponding to calibration coefficients being approximately constants. The described model was successfully applied for the solar flares hard X-ray and gamma-ray emission characteristic studies by AVS-F apparatus data onboard CORONAS-F satellite.

Multifrequency observations of AB Doradus. X-ray flaring and rotational modulation of a young star

NASA Astrophysics Data System (ADS)

Vilhu, O.; Tsuru, T.; Collier Cameron, A.; Budding, E.; Banks, T.; Slee, B.; Ehrenfreund, P.; Foing, B. H.

1993-11-01

X-ray observations of AB Doradus, performed by the Large Area Counter (LAC) instrument of the GINGA satellite on January 1990, are reported. The observations covered 5 rotations of the star (2.6 days) during which 4 flares were detected. When added to the previously observed EINSTEIN and EXOSAT flares, a total of 7 X-ray flares in AB Dor have been observed so far. The flares seem to cluster around rotational phases 0.1-0.25 and 0.6-0.75 although the statistics are poor. The mean flare energies were around (1-3) x 1034 erg with peak luminosities (4-6) x 1030 ergs/s. The flaring loops were compact (ne = 1012/cu cm) and extended (1-2) x 1010 cm above the surface. Flare masses (1018 g) and frequencies (two per day) are similar to prominence-like cloud formations discovered previously in the star. The flare spectra can be best-fitted either by thermal Bremstrahlung with kT = 3-6 keV or with a power-law, with photon index gamma = 2.2-2.6. During the strongest flare peaks AB Dor is a 10 mCrab source with a Crab-like spectrum. The 3 sigma upper limit for the 6.7 keV iron line during the flares is somewhat smaller than predicted by thin plasma models. We discuss the possibility of lowering the equivalent width by an extra non-thermal continuum due to mildly relativistic electrons. Simultaneous 8.4 GHz observations during flare No. 1 gave only a marginal detection, constraining the magnetic field strength to less than 50 Gauss if the total X-ray continuum is non-thermal in origin. The sensitivity was not good enough to detect any clear modulation in the X-ray light curve, folded over the 0.514 d rotation period. Simultaneous 8.4 GHz observations were performed with the 64 m antenna of the Australia Telescope National Facility at Parkes and reveal a clear variability with two maxima at phases 0.0 (spot A) and 0.5 (spot B). Nearly simultaneous optical photometry can be modeled by a cool extended photospheric spot at the phase 0.0 (spot A). Simultaneous H-alpha photometry revealed a transient H-alpha absorption feature above the spot A, trapped in co-rotation with the stellar magnetic field. All these multifrequency data can be understood by a geometrical two spot model. The geometry seems to have been permanent during the past 10 years, although the relative contributions of the two poles vary and the spots are not necessarily fixed into 180 degrees apart all the time.

The beam-driven chromospheric evaporation model of solar flares - A model not supported by observations from nonimpulsive large flares

NASA Technical Reports Server (NTRS)

Feldman, U.

1990-01-01

Most large solar flares exhibit hard X-ray emission which is usually impulsive, as well as thermal soft X-ray emission, which is gradual. The beam-driven chromospheric evaporation model of solar flares was proposed to explain the origin of the soft X-ray emitting flare plasma. A careful evaluation of the issue under discussion reveals contradictions between predictions from the theoretical chromospheric evaporation model and actual observations from a set of large X- and M-type flares. It is shown that although the soft X-ray and hard X-ray emissions are a result of the same flare, one is not a result of the other.

Time delays in the nonthermal radiation of solar flares according to observations of the CORONAS-F satellite

NASA Astrophysics Data System (ADS)

Tsap, Yu. T.; Stepanov, A. V.; Kashapova, L. K.; Myagkova, I. N.; Bogomolov, A. V.; Kopylova, Yu. G.; Goldvarg, T. B.

2016-07-01

In 2001-2003, the X-ray and microwave observations of ten solar flares of M- and X-classes were carried out by the CORONAS-F orbital station, the RSTN Sun service, and Nobeyama radio polarimeters. Based on these observations, a correlation analysis of time profiles of nonthermal radiation was performed. On average, hard X-ray radiation outstrips the microwave radiation in 9 events, i.e., time delays are positive. The appearance of negative delays is associated with effective scattering of accelerated electrons in pitch angles, where the length of the free path of a particle is less than the half-length of a flare loop. The additional indications are obtained in favor of the need to account for the effect of magnetic mirrors on the dynamics of energetic particles in the coronal arches.

Hubble Space Telescope Scattered-light Imaging and Modeling of the Edge-on Protoplanetary Disk ESO-Hα 569

NASA Astrophysics Data System (ADS)

Wolff, Schuyler G.; Perrin, Marshall D.; Stapelfeldt, Karl; Duchêne, Gaspard; Ménard, Francois; Padgett, Deborah; Pinte, Christophe; Pueyo, Laurent; Fischer, William J.

2017-12-01

We present new Hubble Space Telescope (HST) Advanced Camera for Surveys observations and detailed models for a recently discovered edge-on protoplanetary disk around ESO-Hα 569 (a low-mass T Tauri star in the Cha I star-forming region). Using radiative transfer models, we probe the distribution of the grains and overall shape of the disk (inclination, scale height, dust mass, flaring exponent, and surface/volume density exponent) by model fitting to multiwavelength (F606W and F814W) HST observations together with a literature-compiled spectral energy distribution. A new tool set was developed for finding optimal fits of MCFOST radiative transfer models using the MCMC code emcee to efficiently explore the high-dimensional parameter space. It is able to self-consistently and simultaneously fit a wide variety of observables in order to place constraints on the physical properties of a given disk, while also rigorously assessing the uncertainties in those derived properties. We confirm that ESO-Hα 569 is an optically thick nearly edge-on protoplanetary disk. The shape of the disk is well-described by a flared disk model with an exponentially tapered outer edge, consistent with models previously advocated on theoretical grounds and supported by millimeter interferometry. The scattered-light images and spectral energy distribution are best fit by an unusually high total disk mass (gas+dust assuming a ratio of 100:1) with a disk-to-star mass ratio of 0.16.

THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES OBSERVED WITH AIA/SDO: FRACTAL DIFFUSION, SUB-DIFFUSION, OR LOGISTIC GROWTH?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aschwanden, Markus J., E-mail: aschwanden@lmsal.com

2012-09-20

We explore the spatio-temporal evolution of solar flares by fitting a radial expansion model r(t) that consists of an exponentially growing acceleration phase, followed by a deceleration phase that is parameterized by the generalized diffusion function r(t){proportional_to}{kappa}(t - t{sub 1}){sup {beta}/2}, which includes the logistic growth limit ({beta} = 0), sub-diffusion ({beta} = 0-1), classical diffusion ({beta} = 1), super-diffusion ({beta} = 1-2), and the linear expansion limit ({beta} = 2). We analyze all M- and X-class flares observed with Geostationary Operational Environmental Satellite and Atmospheric Imaging Assembly/Solar Dynamics Observatory (SDO) during the first two years of the SDO mission,more » amounting to 155 events. We find that most flares operate in the sub-diffusive regime ({beta} = 0.53 {+-} 0.27), which we interpret in terms of anisotropic chain reactions of intermittent magnetic reconnection episodes in a low plasma-{beta} corona. We find a mean propagation speed of v = 15 {+-} 12 km s{sup -1}, with maximum speeds of v{sub max} = 80 {+-} 85 km s{sup -1} per flare, which is substantially slower than the sonic speeds expected for thermal diffusion of flare plasmas. The diffusive characteristics established here (for the first time for solar flares) is consistent with the fractal-diffusive self-organized criticality model, which predicted diffusive transport merely based on cellular automaton simulations.« less

Influence of orbital-maneuvering-system fairings and rudder flare on the transonic aerodynamic characteristics of a space shuttle orbiter

NASA Technical Reports Server (NTRS)

Ellison, J. C.

1975-01-01

An investigation was conducted in the Langley 8-foot transonic pressure tunnel to determine the influence of orbital-maneuvering-system fairings and a flared rudder on the aerodynamic characteristics of a space shuttle-orbiter configuration. Tests were made at Mach numbers from 0.4 to 1.2, at angles of attack from -1 deg to 24 deg, at angles of sideslip of 0 deg and 5 deg, and at a Reynolds number, based on model length, of 4 million. The model with the orbital-maneuvering-system fairings had a minimum untrimmed lift-drag ratio from 7.4 to 3.4 at Mach numbers from 0.4 to 1.2 and a maximum trimmed lift-drag ratio of about 3.55 at Mach 0.8 with the rudder flared 30 deg. The directional stability was increased at Mach 0.8 and 1.2 by addition of the orbital-maneuvering-system fairings and at Mach 1.2 by flaring the rudder.

Possible biophysical mechanism of the effect of the solar activity on the human central nervous system

NASA Astrophysics Data System (ADS)

Mikhailova, G. A.; Mikhailov, Y. M.

Numerous studies, beginning with Tchizhevsky's works, demonstrated the undeniable effect of the solar activity on the human body. A possible geophysical mechanism of the effect of the solar activity on the human body was proposed by Vladimirsky. In this mechanism solar disturbances (powerful chromospheres flares) cause "magnetosphere and plasmasphere disturbances on the Earth (sudden magnetic storms), which are accompanied by a change in the spectrum of the electromagnetic field on the Earth's surface in the extremely low frequency band. In its turn, this brings about shifts in the phisiological indices of the human body". In this model, the human body is regarded as a self-oscillating system affected by external geophysical factors. We also adhere to the main principles of this model but refine the part of this model that describes the change in the spectrum of the electromagnetic field on the Earth's surface in the extremely low frequency band. Unlike Vladimirsky model, we regard the human is not as a self-oscillating system but as one of two coupled oscillating system with discrete resonance frequencies in the human-habitat ensemble. Solar processes and their induced changes in one of the two coupled oscillating systems, specifically, the habitat play the role of an external force. Such an approach is based on the fact that the brain rhythms have the following definite frequencies: the alpha rhythm, 8-13 Hz; the beta rhythm, 14-30 Hz; the gamma rhythm, above 30 Hz; the delta rhythm, 1.5-3 Hz; and the theta rhythm, 4-7 Hz. On the other hand, the natural electromagnetic field on the Earth's surface in the extremely low frequency band also has a quite distinct resonance distribution. There are so-called Schuman resonances of the cavity formed by the Earth's surface and the lower boundary of the ionosphere (the D and E layers) at f1=10.6; f2=18.3; f3=25.9; f4=33.5; f5=41.1 Hz. These resonance frequencies are variable and most sensitive to variations of the parameters of the lower ionosphere. Solar flares cause magnetic and ionosphere storms, which lead up to additional ionisation in the D and E layers and lowering of the upper boundary of cavity. That decreases the resonance frequencies of the cavity. Thus, the state of the human habitat proves to be dependent on the solar activity through variations of the parameters of the lower ionosphere, which govern variations of the Schuman resonances. These variations we suppose to measure on "Kompass-2" and "Vulcan" satellites.

Search for Gravitational Wave Bursts from Six Magnetars

NASA Astrophysics Data System (ADS)

Abadie, J.; Abbott, B. P.; Abbott, R.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.; Allen, B.; Allen, G. S.; Amador Ceron, E.; Amariutei, D.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Antonucci, F.; Arai, K.; Arain, M. A.; Araya, M. C.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Barker, D.; Barnum, S.; Barone, F.; Barr, B.; Barriga, P.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Basti, A.; Bauchrowitz, J.; Bauer, Th. S.; Behnke, B.; Beker, M. G.; Bell, A. S.; Belletoile, A.; Belopolski, I.; Benacquista, M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birindelli, S.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bouhou, B.; Boyle, M.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brummit, A.; Budzyński, R.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet-Castell, J.; Burmeister, O.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cain, J.; Calloni, E.; Camp, J. B.; Campagna, E.; Campsie, P.; Cannizzo, J.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C.; Carbognani, F.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chaibi, O.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chassande-Mottin, E.; Chelkowski, S.; Chen, Y.; Chincarini, A.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Chung, S.; Clara, F.; Clark, D.; Clark, J.; Clayton, J. H.; Cleva, F.; Coccia, E.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, R.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M.; Coulon, J.-P.; Coward, D. M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; D'Antonio, S.; Danzmann, K.; Das, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; del Prete, M.; Dent, T.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Emilio, M. Di Paolo; Di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Dorsher, S.; Douglas, E. S. D.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Engel, R.; Etzel, T.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Flaminio, R.; Flanigan, M.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Galimberti, M.; Gammaitoni, L.; Garcia, J.; Garofoli, J. A.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Genin, E.; Gennai, A.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gill, C.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Greverie, C.; Grosso, R.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gupta, R.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Hayler, T.; Heefner, J.; Heitmann, H.; Hello, P.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Herrera, V.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Hong, T.; Hooper, S.; Hosken, D. J.; Hough, J.; Howell, E. J.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Jaranowski, P.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J. B.; Katsavounidis, E.; Katzman, W.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Kelner, M.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, H.; Kim, N.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, R.; Kwee, P.; Landry, M.; Lantz, B.; Lastzka, N.; Lazzarini, A.; Leaci, P.; Leong, J.; Leonor, I.; Leroy, N.; Letendre, N.; Li, J.; Li, T. G. F.; Liguori, N.; Lindquist, P. E.; Lockerbie, N. A.; Lodhia, D.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lu, P.; Luan, J.; Lubiński, M.; Lück, H.; Lundgren, A. P.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marandi, A.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McKechan, D. J. A.; Meadors, G.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Mercer, R. A.; Merill, L.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mino, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Moesta, P.; Mohan, M.; Mohanty, S. D.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morgia, A.; Mosca, S.; Moscatelli, V.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murray, P. G.; Nash, T.; Nawrodt, R.; Nelson, J.; Neri, I.; Newton, G.; Nishida, E.; Nishizawa, A.; Nocera, F.; Nolting, D.; Ochsner, E.; O'Dell, J.; Ogin, G. H.; Oldenburg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Papa, M. A.; Parameswaran, A.; Pardi, S.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Pathak, D.; Pedraza, M.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Persichetti, G.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Podkaminer, J.; Poggiani, R.; Pöld, J.; Postiglione, F.; Prato, M.; Predoi, V.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Ramet, C. R.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Redwine, K.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, P.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rolland, L.; Rollins, J.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sakata, S.; Sakosky, M.; Salemi, F.; Salit, M.; Sammut, L.; Sancho de la Jordana, L.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Saraf, S.; Sassolas, B.; Sathyaprakash, B. S.; Sato, S.; Satterthwaite, M.; Saulson, P. R.; Savage, R.; Schilling, R.; Schlamminger, S.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shihan Weerathunga, T.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Smith, R.; Somiya, K.; Sorazu, B.; Soto, J.; Speirits, F. C.; Sperandio, L.; Stefszky, M.; Stein, A. J.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szokoly, G. P.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Trias, M.; Tseng, K.; Turner, L.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vaishnav, B.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vocca, H.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Wanner, A.; Ward, R. L.; Was, M.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, H. R.; Williams, L.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yu, P.; Yvert, M.; Zanolin, M.; Zhang, L.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration; Aptekar, R. L.; Boynton, W. V.; Briggs, M. S.; Cline, T. L.; Connaughton, V.; Frederiks, D. D.; Gehrels, N.; Goldsten, J. O.; Golovin, D.; van der Horst, A. J.; Hurley, K. C.; Kaneko, Y.; von Kienlin, A.; Kouveliotou, C.; Krimm, H. A.; Lin, L.; Mitrofanov, I.; Ohno, M.; Pal'shin, V. D.; Rau, A.; Sanin, A.; Tashiro, M. S.; Terada, Y.; Yamaoka, K.

2011-06-01

Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are thought to be magnetars: neutron stars powered by extreme magnetic fields. These rare objects are characterized by repeated and sometimes spectacular gamma-ray bursts. The burst mechanism might involve crustal fractures and excitation of non-radial modes which would emit gravitational waves (GWs). We present the results of a search for GW bursts from six galactic magnetars that is sensitive to neutron star f-modes, thought to be the most efficient GW emitting oscillatory modes in compact stars. One of them, SGR 0501+4516, is likely ~1 kpc from Earth, an order of magnitude closer than magnetars targeted in previous GW searches. A second, AXP 1E 1547.0-5408, gave a burst with an estimated isotropic energy >1044 erg which is comparable to the giant flares. We find no evidence of GWs associated with a sample of 1279 electromagnetic triggers from six magnetars occurring between 2006 November and 2009 June, in GW data from the LIGO, Virgo, and GEO600 detectors. Our lowest model-dependent GW emission energy upper limits for band- and time-limited white noise bursts in the detector sensitive band, and for f-mode ringdowns (at 1090 Hz), are 3.0 × 1044 d 2 1 erg and 1.4 × 1047 d 2 1 erg, respectively, where d_{1} = \\frac{d_{{0501}}}{1\\,{kpc}} and d 0501 is the distance to SGR 0501+4516. These limits on GW emission from f-modes are an order of magnitude lower than any previous, and approach the range of electromagnetic energies seen in SGR giant flares for the first time.

Consequences of the Breakout Model for Particle Acceleration in CMEs and Flares

NASA Technical Reports Server (NTRS)

Antiochos, S. K.; Karpen, J. T.; DeVore, C. R.

2011-01-01

The largest and most efficient particle accelerators in the solar system are the giant events consisting of a fast coronal mass ejection (CME) and an intense X-class solar flare. Both flares and CMEs can produce l0(exp 32) ergs or more in nonthermal particles. Two general processes are believed to be responsible: particle acceleration at the strong shock ahead of the CME, and reconnection-driven acceleration in the flare current sheet. Although shock acceleration is relatively well understood, the mechanism by which flare reconnection produces nonthermal particles is still an issue of great debate. We address the question of CME/flare particle acceleration in the context of the breakout model using 2.5D MHD simulations with adaptive mesh refinement (AMR). The AMR capability allows us to achieve ultra-high numerical resolution and, thereby, determine the detailed structure and dynamics of the flare reconnection region. Furthermore, we employ newly developed numerical analysis tools for identifying and characterizing magnetic nulls, so that we can quantify accurately the number and location of magnetic islands during reconnection. Our calculations show that flare reconnection is dominated by the formation of magnetic islands. In agreement with many other studies, we find that the number of islands scales with the effective Lundquist number. This result supports the recent work by Drake and co-workers that postulates particle acceleration by magnetic islands. On the other hand, our calculations also show that the flare reconnection region is populated by numerous shocks and other indicators of strong turbulence, which can also accelerate particles. We discuss the implications of our calculations for the flare particle acceleration mechanism and for observational tests of the models.

A Phenomenological Two-Ribbon Model for Spatially Unresolved Observations of Stellar Flares

NASA Astrophysics Data System (ADS)

Kowalski, Adam

2018-06-01

Solar flares and flares that occur in much more magnetically active stars share some striking properties, such as the observed Neupert effect. However, stellar flares with the most impressive multi-wavelength data sets are typically much more energetic than solar flares, thus making robust connections difficult to establish. Whereas solar data have the advantage of high spatial resolution providing critical information about the development of flare ribbons, the major advantage of stellar flare data is the readily available broad-wavelength coverage of the white-light radiation and the Balmer jump spectral region. Due to the lack of direct spatial resolution for stellar flares and rarely coverage of the Balmer jump region for solar flares, it is not clear how to make a direct comparison. I will present a new method for modeling stellar flares based on high spatial resolution information of solar flare two-ribbon development for comparisons of the physics of their observed phenomena, such as the red-wing asymmetries in chromospheric lines and the white-light continuum radiation. The new modeling method combines aspects of "multi-thread" modeling and 1D radiative-hydrodynamic modeling. Our algorithm is important for interpreting the impulsive phase of superflares in young G dwarfs in Kepler and understanding how hour-long decay timescales are attained in the gradual phase of some very energetic stellar flares.

A survey of stellar X-ray flares from the XMM-Newton serendipitous source catalogue: HIPPARCOS-Tycho cool stars

NASA Astrophysics Data System (ADS)

Pye, J. P.; Rosen, S.; Fyfe, D.; Schröder, A. C.

2015-09-01

Context. The X-ray emission from flares on cool (i.e. spectral-type F-M) stars is indicative of very energetic, transient phenomena, associated with energy release via magnetic reconnection. Aims: We present a uniform, large-scale survey of X-ray flare emission. The XMM-Newton Serendipitous Source Catalogue and its associated data products provide an excellent basis for a comprehensive and sensitive survey of stellar flares - both from targeted active stars and from those observed serendipitously in the half-degree diameter field-of-view of each observation. Methods: The 2XMM Catalogue and the associated time-series ("light-curve") data products have been used as the basis for a survey of X-ray flares from cool stars in the Hipparcos-Tycho-2 catalogue. In addition, we have generated and analysed spectrally-resolved (i.e. hardness-ratio), X-ray light-curves. Where available, we have compared XMM OM UV/optical data with the X-ray light-curves. Results: Our sample contains ~130 flares with well-observed profiles; they originate from ~70 stars. The flares range in duration from ~103 to ~104 s, have peak X-ray fluxes from ~10-13 to ~10-11erg cm-2 s-1, peak X-ray luminosities from ~1029 to ~1032erg s-1, and X-ray energy output from ~1032 to ~1035 erg. Most of the ~30 serendipitously-observed stars have little previously reported information. The hardness-ratio plots clearly illustrate the spectral (and hence inferred temperature) variations characteristic of many flares, and provide an easily accessible overview of the data. We present flare frequency distributions from both target and serendipitous observations. The latter provide an unbiased (with respect to stellar activity) study of flare energetics; in addition, they allow us to predict numbers of stellar flares that may be detected in future X-ray wide-field surveys. The serendipitous sample demonstrates the need for care when calculating flaring rates, especially when normalising the number of flares to a total exposure time, where it is important to consider both the stars seen to flare and those from which variability was not detected (i.e. measured as non-variable), since in our survey, the latter outnumber the former by more than a factor ten. The serendipitous variable and "non-variable" stars appear very similar in terms of the distributions of general properties such as quiescent X-ray luminosity; from the available data, it is unclear whether the distinction by flaring is due to an additional, intrinsic property such as intra-system interactions in a close binary system, or is simply the result of limited observations and detection thresholds on a random flaring process, with no real difference between the two samples, or may be a combination of these effects. However, the number of detected flares compared with the number of stars not seen to vary is broadly consistent with estimates based on Poisson statistics. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.Appendices are available in electronic form at http://www.aanda.orgTables C.1 and C.2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/581/A28

CAN A NANOFLARE MODEL OF EXTREME-ULTRAVIOLET IRRADIANCES DESCRIBE THE HEATING OF THE SOLAR CORONA?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tajfirouze, E.; Safari, H.

2012-01-10

Nanoflares, the basic units of impulsive energy release, may produce much of the solar background emission. Extrapolation of the energy frequency distribution of observed microflares, which follows a power law to lower energies, can give an estimation of the importance of nanoflares for heating the solar corona. If the power-law index is greater than 2, then the nanoflare contribution is dominant. We model a time series of extreme-ultraviolet emission radiance as random flares with a power-law exponent of the flare event distribution. The model is based on three key parameters: the flare rate, the flare duration, and the power-law exponentmore » of the flare intensity frequency distribution. We use this model to simulate emission line radiance detected in 171 A, observed by Solar Terrestrial Relation Observatory/Extreme-Ultraviolet Imager and Solar Dynamics Observatory/Atmospheric Imaging Assembly. The observed light curves are matched with simulated light curves using an Artificial Neural Network, and the parameter values are determined across the active region, quiet Sun, and coronal hole. The damping rate of nanoflares is compared with the radiative losses cooling time. The effect of background emission, data cadence, and network sensitivity on the key parameters of the model is studied. Most of the observed light curves have a power-law exponent, {alpha}, greater than the critical value 2. At these sites, nanoflare heating could be significant.« less

FLARES ON A-TYPE STARS: EVIDENCE FOR HEATING OF SOLAR CORONA BY NANOFLARES?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Švanda, Michal; Karlický, Marian, E-mail: michal@astronomie.cz

We analyzed the occurrence rates of flares on stars of spectral types K, G, F, and A, observed by Kepler . We found that the histogram of occurrence frequencies of stellar flares is systematically shifted toward a high-energy tail for A-type stars compared to stars of cooler spectral types. We extrapolated the fitted power laws toward flares with smaller energies (nanoflares) and made estimates for total energy flux to stellar atmospheres by flares. We found that, for A-type stars, the total energy flux density was at least four-times smaller than for G stars. We speculate that this deficit in energymore » supply may explain the lack of hot coronae on A-type stars. Our results indicate the importance of nanoflares for heating and formation of the solar corona.« less

The Evolution of Quasi-separatrix Layer in Two Solar Eruptive Events

NASA Astrophysics Data System (ADS)

Kang, K. F.; Yan, X. L.; Xu, Z.; Wu, N.; Lin, J.

2017-05-01

Quasi-separatrix layer, also called QSL, is a region where magnetic connectivity changes drastically and mostly well coincides with the location of flare ribbons in observations. The research on the relation between this topological structure and 3-dimensional magnetic reconnection, and solar flares has attracted more and more attention. In this paper, using the theory of QSL we investigate a C5.7 classical two-ribbon solar flare (event 1) which occurred at AR11384 on 2011 December 26 and an M6.5 solar flare (event 2) which occurred at AR12371 on 2015 June 22, respectively. Combining the multi-wavelength data of AIA (Atmospheric Imaging Assembly) and vector magnetogrames of HMI (Helioseismic and Magnetic Imager) onboard SDO (Solar Dynamics Observatory), we extrapolate the coronal magnetic field using the PF (Potential Field) model and NLFFF (Nonlinear Force Free Field) model, and calculate the evolution of the AR (Active Region) magnetic free energy first. Next, we calculate the slgQ maps of Q factor (magnetic squashing factor) at different heights away from solar photosphere with the extrapolation results of PF and NLFFF in order to decide the location of QSL. Then, we investigate the evolution relation between QSL at different heights away from solar photosphere and flaring brightening at the same layers. Finally, we study the multi-wavelength evolution features of the 2 flares. And, we calculate the observational slipping running speeds of event 2 in 304 Å and 335 Å, which are 4.6 km s-1 and 6.3 km s-1, respectively. We find that the location of QSL calculated in chromosphere and corona is in good agreement with the location of flare ribbons at the same height, and the QSL at different layers has almost the same evolutionary behavior in time with the flaring brightening of the corresponding layer, which highlights the role of QSL in the research of 3D magnetic reconnection and solar flare, and we suggest that the flare may be triggered by the QSL reconnection. We also suggest that QSL is very important for us to research the essential connection between 3D magnetic reconnection and 2D magnetic reconnection.

Flare Prediction Using Photospheric and Coronal Image Data

NASA Astrophysics Data System (ADS)

Jonas, Eric; Bobra, Monica; Shankar, Vaishaal; Todd Hoeksema, J.; Recht, Benjamin

2018-03-01

The precise physical process that triggers solar flares is not currently understood. Here we attempt to capture the signature of this mechanism in solar-image data of various wavelengths and use these signatures to predict flaring activity. We do this by developing an algorithm that i) automatically generates features in 5.5 TB of image data taken by the Solar Dynamics Observatory of the solar photosphere, chromosphere, transition region, and corona during the time period between May 2010 and May 2014, ii) combines these features with other features based on flaring history and a physical understanding of putative flaring processes, and iii) classifies these features to predict whether a solar active region will flare within a time period of T hours, where T = 2 and 24. Such an approach may be useful since, at the present time, there are no physical models of flares available for real-time prediction. We find that when optimizing for the True Skill Score (TSS), photospheric vector-magnetic-field data combined with flaring history yields the best performance, and when optimizing for the area under the precision-recall curve, all of the data are helpful. Our model performance yields a TSS of 0.84 ±0.03 and 0.81 ±0.03 in the T = 2- and 24-hour cases, respectively, and a value of 0.13 ±0.07 and 0.43 ±0.08 for the area under the precision-recall curve in the T=2- and 24-hour cases, respectively. These relatively high scores are competitive with previous attempts at solar prediction, but our different methodology and extreme care in task design and experimental setup provide an independent confirmation of these results. Given the similar values of algorithm performance across various types of models reported in the literature, we conclude that we can expect a certain baseline predictive capacity using these data. We believe that this is the first attempt to predict solar flares using photospheric vector-magnetic field data as well as multiple wavelengths of image data from the chromosphere, transition region, and corona, and it points the way towards greater data integration across diverse sources in future work.

Models of the Solar Atmospheric Response to Flare Heating

NASA Technical Reports Server (NTRS)

Allred, Joel

2011-01-01

I will present models of the solar atmospheric response to flare heating. The models solve the equations of non-LTE radiation hydrodynamics with an electron beam added as a flare energy source term. Radiative transfer is solved in detail for many important optically thick hydrogen and helium transitions and numerous optically thin EUV lines making the models ideally suited to study the emission that is produced during flares. I will pay special attention to understanding key EUV lines as well the mechanism for white light production. I will also present preliminary results of how the model solar atmosphere responds to Fletcher & Hudson type flare heating. I will compare this with the results from flare simulations using the standard thick target model.

The disc-jet symbiosis emerges: modelling the emission of Sagittarius A* with electron thermodynamics

NASA Astrophysics Data System (ADS)

Ressler, S. M.; Tchekhovskoy, A.; Quataert, E.; Gammie, C. F.

2017-05-01

We calculate the radiative properties of Sagittarius A* - spectral energy distribution, variability and radio-infrared images - using the first 3D, physically motivated black hole accretion models that directly evolve the electron thermodynamics in general relativistic MHD simulations. These models reproduce the coupled disc-jet structure for the emission favoured by previous phenomenological analytic and numerical works. More specifically, we find that the low frequency radio emission is dominated by emission from a polar outflow while the emission above 100 GHz is dominated by the inner region of the accretion disc. The latter produces time variable near-infrared (NIR) and X-ray emission, with frequent flaring events (including IR flares without corresponding X-ray flares and IR flares with weak X-ray flares). The photon ring is clearly visible at 230 GHz and 2 μm, which is encouraging for future horizon-scale observations. We also show that anisotropic electron thermal conduction along magnetic field lines has a negligible effect on the radiative properties of our model. We conclude by noting limitations of our current generation of first-principles models, particularly that the outflow is closer to adiabatic than isothermal and thus underpredicts the low frequency radio emission.

Statistical Study of Magnetic Nonpotential Measures in Confined and Eruptive Flares

NASA Astrophysics Data System (ADS)

Vasantharaju, N.; Vemareddy, P.; Ravindra, B.; Doddamani, V. H.

2018-06-01

Using Solar Dynamics Observatory/Helioseismic and Magnetic Imager vector magnetic field observations, we studied the relation between the degree of magnetic non-potentiality with the observed flare/coronal mass ejection (CME) in active regions (ARs). From a sample of 77 flare/CME cases, we found in general that the degree of non-potentiality is positively correlated with the flare strength and the associated CME speed. Since the magnetic flux in the flare-ribbon area is more related to the reconnection, we trace the strong gradient polarity inversion line (SGPIL) and Schrijver’s R value manually along the flare-ribbon extent. Manually detected SGPIL length and R values show higher correlation with the flare strength and CME speed than automatically traced values without flare-ribbon information. This highlights the difficulty of predicting the flare strength and CME speed a priori from the pre-flare magnetograms used in flare prediction models. Although the total potential magnetic energy proxies show a weak positive correlation, the decrease in free energy exhibits a higher correlation (0.56) with the flare strength and CME speed. Moreover, eruptive flares have thresholds of SGPIL length (31 Mm), R value (1.6 × 1019 Mx), and free energy decrease (2 × 1031 erg) compared to confined flares. In 90% of eruptive flares, the decay-index curve is steeper, reaching {n}crit}=1.5 within 42 Mm, whereas it is beyond this value in >70% of confined flares. While indicating improved statistics in the predictive capability of AR eruptive behavior with flare-ribbon information, our study provides threshold magnetic properties for a flare to be eruptive.

An X-ray flare from 47 Cas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pandey, Jeewan C.; Karmakar, Subhajeet, E-mail: jeewan@aries.res.in

2015-02-01

Using XMM-Newton observations, we investigate properties of a flare from the very active but poorly known stellar system 47 Cas. The luminosity at the peak of the flare is found to be 3.54 × 10{sup 30} erg s{sup −1}, which is ∼2 times higher than that at a quiescent state. The quiescent state corona of 47 Cas can be represented by two temperature plasma: 3.7 and 11.0 MK. The time-resolved X-ray spectroscopy of the flare show the variable nature of the temperature, the emission measure, and the abundance. The maximum temperature during the flare is derived as 72.8 MK. Wemore » infer the length of a flaring loop to be 3.3 × 10{sup 10} cm using a hydrodynamic loop model. Using the RGS spectra, the density during the flare is estimated as 4.0 × 10{sup 10} cm{sup −3}. The loop scaling laws are also applied when deriving physical parameters of the flaring plasma.« less

Simultaneous Extreme-Ultraviolet Explorer and Optical Observations of Ad Leonis: Evidence for Large Coronal Loops and the Neupert Effect in Stellar Flares

NASA Technical Reports Server (NTRS)

Hawley, Suzanne L.; Fisher, George H.; Simon, Theodore; Cully, Scott L.; Deustua, Susana E.; Jablonski, Marek; Johns-Krull, Christopher; Pettersen, Bjorn R.; Smith, Verne; Spiesman, William J.;

Study of Two Successive Three-ribbon Solar Flares on 2012 July 6

NASA Astrophysics Data System (ADS)

Wang, Haimin; Liu, Chang; Deng, Na; Zeng, Zhicheng; Xu, Yan; Jing, Ju; Cao, Wenda

2014-01-01

This Letter reports two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.''1 resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing "fish-bone-like" morphology evidenced by both Hα images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Hα apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections.

Study of Two Successive Three-ribbon Solar Flares Using BBSO/NST Observations

NASA Astrophysics Data System (ADS)

Wang, Haimin; Liu, Chang; Deng, Na; Zeng, Zhicheng; Xu, Yan; Jing, Ju; Cao, Wenda

2014-06-01

We studied two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.1 arcsec resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing "fish-bone-like" morphology evidenced by both Halpha images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Halpha apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections.

Flare parameters inferred from a 3D loop model data base

NASA Astrophysics Data System (ADS)

Cuambe, Valente A.; Costa, J. E. R.; Simões, P. J. A.

2018-06-01

We developed a data base of pre-calculated flare images and spectra exploring a set of parameters which describe the physical characteristics of coronal loops and accelerated electron distribution. Due to the large number of parameters involved in describing the geometry and the flaring atmosphere in the model used, we built a large data base of models (˜250 000) to facilitate the flare analysis. The geometry and characteristics of non-thermal electrons are defined on a discrete grid with spatial resolution greater than 4 arcsec. The data base was constructed based on general properties of known solar flares and convolved with instrumental resolution to replicate the observations from the Nobeyama radio polarimeter spectra and Nobeyama radioheliograph (NoRH) brightness maps. Observed spectra and brightness distribution maps are easily compared with the modelled spectra and images in the data base, indicating a possible range of solutions. The parameter search efficiency in this finite data base is discussed. 8 out of 10 parameters analysed for 1000 simulated flare searches were recovered with a relative error of less than 20 per cent on average. In addition, from the analysis of the observed correlation between NoRH flare sizes and intensities at 17 GHz, some statistical properties were derived. From these statistics, the energy spectral index was found to be δ ˜ 3, with non-thermal electron densities showing a peak distribution ⪅107 cm-3, and Bphotosphere ⪆ 2000 G. Some bias for larger loops with heights as great as ˜2.6 × 109 cm, and looptop events were noted. An excellent match of the spectrum and the brightness distribution at 17 and 34 GHz of the 2002 May 31 flare is presented as well.

The Dependence of Solar Flare Limb Darkening on Emission Peak Formation Temperature

NASA Astrophysics Data System (ADS)

Thiemann, Edward; Epp, Luke; Eparvier, Francis; Chamberlin, Phillip C.

2017-08-01

Solar limb effects are local brightening or darkening of an emission that depend on where in the Sun's atmosphere it forms. Near the solar limb, optically thick (thin) emissions will darken (brighten) as the column of absorbers (emitters) along the line-of-sight increases. Note that in limb brightening, emission sources are re-arranged whereas in limb darkening they are obscured. Thus, only limb darkening is expected to occur in disk integrated observations. Limb darkening also results in center-to-limb variations of disk-integrated solar flare spectra, with important consequences for how planetary atmospheres are affected by flares. Flares are typically characterized by their flux in the optically thin 0.1-0.8 nm band measured by the X-ray Sensor (XRS) on board the Geostationary Operational Environmental Satellite (GOES). On the other hand, Extreme Ultraviolet (EUV) line emissions can limb darken because they are sensitive to resonant scattering, resulting in a flare's location on the solar disk controlling the amount of ionizing radiation that reaches a planet. For example, an X-class flare originating from disk center may significantly heat a planet's thermosphere, whereas the same flare originating near the limb may have no effect because much of the effective emissions are scattered in the solar corona.To advance the relatively poor understanding of flare limb darkening, we use over 300 M-class or larger flares observed by the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO) to characterize limb darkening as a function of emission peak formation temperature, Tf. For hot coronal emissions (Tf>2 MK), these results show a linear relationship between the degree of limb darkening and Tf where lines with Tf=2 MK darken approximately 7 times more than lines with Tf=16 MK. Because the extent of limb darkening is dependent on the height of the source plasma, we use simple Beer-Lambert radiative transfer analysis to interpret these results and characterize the average thermal structure of the flares considered. As such, these results can be used to constrain both empirical flare irradiance models and more sophisticated flare loop hydrodynamic models.

NuSTAR Detection of High-Energy X-Ray Emission and Rapid Variability from Sagittarius A(star) Flares

NASA Technical Reports Server (NTRS)

Barriere, Nicolas M.; Tomsick, John A.; Baganoff, Frederick K.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Dexter, Jason; Grefenstette, Brian; Hailey, Charles J.; Zhang, William W.

2014-01-01

Sagittarius A(star) harbors the supermassive black hole that lies at the dynamical center of our Galaxy. Sagittarius A(star) spends most of its time in a low luminosity emission state but flares frequently in the infrared and X-ray, increasing up to a few hundred fold in brightness for up to a few hours at a time. The physical processes giving rise to the X-ray flares are uncertain. Here we report the detection with the NuSTAR observatory in Summer and Fall 2012 of four low to medium amplitude X-ray flares to energies up to 79 keV. For the first time, we clearly see that the power-law spectrum of Sagittarius A(star) X-ray flares extends to high energy, with no evidence for a cut off. Although the photon index of the absorbed power-law fits are in agreement with past observations, we find a difference between the photon index of two of the flares (significant at the 95% confidence level). The spectra of the two brightest flares (approx. 55 times quiescence in the 2- 10 keV band) are compared to simple physical models in an attempt to identify the main X-ray emission mechanism, but the data do not allow us to significantly discriminate between them. However, we confirm the previous finding that the parameters obtained with synchrotron models are, for the X-ray emission, physically more reasonable than those obtained with inverse-Compton models. One flare exhibits large and rapid (less than 100 s) variability, which, considering the total energy radiated, constrains the location of the flaring region to be within approx. 10 Schwarzschild radii of the black hole.

Broadband radio jet emission and variability of γ-ray blazars

NASA Astrophysics Data System (ADS)

Nestoras, Ioannis

2015-07-01

AGN (Active Galactic Nuclei) and in particular their subclass blazars, are among the most energetic objects observed in the universe, featuring extreme phenomenological characteristics such as rapid broadband flux density and polarization variability, fast super--luminal motion, high degree of polarization and a broadband, double-humped spectral energy distribution (SED). The details of the emission processes and violent variability of blazars are still poorly understood. Variability studies give important clues about the size, structure, physics and dynamics of the emitting region making AGN/blazar monitoring programs of uttermost importance in providing the necessary constraints for understanding the origin of energy production. In this framework the F-gamma program was initiated, monitoring monthly 60 fermi detected AGN/blazars at 12 frequencies between 2.6 and 345GHz since 2007. For the thesis in hand observations and data analysis were performed within the realms of the F-gamma program, using the Effelsberg (EB) 100m and Pico Veleta (PV) 30m telescopes at 10 frequency bands ranging from 2.64 to 142GHz. The cm to short-mm variability/spectral characteristics are monitored for a sample of 59 sources for a period of five years enabling for the first time a detailed study of the observed flaring activity in both the light curve and spectral domains for such a large number of sources and such high cadence. Also the observing systems and methods are introduced as well as the data reduction techniques. The thesis at hand is structured as follows: Chapter 3 presents the reduction methods and post measurement corrections applied to the data such as pointing offsets, gain--elevation and sensitivity corrections as well as specific corrections applied for each of the Effelsberg and Pico Veleta observing systems respectively. Chapter 4 presents the analysis tools and methods that were used such as: variability characteristics, flare amplitudes with a new method for estimating the intrinsic standard deviation, flare time scales using Structure Function analysis, spectral indices and spectral peak estimations. Chapter 5 presents the results of the analysis performed upon the five year light curves. The significance of variability through a x^2 test is estimated as well as the flare amplitudes using the intrinsic variability of the light curves along with a new proposed k--index. The introduction of the k--index enables the characterization of the observed variability amplitudes across frequency, thus permitting us to limit the parameter space of various physical models. Also flare time scales, brightness temperatures and Doppler factors are reported. Chapter 6 presents the corresponding analysis in the spectral domain, including results for spectral indices and an S_max - v_max analysis. By determining the spectral peak of every spectra for a selected number of sources, it is possible to track the evolution of the flaring activity in the S_max - v_max plane, enabling us to discriminate between different underlying physical mechanisms that are in action. Finally Chapter 7 includes the overall discussion and a summary of results obtained.

A global gas flaring black carbon emission rate dataset from 1994 to 2012

PubMed Central

Huang, Kan; Fu, Joshua S.

2016-01-01

Global flaring of associated petroleum gas is a potential emission source of particulate matters (PM) and could be notable in some specific regions that are in urgent need of mitigation. PM emitted from gas flaring is mainly in the form of black carbon (BC), which is a strong short-lived climate forcer. However, BC from gas flaring has been neglected in most global/regional emission inventories and is rarely considered in climate modeling. Here we present a global gas flaring BC emission rate dataset for the period 1994–2012 in a machine-readable format. We develop a region-dependent gas flaring BC emission factor database based on the chemical compositions of associated petroleum gas at various oil fields. Gas flaring BC emission rates are estimated using this emission factor database and flaring volumes retrieved from satellite imagery. Evaluation using a chemical transport model suggests that consideration of gas flaring emissions can improve model performance. This dataset will benefit and inform a broad range of research topics, e.g., carbon budget, air quality/climate modeling, and environmental/human exposure. PMID:27874852

A global gas flaring black carbon emission rate dataset from 1994 to 2012

NASA Astrophysics Data System (ADS)

Huang, Kan; Fu, Joshua S.

2016-11-01

Global flaring of associated petroleum gas is a potential emission source of particulate matters (PM) and could be notable in some specific regions that are in urgent need of mitigation. PM emitted from gas flaring is mainly in the form of black carbon (BC), which is a strong short-lived climate forcer. However, BC from gas flaring has been neglected in most global/regional emission inventories and is rarely considered in climate modeling. Here we present a global gas flaring BC emission rate dataset for the period 1994-2012 in a machine-readable format. We develop a region-dependent gas flaring BC emission factor database based on the chemical compositions of associated petroleum gas at various oil fields. Gas flaring BC emission rates are estimated using this emission factor database and flaring volumes retrieved from satellite imagery. Evaluation using a chemical transport model suggests that consideration of gas flaring emissions can improve model performance. This dataset will benefit and inform a broad range of research topics, e.g., carbon budget, air quality/climate modeling, and environmental/human exposure.

Implications of X-Ray Observations for Electron Acceleration and Propagation in Solar Flares

NASA Technical Reports Server (NTRS)

Holman, G. D.; Aschwanden, M. J.; Aurass, H.; Battaglia, M.; Grigis, P. C.; Kontar, E. P.; Liu, W.; Saint-Hilaire, P.; Zharkova, V. V.

2011-01-01

High-energy X-rays and gamma-rays from solar flares were discovered just over fifty years ago. Since that time, the standard for the interpretation of spatially integrated flare X-ray spectra at energies above several tens of keV has been the collisional thick-target model. After the launch of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in early 2002, X-ray spectra and images have been of sufficient quality to allow a greater focus on the energetic electrons responsible for the X-ray emission, including their origin and their interactions with the flare plasma and magnetic field. The result has been new insights into the flaring process, as well as more quantitative models for both electron acceleration and propagation, and for the flare environment with which the electrons interact. In this article we review our current understanding of electron acceleration, energy loss, and propagation in flares. Implications of these new results for the collisional thick-target model, for general flare models, and for future flare studies are discussed.

Solar Flare Abundances of Potassium, Argon, and Sulphur

NASA Technical Reports Server (NTRS)

Oegerle, William (Technical Monitor); Phillips, K. J. H.; Sylwester, J.; Sylwester, B.; Landi, E.

2003-01-01

The absolute coronal abundances of potassium has been determined for the first time from X-ray solar flare line and continuous spectra together with absolute and relative abundances of Ar and S. Potassium is of importance in the continuing debate concerning the nature of the coronal/photospheric element abundance ratios which are widely considered to depend on first ionization potential since it has the lowest FIP of any common element in the Sun. The measurements were obtained with the RESIK crystal spectrometer on the Coronas-F spacecraft. A differential emission measure DEM = const. x exp (-(beta)T(sub e) was found to be the most consistent with the data out of three models considered. We find that the coronal ratio [K/H] = 3.7 x 10(exp - 7), a factor 3 times photospheric, in agreement with other observations using line-to-line ratios. Our measured value for the coronal ratio [Ar/H] = 1.5 x 10(exp -6) is significantly less than photospheric, indicating that there is a slight depletion of this high-FIP element in the corona. For S (an intermediate-FIP element) we obtained [S/H] = 2.2 x 10(exp - 5), approximately the same as in previous work.

Dynamic Precursors of Flares in Active Region NOAA 10486

NASA Astrophysics Data System (ADS)

Korsós, M. B.; Gyenge, N.; Baranyi, T.; Ludmány, A.

2015-03-01

Four different methods are applied here to study the precursors of flare activity in the Active Region NOAA 10486. Two approaches track the temporal behaviour of suitably chosen features (one, the weighted hori- zontal gradient W G M , is the generalized form of the horizontal gradient of the magnetic field, G M ; the other is the sum of the horizontal gradient of the magnetic field, G S , for all sunspot pairs). W G M is a photospheric indicator, that is a proxy measure of magnetic non-potentiality of a specific area of the active region, i.e., it captures the temporal variation of the weighted horizontal gradient of magnetic flux summed up for the region where opposite magnetic polarities are highly mixed. The third one, referred to as the separateness parameter, S l- f , considers the overall morphology. Further, G S and S l- f are photospheric, newly defined quick-look indicators of the polarity mix of the entire active region. The fourth method is tracking the temporal variation of small X-ray flares, their times of succession and their energies observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager instrument. All approaches yield specific pre-cursory signatures for the imminence of flares.

25 Years of Self-Organized Criticality: Solar and Astrophysics

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.; Crosby, Norma B.; Dimitropoulou, Michaila; Georgoulis, Manolis K.; Hergarten, Stefan; McAteer, James; Milovanov, Alexander V.; Mineshige, Shin; Morales, Laura; Nishizuka, Naoto; Pruessner, Gunnar; Sanchez, Raul; Sharma, A. Surja; Strugarek, Antoine; Uritsky, Vadim

2016-01-01

Shortly after the seminal paper "Self-Organized Criticality: An explanation of 1/ f noise" by Bak et al. (1987), the idea has been applied to solar physics, in "Avalanches and the Distribution of Solar Flares" by Lu and Hamilton (1991). In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into the numerical SOC toy models, such as the discretization of magneto-hydrodynamics (MHD) processes. The novel applications stimulated also vigorous debates about the discrimination between SOC models, SOC-like, and non-SOC processes, such as phase transitions, turbulence, random-walk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multi-scale, and other complexity phenomena. We review SOC studies from the last 25 years and highlight new trends, open questions, and future challenges, as discussed during two recent ISSI workshops on this theme.

The flows of He-3 ions from the region of acceleration downwards to the photosphere

NASA Astrophysics Data System (ADS)

Troitskaia, Evgenia; Arkhangelskaja, Irene; Arkhangelsky, Andrey; Lishnevskii, Andrey

We have studied the powerful solar event of January 20, 2005 by nuclear-physics methods. We based on gamma-emission data of AVS-F apparatus from SONG-D detector onboard CORONAS-F satellite. By the statistical modeling method, proposed in MSU SINP, we calculated the temporal profile of 2.223-MeV line. The calculations were performed under assumptions of Bessel type of accelerated particles energy spectrum, different (3) He content in the region of nuclear reactions to occur, and several density models of the solar atmosphere. The 4.44- and 6.13-MeV gamma-lines temporal profiles were also used. A comparison of the results of modeling with observational 2.223 MeV data reveals the numerical values of all mentioned parameters. The method gives the possibility to detect not only the time-averaged 2.223-MeV gamma-emission parameters over the whole flare, but also their evolution with the time of flare. Particularly, the comparison reveals an increase of the ratio of (3) He/ (1) H concentrations during the flare from 2×10 (-5) at the rise phase of the gamma-ray flux up to 2×10 (-4) at the decay one. The (3) He/ (1) H concentration ratio, averaged over whole time of 2.223-MeV gamma-emission, is equal to (1.40±0.15)×10(-4) . The enlarged ratio of (3) He/ (1) H in the region of nuclear reactions to occur and the increase of this ratio with the time may be understood by the supposition of the gradual accumulation of (3) He in the photosphere and low chromosphere. In this case we can assume that the increased (3) He content in the area of neutron interactions with the medium may be due to the predominant acceleration of (3) He ions in the corona. Then the ions slow down and propagate in the solar atmosphere, downward to the lower chromosphere and photosphere, where they can be accumulated. Several authors proposed different mechanisms of (3) He enrichment. For example, it was suggested that ion-acoustic turbulence could be responsible for this process (L. G. Kocharov et al., 1984), or ion-acoustic turbulence in the crossing electrical and magnetic fields (V.P. Silin et al., 1988), or helical turbulence - in non-potential, convolved magnetic fields (G. Fleyshman , et al., 2012). Thus, we make conclusion about the flows of (3) He ions from the region of acceleration downwards to the low chromosphere and the photosphere. We also have a number of observable confirmations of this supposition and give more detailed substantiations and characteristics of the considered phenomenon. Some obtained numerical results are presented.

Extending F10.7’s Time Resolution to Capture Solar Flare Phenomena

DTIC Science & Technology

2008-07-01

Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 REFERENCES ...accelera- tion, (iii) maximum power is emitted in a direction perpendicular to the acceleration, and (iv) the radiation from protons is insignificant...then is P = 2 3 e2 c3 v2⊥e 2B2γ2 m2ec 2 . (2.19) In the electron reference frame, the power emitted is dipolar and in the rest frame, the power is

Time-resolved spectroscopic observations of an M-dwarf flare star EV Lacertae during a flare

NASA Astrophysics Data System (ADS)

Honda, Satoshi; Notsu, Yuta; Namekata, Kosuke; Notsu, Shota; Maehara, Hiroyuki; Ikuta, Kai; Nogami, Daisaku; Shibata, Kazunari

2018-05-01

We have performed five night spectroscopic observations of the Hα line of EV Lac with a medium wavelength resolution (R ˜ 10000) using the 2 m Nayuta telescope at the Nishi-Harima Astronomical Observatory. EV Lac always possesses the Hα emission line; however, its intensity was stronger on 2015 August 15 than during the other four night periods. On this night, we observed a rapid rise (˜20 min) and a subsequent slow decrease (˜1.5 hr) of the emission-line intensity of Hα, which was probably caused by a flare. We also found an asymmetrical change in the Hα line on the same night. The enhancement has been observed in the blue wing of the Hα line during each phase of this flare (from the flare start to the flare end), and absorption components were present in its red wing during the early and later phases of the flare. Such blue enhancement (blue asymmetry) of the Hα line is sometimes seen during solar flares, but only during the early phases. Even for solar flares, little is known about the origin of the blue asymmetry. Compared with solar flare models, the presented results can lead to better understanding of the dynamics of stellar flares.

Serum uric acid levels and the risk of flares among gout patients in a US managed care setting.

PubMed

Shiozawa, Aki; Buysman, Erin K; Korrer, Stephanie

2017-01-01

Serum uric acid (sUA) levels are causally associated with the risk of gout flares. Our aim was to assess the magnitude of the association and time to first flare among patients in a managed care setting. We conducted a retrospective cohort study using administrative claims data from a large US health plan. Patients were required to have evidence of gout based on medical and pharmacy claims between January 2009 and April 2012. The 12 months prior to the index gout claim were used to assess baseline sUA levels; risk of gout flares, stratified by baseline sUA levels, was examined for 2 years post-index. Risk of flare was modeled with Cox proportional hazards; time to first flare was assessed by Kaplan-Meier. We identified 18,008 patients with gout and available baseline SUA levels (mg/dL). The hazard ratios for the risk of gout flares compared with sUA <5.0 were: 1.17 for sUA 5.0 to <6.0; 1.69 for sUA 6.0 to <7.0; 2.16 for sUA 7.0 to <8.0; 2.87 for sUA 8.0 to <9.0; and 3.85 for sUA ≥9.0 (all p < .001 except for sUA 5.0 to <6.0 cohort). The time to first flare was shorter for cohorts with higher baseline sUA levels. These findings confirm that higher sUA levels are associated with an increased risk of gout flares in a dose-response manner over 2 years. This data supports the need to treat to sUA target levels as recommended by recent gout care guidelines. Claims-based algorithms were used to identify gout flares; although this would not be expected to influence estimates of risk by sUA level, there may have been over- or under-estimation of the incidence of flares.

TEMPORAL AND SPATIAL RELATIONSHIP OF FLARE SIGNATURES AND THE FORCE-FREE CORONAL MAGNETIC FIELD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thalmann, J. K.; Veronig, A.; Su, Y., E-mail: julia.thalmann@uni-graz.at

We investigate the plasma and magnetic environment of active region NOAA 11261 on 2011 August 2 around a GOES M1.4 flare/CME (SOL2011-08-02T06:19). We compare coronal emission at the (extreme) ultraviolet and X-ray wavelengths, using SDO AIA and RHESSI images, in order to identify the relative timing and locations of reconnection-related sources. We trace flare ribbon signatures at ultraviolet wavelengths in order to pin down the intersection of previously reconnected flaring loops in the lower solar atmosphere. These locations are used to calculate field lines from three-dimensional (3D) nonlinear force-free magnetic field models, established on the basis of SDO HMI photosphericmore » vector magnetic field maps. Using this procedure, we analyze the quasi-static time evolution of the coronal model magnetic field previously involved in magnetic reconnection. This allows us, for the first time, to estimate the elevation speed of the current sheet’s lower tip during an on-disk observed flare as a few kilometers per second. A comparison to post-flare loops observed later above the limb in STEREO EUVI images supports this velocity estimate. Furthermore, we provide evidence for an implosion of parts of the flaring coronal model magnetic field, and identify the corresponding coronal sub-volumes associated with the loss of magnetic energy. Finally, we spatially relate the build up of magnetic energy in the 3D models to highly sheared fields, established due to the dynamic relative motions of polarity patches within the active region.« less

Radio imaging of solar flares using the very large array - New insights into flare process

NASA Technical Reports Server (NTRS)

Kundu, M. R.; Schmahl, E. J.; Vlahos, L.; Velusamy, T.

1982-01-01

An interpretation of VLA observations of microwave bursts is presented in an attempt to distinguish between certain models of flares. The VLA observations provide information about the pre-flare magnetic field topology and the existence of mildly relativistic electrons accelerated during flares. Examples are shown of changes in magnetic field topology in the hour before flares. In one case, new bipolar loops appear to emerge, which is an essential component of the model developed by Heyvaerts et al. (1977). In another case, a quadrupole structure, suggestive of two juxtaposed bipolar loops, appears to trigger the flare. Because of the observed diversity of magnetic field topologies in microwave bursts, it is believed that the magnetic energy must be dissipated in more than one way. The VLA observations are clearly providing means for sorting out the diverse flare models.

49 CFR 393.95 - Emergency equipment on all power units.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Standard No. 125, § 571.125 of this title; or (2) At least 6 fusees or 3 liquid-burning flares. The vehicle... relative to the motor vehicle. (5) Extinguishing agents. The fire extinguisher must use an extinguishing... for those parts and accessories. (c)-(e) [Reserved] (f) Warning devices for stopped vehicles. Except...

49 CFR 393.95 - Emergency equipment on all power units.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Standard No. 125, § 571.125 of this title; or (2) At least 6 fusees or 3 liquid-burning flares. The vehicle... relative to the motor vehicle. (5) Extinguishing agents. The fire extinguisher must use an extinguishing... for those parts and accessories. (c)-(e) [Reserved] (f) Warning devices for stopped vehicles. Except...

Active Stellar Coronae: Lots of Little Flares?

NASA Astrophysics Data System (ADS)

Drake, J. J.; Kashyap, V. L.; Audard, M.; Guedel, M.

2000-05-01

One of the outstanding questions in stellar X-ray astronomy is the nature of the apparently quiescent emission on active stars -- does this emission actually arise as a superposition of a multitude of impulsive events (such as microflares or nanoflares), or from truly quiescent plasma? This question has gone unanswered due to the difficulties associated with the analysis: [1] the vast majority of the flares that would make up the emission are by definition too weak to be detected, let alone be distinguished from each other; [2] the low count-rates coupled with the small duty cycles of the telescopes increase the ``deadtime'' due to strong flares, masking the superposed weaker flares; and [3] because of the stochastic nature of the onset of the flares the light-curve cannot be simply fit with a suitably parameterized model. The distribution of microflares and nanoflares in the Sun are known to follow a power-law of the form (dN)/(dE)=k E-α (e.g.,Hudson 1991,Sol.Phys.133,357; Parnell & Jupp 2000,ApJ529,554). We adopt a similar model for stellar coronae, and have developed a method to determine the value of α for the given dataset. Because the model is stochastic, we cannot directly compare a simulated light-curve with the observed. Instead, we work directly on event lists (which has the additional advantage of being unbinned) and compare the distribution of photon arrival-time differences between the data and simulated model. Data gaps and deadtime corrections derived for the data set are applied to the simulations before making the comparisons. Many criteria are available to characterize the level of agreement of a model and data. We have used the Kolmogorov-Smirnoff statistic, and the reduced χ2 between the distributions of arrival-time differences as possible measures. We find that the KS statistic is unreliable for smaller values of α , where the spread in the flare intensities is large, but works very well for α >> 2. In contrast, the reduced χ2 provides more reliable error-bars. We show examples of application to EUVE Deep Survey observations of several late-type stars and discuss the results in the context of flare contributions to coronal heating.

ASCA Observations of the Barnard 209 Dark Cloud and an Intense X-Ray Flare on V773 Tauri

NASA Technical Reports Server (NTRS)

Skinner, Stephen L.; Guedel, Manuel; Koyama, Katsuji; Yamauchi, Shigeo

1997-01-01

ASCA (Advanced Satellite for Cosmology and Astrophysics) detected an intense X-ray flare on the weak-lined T Tauri star V773 Tau (=HD 283447) during a 30 ks observation of the Barnard 209 dark cloud in 1995 September. This star is a spectroscopic binary and shows signs of strong magnetic surface activity including a spot-modulated optical light curve. The flare was seen only during its decay phase but is still one of the strongest ever recorded from a T Tauri star with a peak luminosity L(sub x) = 10(exp 32.4) ergs/s (0.5-10 keV), a maximum temperature of at least 42 million K, and energy release of greater than 10(exp 37) ergs. A shorter ASCA observation taken five months later showed V773 Tau in a quiescent state (L(sub x)= 10(exp 31.0) ergs/s) and detected variable emission from the infrared binary IRAS 04113+2758. The differential emission measure (DEM) distribution during the V773 Tau flare shows a bimodal temperature structure that is almost totally dominated by hot plasma at an average temperature of approx. 37 million K. Using information from time-resolved spectra, we examine the flare decay in terms of solar flare models (cooling loops and two-ribbon flares) and also consider possible nonsolar behavior (interbinary flares, star-disk flares, and rotational X-ray modulation). Solar models are unable to reproduce the unusual convex-shaped X-ray light curve, which decays slowly over a timespan of at least 1 day. However, the light curve decay is accurately modeled as a sinusoid with an inferred X-ray period of 2.97 days, which is nearly identical to the optical rotation period(s) of the two K-type components. This provides tantalizing evidence that the flaring region was undergoing rotational occultation, but periodic X-ray variability is not yet proven since our ASCA observation spans only one-third of a rotation cycle.

Psychophysics, flare, and neurosecretory function in human pain models: capsaicin versus electrically evoked pain.

PubMed

Geber, Christian; Fondel, Ricarda; Krämer, Heidrun H; Rolke, Roman; Treede, Rolfe-Detlef; Sommer, Claudia; Birklein, Frank

2007-06-01

Intradermal capsaicin injection (CAP) and electrical current stimulation (ES) are analyzed in respect to patterns and test-retest reliability of pain as well as sensory and neurosecretory changes. In 10 healthy subjects, 2x CAP (50 microg) and 2x ES (5 to 30 mA) were applied to the volar forearm. The time period between 2 identical stimulations was about 4 months. Pain ratings, areas of mechanical hyperalgesia, and allodynia were assessed. The intensity of sensory changes was quantified by using quantitative sensory testing. Neurogenic flare was assessed by using laser Doppler imaging. Calcitonin gene-related peptide (CGRP) release was quantified by dermal microdialysis in combination with an enzyme immunoassay. Time course and peak pain ratings were different between CAP and ES. Test-retest correlation was high (r > or = 0.73). Both models induced primary heat hyperalgesia and primary plus secondary pin-prick hyperalgesia. Allodynia occurred in about half of the subjects. Maximum flare sizes did not differ between CAP and ES, but flare intensities were higher for ES. Test-retest correlation was higher for flare sizes than for flare intensity. A significant CGRP release could only be measured after CAP. The different time courses of pain stimulation (CAP: rapidly decaying pain versus ES: pain plateau) led to different peripheral neurosecretory effects but induced similar central plasticity and hyperalgesia. The present study gives a detailed overview of psychophysical and neurosecretory characteristics induced by noxious stimulation with capsaicin and electrical current. We describe differences, similarities, and reproducibility of these human pain models. These data might help to interpret past and future results of human pain studies using experimental pain.

Study of Historical 4B/X17 Mega Flare on 28 October 2003 (P58)

NASA Astrophysics Data System (ADS)

Uddin, W.; Chandra, R.; Ali, S. S.

2006-11-01

wuddin_99@yahoo.com We analysed multi-wavelength data of 28 October 2003 4B/X17.2 class extremely energetic parallel ribbon solar flare, which occurred in NOAA 10486. The flare was well observed in H-alpha at ARIES, Nainital and various space (SOHO, TRACE, RHESSI, WIND etc.) and ground based Observatories. The H-alpha observations show the stretching/detwisting and eruption of helically twisted S shaped (sigmoid) filament in the South-West direction of the active region with bright shock front followed by rapid increase in intensity and area of the gigantic flare. The flare is associated with a bright/fast full halo earth directed CME, strong type II, III and IV radio bursts, an intense proton event and GLE. It seems that the filament eruption triggered the halo CME because the helical structure is clearly visible in the SOHO/LASCO C2, C3 images. This indicates helicity transfer from chromosphere to corona and interplanetary medium. The magnetic field of the flaring region was most complex with high magnetic shear. From the above analysis we feel that the energy buildup/release process of this unique flare support helically twisted magnetic flux rope model.

“Orphan” γ-Ray Flares and Stationary Sheaths of Blazar Jets

NASA Astrophysics Data System (ADS)

MacDonald, Nicholas R.; Jorstad, Svetlana G.; Marscher, Alan P.

2017-11-01

Blazars exhibit flares across the entire electromagnetic spectrum. Many γ-ray flares are highly correlated with flares detected at longer wavelengths; however, a small subset appears to occur in isolation, with little or no correlated variability at longer wavelengths. These “orphan” γ-ray flares challenge current models of blazar variability, most of which are unable to reproduce this type of behavior. MacDonald et al. have developed the Ring of Fire model to explain the origin of orphan γ-ray flares from within blazar jets. In this model, electrons contained within a blob of plasma moving relativistically along the spine of the jet inverse-Compton scatter synchrotron photons emanating off of a ring of shocked sheath plasma that enshrouds the jet spine. As the blob propagates through the ring, the scattering of the ring photons by the blob electrons creates an orphan γ-ray flare. This model was successfully applied to modeling a prominent orphan γ-ray flare observed in the blazar PKS 1510-089. To further support the plausibility of this model, MacDonald et al. presented a stacked radio map of PKS 1510-089 containing the polarimetric signature of a sheath of plasma surrounding the spine of the jet. In this paper, we extend our modeling and stacking techniques to a larger sample of blazars: 3C 273, 4C 71.01, 3C 279, 1055+018, CTA 102, and 3C 345, the majority of which have exhibited orphan γ-ray flares. We find that the model can successfully reproduce these flares, while our stacked maps reveal the existence of jet sheaths within these blazars.

The morphology of flare phenomena, magnetic fields, and electric currents in active regions. I - Introduction and methods

NASA Technical Reports Server (NTRS)

Canfield, Richard C.; De La Beaujardiere, J.-F.; Fan, Yuhong; Leka, K. D.; Mcclymont, A. N.; Metcalf, Thomas R.; Mickey, Donald L.; Wuelser, Jean-Pierre; Lites, Bruce W.

1993-01-01

Electric current systems in solar active regions and their spatial relationship to sites of electron precipitation and high-pressure in flares were studied with the purpose of providing observational evidence for or against the flare models commonly discussed in the literature. The paper describes the instrumentation, the data used, and the data analysis methods, as well as improvements made upon earlier studies. Several flare models are overviewed, and the predictions yielded by each model for the relationships of flares to the vertical current systems are discussed.

A combined radio and GeV γ-ray view of the 2012 and 2013 flares of Mrk 421

DOE PAGES

Hovatta, Talvikki; Petropoulou, M.; Richards, J. L.; ...

2015-03-09

In 2012 Markarian 421 underwent the largest flare ever observed in this blazar at radio frequencies. In the present study, we start exploring this unique event and compare it to a less extreme event in 2013. We use 15 GHz radio data obtained with the Owens Valley Radio Observatory 40-m telescope, 95 GHz millimetre data from the Combined Array for Research in Millimeter-Wave Astronomy, and GeV γ-ray data from the Fermi Gamma-ray Space Telescope. Here, the radio light curves during the flaring periods in 2012 and 2013 have very different appearances, in both shape and peak flux density. Assuming thatmore » the radio and γ-ray flares are physically connected, we attempt to model the most prominent sub-flares of the 2012 and 2013 activity periods by using the simplest possible theoretical framework. We first fit a one-zone synchrotron self-Compton (SSC) model to the less extreme 2013 flare and estimate parameters describing the emission region. We then model the major γ-ray and radio flares of 2012 using the same framework. The 2012 γ-ray flare shows two distinct spikes of similar amplitude, so we examine scenarios associating the radio flare with each spike in turn. In the first scenario, we cannot explain the sharp radio flare with a simple SSC model, but we can accommodate this by adding plausible time variations to the Doppler beaming factor. In the second scenario, a varying Doppler factor is not needed, but the SSC model parameters require fine-tuning. Both alternatives indicate that the sharp radio flare, if physically connected to the preceding γ-ray flares, can be reproduced only for a very specific choice of parameters.« less

Flared landing approach flying qualities. Volume 2: Appendices

NASA Technical Reports Server (NTRS)

Weingarten, Norman C.; Berthe, Charles J., Jr.; Rynaski, Edmund G.; Sarrafian, Shahan K.

1986-01-01

An in-flight research study was conducted utilizing the USAF/Total In-Flight Simulator (TIFS) to investigate longitudinal flying qualities for the flared landing approach phase of flight. A consistent set of data were generated for: determining what kind of command response the pilot prefers/requires in order to flare and land an aircraft with precision, and refining a time history criterion that took into account all the necessary variables and the characteristics that would accurately predict flying qualities. Seven evaluation pilots participated representing NASA Langley, NASA Dryden, Calspan, Boeing, Lockheed, and DFVLR (Braunschweig, Germany). The results of the first part of the study provide guidelines to the flight control system designer, using MIL-F-8785-(C) as a guide, that yield the dynamic behavior pilots prefer in flared landings. The results of the second part provide the flying qualities engineer with a derived flying qualities predictive tool which appears to be highly accurate. This time-domain predictive flying qualities criterion was applied to the flight data as well as six previous flying qualities studies, and the results indicate that the criterion predicted the flying qualities level 81% of the time and the Cooper-Harper pilot rating, within + or - 1%, 60% of the time.

Flared landing approach flying qualities. Volume 1: Experiment design and analysis

NASA Technical Reports Server (NTRS)

Weingarten, Norman C.; Berthe, Charles J., Jr.; Rynaski, Edmund G.; Sarrafian, Shahan K.

1986-01-01

An inflight research study was conducted utilizing the USAF Total Inflight Simulator (TIFS) to investigate longitudinal flying qualities for the flared landing approach phase of flight. The purpose of the experiment was to generate a consistent set of data for: (1) determining what kind of commanded response the pilot prefers in order to flare and land an airplane with precision, and (2) refining a time history criterion that took into account all the necessary variables and their characteristics that would accurately predict flying qualities. The result of the first part provides guidelines to the flight control system designer, using MIL-F-8785-(C) as a guide, that yield the dynamic behavior pilots perfer in flared landings. The results of the second part provides the flying qualities engineer with a newly derived flying qualities predictive tool which appears to be highly accurate. This time domain predictive flying qualities criterion was applied to the flight data as well as six previous flying qualities studies, and the results indicate that the criterion predicted the flying qualities level 81% of the time and the Cooper-Harper pilot rating, within + or - 1, 60% of the time.

Analysis and modelling of recurrent solar flares observed with Hinode/EIS on March 9, 2012

NASA Astrophysics Data System (ADS)

Polito, V.; Del Zanna, G.; Valori, G.; Pariat, E.; Mason, H. E.; Dudík, J.; Janvier, M.

2017-05-01

Three homologous C-class flares and one last M-class flare were observed by both the Solar Dynamics Observatory (SDO) and the Hinode EUV Imaging Spectrometer (EIS) in the AR 11429 on March 9, 2012. All the recurrent flares occurred within a short interval of time (less than 4 h), showed very similar plasma morphology and were all confined, until the last one when a large-scale eruption occurred. The C-class flares are characterized by the appearance, at approximatively the same locations, of two bright and compact footpoint sources of ≈3-10 MK evaporating plasma, and a semi-circular ribbon. During all the flares, the continuous brightening of a spine-like hot plasma (≈10 MK) structure is also observed. Spectroscopic observations with Hinode/EIS are used to measure and compare the blueshift velocities in the Fe xxiii emission line and the electron number density at the flare footpoints for each flare. Similar velocities, of the order of 150-200 km s-1, are observed during the C2.0 and C4.7 confined flares, in agreement with the values reported by other authors in the study of the last M1.8 class flare. On the other hand, lower electron number densities and temperatures tend to be observed in flares with lower peak soft X-ray flux. In order to investigate the homologous nature of the flares, we performed a non-linear force-free field (NLFFF) extrapolation of the 3D magnetic field configuration in the corona. The NLFFF extrapolation and the Quasi-Separatrix Layers (QSLs) provide the magnetic field context which explains the location of the kernels, spine-like hot plasma and semi-circular brightenings observed in the (non-eruptive) flares. Given the absence of a coronal null point, we argue that the homologous flares were all generated by the continuous recurrence of bald patch reconnection. The movie associated to Fig. 2 is available at http://www.aanda.org

QUASI-PERIODIC PULSATIONS IN THE GAMMA-RAY EMISSION OF A SOLAR FLARE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakariakov, V. M.; Foullon, C.; Inglis, A. R.

2010-01-01

Quasi-periodic pulsations (QPPs) of gamma-ray emission with a period of about 40 s are found in a single loop X-class solar flare on 2005 January 1 at photon energies up to 2-6 MeV with the SOlar Neutrons and Gamma-rays (SONG) experiment aboard the CORONAS-F mission. The oscillations are also found to be present in the microwave emission detected with the Nobeyama Radioheliograph, and in the hard X-ray and low energy gamma-ray channels of RHESSI. Periodogram and correlation analysis shows that the 40 s QPPs of microwave, hard X-ray, and gamma-ray emission are almost synchronous in all observation bands. Analysis ofmore » the spatial structure of hard X-ray and low energy (80-225 keV) gamma-ray QPP with RHESSI reveals synchronous while asymmetric QPP at both footpoints of the flaring loop. The difference between the averaged hard X-ray fluxes coming from the two footpoint sources is found to oscillate with a period of about 13 s for five cycles in the highest emission stage of the flare. The proposed mechanism generating the 40 s QPP is a triggering of magnetic reconnection by a kink oscillation in a nearby loop. The 13 s periodicity could be produced by the second harmonics of the sausage mode of the flaring loop.« less

The Width of a CME and the Source of the Driving Magnetic Explosion

NASA Technical Reports Server (NTRS)

Moore, R. L.; Sterling, A. C.; Suess, S. T.

2007-01-01

We show that the strength of the magnetic field in the area covered by the flare arcade following a CME-producing ejective solar eruption can be estimated from the final angular width of the CME in the outer corona and the final angular width of the flare arcade. We assume (1) the flux-rope plasmoid ejected from the flare site becomes the interior of the CME plasmoid, (2) in the outer corona the CME is roughly a "spherical plasmoid with legs" shaped like a light bulb, and (3) beyond some height in or below the outer corona the CME plasmoid is in lateral pressure balance with the surrounding magnetic field. The strength of the nearly radial magnetic field in the outer corona is estimated from the radial component of the interplanetary magnetic field measured by Ulysses. We apply this model to three well-observed CMEs that exploded from flare regions of extremely different size and magnetic setting. In each event, the estimated source-region field strength is appropriate for the magnetic setting of the flare. This agreement indicates via the model that CMEs (1) are propelled by the magnetic field of the CME plasmoid pushing against the surrounding magnetic field, and (2) can explode from flare regions that are laterally far offset from the radial path of the CME in the outer corona.

KIC 2557430: A Triple System Containing One γ Dor and Two Flaring Components?

NASA Astrophysics Data System (ADS)

Kamil, Ceren; Dal, Hasan Ali

2017-07-01

The results are presented for eclipsing binary KIC 2557430. The mass ratio was computed as 0.868 ± 0.002, while the inclination (i) was found as 69°.75 ± 0°.01 with T 2 = 6271±1 K. 50 frequencies were found in the period analysis. 48 frequencies of them are caused due to the primary component, a γ Doradus star, while two of them are caused by the cool spots. 69 flares were detected in the analyses. Two OPEA models were derived for flares, which indicates that the flares were come from two different sources. The Plateau value was found to be 1.4336 ± 0.1104 s for Source 1, which is seen as possible the secondary component and 0.7550 ± 0.0677 s for Source 2, which is seen as possible third body. The half-life value was computed as 2278.1 s for Group 1 and 1811.2 s for Group 2. The flare frequency N 1 was found to be 0.02726 h -1 and N 2 was computed as 0.00002 for Group 1, while N 1 was found to be 0.01977 h -1 and N 2 was computed as 0.00001 for Group 2. In a results, KIC 2557430 is a possible triple system consisting of a γ Doradus-type star, a chromospherically active star, and also a flaring third body.

Stellar model chromospheres. IX - Chromospheric activity in dwarf stars

NASA Technical Reports Server (NTRS)

Kelch, W. L.; Worden, S. P.; Linsky, J. L.

1979-01-01

High-resolution Ca II K line profiles are used to model the upper photospheres and lower chromospheres of eight main-sequence stars ranging in spectral type from F0 to M0 and exhibiting different degrees of chromospheric activity. The model chromospheres are studied as a function of spectral type and activity for stars of similar spectral type in order to obtain evidence of enhanced nonradiative heating in the upper-photospheric models and in the ratio of minimum temperature at the base of the chromosphere to effective temperature, a correlation between activity and temperature in the lower chromospheres, and a correlation of the width at the base of the K-line emission core and at the K2 features with activity. Chromospheric radiative losses are estimated for the modelled stars and other previously analyzed main-sequence stars. The results obtained strengthen the argument that dMe flare stars exhibit fundamentally solar-type activity but on an increased scale.

Automatic prediction of solar flares and super geomagnetic storms

NASA Astrophysics Data System (ADS)

Song, Hui

Space weather is the response of our space environment to the constantly changing Sun. As the new technology advances, mankind has become more and more dependent on space system, satellite-based services. A geomagnetic storm, a disturbance in Earth's magnetosphere, may produce many harmful effects on Earth. Solar flares and Coronal Mass Ejections (CMEs) are believed to be the major causes of geomagnetic storms. Thus, establishing a real time forecasting method for them is very important in space weather study. The topics covered in this dissertation are: the relationship between magnetic gradient and magnetic shear of solar active regions; the relationship between solar flare index and magnetic features of solar active regions; based on these relationships a statistical ordinal logistic regression model is developed to predict the probability of solar flare occurrences in the next 24 hours; and finally the relationship between magnetic structures of CME source regions and geomagnetic storms, in particular, the super storms when the D st index decreases below -200 nT is studied and proved to be able to predict those super storms. The results are briefly summarized as follows: (1) There is a significant correlation between magnetic gradient and magnetic shear of active region. Furthermore, compared with magnetic shear, magnetic gradient might be a better proxy to locate where a large flare occurs. It appears to be more accurate in identification of sources of X-class flares than M-class flares; (2) Flare index, defined by weighting the SXR flares, is proved to have positive correlation with three magnetic features of active region; (3) A statistical ordinal logistic regression model is proposed for solar flare prediction. The results are much better than those data published in the NASA/SDAC service, and comparable to the data provided by the NOAA/SEC complicated expert system. To our knowledge, this is the first time that logistic regression model has been applied in solar physics to predict flare occurrences; (4) The magnetic orientation angle [straight theta], determined from a potential field model, is proved to be able to predict the probability of super geomagnetic storms (D= st <=-200nT). The results show that those active regions associated with | [straight theta]| < 90° are more likely to cause a super geomagnetic storm.

A flare event of the long-period RS Canum Venaticorum system IM Pegasi

NASA Technical Reports Server (NTRS)

Buzasi, Derek L.; Ramsey, Lawrence W.; Huenemoerder, David P.

1987-01-01

The characteristics of a flare event detected on the long-period RS CVn system IM Pegasi are reported. The low-resolution spectrum show enhancements of up to a factor of five in some emission lines. All of the ultraviolet emission lines normally visible are enhanced significantly more than the normal 30 rotational modulation. Emission fluxes of both the quiescent and flare event are used to construct models of the density and temperature variation with height. These models reveal a downward shift of the transition region during the flare. Scaled models of the quiet and flaring solar outer atmosphere are used to estimate the filling factor of the flare event at about 30 percent of the stellar surface. The pattern of line enhancements in the flare is the same as a previous event in Lambda Andromeda observed previously.

Contribution of Tula Refinery flaring emissions to the Mexico megacity

NASA Astrophysics Data System (ADS)

Almanza, Victor; Molina, Luisa; Sosa, Gustavo

2013-04-01

Flaring is an important source of greenhouse gases, particulate matter and Volatile Organic Compounds (VOCs) in both upstream and downstream operations in the oil and gas industry. In 2010 Mexico was the eleventh emitting country with 2.5 billion cubic meters of gas flared (World Bank, 2012). Black carbon (a component of soot) emissions from flaring facilities are of particular interest because soot is considered a short-lived climate forcer (SLCF) (UNEP, 2011). In 2011 there were 23 megacities of at least 10 million inhabitants. It is expected that this number increase to 37 by 2025, which will include one more in Northern America (NA) and two more in Latin America (UN, 2012). International collaborative projects like MILAGRO in NA and MEGAPOLI/CityZen in Europe, have been conducted to assess the impact of megacities air pollution at several scales. The former focused on the air pollution plume of Mexico City Metropolitan Area (MCMA), the largest megacity in NA. This work studies the contribution of flaring emissions from Tula Refinery to regional air quality. This is accomplished in two steps. First, the flame of a representative sour gas flare is modeled with a CFD combustion code in order to estimate emission rates of combustion by-products of interest for air quality. Mass flow rates of acetylene, ethylene, nitrogen oxides, carbon monoxide, soot and sulfur dioxide are obtained. The emission rates of NO2 and SO2 are compared with measurements obtained at Tula as part of MILAGRO field campaign. The rates of soot, VOCs and CO emissions are compared with estimates obtained by Instituto Mexicano del Petróleo (IMP). The second stage takes the flaring emission rates of the aforementioned species as inputs to WRF-Chem in order to simulate the chemical transport of the plume from 22 March to 27 March of 2006. The air quality model presented reliable performance of the resolved meteorology, with respect to the Mean Absolute Error (MAE), Root Mean Square Error (RMSE), mean bias (BIAS), vector RMSE and Index of Agreement (IOA). WRF-Chem outputs of SO2 and soot are compared with surface measurements obtained at the three supersites of MILAGRO campaign. Results suggest a contribution of Tula flaring activities to the total SO2 levels at the urban supersite (T0) of 37 %, and of 39 % at the suburban supersite (T1). In the MCMA, modeled SO2 is compared with representative monitoring stations of the MCMA Monitoring Network (RAMA). The suggested contribution is about 43 % and 36 % at the north and south regions of the basin respectively. As for soot, results indicate low contribution at the three supersites, with less than 0.1% at three supersites. According to the model, the greatest contribution of Tula flaring emissions to the three supersites and the MCMA basin occurred on 23 March, which coincided with the third cold surge event reported during the campaign.

Application of Convolution Neural Network to the forecasts of flare classification and occurrence using SOHO MDI data

NASA Astrophysics Data System (ADS)

Park, Eunsu; Moon, Yong-Jae

2017-08-01

A Convolutional Neural Network(CNN) is one of the well-known deep-learning methods in image processing and computer vision area. In this study, we apply CNN to two kinds of flare forecasting models: flare classification and occurrence. For this, we consider several pre-trained models (e.g., AlexNet, GoogLeNet, and ResNet) and customize them by changing several options such as the number of layers, activation function, and optimizer. Our inputs are the same number of SOHO)/MDI images for each flare class (None, C, M and X) at 00:00 UT from Jan 1996 to Dec 2010 (total 1600 images). Outputs are the results of daily flare forecasting for flare class and occurrence. We build, train, and test the models on TensorFlow, which is well-known machine learning software library developed by Google. Our major results from this study are as follows. First, most of the models have accuracies more than 0.7. Second, ResNet developed by Microsoft has the best accuracies : 0.86 for flare classification and 0.84 for flare occurrence. Third, the accuracies of these models vary greatly with changing parameters. We discuss several possibilities to improve the models.

The analysis and the three-dimensional, forward-fit modeling of the X-ray and the microwave emissions of major solar flares

NASA Astrophysics Data System (ADS)

Kuroda, Natsuha; Wang, Haimin; Gary, Dale E.

2017-08-01

It is well known that the time profiles of the hard X-ray (HXR) emission and the microwave (MW) emission during the impulsive phase of the solar flare are well correlated, and that their analysis can lead to the understandings of the flare-accelerated electrons. In this work, we first studied the source locations of seven distinct temporal peaks observed in HXR and MW lightcurves of the 2011-02-15 X2.2 flare using the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Nobeyama Radioheliograph. We found that the seven emission peaks did not come from seven spatially distinct sites in HXR and MW, but rather in HXR we observed a sudden change in location only between the second and the third peak, with the same pattern occurring, but evolving more slowly in MW, which is consistent with the tether-cutting model of solar flares. Next, we closely examine the widely-used notion of a "common population" of the accelerated electrons producing the HXR and the MW, which has been challenged by some studies suggesting the differences in the inferred energy spectral index and emitting energies of the HXR- and MW- producing electrons. We use the Non-linear Force Free Field model extrapolated from the observed photospheric magnetogram in the three-dimensional, multi-wavelength modeling platform GX Simulator, and attempt to create a unified electron population model that can simultaneously reproduce the observed X-ray and MW observations of the 2015-06-22 M6.5 flare. We constrain the model parameters by the observations made by the highest-resolving instruments currently available in two wavelengths, the RHESSI for X-ray and the Expanded Owens Valley Solar Array for MW. The results suggest that the X-ray emitting electron population model fits to the standard flare model with the broken, hardening power-law spectrum at ~300 keV that simultaneously produces the HXR footpoint emission and the MW high frequency emission, and also reveals that there could be a “X-ray invisible” population of nonthermal electrons that are trapped in a large magnetic field volume above the X-ray emitting loops, that emits gyrosynchrotron radiation mainly in MW low frequency range.

Gas flare characterisation with Sentinel-3

NASA Astrophysics Data System (ADS)

Caseiro, Alexandre; Kaiser, Johannes W.; Ruecker, Gernot; Tiemann, Joachim; Leimbach, David

2017-04-01

Gas Flaring (GF) is the process of burning waste gases at the tip of a stack. It is widely used in the upstream oil and gas industry. It is a contributor to the imbalance of the greenhouse gases (GHG) concentration in the earth's atmosphere, which prompts global warming. Besides GHG, GF also emits black carbon (BC), a known carcinogen and climate active species. At higher latitudes, GF has been estimated as the main input of atmospheric BC, alongside vegetation fires. The consideration of GF as a source to global budgets has been hindered by technical difficulties of in-situ measurements and the inexistence of a systematic reporting system. Remote sensing offers the possibility of a continuous, global and systematic monitoring of GF over extended periods. Being a high temperature process, GF can be detected from space using measurements at appropriate wavelengths. Considering 1800K as a typical GF temperature and Wien's displacement law, the peak emission will be in the short-wave infrared region. This spectral region is observed by two channels (S5 and S6) of the SLSTR instrument aboard ESA's newly launched Sentinel-3 satellite. Because of solar contamination, only night-time observations are used. In order to characterise the identified gas flares in terms of temperature and area, two Planck curves are fitted to SLSTR radiance observations in five spectral channels (S5 through S9, with F1 and F2). In this work, we present the methodology in detail as well as results for known flaring regions around the world. A comparison with VIIRS on Suomi-NPP and with HSRS on TET-1 over known GF locations is also considered.

YOHKOH Observations at the Y2K Solar Maximum

NASA Astrophysics Data System (ADS)

Aschwanden, M. J.

1999-05-01

Yohkoh will provide simultaneous co-aligned soft X-ray and hard X-ray observations of solar flares at the coming solar maximum. The Yohkoh Soft X-ray Telescope (SXT) covers the approximate temperature range of 2-20 MK with a pixel size of 2.46\\arcsec, and thus complements ideally the EUV imagers sensitive in the 1-2 MK plasma, such as SoHO/EIT and TRACE. The Yohkoh Hard X-ray Telescope (HXT) offers hard X-ray imaging at 20-100 keV at a time resolution of down to 0.5 sec for major events. In this paper we review the major SXT and HXT results from Yohkoh solar flare observations, and anticipate some of the key questions that can be addressed through joint observations with other ground and space-based observatories. This encompasses the dynamics of flare triggers (e.g. emerging flux, photospheric shear, interaction of flare loops in quadrupolar geometries, large-scale magnetic reconfigurations, eruption of twisted sigmoid structures, coronal mass ejections), the physics of particle dynamics during flares (acceleration processes, particle propagation, trapping, and precipitation), and flare plasma heating processes (chromospheric evaporation, coronal energy loss by nonthermal particles). In particular we will emphasize on how Yohkoh data analysis is progressing from a qualitative to a more quantitative science, employing 3-dimensional modeling and numerical simulations.

Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares

NASA Astrophysics Data System (ADS)

Basak, Tamal; Chakrabarti, Sandip Kumar

Excess solar X-ray radiation during solar flares causes an enhancement of ionization in the ionospheric D-region and hence affects sub-ionospherically propagating VLF signal amplitude and phase. VLF signal amplitude perturbation (DeltaA) and amplitude time delay (Deltat) (vis- ´a-vis corresponding X-ray light curve as measured by GOES-15) of NWC/19.8 kHz signal have been computed for solar flares which is detected by us during Jan-Sep 2011. The signal is recorded by SoftPAL facility of IERC/ICSP, Sitapur (22(°) 27'N, 87(°) 45'E), West Bengal, India. In first part of the work, using the well known LWPC technique, we simulated the flare induced excess lower ionospheric electron density by amplitude perturbation method. Unperturbed D-region electron density is also obtained from simulation and compared with IRI-model results. Using these simulation results and time delay as key parameters, we calculate the effective electron recombination coefficient (alpha_{eff}) at solar flare peak region. Our results match with the same obtained by other established models. In the second part, we dealt with the solar zenith angle effect on D-region during flares. We relate this VLF data with the solar X-ray data. We find that the peak of the VLF amplitude occurs later than the time of the X-ray peak for each flare. We investigate this so-called time delay (Deltat). For the C-class flares we find that there is a direct correspondence between Deltat of a solar flare and the average solar zenith angle Z over the signal propagation path at flare occurrence time. Now for deeper analysis, we compute the Deltat for different local diurnal time slots DT. We find that while the time delay is anti-correlated with the flare peak energy flux phi_{max} independent of these time slots, the goodness of fit, as measured by reduced-chi(2) , actually worsens as the day progresses. The variation of the Z dependence of reduced-chi(2) seems to follow the variation of standard deviation of Z along the T_x-R_x propagation path. In other words, for the flares having almost constant Z over the path a tighter anti-correlation between Deltat and phi_{max} was observed.

Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares

NASA Astrophysics Data System (ADS)

Basak, Tamal; Chakrabarti, Sandip K.

2013-12-01

Excess solar X-ray radiation during solar flares causes an enhancement of ionization in the ionospheric D-region and hence affects sub-ionospherically propagating VLF signal amplitude and phase. VLF signal amplitude perturbation (Δ A) and amplitude time delay (Δ t) (vis-á-vis corresponding X-ray light curve as measured by GOES-15) of NWC/19.8 kHz signal have been computed for solar flares which is detected by us during Jan-Sep 2011. The signal is recorded by SoftPAL facility of IERC/ICSP, Sitapur (22∘ 27'N, 87∘ 45'E), West Bengal, India. In first part of the work, using the well known LWPC technique, we simulated the flare induced excess lower ionospheric electron density by amplitude perturbation method. Unperturbed D-region electron density is also obtained from simulation and compared with IRI-model results. Using these simulation results and time delay as key parameters, we calculate the effective electron recombination coefficient ( α eff ) at solar flare peak region. Our results match with the same obtained by other established models. In the second part, we dealt with the solar zenith angle effect on D-region during flares. We relate this VLF data with the solar X-ray data. We find that the peak of the VLF amplitude occurs later than the time of the X-ray peak for each flare. We investigate this so-called time delay (Δ t). For the C-class flares we find that there is a direct correspondence between Δ t of a solar flare and the average solar zenith angle Z over the signal propagation path at flare occurrence time. Now for deeper analysis, we compute the Δ t for different local diurnal time slots DT. We find that while the time delay is anti-correlated with the flare peak energy flux ϕ max independent of these time slots, the goodness of fit, as measured by reduced- χ 2, actually worsens as the day progresses. The variation of the Z dependence of reduced- χ 2 seems to follow the variation of standard deviation of Z along the T x - R x propagation path. In other words, for the flares having almost constant Z over the path a tighter anti-correlation between Δ t and ϕ max was observed.

A new MODIS based approach for gas flared volumes estimation: the case of the Val d'Agri Oil Center (Southern Italy)

NASA Astrophysics Data System (ADS)

Lacava, T.; Faruolo, M.; Coviello, I.; Filizzola, C.; Pergola, N.; Tramutoli, V.

2014-12-01

Gas flaring is one of the most controversial energetic and environmental issues the Earth is facing, moreover contributing to the global warming and climate change. According to the World Bank, each year about 150 Billion Cubic Meter of gas are being flared globally, that is equivalent to the annual gas use of Italy and France combined. Besides, about 400 million tons of CO2 (representing about 1.2% of global CO2 emissions) are added annually into the atmosphere. Efforts to evaluate the impact of flaring on the surrounding environment are hampered by lack of official information on flare locations and volumes. Suitable satellite based techniques could offers a potential solution to this problem through the detection and subsequent mapping of flare locations as well as gas emissions estimation. In this paper a new methodological approach, based on the Robust Satellite Techniques (RST), a multi-temporal scheme of satellite data analysis, was developed to analyze and characterize the flaring activity of the largest Italian gas and oil pre-treatment plant (ENI-COVA) located in Val d'Agri (Basilicata) For this site, located in an anthropized area characterized by a large environmental complexity, flaring emissions are mainly related to emergency conditions (i.e. waste flaring), being the industrial process regulated by strict regional laws. With reference to the peculiar characteristics of COVA flaring, the RST approach was implemented on 13 years of EOS-MODIS (Earth Observing System - Moderate Resolution Imaging Spectroradiometer) infrared data to detect COVA-related thermal anomalies and to develop a regression model for gas flared volume estimation. The methodological approach, the whole processing chain and the preliminarily achieved results will be shown and discussed in this paper. In addition, the possible implementation of the proposed approach on the data acquired by the SUOMI NPP - VIIRS (National Polar-orbiting Partnership - Visible Infrared Imaging Radiometer Suite) and the expected improvements will be also discussed.

Changes in symptoms during urologic chronic pelvic pain syndrome symptom flares: findings from one site of the MAPP Research Network.

PubMed

Sutcliffe, Siobhan; Colditz, Graham A; Pakpahan, Ratna; Bradley, Catherine S; Goodman, Melody S; Andriole, Gerald L; Lai, H Henry

2015-02-01

To provide the first description and quantification of symptom changes during interstitial cystitis/bladder pain syndrome and chronic prostatitis/chronic pelvic pain syndrome symptom exacerbations ("flares"). Participants at one site of the Trans-Multidisciplinary Approaches to the study of chronic Pelvic Pain Epidemiology and Phenotyping Study completed two 10-day diaries over the 1-year study follow-up period, one at baseline and one during their first flare (if not at baseline). On each day of the diary, participants reported whether they were currently experiencing a flare, defined as "symptoms that are much worse than usual" for at least 1 day, and their levels of urination-related pain, pelvic pain, urgency, and frequency on a scale of 0-10. Linear mixed models were used to calculate mean changes in symptoms between non-flare and flare days from the same participant. Eighteen of 27 women and 9 of 29 men reported at least one flare during follow-up, for a total of 281 non-flare and 210 flare days. Of these participants, 44.4% reported one flare, 29.6% reported two flares, and 25.9% reported ≥ 3 flares over the combined 20-day diary observation period, with reported flares ranging in duration from 1 day to >2 weeks. During these flares, each of the main symptoms worsened significantly by a mean of at least two points and total symptoms worsened by a mean of 11 points for both sexes (all P ≤ 0.01). Flares are common and correspond to a global worsening of urologic and pelvic pain symptoms. © 2013 Wiley Periodicals, Inc.

Multi-wavelength Observations and Modeling of Solar Flares: Magnetic Structures

NASA Astrophysics Data System (ADS)

Su, Y.

2017-12-01

We present a review of our recent investigations on multi-wavelength observations and magnetic field modeling of solar flares. High-resolution observations taken by NVST and BBSO/NST reveal unprecedented fine structures of the flaring regions. Observations by SDO, IRIS, and GOES provide the complementary information. The magnetic field models are constructed using either non-linear force free field extrapolations or flux rope insertion method. Our studies have shown that the flaring regions often consist of double or multiple flux ropes, which often exist at different heights. The fine flare ribbon structures may be due to the magnetic reconnection in the complex quasi separatrix layers. The magnetic field modeling of several large flares suggests that the so called hot-channel structure is corresponding to the erupting flux rope above the X-point in a magnetic configuration with Hyperbolic Flux Tube.

Analysis of flares in the chromosphere and corona of main- and pre-main-sequence M-type stars

NASA Astrophysics Data System (ADS)

Crespo-Chacón, I.

2015-11-01

This Ph.D. Thesis revolves around flares on main- and pre-main-sequence M-type stars. We use observations in different wavelength ranges with the aim of analysing the effects of flares at different layers of stellar atmospheres. In particular, optical and X-ray observations are used so that we can study how flares affect, respectively, the chromosphere and the corona of stars. In the optical range we carry out a high temporal resolution spectroscopic monitoring of UV Ceti-type stars aimed at detecting non-white-light flares (the most typical kind of solar flares) in stars other than the Sun. With these data we confirm that non-white-light flares are a frequent phenomenon in UV Ceti-type stars, as observed in the Sun. We study and interpret the behaviour of different chromospheric lines during the flares detected on AD Leo. By using a simplified slab model of flares (Jevremović et al. 1998), we are able to determine the physical parameters of the chromospheric flaring plasma (electron density and electron temperature), the temperature of the underlying source, and the surface area covered by the flaring plasma. We also search for possible relationships between the physical parameters of the flaring plasma and other properties such as the flare duration, area, maximum flux and released energy. This work considerably extends the existing sample of stellar flares analysed with good quality spectroscopy in the optical range. In X-rays we take advantage of the great sensitivity, wide energy range, high energy resolution, and continuous time coverage of the EPIC detectors - on-board the XMMNewton satellite - in order to perform time-resolved spectral analysis of coronal flares. In particular, in the UV Ceti-type star CC Eri we study two flares that are weaker than those typically reported in the literature (allowing us to speculate about the role of flares as heating agents of stellar atmospheres); while in the pre-main-sequence M-type star TWA 11B (with no signatures of having an accretion disk) we carry out a detailed analysis of an extremely long rise phase and of a shorter, weaker flare (allowing us to compare the results with those reported for young stars but surrounded by disks). Assuming multitemperature models to describe the coronal flaring plasma, we have calculated the metal abundance, the electron temperatures and the respective emission measures by fitting the spectra with the Astrophysical Plasma Emission Code included in the XSPEC software, which calculates spectral models for hot, optically thin plasmas. Moreover, we are able to estimate the size of the flaring loops by using theoretical models. These sizes give us an idea about the extent of the corona. For those flares in which heating does not entirely drive the flare evolution we use the models reported by Reale (2007) and Reale et al. (1997) for the rise and decay phases, respectively, including the effect of sustained heating during the decay. Instead, the stellar version of the Kopp & Poletto (1984)'s solar two-ribbon flare model (Poletto et al. 1988) is used when the residual heating completely drives the flare over the plasma cooling. Later, we apply the so-called RTV scaling laws (Rosner et al. 1978) and other fundamental laws of physics to determine additional characteristics of the plasma contained in the flaring loops (electron density and pressure), as well as the volume of the flaring region, the heating rate per unit volume, and the strength of the magnetic field required to confine this plasma. Making some assumptions we are also able to estimate the number of loops involved in the observed flares and the kind of magnetic structures present in the atmosphere of these types of stars. Finally, we discuss and interpret the results in the context of solar and stellar flares reported so far.

Vortex and Sink Flows in Eruptive Flares as a Model for Coronal Implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuccarello, F. P.; Aulanier, G.; Démoulin, P.

Eruptive flares are sudden releases of magnetic energy that involve many phenomena, several of which can be explained by the standard 2D flare model and its realizations in 3D. We analyze a 3D magnetohydrodynamics simulation, in the framework of this model, that naturally explains the contraction of coronal loops in the proximity of the flare sites, as well as the inflow toward the region above the cusp-shaped loops. We find that two vorticity arcs located along the flanks of the erupting magnetic flux rope are generated as soon as the eruption begins. The magnetic arcades above the flux rope legsmore » are then subjected to expansion, rotation, or contraction depending on which part of the vortex flow advects them. In addition to the vortices, an inward-directed magnetic pressure gradient exists in the current sheet below the magnetic flux rope. It results in the formation of a sink that is maintained by reconnection. We conclude that coronal loop apparent implosions observed during eruptive flares are the result of hydromagnetic effects related to the generation of vortex and sink flows when a flux rope moves in a magnetized environment.« less

Multiwavelength observations of Mrk 501 in 2008

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleksic, J.; Ansoldi, S.; Antonelli, L. A.

2015-01-01

Context. Blazars are variable sources on various timescales over a broad energy range spanning from radio to very high energy (>100 GeV, hereafter VHE). Mrk 501 is one of the brightest blazars at TeV energies and has been extensively studied since its first VHE detection in 1996. However, most of the γ-ray studies performed on Mrk 501 during the past years relate to flaring activity, when the source detection and characterization with the available γ-ray instrumentation was easier toperform. Aims. Our goal is to characterize the source γ-ray emission in detail, together with the radio-to-X-ray emission, during the non-flaring (low)more » activity, which is less often studied than the occasional flaring (high) activity. Methods. We organized a multiwavelength (MW) campaign on Mrk 501 between March and May 2008. This multi-instrument effort included the most sensitive VHE γ-ray instruments in the northern hemisphere, namely the imaging atmospheric Cherenkov telescopes MAGIC and VERITAS, as well as Swift, RXTE, the F-GAMMA, GASP-WEBT, and other collaborations and instruments. This provided extensive energy and temporal coverage of Mrk 501 throughout the entire campaign. Results. Mrk 501 was found to be in a low state of activity during the campaign, with a VHE flux in the range of 10%–20% of the Crab nebula flux. Nevertheless, significant flux variations were detected with various instruments, with a trend of increasing variability with energy and a tentative correlation between the X-ray and VHE fluxes. The broadband spectral energy distribution during the two different emission states of the campaign can be adequately described within the homogeneous one-zone synchrotron self-Compton model, with the (slightly) higher state described by an increase in the electron number density. Conclusions. The one-zone SSC model can adequately describe the broadband spectral energy distribution of the source during the two months covered by the MW campaign. This agrees with previous studies of the broadband emission of this source during flaring and non-flaring states. We report for the first time a tentative X-ray-to-VHE correlation during such a low VHE activity. Although marginally significant, this positive correlation between X-ray and VHE, which has been reported many times during flaring activity, suggests that the mechanisms that dominate the X-ray/VHE emission during non-flaring-activity are not substantially different from those that are responsible for the emission during flaring activity.« less

RADIO FREQUENCY ATTENUATOR

DOEpatents

Giordano, S.

1963-11-12

A high peak power level r-f attenuator that is readily and easily insertable along a coaxial cable having an inner conductor and an outer annular conductor without breaking the ends thereof is presented. Spaced first and second flares in the outer conductor face each other with a slidable cylindrical outer conductor portion therebetween. Dielectric means, such as water, contact the cable between the flares to attenuate the radio-frequency energy received thereby. The cylindrical outer conductor portion is slidable to adjust the voltage standing wave ratio to a low level, and one of the flares is slidable to adjust the attenuation level. An integral dielectric container is also provided. (AFC)

Discovery of decaHz flaring in SAX J1808.4-3658

NASA Astrophysics Data System (ADS)

Bult, P.

2014-01-01

We report on the discovery of strong decaHz flaring in the early decay of two out of five outbursts of the accreting millisecond X-ray pulsar SAX J1808.4-3658. The decaHz flaring switches on and, after ~3 days, off again, on a time scale of 1-2 hours. When the flaring is present, the total 0.05-10 Hz variability has a fractional rms amplitude of 20 to 30 percent, well in excess of the 8 to 12 percent rms broad-band noise usually seen in power spectra of SAX J1808 in this frequency range. Coherent 401 Hz pulsations are seen throughout the observations in which the decaHz flaring is detected. We find that the absolute amplitude of the pulsations varies with the flux modulation of the decaHz flaring, indicating that the flaring is caused by an accretion rate modulation already present in the accretion flow prior to matter entering the accretion funnel. We suggest that the decaHz flaring is the result of the Spruit-Taam instability [1]. This instability arises when the inner accretion disk approaches co-rotation. The rotation of the stellar magnetosphere then acts as a propeller, suppressing accretion onto the neutron star. A matter reservoir forms in the inner accretion disk, which episodically empties onto the neutron star, causing flares at a decaHz timescale. A similar explanation was proposed earlier for 1 Hz flaring occurring late in three of five outbursts, mutually exclusive with the decaHz flaring. The 1 Hz flaring was observed at luminosities a factor 5 to 10 below where we see the decaHz flaring. That a different branch of the Spruit-Taam instability could also act at the much higher luminosity levels of the decaHz flaring had recently been predicted by D'Angelo & Spruit [2, 3]. We discuss these findings in the context of the parameters of the Spruit-Taam-d'Angelo model of the instability. If confirmed, after millisecond pulsations, 1 Hz and decaHz flaring would be another diagnostic of the presence of a magnetosphere in accreting low-magnetic field neutron stars.

Triggering Scenario of Geo-effective Solar Eruption on 15 March 2015

NASA Astrophysics Data System (ADS)

Bamba, Yumi; Inoue, Satoshi; Hayashi, Keiji

2017-08-01

The largest magnetic storm so far, called St Patricks’s Day event, in the solar cycle 24 occurred on 17 March 2015. It was caused by fast coronal mass ejection (CME) on 15 March 2015 from solar active region (AR) NOAA 12297. Surprisingly, the CME is suggested to be related to a C9.1 flare while the large CME is usually corresponding to a large flare. The purpose of this study is to understand the onset mechanism of the huge solar eruption which caused big impact on a magnetic environment of the geospace. The magnetic field structure in the AR was complicated: There were several filaments including the one which erupted and caused the CME. We hence carefully investigated the photospheric magnetic field, brightenings observed in the region from the chromosphere to the corona, and the three-dimensional coronal magnetic field calculated through our nonlinear force-free field (NLFFF) model using photospheric vector magnetic field data from the Hinode SOT and the Solar Dynamics Observatory (SDO). We focused on the C2.4 flare occurred prior to the C9.1 flare and filament eruption. Through our provisional analysis covering long time span, we noticed the C2.4 flare prior to the C9.1 flare is important to understanding the dynamics of this AR system and the CME event. (1) There was a compact but noticeably highly twisted magnetic field structure. During the C2.4 flare, flux cancellation was seen on the photospheric magnetic field data. (2) The erupting filament is sustained by the coronal magnetic field prior to the flare, and C2.4 flaring site locates in the vicinity of one footpoint of them. (3) The top of the coronal loops sustaining the filament touch to a region where the torus instability would be expected.Therefore, we consider that the magnetic reconnection at the C2.4 flaring site changed the magnetic environment of the filament, destabilized the highly twisted magnetic field structure, and finally allowed the twisted magnetic field to erupt.

Investigation of physical parameters in stellar flares observed by GINGA

NASA Technical Reports Server (NTRS)

Stern, Robert A.

1994-01-01

This program involves analysis and interpretation of results from GINGA Large Area Counter (LAC) observations from a group of large stellar x-ray flares. All LAC data are re-extracted using the standard Hayashida method of LAC background subtraction and analyzed using various models available with the XSPEC spectral fitting program. Temperature-emission measure histories are available for a total of 5 flares observed by GINGA. These will be used to compare physical parameters of these flares with solar and stellar flare models.

Investigation of physical parameters in stellar flares observed by GINGA

NASA Technical Reports Server (NTRS)

Stern, Robert A.

1994-01-01

This program involves analysis and interpretation of results from GINGA Large Area Counter (LAC) observations from a group of large stellar X-ray flares. All LAC data are re-extracted using the standard Hayashida method of LAC background subtraction and analyzed using various models available with the XSPEC spectral fitting program.Temperature-emission measure histories are available for a total of 5 flares observed by GINGA. These will be used to compare physical parameters of these flares with solar and stellar flare models.

The Second Catalog of Flaring Gamma-Ray Sources from the Fermi All-sky Variability Analysis

NASA Astrophysics Data System (ADS)

Abdollahi, S.; Ackermann, M.; Ajello, M.; Albert, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Becerra Gonzalez, J.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini, E.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Chekhtman, A.; Cheung, C. C.; Chiaro, G.; Ciprini, S.; Conrad, J.; Costantin, D.; Costanza, F.; Cutini, S.; D'Ammando, F.; de Palma, F.; Desai, A.; Desiante, R.; Digel, S. W.; Di Lalla, N.; Di Mauro, M.; Di Venere, L.; Donaggio, B.; Drell, P. S.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giomi, M.; Giordano, F.; Giroletti, M.; Glanzman, T.; Green, D.; Grenier, I. A.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hays, E.; Horan, D.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Kocevski, D.; Kuss, M.; La Mura, G.; Larsson, S.; Latronico, L.; Li, J.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill, J. D.; Maldera, S.; Manfreda, A.; Mayer, M.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Negro, M.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Paliya, V. S.; Paneque, D.; Perkins, J. S.; Persic, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Porter, T. A.; Principe, G.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Sgrò, C.; Simone, D.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Stawarz, L.; Suson, D. J.; Takahashi, M.; Tanaka, K.; Thayer, J. B.; Thompson, D. J.; Torres, D. F.; Torresi, E.; Tosti, G.; Troja, E.; Vianello, G.; Wood, K. S.

2017-09-01

We present the second catalog of flaring gamma-ray sources (2FAV) detected with the Fermi All-sky Variability Analysis (FAVA), a tool that blindly searches for transients over the entire sky observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. With respect to the first FAVA catalog, this catalog benefits from a larger data set, the latest LAT data release (Pass 8), as well as from an improved analysis that includes likelihood techniques for a more precise localization of the transients. Applying this analysis to the first 7.4 years of Fermi observations, and in two separate energy bands 0.1-0.8 GeV and 0.8-300 GeV, a total of 4547 flares were detected with significance greater than 6σ (before trials), on the timescale of one week. Through spatial clustering of these flares, 518 variable gamma-ray sources were identified. Based on positional coincidence, likely counterparts have been found for 441 sources, mostly among the blazar class of active galactic nuclei. For 77 2FAV sources, no likely gamma-ray counterpart has been found. For each source in the catalog, we provide the time, location, and spectrum of each flaring episode. Studying the spectra of the flares, we observe a harder-when-brighter behavior for flares associated with blazars, with the exception of BL Lac flares detected in the low-energy band. The photon indexes of the flares are never significantly smaller than 1.5. For a leptonic model, and under the assumption of isotropy, this limit suggests that the spectrum of freshly accelerated electrons is never harder than p˜ 2.

UV/Optical Detections of Candidate Tidal Disruption Events by GALEX and CFHTLS

NASA Astrophysics Data System (ADS)

Gezari, S.; Basa, S.; Martin, D. C.; Bazin, G.; Forster, K.; Milliard, B.; Halpern, J. P.; Friedman, P. G.; Morrissey, P.; Neff, S. G.; Schiminovich, D.; Seibert, M.; Small, T.; Wyder, T. K.

2008-04-01

We present two luminous UV/optical flares from the nuclei of apparently inactive early-type galaxies at z = 0.37 and 0.33 that have the radiative properties of a flare from the tidal disruption of a star. In this paper we report the second candidate tidal disruption event discovery in the UV by the GALEX Deep Imaging Survey and present simultaneous optical light curves from the CFHTLS Deep Imaging Survey for both UV flares. The first few months of the UV/optical light curves are well fitted with the canonical t-5/3 power-law decay predicted for emission from the fallback of debris from a tidally disrupted star. Chandra ACIS X-ray observations during the flares detect soft X-ray sources with Tbb = (2-5) × 105 K or Γ > 3 and place limits on hard X-ray emission from an underlying AGN down to LX(2-10 keV) lesssim 1041 ergs s-1. Blackbody fits to the UV/optical spectral energy distributions of the flares indicate peak flare luminosities of gtrsim1044-1045 ergs s-1. The temperature, luminosity, and light curves of both flares are in excellent agreement with emission from a tidally disrupted main-sequence star onto a central black hole of several times 107 M⊙. The observed detection rate of our search over ~2.9 deg2 of GALEX Deep Imaging Survey data spanning from 2003 to 2007 is consistent with tidal disruption rates calculated from dynamical models, and we use these models to make predictions for the detection rates of the next generation of optical synoptic surveys. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Dynamic data-driven integrated flare model based on self-organized criticality

NASA Astrophysics Data System (ADS)

Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M. K.

2013-05-01

Context. We interpret solar flares as events originating in active regions that have reached the self-organized critical state. We describe them with a dynamic integrated flare model whose initial conditions and driving mechanism are derived from observations. Aims: We investigate whether well-known scaling laws observed in the distribution functions of characteristic flare parameters are reproduced after the self-organized critical state has been reached. Methods: To investigate whether the distribution functions of total energy, peak energy, and event duration follow the expected scaling laws, we first applied the previously reported static cellular automaton model to a time series of seven solar vector magnetograms of the NOAA active region 8210 recorded by the Imaging Vector Magnetograph on May 1 1998 between 18:59 UT and 23:16 UT until the self-organized critical state was reached. We then evolved the magnetic field between these processed snapshots through spline interpolation, mimicking a natural driver in our dynamic model. We identified magnetic discontinuities that exceeded a threshold in the Laplacian of the magnetic field after each interpolation step. These discontinuities were relaxed in local diffusion events, implemented in the form of cellular automaton evolution rules. Subsequent interpolation and relaxation steps covered all transitions until the end of the processed magnetograms' sequence. We additionally advanced each magnetic configuration that has reached the self-organized critical state (SOC configuration) by the static model until 50 more flares were triggered, applied the dynamic model again to the new sequence, and repeated the same process sufficiently often to generate adequate statistics. Physical requirements, such as the divergence-free condition for the magnetic field, were approximately imposed. Results: We obtain robust power laws in the distribution functions of the modeled flaring events with scaling indices that agree well with observations. Peak and total flare energy obey single power laws with indices -1.65 ± 0.11 and -1.47 ± 0.13, while the flare duration is best fitted with a double power law (-2.15 ± 0.15 and -3.60 ± 0.09 for the flatter and steeper parts, respectively). Conclusions: We conclude that well-known statistical properties of flares are reproduced after active regions reach the state of self-organized criticality. A significant enhancement of our refined cellular automaton model is that it initiates and further drives the simulation from observed evolving vector magnetograms, thus facilitating energy calculation in physical units, while a separation between MHD and kinetic timescales is possible by assigning distinct MHD timestamps to each interpolation step.

Observational and Model Analysis of a Two-ribbon Flare Possibly Induced by a Neighboring Blowout Jet

NASA Astrophysics Data System (ADS)

Joshi, Bhuwan; Thalmann, Julia K.; Mitra, Prabir K.; Chandra, Ramesh; Veronig, Astrid M.

2017-12-01

In this paper, we present unique observations of a blowout coronal jet that possibly triggered a two-ribbon confined C1.2 flare in bipolar solar active region NOAA 12615 on 2016 December 5. The jet activity initiates at chromospheric/transition region heights with a small brightening that eventually increases in volume, with well-developed standard morphological jet features, viz., base and spire. The spire widens up with a collimated eruption of cool and hot plasma components, observed in the 304 and 94 Å channels of AIA, respectively. The speed of the plasma ejection, which forms the jet’s spire, was higher for the hot component (˜200 km s-1) than the cooler one (˜130 km s-1). The NLFF model of coronal fields at the pre- and post-jet phases successfully reveals openings of previously closed magnetic field lines with a rather inclined/low-lying jet structure. The peak phase of the jet emission is followed by the development of a two-ribbon flare that shows coronal loop emission in HXRs up to ˜25 keV energy. The coronal magnetic fields rooted at the location of EUV flare ribbons, derived from the NLFF model, demonstrate the pre-flare phase to exhibit an “X-type” configuration, while the magnetic fields at the post-flare phase are more or less oriented parallel. Comparisons of multi-wavelength measurements with the magnetic field extrapolations suggest that the jet activity likely triggered the two-ribbon flare by perturbing the field in the interior of the active region.

ABOVE-THE-LOOP-TOP OSCILLATION AND QUASI-PERIODIC CORONAL WAVE GENERATION IN SOLAR FLARES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takasao, Shinsuke; Shibata, Kazunari, E-mail: takasao@kwasan.kyoto-u.ac.jp

Observations revealed that various kinds of oscillations are excited in solar flare regions. Quasi-periodic pulsations (QPPs) in flare emissions are commonly observed in a wide range of wavelengths. Recent observations have found that fast-mode magnetohydrodynamic (MHD) waves are quasi-periodically emitted from some flaring sites (quasi-periodic propagating fast-mode magnetoacoustic waves; QPFs). Both QPPs and QPFs imply a cyclic disturbance originating from the flaring sites. However, the physical mechanisms remain puzzling. By performing a set of two-dimensional MHD simulations of a solar flare, we discovered the local oscillation above the loops filled with evaporated plasma (above-the-loop-top region) and the generation of QPFsmore » from such oscillating regions. Unlike all previous models for QPFs, our model includes essential physics for solar flares such as magnetic reconnection, heat conduction, and chromospheric evaporation. We revealed that QPFs can be spontaneously excited by the above-the-loop-top oscillation. We found that this oscillation is controlled by the backflow of the reconnection outflow. The new model revealed that flare loops and the above-the-loop-top region are full of shocks and waves, which is different from the previous expectations based on a standard flare model and previous simulations. In this paper, we show the QPF generation process based on our new picture of flare loops and will briefly discuss a possible relationship between QPFs and QPPs. Our findings will change the current view of solar flares to a new view in which they are a very dynamic phenomenon full of shocks and waves.« less

Improvements to the ShipIR/NTCS adaptive track gate algorithm and 3D flare particle model

NASA Astrophysics Data System (ADS)

Ramaswamy, Srinivasan; Vaitekunas, David A.; Gunter, Willem H.; February, Faith J.

2017-05-01

A key component in any image-based tracking system is the adaptive tracking algorithm used to segment the image into potential targets, rank-and-select the best candidate target, and gate the selected target to further improve tracker performance. Similarly, a key component in any soft-kill response to an incoming guided missile is the flare/chaff decoy used to distract or seduce the seeker homing system away from the naval platform. This paper describes the recent improvements to the naval threat countermeasure simulator (NTCS) of the NATO-standard ship signature model (ShipIR). Efforts to analyse and match the 3D flare particle model against actual IR measurements of the Chemring TALOS IR round resulted in further refinement of the 3D flare particle distribution. The changes in the flare model characteristics were significant enough to require an overhaul to the adaptive track gate (ATG) algorithm in the way it detects the presence of flare decoys and reacquires the target after flare separation. A series of test scenarios are used to demonstrate the impact of the new flare and ATG on IR tactics simulation.

Revealing the Evolution of Non-thermal Electrons in Solar Flares Using 3D Modeling

NASA Astrophysics Data System (ADS)

Fleishman, Gregory D.; Nita, Gelu M.; Kuroda, Natsuha; Jia, Sabina; Tong, Kevin; Wen, Richard R.; Zhizhuo, Zhou

2018-05-01

Understanding non-thermal particle generation, transport, and escape in solar flares requires detailed quantification of the particle evolution in the realistic 3D domain where the flare takes place. Rather surprisingly, apart from the standard flare scenario and integral characteristics of non-thermal electrons, not much is known about the actual evolution of non-thermal electrons in the 3D spatial domain. This paper attempts to begin to remedy this situation by creating sets of evolving 3D models, the synthesized emission from which matches the evolving observed emission. Here, we investigate two contrasting flares: a dense, “coronal-thick-target” flare SOL2002-04-12T17:42, that contained a single flare loop observed in both microwaves and X-rays, and a more complex flare, SOL2015-06-22T17:50, that contained at least four distinct flaring loops needed to consistently reproduce the microwave and X-ray emission. Our analysis reveals differing evolution patterns for the non-thermal electrons in the dense and tenuous loops; however, both patterns suggest that resonant wave–particle interactions with turbulence play a central role. These results offer new constraints for theory and models of the particle acceleration and transport in solar flares.

Hot coronal plasma phenomena disclosed, classified and studied in the SPIRIT experiment on CORONAS-F mission

NASA Astrophysics Data System (ADS)

Urnov, Alexander; Kuzin, Sergey; Bogachev, Sergey; Goryaev, Farid; Dennis, Brian; Reva, Anton; Shestov, Sergey; Soloviev, Alexander; Zhitnik, Igor

The advent of XUV full-Sun monochromatic imaging spectroscopy in the SPIRIT experiment on CORONAS-F (2001-2005) helped to reveal highly dynamic 4 -20 MK coronal plasma structures characterized by various sizes from 6" through 0.3 solar radius and lifetimes from several minutes to several days. Due to the high dynamic range (more than four orders of magnitude) of the X-Ray detector, the monochromatic images in the Mg XII ion line at 8.42 ˚ allowed the A whole Sun light curves of the GOES 1-8˚ channel to be decomposed over the temporal flux A profiles of individual X-Ray sources. Thus, the GOES background emission was shown to be the result of a superposition of a series of low intensity "elemental bursts" each lasting for 10-20 min and recurring at different locations on the solar disk. A new phenomenon of small size, short-lived X-ray "hot spots" (hot X-ray bright points, HXBP) has been disclosed in addition to the previously reported giant post-eruptive sources ("spiders"). The classification has been proposed of hot plasma phenomena by their spatial and temporal properties being the "markers" of energy storage and release sites for all observable X-ray sources. It was also shown that these sources are characterized by complex topology rather than by the strength of the magnetic field since they associated only with active region loop systems comprising of more than two spots. Diagnostic techniques developed on the basis of monochromatic and broad band data simultaneously measured on CORONAS-F, GOES, and RHESSI were used to obtain space-time dynamics of the temperature and density content for hot coronal plasma structures in the range logT=6.0 -7.2. A theoretical description of the spider phenomena based on long-duration recurrently flaring giant magneto-plasma formations, is given using the Chandrasekhar-Prendergast model of a spherical magnetic vortex, generalized to account for density perturbations. This model presents a sequence of magnetic toroidal configurations stabilized within a spherical cover by an external potential magnetic field. It reveals remarkable properties that help to explain, by simple physical considerations, how the conditions sufficient for fast and efficient energy release, specific for a weak flare, may take place sporadically without disrupting the whole system. The generalized solution gives a realistic picture of observable phenomena allowing new possibilities for the generation of dissipative flare-like processes in the spherical magnetic vortex, and, thus, providing a natural description of their specific features.

Multiwavelength Observations of the Blazar BL Lacertae: A New Fast TeV Gamma-Ray Flare

NASA Astrophysics Data System (ADS)

Abeysekara, A. U.; Benbow, W.; Bird, R.; Brantseg, T.; Brose, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Connolly, M. P.; Cui, W.; Daniel, M. K.; Falcone, A.; Feng, Q.; Finley, J. P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Gunawardhana, I.; Hütten, M.; Hanna, D.; Hervet, O.; Holder, J.; Hughes, G.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kertzman, M.; Krennrich, F.; Lang, M. J.; Lin, T. T. Y.; McArthur, S.; Moriarty, P.; Mukherjee, R.; O’Brien, S.; Ong, R. A.; Otte, A. N.; Park, N.; Petrashyk, A.; Pohl, M.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rulten, C.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Wakely, S. P.; Weinstein, A.; Wells, R. M.; Wilcox, P.; Williams, D. A.; Zitzer, B.; The VERITAS Collaboration; Jorstad, S. G.; Marscher, A. P.; Lister, M. L.; Kovalev, Y. Y.; Pushkarev, A. B.; Savolainen, T.; Agudo, I.; Molina, S. N.; Gómez, J. L.; Larionov, V. M.; Borman, G. A.; Mokrushina, A. A.; Tornikoski, M.; Lähteenmäki, A.; Chamani, W.; Enestam, S.; Kiehlmann, S.; Hovatta, T.; Smith, P. S.; Pontrelli, P.

2018-04-01

Combined with measurements made by very-long-baseline interferometry, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and only within the last few years have these flares been observed from lower-frequency-peaked BL Lac objects and flat-spectrum radio quasars. We report on a fast TeV gamma-ray flare from the blazar BL Lacertae observed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS). with a rise time of ∼2.3 hr and a decay time of ∼36 min. The peak flux above 200 GeV is (4.2 ± 0.6) × 10‑6 photon m‑2 s‑1 measured with a 4-minute-binned light curve, corresponding to ∼180% of the flux that is observed from the Crab Nebula above the same energy threshold. Variability contemporaneous with the TeV gamma-ray flare was observed in GeV gamma-ray, X-ray, and optical flux, as well as in optical and radio polarization. Additionally, a possible moving emission feature with superluminal apparent velocity was identified in Very Long Baseline Array observations at 43 GHz, potentially passing the radio core of the jet around the time of the gamma-ray flare. We discuss the constraints on the size, Lorentz factor, and location of the emitting region of the flare, and the interpretations with several theoretical models that invoke relativistic plasma passing stationary shocks.

A systematic Chandra study of Sgr A⋆: II. X-ray flare statistics

NASA Astrophysics Data System (ADS)

Yuan, Qiang; Wang, Q. Daniel; Liu, Siming; Wu, Kinwah

2018-01-01

The routinely flaring events from Sgr A⋆ trace dynamic, high-energy processes in the immediate vicinity of the supermassive black hole. We statistically study temporal and spectral properties, as well as fluence and duration distributions, of the flares detected by the Chandra X-ray Observatory from 1999 to 2012. The detection incompleteness and bias are carefully accounted for in determining these distributions. We find that the fluence distribution can be well characterized by a power law with a slope of 1.73^{+0.20}_{-0.19}, while the durations (τ in seconds) by a lognormal function with a mean log (τ)=3.39^{+0.27}_{-0.24} and an intrinsic dispersion σ =0.28^{+0.08}_{-0.06}. No significant correlation between the fluence and duration is detected. The apparent positive correlation, as reported previously, is mainly due to the detection bias (i.e. weak flares can be detected only when their durations are short). These results indicate that the simple self-organized criticality model has difficulties in explaining these flares. We further find that bright flares usually have asymmetric light curves with no statistically evident difference/preference between the rising and decaying phases in terms of their spectral/timing properties. Our spectral analysis shows that although a power-law model with a photon index of 2.0 ± 0.4 gives a satisfactory fit to the joint spectra of strong and weak flares, there is weak evidence for a softer spectrum of weaker flares. This work demonstrates the potential to use statistical properties of X-ray flares to probe their trigger and emission mechanisms, as well as the radiation propagation around the black hole.

Cool Spot and Flare Activities of a RS CVn Binary KIC 7885570

NASA Astrophysics Data System (ADS)

Kunt, M.; Dal, H. A.

2017-12-01

We present here the results of our studies on the physical nature and chromospheric activity of a RS CVn binary KIC 7885570 based on the Kepler Mission data. Assuming the primary component temperature, 6530 K, the temperature of the secondary component was found to be 5732±4 K. The mass ratio of the components (q) was found to be 0.43±0.01, while the inclination (i) of the system - 80.6°±0.1°. Additionally, the data were separated into 35 subsets to model the sinusoidal variation due to the rotational modulation, using the SpotModel program, as the light curve analysis indicated the chromospherically active secondary component. It was found that there are generally two spotted areas, whose radii, longitudes and latitudes are rapidly changing, located around the latitudes of +50° and +90° on the active component. Moreover, 113 flares were detected and their parameters were computed from the available data. The One Phase Exponential Association function model was derived from the parameters of these flares. Using the regression calculations, the Plateau value was found to be 1.9815±0.1177, while the half-life value was computed as 3977.2 s. In addition, the flare frequency (N1) - the flare number per hour, was estimated to be 0.00362 h-1, while flare frequency (N2) - the flare-equivalent duration emitted per hour, was computed as 0.00001. Finally, the times of eclipses were computed for 278 minima of the light curves, whose analysis indicated that the chromosphere activity nature of the system causes some effects on these minima times. Comparing the chromospheric activity patterns with the analogues of the secondary component, it is seen that the magnetic activity level is remarkably low. However, it is still at the expected level according to the B-V color index of 0.643 mag for the secondary component.

SLIPPING MAGNETIC RECONNECTIONS WITH MULTIPLE FLARE RIBBONS DURING AN X-CLASS SOLAR FLARE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Ruisheng; Chen, Yao; Wang, Bing, E-mail: ruishengzheng@sdu.edu.cn

2016-06-01

With the observations of the Solar Dynamics Observatory , we present the slipping magnetic reconnections with multiple flare ribbons (FRs) during an X1.2 eruptive flare on 2014 January 7. A center negative polarity was surrounded by several positive ones, and three FRs appeared. The three FRs showed apparent slipping motions, and hook structures formed at their ends. Due to the moving footpoints of the erupting structures, one tight semi-circular hook disappeared after the slippage along its inner and outer edges, and coronal dimmings formed within the hook. The east hook also faded as a result of the magnetic reconnection betweenmore » the arcades of a remote filament and a hot loop that was impulsively heated by the under flare loops. Our results are accordant with the slipping magnetic reconnection regime in three-dimensional standard model for eruptive flares. We suggest that the complex structures of the flare are likely a consequence of the more complex flux distribution in the photosphere, and the eruption involves at least two magnetic reconnections.« less

Flares in Biopsy-Proven Giant Cell Arteritis in Northern Italy

PubMed Central

Restuccia, Giovanna; Boiardi, Luigi; Cavazza, Alberto; Catanoso, Mariagrazia; Macchioni, Pierluigi; Muratore, Francesco; Cimino, Luca; Aldigeri, Raffaella; Crescentini, Filippo; Pipitone, Nicolò; Salvarani, Carlo

2016-01-01

Abstract This study evaluated the frequency, timing, and characteristics of flares in a large cohort of Italian patients with biopsy-proven giant cell arteritis (GCA) and to identify factors at diagnosis able to predict the occurrence of flares. We evaluated 157 patients with biopsy-proven transmural GCA diagnosed and followed at the Rheumatology Unit of Reggio Emilia Hospital (Italy) for whom sufficient information was available from the time of diagnosis until at least 4 years of follow-up. Fifty-seven patients (36.5%) experienced ≥1 flares. Fifty-one (46.4%) of the 110 total flares (88 relapses and 22 recurrences) were experienced during the first 2 years after diagnosis. The majority of relapses occurred with doses of prednisone ≤ 10 mg/day (82.9%), whereas only 3.4% of relapses occurred for doses ≥ 25 mg/day. Polymyalgia rheumatica (46.5%) and cranial symptoms (41.9%) were the most frequent manifestations at the time of the first relapse. Cumulative prednisone dose during the first year and total cumulative prednisone dose were significantly higher in flaring patients compared with those without flares (7.8 ± 2.4 vs 6.7 ± 2.4 g, P = 0.02; 15.5 ± 8.9 vs 10.0 ± 9.2 g, P = 0.0001, respectively). The total duration of prednisone treatment was longer in flaring patients (58 ± 44 vs 30 ± 30 months, P = 0.0001). Patients with disease flares had at diagnosis more frequently systemic manifestations (P = 0.02) and fever ≥ 38°C (P = 0.02), significantly lower hemoglobin levels (P = 0.05), more frequent presence at temporal artery biopsy (TAB) specimens of giant cells (P = 0.04) and intraluminal acute thrombosis (P = 0.007), and more moderate/severe arterial inflammation (P = 0.009) compared with those without flares. In the multivariate model fever ≥ 38 °C (hazard ratio 2.14; 95% confidence interval, 1.06–4.32, P = 0.03) and the severity of inflammatory infiltrate (moderate/severe versus mild) (hazard ratio 5.41; 95% confidence interval, 1.64–17.87, P = 0.006) were significantly associated with an increased risk of flares. In conclusion, a flaring course is common in GCA and it is associated with prolonged GC requirements. Fever at diagnosis and severity of inflammation at TAB appear to predict the development of disease flares. PMID:27175649

Effect of engine shroud configuration on the static aerodynamic characteristics of a 0.00563 scale 142-inch diameter solid rocket booster (SA10F)

NASA Technical Reports Server (NTRS)

Johnson, J. D.; Braddock, W. F.

1974-01-01

A test of a 0.563 percent scale space shuttle Solid Rocket Booster (SRB) model, MSFC Model 449, was conducted in a trisonic wind tunnel. Test Mach numbers were 0.4, 0.6, 0.9, 1.2, 1.96, 3.48, 4.0, 4.45, and 4.96. Test angles-of-attack ranged from minus 10 degrees to 190 degrees. Test Reynolds numbers ranged from 3.0 million per foot to 8.6 million per foot. Test roll angles were 0, 11.25, 22.5, 45, and 90 degrees. In addition to the static stability evaluation of the primary SRB configuration, five parametric investigations were made: (1) effect of Reynolds number, (2) effect of engine shroud flare angle, (3) effect of engine shroud length, (4) effect of engine shroud strakes, and (5) effect of engine shroud strakes and trust vector control bottles.

Modeling Flare Hard X-ray Emission from Electrons in Contracting Magnetic Islands

NASA Astrophysics Data System (ADS)

Guidoni, Silvina E.; Allred, Joel C.; Alaoui, Meriem; Holman, Gordon D.; DeVore, C. Richard; Karpen, Judith T.

2016-05-01

The mechanism that accelerates particles to the energies required to produce the observed impulsive hard X-ray emission in solar flares is not well understood. It is generally accepted that this emission is produced by a non-thermal beam of electrons that collides with the ambient ions as the beam propagates from the top of a flare loop to its footpoints. Most current models that investigate this transport assume an injected beam with an initial energy spectrum inferred from observed hard X-ray spectra, usually a power law with a low-energy cutoff. In our previous work (Guidoni et al. 2016), we proposed an analytical method to estimate particle energy gain in contracting, large-scale, 2.5-dimensional magnetic islands, based on a kinetic model by Drake et al. (2010). We applied this method to sunward-moving islands formed high in the corona during fast reconnection in a simulated eruptive flare. The overarching purpose of the present work is to test this proposed acceleration model by estimating the hard X-ray flux resulting from its predicted accelerated-particle distribution functions. To do so, we have coupled our model to a unified computational framework that simulates the propagation of an injected beam as it deposits energy and momentum along its way (Allred et al. 2015). This framework includes the effects of radiative transfer and return currents, necessary to estimate flare emission that can be compared directly to observations. We will present preliminary results of the coupling between these models.

A significant hardening and rising shape detected in the MeV/GeV νF ν spectrum from the recently discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Yasuyuki T.; Becerra Gonzalez, Josefa; Itoh, Ryosuke

2016-05-23

In this paper, we report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently discovered very-high-energy (VHE, E > 100 GeV) blazar S4 0954+65 (z = 0.368) during an exceptionally bright optical flare in 2015 February. During the time period (2015 February 13/14, or MJD 57067) when the MAGIC telescope detected VHE γ-ray emission from the source, the Fermi-LAT data indicated a significant spectral hardening at GeV energies, with a power-law photon index of 1.8 ± 0.1—compared with the 3FGL (The Fermi LAT 4-Year Point Source Catalog) value (averaged over four years of observation) of 2.34 ±more » 0.04. In contrast, Swift X-Ray Telescope data showed a softening of the X-ray spectrum, with a photon index of 1.72 ± 0.08 (compared with 1.38 ± 0.03 averaged during the flare from MJD 57066 to 57077), possibly indicating a modest contribution of synchrotron photons by the highest-energy electrons superposed on the inverse Compton component. Fitting of the quasi-simultaneous (<1 d) broad-band spectrum with a one-zone synchrotron plus inverse-Compton model revealed that GeV/TeV emission could be produced by inverse-Compton scattering of external photons from the dust torus. Finally, we emphasize that a flaring blazar showing high flux of ≳1.0 × 10 -6 photons cm -2s -1 (E > 100 MeV) and a hard spectral index of ΓGeV < 2.0 detected by Fermi-LAT on daily timescales is a promising target for TeV follow-up by ground-based Cherenkov telescopes to discover high-redshift blazars, investigate their temporal variability and spectral features in the VHE band, and also constrain the intensity of the extragalactic background light.« less

Multiwavelength study of the flaring activity of Sagittarius A* in 2014 February-April

NASA Astrophysics Data System (ADS)

Mossoux, E.; Grosso, N.; Bushouse, H.; Eckart, A.; Yusef-Zadeh, F.; Plambeck, D.; Peissker, F.; Valencia-S., M.; Porquet, D.; Roberts, D.

2017-10-01

We studied the flaring activity of the Galactic Center supermassive black hole Sgr A* close to the DSO/G2 pericenter passage with XMM-Newton, HST/WFC3, VLT/SINFONI, VLA and CARMA. We detected 3 and 2 NIR and 2 X-ray flares with HST, VLT and XMM-Newton, respectively. The Mar. 10 X-ray flare has a long rise and a rapid decay. Its NIR counterpart peaked before the X-ray peak implying a variation in the X-ray-to-NIR flux ratio. This flare may be one flare created by the adiabatic compression of a plasmon or 2 close flares with simultaneous X-ray/NIR peaks. The rising radio flux-density observed on Mar. 10 with the VLA could be the delayed emission from a NIR/X-ray flare preceding our observations. On Apr. 2, we observed the start of the NIR counterpart of the X-ray flare and the end of a bright NIR flare without X-ray counterpart. We studied the physical parameters of the flaring region for each NIR flare but none of the radiative processes can be ruled out for the X-ray flares creation. Our X-ray flaring rate is consistent with those observed in the 2012 Chandra/XVP campaign. No increase in the flaring activity was thus triggered close to the DSO/G2 pericenter passage.

Fusobacterium nucleatum in endodontic flare-ups.

PubMed

Chávez de Paz Villanueva, Luis Eduardo

2002-02-01

The extent to which Fusobacterium nucleatum is recovered from root canals of teeth that present with an interappointment flare-up following endodontic instrumentation was investigated. Included in the study were 28 patients that sought emergency treatment after initiation of root canal therapy. Only non-painful teeth that had been treated because of a necrotic pulp and periapical inflammatory lesion were studied. Root canal samples for bacterial analysis were taken, transported to a bacteriological laboratory, and processed for a semiquantitative assessment of bacterial isolates. Bacterial findings were correlated with self-assessed pain intensity as recorded by means of a Visual Analogue Scale. Clinical presentation of swelling and presence of exudate in the treated root canals were also linked. Bacteria were recovered from all teeth examined. Gram-negative anaerobic coccoid rods (Prevotella species and Porphyromonas species) were frequent isolates. All teeth in patients who were reported to be in severe pain (Visual Analogue Scale > or = 6) displayed F nucleatum. Nine out of 10 of these teeth also had swelling and exudate in the root canals. Samples from the remaining patients that had teeth with less pain score showed a variable bacterial recovery. None of these teeth displayed F nucleatum. F nucleatum appears to be associated with the development of the most severe forms of interappointment endodontic flare-ups.

Dynamic Spectral Imaging of Decimetric Fiber Bursts in an Eruptive Solar Flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhitao; Chen, Bin; Gary, Dale E., E-mail: zw56@njit.edu

Fiber bursts are a type of fine structure that is often superposed on type IV radio continuum emission during solar flares. Although studied for many decades, its physical exciter, emission mechanism, and association with the flare energy release remain unclear, partly due to the lack of simultaneous imaging observations. We report the first dynamic spectroscopic imaging observations of decimetric fiber bursts, which occurred during the rise phase of a long-duration eruptive flare on 2012 March 3, as obtained by the Karl G. Jansky Very Large Array in 1–2 GHz. Our results show that the fiber sources are located near andmore » above one footpoint of the flare loops. The fiber source and the background continuum source are found to be co-spatial and share the same morphology. It is likely that they are associated with nonthermal electrons trapped in the converging magnetic fields near the footpoint, as supported by a persistent coronal hard X-ray source present during the flare rise phase. We analyze three groups of fiber bursts in detail with dynamic imaging spectroscopy and obtain their mean frequency-dependent centroid trajectories in projection. By using a barometric density model and magnetic field based on a potential field extrapolation, we further reconstruct the 3D source trajectories of fiber bursts, for comparison with expectations from the whistler wave model and two MHD-based models. We conclude that the observed fiber burst properties are consistent with an exciter moving at the propagation velocity expected for whistler waves, or models that posit similar exciter velocities.« less

Fearsome Flashes: A Study Of The Evolution Of Flaring Rates In Cool Stars Using Kepler Cluster Data

NASA Astrophysics Data System (ADS)

Saar, Steven

Strong solar flares can damage power grids, satellites, interrupt communications and GPS information, and threaten astronauts and high latitude air travelers. Despite the potential cost, their frequency is poorly determined. Beyond purely current terrestrial concerns, how the rate of large flares (and associated coronal mass ejections [CMEs], high-energy particle fluxes and far UV emission) varies over the stellar lifetime holds considerable astrophysical interest. These include: the contributions of flares to coronal energy budgets; the importance of flares and CMEs to terrestrial and exoplanet atmospheric and biological evolution; and importance of CME mass loss for angular momentum evolution. We will explore the rate of strong flares and its variation with stellar age, mass and rotation by studying Kepler data of cool stars in two open clusters NGC 6811 (age ~ 1 Gyr) and NGC 6819 (~2.5 Gyr). We will use two flare analysis methods to build white-light flare distributions for cluster stars. One subtracts a low-pass filtered version of the data and analyzes the residue for positive flux deviations, the other does a statistical analysis of the flux deviations vs. time lags compared with a model. For near- solar stars, a known solar relation can then be used to estimate X-ray production by the white-light flares. For stars much hotter or cooler or with significantly different chromospheric density, we will use particle code flare models including bombardment effects to estimate how the X-ray to white light scaling changes. With the X-ray values, we can estimate far UV fluxes and CME rates, building a picture of the flare effects; with the two cluster ages, we can make a first estimate of the solar rate (by projecting to the Sun's age) and begin to build up an understanding of flare rate evolution with mass and age. Our proposal falls squarely in the "Stellar Astrophysics and Exoplanets" research area, and is relevant to NASA astrophysics goals in promoting better understanding the evolution of stars and their exoplanets, and better understanding the environment in which life evolved, and threats to it, both on Earth and in the wider cosmos.

On the relation between the peak frequency and the corresponding rise time of solar microwave impulsive bursts and the height dependence of magnetic fields

NASA Astrophysics Data System (ADS)

Zhao, Ren-Yang; Magun, Andreas; Schanda, Erwin

1990-12-01

Results are reported from a correlation analysis for 57 microwave impulsive bursts observed at six frequencies. A regression line between the peak frequency and the corresponding rise time of microwave impulsive bursts is obtained, with a correlation coefficient of -0.43. This can be explained in the frame of a thermal model. The magnetic field decrease with height has to be much slower than in a dipole field in order to explain the weak dependence of f(p) on t(r). This decrease of magnetic field with height in burst sources is based on the relationship between f(p) and t(r) found by assuming a thermal flare model with a collisionless conduction front.

Observations and analysis of NOAA AR 11429 at KSU-Astronomical Observatory

NASA Astrophysics Data System (ADS)

Elmhamdi, Abouazza; Kordi, A. S.; Al-Trabulsy, H. A.; El-Nawawy, M.; Ibrahim, A. A.; Ben Nessib, N.; Abdel-Sabour, M. A.; Al-Mostafa, Z. A.

2013-10-01

We study the evolution of the sunspots in the recent super active region NOAA 11429, which spawned a powerful X5.4/3B flare on March 07, 2012 (2nd on record occurred since 2010), associated with a wide and fast Coronal Mass Ejection (CME; Halo/070036) and a large proton flux event (6530 p.f.u). The sunspot group consists a rare example of "Island Delta" in βγδ- magnetic configuration. This active region dominated the Solar activities on the northern hemisphere during the period March 03-15, 2012, of the present Solar Cycle 24, erupting 2 X-class flares, 13 M-class flares, and about 32 C-class flares. We analyze white-light images, wavelengths around 540 nm, observed at the Astronomical Observatory of King Saud University (AOKSU). The observations are part of a campaign conducted locally since early 2012, for monitoring Solar activities on a daily basis. The observations and data reduction are presented and discussed. We examine the main properties of AR 11429 (i.e. structure, growth and decay) by computing its daily "area" and "tilt- & trend-" angles, and infer information about its development and dynamics. The area curve is found to show three distinguishable phases, nicely fitted adopting double-Gaussian distribution. A close relation between sunspot group area and tilt-angle with the major March 07 powerful flare can be noticed from the current results, that certainly necessitates deep and careful inspections through studying large sample of events. The follow-up of the sunspot group the period it inhabits the Solar photosphere, permits exploiting the proper motion of four long-lived individual spots, as well as tracing the local surface differential rotation, found to be consistent with empirical results.

40 CFR 264.1033 - Standards: Closed-vent systems and control devices.

Code of Federal Regulations, 2012 CFR

2012-07-01

... § 264.1035(b)(4)(iii)(F). (h) An owner or operator using a carbon adsorption system such as a carbon...). (iii) A steam-assisted or nonassisted flare designed for and operated with an exit velocity, as... established as a requirement of § 264.1035(b)(4)(iii)(G), whichever is longer. (2) Replace the existing carbon...

40 CFR 264.1033 - Standards: Closed-vent systems and control devices.

Code of Federal Regulations, 2014 CFR

2014-07-01

... § 264.1035(b)(4)(iii)(F). (h) An owner or operator using a carbon adsorption system such as a carbon...). (iii) A steam-assisted or nonassisted flare designed for and operated with an exit velocity, as... established as a requirement of § 264.1035(b)(4)(iii)(G), whichever is longer. (2) Replace the existing carbon...

40 CFR 264.1033 - Standards: Closed-vent systems and control devices.

Code of Federal Regulations, 2013 CFR

2013-07-01

... § 264.1035(b)(4)(iii)(F). (h) An owner or operator using a carbon adsorption system such as a carbon...). (iii) A steam-assisted or nonassisted flare designed for and operated with an exit velocity, as... established as a requirement of § 264.1035(b)(4)(iii)(G), whichever is longer. (2) Replace the existing carbon...

The energy spectra of solar flare electrons

NASA Technical Reports Server (NTRS)

Evenson, P. A.; Hovestadt, D.; Meyer, P.; Moses, D.

1985-01-01

A survey of 50 electron energy spectra from .1 to 100 MeV originating from solar flares was made by the combination of data from two spectrometers onboard the International Sun Earth Explorer-3 spacecraft. The observed spectral shapes of flare events can be divided into two classes through the criteria of fit to an acceleration model. This standard two step acceleration model, which fits the spectral shape of the first class of flares, involves an impulsive step that accelerates particles up to 100 keV and a second step that further accelerates these particles up to 100 MeV by a single shock. This fit fails for the second class of flares that can be characterized as having excessively hard spectra above 1 MeV relative to the predictions of the model. Correlations with soft X-ray and meter radio observations imply that the acceleration of the high energy particles in the second class of flares is dominated by the impulsive phase of the flares.

The excitation of helium resonance lines in solar flares

NASA Technical Reports Server (NTRS)

Porter, J. G.; Gebbie, K. B.; November, L. J.

1985-01-01

Helium resonance line intensities are calculated for a set of six flare models corresponding to two rates of heating and three widely varying incident fluxes of soft X-rays. The differing ionization and excitation equilibria produced by these models, the processes which dominate the various cases, and the predicted helium line spectra are examined. The line intensities and their ratios are compared with values derived from Skylab NRL spectroheliograms for a class M flare, thus determining which of these models most nearly represents the density vs temperature structure and soft X-ray flux in the flaring solar transition region, and the temperature and dominant mechanaism of formation of the helium line spectrum during a flare.

Energy Intensity and Greenhouse Gas Emissions from Tight Oil Production in the Bakken Formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, Adam R.; Yeskoo, Tim; McNally, Michael S.

The Bakken formation has contributed to the recent rapid increase in U.S. oil production, reaching a peak production of >1.2 × 106 barrels per day in early 2015. In this study, we estimate the energy intensity and greenhouse gas (GHG) emissions from 7271 Bakken wells drilled from 2006 to 2013. We model energy use and emissions using the Oil Production Greenhouse Gas Emissions Estimator (OPGEE) model, supplemented with an open-source drilling and fracturing model, GHGfrack. Overall well-to-refinery-gate (WTR) consumption of natural gas, diesel, and electricity represent 1.3%, 0.2%, and 0.005% of produced crude energy content, respectively. Fugitive emissions are modeledmore » for a “typical” Bakken well using previously published results of atmospheric measurements. Flaring is a key driver of emissions: wells that flared in 2013 had a mean flaring rate that was ≈500 standard cubic feet per barrel or ≈14% of the energy content of the produced crude oil. Resulting production-weighted mean GHG emissions in 2013 were 10.2 g of CO2 equivalent GHGs per megajoule (henceforth, gCO2eq/MJ) of crude. Between-well variability gives a 5–95% range of 2–28 gCO2eq/MJ. If flaring is completely controlled, Bakken crude compares favorably to conventional U.S. crude oil, with 2013 emissions of 3.5 gCO2eq/MJ for nonflaring wells, compared to the U.S. mean of ≈8 gCO2eq/MJ.« less

Neutrino Analysis of the 2010 September Crab Nebula Flare and Time-integrated Constraints on Neutrino Emission from the Crab Using IceCube

NASA Astrophysics Data System (ADS)

Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Altmann, D.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; BenZvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Brown, A. M.; Buitink, S.; Caballero-Mora, K. S.; Carson, M.; Chirkin, D.; Christy, B.; Clem, J.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; D'Agostino, M. V.; Danninger, M.; Daughhetee, J.; Davis, J. C.; De Clercq, C.; Demirörs, L.; Denger, T.; Depaepe, O.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Díaz-Vélez, J. C.; Dierckxsens, M.; Dreyer, J.; Dumm, J. P.; Ehrlich, R.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Foerster, M. M.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Gora, D.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gurtner, M.; Ha, C.; Hajismail, A.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Heinen, D.; Helbing, K.; Herquet, P.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Homeier, A.; Hoshina, K.; Hubert, D.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Joseph, J. M.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Krings, T.; Kroll, G.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Lafebre, S.; Laihem, K.; Landsman, H.; Larson, M. J.; Lauer, R.; Lünemann, J.; Madsen, J.; Majumdar, P.; Marotta, A.; Maruyama, R.; Mase, K.; Matis, H. S.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Middell, E.; Milke, N.; Miller, J.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nießen, P.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Ono, M.; Panknin, S.; Paul, L.; Pérez de los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Rizzo, A.; Rodrigues, J. P.; Roth, P.; Rothmaier, F.; Rott, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Schmidt, T.; Schönwald, A.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Slipak, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stephens, G.; Stezelberger, T.; Stokstad, R. G.; Stössl, A.; Stoyanov, S.; Strahler, E. A.; Straszheim, T.; Stür, M.; Sullivan, G. W.; Swillens, Q.; Taavola, H.; Taboada, I.; Tamburro, A.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Tosi, D.; Turčan, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, C.; Xu, X. W.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Zoll, M.

2012-01-01

We present the results of a search for high-energy muon neutrinos with the IceCube detector in coincidence with the Crab Nebula flare reported on 2010 September by various experiments. Due to the unusual flaring state of the otherwise steady source we performed a prompt analysis of the 79-string configuration data to search for neutrinos that might be emitted along with the observed γ-rays. We performed two different and complementary data selections of neutrino events in the time window of 10 days around the flare. One event selection is optimized for discovery of E -2 ν neutrino spectrum typical of first-order Fermi acceleration. A similar event selection has also been applied to the 40-string data to derive the time-integrated limits to the neutrino emission from the Crab. The other event selection was optimized for discovery of neutrino spectra with softer spectral index and TeV energy cutoffs as observed for various Galactic sources in γ-rays. The 90% confidence level (CL) best upper limits on the Crab flux during the 10 day flare are 4.73 × 10-11 cm-2 s-1 TeV-1 for an E -2 ν neutrino spectrum and 2.50 × 10-10 cm-2 s-1 TeV-1 for a softer neutrino spectra of E -2.7 ν, as indicated by Fermi measurements during the flare. In this paper, we also illustrate the impact of the time-integrated limit on the Crab neutrino steady emission. The limit obtained using 375.5 days of the 40-string configuration is compared to existing models of neutrino production from the Crab and its impact on astrophysical parameters is discussed. The most optimistic predictions of some models are already rejected by the IceCube neutrino telescope with more than 90% CL.

Modelling Public Security Operations: Analysis of the Effect of Key Social, Cognitive, and Informational Factors with Security System Relationship Configurations for Goal Achievement

DTIC Science & Technology

2012-12-01

of MARSEC 2 13 Causing a fire or explosion, conducting blasting or setting off fireworks , including setting a flare or other signalling device...or explosion, conducting blasting or setting off fireworks , including setting a flare or other signalling device without port approval X X X X X X...explosion, conducting blasting or setting off fireworks , including setting a flare or other signalling device without port approval X X X X X X X Non

SIMULTANEOUS IRIS AND HINODE/EIS OBSERVATIONS AND MODELING OF THE 2014 OCTOBER 27 X2.0 CLASS FLARE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polito, V.; Reep, J. W.; Del Zanna, G.

We present a study of the X2-class flare which occurred on 2014 October 27 and was observed with the Interface Region Imaging Spectrograph (IRIS) and the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. Thanks to the high cadence and spatial resolution of the IRIS and EIS instruments, we are able to compare simultaneous observations of the Fe xxi 1354.08 Å and Fe xxiii 263.77 Å high-temperature emission (≳10 MK) in the flare ribbon during the chromospheric evaporation phase. We find that IRIS observes completely blueshifted Fe xxi line profiles, up to 200 km s{sup −1} during the rise phase of the flare, indicatingmore » that the site of the plasma upflows is resolved by IRIS. In contrast, the Fe xxiii line is often asymmetric, which we interpret as being due to the lower spatial resolution of EIS. Temperature estimates from SDO/AIA and Hinode/XRT show that hot emission (log(T[K]) > 7.2) is first concentrated at the footpoints before filling the loops. Density-sensitive lines from IRIS and EIS give estimates of electron number density of ≳10{sup 12} cm{sup −3} in the transition region lines and 10{sup 10} cm{sup −3} in the coronal lines during the impulsive phase. In order to compare the observational results against theoretical predictions, we have run a simulation of a flare loop undergoing heating using the HYDRAD 1D hydro code. We find that the simulated plasma parameters are close to the observed values that are obtained with IRIS, Hinode, and AIA. These results support an electron beam heating model rather than a purely thermal conduction model as the driving mechanism for this flare.« less

Global Energetics of Solar Flares. V. Energy Closure in Flares and Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.; Caspi, Amir; Cohen, Christina M. S.; Holman, Gordon; Jing, Ju; Kretzschmar, Matthieu; Kontar, Eduard P.; McTiernan, James M.; Mewaldt, Richard A.; O'Flannagain, Aidan; Richardson, Ian G.; Ryan, Daniel; Warren, Harry P.; Xu, Yan

2017-02-01

In this study we synthesize the results of four previous studies on the global energetics of solar flares and associated coronal mass ejections (CMEs), which include magnetic, thermal, nonthermal, and CME energies in 399 solar M- and X-class flare events observed during the first 3.5 yr of the Solar Dynamics Observatory (SDO) mission. Our findings are as follows. (1) The sum of the mean nonthermal energy of flare-accelerated particles ({E}{nt}), the energy of direct heating ({E}{dir}), and the energy in CMEs ({E}{CME}), which are the primary energy dissipation processes in a flare, is found to have a ratio of ({E}{nt}+{E}{dir}+{E}{CME})/{E}{mag}=0.87+/- 0.18, compared with the dissipated magnetic free energy {E}{mag}, which confirms energy closure within the measurement uncertainties and corroborates the magnetic origin of flares and CMEs. (2) The energy partition of the dissipated magnetic free energy is: 0.51 ± 0.17 in nonthermal energy of ≥slant 6 {keV} electrons, 0.17 ± 0.17 in nonthermal ≥slant 1 {MeV} ions, 0.07 ± 0.14 in CMEs, and 0.07 ± 0.17 in direct heating. (3) The thermal energy is almost always less than the nonthermal energy, which is consistent with the thick-target model. (4) The bolometric luminosity in white-light flares is comparable to the thermal energy in soft X-rays (SXR). (5) Solar energetic particle events carry a fraction ≈ 0.03 of the CME energy, which is consistent with CME-driven shock acceleration. (6) The warm-target model predicts a lower limit of the low-energy cutoff at {e}c≈ 6 {keV}, based on the mean peak temperature of the differential emission measure of T e = 8.6 MK during flares. This work represents the first statistical study that establishes energy closure in solar flare/CME events.

A peculiar multiwavelength flare in the blazar 3C 454.3

DOE PAGES

Gupta, Alok C.; Mangalam, Arun; Wiita, Paul J.; ...

2017-08-14

The blazar 3C 454.3 exhibited a strong flare seen in γ-rays, X-rays and optical/near-infrared bands during 2009 December 3–12. Emission in the V and J bands rose more gradually than did the γ-rays and soft X-rays, though all peaked at nearly the same time. Optical polarization measurements showed dramatic changes during the flare, with a strong anticorrelation between optical flux and degree of polarization (which rose from ~3 to ~20 percent) during the declining phase of the flare. The flare was accompanied by large rapid swings in polarization angle of ~170°. This combination of behaviours appears to be unique. Wemore » have cm-band radio data during the same period but they show no correlation with variations at higher frequencies. Such peculiar behaviour may be explained using jet models incorporating fully relativistic effects with a dominant source region moving along a helical path or by a shock-in-jet model incorporating three-dimensional radiation transfer if there is a dominant helical magnetic field. We find that spectral energy distributions at different times during the flare can be fit using modified one-zone models where only the magnetic field strength and particle break frequencies and normalizations need change. An optical spectrum taken at nearly the same time provides an estimate for the central black hole mass of ~2.3 × 10 9 M ⊙. Furthermore, we also consider two weaker flares seen during the ~200 d span over which multiband data are available. In one of them, the V and J bands appear to lead the γ-ray and X-ray bands by a few days; in the other, all variations are simultaneous.« less

Solar Flare Termination shock and the Synthetic Fe XXI 1354.08 Å line

NASA Astrophysics Data System (ADS)

Guo, L.; Li, G.; Reeves, K.; Raymond, J. C.

2017-12-01

Solar flares are one of the most energetic phenomena occurred in the solar system. In the standard solar flare model, a fast mode shock, which is often referred to as the flare termination shock (TS), can exist above the loop-top source of hard X-ray emissions. The existence of the termination shock has been recently related to spectral hardening of flare hard X-ray spectrum at energies > 300 keV. Observations of the Fe XXI 1354.08 Å line during solar flares by the IRIS spacecraft have found significant redshift with >100 km/s, which is consistent with a reconnection downflow. The ability to identify such a redshift by IRIS is made possible by IRIS's high time resolution, high spatial resolution, high sensitivity and cadence spectral observations. The ability to identify such a redshift by IRIS suggests that one may be able to use IRIS observations to identify flare termination shocks. Using a MHD simulation to model magnetic reconnection of a solar flare and assuming the existence of a TS in the downflow of the reconnection plasma, we model the synthetic emission of the Fe XXI 1354.08 Å line in this work. We show that the existence of the TS in the solar flare may manifest itself from the Fe XXI 1354.08 Å line.

Soot and SO2 contribution to the supersites in the MILAGRO campaign from elevated flares in the Tula Refinery

NASA Astrophysics Data System (ADS)

Almanza, V. H.; Molina, L. T.; Sosa, G.

2012-11-01

This work presents a simulation of the plume trajectory emitted by flaring activities of the Miguel Hidalgo Refinery in Mexico. The flame of a representative sour gas flare is modeled with a CFD combustion code in order to estimate emission rates of combustion by-products of interest for air quality: acetylene, ethylene, nitrogen oxides, carbon monoxide, soot and sulfur dioxide. The emission rates of NO2 and SO2 were compared with measurements obtained at Tula as part of MILAGRO field campaign. The rates of soot, VOCs and CO emissions were compared with estimates obtained by Instituto Mexicano del Petróleo (IMP). The emission rates of these species were further included in WRF-Chem model to simulate the chemical transport of the plume from 22 to 27 March of 2006. The model presents reliable performance of the resolved meteorology, with respect to the Mean Absolute Error (MAE), Root Mean Square Error (RMSE), mean bias (BIAS), vector RMSE and Index of Agreement (IOA). WRF-Chem outputs of SO2 and soot were compared with surface measurements obtained at the three supersites of MILAGRO campaign. The results suggest a contribution of Tula flaring activities to the total SO2 levels of 18% to 27% at the urban supersite (T0), and of 10% to 18% at the suburban supersite (T1). For soot, the model predicts low contribution at the three supersites, with less than 0.1% at three supersites. According to the model, the greatest contribution of both pollutants to the three supersites occurred on 23 March, which coincides with the third cold surge event reported during the campaign.

SWAP Observations of Post Flare Giant Arches and Evidence of Run-Away Reconnection

NASA Astrophysics Data System (ADS)

West, M. J.; Seaton, D. B.; Savage, S. L.

2016-12-01

It was recently established that post-flare giant arches and regular post-flare loops are generated in the same way, with post-flare giant arches undergoing sustained magnetic reconnection allowing them to grow to heights of approximately 400000 km (>0.5 solar-radii). In this presentation we discuss how reconnection can be sustained to such great heights, and the role the background corona plays in maintaining this growth. We use observations from 14 October 2014, when the SWAP EUV solar telescope on-board the PROBA2 spacecraft observed an eruption that led to the formation of perhaps the largest post-flare loop system seen in the solar corona in solar cycle 24. We combine these observations with those of RHESSI and LASCO, as well as using a forward model to assess the reconnection and loop deposition rate in the post-eruptive loop system.

Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares

NASA Technical Reports Server (NTRS)

Guidoni, S. E.; Devore, C. R.; Karpen, J. T.; Lynch, B. J.

2016-01-01

The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gains in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magneto hydro dynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.

Study of the effect of solar flares on the VLF signal during D layer disappearance time

NASA Astrophysics Data System (ADS)

Palit, Sourav; Chakrabarti, Sandip Kumar; Ray, Suman

We have modeled the effect of solar flare on the VLF signal during D layer disappearance time of the lower ionosphere by using the Monte Carlo simulation and a simple chemical scheme We have calculated the electron density profile during the flare using GEANT4 and the chemical model and put it as input to the LWPC to find the VLF amplitude variation due to the flare during the time when the D-layer is disappearing. We have compared the effect on the observed VLF signals with this model. We found that the long decay phase of a solar flare specially during the D-layer disappearance time causes the shifting of the sunset terminator times of VLF signals towards the nighttime. For observation we have taken the data for NWC-IERC propagation path. We have investigated the effect for different classes of flares.

Equatorial electrojet responses to intense solar flares under geomagnetic disturbance time electric fields

NASA Astrophysics Data System (ADS)

Abdu, M. A.; Nogueira, P. A. B.; Souza, J. R.; Batista, I. S.; Dutra, S. L. G.; Sobral, J. H. A.

2017-03-01

Large enhancement in the equatorial electrojet (EEJ) current can occur due to sudden increase in the E layer density arising from solar flare associated ionizing radiations, as also from background electric fields modified by magnetospheric disturbances when present before or during a solar flare. We investigate the EEJ responses at widely separated longitudes during two X-class flares that occurred at different activity phases surrounding the magnetic super storm sequences of 28-29 October 2003. During the 28 October flare we observed intense reverse electrojet under strong westward electric field in the sunrise sector over Jicamarca. Sources of westward disturbance electric fields driving large EEJ current are identified for the first time. Model calculations on the E layer density, with and without flare, and comparison of the results between Jicamarca and Sao Luis suggested enhanced westward electric field due to the flare occurring close to sunrise (over Jicamarca). During the flare on 29 October, which occurred during a rapid AE recovery, a strong overshielding electric field of westward polarity over Jicamarca delayed an expected EEJ eastward growth due to flare-induced ionization enhancement in the afternoon. This EEJ response yielded a measure of the overshielding decay time determined by the storm time Region 2 field-aligned current. This paper will present a detailed analysis of the EEJ responses during the two flares, including a quantitative evaluation of the flare-induced electron density enhancements and identification of electric field sources that played dominant roles in the large westward EEJ at the sunrise sector over Jicamarca.

Investigation of jet exhaust and local Mach number effects on the Solid Rocket Booster (SRB) base pressures (fa19)

NASA Technical Reports Server (NTRS)

Love, D. A.

1978-01-01

Two single nozzles with flare angles of 10 and 20 degrees were tested at Mach numbers of 0.5, 0.9, 1.2, 1.46, 1.96 and 3.48 in the presence of gaseous plumes. An attempt was made to determine the local Mach number above the flare by utilizing a pitot probe. This objective was only partially satisfied because the 20 degree flare separated the flow ahead of the flare for Mach numbers of 0.5 to 1.96. An accurate local Mach number could not be determined because of the separated flow. To meet the objective of a data base as a function of freestream Mach number, model surface and base pressures were obtained in the presence of gaseous plumes for a matrix of chamber pressures and temperatures at Mach numbers of 0.5, 0.9, 1.2, 1.46, 1.96 and 3.48.

The morphology of flare phenomena, magnetic fields, and electric currents in active regions. III - NOAA active region 6233 (1990 August)

NASA Technical Reports Server (NTRS)

De La Beaujardiere, J.-F.; Canfield, Richard C.; Leka, K. D.

1993-01-01

We investigate the spatial relationship between vertical electric currents and flare phenomena in NOAA Active Region 6233, which was observed 1990, August 28-31 at Mees Solar Observatory. The two flares studied are the 1N/M1.8 flare on August 28, 22:30 UT and the 1N/M1.6 flare on August 29, 20:35 UT. Using Stokes polarimetry we make magnetograms of the region and compute the vertical current density. Using H-alpha imaging spectroscopy we identify sites of intense nonthermal electron precipitation or of high coronal pressure. The precipitation in these flares is barely strong enough to be detectable. We find that both precipitation and high pressure tend to occur near vertical currents, but that neither phenomenon is cospatial with current maxima. In contrast with the conclusion of other authors, we argue that these observations do not support a current-interruption model for flares, unless the relevant currents are primarily horizontal. The magnetic morphology and temporal evolution of these flares suggest that an erupting filament model may be relevant, but this model does not explicitly predict the relationship between precipitation, high pressure, and vertical currents.

Slipping magnetic reconnection during an X-class solar flare observed by SDO/AIA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dudík, J.; Del Zanna, G.; Mason, H. E.

2014-04-01

We present SDO/AIA observations of an eruptive X-class flare of 2012 July 12, and compare its evolution with the predictions of a three-dimensional (3D) numerical simulation. We focus on the dynamics of flare loops that are seen to undergo slipping reconnection during the flare. In the Atmospheric Imaging Assembly (AIA) 131 Å observations, lower parts of 10 MK flare loops exhibit an apparent motion with velocities of several tens of km s{sup –1} along the developing flare ribbons. In the early stages of the flare, flare ribbons consist of compact, localized bright transition-region emission from the footpoints of the flaremore » loops. A differential emission measure analysis shows that the flare loops have temperatures up to the formation of Fe XXIV. A series of very long, S-shaped loops erupt, leading to a coronal mass ejection observed by STEREO. The observed dynamics are compared with the evolution of magnetic structures in the 'standard solar flare model in 3D.' This model matches the observations well, reproducing the apparently slipping flare loops, S-shaped erupting loops, and the evolution of flare ribbons. All of these processes are explained via 3D reconnection mechanisms resulting from the expansion of a torus-unstable flux rope. The AIA observations and the numerical model are complemented by radio observations showing a noise storm in the metric range. Dm-drifting pulsation structures occurring during the eruption indicate plasmoid ejection and enhancement of the reconnection rate. The bursty nature of radio emission shows that the slipping reconnection is still intermittent, although it is observed to persist for more than an hour.« less

Is the Universe More Transparent to Gamma Rays than Previously Thought?

NASA Technical Reports Server (NTRS)

Stecker, Floyd W.; Scully, Sean T.

2009-01-01

The MAGIC collaboration has recently reported the detection of the strong gamma-ray blazar 3C279 during a 1-2 day flare. They have used their spectral observations to draw conclusions regarding upper limits on the opacity of the Universe to high energy gamma-rays and, by implication, upper limits on the extragalactic mid-infrared background radiation. In this paper we examine the effect of gamma-ray absorption by the extragalactic infrared radiation on intrinsic spectra for this blazar and compare our results with the observational data on 3C279. We find agreement with our previous results, contrary to the recent assertion of the MAGIC group that the Universe is more transparent to gamma-rays than our calculations indicate. Our analysis indicates that in the energy range between approx. 80 and approx. 500 GeV, 3C279 has a best-fit intrinsic spectrum with a spectral index approx. 1.78 using our fast evolution model and approx. 2.19 using our baseline model. However, we also find that spectral indices in the range of 1.0 to 3.0 are almost as equally acceptable as the best fit spectral indices. Assuming the same intrinsic spectral index for this flare as for the 1991 flare from 3C279 observed by EGRET, viz., 2.02, which lies between our best fit indeces, we estimate that the MAGIC flare was approx.3 times brighter than the EGRET flare observed 15 years earlier.

Predictors of Flare Following Etanercept Withdrawal in Patients with Rheumatoid Factor-negative Juvenile Idiopathic Arthritis Who Reached Remission while Taking Medication.

PubMed

Aquilani, Angela; Pires Marafon, Denise; Marasco, Emiliano; Nicolai, Rebecca; Messia, Virginia; Perfetti, Francesca; Magni-Manzoni, Silvia; De Benedetti, Fabrizio

2018-05-01

To evaluate the rate of flare after etanercept (ETN) withdrawal in patients with juvenile idiopathic arthritis (JIA) who attained clinical remission while taking medication, and to identify predictors of flare. Patients were included with oligo- (oJIA) and rheumatoid factor-negative polyarticular JIA (pJIA) who received a first course of ETN for at least 18 months, maintained clinically inactive disease (CID) for at least 6 months during treatment, and were followed for 12 months after ETN withdrawal. Demographic and clinical features were collected at onset, at baseline (initiation of ETN), and at time of disease flare. After ETN withdrawal, 66 of the 110 patients enrolled (60%) flared with arthritis (of whom 7 flared with concurrent anterior uveitis; none with uveitis alone). The median time to flare was 4.3 months (interquartile range 2.5-6.4) with no evident differences between oJIA and pJIA. The number and type of joints involved at baseline and characteristics of ETN treatment/discontinuation were not associated with flare. Patients who flared were more frequently males (p = 0.034), positive for antinuclear antibody (ANA; p = 0.047), and had higher values of C-reactive protein (CRP; p = 0.012) at baseline. These variables remained significantly associated with flare in a multivariate logistic analysis, a model accounting for only 14% of the variability of the occurrence of the flare. Our results show that a significant proportion of patients with JIA who maintain CID for at least 6 months experience a relapse after ETN withdrawal. Male sex, presence of ANA, and elevated CRP at baseline were associated with higher risk of flare.

X-ray flare properties of Sgr A*

NASA Astrophysics Data System (ADS)

Wang, Daniel; Yuan, Qiang

2016-04-01

Daily X-ray flaring represents an enigmatic phenomenon of Sgr A* --- the supermassive black hole at the center of our Galaxy. We report results from a systematic X-ray study of this phenomenon, based on extensive Chandra observations obtained from 1999 to 2012, totaling about 4.5 Ms. We detect flares, using a combination of the maximum likelihood and Markov Chain Monte Carlo methods, which allow for a direct accounting for the pile-up effect in the modeling of the flare lightcurves and an optimal use of the data, as well as the measurements of flare parameters, including their uncertainties. A total of 82 flares are detected. About one third of them are relatively faint, which were not detected previously. The observation-to-observation variation of the quiescent emission has an average root-mean-square of 6%-14%, including the Poisson statistical fluctuation of faint flares below our detection limits. We find no significant long-term variation in the quiescent emission and the flare rate over the 14 years. In particular, we see no evidence of changing quiescent emission and flare rate around the pericenter passage of the S2 star around 2002. We show clear evidence of a short-term clustering for the flares on time scale of 20-70 ks. We will also report new results on the spectral and lightcurve properties of the flares, as well as their fluence-duration relation after carefully accounting for the detection incompleteness and bias. Finally, we will use these results to constrain the origin and emission mechanism of the flares, which further helps to establish Sgr A* as a unique laboratory to understand the astrophysics of prevailing low-luminosity black holes in the Universe.

The Flare Irradiance Spectral Model (FISM) and its Contributions to Space Weather Research, the Flare Energy Budget, and Instrument Design

NASA Technical Reports Server (NTRS)

Chamberlin, Phillip

2008-01-01

The Flare Irradiance Spectral Model (FISM) is an empirical model of the solar irradiance spectrum from 0.1 to 190 nm at 1 nm spectral resolution and on a 1-minute time cadence. The goal of FISM is to provide accurate solar spectral irradiances over the vacuum ultraviolet (VUV: 0-200 nm) range as input for ionospheric and thermospheric models. The seminar will begin with a brief overview of the FISM model, and also how the Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) will contribute to improving FISM. Some current studies will then be presented that use FISM estimations of the solar VUV irradiance to quantify the contributions of the increased irradiance from flares to Earth's increased thermospheric and ionospheric densites. Initial results will also be presented from a study looking at the electron density increases in the Martian atmosphere during a solar flare. Results will also be shown quantifying the VUV contributions to the total flare energy budget for both the impulsive and gradual phases of solar flares. Lastly, an example of how FISM can be used to simplify the design of future solar VUV irradiance instruments will be discussed, using the future NOAA GOES-R Extreme Ultraviolet and X-Ray Sensors (EXIS) space weather instrument.

New Evidence that CMEs are Self-Propelled Magnetic Bubbles

NASA Technical Reports Server (NTRS)

Moore, Ronald L.; Sterling, Alphonse C.; Seuss, Steven T.

2007-01-01

We briefly describe the "standard model" for the production of coronal mass ejections (CMEs), and our view of how it works. We then summarize pertinent recent results that we have found from SOHO observations of CMEs and the flares at the sources of these magnetic explosions. These results support our interpretation of the standard model: a CME is basically a self-propelled magnetic bubble, a low-beta plasmoitl, that (1) is built and unleashed by the tether-cutting reconnection that builds and heats the coronal flare arcade, (2) can explode from a flare site that is far from centered under the full-blown CME in the outer corona, and (3) drives itself out into the solar wind by pushing on the surrounding coronal magnetic field.

Reconstructing the 20th century high-resolution climate of the southeastern United States

NASA Astrophysics Data System (ADS)

Dinapoli, Steven M.; Misra, Vasubandhu

2012-10-01

We dynamically downscale the 20th Century Reanalysis (20CR) to a 10-km grid resolution from 1901 to 2008 over the southeastern United States and the Gulf of Mexico using the Regional Spectral Model. The downscaled data set, which we call theFlorida Climate Institute-Florida State University Land-Atmosphere Reanalysis for theSoutheastern United States at 10-km resolution (FLAReS1.0), will facilitate the study of the effects of low-frequency climate variability and major historical climate events on local hydrology and agriculture. To determine the suitability of the FLAReS1.0 downscaled data set for any subsequent applied climate studies, we compare the annual, seasonal, and diurnal variability of temperature and precipitation in the model to various observation data sets. In addition, we examine the model's depiction of several meteorological phenomena that affect the climate of the region, including extreme cold waves, summer sea breezes and associated convective activity, tropical cyclone landfalls, and midlatitude frontal systems. Our results show that temperature and precipitation variability are well-represented by FLAReS1.0 on most time scales, although systematic biases do exist in the data. FLAReS1.0 accurately portrays some of the major weather phenomena in the region, but the severity of extreme weather events is generally underestimated. The high resolution of FLAReS1.0 makes it more suitable for local climate studies than the coarser 20CR.

Global Energetics of Solar Flares. Part III; Nonthermal Energies

NASA Technical Reports Server (NTRS)

Aschwanden, Markus J.; Holman, Gordon; O'Flannagain, Aidan; Caspi, Amir; McTiernan, James M.; Kontar, Eduard P.

2016-01-01

This study entails the third part of a global flare energetics project, in which Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data of 191 M and X-class flare events from the first 3.5 years of the Solar Dynamics Observatory mission are analyzed. We fit a thermal and a nonthermal component to RHESSI spectra, yielding the temperature of the differential emission measure (DEM) tail, the nonthermal power-law slope and flux, and the thermal nonthermal cross-over energy eco. From these parameters, we calculate the total nonthermal energy E(sub nt) in electrons with two different methods: (1) using the observed cross-over energy e(sub co) as low-energy cutoff, and (2) using the low-energy cut off e(sub wt) predicted by the warm thick-target bremsstrahlung model of Kontar et al. Based on a mean temperature of T(sub e) = 8.6 MK in active regions, we find low-energy cutoff energies of e(sub wt) = 6.2 +/-1.6 keV for the warm-target model, which is significantly lower than the cross-over energies e(sub co) = 21 +/- 6 keV. Comparing with the statistics of magnetically dissipated energies E(sub mag) and thermal energies E(sub th) from the two previous studies, we find the following mean (logarithmic) energy ratios with the warm-target model: E(sub nt) = 0.41E(sub mag), E(sub th) = 0.08 E(sub mag), and E(sub th) = 0.15 E(sub nt). The total dissipated magnetic energy exceeds the thermal energy in 95% and the nonthermal energy in 71% of the flare events, which confirms that magnetic reconnection processes are sufficient to explain flare energies. The nonthermal energy exceeds the thermal energy in 85% of the events, which largely confirms the warm thick-target model.

Triggering Process of the X1.0 Three-ribbon Flare in the Great Active Region NOAA 12192

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bamba, Yumi; Inoue, Satoshi; Kusano, Kanya

The solar magnetic field in a flare-producing active region (AR) is much more complicated than theoretical models, which assume a very simple magnetic field structure. The X1.0 flare, which occurred in AR 12192 on 2014 October 25, showed a complicated three-ribbon structure. To clarify the trigger process of the flare and to evaluate the applicability of a simple theoretical model, we analyzed the data from Hinode /Solar Optical Telescope and the Solar Dynamics Observatory /Helioseismic and Magnetic Imager, Atmospheric Imaging Assembly. We investigated the spatio-temporal correlation between the magnetic field structures, especially the non-potentiality of the horizontal field, and themore » bright structures in the solar atmosphere. As a result, we determined that the western side of the positive polarity, which is intruding on a negative polarity region, is the location where the flare was triggered. This is due to the fact that the sign of the magnetic shear in that region was opposite that of the major shear of the AR, and the significant brightenings were observed over the polarity inversion line (PIL) in that region before flare onset. These features are consistent with the recently proposed flare-trigger model that suggests that small reversed shear (RS) magnetic disturbances can trigger solar flares. Moreover, we found that the RS field was located slightly off the flaring PIL, contrary to the theoretical prediction. We discuss the possibility of an extension of the RS model based on an extra numerical simulation. Our result suggests that the RS field has a certain flexibility for displacement from a highly sheared PIL, and that the RS field triggers more flares than we expected.« less

Energetics and dynamics of simple impulsive solar flares

NASA Technical Reports Server (NTRS)

Starr, R.; Heindl, W. A.; Crannell, C. J.; Thomas, R. J.; Batchelor, D. A.; Magun, A.

1987-01-01

Flare energetics and dynamics were studied using observations of simple impulsive spike bursts. A large, homogeneous set of events was selected to enable the most definite tests possible of competing flare models, in the absence of spatially resolved observations. The emission mechanisms and specific flare models that were considered in this investigation are described, and the derivations of the parameters that were tested are presented. Results of the correlation analysis between soft and hard X-ray energetics are also presented. The ion conduction front model and tests of that model with the well-observed spike bursts are described. Finally, conclusions drawn from this investigation and suggestions for future studies are discussed.

A Unified Computational Model for Solar and Stellar Flares

NASA Technical Reports Server (NTRS)

Allred, Joel C.; Kowalski, Adam F.; Carlsson, Mats

2015-01-01

We present a unified computational framework that can be used to describe impulsive flares on the Sun and on dMe stars. The models assume that the flare impulsive phase is caused by a beam of charged particles that is accelerated in the corona and propagates downward depositing energy and momentum along the way. This rapidly heats the lower stellar atmosphere causing it to explosively expand and dramatically brighten. Our models consist of flux tubes that extend from the sub-photosphere into the corona. We simulate how flare-accelerated charged particles propagate down one-dimensional flux tubes and heat the stellar atmosphere using the Fokker-Planck kinetic theory. Detailed radiative transfer is included so that model predictions can be directly compared with observations. The flux of flare-accelerated particles drives return currents which additionally heat the stellar atmosphere. These effects are also included in our models. We examine the impact of the flare-accelerated particle beams on model solar and dMe stellar atmospheres and perform parameter studies varying the injected particle energy spectra. We find the atmospheric response is strongly dependent on the accelerated particle cutoff energy and spectral index.

Global Energetics of Solar Flares. VI. Refined Energetics of Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.

2017-09-01

In this study, we refine the coronal mass ejection (CME) model that was presented in an earlier study of the global energetics of solar flares and associated CMEs and apply it to all (860) GOES M- and X-class flare events observed during the first seven years (2010-2016) of the Solar Dynamics Observatory (SDO) mission. The model refinements include (1) the CME geometry in terms of a 3D volume undergoing self-similar adiabatic expansion, (2) the solar gravitational deceleration during the propagation of the CME, which discriminates between eruptive and confined CMEs, (3) a self-consistent relationship between the CME center-of-mass motion detected during EUV dimming and the leading-edge motion observed in white-light coronagraphs, (4) the equipartition of the CME’s kinetic and thermal energies, and (5) the Rosner-Tucker-Vaiana scaling law. The refined CME model is entirely based on EUV-dimming observations (using Atmospheric Imager Assembly (AIA)/SDO data) and complements the traditional white-light scattering model (using Large-Angle and Spectrometric Coronagraph Experiment (LASCO)/Solar and Heliospheric Observatory data), and both models are independently capable of determining fundamental CME parameters. Comparing the two methods, we find that (1) LASCO is less sensitive than AIA in detecting CMEs (in 24% of the cases), (2) CME masses below {m}{cme}≲ {10}14 g are underestimated by LASCO, (3) AIA and LASCO masses, speeds, and energies agree closely in the statistical mean after the elimination of outliers, and (4) the CME parameters speed v, emission measure-weighted flare peak temperature T e , and length scale L are consistent with the following scaling laws: v\\propto {T}e1/2, v\\propto {({m}{cme})}1/4, and {m}{cme}\\propto {L}2.

40 CFR Table 3 to Subpart Ggggg of... - Applicability of General Provisions to Subpart GGGGG

Code of Federal Regulations, 2013 CFR

2013-07-01

.... Content of SSMP Yes with the exception of containers using either Level 1 or Level 2 controls. § 63.6(f)(1... performance test Yes. § 63.8(a)(1) Applicability of Monitoring Requirements Subject to all monitoring... of part 60 apply Yes. § 63.8(a)(3) [Reserved] § 63.8(a)(4) Monitoring with Flares Unless your rule...

40 CFR Table 3 to Subpart Ggggg of... - Applicability of General Provisions to Subpart GGGGG

Code of Federal Regulations, 2011 CFR

2011-07-01

.... Content of SSMP Yes with the exception of containers using either Level 1 or Level 2 controls. § 63.6(f)(1... performance test Yes. § 63.8(a)(1) Applicability of Monitoring Requirements Subject to all monitoring... of part 60 apply Yes. § 63.8(a)(3) [Reserved] § 63.8(a)(4) Monitoring with Flares Unless your rule...

40 CFR Table 3 to Subpart Ggggg of... - Applicability of General Provisions to Subpart GGGGG

Code of Federal Regulations, 2012 CFR

2012-07-01

.... Content of SSMP Yes with the exception of containers using either Level 1 or Level 2 controls. § 63.6(f)(1... performance test Yes. § 63.8(a)(1) Applicability of Monitoring Requirements Subject to all monitoring... of part 60 apply Yes. § 63.8(a)(3) [Reserved] § 63.8(a)(4) Monitoring with Flares Unless your rule...

VizieR Online Data Catalog: Bayesian method for detecting stellar flares (Pitkin+, 2014)

NASA Astrophysics Data System (ADS)

Pitkin, M.; Williams, D.; Fletcher, L.; Grant, S. D. T.

2015-05-01

We present a Bayesian-odds-ratio-based algorithm for detecting stellar flares in light-curve data. We assume flares are described by a model in which there is a rapid rise with a half-Gaussian profile, followed by an exponential decay. Our signal model also contains a polynomial background model required to fit underlying light-curve variations in the data, which could otherwise partially mimic a flare. We characterize the false alarm probability and efficiency of this method under the assumption that any unmodelled noise in the data is Gaussian, and compare it with a simpler thresholding method based on that used in Walkowicz et al. We find our method has a significant increase in detection efficiency for low signal-to-noise ratio (S/N) flares. For a conservative false alarm probability our method can detect 95 per cent of flares with S/N less than 20, as compared to S/N of 25 for the simpler method. We also test how well the assumption of Gaussian noise holds by applying the method to a selection of 'quiet' Kepler stars. As an example we have applied our method to a selection of stars in Kepler Quarter 1 data. The method finds 687 flaring stars with a total of 1873 flares after vetos have been applied. For these flares we have made preliminary characterizations of their durations and and S/N. (1 data file).

A Bayesian method for detecting stellar flares

NASA Astrophysics Data System (ADS)

Pitkin, M.; Williams, D.; Fletcher, L.; Grant, S. D. T.

2014-12-01

We present a Bayesian-odds-ratio-based algorithm for detecting stellar flares in light-curve data. We assume flares are described by a model in which there is a rapid rise with a half-Gaussian profile, followed by an exponential decay. Our signal model also contains a polynomial background model required to fit underlying light-curve variations in the data, which could otherwise partially mimic a flare. We characterize the false alarm probability and efficiency of this method under the assumption that any unmodelled noise in the data is Gaussian, and compare it with a simpler thresholding method based on that used in Walkowicz et al. We find our method has a significant increase in detection efficiency for low signal-to-noise ratio (S/N) flares. For a conservative false alarm probability our method can detect 95 per cent of flares with S/N less than 20, as compared to S/N of 25 for the simpler method. We also test how well the assumption of Gaussian noise holds by applying the method to a selection of `quiet' Kepler stars. As an example we have applied our method to a selection of stars in Kepler Quarter 1 data. The method finds 687 flaring stars with a total of 1873 flares after vetos have been applied. For these flares we have made preliminary characterizations of their durations and and S/N.

PREDICTING CORONAL MASS EJECTIONS USING MACHINE LEARNING METHODS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobra, M. G.; Ilonidis, S.

Of all the activity observed on the Sun, two of the most energetic events are flares and coronal mass ejections (CMEs). Usually, solar active regions that produce large flares will also produce a CME, but this is not always true. Despite advances in numerical modeling, it is still unclear which circumstances will produce a CME. Therefore, it is worthwhile to empirically determine which features distinguish flares associated with CMEs from flares that are not. At this time, no extensive study has used physically meaningful features of active regions to distinguish between these two populations. As such, we attempt to domore » so by using features derived from (1) photospheric vector magnetic field data taken by the Solar Dynamics Observatory ’s Helioseismic and Magnetic Imager instrument and (2) X-ray flux data from the Geostationary Operational Environmental Satellite’s X-ray Flux instrument. We build a catalog of active regions that either produced both a flare and a CME (the positive class) or simply a flare (the negative class). We then use machine-learning algorithms to (1) determine which features distinguish these two populations, and (2) forecast whether an active region that produces an M- or X-class flare will also produce a CME. We compute the True Skill Statistic, a forecast verification metric, and find that it is a relatively high value of ∼0.8 ± 0.2. We conclude that a combination of six parameters, which are all intensive in nature, will capture most of the relevant information contained in the photospheric magnetic field.« less

Recurring OH Flares towards o Ceti - I. Location and structure of the 1990s' and 2010s' events

NASA Astrophysics Data System (ADS)

Etoka, S.; Gérard, E.; Richards, A. M. S.; Engels, D.; Brand, J.; Le Bertre, T.

2017-06-01

We present the analysis of the onset of the new 2010s OH flaring event detected in the OH ground-state main line at 1665 MHz towards o Ceti and compare its characteristics with those of the 1990s' flaring event. This is based on a series of complementary single-dish and interferometric observations both in OH and H2O obtained with the Nançay Radio telescope, the Medicina and Effelsberg Telescopes, the European VLBI Network and (e)Multi-Element Radio Linked Interferometer Network. We compare the overall characteristics of o Ceti's flaring events with those that have been observed towards other thin-shell Miras, and explore the implication of these events with respect to the standard OH circumstellar-envelope model. The role of binarity in the specific characteristics of o Ceti's flaring events is also investigated. The flaring regions are found to be less than ˜400 ± 40 mas (I.e. ≤40 ± 4 au) either side of o Ceti, with seemingly no preferential location with respect to the direction to the companion Mira B. Contrary to the usual expectation that the OH maser zone is located outside the H2O maser zone, the coincidence of the H2O and OH maser velocities suggests that both emissions arise at similar distances from the star. The OH flaring characteristics of Mira are similar to those observed in various Mira variables before, supporting the earlier results that the regions where the transient OH maser emission occurs are different from the standard OH maser zone.

Nasal flaring as a clinical sign of respiratory acidosis in patients with dyspnea.

PubMed

Zorrilla-Riveiro, José Gregorio; Arnau-Bartés, Anna; Rafat-Sellarés, Ramón; García-Pérez, Dolors; Mas-Serra, Arantxa; Fernández-Fernández, Rafael

2017-04-01

To determine whether the presence of nasal flaring is a clinical sign of respiratory acidosis in patients attending emergency departments for acute dyspnea. Single-center, prospective, observational study of patients aged over 15 requiring urgent attention for dyspnea, classified as level II or III according to the Andorran Triage Program and who underwent arterial blood gas test on arrival at the emergency department. The presence of nasal flaring was evaluated by two observers. Demographic and clinical variables, signs of respiratory difficulty, vital signs, arterial blood gases and clinical outcome (hospitalization and mortality) were recorded. Bivariate and multivariate analyses were performed using logistic regression models. The sample comprised 212 patients, mean age 78years (SD=12.8), of whom 49.5% were women. Acidosis was recorded in 21.2%. Factors significantly associated with the presence of acidosis in the bivariate analysis were the need for pre-hospital medical care, triage level II, signs of respiratory distress, presence of nasal flaring, poor oxygenation, hypercapnia, low bicarbonates and greater need for noninvasive ventilation. Nasal flaring had a positive likelihood ratio for acidosis of 4.6 (95% CI 2.9-7.4). In the multivariate analysis, triage level II (aOR 5.16; 95% CI: 1.91 to 13.98), the need for oxygen therapy (aOR 2.60; 95% CI: 1.13-5.96) and presence of nasal flaring (aOR 6.32; 95% CI: 2.78-14.41) were maintained as factors independently associated with acidosis. Nasal flaring is a clinical sign of severity in patients requiring urgent care for acute dyspnea, which has a strong association with acidosis and hypercapnia. Copyright © 2016 Elsevier Inc. All rights reserved.

Space weather effects on the low latitude D-region ionosphere during solar minimum

NASA Astrophysics Data System (ADS)

Kumar, Abhikesh; Kumar, Sushil

2014-12-01

The effects of the solar flares and the geomagnetic storms (disturbance storm time ( Dst) < -50 nT) during December 2006 to 2008, a period during the unprecedented solar minimum of solar cycles 23 and 24, have been examined on sub-ionospheric very low frequency (VLF) signals from NWC (19.8 kHz), NPM (21.4 kHz), VTX (18.2 kHz), and NLK (24.8 kHz) transmitters monitored at Suva (18.2° S, 178.4° E), Fiji. Apart from the higher class solar flares (C to X), a solar flare of class B8.5 also produced enhancements both on the amplitude and phase. The amplitude enhancements in NLK, NPM, and NWC signals as a function of peak solar flare X-ray flux in decibel (dB; relative to 1 μW/m2) shows that the relationship curve is steeper and quite linear between the flare power levels of 0 to 15 dB; below 0 dB, the curve gets less steep and flattens towards -5 dB flare power level, while it also gets less steep above 15 dB and almost flattens above 20 dB. In general, the level of amplitude enhancement for NLK signal is higher than that for NPM and NWC signals for all solar flares. The enhancement in the amplitude and phase of VLF signals by solar flares is due to the increase in the D-region electron density by the solar flare-produced extra ionization. The modeling of VLF perturbations produced by B8.5 and C1.5 classes of solar flares on 29 January 2007 using LWPC (Long Wave Propagation Capability) V2.1 codes show that reflection height ( H') was reduced by 0.6 and 1.2 km and the exponential sharpness factor ( β) was raised by 0.010 and 0.005 km-1, respectively. Out of seven storms with Dst < -50 nT, only the intense storm of 14 to 16 December 2006 with a minimum Dst of -145 nT has shown a clear reduction in the signal strength of NWC and NPM sub-ionospheric signals due to storm-induced reduction in the D-region electron density.

Critical frequencies of the ionospheric F1 and F2 layers during the last four solar cycles: Sunspot group type dependencies

NASA Astrophysics Data System (ADS)

Yiǧit, Erdal; Kilcik, Ali; Elias, Ana Georgina; Dönmez, Burçin; Ozguc, Atila; Yurchshyn, Vasyl; Rozelot, Jean-Pierre

2018-06-01

The long term solar activity dependencies of ionospheric F1 and F2 regions' critical frequencies (f0F1 and f0F2) are analyzed for the last four solar cycles (1976-2015). We show that the ionospheric F1 and F2 regions have different solar activity dependencies in terms of the sunspot group (SG) numbers: F1 region critical frequency (f0F1) peaks at the same time with the small SG numbers, while the f0F2 reaches its maximum at the same time with the large SG numbers, especially during the solar cycle 23. The observed differences in the sensitivity of ionospheric critical frequencies to sunspot group (SG) numbers provide a new insight into the solar activity effects on the ionosphere and space weather. While the F1 layer is influenced by the slow solar wind, which is largely associated with small SGs, the ionospheric F2 layer is more sensitive to Coronal Mass Ejections (CMEs) and fast solar winds, which are mainly produced by large SGs and coronal holes. The SG numbers maximize during of peak of the solar cycle and the number of coronal holes peaks during the sunspot declining phase. During solar minimum there are relatively less large SGs, hence reduced CME and flare activity. These results provide a new perspective for assessing how the different regions of the ionosphere respond to space weather effects.

Hard X-ray and high-frequency decimetric radio observations of the 4 April 2002 solar flare

NASA Astrophysics Data System (ADS)

Kane, S. R.; Sawant, H. S.; Cecatto, J. R.; Andrade, M. C.; Fernandes, F. C. R.; Karlicky, M.; Meszarosova, H.

Hard X-ray and high frequency decimetric type III radio bursts have been observed in association with the soft X-raysolar flare (GOES class M 6.1) on 4 April 2002 (˜1532 UT). The flare apparently occurred ˜ 6 degrees behind the east limb of the Sun in the active region NOAA 9898. Hard X-ray spectra and images were obtained by the X-ray imager on RHESSI during the impulsive phase of the flare. The Brazilian Solar Spectroscope and Ondrejov Radio Telescopes recorded type III bursts in 800-1400 MHz range in association with the flare. The images of the 3-6, 6-12, 12-25, and 25-50 keV X-ray sources, obtained simultaneously by RHESSI during the early impulsive phase of the flare, show that all the four X-ray sources were essentially at the same location well above the limb of the Sun. During the early impulsive phase, the X-ray spectrum over 8-30 keV range was consistent with a power law with a negative exponent of ˜ 6. The radio spectra show drifting radio structures with emission in a relatively narrow (Δf ≤ 200 MHz) frequency range indicating injection of energetic electrons into a plasmoid which is slowly drifting upwards in the corona.

An interacting loop model of solar flare bursts

NASA Technical Reports Server (NTRS)

Emslie, A. G.

1981-01-01

As a result of the strong heating produced at chromospheric levels during a solar flare burst, the local gas pressure can transiently attain very large values in certain regions. The effectiveness of the surrounding magnetic field at confining this high pressure plasma is therefore reduced and the flaring loop becomes free to expand laterally. In so doing it may drive magnetic field lines into neighboring, nonflaring, loops in the same active region, causing magnetic reconnection to take place and triggering another flare burst. The features of this interacting loop model are found to be in good agreement with the energetics and time structure of flare associated solar hard X-ray bursts.

Peak-Flux-Density Spectra of Large Solar Radio Bursts and Proton Emission from Flares.

DTIC Science & Technology

1985-08-19

of the microwave peak (Z 1000 sfu in U-bursts) served as an indicator that the energy release during the impulsive phase was sufficient to produce a... energy or wave- length tends to be prominent in all, and cautions about over-interpreting associa- tions/correlations observed in samples of big flares...Sung, L. S., and McDonald, F. B. (1975) The variation of solar proton energy spectra and size distribution with helio- longitude, Sol. Phys. 41: 189. 28

Intermittent Flare Energy Release: A Signature of Contracting Magnetic Islands from Reconnection?

NASA Astrophysics Data System (ADS)

Guidoni, S. E.; Karpen, J. T.; DeVore, C.

2013-12-01

Many flares show short-lived enhancements of emission that protrude above their smooth underlying emission. These spikes have been observed over a vast energy spectrum, from radio to hard x-rays. In hard X-rays, for example, their duration ranges from 0.2 to 2 s, with the majority occurring during the flare impulsive phase (Cheng 2012). In most cases, this intermittent energy release is situated at the footpoints of flare arcades where ionized particles, previously accelerated to high energies at coronal heights, are decelerated by the dense solar surface. It is not yet understood what mechanisms accelerate ionized particles to the energies required to produce the observed emission spikes. Drake et al. (2006) proposed a kinetic mechanism for accelerating electrons from contracting magnetic islands that form as reconnection proceeds, analogous to the energy gain of a ball bouncing between converging walls. They estimated that multi-island regions of macroscopic dimensions might account for the required acceleration rates in flares, but at this time it is impractical to simulate large-scale systems in kinetic models. On the other hand, our recent high-resolution MHD simulations of a breakout eruptive flare (Karpen et al. 2012) allow us to resolve in detail the generation and evolution of macroscopic magnetic islands in a flare current sheet. Incorporating a rigorous kinetic model into our global simulations is not feasible at present. However, we intend to breach the gap between kinetic and fluid models by characterizing the contractions of islands as they move away from the main reconnection site, to determine their plausibility as candidates for the observed bursts of radiation. With our null-tracking capabilities, we follow the creation and evolution of the X- and O-type (island) nulls that result from spatially and temporally localized reconnection. Different regimes of current-sheet reconnection (slow/fast), island sizes, rates of island coalescence, and rates of reconnection between islands and arcades may help to explain the variety of energy and time scales exhibited by flare emission spikes. This research was supported, in part, by NASA's SR&T program and by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center administered by Oak Ridge Associated Universities through a contract with NASA.

On the relation between the peak frequency and the corresponding rise time of solar microwave impulsive bursts and the height dependence of magnetic fields

NASA Astrophysics Data System (ADS)

Ren-Yang, Zhao; Magun, Andreas; Schanda, Erwin

1990-12-01

In the present paper we report the results of a correlation analysis for 57 microwave impulsive bursts observed at six frequencies in which we have obtained a regression line between the peak frequency and the corresponding rise time of microwave impulsive bursts: {ie361-01} (with a correlation coefficient of - 0.43). This can be explained in the frame of a thermal model. The magnetic field decrease with height has to be much slower than in a dipole field in order to explain the weak dependence of f p on t r . This decrease of magnetic field with height in burst sources is based on the relationship between f p and t r found by assuming a thermal flare model with a collisionless conduction front.

Neutrino Analysis of the September 2010 Crab Nebula Flare and Time-Integrated Constraints on Neutrino Emission from the Crab Using IceCube

NASA Technical Reports Server (NTRS)

Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Adams, J.; Aguilar, A.; Ahlers, M.; Altmann; Andeen, K.; Auffenberg, J; Bai, X.;

Neutrino Analysis of the September 2010 Crab Nebula Flare and Time-integrated Constraints on Neutrino Emission From the Crab Using IceCube

NASA Technical Reports Server (NTRS)

Stamatikos, M.; Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Adams, J.; Aguliar, J. A.; Ahlers, M.; Altmann, D.; Andeen, K.; Auffenberg, J.;

A systematic Chandra study of Sgr A⋆ - I. X-ray flare detection

NASA Astrophysics Data System (ADS)

Yuan, Qiang; Wang, Q. Daniel

2016-02-01

Daily X-ray flaring represents an enigmatic phenomenon of Sagittarius A⋆ (Sgr A⋆) - the supermassive black hole at the centre of our Galaxy. We report initial results from a systematic X-ray study of this phenomenon, based on extensive Chandra observations obtained from 1999 to 2012, totalling about 4.5 Ms. We detect flares, using a combination of the maximum likelihood and Markov Chain Monte Carlo methods, which allow for a direct accounting for the pileup effect in the modelling of the flare light curves and an optimal use of the data, as well as the measurements of flare parameters, including their uncertainties. A total of 82 flares are detected. About one third of them are relatively faint, which were not detected previously. The observation-to-observation variation of the quiescent emission has an average root-mean-square of 6-14 per cent, including the Poisson statistical fluctuation of faint flares below our detection limits. We find no significant long-term variation in the quiescent emission and the flare rate over the 14 years. In particular, we see no evidence of changing quiescent emission and flare rate around the pericentre passage of the S2 star around 2002. We show clear evidence of a short-term clustering for the Advanced CCD Imaging Spectrometer - Spectroscopy array/high energy transmission gratings 0th-order flares on time-scale of 20-70 ks. We further conduct detailed simulations to characterize the detection incompleteness and bias, which is critical to a comprehensive follow-up statistical analysis of flare properties. These studies together will help to establish Sgr A⋆ as a unique laboratory to understand the astrophysics of prevailing low-luminosity black holes in the Universe.

Air pollution from gas flaring: new emission factor estimates and detection in a West African aerosol remote-sensing climatology

NASA Astrophysics Data System (ADS)

MacKenzie, Rob; Fawole, Olusegun Gabriel; Levine, James; Cai, Xiaoming

2016-04-01

Gas flaring, the disposal of gas through stacks in an open-air flame, is a common feature in the processing of crude oil, especially in oil-rich regions of the world. Gas flaring is a prominent source of volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAH), CO, CO2, nitrogen oxides (NOx), SO2 (in "sour" gas only), and soot (black carbon), as well as the release of locally significant amounts of heat. The rates of emission of these pollutants from gas flaring depend on a number of factors including, but not limited to, fuel composition and quantity, stack geometry, flame/combustion characteristics, and prevailing meteorological conditions. Here, we derive new estimated emission factors (EFs) for carbon-containing pollutants (excluding PAH). The air pollution dispersion model, ADMS5, is used to simulate the dispersion of the pollutants from flaring stacks in the Niger delta. A seasonal variation of the dispersion pattern of the pollutant within a year is studied in relation to the movements of the West Africa Monsoon (WAM) and other prevailing meteorological factors. Further, we have clustered AERONET aerosol signals using trajectory analysis to identify dominant aerosol sources at the Ilorin site in West Africa (4.34 oE, 8.32 oN). A 10-year trajectory-based analysis was undertaken (2005-2015, excluding 2010). Of particular interest are air masses that have passed through the gas flaring region in the Niger Delta area en-route the AERONET site. 7-day back trajectories were calculated using the UK Universities Global Atmospheric Modelling Programme (UGAMP) trajectory model which is driven by analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF). From the back-trajectory calculations, dominant sources are identified, using literature classifications: desert dust (DD); Biomass burning (BB); and Urban-Industrial (UI). We use a combination of synoptic trajectories and aerosol optical properties to distinguish a fourth source: that due to gas flaring. We discuss the relative impact of these different aerosol sources on the overall radiative forcing at Ilorin AERONET site.

Solar Flare Termination Shock and Synthetic Emission Line Profiles of the Fe xxi 1354.08 Å Line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Lijia; Li, Gang; Reeves, Kathy

Solar flares are among the most energetic phenomena that occur in the solar system. In the standard solar flare model, a fast mode shock, often referred to as the flare termination shock (TS), can exist above the loop-top source of hard X-ray emissions. The existence of the TS has been recently related to spectral hardening of a flare’s hard X-ray spectra at energies >300 keV. Observations of the Fe xxi 1354.08 Å line during solar flares by the Interface Region Imaging Spectrograph ( IRIS ) spacecraft have found significant redshifts with >100 km s{sup −1}, which is consistent with amore » reconnection downflow. The ability to detect such a redshift with IRIS suggests that one may be able to use IRIS observations to identify flare TSs. Using a magnetohydrodynamic simulation to model magnetic reconnection of a solar flare and assuming the existence of a TS in the downflow of the reconnection plasma, we model the synthetic emission of the Fe xxi 1354.08 line in this work. We show that the existence of the TS in the solar flare may manifest itself in the Fe xxi 1354.08 Å line.« less

A Parameter Study for Modeling Mg ii h and k Emission during Solar Flares

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubio da Costa, Fatima; Kleint, Lucia, E-mail: frubio@stanford.edu

2017-06-20

Solar flares show highly unusual spectra in which the thermodynamic conditions of the solar atmosphere are encoded. Current models are unable to fully reproduce the spectroscopic flare observations, especially the single-peaked spectral profiles of the Mg ii h and k lines. We aim to understand the formation of the chromospheric and optically thick Mg ii h and k lines in flares through radiative transfer calculations. We take a flare atmosphere obtained from a simulation with the radiative hydrodynamic code RADYN as input for a radiative transfer modeling with the RH code. By iteratively changing this model atmosphere and varying thermodynamicmore » parameters such as temperature, electron density, and velocity, we study their effects on the emergent intensity spectra. We reproduce the typical single-peaked Mg ii h and k flare spectral shape and approximate the intensity ratios to the subordinate Mg ii lines by increasing either densities, temperatures, or velocities at the line core formation height range. Additionally, by combining unresolved upflows and downflows up to ∼250 km s{sup −1} within one resolution element, we reproduce the widely broadened line wings. While we cannot unambiguously determine which mechanism dominates in flares, future modeling efforts should investigate unresolved components, additional heat dissipation, larger velocities, and higher densities and combine the analysis of multiple spectral lines.« less

Transition from eruptive to confined flares in the same active region

NASA Astrophysics Data System (ADS)

Zuccarello, F. P.; Chandra, R.; Schmieder, B.; Aulanier, G.; Joshi, R.

2017-05-01

Context. Solar flares are sudden and violent releases of magnetic energy in the solar atmosphere that can be divided into two classes: eruptive flares, where plasma is ejected from the solar atmosphere resulting in a coronal mass ejection (CME), and confined flares, where no CME is associated with the flare. Aims: We present a case study showing the evolution of key topological structures, such as spines and fans, which may determine the eruptive versus non-eruptive behavior of the series of eruptive flares followed by confined flares, which all originate from the same site. Methods: To study the connectivity of the different flux domains and their evolution, we compute a potential magnetic field model of the active region. Quasi-separatrix layers are retrieved from the magnetic field extrapolation. Results: The change in behavior of the flares from one day to the next - from eruptive to confined - can be attributed to the change in orientation of the magnetic field below the fan with respect to the orientation of the overlaying spine rather than an overall change in the stability of the large-scale field. Conclusions: Flares tend to be more confined when the field that supports the filament and the overlying field gradually becomes less anti-parallel as a direct result of changes in the photospheric flux distribution, being themselves driven by continuous shearing motions of the different magnetic flux concentrations. Movies associated to Figs. 2, 3, and 5 are available at http://www.aanda.org

Classification of Solar Flares

DTIC Science & Technology

1988-11-01

34proton flares," and flares which cause ground level effects are often called "GLE events" or " cosmic - ray flares." However, the term "proton flares...34 in general refers to both groups. Ellison et al (54) first noticed that cosmic - ray flares are typically two- ribbon flares, with two large Ha ribbons...atmosphere and combine with protons to produce deuterons and the 2.2 MeV gamma- ray line. Pions produced by nuclear interactions decay to muons , which in

HOW DID A MAJOR CONFINED FLARE OCCUR IN SUPER SOLAR ACTIVE REGION 12192?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Chaowei; Feng, Xueshang; Wu, S. T.

We study the physical mechanism of a major X-class solar flare that occurred in the super NOAA active region (AR) 12192 using data-driven numerical magnetohydrodynamic (MHD) modeling complemented with observations. With the evolving magnetic fields observed at the solar surface as bottom boundary input, we drive an MHD system to evolve self-consistently in correspondence with the realistic coronal evolution. During a two-day time interval, the modeled coronal field has been slowly stressed by the photospheric field evolution, which gradually created a large-scale coronal current sheet, i.e., a narrow layer with intense current, in the core of the AR. The currentmore » layer was successively enhanced until it became so thin that a tether-cutting reconnection between the sheared magnetic arcades was set in, which led to a flare. The modeled reconnecting field lines and their footpoints match well the observed hot flaring loops and the flare ribbons, respectively, suggesting that the model has successfully “reproduced” the macroscopic magnetic process of the flare. In particular, with simulation, we explained why this event is a confined eruption—the consequence of the reconnection is a shared arcade instead of a newly formed flux rope. We also found a much weaker magnetic implosion effect compared to many other X-class flares.« less

MAGNETIC-ISLAND CONTRACTION AND PARTICLE ACCELERATION IN SIMULATED ERUPTIVE SOLAR FLARES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guidoni, S. E.; DeVore, C. R.; Karpen, J. T.

The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gainsmore » in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magnetohydrodynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.« less

FLARE ENERGY BUILD-UP IN A DECAYING ACTIVE REGION NEAR A CORONAL HOLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su Yingna; Van Ballegooijen, Adriaan; Golub, Leon

2009-10-10

A B1.7 two-ribbon flare occurred in a highly non-potential decaying active region near a coronal hole at 10:00 UT on 2008 May 17. This flare is 'large' in the sense that it involves the entire region, and it is associated with both a filament eruption and a coronal mass ejection. We present multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays (Hinode/XRT), and Halpha (THEMIS, BBSO) prior to, during and after the flare. Prior to the flare, the region contained two filaments. The long J-shaped sheared loops corresponding to the southern filament were evolved from two short loop systems, which happened aroundmore » 22:00 UT after a filament eruption on May 16. Formation of highly sheared loops in the southeastern part of the region was observed by STEREO 8 hr before the flare. We also perform nonlinear force-free field (NLFFF) modeling for the region at two times prior to the flare, using the flux rope insertion method. The models include the non-force-free effect of magnetic buoyancy in the photosphere. The best-fit NLFFF models show good fit to observations both in the corona (X-ray and EUV loops) and chromosphere (Halpha filament). We find that the horizontal fields in the photosphere are relatively insensitive to the present of flux ropes in the corona. The axial flux of the flux rope in the NLFFF model on May 17 is twice that on May 16, and the model on May 17 is only marginally stable. We also find that the quasi-circular flare ribbons are associated with the separatrix between open and closed fields. This observation and NLFFF modeling suggest that this flare may be triggered by the reconnection at the null point on the separatrix surface.« less

Advances In Understanding Solar And Stellar Flares

NASA Astrophysics Data System (ADS)

Kowalski, Adam F.

2016-07-01

Flares result from the sudden reconnection and relaxation of magnetic fields in the coronae of stellar atmospheres. The highly dynamic atmospheric response produces radiation across the electromagnetic spectrum, from the radio to X-rays, on a range of timescales, from seconds to days. New high resolution data of solar flares have revealed the intrinsic spatial properties of the flaring chromosphere, which is thought to be where the majority of the flare energy is released as radiation in the optical and near-UV continua and emission lines. New data of stellar flares have revealed the detailed properties of the broadband (white-light) continuum emission, which provides straightforward constraints for models of the transformation of stored magnetic energy in the corona into thermal energy of the lower atmosphere. In this talk, we discuss the physical processes that produce several important spectral phenomena in the near-ultraviolet and optical as revealed from new radiative-hydrodynamic models of flares on the Sun and low mass stars. We present recent progress with high-flux nonthermal electron beams in reproducing the observed optical continuum color temperature of T 10,000 K and the Balmer jump properties in the near-ultraviolet. These beams produce dense, heated chromospheric condensations, which can explain the shape and strength of the continuum emission in M dwarf flares and the red-wing asymmetries in the chromospheric emission lines in recent observations of solar flares from the Interface Region Imaging Spectrograph. Current theoretical challenges and future modeling directions will be discussed, as well as observational synergies between solar and stellar flares.

The flare kernel in the impulsive phase

NASA Technical Reports Server (NTRS)

Dejager, C.

1986-01-01

The impulsive phase of a flare is characterized by impulsive bursts of X-ray and microwave radiation, related to impulsive footpoint heating up to 50 or 60 MK, by upward gas velocities (150 to 400 km/sec) and by a gradual increase of the flare's thermal energy content. These phenomena, as well as non-thermal effects, are all related to the impulsive energy injection into the flare. The available observations are also quantitatively consistent with a model in which energy is injected into the flare by beams of energetic electrons, causing ablation of chromospheric gas, followed by convective rise of gas. Thus, a hole is burned into the chromosphere; at the end of impulsive phase of an average flare the lower part of that hole is situated about 1800 km above the photosphere. H alpha and other optical and UV line emission is radiated by a thin layer (approx. 20 km) at the bottom of the flare kernel. The upward rising and outward streaming gas cools down by conduction in about 45 s. The non-thermal effects in the initial phase are due to curtailing of the energy distribution function by escape of energetic electrons. The single flux tube model of a flare does not fit with these observations; instead we propose the spaghetti-bundle model. Microwave and gamma-ray observations suggest the occurrence of dense flare knots of approx. 800 km diameter, and of high temperature. Future observations should concentrate on locating the microwave/gamma-ray sources, and on determining the kernel's fine structure and the related multi-loop structure of the flaring area.

ANTERIOR CHAMBER FLARE DURING BEVACIZUMAB TREATMENT IN EYES WITH EXUDATIVE AGE-RELATED MACULAR DEGENERATION.

PubMed

Hautamäki, Asta; Luoma, Arto; Immonen, Ilkka

2016-11-01

To study the anterior chamber flare during bevacizumab treatment of exudative age-related macular degeneration. During a 2-year prospective follow-up, 50 patients recently diagnosed with exudative age-related macular degeneration were treated at once-a-month visits if subretinal or intraretinal fluid or a new hemorrhage was present in the lesion area. Flare was measured weekly during the first month and then monthly in both eyes. Higher flare was associated with older age (P = 0.007, Linear Mixed Model), higher number of smoking pack-years (P = 0.019), macular cysts (P = 0.041), and pseudophakia (P = 0.003). The levels gradually increased during the follow-up (P < 0.0001) but less in the eyes with classic CNV (P = 0.011). Flare decreased during treatment-free periods lasting for at least two consecutive visits (P = 0.005). A peak in flare was observed 1 week after the first injection (P = 0.034, Wilcoxon signed rank test). In the fellow eyes, higher flare values in the beginning of the follow-up were associated with later conversion into exudative age-related macular degeneration (P = 0.015, Mann-Whitney U test). Anterior chamber flare correlated poorly with the CNV activity. Higher levels may, however, precede or exist early in the process that leads to the development of exudative age-related macular degeneration.

Spectral and Temporal Characteristics of X-Ray-Bright Stars in the Pleiades

NASA Technical Reports Server (NTRS)

Gagne, Marc; Caillault, Jean-Pierre; Stauffer, John R.

1995-01-01

We follow up our deep ROSAT imaging survey of the Pleiades (Stauffer et al. 1994) with an analysis of the spectral and temporal characteristics of the X-ray-bright stars in the Pleiades. Raymond & Smith (1977) one and two-temperature models have been used to fit the position-sensitive proportional counter (PSPC) pulse-height spectra of the dozen or so brightest sources associated with late-type Pleiades members. The best-fit temperatures suggest hot coronal temperatures for K, M, and rapidly rotating G stars, and cooler temperatures for F and slowly rotating G stars. In order to probe the many less X-ray-luminous stars, we have generated composite spectra by combining net counts from all Pleiades members according to spectral type and rotational velocity. Model fits to the composite spectra confirm the trend seen in the individual spectral fits. Particularly interesting is the apparent dependence of coronal temperature on L(sub x)/L(sub bol). A hardness-ratio analysis also confirms some of these trends. The PSPC data have also revealed a dozen or so strong X-ray flares with peak X-ray luminosities in excess of approx. 10(exp 30) ergs/sec. We have modeled the brightest of these flares with a simple quasi-static cooling loop model. The peak temperature and emission measure and the inferred electron density and plasma volume suggest a very large scale flaring event. The PSPC data were collected over a period of approx. 18 months, allowing us to search for source variability on timescales ranging from less than a day (in the case of flares) to more than a year between individual exposures. On approximately year-long timescales, roughly 25% of the late-type stars are variable. Since the Pleiades was also intensively monitored by the imaging instruments on the Einstein Observatory, we have examined X-ray luminosity variations on the 10 yr timescale between Einstein and ROSAT and find that up to 40% of the late-type stars are X-ray variable. Since there is only marginal evidence for increased variability on decade-long timescales, the variability observed on long and short timescales may have a common physical origin.

OBSERVATION OF THE 2011-02-15 X2.2 FLARE IN THE HARD X-RAY AND MICROWAVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuroda, Natsuha; Wang, Haimin; Gary, Dale E., E-mail: nk257@njit.edu

2015-07-10

Previous studies have shown that the energy release mechanism of some solar flares follow the Standard magnetic-reconnection model, but the detailed properties of high-energy electrons produced in the flare are still not well understood. We conducted a unique, multi-wavelength study that discloses the spatial, temporal and energy distributions of the accelerated electrons in the X2.2 solar flare on 2011 February 15. We studied the source locations of seven distinct temporal peaks observed in hard X-ray (HXR) and microwave (MW) light curves using the RHESSI in 50–75 keV channels and Nobeyama Radioheliograph in 34 GHz, respectively. We found that the sevenmore » emission peaks did not come from seven spatially distinct sites in HXR and MW, but rather in HXR we observed a sudden change in location only between the second and the third peak, with the same pattern occurring, but evolving more slowly in MW. Comparison between the HXR light curve and the temporal variations in intensity in the two MW source kernels also confirmed that the seven peaks came predominantly from two sources, each with multiple temporal peaks. In addition, we studied the polarization properties of MW sources, and time delay between HXR and MW. We discuss our results in the context of the tether-cutting model.« less

Estimating soot emissions from an elevated flare

NASA Astrophysics Data System (ADS)

Almanza, Victor; Sosa, Gustavo

2009-11-01

Combustion aerosols are one of the major concerns in flaring operations, due to both health and environmental hazards. Preliminary results are presented for a 2D transient simulation of soot formation in a reacting jet with exit velocity of 130 m/s under a 5 m/s crossflow released from a 50 m high elevated flare and a 50 cm nozzle. Combustion dynamics was simulated with OpenFOAM. Gas-phase non-premixed combustion was modeled with the Chalmers PaSR approach and a κ-ɛ turbulence model. For soot formation, Moss model was used and the ISAT algorithm for solving the chemistry. Sulfur chemistry was considered to account for the sourness of the fuel. Gas composition is 10 % H2S and 90 % C2H4. A simplified Glassman reaction mechanism was used for this purpose. Results show that soot levels are sensitive to the sulfur present in the fuel, since it was observed a slight decrease in the soot volume fraction. NSC is the current oxidation model for soot formation. Predicted temperature is high (about 2390 K), perhaps due to soot-radiation interaction is not considered yet, but a radiation model implementation is on progress, as well as an oxidation mechanism that accounts for OH radical. Flame length is about 50 m.

HOW GAS-DYNAMIC FLARE MODELS POWERED BY PETSCHEK RECONNECTION DIFFER FROM THOSE WITH AD HOC ENERGY SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longcope, D. W.; Klimchuk, J. A.

Aspects of solar flare dynamics, such as chromospheric evaporation and flare light curves, have long been studied using one-dimensional models of plasma dynamics inside a static flare loop, subjected to some energy input. While extremely successful at explaining the observed characteristics of flares, all such models so far have specified energy input ad hoc, rather than deriving it self-consistently. There is broad consensus that flares are powered by magnetic energy released through reconnection. Recent work has generalized Petschek’s basic reconnection scenario, topological change followed by field line retraction and shock heating, to permit its inclusion in a one-dimensional flare loop model. Heremore » we compare the gas dynamics driven by retraction and shocking to those from more conventional static loop models energized by ad hoc source terms. We find significant differences during the first minute, when retraction leads to larger kinetic energies and produces higher densities at the loop top, while ad hoc heating tends to rarify the loop top. The loop-top density concentration is related to the slow magnetosonic shock, characteristic of Petschek’s model, but persists beyond the retraction phase occurring in the outflow jet. This offers an explanation for observed loop-top sources of X-ray and EUV emission, with advantages over that provided by ad hoc heating scenarios. The cooling phases of the two models are, however, notably similar to one another, suggesting that observations at that stage will yield little information on the nature of energy input.« less

Frequencies of Flare Occurrence: Interaction between Convection and Coronal Loops

NASA Astrophysics Data System (ADS)

Mullan, D. J.; Paudel, R. R.

2018-02-01

Observations of solar and stellar flares have revealed the presence of power-law dependences between the flare energy and the time interval between flares. Various models have been proposed to explain these dependences and the numerical value of the power-law indices. Here, we propose a model in which convective flows in granules force the footpoints of coronal magnetic loops, which are frozen-in to photospheric gas, to undergo a random walk. In certain conditions, this can lead to a twist in the loop, which drives the loop unstable if the twist exceeds a critical value. The possibility that a solar flare is caused by such a twist-induced instability in a loop has been in the literature for decades. Here, we quantify the process in an approximate way with a view to replicating the power-law index. We find that, for relatively small flares, the random walk twisting model leads to a rather steep power-law slope that agrees very well with the index derived from a sample of 56,000+ solar X-ray flares reported by the GOES satellites. For relatively large flares, we find that the slope of the power law is shallower. The empirical power-law slopes reported for flare stars also have a range that overlaps with the slopes obtained here. We suggest that in the coolest stars, a significant change in slope should occur when the frozen-flux assumption breaks down due to low electrical conductivity.

Infrared countermeasure flare performance measurements using a gas gun

NASA Astrophysics Data System (ADS)

Krishnamoorthy, Lakshmanan; Stringer, Michael; Taylor, Mark R. G.; Kollias, S.

2004-12-01

A unique and cost effective measurement facility called the Reusable Aerodynamic Flare Ejection Capability (RAFEC) has been developed at the Defence Science and Technology Organisation (DSTO), Australia. The RAFEC system involves the use of a reusable, carrier projectile that is launched from a 10 inch, nitrogen driven gas gun. The IRCM flare is loaded in the carrier projectile and the gas gun launches the carrier projectile with a known velocity of between approximately 350 to 650 knots. At a pre-determined time after firing and in the field of view of the measuring instrumentation, the flare is ejected from the carrier projectile for performance measurements to be undertaken. The temporal, spatial and spectral quantities were accomplished with the instruments fielded around the gas gun line of fire and the trajectory is derived from the spatial measurements. The data will be used for hardware in the loop simulations and modelling. Further improvements such as; (1) multiple (maximum of three) flare ejection, (2) 1"x1"x8" format flares made to the carrier projectile, and (3) design and manufacture of the puston, a new item of firing hardware to obtain lower muzzle velocities have enhanced the RAFEC capability. Thus the RAFEC system provides a more realistic IRCM performance measurement capability as it incorporates the deceleration effects experienced by the flare on deployment.

A Test of Thick-Target Nonuniform Ionization as an Explanation for Breaks in Solar Flare Hard X-Ray Spectra

NASA Technical Reports Server (NTRS)

Holman, gordon; Dennis Brian R.; Tolbert, Anne K.; Schwartz, Richard

2010-01-01

Solar nonthermal hard X-ray (HXR) flare spectra often cannot be fitted by a single power law, but rather require a downward break in the photon spectrum. A possible explanation for this spectral break is nonuniform ionization in the emission region. We have developed a computer code to calculate the photon spectrum from electrons with a power-law distribution injected into a thick-target in which the ionization decreases linearly from 100% to zero. We use the bremsstrahlung cross-section from Haug (1997), which closely approximates the full relativistic Bethe-Heitler cross-section, and compare photon spectra computed from this model with those obtained by Kontar, Brown and McArthur (2002), who used a step-function ionization model and the Kramers approximation to the cross-section. We find that for HXR spectra from a target with nonuniform ionization, the difference (Delta-gamma) between the power-law indexes above and below the break has an upper limit between approx.0.2 and 0.7 that depends on the power-law index delta of the injected electron distribution. A broken power-law spectrum with a. higher value of Delta-gamma cannot result from nonuniform ionization alone. The model is applied to spectra obtained around the peak times of 20 flares observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI from 2002 to 2004 to determine whether thick-target nonuniform ionization can explain the measured spectral breaks. A Monte Carlo method is used to determine the uncertainties of the best-fit parameters, especially on Delta-gamma. We find that 15 of the 20 flare spectra require a downward spectral break and that at least 6 of these could not be explained by nonuniform ionization alone because they had values of Delta-gamma with less than a 2.5% probability of being consistent with the computed upper limits from the model. The remaining 9 flare spectra, based on this criterion, are consistent with the nonuniform ionization model.

Properties of hydrocarbon- and salt-contaminated flare pit soils in northeastern British Columbia (Canada).

PubMed

Arocena, J M; Rutherford, P M

2005-07-01

Many contaminated sites in Canada are associated with flare pits generated during past petroleum extraction operations. Flare pits are located adjacent to well sites, compressor stations and batteries and are often subjected to the disposal of wastes from the flaring of gas, liquid hydrocarbons and brine water. This study was conducted to evaluate the physical, chemical, electrical and mineral properties of three flare pit soils as compared to adjacent control soils. Results showed that particle size distribution, pH, total N, cation exchange capacity, exchangeable Mg(2+), and sodium adsorption ratio were similar in soils from flare pits and control sites. Total C, exchangeable Ca(2+), K(+) and Na(+), soluble Ca(2+), Mg(2+), K(+) and Na(+) and electrical conductivity were higher in flare pit soils compared to control soils. X-ray diffraction and scanning electron microscopic analyses showed the presence of gypsum [CaSO(4).2H(2)O], dolomite [CaMg(CO(3))(2)], pyrite [FeS(2)], jarosite [KFe(3)(OH)(6)(SO(4))(2)], magnesium sulphate, oxides of copper and iron+copper in salt efflorescence observed in flare pit soils. Soils from both flare pits and control sites contained mica, kaolonite and 2:1 expanding clays. The salt-rich materials altered the ionic equilibria in the flare pit soils; K(Mg-Ca) selectivity coefficients in control soils were higher compared to contaminated soils. The properties of soils (e.g., high electrical conductivity) affected by inputs associated with oil and gas operations might render flare pit soils less conducive to the establishment and growth of common agricultural crops and forest trees.

RXTE Monitoring of the Anomalous X-ray Pulsar 1E 1048.1-5937: Long-Term Variability and the 2007 March Event

NASA Technical Reports Server (NTRS)

Dib, Rim; Kaspi, Victoria M.; Gavriil, Fotis P.

2009-01-01

After three years of no unusual activity, Anomalous X-ray Pulsar 1E 1048.1-5937 reactivated in 2007 March. We report on the detection of a large glitch (deltav/v = 1.63(2) x 10(exp -5)) on 2007 March 26 (MJD 54185.9), contemporaneous with the onset of a pulsed-flux flare, the third flare observed from this source in 10 years of monitoring with the Rossi X-ray Timing Explorer. Additionally, we report on a detailed study of the evolution of the timing properties, the pulsed flux, and the pulse profile of this source as measured by RXTE from 1996 July to 2008 January. In our timing study, we attempted phase coherent timing of all available observations. We show that in 2001, a timing anomaly of uncertain nature occurred near the rise of the first pulsed flux flare; we show that a likely glitch (deltav/v = 2.91(9) x 10(exp -6)) occurred in 2002, near the rise of the second flare, and we present a detailed description of the variations in the spin-down. In our pulsed flux study, we compare the decays of the three flares and discuss changes in the hardness ratio. In our pulse profile study, we show that the profile exhibited large variations near the peak of the first two flares, and several small short-term profile variations during the most recent flare. Finally, we report on the discovery of a small burst 27 days after the peak of the last flare, the fourth burst discovered from this source. We discuss the relationships between the observed properties in the framework of the magnetar model.

[Nasal flaring as a predictor of mortality in patients with severe dyspnea].

PubMed

Zorrilla Riveiro, José Gregorio; Arnau Bartés, Anna; García Pérez, Dolors; Rafat Sellarés, Ramón; Mas Serra, Arantxa; Fernández Fernández, Rafael

2015-02-01

To determine whether the presence of nasal flaring is a clinical sign of severity and a predictor of hospital mortality in emergency patients with dyspnea. Prospective, observational, single-center study. We enrolled patients older than 15 years of age who required attention for dyspnea categorized as level II or III emergencies according to the Andorran Medical Triage system. Two observers evaluated the presence of nasal flaring. We recorded demographic and clinical variables, including respiratory effort, vital signs, arterial blood gases, and clinical course (hospital admission and mortality). Bivariable analysis was performed and multivariable logistic regression models were constructed. We enrolled 246 patients with a mean (SD) age of 77 (13) years; 52% were female. Nasal flaring was present in 19.5%. Patients with nasal flaring had triage levels indicating greater severity and they had more severe tachypnea, worse oxygenation, and greater acidosis and hypercapnia. Bivariable analysis detected that the following variables were associated with mortality: age (odds ratio [OR], 1.05; 95% CI, 1.01-1.10), prehospital care from the emergency medical service (OR, 3.97; 95% CI, 1.39-11.39), triage level II (OR, 4.19; 95% CI, 1.63-10.78), signs of respiratory effort such as nasal flaring (OR, 3.79; 95% CI, 1.65-8.69), presence of acidosis (OR, 7.09; 95% CI, 2.97-16.94), and hypercapnia (OR, 2.67; 95% CI, 1,11-6,45). The factors that remained independent predictors of mortality in the multivariable analysis were age, severity (triage level), and nasal flaring. In patients requiring emergency care for dyspnea, nasal flaring is a clinical sign of severity and a predictor of mortality.

The Rise and Fall of MU Velorum

NASA Astrophysics Data System (ADS)

Ayres, T. R.; Osten, R. A.; Brown, A.

1998-12-01

Mu Velorum (HD 93497) is a close visual pair consisting of a G5 III primary and a fainter companion, currently 2'' apart, with an orbital period of about 140 yr. The distance to the system is 36 pc. Mu Vel A is a 3 Msun giant, in the Hertzsprung gap beyond the ``rapid braking zone'' just redward of G0 III. Mu Vel recently was the source of a giant EUV flare, caught during a 12-day pointing in March 1998 by the Deep Survey telescope of the Extreme Ultraviolet Explorer. The outburst rose in less than half a day, and decayed with an e-folding time of several days. The peak flux, ~ 0.3 cnts s(-1) in the DS band 80--180 Angstroms, was approximately twice the quiescent level recorded during the previous ten days of observation. The size and long duration of the event are very unusual for a mid-G giant; in fact, more typical of the extremes seen among the hyperactive short-period RS Canum Venaticorum binaries. Although the secondary star is classified as a G2 V, published visual magnitude differences, and the enhanced 1900 Angstroms continuum (mu Vel was detected by IUE, but AB were not resolved), suggest that it falls earlier on the MS (perhaps F5 V) and indeed itself might be a pair. If mu Vel B is a short-period double, then arguably it could be the source of the giant flare. Unfortunately, little is known about the secondary owing to the small separation of the visual components of mu Vel, and their large difference in brightness. We discuss the flare event, EUV spectra obtained in quiescence and during the flare decay, and the nature of the puzzling secondary. [2mm] This work was supported by NASA grant NAG5-3226.

Correlation between aqueous flare and residual visual field area in retinitis pigmentosa.

PubMed

Nishiguchi, Koji M; Yokoyama, Yu; Kunikata, Hiroshi; Abe, Toshiaki; Nakazawa, Toru

2018-06-01

To investigate the relationship between aqueous flare, visual function and macular structures in retinitis pigmentosa (RP). Clinical data from 123 patients with RP (227 eyes), 35 patients with macular dystrophy (68 eyes) and 148 controls (148 eyes) were analysed. The differences in aqueous flare between clinical entities and the correlation between aqueous flare (measured with a laser flare cell meter) versus visual acuity, visual field area (Goldmann perimetry) and macular thickness (optical coherence tomography) in patients with RP were determined. Influence of selected clinical data on flare was assessed using linear mixed-effects model. Aqueous flare was higher in patients with RP than patients with macular dystrophy or controls (p=7.49×E-13). Aqueous flare was correlated with visual field area (R=-0.379, p=3.72×E-9), but not with visual acuity (R=0.083, p=0.215). Macular thickness (R=0.234, p=3.74×E-4), but not foveal thickness (R=0.122, p=0.067), was positively correlated with flare. Flare was not affected by the presence of macular complications. All these associations were maintained when the right and the left eyes were assessed separately. Analysis by linear mixed-effects model revealed that age (p=8.58×E-5), visual field area (p=8.01×E-7) and average macular thickness (p=0.037) were correlated with flare. Aqueous flare and visual field area were correlated in patients with RP. Aqueous flare may reflect the degree of overall retinal degeneration more closely than the local foveal impairment. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

The Width of a Solar Coronal Mass Ejection and the Source of the Driving Magnetic Explosion

NASA Technical Reports Server (NTRS)

Moore, Ronald L.; Sterling, Alphonse C.; Suess, Steven T.

2007-01-01

We show that the strength of the magnetic field in the area covered by the flare arcade following a CME-producing ejective solar eruption can be estimated from the final angular width of the CME in the outer corona and the final angular width of the flare arcade. We assume (1) the flux-rope plasmoid ejected from the flare site becomes the interior of the CME plasmoid, (2) in the outer corona (R greater than 2R(sub Sun)) the CME is roughly a spherical plasmoid with legs shaped like a light bulb, and (3) beyond some height in or below the outer corona the CME plasmoid is in lateral pressure balance with the surrounding magnetic field. The strength of the nearly radial magnetic field in the outer corona is estimated from the radial component of the interplanetary magnetic field measured by Ulysses. We apply this model to three well-observed CMEs that exploded from flare regions of extremely different size and magnetic setting. One of these CMEs is an over-and-out CME that exploded from a laterally far offset compact ejective flare. In each event, the estimated source-region field strength is appropriate for the magnetic setting of the flare. This agreement (1) indicates that CMEs are propelled by the magnetic field of the CME plasmoid pushing against the surrounding magnetic field, (2) supports the magnetic-arch-blowout scenario for over-and-out CMEs, and (3) shows that a CME s final angular width in the outer corona can be estimated from the amount of magnetic flux covered by the source-region flare arcade.

Frequency distributions and correlations of solar X-ray flare parameters

NASA Technical Reports Server (NTRS)

Crosby, Norma B.; Aschwanden, Markus J.; Dennis, Brian R.

1993-01-01

Frequency distributions of flare parameters are determined from over 12,000 solar flares. The flare duration, the peak counting rate, the peak hard X-ray flux, the total energy in electrons, and the peak energy flux in electrons are among the parameters studied. Linear regression fits, as well as the slopes of the frequency distributions, are used to determine the correlations between these parameters. The relationship between the variations of the frequency distributions and the solar activity cycle is also investigated. Theoretical models for the frequency distribution of flare parameters are dependent on the probability of flaring and the temporal evolution of the flare energy build-up. The results of this study are consistent with stochastic flaring and exponential energy build-up. The average build-up time constant is found to be 0.5 times the mean time between flares.

LEPTONIC AND LEPTO-HADRONIC MODELING OF THE 2010 NOVEMBER FLARE FROM 3C 454.3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diltz, C.; Böttcher, M.

In this study, we use a one-zone leptonic and a lepto-hadronic model to investigate the multi-wavelength emission and prominent flare of the flat spectrum radio quasar 3C 454.3 in 2010 November. We perform a parameter study with both models to obtain broadband fits to the spectral energy distribution (SED) of 3C 454.3. Starting with the baseline parameters obtained from the fits, we then investigate different flaring scenarios for both models to explain an extreme outburst and spectral hardening of 3C 454.3 that occurred in 2010 November. We find that the one-zone lepto-hadronic model can successfully explain both the broadband multi-wavelengthmore » SED and light curves in the optical R, Swift X-Ray Telescope, and Fermi γ -ray band passes for 3C 454.3 during quiescence and the peak of the 2010 November flare. We also find that the one-zone leptonic model produces poor fits to the broadband spectra in the X-ray and high-energy γ -ray band passes for the 2010 November flare.« less

The interpretation of hard X-ray polarization measurements in solar flares

NASA Technical Reports Server (NTRS)

Leach, J.; Emslie, A. G.; Petrosian, V.

1983-01-01

Observations of polarization of moderately hard X-rays in solar flares are reviewed and compared with the predictions of recent detailed modeling of hard X-ray bremsstrahlung production by non-thermal electrons. The recent advances in the complexity of the modeling lead to substantially lower predicted polarizations than in earlier models and more fully highlight how various parameters play a role in determining the polarization of the radiation field. The new predicted polarizations are comparable to those predicted by thermal modeling of solar flare hard X-ray production, and both are in agreement with the observations. In the light of these results, new polarization observations with current generation instruments are proposed which could be used to discriminate between non-thermal and thermal models of hard X-ray production in solar flares.

THE ROLE OF A FLUX ROPE EJECTION IN A THREE-DIMENSIONAL MAGNETOHYDRODYNAMIC SIMULATION OF A SOLAR FLARE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nishida, Keisuke; Shibata, Kazunari; Nishizuka, Naoto, E-mail: nishida@kwasan.kyoto-u.ac.jp

2013-10-01

We investigated the dynamic evolution of a three-dimensional (3D) flux rope eruption and magnetic reconnection process in a solar flare by simply extending the two-dimensional (2D) resistive magnetohydrodynamic simulation model of solar flares with low β plasma to a 3D model. We succeeded in reproducing a current sheet and bi-directional reconnection outflows just below the flux rope during the eruption in our 3D simulations. We calculated four cases of a strongly twisted flux rope and a weakly twisted flux rope in 2D and 3D simulations. The time evolution of a weakly twisted flux rope in the 3D simulation shows behaviorsmore » similar to those of the 2D simulation, while a strongly twisted flux rope in the 3D simulation clearly shows a different time evolution from the 2D simulation except for the initial phase evolution. The ejection speeds of both strongly and weakly twisted flux ropes in 3D simulations are larger than in the 2D simulations, and the reconnection rates in 3D cases are also larger than in the 2D cases. This indicates positive feedback between the ejection speed of a flux rope and the reconnection rate even in the 3D simulation, and we conclude that the plasmoid-induced reconnection model can be applied to 3D. We also found that small-scale plasmoids are formed inside a current sheet and make it turbulent. These small-scale plasmoid ejections have a role in locally increasing the reconnection rate intermittently as observed in solar flares, coupled with a global eruption of a flux rope.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mandage, Revati S.; McAteer, R. T. James, E-mail: mcateer@nmsu.edu

A magnetic power spectral analysis is performed on 53 solar active regions, observed from 2011 August to 2012 July. Magnetic field data obtained from the Helioseismic and Magnetic Imager, inverted as Active Region Patches, are used to study the evolution of the magnetic power index as each region rotates across the solar disk. Active regions are classified based on the numbers and sizes of solar flares they produce in order to study the relationship between flare productivity and the magnetic power index. The choice of window size and inertial range plays a key role in determining the correct magnetic powermore » index. The overall distribution of magnetic power indices has a range of 1.0–2.5. Flare-quiet regions peak at a value of 1.6. However, flare-productive regions peak at a value of 2.2. Overall, the histogram of the distribution of power indices of flare-productive active regions is well separated from flare-quiet active regions. Only 12% of flare-quiet regions exhibit an index greater than 2, whereas 90% of flare-productive regions exhibit an index greater than 2. Flare-quiet regions exhibit a high temporal variance (i.e., the index fluctuates between high and low values), whereas flare-productive regions maintain an index greater than 2 for several days. This shows the importance of including the temporal evolution of active regions in flare prediction studies, and highlights the potential of a 2–3 day prediction window for space weather applications.« less

Effects of camera location on the reconstruction of 3D flare trajectory with two cameras

NASA Astrophysics Data System (ADS)

Özsaraç, Seçkin; Yeşilkaya, Muhammed

2015-05-01

Flares are used as valuable electronic warfare assets for the battle against infrared guided missiles. The trajectory of the flare is one of the most important factors that determine the effectiveness of the counter measure. Reconstruction of the three dimensional (3D) position of a point, which is seen by multiple cameras, is a common problem. Camera placement, camera calibration, corresponding pixel determination in between the images of different cameras and also the triangulation algorithm affect the performance of 3D position estimation. In this paper, we specifically investigate the effects of camera placement on the flare trajectory estimation performance by simulations. Firstly, 3D trajectory of a flare and also the aircraft, which dispenses the flare, are generated with simple motion models. Then, we place two virtual ideal pinhole camera models on different locations. Assuming the cameras are tracking the aircraft perfectly, the view vectors of the cameras are computed. Afterwards, using the view vector of each camera and also the 3D position of the flare, image plane coordinates of the flare on both cameras are computed using the field of view (FOV) values. To increase the fidelity of the simulation, we have used two sources of error. One is used to model the uncertainties in the determination of the camera view vectors, i.e. the orientations of the cameras are measured noisy. Second noise source is used to model the imperfections of the corresponding pixel determination of the flare in between the two cameras. Finally, 3D position of the flare is estimated using the corresponding pixel indices, view vector and also the FOV of the cameras by triangulation. All the processes mentioned so far are repeated for different relative camera placements so that the optimum estimation error performance is found for the given aircraft and are trajectories.

K2 Ultracool Dwarfs Survey. II. The White Light Flare Rate of Young Brown Dwarfs

NASA Astrophysics Data System (ADS)

Gizis, John E.; Paudel, Rishi R.; Mullan, Dermott; Schmidt, Sarah J.; Burgasser, Adam J.; Williams, Peter K. G.

2017-08-01

We use Kepler K2 Campaign 4 short-cadence (one-minute) photometry to measure white light flares in the young, moving group brown dwarfs 2MASS J03350208+2342356 (2M0335+23) and 2MASS J03552337+1133437 (2M0355+11), and report on long-cadence (thirty-minute) photometry of a superflare in the Pleiades M8 brown dwarf CFHT-PL-17. The rotation period (5.24 hr) and projected rotational velocity (45 km s-1) confirm 2M0335+23 is inflated (R≥slant 0.20 {R}⊙ ) as predicted for a 0.06 {M}⊙ , 24 Myr old brown dwarf βPic moving group member. We detect 22 white light flares on 2M0335+23. The flare frequency distribution follows a power-law distribution with slope -α =-1.8+/- 0.2 over the range 1031 to 1033 erg. This slope is similar to that observed in the Sun and warmer flare stars, and is consistent with lower-energy flares in previous work on M6-M8 very-low-mass stars; taking the two data sets together, the flare frequency distribution for ultracool dwarfs is a power law over 4.3 orders of magnitude. The superflare (2.6× {10}34 erg) on CFHT-PL-17 shows higher-energy flares are possible. We detect no flares down to a limit of 2× {10}30 erg in the nearby L5γ AB Dor moving group brown dwarf 2M0355+11, consistent with the view that fast magnetic reconnection is suppressed in cool atmospheres. We discuss two multi-peaked flares observed in 2M0335+23, and argue that these complex flares can be understood as sympathetic flares, in which fast-mode magnetohydrodynamic waves similar to extreme-ultraviolet waves in the Sun trigger magnetic reconnection in different active regions.

Implications of RHESSI Observations for Solar Flare Models and Energetics

NASA Technical Reports Server (NTRS)

Holman, Gordon D.

2006-01-01

Observations of solar flares in X-rays and gamma-rays provide the most direct information about the hottest plasma and energetic electrons and ions accelerated in flares. The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has observed over 18000 solar flares in X-rays and gamma-rays since its launch in February of 2002. RHESSI observes the full Sun at photon energies from as low as 3 keV to as high as 17 MeV with a spectral resolution on the order of 1 keV. It also provides images in arbitrary bands within this energy range with spatial resolution as good as 3 seconds of arc. Full images are typically produced every 4 seconds, although higher time resolution is possible. This unprecedented combination of spatial, spectral, and temporal resolution, spectral range and flexibility has led to fundamental advances in our understanding of flares. I will show RHESSI and coordinated observations that confirm coronal magnetic reconnection models for eruptive flares and coronal mass ejections, but also present new puzzles for these models. I will demonstrate how the analysis of RHESSI spectra has led to a better determination of the energy flux and total energy in accelerated electrons, and of the energy in the hot, thermal flare plasma. I will discuss how these energies compare with each other and with the energy contained in other flare-related phenomena such as interplanetary particles and coronal mass ejections.

The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. I. Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kowalski, Adam F.; Allred, Joel C.; Daw, Adrian

2017-02-10

The 2014 March 29 X1 solar flare (SOL20140329T17:48) produced bright continuum emission in the far- and near-ultraviolet (NUV) and highly asymmetric chromospheric emission lines, providing long-sought constraints on the heating mechanisms of the lower atmosphere in solar flares. We analyze the continuum and emission line data from the Interface Region Imaging Spectrograph (IRIS) of the brightest flaring magnetic footpoints in this flare. We compare the NUV spectra of the brightest pixels to new radiative-hydrodynamic predictions calculated with the RADYN code using constraints on a nonthermal electron beam inferred from the collisional thick-target modeling of hard X-ray data from Reuven Ramatymore » High Energy Solar Spectroscopic Imager . We show that the atmospheric response to a high beam flux density satisfactorily achieves the observed continuum brightness in the NUV. The NUV continuum emission in this flare is consistent with hydrogen (Balmer) recombination radiation that originates from low optical depth in a dense chromospheric condensation and from the stationary beam-heated layers just below the condensation. A model producing two flaring regions (a condensation and stationary layers) in the lower atmosphere is also consistent with the asymmetric Fe ii chromospheric emission line profiles observed in the impulsive phase.« less

The Multiple Continuum Components in the White-Light Flare of 16 January 2009 on the dM4.5e Star YZ CMi

NASA Astrophysics Data System (ADS)

Kowalski, A. F.; Hawley, S. L.; Holtzman, J. A.; Wisniewski, J. P.; Hilton, E. J.

2012-03-01

The white light during M dwarf flares has long been known to exhibit the broadband shape of a T≈10 000 K blackbody, and the white light in solar-flares is thought to arise primarily from hydrogen recombination. Yet, a current lack of broad-wavelength coverage solar flare spectra in the optical/near-UV region prohibits a direct comparison of the continuum properties to determine if they are indeed so different. New spectroscopic observations of a secondary flare during the decay of a megaflare on the dM4.5e star YZ CMi have revealed multiple components in the white-light continuum of stellar flares, including both a blackbody-like spectrum and a hydrogen-recombination spectrum. One of the most surprising findings is that these two components are anti-correlated in their temporal evolution. We combine initial phenomenological modeling of the continuum components with spectra from radiative hydrodynamic models to show that continuum veiling causes the measured anti-correlation. This modeling allows us to use the components' inferred properties to predict how a similar spatially resolved, multiple-component, white-light continuum might appear using analogies to several solar-flare phenomena. We also compare the properties of the optical stellar flare white light to Ellerman bombs on the Sun.

The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. I. Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29

NASA Technical Reports Server (NTRS)

Kowalski, Adam F.; Allred, Joel C.; Daw, Adrian N.; Cauzzi, Gianna; Carlsson, Mats

2017-01-01

The 2014 March 29 X1 solar flare (SOL20140329T17:48) produced bright continuum emission in the far- and near-ultraviolet (NUV) and highly asymmetric chromospheric emission lines, providing long-sought constraints on the heating mechanisms of the lower atmosphere in solar flares. We analyze the continuum and emission line data from the Interface Region Imaging Spectrograph (IRIS) of the brightest flaring magnetic footpoints in this flare. We compare the NUV spectra of the brightest pixels to new radiative-hydrodynamic predictions calculated with the RADYN code using constraints on a nonthermal electron beam inferred from the collisional thick-target modeling of hard X-ray data from Reuven Ramaty High Energy Solar Spectroscopic Imager. We show that the atmospheric response to a high beam flux density satisfactorily achieves the observed continuum brightness in the NUV. The NUV continuum emission in this flare is consistent with hydrogen (Balmer) recombination radiation that originates from low optical depth in a dense chromospheric condensation and from the stationary beam-heated layers just below the condensation. A model producing two flaring regions (a condensation and stationary layers) in the lower atmosphere is also consistent with the asymmetric Fe II chromospheric emission line profiles observed in the impulsive phase.

Short-duration solar microwave bursts and associated soft X-ray emission. M.S. Thesis

NASA Technical Reports Server (NTRS)

Spangler, S. R.

1972-01-01

Two hundred and fifty-nine short-duration microwave (15.4 GHz) bursts which occurred during the period of January 1968 to March 1970 were correlated with possible soft X-ray (2-12 A) flares occurring simultaneously. Sixty-six percent of the microwave bursts which were observed during periods of soft X-ray data coverage had associated soft X-ray flares. A study of an index of impulsiveness of the microwave flares failed to show a separation of the events into subclasses which could be attributed to distinctly different physical mechanisms. A weak (0.43) correlation was found between the intensities of the microwave and X-ray flares. A very weak (0.15) and statistically questionable correlation was found between the total energy released in these two energy ranges. Two models for the electron acceleration mechanism are discussed.

Study of non-thermal photon production under different scenarios in solar flares. 2: The Compton inverse and Bremsstrahlung models and fittings

NASA Technical Reports Server (NTRS)

Perez-Peraza, J.; Alvarez, M.; Laville, A.; Gallegos, A.

1985-01-01

Energy spectra of photons emitted from Bremsstrahlung (BR) of energetic electrons with matter, is obtained from the deconvolution of the electron energy spectra. It can be inferred that the scenario for the production of X-rays and gamma rays in solar flares may vary from event to event. However, it is possible in many cases to associated low energy events to impulsive acceleration, and the high energy phase of some events to stochastic acceleration. In both cases, flare particles seem to be strongly modulated by local energy losses. Electric field acceleration, associated to neutral current sheets is a suitable candidate for impulsive acceleration. Finally, that the predominant radiation process of this radiation is the inverse Compton effect due to the local flare photon field.

Max '91 Workshop 2: Developments in Observations and Theory for Solar Cycle 22

NASA Technical Reports Server (NTRS)

Winglee, Robert M. (Editor); Dennis, Brian R. (Editor)

1989-01-01

Papers and observatory reports presented at the second workshop of the Max '91 program are compiled along with discussion group summaries and invited reviews. The four discussion groups addressed the following subjects: high-energy flare physics; coordinated magnetograph observations; flare theory and modeling; and Max '91 communications and coordination. A special session also took place on observations of Active Region 5395 and the associated flares of March 1989. Other topics covered during the workshop include the scientific objectives of solar gamma ray observations, the solar capabilities of each of the four instruments on the Gamma Ray Observatory, and access to Max '91 information.

Electron Densities in Solar Flare Loops, Chromospheric Evaporation Upflows, and Acceleration Sites

NASA Technical Reports Server (NTRS)

Aschwanden, Markus J.; Benz, Arnold O.

1996-01-01

We compare electron densities measured at three different locations in solar flares: (1) in Soft X-Ray (SXR) loops, determined from SXR emission measures and loop diameters from Yohkoh Soft X-Ray Telescope maps (n(sub e, sup SXR) = (0.2-2.5) x 10(exp 11)/ cu cm); (2) in chromospheric evaporation upflows, inferred from plasma frequency cutoffs of decimetric radio bursts detected with the 0.1-3 GHz spectrometer Phoenix of ETH Zuerich (n(sub e, sup upflow) = (0.3-11) x 10(exp 10)/cu cm; and (3) in acceleration sites, inferred from the plasma frequency at the separatrix between upward-accelerated (type III bursts) and downward-accelerated (reverse-drift bursts) electron beams [n(sub e, sup acc) = (0.6-10) x 10(exp 9)/cu cm]. The comparison of these density measurements, obtained from 44 flare episodes (during 14 different flares), demonstrates the compatibility of flare plasma density diagnostics with SXR and radio methods. The density in the upflowing plasma is found to be somewhat lower than in the filled loops, having ratios in a range n(sub e, sup upflow)/n(sub e, sup SXR) = 0.02-1.3, and a factor of 3.6 higher behind the upflow front. The acceleration sites are found to have a much lower density than the SXR-bright flare loops, i.e., n(sub e, sup acc)/n(sub e, sup SXR) = 0.005- 0.13, and thus must be physically displaced from the SXR-bright flare loops. The scaling law between electron time-of-flight distances l' and loop half-lengths s, l'/s = 1.4 +/- 0.3, recently established by Aschwanden et al. suggests that the centroid of the acceleration region is located above the SXR-bright flare loop, as envisioned in cusp geometries (e.g., in magnetic reconnection models).

Classification of X-ray solar flares regarding their effects on the lower ionosphere electron density profile

NASA Astrophysics Data System (ADS)

Grubor, D. P.; Ulić, D. M. Å.; Žigman, V.

2008-06-01

The classification of X-ray solar flares is performed regarding their effects on the Very Low Frequency (VLF) wave propagation along the Earth-ionosphere waveguide. The changes in propagation are detected from an observed VLF signal phase and amplitude perturbations, taking place during X-ray solar flares. All flare effects chosen for the analysis are recorded by the Absolute Phase and Amplitude Logger (AbsPal), during the summer months of 2004-2007, on the single trace, Skelton (54.72 N, 2.88 W) to Belgrade (44.85 N, 20.38 E) with a distance along the Great Circle Path (GCP) D≍2000 km in length. The observed VLF amplitude and phase perturbations are simulated by the computer program Long-Wavelength Propagation Capability (LWPC), using Wait's model of the lower ionosphere, as determined by two parameters: the sharpness (β in 1/km) and reflection height (H' in km). By varying the values of β and H' so as to match the observed amplitude and phase perturbations, the variation of the D-region electron density height profile Ne(z) was reconstructed, throughout flare duration. The procedure is illustrated as applied to a series of flares, from class C to M5 (5×10-5 W/m2 at 0.1-0.8 nm), each giving rise to a different time development of signal perturbation. The corresponding change in electron density from the unperturbed value at the unperturbed reflection height, i.e. Ne(74 km)=2.16×108 m-3 to the value induced by an M5 class flare, up to Ne(74 km)=4×1010 m-3 is obtained. The β parameter is found to range from 0.30-0.49 1/km and the reflection height H' to vary from 74-63 km. The changes in Ne(z) during the flares, within height range z=60 to 90 km are determined, as well.

Through the Ring of Fire: A Study of the Origin of Orphan Gamma-ray Flares in Blazars

NASA Astrophysics Data System (ADS)

MacDonald, Nicholas R.; Marscher, Alan P.; Jorstad, Svetlana G.; Joshi, Manasvita

2014-06-01

Blazars exhibit flares across the electromagnetic spectrum. Many gamma-ray flares are highly correlated with flares detected at optical wavelengths; however, a small subset appear to occur in isolation, with no counterpart in the other wave bands. These "orphan" gamma-ray flares challenge current models of blazar variability, most of which are unable to reproduce this type of behavior. We present numerical calculations of the time variable emission of a blazar based on a proposal by Marscher et al. (2010) to explain such events. In this model, a plasmoid ("blob") consisting of a power-law distribution of electrons propagates relativistically along the spine of a blazar jet and passes through a synchrotron emitting ring of electrons representing a shocked portion of the jet sheath. This ring supplies a source of seed photons that are inverse-Compton scattered by the electrons in the moving blob. As the blob approaches the ring, the photon density in the co-moving frame of the plasma increases, resulting in an orphan gamma-ray flare that then dissipates as the blob passes through and then moves away from the ring. The model includes the effects of radiative cooling and a spatially varying magnetic field. Support for the plausibility of this model is provided by observations by Marscher et al.(2010) of an isolated gamma-ray flare that was correlated with the passage of a superluminal knot through the inner jet of quasar PKS 1510-089. Synthetic light-curves produced by this new model are compared to the observed light-curves from this event. In addition, we present polarimetric observations that point to the existence of a jet sheath in the quasar 3C 273. A rough estimate of the bolometric luminosity of the sheath results in a value of ~10^45 erg s^-1 10% of the jet luminosity). This inferred sheath luminosity indicates that the jet sheath in 3C 273 can provide a significant source of seed photons that need to be taken into account when modeling the non-thermal emission due to inverse-Compton scattering processes. Funding for this research was provided by an NSERC PGS D2 Doctoral Fellowship and NASA under Fermi Guest Investigator grants NNX12AO79G and NNX12AO59G.

Flares, ejections, proton events

NASA Astrophysics Data System (ADS)

Belov, A. V.

2017-11-01

Statistical analysis is performed for the relationship of coronal mass ejections (CMEs) and X-ray flares with the fluxes of solar protons with energies >10 and >100 MeV observed near the Earth. The basis for this analysis was the events that took place in 1976-2015, for which there are reliable observations of X-ray flares on GOES satellites and CME observations with SOHO/LASCO coronagraphs. A fairly good correlation has been revealed between the magnitude of proton enhancements and the power and duration of flares, as well as the initial CME speed. The statistics do not give a clear advantage either to CMEs or the flares concerning their relation with proton events, but the characteristics of the flares and ejections complement each other well and are reasonable to use together in the forecast models. Numerical dependences are obtained that allow estimation of the proton fluxes to the Earth expected from solar observations; possibilities for improving the model are discussed.

The impulsive hard X-rays from solar flares

NASA Technical Reports Server (NTRS)

Leach, J.

1984-01-01

A technique for determining the physical arrangement of a solar flare during the impulsive phase was developed based upon a nonthermal model interpretation of the emitted hard X-rays. Accurate values are obtained for the flare parameters, including those which describe the magnetic field structure and the beaming of the energetic electrons, parameters which have hitherto been mostly inaccessible. The X-ray intensity height structure can be described readily with a single expression based upon a semi-empirical fit to the results from many models. Results show that the degree of linear polarization of the X-rays from a flaring loop does not exceed 25 percent and can easily and naturally be as low as the polarization expected from a thermal model. This is a highly significant result in that it supersedes those based upon less thorough calculations of the electron beam dynamics and requires that a reevaluation of hopes of using polarization measurements to discriminate between categories of flare models.

Flare Energy Release: Internal Conflict, Contradiction with High Resolution Observations, Possible Solutions

NASA Astrophysics Data System (ADS)

Pustilnik, L.

2017-06-01

All accepted paradigm of solar and stellar flares energy release based on 2 whales: 1. Source of energy is free energy of non-potential force free magnetic field in atmosphere above active region; 2. Process of ultrafast dissipation of magnetic fields is Reconnection in Thin Turbulent Current Sheet (RTTCS). Progress in observational techniques in last years provided ultra-high spatial resolution and in physics of turbulent plasma showed that real situation is much more complicated and standard approach is in contradiction both with observations and with problem of RTTCS stability. We present critical analysis of classic models of pre-flare energy accumulation and its dissipation during flare energy release from pioneer works Giovanelli (1939, 1947) up to topological reconnection. We show that all accepted description of global force-free fields as source of future flare cannot be agreed with discovered in last years fine and ultra-fine current-magnetic structure included numerouse arcs-threads with diameters up to 100 km with constant sequence from photosphere to corona. This magnetic skeleton of thin current magnetic threads with strong interaction between them is main source of reserved magnetic energy insolar atmosphere. Its dynamics will be controlled by percolation of magnetic stresses through network of current-magnetic threads with transition to flare state caused by critical value of global current. We show that thin turbulent current sheet is absolutely unstable configuration both caused by splitting to numerous linear currents by dissipative modes like to tearing, and as sequence of suppress of plasma turbulence caused by anomalous heating of turbulent plasma. In result of these factors primary RTTCS will be disrupted in numerous turbulent and normal plasma domains like to resistors network. Current propagation through this network will have percolation character with all accompanied properties of percolated systems: self-organization with formation power spectrum of distribution of flares and micro-flares, and possibility of phase transition to flare energy release with huge increasing of energy release.

Tophi and frequent gout flares are associated with impairments to quality of life, productivity, and increased healthcare resource use: Results from a cross-sectional survey.

PubMed

Khanna, Puja P; Nuki, George; Bardin, Thomas; Tausche, Anne-Kathrin; Forsythe, Anna; Goren, Amir; Vietri, Jeffrey; Khanna, Dinesh

2012-09-22

The prevalence of gout is increasing, and most research on the associated burden has focused on serum urate (sUA) levels. The present study quantifies the impact of the presence of tophi and frequency of acute gout attacks on health-related quality of life (HRQOL), productivity, and healthcare resource utilization. Patients with self-reported gout (n=620; 338 in US and 282 across France, Germany, and UK) were contacted based on inclusion in the 2010 US and EU National Health and Wellness Surveys (Kantar Health) and the Lightspeed Research ailment panel. Respondents were categorized into mutually-exclusive groups based on number of gout flares experienced in the past 12 months (0/don't recall, 1-2, 3, 4-5, 6+), current presence of tophi (none, 1+, or not sure), and sUA level awareness (yes, no). HRQOL (SF-12v2), healthcare provider visits in the last 6 months, and work productivity and activity impairment (WPAI) were compared across groups. Most patients were males, mean age of 61 years, who reported experiencing at least one acute gout flare in the past 12 months, and 12.3% (n=76) reported presence of tophi. Among the 27.7% (n=172) of patients who were aware of their sUA levels, higher sUA was associated with more flares and tophi. Decreased HRQOL was associated with more frequent flares and presence of tophi. In multivariable models predicting outcomes based on presence of tophi and number of flares, both flares (≥4) and tophi (≥1) were associated with HRQOL decrements on physical and mental component summary scores and health utilities (all p<0.05), after adjustment for age, gender, and time since diagnosis. Flares were also associated with greater activity impairment. Impairments associated with gout flares and presence of tophi, across patients in the US and EU, underscore the importance of effective management of this potentially curable condition.

Principle of Minimum Energy in Magnetic Reconnection in a Self-organized Critical Model for Solar Flares

NASA Astrophysics Data System (ADS)

Farhang, Nastaran; Safari, Hossein; Wheatland, Michael S.

2018-05-01

Solar flares are an abrupt release of magnetic energy in the Sun’s atmosphere due to reconnection of the coronal magnetic field. This occurs in response to turbulent flows at the photosphere that twist the coronal field. Similar to earthquakes, solar flares represent the behavior of a complex system, and expectedly their energy distribution follows a power law. We present a statistical model based on the principle of minimum energy in a coronal loop undergoing magnetic reconnection, which is described as an avalanche process. We show that the distribution of peaks for the flaring events in this self-organized critical system is scale-free. The obtained power-law index of 1.84 ± 0.02 for the peaks is in good agreement with satellite observations of soft X-ray flares. The principle of minimum energy can be applied for general avalanche models to describe many other phenomena.

Numerical simulations of loops heated to solar flare temperatures. III - Asymmetrical heating

NASA Technical Reports Server (NTRS)

Cheng, C.-C.; Doschek, G. A.; Karpen, J. T.

1984-01-01

A numerical model is defined for asymmetric full solar flare loop heating and comparisons are made with observational data. The Dynamic Flux Tube Model is used to describe the heating process in terms of one-dimensional, two fluid conservation equations of mass, energy and momentum. An adaptive grid allows for the downward movement of the transition region caused by an advancing conduction front. A loop 20,000 km long is considered, along with a flare heating system and the hydrodynamic evolution of the loop. The model was applied to generating line profiles and spatial X-ray and UV line distributions, which were compared with SMM, P78-1 and Hintori data for Fe, Ca and Mg spectra. Little agreement was obtained, and it is suggested that flares be treated as multi-loop phenomena. Finally, it is concluded that chromospheric evaporation is not an effective mechanism for generating the soft X-ray bursts associated with flares.

Aerodynamic Characteristics at a Mach Number of 6.8 of Two Hypersonic Missile Configurations, One with Low-Aspect-Ratio Cruciform Fins and Trailing-Edge Flaps and One with a Flared Afterbody and All-Movable Controls

NASA Technical Reports Server (NTRS)

Robinson, Ross B; Bernot, Peter T

1958-01-01

An investigation has been made to determine the aerodynamic characteristics in pitch at a Mach number of 6.8 of hypersonic missile configurations with cruciform trailing-edge flaps and with all-movable control surfaces. The flaps were tested on a configuration having low-aspect-ratio cruciform fins with an apex angle of 5 deg the all-movable controls were mounted at the 46.7-percent body station on a configuration having a 10 deg flared afterbody. The tests were made through an angle-of-attack range of -2 deg to 20 deg at zero sideslip in the Langley 11-inch hypersonic tunnel. The results indicated that the all-movable controls on the flared afterbody model should be capable of producing much larger values of trim lift and of normal acceleration than the trailing-edge -flap configuration. The flared -after body configuration had considerably higher drag than the cruciform-fin model but only slightly lower values of lift drag ratio.

Aerodynamic Characteristics at a Mach Number of 6.8 of Two Hypersonic Missile Configurations, One with Low-Aspect-Ratio Cruciform Fins and Trailing-Edge Flaps and One with a Flared Afterbody and All-Movable Controls

NASA Technical Reports Server (NTRS)

Bernot, P. T.; Robinson, R. B.

1958-01-01

An investigation has been made to determine the aerodynamic characteristics in pitch at a Mach number of 6.8 of hypersonic missile configurations with cruciform trailing-edge flaps and with all-movable control surfaces. The flaps were tested on a configuration having low-aspect-ratio cruciform fins with an apex angle of 5 degrees; the all-movable controls were mounted at the 46.7-percent body station on a configuration having a 10 degrees flared afterbody. The tests were made through an angle-of-attack range of -2 degrees to 20 degrees at zero sideslip in the Langley 11-inch hypersonic tunnel. The results indicated that the all-movable controls on the flared-afterbody model should be capable of producing much larger values of trim lift and of normal acceleration than the trailing-edge-flap configuration. The flared-afterbody configuration had considerably higher drag than the cruciform-fin model but only slightly lower values of lift-drag ratio.

LATERAL OFFSET OF THE CORONAL MASS EJECTIONS FROM THE X-FLARE OF 2006 DECEMBER 13 AND ITS TWO PRECURSOR ERUPTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sterling, Alphonse C.; Moore, Ronald L.; Harra, Louise K., E-mail: alphonse.sterling@nasa.gov, E-mail: ron.moore@nasa.gov, E-mail: lkh@mssl.ucl.ac.uk

2011-12-10

Two GOES sub-C-class precursor eruptions occurred within {approx}10 hr prior to and from the same active region as the 2006 December 13 X4.3-class flare. Each eruption generated a coronal mass ejection (CME) with center laterally far offset ({approx}> 45 Degree-Sign ) from the co-produced bright flare. Explaining such CME-to-flare lateral offsets in terms of the standard model for solar eruptions has been controversial. Using Hinode/X-Ray Telescope (XRT) and EUV Imaging Spectrometer (EIS) data, and Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph (LASCO) and Michelson Doppler Imager (MDI) data, we find or infer the following. (1) The first precursormore » was a 'magnetic-arch-blowout' event, where an initial standard-model eruption of the active region's core field blew out a lobe on one side of the active region's field. (2) The second precursor began similarly, but the core-field eruption stalled in the side-lobe field, with the side-lobe field erupting {approx}1 hr later to make the CME either by finally being blown out or by destabilizing and undergoing a standard-model eruption. (3) The third eruption, the X-flare event, blew out side lobes on both sides of the active region and clearly displayed characteristics of the standard model. (4) The two precursors were offset due in part to the CME originating from a side-lobe coronal arcade that was offset from the active region's core. The main eruption (and to some extent probably the precursor eruptions) was offset primarily because it pushed against the field of the large sunspot as it escaped outward. (5) All three CMEs were plausibly produced by a suitable version of the standard model.« less

X-ray and radio observations of flares from the RS Canum Venaticorum system UX ARIETIS

NASA Astrophysics Data System (ADS)

Tsuru, T.; Makishima, K.; Ohashi, T.; Inoue, H.; Koyama, K.; Turner, M. J. L.; Barstow, M. A.; McHardy, I. M.; Pye, J. P.; Tsunemi, H.; Kitamoto, S.; Taylor, A. R.; Nelson, R. F.

In July 1987 the RS CVn system UX Ari was observed in the 2-20-keV X-ray band by Ginga, immediately followed by 5-GHz radio observations. UX Ari was found to be very active at both radio and X-ray frequencies. Quiescent X-ray emission with a luminosity of 3 x 10 to the 31st erg/s (in the 2-20-keV band) was detected, together with two intense X-ray flares up to 2 x 10 to the 32nd and 6 x 10 to the 31st erg/s, respectively. Both flare and quiescent X-ray spectra are well fitted by single-temperature thermal bremsstrahlung models, with the continuum temperature and emission measure in the range 4-7 kev (in kT) and (2-10) x 10 to the 54th/cu cm, respectively.

Using Models for How Energetic Electrons Heat the Atmosphere During Flares

NASA Technical Reports Server (NTRS)

Allred, Joel

2011-01-01

Using models for how energetic electrons heat the atmosphere during flares, we simulate the radiative-hydrodynamic response of the lower solar atmosphere to flare heating. The simulations account for much of the non-LTE, optically thick radiative transfer that occurs in the chromosphere. Our models predict an increase in white light continuum during the flare on the order of 20%, but this is highly sensitive to the electron beam flux used in the simulation. We find that a majority of the white light continuum originates in the chromosphere as a result of Balmer and Paschen recombinations, but a significant portion also forms in the photosphere which has been heated by radiative backwarming.

Flat microwave spectra seen at X-class flares

NASA Technical Reports Server (NTRS)

Lee, Jeongwoo W.; Gary, Dale E.; Zirin, H.

1994-01-01

We report peculiar spectral activity of four large microwave bursts as obtained from the Solar Arrays at the Owens Valey Radio Observatory during observations of X-class flares on 24 May 1990 and 7, 8, 22 March 1991. Main observational points that we newly uncovered are: (1) flat flux spectra over 1-18 GHz in large amounts of flux ranging from 10(exp 2) to 10(exp 4) s.f.u. at the maximum phase, (2) a common evolutionary pattern in which the spectral region of dominant flux shifts from high frequencies at the initial rise to low frequencies at the decaying phase, and (3) unusual time profiles that are impulsive at high frequencies but more extended at lower frequencies. We carry out the model calculations of microwave spectra under assumptions of gyrosynchrotron mechanism and a dipole field configuration to reproduce the observational characteristics. Our results are summarized as follows. First, a flat microwave spectrum reaching up to 10(exp 2) - 10(exp 4) s.f.u. may occur in a case where a magnetic loop is extended to an angular size of approximately (0.7-7.0) x 10(exp -7) sterad and contains a huge number (N(E greater than 10 keV) approx. 10(exp 36) - 10(exp 38)) of nonthermal electrons with power-law index approx. 3-3.5 over the entire volume. Second, the observed spectral activity could adequately be accounted for by the shrinking of the region of nonthermal electrons to the loop top and by the softening of the power-law spectrum of electrons in a time scale ranging 3-45 min depending on the event. Third, the extended microwave activity at lower frequencies is probably due to electrons trapped in the loop top where magnetic fields are low. Finally, we clarify the physical distinction between these large, extended microwave bursts and the gradual/post-microwave bursts often seen in weak events, both of which are characterized by long-period activity and broadband spectra.

Model of flare lightcurve profile observed in soft X-rays

NASA Astrophysics Data System (ADS)

Gryciuk, Magdalena; Siarkowski, Marek; Gburek, Szymon; Podgorski, Piotr; Sylwester, Janusz; Kepa, Anna; Mrozek, Tomasz

We propose a new model for description of solar flare lightcurve profile observed in soft X-rays. The method assumes that single-peaked `regular' flares seen in lightcurves can be fitted with the elementary time profile being a convolution of Gaussian and exponential functions. More complex, multi-peaked flares can be decomposed as a sum of elementary profiles. During flare lightcurve fitting process a linear background is determined as well. In our study we allow the background shape over the event to change linearly with time. Presented approach originally was dedicated to the soft X-ray small flares recorded by Polish spectrophotometer SphinX during the phase of very deep solar minimum of activity, between 23 rd and 24 th Solar Cycles. However, the method can and will be used to interpret the lightcurves as obtained by the other soft X-ray broad-band spectrometers at the time of both low and higher solar activity level. In the paper we introduce the model and present examples of fits to SphinX and GOES 1-8 Å channel observations as well.

Semiempirical photospheric models of a solar flare on May 28, 2012

NASA Astrophysics Data System (ADS)

Andriets, E. S.; Kondrashova, N. N.

2015-02-01

The variation of the photosphere physical state during the decay phase of SF/B6.8-class solar flare on May 28, 2012 in active region NOAA 11490 is studied. We used the data of the spectropolarimetric observations with the French-Italian solar telescope THEMIS (Tenerife, Spain). Semi-empirical model atmospheres are derived from the inversion with SIR (Stokes Inversion based on Response functions) code. The inversion was based on Stokes profiles of six photospheric lines. Each model atmosphere has a two-component structure: a magnetic flux tube and non-magnetic surroundings. The Harvard Smithsonian Reference Atmosphere (HSRA) has been adopted for the surroundings. The macroturbulent velocity and the filling factor were assumed to be constant with the depth. The optical depth dependences of the temperature, magnetic field strength, and line-of-sight velocity are obtained from inversion. According to the received model atmospheres, the parameters of the magnetic field and the thermodynamical parameters changed during the decay phase of the flare. The model atmospheres showed that the photosphere remained in a disturbed state during observations after the maximum of the flare. There are temporal changes in the temperature and the magnetic field strength optical depth dependences. The temperature enhancement in the upper photospheric layers is found in the flaring atmospheres relative to the quiet-Sun model. The downflows are found in the low and upper photosphere at the decay phase of the flare.

VALIDATION OF THE CORONAL THICK TARGET SOURCE MODEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleishman, Gregory D.; Xu, Yan; Nita, Gelu N.

2016-01-10

We present detailed 3D modeling of a dense, coronal thick-target X-ray flare using the GX Simulator tool, photospheric magnetic measurements, and microwave imaging and spectroscopy data. The developed model offers a remarkable agreement between the synthesized and observed spectra and images in both X-ray and microwave domains, which validates the entire model. The flaring loop parameters are chosen to reproduce the emission measure, temperature, and the nonthermal electron distribution at low energies derived from the X-ray spectral fit, while the remaining parameters, unconstrained by the X-ray data, are selected such as to match the microwave images and total power spectra.more » The modeling suggests that the accelerated electrons are trapped in the coronal part of the flaring loop, but away from where the magnetic field is minimal, and, thus, demonstrates that the data are clearly inconsistent with electron magnetic trapping in the weak diffusion regime mediated by the Coulomb collisions. Thus, the modeling supports the interpretation of the coronal thick-target sources as sites of electron acceleration in flares and supplies us with a realistic 3D model with physical parameters of the acceleration region and flaring loop.« less

On the Importance of the Flare's Late Phase for the Solar Extreme Ultraviolet Irradiance

NASA Technical Reports Server (NTRS)

Woods, Thomas N.; Eparvier, Frank; Jones, Andrew R.; Hock, Rachel; Chamberlin, Phillip C.; Klimchuk, James A.; Didkovsky, Leonid; Judge, Darrell; Mariska, John; Bailey, Scott;

The Fading Behavior of the Propagating VLF Signal during the Recovery Time of Solar Flares

NASA Astrophysics Data System (ADS)

Yasmina, B.

2016-12-01

The VLF radio signal propagating in the waveguide delimited by the Earth's surface and the D-layer of the ionosphere undergoes important modifications due to solar flares. In this work we focus on the NRK (37.5 kHz) VLF transmitter signal that propagates along the medium path to Algiers receiver (distance=3495 km). The signal analysis of two different flare classes shows that the perturbation due to a week flare of C2.1 (Imax=2.1 x 10-6 W/m2) class are less important than the medium one of M3.2 (Imax=3.2 x 10-5 W/m2) class. This leads to the fast recovery to the normal ionospheric condition after the weak solar flare while the medium solar flare takes more time. Additionally, the study of the signal amplitude behaviors by means of the LWPC code shows that the fading displacement toward the transmitter is more significant in the case of M3.2 flare than C2.1 class.

PRODUCTIVITY OF SOLAR FLARES AND MAGNETIC HELICITY INJECTION IN ACTIVE REGIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Sung-hong; Wang Haimin; Chae, Jongchul, E-mail: sp295@njit.ed

The main objective of this study is to better understand how magnetic helicity injection in an active region (AR) is related to the occurrence and intensity of solar flares. We therefore investigate the magnetic helicity injection rate and unsigned magnetic flux, as a reference. In total, 378 ARs are analyzed using SOHO/MDI magnetograms. The 24 hr averaged helicity injection rate and unsigned magnetic flux are compared with the flare index and the flare-productive probability in the next 24 hr following a measurement. In addition, we study the variation of helicity over a span of several days around the times ofmore » the 19 flares above M5.0 which occurred in selected strong flare-productive ARs. The major findings of this study are as follows: (1) for a sub-sample of 91 large ARs with unsigned magnetic fluxes in the range from (3-5) x 10{sup 22} Mx, there is a difference in the magnetic helicity injection rate between flaring ARs and non-flaring ARs by a factor of 2; (2) the GOES C-flare-productive probability as a function of helicity injection displays a sharp boundary between flare-productive ARs and flare-quiet ones; (3) the history of helicity injection before all the 19 major flares displayed a common characteristic: a significant helicity accumulation of (3-45) x 10{sup 42} Mx{sup 2} during a phase of monotonically increasing helicity over 0.5-2 days. Our results support the notion that helicity injection is important in flares, but it is not effective to use it alone for the purpose of flare forecast. It is necessary to find a way to better characterize the time history of helicity injection as well as its spatial distribution inside ARs.« less

Productivity of Solar Flares and Magnetic Helicity Injection in Active Regions

NASA Astrophysics Data System (ADS)

Park, Sung-hong; Chae, Jongchul; Wang, Haimin

2010-07-01

The main objective of this study is to better understand how magnetic helicity injection in an active region (AR) is related to the occurrence and intensity of solar flares. We therefore investigate the magnetic helicity injection rate and unsigned magnetic flux, as a reference. In total, 378 ARs are analyzed using SOHO/MDI magnetograms. The 24 hr averaged helicity injection rate and unsigned magnetic flux are compared with the flare index and the flare-productive probability in the next 24 hr following a measurement. In addition, we study the variation of helicity over a span of several days around the times of the 19 flares above M5.0 which occurred in selected strong flare-productive ARs. The major findings of this study are as follows: (1) for a sub-sample of 91 large ARs with unsigned magnetic fluxes in the range from (3-5) × 1022 Mx, there is a difference in the magnetic helicity injection rate between flaring ARs and non-flaring ARs by a factor of 2; (2) the GOES C-flare-productive probability as a function of helicity injection displays a sharp boundary between flare-productive ARs and flare-quiet ones; (3) the history of helicity injection before all the 19 major flares displayed a common characteristic: a significant helicity accumulation of (3-45) × 1042 Mx2 during a phase of monotonically increasing helicity over 0.5-2 days. Our results support the notion that helicity injection is important in flares, but it is not effective to use it alone for the purpose of flare forecast. It is necessary to find a way to better characterize the time history of helicity injection as well as its spatial distribution inside ARs.

Study of the effect of solar flares on VLF signals during D-layer preparation or disappearance time

NASA Astrophysics Data System (ADS)

Ray, Suman; Chakrabarti, Sandip Kumar; Palit, Sourav

2016-07-01

"Very Low Frequency" (VLF) is one of the bands of the Radio waves having frequency 3-30 KHz, which propagates through the Earth-ionosphere wave-guide. In relation to propagation of radio waves through ionosphere, low mass and high mobility cause electrons to play a vital role. Electrons are not distributed uniformly in the ionosphere and depending on this factor, ionosphere has different layers namely D, E and F. Different ionospheric layers generally exist during day and night time. During day-time when the main source of the ionization of the ionosphere is Sun, the lower most layer of ionosphere is D-layer. But during the night-time when Sun is absent and cosmic ray is the main source of the ionization of the ionosphere, this D-layer disappears and E-layer becomes the lower most region of the ionosphere. Normally, patterns of VLF signal depend on regular solar flux variations. However, during solar flares extra energetic particles are released from Sun, which makes the changes in the ionization of the ionosphere and these changes can perturb VLF signal amplitude. Usually if a solar flare occurs during any time of day, it only affects the amplitude and phase of the VLF signals. But in the present work, we found the if the flare occurs during D-layer preparation / disappearance time, then it will not only affect to amplitude and phase of the VLF signals but also to terminator times of VLF signals. We have observed that the sun set terminator time of the VLF signals shifted towards night time due to the effect of a M-class solar flare which occurred during the D-layer disappearance time. The shift is so high that it crossed 5σ level. We are now trying to a make model using the ion-chemistry and LWPC code to explain this observed effect.

Observations of vector magnetic fields in flaring active regions

NASA Technical Reports Server (NTRS)

Chen, Jimin; Wang, Haimin; Zirin, Harold; Ai, Guoxiang

1994-01-01

We present vector magnetograph data of 6 active regions, all of which produced major flares. Of the 20 M-class (or above) flares, 7 satisfy the flare conditions prescribed by Hagyard (high shear and strong transverse fields). Strong photospheric shear, however, is not necessarily a condition for a flare. We find an increase in the shear for two flares, a 6-deg shear increase along the neutral line after a X-2 flare and a 13-deg increase after a M-1.9 flare. For other flares, we did not detect substantial shear changes.

Interaction of Two Filaments in a Long Filament Channel Associated with Twin Coronal Mass Ejections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Ruisheng; Chen, Yao; Wang, Bing

Using the high-quality observations of the Solar Dynamics Observatory , we present the interaction of two filaments (F1 and F2) in a long filament channel associated with twin coronal mass ejections (CMEs) on 2016 January 26. Before the eruption, a sequence of rapid cancellation and emergence of the magnetic flux has been observed, which likely triggered the ascending of the west filament (F1). The east footpoints of rising F1 moved toward the east far end of the filament channel, accompanied by post-eruption loops and flare ribbons. This likely indicated a large-scale eruption involving the long filament channel, which resulted frommore » the interaction between F1 and the east filament (F2). Some bright plasma flew over F2, and F2 stayed at rest during the eruption, likely due to the confinement of its overlying lower magnetic field. Interestingly, the impulsive F1 pushed its overlying magnetic arcades to form the first CME, and F1 finally evolved into the second CME after the collision with the nearby coronal hole. We suggest that the interaction of F1 and the overlying magnetic field of F2 led to the merging reconnection that forms a longer eruptive filament loop. Our results also provide a possible picture of the origin of twin CMEs and show that the large-scale magnetic topology of the coronal hole is important for the eventual propagation direction of CMEs.« less

Feature Selection, Flaring Size and Time-to-Flare Prediction Using Support Vector Regression, and Automated Prediction of Flaring Behavior Based on Spatio-Temporal Measures Using Hidden Markov Models

NASA Astrophysics Data System (ADS)

Al-Ghraibah, Amani

Solar flares release stored magnetic energy in the form of radiation and can have significant detrimental effects on earth including damage to technological infrastructure. Recent work has considered methods to predict future flare activity on the basis of quantitative measures of the solar magnetic field. Accurate advanced warning of solar flare occurrence is an area of increasing concern and much research is ongoing in this area. Our previous work 111] utilized standard pattern recognition and classification techniques to determine (classify) whether a region is expected to flare within a predictive time window, using a Relevance Vector Machine (RVM) classification method. We extracted 38 features which describing the complexity of the photospheric magnetic field, the result classification metrics will provide the baseline against which we compare our new work. We find a true positive rate (TPR) of 0.8, true negative rate (TNR) of 0.7, and true skill score (TSS) of 0.49. This dissertation proposes three basic topics; the first topic is an extension to our previous work [111, where we consider a feature selection method to determine an appropriate feature subset with cross validation classification based on a histogram analysis of selected features. Classification using the top five features resulting from this analysis yield better classification accuracies across a large unbalanced dataset. In particular, the feature subsets provide better discrimination of the many regions that flare where we find a TPR of 0.85, a TNR of 0.65 sightly lower than our previous work, and a TSS of 0.5 which has an improvement comparing with our previous work. In the second topic, we study the prediction of solar flare size and time-to-flare using support vector regression (SVR). When we consider flaring regions only, we find an average error in estimating flare size of approximately half a GOES class. When we additionally consider non-flaring regions, we find an increased average error of approximately 3/4 a GOES class. We also consider thresholding the regressed flare size for the experiment containing both flaring and non-flaring regions and find a TPR. of 0.69 and a TNR of 0.86 for flare prediction, consistent with our previous studies of flare prediction using the same magnetic complexity features. The results for both of these size regression experiments are consistent across a wide range of predictive time windows, indicating that the magnetic complexity features may be persistent in appearance long before flare activity. This conjecture is supported by our larger error rates of some 40 hours in the time-to-flare regression problem. The magnetic complexity features considered here appear to have discriminative potential for flare size, but their persistence in time makes them less discriminative for the time-to-flare problem. We also study the prediction of solar flare size and time-to-flare using two temporal features, namely the ▵- and ▵-▵-features, the same average size and time-to-flare regression error are found when these temporal features are used in size and time-to-flare prediction. In the third topic, we study the temporal evolution of active region magnetic fields using Hidden Markov Models (HMMs) which is one of the efficient temporal analyses found in literature. We extracted 38 features which describing the complexity of the photospheric magnetic field. These features are converted into a sequence of symbols using k-nearest neighbor search method. We study many parameters before prediction; like the length of the training window Wtrain which denotes to the number of history images use to train the flare and non-flare HMMs, and number of hidden states Q. In training phase, the model parameters of the HMM of each category are optimized so as to best describe the training symbol sequences. In testing phase, we use the best flare and non-flare models to predict/classify active regions as a flaring or non-flaring region using a sliding window method. The best prediction result is found where the length of the history training images are 15 images (i.e., Wtrain= 15) and the length of the sliding testing window is less than or equal to W train, the best result give a TPR of 0.79 consistent with previous flare prediction work, TNR of 0.87 arid TSS of 0.66, where both are higher than our previous flare prediction work. We find that the best number of hidden states which can describe the temporal evolution of the solar ARs is equal to five states, at the same time, a close resultant metrics are found using different number of states.

Comparing the Chromospheric Response to Different Flare Energy Transport Mechanisms

NASA Astrophysics Data System (ADS)

Kerr, G. S.; Reep, J. W.; Allred, J. C.; Russell, A. J. B.; Leake, J. E.; Tarr, L.

2017-12-01

The chromosphere is the origin of the bulk of the enhanced radiative output during solar flares, and so the mechanism(s) by which energy is transported from the release site to the chromosphere is a crucial ingredient in our understanding of flare physics. In the standard model of solar flares, non-thermal particle beams (typically electrons) transport energy from the corona to the chromosphere. While this model has been supported by flare observations, and while flare simulations employing this model have been successful in reproducing the observational characteristics of flares, there have been suggestions that electron beams are not the sole energy transport mechanism at play. Originally proposed by Emslie and Sturrock (1982), and revisited by Fletcher and Hudson (2008) the dissipation of downward propagating Alfvénic waves have been posited as an additional, or alternative, energy transport mechanism. Reep & Russell (2016) and Kerr et al (2016) used the WKB approximation to simulate flares in which energy was transported via Alfven waves. This model has been further developed to more realistically model wave energy transport by including the wave travel time (Reep et al, in prep). We present the radiative response of the solar chromosphere to energy input using both the standard electron beam mechanism, and using the updated Alfven wave mechanism, simulated using the radiation hydrodynamics code RADYN. We will show the formation properties of the Mg II and C II resonance lines, and the Mg II subordinate lines, all of which can be observed by the IRIS spacecraft, and the Ca II 8542 line which can be routinely observed from ground based observatories, commenting on any key differences in the formation of these lines in the different simulations that may be present. Finally we discuss other, less observed, chromospheric spectral lines such as Ly-alpha and He II 304 and their potential as tools to discriminate between the models, in order to determine what future observations may of particular use.

Particle propagation, wave growth and energy dissipation in a flaring flux tube

NASA Technical Reports Server (NTRS)

White, S. M.; Melrose, D. B.; Dulk, G. A.

1986-01-01

Wave amplification by downgoing particles in a common flare model is investigated. The flare is assumed to occur at the top of a coronal magnetic flux loop, and results in the heating of plasma in the flaring region. The hot electrons propagate down the legs of the flux tube towards increasing magnetic field. It is simple to demonstrate that the velocity distributions which result in this model are unstable to both beam instabilities and cyclotron maser action. An explanation is presented for the propagation effects on the distribution, and the properties of the resulting amplified waves are explored, concentrating on cyclotron maser action, which has properties (emission in the z mode below the local gyrofrequency) quite different from maser action by other distributions considered in the context of solar flares. The z mode waves will be damped in the coronal plasma surrounding the flaring flux tube and lead to heating there. This process may be important in the overall energy budget of the flare. The downgoing maser is compared with the loss cone maser, which is more likely to produce observable bursts.

IRIS Ultraviolet Spectral Properties of a Sample of X-Class Solar Flares

NASA Astrophysics Data System (ADS)

Butler, Elizabeth; Kowalski, Adam; Cauzzi, Gianna; Allred, Joel C.; Daw, Adrian N.

2018-06-01

The white-light (near-ultraviolet (NUV) and optical) continuum emission comprises the majority of the radiated energy in solar flares. However, there are nearly as many explanations for the origin of the white-light continuum radiation as there are white-light flares that have been studied in detail with spectra. Furthermore, there are rarely robust constraints on the time-resolved dynamics in the white-light emitting flare layers. We are conducting a statistical study of the properties of Fe II lines, Mg II lines, and NUV continuum intensity in bright flare kernels observed by the Interface Region Imaging Spectrograph (IRIS), in order to provide comprehensive constraints for radiative-hydrodynamic flare models. Here we present a new technique for identifying bright flare kernels and preliminary relationships among IRIS spectral properties for a sample of X-class solar flares.

Theory and modeling group

NASA Technical Reports Server (NTRS)

Holman, Gordon D.

1989-01-01

The primary purpose of the Theory and Modeling Group meeting was to identify scientists engaged or interested in theoretical work pertinent to the Max '91 program, and to encourage theorists to pursue modeling which is directly relevant to data which can be expected to result from the program. A list of participants and their institutions is presented. Two solar flare paradigms were discussed during the meeting -- the importance of magnetic reconnection in flares and the applicability of numerical simulation results to solar flare studies.

A Self-Critique of Self-Organized Criticality in Astrophysics

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.

2015-08-01

The concept of ``self-organized criticality'' (SOC) was originally proposed as an explanation of 1/f-noise by Bak, Tang, and Wiesenfeld (1987), but turned out to have a far broader significance for scale-free nonlinear energy dissipation processes occurring in the entire universe. Over the last 30 years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into numerical SOC toy models. The novel applications stimulated also vigorous debates about the discrimination between SOC-related and non-SOC processes, such as phase transitions, turbulence, random-walk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multi-scale, and other complexity phenomena. We review SOC models applied to astrophysical observations, attempt to describe what physics can be captured by SOC models, and offer a critique of weaknesses and strengths in existing SOC models.

A Self-Critique of Self-Organized Criticality in Astrophysics

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.

The concept of ``self-organized criticality'' (SOC) was originally proposed as an explanation of 1/f-noise by Bak, Tang, and Wiesenfeld (1987), but turned out to have a far broader significance for scale-free nonlinear energy dissipation processes occurring in the entire universe. Over the last 30 years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into numerical SOC toy models. The novel applications stimulated also vigorous debates about the discrimination between SOC-related and non-SOC processes, such as phase transitions, turbulence, random-walk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multi-scale, and other complexity phenomena. We review SOC models applied to astrophysical observations, attempt to describe what physics can be captured by SOC models, and offer a critique of weaknesses and strengths in existing SOC models.

Multiwavelength Spectral Variability of Mkn 501 in Outburst

NASA Astrophysics Data System (ADS)

Hempfling, Christina

2012-10-01

We propose simultaneous multiwavelength observations of the blazar Mrk501 in flaring state with XMM-Newton, FACT and Swift. Bright TeV gamma-ray flares have been detected repeatedly from Mrk501. Leptonic blazar models predict an simultaneous increase in the gamma-ray and X-ray bands. However, Mrk 501 also showed so-called orphan flares, as well as flares featuring time lags that are hard to explain by current models. Available data lack detailed light curves and hence are not sufficient to make strong statements on the nature of the responsible processes. These observations of a flare of Mrk501 in the gamma-ray and X-ray band with high spectral sensitivity and time resolution will yield a big contribution to the comprehension of blazar emission processes.

The quantitative properties of three soft X-ray flare kernels observed with the AS&E X-ray telescope on Skylab

NASA Technical Reports Server (NTRS)

Kahler, S. W.; Petrasso, R. D.; Kane, S. R.

1976-01-01

The physical parameters for the kernels of three solar X-ray flare events have been deduced using photographic data from the S-054 X-ray telescope on Skylab as the primary data source and 1-8 and 8-20 A fluxes from Solrad 9 as the secondary data source. The kernels had diameters of about 5-7 seconds of arc and in two cases electron densities at least as high as 0.3 trillion per cu cm. The lifetimes of the kernels were 5-10 min. The presence of thermal conduction during the decay phases is used to argue: (1) that kernels are entire, not small portions of, coronal loop structures, and (2) that flare heating must continue during the decay phase. We suggest a simple geometric model to explain the role of kernels in flares in which kernels are identified with emerging flux regions.

Solar flare model atmospheres

NASA Technical Reports Server (NTRS)

Hawley, Suzanne L.; Fisher, George H.

1993-01-01

Solar flare model atmospheres computed under the assumption of energetic equilibrium in the chromosphere are presented. The models use a static, one-dimensional plane parallel geometry and are designed within a physically self-consistent coronal loop. Assumed flare heating mechanisms include collisions from a flux of non-thermal electrons and x-ray heating of the chromosphere by the corona. The heating by energetic electrons accounts explicitly for variations of the ionized fraction with depth in the atmosphere. X-ray heating of the chromosphere by the corona incorporates a flare loop geometry by approximating distant portions of the loop with a series of point sources, while treating the loop leg closest to the chromospheric footpoint in the plane-parallel approximation. Coronal flare heating leads to increased heat conduction, chromospheric evaporation and subsequent changes in coronal pressure; these effects are included self-consistently in the models. Cooling in the chromosphere is computed in detail for the important optically thick HI, CaII and MgII transitions using the non-LTE prescription in the program MULTI. Hydrogen ionization rates from x-ray photo-ionization and collisional ionization by non-thermal electrons are included explicitly in the rate equations. The models are computed in the 'impulsive' and 'equilibrium' limits, and in a set of intermediate 'evolving' states. The impulsive atmospheres have the density distribution frozen in pre-flare configuration, while the equilibrium models assume the entire atmosphere is in hydrostatic and energetic equilibrium. The evolving atmospheres represent intermediate stages where hydrostatic equilibrium has been established in the chromosphere and corona, but the corona is not yet in energetic equilibrium with the flare heating source. Thus, for example, chromospheric evaporation is still in the process of occurring.

The MUSCLES Treasury Survey: Temporally- and Spectrally-Resolved Irradiance from Low-mass Exoplanet Host Stars

NASA Astrophysics Data System (ADS)

France, Kevin; Loyd, R. O. Parke; Youngblood, Allison; Linsky, Jeffrey; MUSCLES Treasury Survey Team

2016-01-01

The spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres. High-energy photons (X-ray to near-UV; 5 - 3200 Ang) from these stars regulate the atmospheric temperature profiles and photochemistry on orbiting planets, influencing the production of potential "biomarker" gases. It has been shown that the atmospheric signatures of potentially habitable planets around low-mass stars may be significantly different from planets orbiting Sun-like stars owing to the different UV spectral energy distribution. I will present results from a panchromatic survey (Hubble/Chandra/XMM/optical) of M and K dwarf exoplanet hosts, the MUSCLES Treasury Survey (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems). We reconstruct the Lyman-alpha and extreme-UV (100-900 Ang) radiation lost to interstellar attenuation and create 5 Angstrom to 5 micron stellar irradiance spectra; these data will be publically available as a High-Level Science Product on MAST. We find that all low-mass exoplanet host stars exhibit significant chromospheric/transition region/coronal emission -- no "UV inactive" M dwarfs are observed. The F(far-UV)/F(near-UV) flux ratio, a driver for possible abiotic production of the suggested biomarkers O2 and O3, increases by ~3 orders of magnitude as the habitable zone moves inward from 1 to 0.1 AU, while the incident far-UV (912 - 1700 Ang) and XUV (5 - 900 Ang) radiation field strengths decrease by factors of a few across this range. Far-UV flare activity is common in 'optically inactive' M dwarfs; statistics from the entire sample indicate that large UV flares (E(300 - 1700 Ang) >= 10^31 erg) occur several times per day on typical M dwarf exoplanet hosts.

40 CFR 98.253 - Calculating GHG emissions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... a flare. 0.001 = Unit conversion factor (metric tons per kilogram, mt/kg). n = Number of measurement... average. MVC = Molar volume conversion factor (849.5 scf/kg-mole at 68 °F and 14.7 pounds per square inch... (kg/kg-mole). MVC = Molar volume conversion factor (849.5 scf/kg-mole at 68 °F and 14.7 psia or 836.6...

40 CFR 98.253 - Calculating GHG emissions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... a flare. 0.001 = Unit conversion factor (metric tons per kilogram, mt/kg). n = Number of measurement... average. MVC = Molar volume conversion factor (849.5 scf/kg-mole at 68 °F and 14.7 pounds per square inch... (kg/kg-mole). MVC = Molar volume conversion factor (849.5 scf/kg-mole at 68 °F and 14.7 psia or 836.6...

40 CFR 98.253 - Calculating GHG emissions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... a flare. 0.001 = Unit conversion factor (metric tons per kilogram, mt/kg). n = Number of measurement... average. MVC = Molar volume conversion factor (849.5 scf/kg-mole at 68 °F and 14.7 pounds per square inch... (kg/kg-mole). MVC = Molar volume conversion factor (849.5 scf/kg-mole at 68 °F and 14.7 psia or 836.6...

40 CFR 98.253 - Calculating GHG emissions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... a flare. 0.001 = Unit conversion factor (metric tons per kilogram, mt/kg). n = Number of measurement... average. MVC = Molar volume conversion factor (849.5 scf/kg-mole at 68 °F and 14.7 pounds per square inch... (kg/kg-mole). MVC = Molar volume conversion factor (849.5 scf/kg-mole at 68 °F and 14.7 psia or 836.6...

Two-phase Heating in Flaring Loops

NASA Astrophysics Data System (ADS)

Zhu, Chunming; Qiu, Jiong; Longcope, Dana W.

2018-03-01

We analyze and model a C5.7 two-ribbon solar flare observed by the Solar Dynamics Observatory, Hinode, and GOES on 2011 December 26. The flare is made of many loops formed and heated successively over one and half hours, and their footpoints are brightened in the UV 1600 Å before enhanced soft X-ray and EUV missions are observed in flare loops. Assuming that anchored at each brightened UV pixel is a half flaring loop, we identify more than 6700 half flaring loops, and infer the heating rate of each loop from the UV light curve at the footpoint. In each half loop, the heating rate consists of two phases: intense impulsive heating followed by a low-rate heating that is persistent for more than 20 minutes. Using these heating rates, we simulate the evolution of their coronal temperatures and densities with the model of the “enthalpy-based thermal evolution of loops.” In the model, suppression of thermal conduction is also considered. This model successfully reproduces total soft X-ray and EUV light curves observed in 15 passbands by four instruments GOES, AIA, XRT, and EVE. In this flare, a total energy of 4.9 × 1030 erg is required to heat the corona, around 40% of this energy is in the slow-heating phase. About two-fifths of the total energy used to heat the corona is radiated by the coronal plasmas, and the other three fifth transported to the lower atmosphere by thermal conduction.

Gradient spectral analysis of solar radio flare superevents

NASA Astrophysics Data System (ADS)

Rosa, R. R.; Veronese, T. B.; Sych, R. A.; Bolzan, M. A.; Sandri, S. A.; Drummond, I. A.; Becceneri, J. C.; Sawant, H. S.

2011-12-01

Some of complex solar active regions exhibit rare and sudden transitions that occur over time intervals that are short compared to the characteristic time scales of their evolution. Usually, extreme radio emission is driven by a latent nonlinear process involving magnetic reconnection among coronal loops and such extreme events (e.g., X-class flares and coronal mass ejections) express the presence of plasma and magnetic activity usually hidden inside the solar convective layer. Recently, the scaling exponent obtained from Detrended Fluctuation Analysis has been used to characterize the formation of solar flare superevents - SFS (integrated flux of radiation greater than 1.5 J/m2) when it is observed in the decimetric range of 1-3 GHz (Veronese et al., 2011). Here, we show a complementary computational analisys of four X-class solar flares observed in 17GHz from Nobeyama Radioheliograph. Our analysis is based on the combination of DFA and Gradient Spectral Analysis (GSA) which can be used to characterize the evolution of SFSs under the condition that the emission threshold is large enough (fmax > 300 S.F.U.) and the solar flux unit variability is greater than 50% of the average taken from the minimum flux to the extreme value. Preliminary studies of the gradient spectra of Nobeyama data in 17 GHz can be found in Sawant et al. (JASTP 73(11), 2011). Future applications of GSA on the images which will be observed from the Brazilian Decimetric Array (BDA) are discusssed.

Analysis of X-15 Landing Approach and Flare Characteristics Determined from the First 30 Flights

NASA Technical Reports Server (NTRS)

Matranga, Gene J.

1961-01-01

The approach and flare maneuvers for the first 30 flights of the X-15 airplane and the various control problems encountered are discussed. The results afford a relatively good cross section of landing conditions that might be experienced with future glide vehicles having low lift-drag ratios. Flight-derived drag data show that preflight predictions based on wind-tunnel tests were, in general, somewhat higher than the values measured in flight. Depending on configuration, the peak lift-drag ratios from flight varied from 3.5 to 4.5 as compared with a predicted range of from 3.0 to 4.2. By employing overhead, spiral-type patterns beginning at altitudes as high as 40,000 feet, the pilots were consistently able to touch down within about +/-1,000 feet of a designated point. A typical flare was initiated at a "comfortable" altitude of about 800 feet and an indicated airspeed of approximately 300 knots., which allowed a margin of excess speed. The flap and gear were extended when the flare was essentially completed, and an average touchdown was accomplished at a speed of about 185 knots indicated airspeed, an angle of attack of about 7 deg, and a rate of descent of about 4 feet per second. In general, the approach and landing characteristics were predicted with good accuracy in extensive preflight simulations. F-104 airplanes which simulated the X-15 landing characteristics were particularly valuable for pilot training.

Photospheric Current Spikes as Possible Predictors of Flares

NASA Technical Reports Server (NTRS)

Goodman, Michael L.; Kwan, Chiman; Ayhan, Bulent; Shang, Eric L.

2016-01-01

Flares involve generation of the largest current densities in the solar atmosphere. This suggests the hypothesis that prior to a large (M,X) flare there are related time dependent changes in the photospheric current distribution, and hence in the resistive heating rate in neutral line regions (NLRs). If this is true, these changes might be useful predictors of flares. Preliminary evidence supporting this hypothesis is presented. Results from a data driven, near photospheric, 3D magnetohydrodynamic type model suggest the model might be useful for predicting M and X flares several hours to several days in advance. The model takes as input the photospheric magnetic field observed by the Helioseismic and Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO) satellite. The model computes quantities in every active region (AR) pixel for 14 ARs, with spurious Doppler periods due to SDO orbital motion filtered out of the time series of the magnetic field for each pixel. Spikes in the NLR resistive heating rate Q, appearing as increases by orders of magnitude above background values in the time series of Q are found to occur, and appear to be correlated with the occurrence of M or X flares a few hours to a few days later. The subset of spikes analyzed at the pixel level are found to occur on HMI and granulation scales of 1 arcsec and 12 minutes. Spikes are found in NLRs with and without M or X flares, and outside as well as inside NLRs, but the largest spikes are localized in the NLRs of ARs with M or X flares, and associated with horizontal magnetic field strengths approximately several hG, and vertical magnetic field strengths several orders of magnitude smaller. The spikes may be signatures of horizontal current sheets associated with emerging magnetic flux.

Photospheric Current Spikes as Possible Predictors of Flares

NASA Technical Reports Server (NTRS)

Goodman, Michael L.; Kwan, Chiman; Ayhan, Bulent; Shang, Eric L.

2016-01-01

Flares involve generation of the largest current densities in the solar atmosphere. This suggests the hypothesis that prior to a large (M,X) flare there are related time dependent changes in the photospheric current distribution, and hence in the resistive heating rate in neutral line regions (NLRs). If this is true, these changes might be useful predictors of flares. Evidence supporting this hypothesis is presented. Results from a data driven, near photospheric, 3D magnetohydrodynamic type model suggest the model might be useful for predicting M and X flares several hours to several days in advance. The model takes as input the photospheric magnetic field observed by the Helioseismic & Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO) satellite. The model computes quantities in every active region (AR) pixel for 14 ARs, with spurious Doppler periods due to SDO orbital motion filtered out of the time series of the magnetic field for each pixel. Spikes in the NLR resistive heating rate Q, appearing as increases by orders of magnitude above background values in the time series of Q are found to occur, and appear to be correlated with the occurrence of M or X flares a few hours to a few days later. The subset of spikes analyzed at the pixel level are found to occur on HMI and granulation scales of 1 arcsec and 12 minutes. Spikes are found in NLRs with and without M or X flares, and outside as well as inside NLRs, but the largest spikes are localized in the NLRs of ARs with M or X flares, and associated with horizontal magnetic field strengths several hG, and vertical magnetic field strengths several orders of magnitude smaller, suggesting that the spikes are associated with current sheets.

Rethinking the solar flare paradigm

NASA Astrophysics Data System (ADS)

D, B. MELROSE

2018-07-01

It is widely accepted that solar flares involve release of magnetic energy stored in the solar corona above an active region, but existing models do not include the explicitly time-dependent electrodynamics needed to describe such energy release. A flare paradigm is discussed that includes the electromotive force (EMF) as the driver of the flare, and the flare-associated current that links different regions where magnetic reconnection, electron acceleration, the acceleration of mass motions and current closure occur. The EMF becomes localized across regions where energy conversion occurs, and is involved in energy propagation between these regions.

Implications of the pion-decay gamma emission and neutron observations with CORONAS-F/SONG

NASA Astrophysics Data System (ADS)

Kurt, V.; Yushkov, B.; Kudela, K.

2013-05-01

We analyzed the high-energy gamma and neutron emissions observed by the SONG instrument onboard the CORONAS-F satellite during August 25, 2001, October 28, 2003, November 4, 2003, and January 20, 2005 solar flares. These flares produced neutrons and/or protons recorded near Earth. The SONG response was consistent with detection of the pion-decay gamma emission and neutrons in these events. We compared time profiles of various electromagnetic emissions and showed that the maximum of the pion-decay-emission coincided in time best of all with the soft X-ray derivative, dISXR/dt, maximum. We evaluated the energy of accelerated ions and compared it with the energy deposited by accelerated electrons. The ion energy becomes comparable or even higher than the electron energy from a certain step of flare development. So the time profile of dISXR/dt is a superposition of energy deposited by both fractions of accelerated particles. This result allowed us to use a time profile of dISXR/dt as a real proxy of time behavior of the energy release at least during major flare analysis. In particular the time interval when the dISXR/dt value exceeds 0.9 of its maximum can be used as a unified reference point for the calculations of time delay between the high-energy proton acceleration and GLE onset. Analysis of the total set of pion-decay emission observations shows that such temporal closeness of pion-decay emission maximum and the soft X-ray derivative maximum is typical but not obligatory.

The origin of two X-class flares in active region NOAA 12673. Shear flows and head-on collision of new and preexisting flux

NASA Astrophysics Data System (ADS)

Verma, Meetu

2018-05-01

Flare-prolific active region NOAA 12673 produced consecutive X2.2 and X9.3 flares on the 6 September 2017. To scrutinize the morphological, magnetic, and horizontal flow properties associated with these flares, a seven-hour time series was used consisting of continuum images, line-of-sight and vector magnetograms, and 1600 Å UV images. These data were acquired with the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA). The white-light flare emission differed for both flares, while the X2.2 flare displayed localized, confined flare kernels, the X9.3 flare exhibited a two-ribbon structure. In contrast, the excess UV emission exhibited a similar structure for both flares, but with larger areal extent for the X9.3 flare. These two flares represented a scenario in which the first confined flare acted as precursor, setting up the stage for the more extended flare. Difference maps for continuum and magnetograms revealed locations of significant changes, that is, penumbral decay and umbral strengthening. The curved magnetic polarity inversion line in the δ-spot was the fulcrum of most changes. Horizontal proper motions were computed using the differential affine velocity estimator for vector magnetograms (DAVE4VM). Persistent flow features included (1) strong shear flows along the polarity inversion line, where the negative, parasitic polarity tried to bypass the majority, positive-polarity part of the δ-spot in the north, (2) a group of positive-polarity spots, which moved around the δ-spot in the south, moving away from the δ-spot with significant horizontal flow speeds, and (3) intense moat flows partially surrounding the penumbra of several sunspots, which became weaker in regions with penumbral decay. The enhanced flare activity has its origin in the head-on collision of newly emerging flux with an already existing regular, α-spot. Umbral cores of emerging bipoles were incorporated in its penumbra, creating a δ-configuration with an extended polarity inversion line, as the parasitic umbral cores were stretched while circumventing the majority polarity. The movie associated to Fig. A.1 is available at http://https://www.aanda.org

A STOL airworthiness investigation using a simulation of an augmentor wing transport. Volume 2: Simulation data and analysis

NASA Technical Reports Server (NTRS)

Heffley, R. K.; Stapleford, R. L.; Rumold, R. C.; Lehman, J. M.; Scott, B. C.; Hynes, C. S.

1974-01-01

A simulator study of STOL airworthiness was conducted using a model of an augmentor wing transport. The approach, flare and landing, go-around, and takeoff phases of flight were investigated. The simulation and the data obtained are described. These data include performance measures, pilot commentary, and pilot ratings. A pilot/vehicle analysis of glide slope tracking and of the flare maneuver is included.

Correlation between solar flare productivity and photospheric vector magnetic fields

NASA Astrophysics Data System (ADS)

Cui, Yanmei; Wang, Huaning

2008-11-01

Studying the statistical correlation between the solar flare productivity and photospheric magnetic fields is very important and necessary. It is helpful to set up a practical flare forecast model based on magnetic properties and improve the physical understanding of solar flare eruptions. In the previous study ([Cui, Y.M., Li, R., Zhang, L.Y., He, Y.L., Wang, H.N. Correlation between solar flare productivity and photospheric magnetic field properties 1. Maximum horizontal gradient, length of neutral line, number of singular points. Sol. Phys. 237, 45 59, 2006]; from now on we refer to this paper as ‘Paper I’), three measures of the maximum horizontal gradient, the length of the neutral line, and the number of singular points are computed from 23990 SOHO/MDI longitudinal magnetograms. The statistical relationship between the solar flare productivity and these three measures is well fitted with sigmoid functions. In the current work, the three measures of the length of strong-shear neutral line, total unsigned current, and total unsigned current helicity are computed from 1353 vector magnetograms observed at Huairou Solar Observing Station. The relationship between the solar flare productivity and the current three measures can also be well fitted with sigmoid functions. These results are expected to be beneficial to future operational flare forecasting models.

Expanding and Contracting Coronal Loops as Evidence of Vortex Flows Induced by Solar Eruptions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dudík, J.; Zuccarello, F. P.; Aulanier, G.

Eruptive solar flares were predicted to generate large-scale vortex flows at both sides of the erupting magnetic flux rope. This process is analogous to a well-known hydrodynamic process creating vortex rings. The vortices lead to advection of closed coronal loops located at the peripheries of the flaring active region. Outward flows are expected in the upper part and returning flows in the lower part of the vortex. Here, we examine two eruptive solar flares, the X1.1-class flare SOL2012-03-05T03:20 and the C3.5-class SOL2013-06-19T07:29. In both flares, we find that the coronal loops observed by the Atmospheric Imaging Assembly in its 171more » Å, 193 Å, or 211 Å passbands show coexistence of expanding and contracting motions, in accordance with the model prediction. In the X-class flare, multiple expanding and contracting loops coexist for more than 35 minutes, while in the C-class flare, an expanding loop in 193 Å appears to be close by and cotemporal with an apparently imploding loop arcade seen in 171 Å. Later, the 193 Å loop also switches to contraction. These observations are naturally explained by vortex flows present in a model of eruptive solar flares.« less

Echoes from a Dying Star

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-06-01

When a passing star is torn apart by a supermassive black hole, it emits a flare of X-ray, ultraviolet, and optical light. What can we learn from the infrared echo of a violent disruption like this one?Stellar DestructionOptical (black triangles) and infrared (blue circles and red squares) observations of F010042237. Day 0 marks the day the optical emission peaked. The infrared emission rises steadily through the end of the data. [Dou et al. 2017]Tidal disruption events occur when a star passes within the tidal radius of a supermassive black hole. After tidal forces pull the star apart, much of the stellar matter falls onto the black hole, radiating briefly in X-ray, ultraviolet and optical as it accretes. This signature rise and gradual fall of emission has allowed us to detect dozens of tidal disruption events thus far.One of the recently discovered candidate events is a little puzzling. Not only does the candidate in ultraluminous infrared galaxy F010042237 have an unusual host most disruptions occur in galaxies that are no longer star-forming, in contrast to this one but its optical light curve also shows an unusually long decay time.Now mid-infrared observations of this event have beenpresented by a team of scientists led by Liming Dou (Guangzhou University and Department of Education, Guangdong Province, China), revealing why this disruption is behaving unusually.Schematic of a convex dusty ring (red bows) that absorbs UV photons and re-emits in the infrared. It simultaneously scatters UV and optical photons into our line of sight. The dashed lines illustrate the delays at lags of 60 days, 1, 2, 3, 4, and 5 years. [Adapted from Dou et al. 2017]A Dusty Solution?The optical flare from F010042237s nucleus peaked in 2010, so Dou and collaborators obtained archival mid-infrared data from the WISE and NEOWISE missions from 2010 to 2016. The data show that the galaxy is quiescent in mid-infrared in 2010 but in data from three years later, the infrared emission has significantly increased, and it continues to brighten steadily through the end of the data.Whats going on? The supermassive black hole in the nucleus of F010042237 is likely shrouded by dust! The optical and ultraviolet radiation from the disruption is absorbed by the dust surrounding the black hole. This light is then reemitted as infrared radiation which we see as a delayed echo of the flare, since the light had to travel out to the surrounding dust before being reemitted and traveling to us.Modeling EchoesA fit of the data (points) to light curves (dashed lines) generated by one of the authors dust ring models. [Adapted from Dou et al. 2017]Dou and collaborators show that the observations of F010042237 can be explained if the black hole is surrounded by a thick torus of at least 7 solar masses worth of dust, with a radius of at least 3 light-years. Such a large dust mass so close to the supermassive black hole implies that these dust grains cant have been newly formed so they must have already been there from the dusty torus of the galactic nucleus.The authors point out that this dusty ring solves one of the mysteries of this disruption candidate: because the dust also scatters some of the optical light, this explains why the optical light curve didnt decay as quickly as wed expect.Conveniently, the authors model of this event can be easily tested: it predicts a sharp decrease in the mid-infrared flux in the near future. Continued monitoring of F010042237 in mid-infrared channels should therefore soon be able to confirm our picture of this event. If were correct, these observations provide us with an excellent opportunity to learn about the environments around supermassive black holes.CitationLiming Dou et al 2017 ApJL 841 L8. doi:10.3847/2041-8213/aa7130

The fading behavior of the propagating VLF signal during the recovery time of solar flares.

NASA Astrophysics Data System (ADS)

Bouderba, Yasmina; Tribeche, Mouloud; Nait Amor, Samir

2016-07-01

The VLF radio signal propagating in the waveguide delimited by the Earth's surface and the D-layer of the ionosphere undergoes important modifications due to solar flares. In this work we focus on the NRK (37.5 kHz) VLF transmitter signal that propagates along the medium path to Algiers receiver (distance=3495 km). The signal analysis of two different flare classes shows that the perturbation due to a week flare of C2.1 (I _{max}=2.1 x 10 ^{-6} W/m ^{2}) class are less important than the medium one of M3.2 (I _{max}=3.2 x 10 ^{-5} W/m ^{2}) class. This leads to the fast recovery to the normal ionospheric condition after the weak solar flare while the medium solar flare takes more time. Additionally, the study of the signal amplitude behaviors by means of the LWPC code shows that the fading displacement toward the transmitter is more significant in the case of M3.2 flare than C2.1 class.

ANATOMY OF A SOLAR FLARE: MEASUREMENTS OF THE 2006 DECEMBER 14 X-CLASS FLARE WITH GONG, HINODE, AND RHESSI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, S. A.; Zharkov, S.; Zharkova, V. V.

2011-10-01

Some of the most challenging observations to explain in the context of existing flare models are those related to the lower atmosphere and below the solar surface. Such observations, including changes in the photospheric magnetic field and seismic emission, indicate the poorly understood connections between energy release in the corona and its impact in the photosphere and the solar interior. Using data from Hinode, TRACE, RHESSI, and GONG we study the temporal and spatial evolution of the 2006 December 14 X-class flare in the chromosphere, photosphere, and the solar interior. We investigate the connections between the emission at various atmosphericmore » depths, including acoustic signatures obtained by time-distance and holography methods from the GONG data. We report the horizontal displacements observed in the photosphere linked to the timing and locations of the acoustic signatures we believe to be associated with this flare, their vertical and horizontal displacement velocities, and their potential implications for current models of flare dynamics.« less

Fast transient X-rays from flare stars and RS CVn binaries

NASA Astrophysics Data System (ADS)

Rao, A. R.; Vahia, M. N.

1987-12-01

The authors have studied the fast transient X-ray (FTX) observations of the Ariel V satellite. They find that the FTX have characteristics very similar to the stellar flares detected in flare stars and RS CVn binaries by other satellites. It is found that, of the possible candidate objects, only the flare stars and RS CVn binaries can be associated with the Ariel V observations. 11 new flare stars and RS CVn binaries are associated with the FTX. This brings the total number of identifications with the flare stars and RS CVn binaries to 17. The authors further study the flare properties and correlate the peak X-ray luminosity of these Ariel V sources with the bolometric luminosity of the candidate stars. They discuss a solar flare model and show that the observed correlation can be explained under the assumption of constant temperature loops of binary sizes.

Incidence and factors related to flare-ups in a graduate endodontic programme.

PubMed

Iqbal, M; Kurtz, E; Kohli, M

2009-02-01

To investigate the incidence and factors related to endodontic flare-ups in nonsurgical root canal treatment (NSRCT) cases completed by graduate endodontic residents at University of Pennsylvania, USA. Residents at University of Pennsylvania enter all clinical patient records into an electronic database called PennEndo database. Analysis of records of 6580 patients treated from September 2000 to July 2005 revealed a total of 26 patients with flare-ups (0.39%). Patients were categorized to have undergone flare-up when they attended for an unscheduled visit and active treatment, and when they suffered from severe pain and or swelling after initiation or continuation of NSRCT. SAS software was used to develop a logistic regression model with flare-up as a dependent variable. Independent variables included in the model were: history of previous pain, one vs. two visit NSRCT, periapical diagnosis, tooth type, rotary versus hand instrumentation, and lateral versus vertical compaction of gutta-percha. The odds for developing a flare-up in teeth with a periapical radiolucency were 9.64 times greater than teeth without a periapical radiolucency (P = 0.0090). There was no statistically significant difference in flare-ups between one and two visits NSRCT. The odds of developing a flare-up increased 40 fold when NSRCT was completed in three or more visits. However, this result may have been confounded by addition of an unscheduled visit in patients suffering from flare-ups. Other independent variables did not have any statistically significant correlations. A low percentage of patients experienced flare-ups during NSRCT procedures. The presence of a periapical lesion was the single most important predictor of flare-ups during NSRCT.

A Statistical Analysis of Loop-Top Motion in Solar Limb Flares

NASA Technical Reports Server (NTRS)

Holman, Gordon D.; Sui, Linhui; Brosius, D. G.; Dennis, Brian R.

2005-01-01

Previous studies of hot, thermal solar flare loops imaged with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) have identified several flares for which the loop top shrinks downward early in the impulsive phase and then expands upward later in the impulsive phase (Sui & Holman 2003; Sui, Holman & Dennis 2004; Veronig et al. 2005). This early downward motion is not predicted by flare models. We study a statistical sample of RHESSI flares to assess how common this evolution is and to better characterize it. In a sample of 88 flares near the solar lin$ that show identifiable loop structure in RHESSI images, 66% (58 flares) showed downward loop-top motion followed by upward motion. We therefore conclude that the early downward motion is a frequent characteristic of flare loops. We obtain the distribution of the timing of the change from downward to upward motion relative to flare start and peak times. We also obtain the distributions of downward and upward speeds.

Hypersonic Wind Tunnel Test of a Flare-type Membrane Aeroshell for Atmospheric Entry Capsules

NASA Astrophysics Data System (ADS)

Yamada, Kazuhiko; Koyama, Masashi; Kimura, Yusuke; Suzuki, Kojiro; Abe, Takashi; Koichi Hayashi, A.

A flexible aeroshell for atmospheric entry vehicles has attracted attention as an innovative space transportation system. In this study, hypersonic wind tunnel tests were carried out to investigate the behavior, aerodynamic characteristics and aerodynamic heating environment in hypersonic flow for a previously developed capsule-type vehicle with a flare-type membrane aeroshell made of ZYLON textile sustained by a rigid torus frame. Two different models with different flare angles (45º and 60º) were tested to experimentally clarify the effect of flare angle. Results indicate that flare angle of aeroshell has significant and complicate effect on flow field and aerodynamic heating in hypersonic flow at Mach 9.45 and the flare angle is very important parameter for vehicle design with the flare-type membrane aeroshell.

An active role for magnetic fields in solar flares

NASA Technical Reports Server (NTRS)

Rust, D. M.

1976-01-01

Observations of photospheric magnetic fields are reviewed to determine whether changes in such fields can be related to flare activity, assuming that magnetic fields play an active role in providing flare energy. An intimate relation between emerging fields and bright flare knots is noted, and it is shown that the activation and eruption of an H-alpha filament is indicative of a major disruption of a magnetic field just prior to a flare. Observations of twisting motions in a filament just before a flare are discussed, erupting untwisting filaments are taken as unambiguous evidence for restructuring of the magnetic fields associated with flares, and it is argued that magnetic-field changes in the midst of most flares are obvious. It is concluded that successive brightenings in a family of loops may be evidence for the spread of a magnetic-field reconnection point from one field concentration to another and that flares may well take place in regions of field-line reconnection. This latter conclusion is illustrated using an empirical flare model that involves field-line reconnection, filament activation, and emerging magnetic flux.

Effect of Transport Coefficients on Excitation of Flare-induced Standing Slow-mode Waves in Coronal Loops

NASA Astrophysics Data System (ADS)

Wang, Tongjiang; Ofman, Leon; Sun, Xudong; Solanki, Sami K.; Davila, Joseph M.

2018-06-01

Standing slow-mode waves have been recently observed in flaring loops by the Atmospheric Imaging Assembly of the Solar Dynamics Observatory. By means of the coronal seismology technique, transport coefficients in hot (∼10 MK) plasma were determined by Wang et al., revealing that thermal conductivity is nearly suppressed and compressive viscosity is enhanced by more than an order of magnitude. In this study, we use 1D nonlinear MHD simulations to validate the predicted results from the linear theory and investigate the standing slow-mode wave excitation mechanism. We first explore the wave trigger based on the magnetic field extrapolation and flare emission features. Using a flow pulse driven at one footpoint, we simulate the wave excitation in two types of loop models: Model 1 with the classical transport coefficients and Model 2 with the seismology-determined transport coefficients. We find that Model 2 can form the standing wave pattern (within about one period) from initial propagating disturbances much faster than Model 1, in better agreement with the observations. Simulations of the harmonic waves and the Fourier decomposition analysis show that the scaling law between damping time (τ) and wave period (P) follows τ ∝ P 2 in Model 2, while τ ∝ P in Model 1. This indicates that the largely enhanced viscosity efficiently increases the dissipation of higher harmonic components, favoring the quick formation of the fundamental standing mode. Our study suggests that observational constraints on the transport coefficients are important in understanding both the wave excitation and damping mechanisms.

Low-latitude Ionospheric Heating during Solar Flares

NASA Astrophysics Data System (ADS)

Klenzing, J.; Chamberlin, P. C.; Qian, L.; Haaser, R. A.; Burrell, A. G.; Earle, G. D.; Heelis, R. A.; Simoes, F. A.

2013-12-01

The advent of the Solar Dynamics Observatory (SDO) represents a leap forward in our capability to measure rapidly changing transient events on the sun. SDO measurements are paired with the comprehensive low latitude measurements of the ionosphere and thermosphere provided by the Communication/Navigation Outage Forecast System (C/NOFS) satellite and state-of-the-art general circulation models to discuss the coupling between the terrestrial upper atmosphere and solar radiation. Here we discuss ionospheric heating as detected by the Coupled Ion-Neutral Dynamics Investigation (CINDI) instrument suite on the C/NOFS satellite during solar flares. Also discusses is the necessity of decoupling the heating due to increased EUV irradiance and that due to geomagnetic storms, which sometimes occur with flares. Increases in both the ion temperature and ion density in the subsolar topside ionosphere are detected within 77 minutes of the 23 Jan 2012 M-class flare, and the observed results are compared with the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) using the Flare Irradiance Spectral Model (FISM) as an input.

On the Origin of Pulsations of Sub-THz Emission from Solar Flares

NASA Astrophysics Data System (ADS)

Zaitsev, V. V.; Stepanov, A. V.; Kaufmann, P.

2014-08-01

We propose a model to explain fast pulsations in sub-THz emission from solar flares. The model is based on the approach of a flaring loop as an equivalent electric circuit and explains the pulse-repetition rate, the high-quality factor, Q≥103, low modulation depth, pulse synchronism at different frequencies, and the dependence of the pulse-repetition rate on the emission flux, observed by Kaufmann et al. ( Astrophys. J. 697, 420, 2009). We solved the nonlinear equation for electric current oscillations using a Van der Pol method and found the steady-state value for the amplitude of the current oscillations. Using the pulse rate variation during the flare on 4 November 2003, we found a decrease of the electric current from 1.7×1012 A in the flare maximum to 4×1010 A just after the burst. Our model is consistent with the plasma mechanism of sub-THz emission suggested recently by Zaitsev, Stepanov, and Melnikov ( Astron. Lett. 39, 650, 2013).

Time Variations of Observed H α Line Profiles and Precipitation Depths of Nonthermal Electrons in a Solar Flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falewicz, Robert; Radziszewski, Krzysztof; Rudawy, Paweł

2017-10-01

We compare time variations of the H α and X-ray emissions observed during the pre-impulsive and impulsive phases of the C1.1-class solar flare on 2013 June 21 with those of plasma parameters and synthesized X-ray emission from a 1D hydrodynamic numerical model of the flare. The numerical model was calculated assuming that the external energy is delivered to the flaring loop by nonthermal electrons (NTEs). The H α spectra and images were obtained using the Multi-channel Subtractive Double Pass spectrograph with a time resolution of 50 ms. The X-ray fluxes and spectra were recorded by RHESSI . Pre-flare geometric andmore » thermodynamic parameters of the model and the delivered energy were estimated using RHESSI data. The time variations of the X-ray light curves in various energy bands and those of the H α intensities and line profiles were well correlated. The timescales of the observed variations agree with the calculated variations of the plasma parameters in the flaring loop footpoints, reflecting the time variations of the vertical extent of the energy deposition layer. Our result shows that the fast time variations of the H α emission of the flaring kernels can be explained by momentary changes of the deposited energy flux and the variations of the penetration depths of the NTEs.« less

Photospheric Spots and Flare on the Active Dwarf Star FR Cnc

NASA Astrophysics Data System (ADS)

Kozhevnikova, A. V.; Kozhevnikov, V. P.; Alekseev, I. Yu.

2018-03-01

We perform analysis of new BVRI photometry of young active dwarf star FR Cnc (K7V), obtained at Kourovka astronomical observatory of Ural Federal University with the help of multichannel electrophotometer in February 2010. The lightcurve displays sinusoidal rotation modulation with the amplitude of 0m.15 in V band. Reddening of the brightness at the photometric minimum confirms that this modulation is caused by cold photospheric spots. An analysis of the spottedness distribution in terms of a zonal model based on our own and published data shows that the spots are localized at lower and middle latitudes from 47° to 56°, occupy 10-21% of the star's area, and are colder than the photosphere by 1650 K. A flare was detected on February 3, 2010, at a time corresponding to HJD=2455231. 3136. A maximum amplitude of 0m.11 was observed in the B band, the amplitudes in the V, R, and I bands were 0m.04, 0m.03, and 0m.02, respectively, and the duration of the flare was 32.5 min. It was noted that the flare occurred near the maximum spottedness of the star. The calculated total energy of the flare was 2.4·1033 and 1.3·1033 erg in the B and V bands, respectively. The flare was found to have an afterglow, with an overall increase in the star's brightness by 0m.02 in the B band after the flare compared to the pre-flare level.

Explosive plasma flows in a solar flare

NASA Technical Reports Server (NTRS)

Zarro, Dominic M.; Canfield, Richard C.; Metcalf, Thomas R.; Strong, Keith T.

1988-01-01

Solar Maximum Mission soft X-ray data and Sacramento Peak Observatory H-alpha observations are combined in a study of the impulsive phase of a solar flare. A blue asymmetry, indicative of upflows, was observed in the coronal Ca XIX line during the soft X-ray rise phase. A red asymmetry, indicative of downflows, was observed simultaneously in chromospheric H-alpha emitted from bright flare kernels during the period of hard X-ray emission. Combining the velocity data with a measurement of coronal electron density, it is shown that the impulsive phase momentum of upflowing soft X-ray-emitting plasma equalled that of the downflowing H-alpha-emitting plasma to within one order of magnitude. In particular, the momentum of the upflowing plasma was 2 x 10 to the 21st g cm/s while that of the downflowing plasma was 7 x 10 to the 21st g cm/s, with a factor of 2 uncertainty on each value. This equality supports the explosive chromospheric evaporation model of solar flares, in which a sudden pressure increase at the footprint of a coronal loop produces oppositely directed flows in the heated plasma.

Spectropolarimetric Inversions of the Ca II 8542 Å Line in an M-class Solar Flare

NASA Astrophysics Data System (ADS)

Kuridze, D.; Henriques, V. M. J.; Mathioudakis, M.; Rouppe van der Voort, L.; de la Cruz Rodríguez, J.; Carlsson, M.

2018-06-01

We study the M1.9-class solar flare SOL2015-09-27T10:40 UT using high-resolution full Stokes imaging spectropolarimetry of the Ca II 8542 Å line obtained with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope. Spectropolarimetric inversions using the non-LTE code NICOLE are used to construct semiempirical models of the flaring atmosphere to investigate the structure and evolution of the flare temperature and magnetic field. A comparison of the temperature stratification in flaring and nonflaring areas reveals strong heating of the flare ribbon during the flare peak. The polarization signals of the ribbon in the chromosphere during the flare maximum become stronger when compared to its surroundings and to pre- and post-flare profiles. Furthermore, a comparison of the response functions to perturbations in the line-of-sight magnetic field and temperature in flaring and nonflaring atmospheres shows that during the flare, the Ca II 8542 Å line is more sensitive to the lower atmosphere where the magnetic field is expected to be stronger. The chromospheric magnetic field was also determined with the weak-field approximation, which led to results similar to those obtained with the NICOLE inversions.

A Comparison between the WATCH Flare Data Statistical Properties and Predictions of the Statistical Flare Model

NASA Astrophysics Data System (ADS)

Crosby, N.; Georgoulis, M.; Vilmer, N.

1999-10-01

Solar burst observations in the deka-keV energy range originating from the WATCH experiment aboard the GRANAT spacecraft were used to perform frequency distributions built on measured X-ray flare parameters (Crosby et al., 1998). The results of the study show that: 1- the overall distribution functions are robust power laws extending over a number of decades. The typical parameters of events (total counts, peak count rates, duration) are all correlated to each other. 2- the overall distribution functions are the convolution of significantly different distribution functions built on parts of the whole data set filtered by the event duration. These "partial" frequency distributions are still power law distributions over several decades, with a slope systematically decreasing with increasing duration. 3- No correlation is found between the elapsed time interval between successive bursts arising from the same active region and the peak intensity of the flare. In this paper, we attempt a tentative comparison between the statistical properties of the self-organized critical (SOC) cellular automaton statistical flare models (see e.g. Lu and Hamilton (1991), Georgoulis and Vlahos (1996, 1998)) and the respective properties of the WATCH flare data. Despite the inherent weaknesses of the SOC models to simulate a number of physical processes in the active region, it is found that most of the observed statistical properties can be reproduced using the SOC models, including the various frequency distributions and scatter plots. We finally conclude that, even if SOC models must be refined to improve the physical links to MHD approaches, they nevertheless represent a good approach to describe the properties of rapid energy dissipation and magnetic field annihilation in complex and magnetized plasmas. Crosby N., Vilmer N., Lund N. and Sunyaev R., A&A; 334; 299-313; 1998 Crosby N., Lund N., Vilmer N. and Sunyaev R.; A&A Supplement Series; 130, 233, 1998 Georgoulis M. and Vlahos L., 1996, Astrophy. J. Letters, 469, L135 Georgoulis M. and Vlahos L., 1998, in preparation Lu E.T. and Hamilton R.J., 1991, Astroph. J., 380, L89

Ground-based detection of G star superflares with NGTS

NASA Astrophysics Data System (ADS)

Jackman, James A. G.; Wheatley, Peter J.; Pugh, Chloe E.; Gänsicke, Boris T.; Gillen, Edward; Broomhall, Anne-Marie; Armstrong, David J.; Burleigh, Matthew R.; Chaushev, Alexander; Eigmüller, Philipp; Erikson, Anders; Goad, Michael R.; Grange, Andrew; Günther, Maximilian N.; Jenkins, James S.; McCormac, James; Raynard, Liam; Thompson, Andrew P. G.; Udry, Stéphane; Walker, Simon; Watson, Christopher A.; West, Richard G.

2018-07-01

We present high cadence detections of two superflares from a bright G8 star (V = 11.56) with the Next Generation Transit Survey (NGTS). We improve upon previous superflare detections by resolving the flare rise and peak, allowing us to fit a solar flare inspired model without the need for arbitrary break points between rise and decay. Our data also enables us to identify substructure in the flares. From changing star-spot modulation in the NGTS data, we detect a stellar rotation period of 59 h, along with evidence for differential rotation. We combine this rotation period with the observed ROSAT X-ray flux to determine that the star's X-ray activity is saturated. We calculate the flare bolometric energies as 5.4^{+0.8}_{-0.7}× 10^{34} and 2.6^{+0.4}_{-0.3}× 10^{34} erg and compare our detections with G star superflares detected in the Kepler survey. We find our main flare to be one of the largest amplitude superflares detected from a bright G star. With energies more than 100 times greater than the Carrington event, our flare detections demonstrate the role that ground-based instruments such as NGTS can have in assessing the habitability of Earth-like exoplanets, particularly in the era of PLATO.

Ground-based detection of G star superflares with NGTS

NASA Astrophysics Data System (ADS)

Jackman, James A. G.; Wheatley, Peter J.; Pugh, Chloe E.; Gänsicke, Boris T.; Gillen, Edward; Broomhall, Anne-Marie; Armstrong, David J.; Burleigh, Matthew R.; Chaushev, Alexander; Eigmüller, Philipp; Erikson, Anders; Goad, Michael R.; Grange, Andrew; Günther, Maximilian N.; Jenkins, James S.; McCormac, James; Raynard, Liam; Thompson, Andrew P. G.; Udry, Stéphane; Walker, Simon; Watson, Christopher A.; West, Richard G.

2018-04-01

We present high cadence detections of two superflares from a bright G8 star (V = 11.56) with the Next Generation Transit Survey (NGTS). We improve upon previous superflare detections by resolving the flare rise and peak, allowing us to fit a solar flare inspired model without the need for arbitrary break points between rise and decay. Our data also enables us to identify substructure in the flares. From changing starspot modulation in the NGTS data we detect a stellar rotation period of 59 hours, along with evidence for differential rotation. We combine this rotation period with the observed ROSAT X-ray flux to determine that the star's X-ray activity is saturated. We calculate the flare bolometric energies as 5.4^{+0.8}_{-0.7}× 10^{34}and 2.6^{+0.4}_{-0.3}× 10^{34}erg and compare our detections with G star superflares detected in the Kepler survey. We find our main flare to be one of the largest amplitude superflares detected from a bright G star. With energies more than 100 times greater than the Carrington event, our flare detections demonstrate the role that ground-based instruments such as NGTS can have in assessing the habitability of Earth-like exoplanets, particularly in the era of PLATO.

Numerical Modeling of Flare-productive Active Regions of the Sun

NASA Astrophysics Data System (ADS)

Toriumi, S.; Takasao, S.

2017-12-01

It is known that strong flare events on the Sun take place in active regions (ARs), especially in delta sunspots with closely-packed positive and negative polarities. The delta spots are produced as a result of complex magnetic flux emergence and have strong-field, highly-sheared polarity inversion lines (PILs). Here we report on the numerical simulations of four types of such flare-productive ARs, namely, (1) Spot-Spot, a complex AR with AR-sized PIL, (2) Spot-Satellite, in which a newly-emerging bipole appears next to the pre-existing sunspot, (3) Quadrupole, where two emerging bipoles collide against each other, and (4) Inter-AR, the flares occurring between two separated ARs. We reproduced these four cases by conducting a series of 3D MHD flux emergence simulations and found, for example, that the sheared PILs in these ARs are created through the stretching and advection of horizontal magnetic fields due to relative spot motions. As ARs develop, free magnetic energy becomes stored in the corona, which could be eventually released through flare eruptions. In the presentation, we also mention the relationship between the HMI/SHARP parameters measured in the photosphere and the free energy stored in the corona, and discuss why these parameters successfully predict the flares.

Multiwavelength analysis of a well observed flare from SMM. [Solar Maximum Mission

NASA Technical Reports Server (NTRS)

Macneice, P.; Pallavicini, R.; Mason, H. E.; Simnett, G. M.; Antonucci, E.; Shine, R. A.; Dennis, B. R.

1985-01-01

Observations of an M 1.4 flare which began at 17:00 UT on November 12, 1980, are presented and analyzed. Ground based H-alpha and magnetogram data have been combined with EUV, soft and hard X-ray observations made with instruments on-board the Solar Maximum Mission satellite. The preflare phase was marked by a gradual brightening of the flare site in O v and the disappearance of an H-alpha filament. Filament ejecta were seen in O v moving southward at a speed of about 60 km/s, before the impulsive phase. The flare loop footpoints brightened in H-alpha and the Ca XIX resonance line broadened dramatically 2 min before the impulsive phase. Nonthermal hard X-ray emission was detected from the loop footpoints during the impulsive phase, while during the same period blue-shifts corresponding to upflows of 200-250 km/s were seen in Ca XIX. Evidence was found for energy deposition in both the chromosphere and corona at a number of stages during the flare. Two widely studied mechanisms for the production of the high temperature soft X-ray flare plasma in the corona are considered, i.e. chromospheric evaporation, and a model in which the heating and transfer of material occurs between flux tubes during reconnection.

Sixteen years of X-ray monitoring of Sagittarius A*: Evidence for a decay of the faint flaring rate from 2013 August, 13 months before a rise in the bright flaring rate

NASA Astrophysics Data System (ADS)

Mossoux, Enmanuelle; Grosso, Nicolas

2017-08-01

Context. X-ray flaring activity from the closest supermassive black hole Sagittarius A* (Sgr A*) located at the center of our Galaxy has been observed since 2000 October 26 thanks to the current generation of X-ray facilities. In a study of X-ray flaring activity from Sgr A* using Chandra and XMM-Newton public observations from 1999 to 2014 and Swift monitoring in 2014, it was argued that the "bright and very bright" flaring rate has increased from 2014 August 31. Aims: As a result of additional observations performed in 2015 with Chandra, XMM-Newton, and Swift (total exposure of 482 ks), we seek to test the significance and persistence of this increase of flaring rate and to determine the threshold of unabsorbed flare flux or fluence leading to any change of flaring rate. Methods: We reprocessed the Chandra, XMM-Newton, and Swift data from 1999 to 2015 November 2. From these data, we detected the X-ray flares via our two-step Bayesian blocks algorithm with a prior on the number of change points properly calibrated for each observation. We improved the Swift data analysis by correcting the effects of the target variable position on the detector and we detected the X-ray flares with a 3σ threshold on the binned light curves. The mean unabsorbed fluxes of the 107 detected flares were consistently computed from the extracted spectra and the corresponding calibration files, assuming the same spectral parameters. We constructed the observed distribution of flare fluxes and durations from the XMM-Newton and Chandra detections. We corrected this observed distribution from the detection biases to estimate the intrinsic distribution of flare fluxes and durations. From this intrinsic distribution, we determined the average flare detection efficiency for each XMM-Newton, Chandra, and Swift observation. We finally applied the Bayesian blocks algorithm on the arrival times of the flares corrected from the corresponding efficiency. Results: We confirm a constant overall flaring rate from 1999 to 2015 and a rise in the flaring rate by a factor of three for the most luminous and most energetic flares from 2014 August 31, I.e., about four months after the pericenter passage of the Dusty S-cluster Object (DSO)/G2 close to Sgr A*. In addition, we identify a decay of the flaring rate for the less luminous and less energetic flares from 2013 August and November, respectively, I.e., about 10 and 7 months before the pericenter passage of the DSO/G2 and 13 and 10 months before the rise in the bright flaring rate. Conclusions: The decay of the faint flaring rate is difficult to explain in terms of the tidal disruption of a dusty cloud since it occurred well before the pericenter passage of the DSO/G2, whose stellar nature is now well established. Moreover, a mass transfer from the DSO/G2 to Sgr A* is not required to produce the rise in the bright flaring rate since the energy saved by the decay of the number of faint flares during a long period of time may be later released by several bright flares during a shorter period of time.

Mass ejections. [during solar flares

NASA Technical Reports Server (NTRS)

Rust, D. M.; Hildner, E.; Hansen, R. T.; Dryer, M.; Mcclymont, A. N.; Mckenna-Lawlor, S. M. P.; Mclean, D. J.; Schmahl, E. J.; Steinolfson, R. S.; Tandberg-Hanssen, E.

1980-01-01

Observations and model simulations of solar mass ejection phenomena are examined in an investigation of flare processes. Consideration is given to Skylab and other observations of flare-associated sprays, eruptive prominences, surges and coronal transients, and to MHD, gas dynamic and magnetic loop models developed to account for them. Magnetic forces are found to confine spray material, which originates in preexisting active-region filaments, within steadily expanding loops, while surges follow unmoving, preexisting magnetic field lines. Simulations of effects of a sudden pressure pulse at the bottom of the corona are found to exhibit many characteristics of coronal transients associated with flares, and impulsive heating low in the chromosphere is found to be able to account for surges. The importance of the magnetic field as the ultimate source of energy which drives eruptive phenomena as well as flares is pointed out.

Time behavior of solar flare particles to 5 AU

NASA Technical Reports Server (NTRS)

Haffner, J. W.

1972-01-01

A simple model of solar flare radiation event particle transport is developed to permit the calculation of fluxes and related quantities as a function of distance from the sun (R). This model assumes the particles spiral around the solar magnetic field lines with a constant pitch angle. The particle angular distributions and onset plus arrival times as functions of energy at 1 AU agree with observations if the pitch angle distribution peaks near 90 deg. As a consequence the time dependence factor is essentially proportional to R/1.7, (R in AU), and the event flux is proportional to R/2.

40 CFR 60.107a - Monitoring of emissions and operations for fuel gas combustion devices and flares.

Code of Federal Regulations, 2013 CFR

2013-07-01

... for fuel gas combustion devices and flares. 60.107a Section 60.107a Protection of Environment... combustion devices and flares. (a) Fuel gas combustion devices subject to SO2 or H2S limit and flares subject to H2S concentration requirements. The owner or operator of a fuel gas combustion device that is...

40 CFR 60.107a - Monitoring of emissions and operations for fuel gas combustion devices and flares.

Code of Federal Regulations, 2014 CFR

2014-07-01

... for fuel gas combustion devices and flares. 60.107a Section 60.107a Protection of Environment... combustion devices and flares. (a) Fuel gas combustion devices subject to SO2 or H2S limit and flares subject to H2S concentration requirements. The owner or operator of a fuel gas combustion device that is...

Environmental Assessment: Recapitalization of the 49th WG Combat Capabilities and Capacities, Holloman Air Force Base, New Mexico

DTIC Science & Technology

2011-07-01

of Liquid Oxygen (LOX). The new facilities would provide for the specific needs to maintain the F-16 engine, electronics , and maintenance... electronic countermeasures, and electronic counter countermeasures. 500 AGL to 40,000 MSL 0.5 to 1.0 hour Night Operations Aircraft intercepts (1...defensive maneuvering, chaff/flare, and electronic countermeasures. 2,000 AGL to 40,000 MSL 0.75 to 1.5 hour (Dissimilar) Air Combat Tactics

Study of the post-flare loops on 29 July 1973. I - Dynamics of the X-ray loops

NASA Technical Reports Server (NTRS)

Nolte, J. T.; Gerassimenko, M.; Krieger, A. S.; Petrasso, R. D.; Svestka, Z.

1979-01-01

We derive an empirical model of the X-ray emitting post-flare loops observed during the decay phase of the 29 July 1973 flare. We find that the loops are elliptical, with the brightest emitting region at the tops. We determine the height, velocity of growth, and ratio of height to width of the loops at times from 3 to 12 hr after the flare onset.

Boundary-layer transition on a flared cone in a Mach 6 quiet wind tunnel

NASA Astrophysics Data System (ADS)

Hofferth, Jerrod; Saric, William

2010-11-01

The Mach 6 Quiet Tunnel at Texas A&M is a low-disturbance blowdown facility suitable for boundary-layer stability and transition research. Following its reactivation in 2009, initial testing confirmed the presence of low-disturbance (< 0.1% Pt^'/Pt) freestream flow at select locations on the centerline of the nozzle for settling chamber pressures up to 10 atm, and a fully-traversed freestream flow-quality assessment is currently underway. As a third performance benchmark to complement these direct measurements, the present work measures the transition location on the NASA Langley 93-10 flared-cone model. This model has a 0.5m length, beginning as a 5^o half-angle circular cone. At the X=254mm station, a flare of surface radius 2.35m begins which is intended to induce transition within the quiet test core. Boundary-layer transition is detected on the thin-walled model by an observed surface temperature rise using an array of 51 embedded thermocouples. Transition data are presented for a sharp (2.5 μm) nose-tip radius case for comparison with the Lachowicz & Chokani (1996 data). Data for larger-radius nose-tips are also presented.

Reconstruction of a Large-scale Pre-flare Coronal Current Sheet Associated with a Homologous X-shaped Flare

NASA Astrophysics Data System (ADS)

Jiang, Chaowei; Yan, Xiaoli; Feng, Xueshang; Duan, Aiying; Hu, Qiang; Zuo, Pingbing; Wang, Yi

2017-11-01

As a fundamental magnetic structure in the solar corona, electric current sheets (CSs) can form either prior to or during a solar flare, and they are essential for magnetic energy dissipation in the solar corona because they enable magnetic reconnection. However, the static reconstruction of a CS is rare, possibly due to limitations that are inherent in the available coronal field extrapolation codes. Here we present the reconstruction of a large-scale pre-flare CS in solar active region 11967 using an MHD-relaxation model constrained by the SDO/HMI vector magnetogram. The CS is associated with a set of peculiar homologous flares that exhibit unique X-shaped ribbons and loops occurring in a quadrupolar magnetic configuration.This is evidenced by an ’X’ shape, formed from the field lines traced from the CS to the photosphere. This nearly reproduces the shape of the observed flare ribbons, suggesting that the flare is a product of the dissipation of the CS via reconnection. The CS forms in a hyperbolic flux tube, which is an intersection of two quasi-separatrix layers. The recurrence of the X-shaped flares might be attributed to the repetitive formation and dissipation of the CS, as driven by the photospheric footpoint motions. These results demonstrate the power of a data-constrained MHD model in reproducing a CS in the corona as well as providing insight into the magnetic mechanism of solar flares.

Reconnection on the Sun

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-05-01

Because the Sun is so close, it makes an excellent laboratory to study processes we cant examinein distant stars. One openquestion is that of how solar magnetic fields rearrange themselves, producing the tremendous releases of energy we observe as solar flares and coronal mass ejections (CMEs).What is Magnetic Reconnection?Magnetic reconnection occurs when a magnetic field rearranges itself to move to a lower-energy state. As field lines of opposite polarity reconnect, magnetic energy is suddenly converted into thermal and kinetic energy.This processis believed to be behind the sudden releases of energy from the solar surface in the form of solar flares and CMEs. But there are many different models for how magnetic reconnection could occur in the magnetic field at the Suns surface, and we arent sure which one of these reconnection types is responsible for the events we see.Recently, however, several studies have been published presenting some of the first observational support of specific reconnection models. Taken together, these observations suggest that there are likely several different types of reconnection happening on the solar surface. Heres a closer look at two of these recent publications:A pre-eruption SDO image of a flaring region (b) looks remarkably similar to a 3D cartoon for typical breakout configuration (a). Click for a closer look! [Adapted from Chen et al. 2016]Study 1:Magnetic BreakoutLed by Yao Chen (Shandong University in China), a team of scientists has presented observations made by the Solar Dynamics Observatory (SDO) of a flare and CME event that appears to have been caused by magnetic breakout.In the magnetic breakout model, a series of loops in the Suns lower corona are confined by a surrounding larger loop structure called an arcade higher in the corona. As the lower loops push upward, reconnection occurs in the upper corona, removing the overlying, confining arcade. Without that extra confinement, the lower coronal loops expand upward, erupting from the solar surface.Snapshots from the SDO side view (left and center) and STEREO overhead view (right). The three rows show the time evolution of the double-loop structure after the initial flare. In the STEREO view, you can see the central footpoints of the loops slip to the left. [Gou et al. 2016]In the SDO observations presented by Chen and collaborators, the pre-flare/CME structures look remarkably like the structures predicted in the breakout model. Sequential heating of loops can be seen as the breakout reconnection starts, followed by anenormous flare and CME as the lower loops erupt outward.Study 2: Slipping ReconnectionA team of scientists from the University of Science and Technology of China, led by Tingyu Gou and Rui Liu, have presented the first stereoscopic observation of slipping reconnection in the Sun, made by the two-spacecraft Solar Terrestrial Relations Observatory (STEREO).In slipping reconnection, magnetic field lines continuously exchange connectivities with their neighbors, causing them to slip through plasma. Observations by STEREO of a flaring double-loop system revealed that the central footpoints the endpoints where the loops are anchored to the solar surface slipped sideways after a flare.The authors model of the double-loop structure at two different times, during which the central footpoint slips from point C to D. Projections onto the XY and YZ planes show STEREOs and SDOs views, respectively. [Gou et al. 2016]The authors reconstructed a 3D model of the loop system using the overhead observations from STEREO and a simultaneous side view from SDO. They speculate that the slipping reconnection was likely triggered by the initial solar flare.Double BonusCheck out the videos belowto watch these processes happen!This first video is from Chen et al. 2016, and shows the SDO view of coronal loops in three wavelengths. If you watch carefully, you can see the sequential brightening of loops signs of the breakout reconnection before the flare and CME.http://aasnova.org/wp-content/uploads/2016/05/breakout.mp4This second video is from Gou et al. 2016, and shows the SDO side view (left and center panels) and STEREO top view (right panel) of a flare and the slipping reconnection that occurred after. Keep your eye on the STEREO view between 0:02 and 0:04 to watch the central footpoint slide left.http://aasnova.org/wp-content/uploads/2016/05/slipping.mp4CitationYao Chen et al 2016 ApJ 820 L37. doi:10.3847/2041-8205/820/2/L37Tingyu Gou et al 2016 ApJ 821 L28. doi:10.3847/2041-8205/821/2/L28

Wavelength Dependence of Solar Irradiance Enhancement During X-Class Flares and Its Influence on the Upper Atmosphere

NASA Technical Reports Server (NTRS)

Huang, Yanshi; Richmond, Arthur D.; Deng, Yue; Chamberlin, Phillip C.; Qian, Liying; Solomon, Stanley C.; Roble, Raymond G.; Xiao, Zuo

2013-01-01

The wavelength dependence of solar irradiance enhancement during flare events is one of the important factors in determining how the Thermosphere-Ionosphere (T-I) system responds to flares. To investigate the wavelength dependence of flare enhancement, the Flare Irradiance Spectral Model (FISM) was run for 61 X-class flares. The absolute and the percentage increases of solar irradiance at flare peaks, compared to pre-flare conditions, have clear wavelength dependences. The 0-14 nm irradiance increases much more (approx. 680% on average) than that in the 14-25 nm waveband (approx. 65% on average), except at 24 nm (approx. 220%). The average percentage increases for the 25-105 nm and 122-190 nm wavebands are approx. 120% and approx. 35%, respectively. The influence of 6 different wavebands (0-14 nm, 14-25 nm, 25-105 nm, 105- 120 nm, 121.56 nm, and 122-175 nm) on the thermosphere was examined for the October 28th, 2003 flare (X17-class) event by coupling FISM with the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) under geomagnetically quiet conditions (Kp=1). While the enhancement in the 0-14 nm waveband caused the largest enhancement of the globally integrated solar heating, the impact of solar irradiance enhancement on the thermosphere at 400 km is largest for the 25-105 nm waveband (EUV), which accounts for about 33 K of the total 45 K temperature enhancement, and approx. 7.4% of the total approx. 11.5% neutral density enhancement. The effect of 122-175 nm flare radiation on the thermosphere is rather small. The study also illustrates that the high-altitude thermospheric response to the flare radiation at 0-175 nm is almost a linear combination of the responses to the individual wavebands. The upper thermospheric temperature and density enhancements peaked 3-5 h after the maximum flare radiation.

Wavelength Dependence of Solar Irradiance Enhancement During X-class Flares and Its Influence on the Upper Atmosphere

NASA Technical Reports Server (NTRS)

Huang, Yanshi; Richmond, A. D.

2013-01-01

The wavelength dependence of solar irradiance enhancement during flare events is one of the important factors in determining how the Thermosphere-Ionosphere (TI) system responds to flares. To investigate the wavelength dependence of flare enhancement, the Flare Irradiance Spectral Model (FISM) was run for 61X-class flares. The absolute and the percentage increases of solar irradiance at flare peaks, compared to pre-flare conditions, have clear wavelength dependences. The 0-4 nm irradiance increases much more ((is) approximately 680 on average) than that in the 14-25 nm waveband ((is) approximately 65 on average), except at 24 nm ( (is) approximately 220). The average percentage increases for the 25-105 nm and 122-190 nm wave bands are approximately 120 and approximately 35, respectively. The influence of 6 different wavebands (0-14 nm, 14-25 nm, 25-105 nm, 105-120 nm, 121.56 nm,and122-175 nm) on the thermosphere was examined for the October 28th, 2003 flare (X17-class) event by coupling FISM with the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model(TIE-GCM) under geomagnetically quiet conditions (Kp=1). While the enhancement in the0-14nm waveband caused the largest enhancement of the globally integrated solar heating, the impact of solar irradiance enhancement on the thermosphere at 400 km is largest for the 25-105 nm waveband (EUV), which accounts for about 33 K of the total 45 K temperature enhancement, and approximately 7.4% of the total approximately 11.5% neutral density enhancement. The effect of 122-175 nm flare radiation on the thermosphere is rather small. The study also illustrates that the high-altitude thermospheric response to the flare radiation at 0-175 nm is almost a linear combination of the responses to the individual wavebands. The upper thermospheric temperature and density enhancements peaked 3-5 h after the maximum flare radiation.

The flares of August 1972

NASA Technical Reports Server (NTRS)

Zirin, H.; Tanaka, K.

1972-01-01

Analysis is made of observations of the August, 1972 flares at Big Bear and Tel Aviv, involving monochromatic movies, magnetograms, and spectra. In each flare the observations fit a model of particle acceleration in the chromosphere with emission produced by impart and by heating by the energetic electrons and protons. The region showed twisted flux and high gradients from birth, and flares appear due to strong magnetic shears and gradients across the neutral line produced by sunspot motions. Post flare loops show a strong change from sheared, force-free fields parallel to potential-field-like loops, perpendicular to the neutral line above the surface.

Extremely Rapid X-Ray Flares of TeV Blazars in the RXTE Era

NASA Astrophysics Data System (ADS)

Zhu, S. F.; Xue, Y. Q.; Brandt, W. N.; Cui, W.; Wang, Y. J.

2018-01-01

Rapid flares from blazars in very high-energy (VHE) γ-rays challenge the common understanding of jets of active galactic nuclei (AGNs). The same population of ultra-relativistic electrons is often thought to be responsible for both X-ray and VHE emission. We thus systematically searched for X-ray flares at sub-hour timescales of TeV blazars in the entire Rossi X-ray Timing Explorer archival database. We found rapid flares from PKS 2005‑489 and S5 0716+714, and a candidate rapid flare from 1ES 1101‑232. In particular, the characteristic rise timescale of PKS 2005‑489 is less than half a minute, which, to our knowledge, is the shortest among known AGN flares at any wavelengths. The timescales of these rapid flares indicate that the size of the central supermassive black hole is not a hard lower limit on the physical size of the emission region of the flare. PKS 2005‑489 shows possible hard lags in its flare, which could be attributed to particle acceleration (injection); its flaring component has the hardest spectrum when it first appears. For all flares, the flaring components show similar hard spectra with {{Γ }}=1.7{--}1.9, and we estimate the magnetic field strength B ∼ 0.1–1.0 G by assuming synchrotron cooling. These flares could be caused by inhomogeneity of the jets. Models that can only produce rapid γ-ray flares but little synchrotron activity are less favorable.

Blue-wing enhancement of the chromospheric Mg II h and k lines in a solar flare

NASA Astrophysics Data System (ADS)

Tei, Akiko; Sakaue, Takahito; Okamoto, Takenori J.; Kawate, Tomoko; Heinzel, Petr; UeNo, Satoru; Asai, Ayumi; Ichimoto, Kiyoshi; Shibata, Kazunari

2018-05-01

We performed coordinated observations of AR 12205, which showed a C-class flare on 2014 November 11, with the Interface Region Imaging Spectrograph (IRIS) and the Domeless Solar Telescope (DST) at Hida Observatory. Using spectral data in the Si IV 1403 Å, C II 1335 Å, and Mg II h and k lines from IRIS and the Ca II K, Ca II 8542 Å, and Hα lines from DST, we investigated a moving flare kernel during the flare. In the Mg II h line, the leading edge of the flare kernel showed an intensity enhancement in the blue wing and a smaller intensity of the blue-side peak (h2v) than that of the red-side one (h2r). The blueshift lasted for 9-48 s with a typical speed of 10.1 ± 2.6 km s-1, which was followed by a high intensity and a large redshift with a speed of up to 51 km s-1 detected in the Mg II h line. The large redshift was a common property for all six lines, but the blueshift prior to it was found only in the Mg II lines. Cloud modeling of the Mg II h line suggests that the blue-wing enhancement with such a peak difference could have been caused by a chromospheric-temperature (cool) upflow. We discuss a scenario in which an upflow of cool plasma is lifted up by expanding hot plasma owing to the deep penetration of non-thermal electrons into the chromosphere. Furthermore, we found that the blueshift persisted without any subsequent redshift in the leading edge of the flare kernel during its decaying phase. The cause of such a long-lasting blueshift is also discussed.

Numerical simulations of flares on M dwarf stars. I - Hydrodynamics and coronal X-ray emission

NASA Technical Reports Server (NTRS)

Cheng, Chung-Chieh; Pallavicini, Roberto

1991-01-01

Flare-loop models are utilized to simulate the time evolution and physical characteristics of stellar X-ray flares by varying the values of flare-energy input and loop parameters. The hydrodynamic evolution is studied in terms of changes in the parameters of the mass, energy, and momentum equations within an area bounded by the chromosphere and the corona. The zone supports a magnetically confined loop for which processes are described including the expansion of heated coronal gas, chromospheric evaporation, and plasma compression at loop footpoints. The intensities, time profiles, and average coronal temperatures of X-ray flares are derived from the simulations and compared to observational evidence. Because the amount of evaporated material does not vary linearly with flare-energy input, large loops are required to produce the energy measured from stellar flares.

Sun Emits Mid-Level Flare on October 2, 2014

NASA Image and Video Library

2017-12-08

The sun emitted a mid-level solar flare, peaking at 3:01 p.m. EDT on Oct. 2, 2014. NASA's Solar Dynamics Observatory, which watches the sun 24-hours a day, captured images of the flare. Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel. This flare is classified as an M7.3 flare. M-class flares are one-tenth as powerful as the most powerful flares, which are designated X-class flares. Download high res: svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=11670 Credit: NASA's Goddard Space Flight Center NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Coronal loop hydrodynamics. The solar flare observed on November 12, 1980 revisited: The UV line emission

NASA Astrophysics Data System (ADS)

Betta, R. M.; Peres, G.; Reale, F.; Serio, S.

2001-12-01

We revisit a well-studied solar flare whose X-ray emission originating from a simple loop structure was observed by most of the instruments on board SMM on November 12, 1980. The X-ray emission of this flare, as observed with the XRP, was successfully modeled previously. Here we include a detailed modeling of the transition region and we compare the hydrodynamic results with the UVSP observations in two EUV lines, measured in areas smaller than the XRP rasters, covering only some portions of the flaring loop (the top and the foot-points). The single loop hydrodynamic model, which fits well the evolution of coronal lines (those observed with the XRP and the Fe XXI 1354.1 Å line observed with the UVSP) fails to model the flux level and evolution of the O V 1371.3 Åline.

Is living in a gas-flaring host community associated with being hypertensive? Evidence from the Niger Delta region of Nigeria

PubMed Central

Tobin-West, Charles

2017-01-01

Background Researchers have linked gas flaring to climate change, the hastening of the epidemiological transition and an upsurge in the prevalence of non-communicable diseases. We sought to determine if a relationship exists between residing in a gas-flaring host community and hypertension. Methods We conducted an analytical cross-sectional household survey among residents of 600 households in three gas-flaring and three non-gas-flaring host communities in the Niger Delta region of Nigeria. We took geo-coordinates, administered a modified WHO-STEPS questionnaire and built on Android mobile phones using Open-Data-Kit (ODK) software. We also took biological measurements and carried out descriptive and inferential statistical analysis using SPSS and STATA. Results We interviewed a total of 912 adults: 437 (47.9%) from non-gas-flaring and 475 (52.1%) from gas-flaring host communities. There were differences in level of education (x2=42.99; p=0.00), occupation category (x2=25.42; p=0.00) and BMI category (x2=15.37; 0.003) among the two groups. The overall prevalence of hypertension was 23.7%: 20.7% among persons living in non-gas-flaring host communities compared with 25.3% among persons living in gas-flaring host communities (x2=2.89; p=0.89). Residence in a gas-flaring host community, (AdjOR=1.75; 95% CI=1.11 to 2.74) and mean age (AdjOR=1.05; 95% CI=1.03 to 1.07) were identified as the predictors of hypertension. There was a significant association between hypertension and age, 1.05 (1.04–1.06) while the probability of being hypertensive was higher among residents of gas-flaring host communities between 20 to 40 years and 60 to 80 years. Conclusion There is a need for the relevant agencies to scale up environmental and biological monitoring of air pollutants. The implication of a possible relationship between gas-flaring and hypertension brings to the fore the need for interventions to regulate gas-flaring activities. PMID:29225950

Coronal propagation of flare associated electrons and protons

NASA Technical Reports Server (NTRS)

Schellert, G.; Wibberenz, G.; Kunow, H.

1985-01-01

A statistical study of characteristic times and intensities of 36 solar particle events observed between 1977 and 1979 by the Kiel Cosmic Ray Experiment on board HELIOS-1 and -2 has been carried out. For approx. 0.5 MeV electrons we order the times of maximum and the absolute intensities with respect to angular distance from the parent flare. Discussion of coronal parameters in terms of Reid's model leads to typical time constants for coronal diffusion and escape.

Global Energetics in Solar Flares and Coronal Mass Ejections

NASA Astrophysics Data System (ADS)

Aschwanden, Markus J.

2017-08-01

We present a statistical study of the energetics of coronal mass ejections (CME) and compare it with the magnetic, thermal, and nonthermal energy dissipated in flares. The physical parameters of CME speeds, mass, and kinetic energies are determined with two different independent methods, i.e., the traditional white-light scattering method using LASCO/SOHO data, and the EUV dimming method using AIA/SDO data. We analyze all 860 GOES M- and X-class flare events observed during the first 7 years (2010-2016) of the SDO mission. The new ingredients of our CME modeling includes: (1) CME geometry in terms of a self-similar adiabatic expansion, (2) DEM analysis of CME mass over entire coronal temperature range, (3) deceleration of CME due to gravity force which controls the kinetic and potentail CME energy as a function of time, (4) the critical speed that controls eruptive and confined CMEs, (5) the relationship between the center-of-mass motion during EUV dimming and the leading edge motion observed in white-light coronagraphs. Novel results are: (1) Physical parameters obtained from both the EUV dimming and white-light method can be reconciled; (2) the equi-partition of CME kinetic and thermal flare energy; (3) the Rosner-Tucker-Vaiana scaling law. We find that the two methods in EUV and white-light wavelengths are highly complementary and yield more complete models than each method alone.

Tophi and frequent gout flares are associated with impairments to quality of life, productivity, and increased healthcare resource use: Results from a cross-sectional survey

PubMed Central

2012-01-01

Background The prevalence of gout is increasing, and most research on the associated burden has focused on serum urate (sUA) levels. The present study quantifies the impact of the presence of tophi and frequency of acute gout attacks on health-related quality of life (HRQOL), productivity, and healthcare resource utilization. Methods Patients with self-reported gout (n = 620; 338 in US and 282 across France, Germany, and UK) were contacted based on inclusion in the 2010 US and EU National Health and Wellness Surveys (Kantar Health) and the Lightspeed Research ailment panel. Respondents were categorized into mutually-exclusive groups based on number of gout flares experienced in the past 12 months (0/don’t recall, 1–2, 3, 4–5, 6+), current presence of tophi (none, 1+, or not sure), and sUA level awareness (yes, no). HRQOL (SF-12v2), healthcare provider visits in the last 6 months, and work productivity and activity impairment (WPAI) were compared across groups. Results Most patients were males, mean age of 61 years, who reported experiencing at least one acute gout flare in the past 12 months, and 12.3% (n = 76) reported presence of tophi. Among the 27.7% (n = 172) of patients who were aware of their sUA levels, higher sUA was associated with more flares and tophi. Decreased HRQOL was associated with more frequent flares and presence of tophi. In multivariable models predicting outcomes based on presence of tophi and number of flares, both flares (≥4) and tophi (≥1) were associated with HRQOL decrements on physical and mental component summary scores and health utilities (all p < 0.05), after adjustment for age, gender, and time since diagnosis. Flares were also associated with greater activity impairment. Conclusions Impairments associated with gout flares and presence of tophi, across patients in the US and EU, underscore the importance of effective management of this potentially curable condition. PMID:22999027

Modeling 13.3nm Fe XXIII Flare Emissions Using the GOES-R EXIS Instrument

NASA Astrophysics Data System (ADS)

Rook, H.; Thiemann, E.

2017-12-01

The solar EUV spectrum is dominated by atomic transitions in ionized atoms in the solar atmosphere. As solar flares evolve, plasma temperatures and densities change, influencing abundances of various ions, changing intensities of different EUV wavelengths observed from the sun. Quantifying solar flare spectral irradiance is important for constraining models of Earth's atmosphere, improving communications quality, and controlling satellite navigation. However, high time cadence measurements of flare irradiance across the entire EUV spectrum were not available prior to the launch of SDO. The EVE MEGS-A instrument aboard SDO collected 0.1nm EUV spectrum data from 2010 until 2014, when the instrument failed. No current or future instrument is capable of similar high resolution and time cadence EUV observation. This necessitates a full EUV spectrum model to study EUV phenomena at Earth. It has been recently demonstrated that one hot flare EUV line, such as the 13.3nm Fe XXIII line, can be used to model cooler flare EUV line emissions, filling the role of MEGS-A. Since unblended measurements of Fe XXIII are typically unavailable, a proxy for the Fe XXIII line must be found. In this study, we construct two models of this line, first using the GOES 0.1-0.8nm soft x-ray (SXR) channel as the Fe XXIII proxy, and second using a physics-based model dependent on GOES emission measure and temperature data. We determine that the more sophisticated physics-based model shows better agreement with Fe XXIII measurements, although the simple proxy model also performs well. We also conclude that the high correlation between Fe XXIII emissions and the GOES 0.1-0.8nm band is because both emissions tend to peak near the GOES emission measure peak despite large differences in their contribution functions.

Generation Mechanisms of Quasi-parallel and Quasi-circular Flare Ribbons in a Confined Flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernandez-Perez, Aaron; Thalmann, Julia K.; Veronig, Astrid M.

We analyze a confined multiple-ribbon M2.1 flare (SOL2015-01-29T11:42) that originated from a fan-spine coronal magnetic field configuration, within active region NOAA 12268. The observed ribbons form in two steps. First, two primary ribbons form at the main flare site, followed by the formation of secondary ribbons at remote locations. We observe a number of plasma flows at extreme-ultraviolet temperatures during the early phase of the flare (as early as 15 minutes before the onset) propagating toward the formation site of the secondary ribbons. The secondary ribbon formation is co-temporal with the arrival of the pre-flare generated plasma flows. The primarymore » ribbons are co-spatial with Ramaty High Energy Spectroscopic Imager ( RHESSI ) hard X-ray sources, whereas no enhanced X-ray emission is detected at the secondary ribbon sites. The (E)UV emission, associated with the secondary ribbons, peaks ∼1 minute after the last RHESSI hard X-ray enhancement. A nonlinear force-free model of the coronal magnetic field reveals that the secondary flare ribbons are not directly connected to the primary ribbons, but to regions nearby. Detailed analysis suggests that the secondary brightenings are produced due to dissipation of kinetic energy of the plasma flows (heating due to compression), and not due to non-thermal particles accelerated by magnetic reconnection, as is the case for the primary ribbons.« less

Gamma-Ray "Raindrops" from Flaring Blazar

NASA Image and Video Library

2017-12-08

This visualization shows gamma rays detected during 3C 279's big flare by the LAT instrument on NASA's Fermi satellite. Gamma rays are represented as expanding circles reminiscent of raindrops on water. The flare is an abrupt shower of "rain" that trails off toward the end of the movie. Both the maximum size of the circle and its color represent the energy of the gamma ray, with white lowest and magenta highest. In a second version of the visualization, a background map shows how the LAT detects 3C 279 and other sources by accumulating high-energy photons over time (brighter squares reflect higher numbers of gamma rays). The movie starts on June 14 and ends June 17. The area shown is a region of the sky five degrees on a side and centered on the position of 3C 279. Read more: go.nasa.gov/1TqximF Credits: NASA/DOE/Fermi LAT Collaboration

Could Flaring Stars Change Our Views of Their Planets?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

As the exoplanet count continues to increase, we are making progressively more measurements of exoplanets outer atmospheres through spectroscopy. A new study, however, reveals that these measurements may be influenced by the planets hosts.Spectra From TransitsExoplanet spectra taken as they transit their hosts can tell us about the chemical compositions of their atmospheres. Detailed spectroscopic measurements of planet atmospheres should become even more common with the next generation of missions, such as the James Webb Space Telescope (JWST), or Planetary Transits and Oscillations of Stars (PLATO).But is the spectrum that we measure in the brief moment of a planets transit necessarily representative of its spectrum all of the time? A team of scientists led by Olivia Venot (University of Leuven in Belgium) argue that it might not be, due to the influence of the planets stellar host.Atmospheric composition of a planet before flare impacts (dotted lines), during the steady state reached after a flare impact (dashed lines), and during the steady state reached after a second flare impact (solid lines). [Venot et al. 2016]The team suggests that when a hosts flares impact upon a planets atmosphere (especially likely in the case of active M-dwarfs that commonly harbor planetary systems), this activity may modify the chemical composition of the planets atmosphere. This would in turn alter the spectrum that we measure from the exoplanet.Modeling AtmospheresVenot and collaborators set out to test the effect of stellar flares on exoplanet atmospheres by modeling the atmospheres of two hypothetical planets orbiting the star AD Leo an active and flaring M dwarf located roughly 16 light-years away at two different distances. The team then examined what happened to the atmospheres, and to the resulting spectra that we would observe, when they were hit with a stellar flare typical of AD Leo.The difference in relative absorption between the initial steady-state and the instantaneous transmission spectra, obtained during the different phases of the flare. The left plot examines the impulsive and gradual phases, when the flare first impacts and then starts to pass. The peak photon flux occurs at 912 seconds. The right plot examines the return to a steady state over 1012 seconds, or roughly 30,000 years. [Adapted from Venot et al. 2016]The authors found that the planets atmospheric compositions were significantly affected by the incoming stellar flare. The sudden increase in incoming photon flux changed the chemical abundances of several important molecular species, like hydrogen and ammonia which resulted in changes to the spectrum that would be observed during the planets transit.Permanent ImpactIn addition to demonstrating that a planets atmospheric composition changes during and immediately after a flare impact, Venot and collaborators show that the chemical alteration isnt temporary: the planets atmosphere doesnt fully return to its original state after the flare passes. Instead, the authors find that it settles to a new steady-state composition that can be significantly different from the pre-flare composition.For a planet that is repeatedly hit by stellar flares, therefore, its atmospheric composition never actually settles to a steady state. Instead it is continually and permanently modified by its hosts activity.Venot and collaborators demonstrate that the variations of planetary spectra due to stellar flares should be easily detectable by future missions like JWST. We must therefore be careful about the conclusions we draw about planetary atmospheres from measurements of their spectra.CitationOlivia Venot et al 2016 ApJ 830 77. doi:10.3847/0004-637X/830/2/77

Flare Seismology from SDO Observations

NASA Astrophysics Data System (ADS)

Lindsey, Charles; Martinez Oliveros, Juan Carlos; Hudson, Hugh

2011-10-01

Some flares release intense seismic transients into the solar interior. These transients are the sole instance we know of in which the Sun's corona exerts a conspicuous influence on the solar interior through flares. The desire to understand this phenomenon has led to ambitious efforts to model the mechanisms by which energy stored in coronal magnetic fields drives acoustic waves that penetrate deep into the Sun's interior. These mechanisms potentially involve the hydrodynamic response of the chromosphere to thick-target heating by high-energy particles, radiative exchange in the chromosphere and photosphere, and Lorentz-force transients to account for acoustic energies estimated up to at 5X10^27 erg and momenta of order 6X10^19 dyne sec. An understanding of these components of flare mechanics promises more than a powerful diagnostic for local helioseismology. It could give us fundamental new insight into flare mechanics themselves. The key is appropriate observations to match the models. Helioseismic observations have identified the compact sources of transient seismic emission at the foot points of flares. The Solar Dynamics Observatory is now giving us high quality continuum-brightness and Doppler observations of acoustically active flares from HMI concurrent with high-resolution EUV observations from AIA. Supported by HXR observations from RHESSI and a broad variety of other observational resources, the SDO promises a leading role in flare research in solar cycle 24.

Solar active region display system

NASA Astrophysics Data System (ADS)

Golightly, M.; Raben, V.; Weyland, M.

2003-04-01

The Solar Active Region Display System (SARDS) is a client-server application that automatically collects a wide range of solar data and displays it in a format easy for users to assimilate and interpret. Users can rapidly identify active regions of interest or concern from color-coded indicators that visually summarize each region's size, magnetic configuration, recent growth history, and recent flare and CME production. The active region information can be overlaid onto solar maps, multiple solar images, and solar difference images in orthographic, Mercator or cylindrical equidistant projections. Near real-time graphs display the GOES soft and hard x-ray flux, flare events, and daily F10.7 value as a function of time; color-coded indicators show current trends in soft x-ray flux, flare temperature, daily F10.7 flux, and x-ray flare occurrence. Through a separate window up to 4 real-time or static graphs can simultaneously display values of KP, AP, daily F10.7 flux, GOES soft and hard x-ray flux, GOES >10 and >100 MeV proton flux, and Thule neutron monitor count rate. Climatologic displays use color-valued cells to show F10.7 and AP values as a function of Carrington/Bartel's rotation sequences - this format allows users to detect recurrent patterns in solar and geomagnetic activity as well as variations in activity levels over multiple solar cycles. Users can customize many of the display and graph features; all displays can be printed or copied to the system's clipboard for "pasting" into other applications. The system obtains and stores space weather data and images from sources such as the NOAA Space Environment Center, NOAA National Geophysical Data Center, the joint ESA/NASA SOHO spacecraft, and the Kitt Peak National Solar Observatory, and can be extended to include other data series and image sources. Data and images retrieved from the system's database are converted to XML and transported from a central server using HTTP and SOAP protocols, allowing operation through network firewalls; data is compressed to enhance performance over limited bandwidth connections. All applications and services are written in the JAVA program language for platform independence. Several versions of SARDS have been in operational use by the NASA Space Radiation Analysis Group, NOAA Space Weather Operations, and U.S. Air Force Weather Agency since 1999.

Xrt And Shinx Joint Flare Study: Ar 11024

NASA Astrophysics Data System (ADS)

Engell, Alexander; Sylwester, J.; Siarkowski, M.

2010-05-01

From 12:00 UT on July 3 through July 7, 2009 SphinX (Solar Photometer IN X-rays) observes 130 flares with active region (AR) 11024 being the only AR on disk. XRT (X-Ray Telescope) is able to observe 64 of these flare events. The combination of both instruments results in a flare study revealing (1) a relationship between flux emergence and flare rate, (2) that the presence of active region loops typically results in different flare morphologies (single and multiple loop flares) then when there is a lack of an active region loop environment where more cusp and point-like flares are observed, (3) cusp and point-like flares often originate from the same location, and (4) a distribution of flare temperatures corresponding to the different flare morphologies. The differences between the observed flare morphologies may occur as the result of the heated plasma through the flaring process being confined by the proximity of loop structures as for the single and multiple loop flares, while for cusp and point-like flares they occur in an early-phase environment that lack loop presence. The continuing flux emergence of AR 11024 likely provides different magnetic interactions and may be the source responsible for all of the flares.

Canakinumab reduces the risk of acute gouty arthritis flares during initiation of allopurinol treatment: results of a double-blind, randomised study

PubMed Central

Schlesinger, Naomi; Mysler, Eduardo; Lin, Hsiao-Yi; De Meulemeester, Marc; Rovensky, Jozef; Arulmani, Udayasankar; Balfour, Alison; Krammer, Gerhard; Sallstig, Peter; So, Alexander

2011-01-01

Objective This study assessed the efficacy and safety of canakinumab, a fully human anti-interleukin 1β monoclonal antibody, for prophylaxis against acute gouty arthritis flares in patients initiating urate-lowering treatment. Methods In this double-blind, double-dummy, dose-ranging study, 432 patients with gouty arthritis initiating allopurinol treatment were randomised 1:1:1:1:1:1:2 to receive: a single dose of canakinumab, 25, 50, 100, 200, or 300 mg subcutaneously; 4×4-weekly doses of canakinumab (50+50+25+25 mg subcutaneously); or daily colchicine 0.5 mg orally for 16 weeks. Patients recorded details of flares in diaries. The study aimed to determine the canakinumab dose having equivalent efficacy to colchicine 0.5 mg at 16 weeks. Results A dose-response for canakinumab was not apparent with any of the four predefined dose-response models. The estimated canakinumab dose with equivalent efficacy to colchicine was below the range of doses tested. At 16 weeks, there was a 62% to 72% reduction in the mean number of flares per patient for canakinumab doses ≥50 mg versus colchicine based on a negative binomial model (rate ratio: 0.28–0.38, p≤0.0083), and the percentage of patients experiencing ≥1 flare was significantly lower for all canakinumab doses (15% to 27%) versus colchicine (44%, p<0.05). There was a 64% to 72% reduction in the risk of experiencing ≥1 flare for canakinumab doses ≥50 mg versus colchicine at 16 weeks (hazard ratio (HR): 0.28–0.36, p≤0.05). The incidence of adverse events was similar across treatment groups. Conclusions Single canakinumab doses ≥50 mg or four 4-weekly doses provided superior prophylaxis against flares compared with daily colchicine 0.5 mg. PMID:21540198

Statistical aspects of solar flares

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

1987-01-01

A survey of the statistical properties of 850 H alpha solar flares during 1975 is presented. Comparison of the results found here with those reported elsewhere for different epochs is accomplished. Distributions of rise time, decay time, and duration are given, as are the mean, mode, median, and 90th percentile values. Proportions by selected groupings are also determined. For flares in general, mean values for rise time, decay time, and duration are 5.2 + or - 0.4 min, and 18.1 + or 1.1 min, respectively. Subflares, accounting for nearly 90 percent of the flares, had mean values lower than those found for flares of H alpha importance greater than 1, and the differences are statistically significant. Likewise, flares of bright and normal relative brightness have mean values of decay time and duration that are significantly longer than those computed for faint flares, and mass-motion related flares are significantly longer than non-mass-motion related flares. Seventy-three percent of the mass-motion related flares are categorized as being a two-ribbon flare and/or being accompanied by a high-speed dark filament. Slow rise time flares (rise time greater than 5 min) have a mean value for duration that is significantly longer than that computed for fast rise time flares, and long-lived duration flares (duration greater than 18 min) have a mean value for rise time that is significantly longer than that computed for short-lived duration flares, suggesting a positive linear relationship between rise time and duration for flares. Monthly occurrence rates for flares in general and by group are found to be linearly related in a positive sense to monthly sunspot number. Statistical testing reveals the association between sunspot number and numbers of flares to be significant at the 95 percent level of confidence, and the t statistic for slope is significant at greater than 99 percent level of confidence. Dependent upon the specific fit, between 58 percent and 94 percent of the variation can be accounted for with the linear fits. A statistically significant Northern Hemisphere flare excess (P less than 1 percent) was found, as was a Western Hemisphere excess (P approx 3 percent). Subflares were more prolific within 45 deg of central meridian (P less than 1 percent), while flares of H alpha importance or = 1 were more prolific near the limbs greater than 45 deg from central meridian; P approx 2 percent). Two-ribbon flares were more frequent within 45 deg of central meridian (P less than 1 percent). Slow rise time flares occurred more frequently in the western hemisphere (P approx 2 percent), as did short-lived duration flares (P approx 9 percent), but fast rise time flares were not preferentially distributed (in terms of east-west or limb-disk). Long-lived duration flares occurred more often within 45 deg 0 central meridian (P approx 7 percent). Mean durations for subflares and flares of H alpha importance or + 1, found within 45 deg of central meridian, are 14 percent and 70 percent, respectively, longer than those found for flares closer to the limb. As compared to flares occurring near cycle maximum, the flares of 1975 (near solar minimum) have mean values of rise time, decay time, and duration that are significantly shorter. A flare near solar maximum, on average, is about 1.6 times longer than one occurring near solar minimum.

The potential near-source ozone impacts of upstream oil and gas industry emissions.

PubMed

Olaguer, Eduardo P

2012-08-01

Increased drilling in urban areas overlying shale formations and its potential impact on human health through decreased air quality make it important to estimate the contribution of oil and gas activities to photochemical smog. Flares and compressor engines used in natural gas operations, for example, are large sources not only of NOx but also offormaldehyde, a hazardous air pollutant and powerful ozone precursor We used a neighborhood scale (200 m horizontal resolution) three-dimensional (3D) air dispersion model with an appropriate chemical mechanism to simulate ozone formation in the vicinity ofa hypothetical natural gas processing facility, based on accepted estimates of both regular and nonroutine emissions. The model predicts that, under average midday conditions in June, regular emissions mostly associated with compressor engines may increase ambient ozone in the Barnett Shale by more than 3 ppb beginning at about 2 km downwind of the facility, assuming there are no other major sources of ozone precursors. Flare volumes of 100,000 cubic meters per hour ofnatural gas over a period of 2 hr can also add over 3 ppb to peak 1-hr ozone somewhatfurther (>8 km) downwind, once dilution overcomes ozone titration and inhibition by large flare emissions of NOx. The additional peak ozone from the hypothetical flare can briefly exceed 10 ppb about 16 km downwind. The enhancements of ambient ozone predicted by the model are significant, given that ozone control strategy widths are of the order of a few parts per billion. Degrading the horizontal resolution of the model to 1 km spuriously enhances the simulated ozone increases by reducing the effectiveness of ozone inhibition and titration due to artificial plume dilution.

Harnessing AIA Diffraction Patterns to Determine Flare Footpoint Temperatures

NASA Astrophysics Data System (ADS)

Bain, H. M.; Schwartz, R. A.; Torre, G.; Krucker, S.; Raftery, C. L.

2014-12-01

In the "Standard Flare Model" energy from accelerated electrons is deposited at the footpoints of newly reconnected flare loops, heating the surrounding plasma. Understanding the relation between the multi-thermal nature of the footpoints and the energy flux from accelerated electrons is therefore fundamental to flare physics. Extreme ultraviolet (EUV) images of bright flare kernels, obtained from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory, are often saturated despite the implementation of automatic exposure control. These kernels produce diffraction patterns often seen in AIA images during the most energetic flares. We implement an automated image reconstruction procedure, which utilizes diffraction pattern artifacts, to de-saturate AIA images and reconstruct the flare brightness in saturated pixels. Applying this technique to recover the footpoint brightness in each of the AIA EUV passbands, we investigate the footpoint temperature distribution. Using observations from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we will characterize the footpoint accelerated electron distribution of the flare. By combining these techniques, we investigate the relation between the nonthermal electron energy flux and the temperature response of the flare footpoints.

Solar-geophysical data number 496, December 1985. Part 2: (Comprehensive reports). Data for June 1985, January-May 1985 and miscellanea

NASA Technical Reports Server (NTRS)

Coffey, H. E. (Editor)

1985-01-01

Contents include the detailed index for 1985; data for June 1985 (solar flares, solar radio bursts at fixed frequencies, solar X-ray radiation from GOES satellite graphs, mass ejections from the sun, and active prominences and filaments); data for January to May 1985 (solar flares January 1985, solar flares February 1985, solar flares March 1985, solar flares April 1985, solar flares May 1985, and number of flares August 1966 to June 1985); and the international geophysical calendar 1986.

Sun Emits an X2.2 Flare

NASA Image and Video Library

2015-03-11

The sun emitted a significant solar flare, peaking at 12:22 p.m. EDT on March 11, 2015. NASA’s Solar Dynamics Observatory, which watches the sun constantly, captured an image of the event. Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground, however -- when intense enough -- they can disturb the atmosphere in the layer where GPS and communications signals travel. This flare is classified as an X2.2-class flare. X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, etc. Credit: NASA/Goddard/SDO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

The Effect of a Strong Stellar Flare on the Atmospheric Chemistry of an Earth-like Planet Orbiting an M Dwarf

PubMed Central

Walkowicz, Lucianne M.; Meadows, Victoria; Kasting, James; Hawley, Suzanne

2010-01-01

Abstract Main sequence M stars pose an interesting problem for astrobiology: their abundance in our galaxy makes them likely targets in the hunt for habitable planets, but their strong chromospheric activity produces high-energy radiation and charged particles that may be detrimental to life. We studied the impact of the 1985 April 12 flare from the M dwarf AD Leonis (AD Leo), simulating the effects from both UV radiation and protons on the atmospheric chemistry of a hypothetical, Earth-like planet located within its habitable zone. Based on observations of solar proton events and the Neupert effect, we estimated a proton flux associated with the flare of 5.9 × 108 protons cm−2 sr−1 s−1 for particles with energies >10 MeV. Then we calculated the abundance of nitrogen oxides produced by the flare by scaling the production of these compounds during a large solar proton event called the Carrington event. The simulations were performed with a 1-D photochemical model coupled to a 1-D radiative/convective model. Our results indicate that the UV radiation emitted during the flare does not produce a significant change in the ozone column depth of the planet. When the action of protons is included, the ozone depletion reaches a maximum of 94% two years after the flare for a planet with no magnetic field. At the peak of the flare, the calculated UV fluxes that reach the surface, in the wavelength ranges that are damaging for life, exceed those received on Earth during less than 100 s. Therefore, flares may not present a direct hazard for life on the surface of an orbiting habitable planet. Given that AD Leo is one of the most magnetically active M dwarfs known, this conclusion should apply to planets around other M dwarfs with lower levels of chromospheric activity. Key Words: M dwarf—Flare—Habitable zone—Planetary atmospheres. Astrobiology 10, 751–771. PMID:20879863

Unprecedented Fine Structure of a Solar Flare Revealed by the 1.6 m New Solar Telescope

PubMed Central

Jing, Ju; Xu, Yan; Cao, Wenda; Liu, Chang; Gary, Dale; Wang, Haimin

2016-01-01

Solar flares signify the sudden release of magnetic energy and are sources of so called space weather. The fine structures (below 500 km) of flares are rarely observed and are accessible to only a few instruments world-wide. Here we present observation of a solar flare using exceptionally high resolution images from the 1.6 m New Solar Telescope (NST) equipped with high order adaptive optics at Big Bear Solar Observatory (BBSO). The observation reveals the process of the flare in unprecedented detail, including the flare ribbon propagating across the sunspots, coronal rain (made of condensing plasma) streaming down along the post-flare loops, and the chromosphere’s response to the impact of coronal rain, showing fine-scale brightenings at the footpoints of the falling plasma. Taking advantage of the resolving power of the NST, we measure the cross-sectional widths of flare ribbons, post-flare loops and footpoint brighenings, which generally lie in the range of 80–200 km, well below the resolution of most current instruments used for flare studies. Confining the scale of such fine structure provides an essential piece of information in modeling the energy transport mechanism of flares, which is an important issue in solar and plasma physics. PMID:27071459

Study of solar flare induced D-region ionosphere changes using VLF amplitude observations at a low latitude site

NASA Astrophysics Data System (ADS)

Tan, L. M.; Thu, N. N.; Ha, T. Q.; Marbouti, M.

2014-06-01

About 26 solar flare events from C2.56 to X3.2 classes were obtained and analyzed at Tay Nguyen University, Vietnam (12.56°N, 108.02°E) during May - December 2013 using very low frequency remote sensing to understand the responses of low latitude D-region ionosphere during solar flares. The observed VLF amplitude perturbations are used as the input parameters for the simulated Long Wavelength Propagation Capability (LWPC) program, using Wait's model of lower ionosphere, to calculate two Wait's parameters, viz. the reflection height (H') and the sharpness factor (?). The results reveal that when X-ray irradiance is increased, ? increased from 0.3 to 0.506 km-1, while H' decreased from 74 to 60 km. The electron density increased at the height of 74 km with 1-3 orders of magnitude during solar flares. These phenomena can be explained as: the ionization due to X-ray irradiance becomes greater than that due to cosmic rays and Lyman-α radiation, which increases the electron density profile. The present results are in agreement with the earlier results. The 3D representation of the electron density changes with altitude and time supports to fully understand the shape of the electron density changes due to X-ray flares. The shape variation of electron density is roughly followed to the variation of the amplitude perturbation and keeps this rule for different altitudes. It is also found that the electron density versus the height in lower latitude D-region ionosphere increases more rapidly during solar flares.

Pharmacokinetic-pharmacodynamic modelling of the antihistaminic (H1) effect of bilastine.

PubMed

Jauregizar, Nerea; de la Fuente, Leire; Lucero, Maria Luisa; Sologuren, Ander; Leal, Nerea; Rodríguez, Mónica

2009-01-01

To model the pharmacokinetic and pharmacodynamic relationship of bilastine, a new histamine H(1) receptor antagonist, from single- and multiple-dose studies in healthy adult subjects. The pharmacokinetic model was developed from different single-dose and multiple-dose studies. In the single-dose studies, a total of 183 subjects received oral doses of bilastine 2.5, 5, 10, 20, 50, 100, 120, 160, 200 and 220 mg. In the multiple-dose studies, 127 healthy subjects received bilastine 10, 20, 40, 50, 80, 100, 140 or 200 mg/day as multiple doses during a 4-, 7- or 14-day period. The pharmacokinetic profile of bilastine was investigated using a simultaneous analysis of all concentration-time data by means of nonlinear mixed-effects modelling population pharmacokinetic software NONMEM version 6.1. Plasma concentrations were modelled according to a two-compartment open model with first-order absorption and elimination. For the pharmacodynamic analysis, the inhibitory effect of bilastine (inhibition of histamine-induced wheal and flare) was assessed on a preselected time schedule, and the predicted typical pharmacokinetic profile (based on the pharmacokinetic model previously developed) was used. An indirect response model was developed to describe the pharmacodynamic relationships between flare or wheal areas and bilastine plasma concentrations. Finally, once values of the concentration that produced 50% inhibition (IC(50)) had been estimated for wheal and flare effects, simulations were carried out to predict plasma concentrations for the doses of bilastine 5, 10 and 20 mg at steady state (72-96 hours). A non-compartmental analysis resulted in linear kinetics of bilastine in the dose range studied. Bilastine was characterized by two-compartmental kinetics with a rapid-absorption phase (first-order absorption rate constant = 1.50 h(-1)), plasma peak concentrations were observed at 1 hour following administration and the maximal response was observed at approximately 4 hours or later. Concerning the selected pharmacodynamic model to fit the data (type I indirect response model), this selection is attributable to the presence of inhibitory bilastine plasma concentrations that decrease the input response function, i.e. the production of the skin reaction. This model resulted in the best fit of wheal and flare data. The estimates (with relative standard errors expressed in percentages in parentheses) of the apparent zero-order rate constant for flare or wheal spontaneous appearance (k(in)), the first-order rate constant for flare or wheal disappearance (k(out)) and bilastine IC(50) values were 0.44 ng/mL/h (14.60%), 1.09 h(-1) (15.14%) and 5.15 ng/mL (16.16%), respectively, for wheal inhibition, and 11.10 ng/mL/h (8.48%), 1.03 h(-1) (8.35%) and 1.25 ng/mL (14.56%), respectively, for flare inhibition. The simulation results revealed that bilastine plasma concentrations do not remain over the IC(50) value throughout the inter-dose period for doses of 5 and 10 mg. However, with a dose of 20 mg of bilastine administered every 24 hours, plasma concentrations remained over the IC(50) value during the considered period for the flare effect, and up to 20 hours for the wheal effect. Pharmacokinetic and pharmacodynamic relationships of bilastine were reliably described with the use of an indirect response pharmacodynamic model; this led to an accurate prediction of the pharmacodynamic activity of bilastine.

Hooked Flare Ribbons and Flux-rope-related QSL Footprints

NASA Astrophysics Data System (ADS)

Zhao, Jie; Gilchrist, Stuart A.; Aulanier, Guillaume; Schmieder, Brigitte; Pariat, Etienne; Li, Hui

2016-05-01

We studied the magnetic topology of active region 12158 on 2014 September 10 and compared it with the observations before and early in the flare that begins at 17:21 UT (SOL2014-09-10T17:45:00). Our results show that the sigmoidal structure and flare ribbons of this active region observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly can be well reproduced from a Grad-Rubin nonlinear force-free field extrapolation method. Various inverse-S- and inverse-J-shaped magnetic field lines, which surround a coronal flux rope, coincide with the sigmoid as observed in different extreme-ultraviolet wavelengths, including its multithreaded curved ends. Also, the observed distribution of surface currents in the magnetic polarity where it was not prescribed is well reproduced. This validates our numerical implementation and setup of the Grad-Rubin method. The modeled double inverse-J-shaped quasi-separatrix layer (QSL) footprints match the observed flare ribbons during the rising phase of the flare, including their hooked parts. The spiral-like shape of the latter may be related to a complex pre-eruptive flux rope with more than one turn of twist, as obtained in the model. These ribbon-associated flux-rope QSL footprints are consistent with the new standard flare model in 3D, with the presence of a hyperbolic flux tube located below an inverse-teardrop-shaped coronal QSL. This is a new step forward forecasting the locations of reconnection and ribbons in solar flares and the geometrical properties of eruptive flux ropes.

Catching the radio flare in CTA 102. I. Light curve analysis

NASA Astrophysics Data System (ADS)

Fromm, C. M.; Perucho, M.; Ros, E.; Savolainen, T.; Lobanov, A. P.; Zensus, J. A.; Aller, M. F.; Aller, H. D.; Gurwell, M. A.; Lähteenmäki, A.

2011-07-01

Context. The blazar CTA 102 (z = 1.037) underwent a historical radio outburst in April 2006. This event offered a unique chance to study the physical properties of the jet. Aims: We used multifrequency radio and mm observations to analyze the evolution of the spectral parameters during the flare as a test of the shock-in-jet model under these extreme conditions. Methods: For the analysis of the flare we took into account that the flaring spectrum is superimposed on a quiescent spectrum. We reconstructed the latter from archival data and fitted a synchrotron self-absorbed distribution of emission. The uncertainties of the derived spectral parameters were calculated using Monte Carlo simulations. The spectral evolution is modeled by the shock-in-jet model, and the derived results are discussed in the context of a geometrical model (varying viewing angle) and shock-shock interaction Results: The evolution of the flare in the turnover frequency-turnover flux density (νm - Sm) plane shows a double peak structure. The nature of this evolution is dicussed in the frame of shock-in-jet models. We discard the generation of the double peak structure in the νm - Sm plane purely based on geometrical changes (variation of the Doppler factor). The detailed modeling of the spectral evolution favors a shock-shock interaction as a possible physical mechanism behind the deviations from the standard shock-in-jet model.

Ionic charge distributions of energetic particles from solar flares

NASA Technical Reports Server (NTRS)

Mullan, D. J.; Waldron, W. L.

1986-01-01

The effects which solar flare X-rays have on the charge states of solar cosmic rays is determined quantitatively. Rather than to characterize the charge distribution by temperature alone, it is proposed that the X-ray flux at the acceleration site also is used. The effects of flare X-rays are modeled mathematically.

Modeling properties of chromospheric evaporation driven by thermal conduction fronts from reconnection shocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brannon, Sean; Longcope, Dana

2014-09-01

Magnetic reconnection in the corona results in contracting flare loops, releasing energy into plasma heating and shocks. The hydrodynamic shocks produced in this manner drive thermal conduction fronts (TCFs) which transport energy into the chromosphere and drive upflows (evaporation) and downflows (condensation) in the cooler, denser footpoint plasma. Observations have revealed that certain properties of the transition point between evaporation and condensation (the 'flow reversal point' or FRP), such as temperature and velocity-temperature derivative at the FRP, vary between different flares. These properties may provide a diagnostic tool to determine parameters of the coronal energy release mechanism and the loopmore » atmosphere. In this study, we develop a one-dimensional hydrodynamical flare loop model with a simplified three-region atmosphere (chromosphere/transition region/corona), with TCFs initiated by shocks introduced in the corona. We investigate the effect of two different flare loop parameters (post-shock temperature and transition region temperature ratio) on the FRP properties. We find that both of the evaporation characteristics have scaling-law relationships to the varied flare parameters, and we report the scaling exponents for our model. This provides a means of using spectroscopic observations of the chromosphere as quantitative diagnostics of flare energy release in the corona.« less

A thermal/nonthermal approach to solar flares

NASA Technical Reports Server (NTRS)

Benka, Stephen G.

1991-01-01

An approach for modeling solar flare high-energy emissions is developed in which both thermal and nonthermal particles coexist and contribute to the radiation. The thermal/nonthermal distribution function is interpreted physically by postulating the existence of DC sheets in the flare region. The currents then provide both primary plasma heating through Joule dissipation, and runaway electron acceleration. The physics of runaway acceleration is discussed. Several methods are presented for obtaining approximations to the thermal/nonthermal distribution function, both within the current sheets and outside of them. Theoretical hard x ray spectra are calculated, allowing for thermal bremsstrahlung from the heated plasma electrons impinging on the chromosphere. A simple model for hard x ray images of two-ribbon flares is presented. Theoretical microwave gyrosynchrotron spectra are calculated and analyzed, uncovering important new effects caused by the interplay of thermal and nonthermal particles. The theoretical spectra are compared with observed high resolution spectra of solar flares, and excellent agreement is found, in both hard x rays and microwaves. The future detailed application of this approach to solar flares is discussed, as are possible refinements to this theory.

Modeling of very low frequency (VLF) radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry

NASA Astrophysics Data System (ADS)

Palit, S.; Basak, T.; Mondal, S. K.; Pal, S.; Chakrabarti, S. K.

2013-09-01

X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~60 to 100 km) in excess of what is expected to occur due to a quiet sun. Very low frequency (VLF) radio wave signals reflected from the D-region of the ionosphere are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class flare and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the D-region of the ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the change in VLF signal. We did the modeling of the VLF signal along the NWC (Australia) to IERC/ICSP (India) propagation path and compared the results with observations. The agreement is found to be very satisfactory.

Modeling VLF signal modulation during solar flares with GEANT4 Monte Carlo simulation, a simple chemical model and LWPC

NASA Astrophysics Data System (ADS)

Palit, Sourav; Chakrabarti, Sandip Kumar; Pal, Sujay; Basak, Tamal

Extra ionization by X-rays during solar flares affects VLF signal propagation through D-region ionosphere. Ionization produced in the lower ionosphere due to X-ray spectra of solar flares are simulated with an efficient detector simulation program, GEANT4. The balancing between the ionization and loss processes, causing the lower ionosphere to settle back to its undisturbed state is handled with a simple chemical model consisting of four broad species of ion densities. Using the electron densities, modified VLF signal amplitude is then computed with LWPC code. VLF signal along NWC (Australia) to IERC/ICSP (India) propagation path is examined during a M and a X-type solar flares and observational deviations are compared with simulated results. The agreement is found to be excellent.

Magnetic Field Configuration of Active Region NOAA 6555 at the Time of a Long Duration Flare on 23 March 1991: An Exception to Standard Flare Reconnection Model

NASA Technical Reports Server (NTRS)

Choudhary, Debi Prasad; Gary, Allen G.

1998-01-01

The high-resolution H(sub alpha) images observed during the decay phase of a long duration flare on 23 March 1991 are used to study the three-dimensional magnetic field configuration of the active region NOAA 6555. Whereas, all the large flares in NOAA 6555 occurred at the location of high magnetic shear and flux emergence, this long duration flare was observed in the region of low magnetic shear at the photosphere. The H(sub alpha) loop activity started soon after the maximum phase of the flare. There were few long loop at the initial phase of the activity. Some of these were sheared in the chromosphere at an angle of about 45 deg with the east-west axis. Gradually, increasing number of shorter loops, oriented along the east-west axis, started appearing. The chromospheric Dopplergrams show blue-shifts at the end points of the loops. By using different magnetic field models, we have extrapolated the photospheric magnetograms to the chromospheric heights. The magnetic field lines computed by using the potential field model correspond to most of the observed H(sub alpha) loops. The height of the H(sub alpha) loops were derived by comparing them with the computed field lines. From the temporal evolution of the H(sub alpha) loop activity, we derive the negative rate of appearance of H(sub alpha) features as a function of height. It is found that the field lines oriented along one of the neutral lines was sheared and low lying. The higher field lines were mostly potential. The paper also outlines a possible scenario for describing the post-flare stage of the observed long duration flare.

Why models struggle to capture Arctic Haze: the underestimated role of gas flaring and domestic combustion emissions

NASA Astrophysics Data System (ADS)

Stohl, A.; Klimont, Z.; Eckhardt, S.; Kupiainen, K.

2013-04-01

Arctic Haze is a seasonal phenomenon with high concentrations of accumulation-mode aerosols occurring in the Arctic in winter and early spring. Chemistry transport models and climate chemistry models struggle to reproduce this phenomenon, and this has recently prompted changes in aerosol removal schemes to remedy the modeling problems. In this paper, we show that shortcomings in current emission data sets are at least as important. We perform a 3 yr model simulation of black carbon (BC) with the Lagrangian particle dispersion model FLEXPART. The model is driven with a new emission data set which includes emissions from gas flaring. While gas flaring is estimated to contribute less than 3% of global BC emissions in this data set, flaring dominates the estimated BC emissions in the Arctic (north of 66° N). Putting these emissions into our model, we find that flaring contributes 42% to the annual mean BC surface concentrations in the Arctic. In March, flaring even accounts for 52% of all Arctic BC near the surface. Most of the flaring BC remains close to the surface in the Arctic, so that the flaring contribution to BC in the middle and upper troposphere is small. Another important factor determining simulated BC concentrations is the seasonal variation of BC emissions from domestic combustion. We have calculated daily domestic combustion emissions using the heating degree day (HDD) concept based on ambient air temperature and compare results from model simulations using emissions with daily, monthly and annual time resolution. In January, the Arctic-mean surface concentrations of BC due to domestic combustion emissions are 150% higher when using daily emissions than when using annually constant emissions. While there are concentration reductions in summer, they are smaller than the winter increases, leading to a systematic increase of annual mean Arctic BC surface concentrations due to domestic combustion by 68% when using daily emissions. A large part (93%) of this systematic increase can be captured also when using monthly emissions; the increase is compensated by a decreased BC burden at lower latitudes. In a comparison with BC measurements at six Arctic stations, we find that using daily-varying domestic combustion emissions and introducing gas flaring emissions leads to large improvements of the simulated Arctic BC, both in terms of mean concentration levels and simulated seasonality. Case studies based on BC and carbon monoxide (CO) measurements from the Zeppelin observatory appear to confirm flaring as an important BC source that can produce pollution plumes in the Arctic with a high BC/CO enhancement ratio, as expected for this source type. Our results suggest that it may not be "vertical transport that is too strong or scavenging rates that are too low" and "opposite biases in these processes" in the Arctic and elsewhere in current aerosol models, as suggested in a recent review article (Bond et al., 2013), but missing emission sources and lacking time resolution of the emission data that are causing opposite model biases in simulated BC concentrations in the Arctic and in the mid-latitudes.

Interplanetary propagation of flare-associated energetic particles

NASA Technical Reports Server (NTRS)

Masung, L. L.; Earl, J. A.

1978-01-01

A propagation model which combines a Gaussian profile for particle release from the sun, with interplanetary particle densities predicted by focused diffusion, was proposed to explain the propagation history of flare associated energetic particles. This model, which depends on only two parameters, successfully describes the time-intensity profiles of 30 proton and electron events originating from the western hemisphere of the sun. Generally, particles are released from the sun over a finite interval. In almost all events, particle release begins at the time of flare acceleration.

Plasma upflows and microwave emission in hot supra-arcade structure associated with AN M1.6 limb flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, S.; Shibasaki, K.; Bain, H.-M.

2014-04-20

We have investigated a supra-arcade structure associated with an M1.6 flare, which occurred on the south-east limb on 2010 November 4. It is observed in EUV with the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, microwaves at 17 and 34 GHz with the Nobeyama Radioheliograph (NoRH), and soft X-rays of 8-20 keV with RHESSI. Interestingly, we found exceptional properties of the supra-arcade thermal plasma from the AIA 131 Å and the NoRH: (1) plasma upflows along large coronal loops and (2) enhancing microwave emission. RHESSI detected two soft X-ray sources, a broad one in the middle ofmore » the supra-arcade structure and a bright one just above the flare-arcade. We estimated the number density and thermal energy for these two source regions during the decay phase of the flare. In the supra-arcade source, we found that there were increases of the thermal energy and the density at the early and last stages, respectively. On the contrary, the density and thermal energy of the source on the top of the flare-arcade decreases throughout. The observed upflows imply that there is continuous energy supply into the supra-arcade structure from below during the decay phase of the flare. It is hard to explain by the standard flare model in which the energy release site is located high in the corona. Thus, we suggest that a potential candidate of the energy source for the hot supra-arcade structure is the flare-arcade, which has exhibited a predominant emission throughout.« less

A ``perfect'' Late Phase Flare Loop: X-ray And Radio Studies

NASA Astrophysics Data System (ADS)

Bain, Hazel; Fletcher, L.

2009-05-01

We present observations of a GOES X3.1 class flare which occurred on the 24th August 2002. The event was observed by a number of instruments including RHESSI, TRACE and NoRH. This flare is particularly interesting due to its position and orientation on the west limb of the Sun. The flare appears to be perpendicular to the line of sight making it possible to ascertain the geometrical parameters of the post flare arcade loops. We investigate the decay phase of the flare by comparing X-ray and radio observations of the post flare arcade loops with models of soft x-ray and thermal gyrosynchrotron emission to characterise the electron distribution present within the loop. HMB gratefully acknowledges the support of an SPD and STFC studentship. LF gratefully acknowledges the support of an STFC Rolling Grant, and financial support by the European Commission through the SOLAIRE Network (MTRN-CT_2006-035484)

Testing the Model of Oscillating Magnetic Traps

NASA Astrophysics Data System (ADS)

Szaforz, Ż.; Tomczak, M.

2015-01-01

The aim of this paper is to test the model of oscillating magnetic traps (the OMT model), proposed by Jakimiec and Tomczak ( Solar Phys. 261, 233, 2010). This model describes the process of excitation of quasi-periodic pulsations (QPPs) observed during solar flares. In the OMT model energetic electrons are accelerated within a triangular, cusp-like structure situated between the reconnection point and the top of a flare loop as seen in soft X-rays. We analyzed QPPs in hard X-ray light curves for 23 flares as observed by Yohkoh. Three independent methods were used. We also used hard X-ray images to localize magnetic traps and soft X-ray images to diagnose thermal plasmas inside the traps. We found that the majority of the observed pulsation periods correlates with the diameters of oscillating magnetic traps, as was predicted by the OMT model. We also found that the electron number density of plasma inside the magnetic traps in the time of pulsation disappearance is strongly connected with the pulsation period. We conclude that the observations are consistent with the predictions of the OMT model for the analyzed set of flares.

Exploring the blazar zone in high-energy flares of FSRQs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pacciani, L.; Donnarumma, I.; Tavecchio, F.

2014-07-20

The gamma-ray emission offers a powerful diagnostic tool to probe jets and their surroundings in flat-spectrum radio quasars (FSRQs). In particular, sources emitting at high energies (>10 GeV) give us the strongest constraints. This motivates us to start a systematic study of flares with bright emission above 10 GeV, examining archival data of the Fermi-LAT gamma-ray telescope. At the same time, we began to trigger Target of Opportunity observations to the Swift observatory at the occurrence of high-energy flares, obtaining a wide coverage of the spectral energy distributions (SEDs) for several FSRQs during flares. Among others, we investigate the SEDmore » of a peculiar flare of 3C 454.3, showing a remarkably hard gamma-ray spectrum, quite different from the brightest flares of this source, and a bright flare of CTA 102. We modeled the SED in the framework of the one-zone leptonic model, using also archival optical spectroscopic data to derive the luminosity of the broad lines and thus estimate the disk luminosity, from which the structural parameters of the FSRQ nucleus can be inferred. The model allowed us to evaluate the magnetic field intensity in the blazar zone and to locate the emitting region of gamma-rays in the particular case in which gamma-ray spectra show neither absorption from the broad-line region (BLR) nor the Klein-Nishina curvature expected in leptonic models assuming the BLR as the source of seed photons for the External Compton scenario. For FSRQs bright above 10 GeV, we were able to identify short periods lasting less than one day characterized by a high rate of high-energy gamma-rays and hard gamma-ray spectra. We discussed the observed spectra and variability timescales in terms of injection and cooling of energetic particles, arguing that these flares could be triggered by magnetic reconnection events or turbulence in the flow.« less

Qualitative Assessment of the Acoustic Disturbance Environment in the NASA LaRC 20-Inch MACH 6 Wind Tunnel

NASA Technical Reports Server (NTRS)

Horvath, Thomas J.; Berry, Scott A.; Hamilton, H. Harris

2001-01-01

An experimental investigation was conducted on a 5-degree-half-angle cone with a flare in a conventional Mach 6 wind tunnel to examine the effect of facility noise on boundary layer transition. The effect of tunnel noise was inferred by comparing transition onset locations determined from the present test to that previously obtained in a Mach 6 quiet tunnel. Together, the two sets of experiments are believed to represent the first direct comparison of transition onset between a conventional and a quiet hypersonic wind tunnel using a common test model. In the present conventional hypersonic tunnel experiment, adiabatic wall temperatures were measured and heat transfer distributions were inferred on the cone flare model at zero degree angle of attack over a range of length Reynolds numbers (2 x 10(exp 6) to 10 x 10(exp 6)) which resulted in laminar and turbulent flow. Wall-to-total temperature ratio for the transient heating measurements and the adiabatic wall temperature measurements were 0.69 and 0.86, respectively. The cone flare nosetip radius was varied from 0.0001 to 0.125-inch to examine the effects of bluntness on transition onset. At comparable freestream conditions the transition onset Reynolds number obtained on the cone flare model in the conventional "noisy" tunnel was approximately 25% lower than that measured in the low disturbance tunnel.

The very high energy gamma ray spectra of IES 1959+650 and Mrk 421 as measured with the Whipple 10 m telescope

NASA Astrophysics Data System (ADS)

VERITAS Collaboration; Badran, H. M.; Bond, I. H.; Boyle, P. J.; Bradbury, S. M.; Buckley, J. H.; Byrum, K.; Carter-Lewis, D. A.; Celik, O.; Cogan, P.; Cui, W.; de La Calle Perez, I.; Duke, C.; Falcone, A.; Fegan, D. J.; Fegan, S. J.; Finley, J. P.; Fortson, L. F.; Gammell, S.; Gibbs, K.; Gillanders, G. H.; Grube, J.; Guiterrez, K. J.; Hall, J.; Hanna, D.; Holder, J.; Horan, D.; Hughes, S.; Humensky, T. B.; Jung, I.; Kenny, G. E.; Kertzman, M.; Kieda, D.; Kildea, J.; Knapp, J.; Kosack, K.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; Le Bohec, S.; Linton, E.; Lloyd-Evans, J.; Mendoza, D.; Merriman, A.; Milovanovic, A.; Moriarty, P.; Nagai, T.; Ong, R. A.; Pallassini, R.; Perkins, J.; Petry, D.; Pohl, M.; Power-Mooney, B.; Quinn, J.; Quinn, M.; Ragan, K.; Rebillot, P.; Reynolds, P. T.; Rose, H. J.; Schroedter, M.; Sembroski, G. H.; Swordy, S. P.; Syson, A.; Valcarcel, L.; Vassiliev, V. V.; Wagner, R.; Wakely, S. P.; Walker, G.; Weekes, T. C.; White, R. J.; Zweerink, J.

2005-02-01

In observations made with the Whipple 10 m telescope, 1ES 1959+650 (z = 0.048) was caught in a high flaring state in May 2002, concurrent with a high X-ray state, and in June 2002, for which there was no corresponding X-ray flare. The spectra for both of those occasions are well fitted by a power law of differential spectral index ~ -2.8. The relative stability of the spectral index for those flares argues strongly in favour of a two-component model as to the emission zones for the two radiation regimes. Markarian 421 (z = 0.031) was observed to be in a high flaring state, at levels of >= 3 Crab, during March and April 2004. The average spectrum over this time period shows evidence for a cut-off in the spectrum at ~ 5 TeV, similar to a cut-off seen during an equivalently strong episode of flaring activity in 2001. The continued appearance of this feature indicates a long term stability, either in the physical conditions at the source, or in the intervening medium (such as attenuation on the extra-galactic infra-red background radiation).

Effect of the X5.4 Class Solar Flare Event of Solar Cycle 24 ON the GPS Signal Reception in Peninsular Malaysia

NASA Astrophysics Data System (ADS)

Ismail, S.; Musa, T. A.; Aris, W. A. W.; Gopir, G.

2016-09-01

In this paper, we examine the effect of solar flare event on the Global Positioning System (GPS) signal reception in Peninsular Malaysia during the X5.4 class solar flare on 7th March 2012, 00:24 UT at active region AR1429. GPS data from six MyRTKnet stations that cover the northern, southern, western and eastern regions of Peninsular Malaysia were used, namely Langkawi (Kedah), Bandar Baharu (Pulau Pinang), Pekan (Pahang), Mersing (Johor), Tanjung Pengelih (Johor) and Malacca (Malacca). The total electron content (TEC) was estimated based on the single layer ionospheric model. Next, the ionospheric delay for each GPS frequency of L1 (1575.42 MHz), L2 (1227.60 MHz) and L5 (1176.45 MHz) was then calculated. The results show that solar flare event can influence the GPS signal reception in Peninsular Malaysia where the X5.4 class solar flare shows significant effect of the ionospheric delay within the range of 9 m - 20 m. These research findings will significantly contribute to space weather study and its effects on space-based positioning system such as the GPS.

The mean ionic charge of silicon in 3HE-rich solar flares

NASA Technical Reports Server (NTRS)

Luhn, A.; Klecker, B.; Hovestadt, E.; Moebius, E.

1985-01-01

Mean ionic charge of iron in 3He-rich solar flares and the average mean charge of Silicon for 23 #He-rich periods during the time interval from September 1978 to October 1979 were determined. It is indicated that the value of the mean charge state of Silicon is higher than the normal flare average by approximately 3 units and in perticular it is higher then the value predicted by resonant heating models for 3He-rich solar flares.

A Large-scale Search for Evidence of Quasi-periodic Pulsations in Solar Flares

NASA Astrophysics Data System (ADS)

Inglis, A. R.; Ireland, J.; Dennis, B. R.; Hayes, L.; Gallagher, P.

2016-12-01

The nature of quasi-periodic pulsations (QPP) in solar flares is poorly constrained, and critically the general prevalence of such signals in solar flares is unknown. Therefore, we perform a large-scale search for evidence of signals consistent with QPP in solar flares, focusing on the 1-300 s timescale. We analyze 675 M- and X-class flares observed by the Geostationary Operational Environmental Satellite (GOES) series in 1-8 Å soft X-rays between 2011 February 1 and 2015 December 31. Additionally, over the same era we analyze Fermi/Gamma-ray Burst Monitor (GBM) 15-25 keV X-ray data for each of these flares associated with a Fermi/GBM solar flare trigger, a total of 261 events. Using a model comparison method, we determine whether there is evidence for a substantial enhancement in the Fourier power spectrum that may be consistent with a QPP signature, based on three tested models; a power-law plus a constant, a broken power-law plus constant, and a power-law-plus-constant with an additional QPP signature component. From this, we determine that ˜30% of GOES events and ˜8% of Fermi/GBM events show strong signatures consistent with classical interpretations of QPP. For the remaining events either two or more tested models cannot be strongly distinguished from each other, or the events are well-described by single power-law or broken power-law Fourier power spectra. For both instruments, a preferred characteristic timescale of ˜5-30 s was found in the QPP-like events, with no dependence on flare magnitude in either GOES or GBM data. We also show that individual events in the sample show similar characteristic timescales in both GBM and GOES data sets. We discuss the implications of these results for our understanding of solar flares and possible QPP mechanisms.

A Large-Scale Search for Evidence of Quasi-Periodic Pulsations in Solar Flares

NASA Technical Reports Server (NTRS)

Inglis, A. R.; Ireland, J.; Dennis, B. R..; Hayes, L.; Gallagher, P.

2016-01-01

The nature of quasi-periodic pulsations (QPP) in solar flares is poorly constrained, and critically the general prevalence of such signals in solar flares is unknown. Therefore, we perform a large-scale search for evidence of signals consistent with QPP in solar flares, focusing on the 1300 s timescale. We analyze 675 M- and X-class flares observed by the Geostationary Operational Environmental Satellite (GOES) series in 18 soft X-rays between 2011 February 1 and 2015 December 31. Additionally, over the same era we analyze Fermi/Gamma-ray Burst Monitor (GBM) 1525 keV X-ray data for each of these flares associated with a Fermi/GBM solar flare trigger, a total of 261 events. Using a model comparison method, we determine whether there is evidence for a substantial enhancement in the Fourier power spectrum that may be consistent with a QPP signature, based on three tested models; a power-law plus a constant, a broken power-law plus constant, and a power-law-plus-constant with an additional QPP signature component. From this, we determine that approx. 30% of GOES events and approx. 8% of Fermi/GBM events show strong signatures consistent with classical interpretations of QPP. For the remaining events either two or more tested models cannot be strongly distinguished from each other, or the events are well-described by single power-law or broken power-law Fourier power spectra. For both instruments, a preferred characteristic time-scale of approx. 5-30 s was found in the QPP-like events, with no dependence on flare magnitude in either GOES or GBM data. We also show that individual events in the sample show similar characteristic time-scales in both GBM and GOES data sets. We discuss the implications of these results for our understanding of solar flares and possible QPP mechanisms.

A LARGE-SCALE SEARCH FOR EVIDENCE OF QUASI-PERIODIC PULSATIONS IN SOLAR FLARES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inglis, A. R.; Ireland, J.; Dennis, B. R.

The nature of quasi-periodic pulsations (QPP) in solar flares is poorly constrained, and critically the general prevalence of such signals in solar flares is unknown. Therefore, we perform a large-scale search for evidence of signals consistent with QPP in solar flares, focusing on the 1–300 s timescale. We analyze 675 M- and X-class flares observed by the Geostationary Operational Environmental Satellite (GOES) series in 1–8 Å soft X-rays between 2011 February 1 and 2015 December 31. Additionally, over the same era we analyze Fermi /Gamma-ray Burst Monitor (GBM) 15–25 keV X-ray data for each of these flares associated with amore » Fermi /GBM solar flare trigger, a total of 261 events. Using a model comparison method, we determine whether there is evidence for a substantial enhancement in the Fourier power spectrum that may be consistent with a QPP signature, based on three tested models; a power-law plus a constant, a broken power-law plus constant, and a power-law-plus-constant with an additional QPP signature component. From this, we determine that ∼30% of GOES events and ∼8% of Fermi /GBM events show strong signatures consistent with classical interpretations of QPP. For the remaining events either two or more tested models cannot be strongly distinguished from each other, or the events are well-described by single power-law or broken power-law Fourier power spectra. For both instruments, a preferred characteristic timescale of ∼5–30 s was found in the QPP-like events, with no dependence on flare magnitude in either GOES or GBM data. We also show that individual events in the sample show similar characteristic timescales in both GBM and GOES data sets. We discuss the implications of these results for our understanding of solar flares and possible QPP mechanisms.« less

Current Fragmentation and Particle Acceleration in Solar Flares

NASA Astrophysics Data System (ADS)

Cargill, P. J.; Vlahos, L.; Baumann, G.; Drake, J. F.; Nordlund, Å.

2012-11-01

Particle acceleration in solar flares remains an outstanding problem in plasma physics and space science. While the observed particle energies and timescales can perhaps be understood in terms of acceleration at a simple current sheet or turbulence site, the vast number of accelerated particles, and the fraction of flare energy in them, defies any simple explanation. The nature of energy storage and dissipation in the global coronal magnetic field is essential for understanding flare acceleration. Scenarios where the coronal field is stressed by complex photospheric motions lead to the formation of multiple current sheets, rather than the single monolithic current sheet proposed by some. The currents sheets in turn can fragment into multiple, smaller dissipation sites. MHD, kinetic and cellular automata models are used to demonstrate this feature. Particle acceleration in this environment thus involves interaction with many distributed accelerators. A series of examples demonstrate how acceleration works in such an environment. As required, acceleration is fast, and relativistic energies are readily attained. It is also shown that accelerated particles do indeed interact with multiple acceleration sites. Test particle models also demonstrate that a large number of particles can be accelerated, with a significant fraction of the flare energy associated with them. However, in the absence of feedback, and with limited numerical resolution, these results need to be viewed with caution. Particle in cell models can incorporate feedback and in one scenario suggest that acceleration can be limited by the energetic particles reaching the condition for firehose marginal stability. Contemporary issues such as footpoint particle acceleration are also discussed. It is also noted that the idea of a "standard flare model" is ill-conceived when the entire distribution of flare energies is considered.

Eruption of a Multiple-Turn Helical Magnetic Flux Tube in a Large Flare: Evidence for External and Internal Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions

NASA Technical Reports Server (NTRS)

Gary, G. Allen; Moore, R. L.

2003-01-01

We present observations and an interpretation of a unique multiple-turn spiral flux tube eruption from AR10030 on 2002 July 15. The TRACE CIV observations clearly show a flux tube that is helical and that is erupting from within a sheared magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The initiation of the helix eruption starts 25 seconds after the peak of the flare s strongest impulsive spike of microwave gryosynchrotron radiation early in the flare s explosive phase, implying that the sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double CME. The first external breakout reconnection apparently releases an underlying sheared core field and allows it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection heats the two-ribbon flare and might or might not produce the helix. These events lead to the first CME and are followed by a second breakout that initiates a second and larger halo CME. The strong magnetic shear in the region is associated with rapid proper motion and evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within a filament channel, and starts to erupt only after fast breakout reconnection has started. These observations are counter to the standard flare model and support the breakout model for eruptive flare initiation. However, the observations are compatible with internal reconnection in a sheared magnetic arcade in the formation and eruption of the helix.

Eruption of a Multiple-Turn Helical Magnetic Flux Tube in a Large Flare: Evidence for External and Internal Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions

NASA Technical Reports Server (NTRS)

Gary, G. Allen; Moore, R. L.

2004-01-01

We present observations and an interpretation of a unique multiple-turn spiral flux tube eruption from active region 10030 on 2002 July 15. The TRACE C IV observations clearly show a flux tube that is helical and erupting from within a sheared magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The initiation of the helix eruption. as determined by a linear backward extrapolation, starts 25 s after the peak of the flare's strongest impulsive spike of microwave gyrosynchrotron radiation early in the flare s explosive phase, implying that the sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double coronal mass ejection (CME). The first external breakout reconnection apparently releases an underlying sheared core field and allows it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection releases the helix and heats the two-ribbon flare. These events lead to the first CME and are followed by a second breakout that initiates a second and larger halo CME. The strong magnetic shear in the region is compatible with the observed rapid proper motion and evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within a filament channel. and starts to erupt only after fast breakout reconnection has started. These observations are counter to the standard flare model and support the breakout model for eruptive flare initiation.

The flares of August 1972. [solar flare characteristics and spectra

NASA Technical Reports Server (NTRS)

Zirin, H.; Tanaka, K.

1973-01-01

Observations of the August, 1972 flares at Big Bear and Tel Aviv, involving monochromatic movies, magnetograms, and spectra, are analyzed. The region (McMath 11976) showed inverted polarity from its inception on July 11; the great activity was due to extremely high shear and gradients in the magnetic field, as well as a constant invasion of one polarity into the opposite; observations in lambda 3835 show remarkable fast flashes in the impulsive flare of 18:38 UT on Aug. 2 with lifetimes of 5 sec, which may be due to dumping of particles in the lower chromosphere. Flare loops show evolutionary increases of their tilts to the neutral line in the flares of Aug. 4 and 7. Spectroscopic observations show red asymmetry and red shift of the H alpha emission in the flash phase of the Aug. 7 flare, as well as substantial velocity shear in the photosphere during the flare, somewhat like earthquake movement along a fault. Finally the total H alpha emission of the Aug. 7 flare could be measured accurately as about 2.5 x 10 to the 30th power erg, considerably less than coarser previous estimates for great flares.

Magnetohydrodynamic Simulations for Studying Solar Flare Trigger Mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muhamad, J.; Kusano, K.; Inoue, S.

In order to understand the flare trigger mechanism, we conduct three-dimensional magnetohydrodynamic simulations using a coronal magnetic field model derived from data observed by the Hinode satellite. Several types of magnetic bipoles are imposed into the photospheric boundary of the Nonlinear Force-free Field model of Active Region (AR) NOAA 10930 on 2006 December 13, to investigate what kind of magnetic disturbance may trigger the flare. As a result, we confirm that certain small bipole fields, which emerge into the highly sheared global magnetic field of an AR, can effectively trigger a flare. These bipole fields can be classified into twomore » groups based on their orientation relative to the polarity inversion line: the so-called opposite polarity, and reversed shear structures, as suggested by Kusano et al. We also investigate the structure of the footpoints of reconnected field lines. By comparing the distribution of reconstructed field lines and observed flare ribbons, the trigger structure of the flare can be inferred. Our simulation suggests that the data-constrained simulation, taking into account both the large-scale magnetic structure and small-scale magnetic disturbance (such as emerging fluxes), is a good way to discover a flare-producing AR, which can be applied to space weather prediction.« less

Simulating the Mg II NUV Spectra & C II Resonance Lines During Solar Flares

NASA Astrophysics Data System (ADS)

Kerr, Graham Stewart; Allred, Joel C.; Leenaarts, Jorrit; Butler, Elizabeth; Kowalski, Adam

2017-08-01

The solar chromosphere is the origin of the bulk of the enhanced radiative output during solar flares, and so comprehensive understanding of this region is important if we wish to understand energy transport in solar flares. It is only relatively recently, however, with the launch of IRIS that we have routine spectroscopic flarea observations of the chromsphere and transition region. Since several of the spectral lines observed by IRIS are optically thick, it is necessary to use forward modelling to extract the useful information that these lines carry about the flaring chromosphere and transition region. We present the results of modelling the formation properties Mg II resonance lines & subordinate lines, and the C II resonance lines during solar flares. We focus on understanding their relation to the physical strucutre of the flaring atmosphere, exploiting formation height differences to determine if we can extract information about gradients in the atmosphere. We show the effect of degrading the profiles to the resolution of the IRIS, and that the usual observational techniques used to identify the line centroid do a poor job in the early stages of the flare (partly due to multiple optically thick line components). Finally, we will tentatively comment on the effects that 3D radiation transfer may have on these lines.

Truncated disc surface brightness profiles produced by flares

NASA Astrophysics Data System (ADS)

Borlaff, Alejandro; Eliche-Moral, M. Carmen; Beckman, John; Font, Joan

2017-03-01

Previous studies have discarded that flares in galactic discs may explain the truncation that are frequently observed in highly-inclined galaxies (Kregel et al. 2002). However, no study has systematically analysed this hypothesis using realistic models for the disc, the flare and the bulge. We derive edge-on and face-on surface brightness profiles for a series of realistic galaxy models with flared discs that sample a wide range of structural and photometric parameters across the Hubble Sequence, accordingly to observations. The surface brightness profile for each galaxy model has been simulated for edge-on and face-on views to find out whether the flared disc produces a significant truncation in the disc in the edge-on view compared to the face-on view or not. In order to simulate realistic images of disc galaxies, we have considered the observational distribution of the photometric parameters as a function of the morphological type for three mass bins (10 < log10(M/M ⊙) < 10.7, 10.7 < log10(M/M ⊙) < 11 and log10(M/M ⊙) > 11), and four morphological type bins (S0-Sa, Sb-Sbc, Sc-Scd and Sd-Sdm). For each mass bin, we have restricted the photometric and structural parameters of each modelled galaxy to their characteristic observational ranges (μ0, disc, μeff, bulge, B/T, M abs, r eff, n bulge, h R, disc) and the flare in the disc (h z, disc/h R, disc, ∂h z, disc/∂R, see de Grijs & Peletier 1997, Graham 2001, López-Corredoira et al. 2002, Yoachim & Dalcanton 2006, Bizyaev et al. 2014, Mosenkov et al. 2015). Contrary to previous claims, the simulations show that realistic flared disks can be responsible for the truncations observed in many edge-on systems, preserving the profile of the non-flared analogous model in face-on view. These breaks reproduce the properties of the weak-to-intermediate breaks observed in many real Type-II galaxies in the diagram relating the radial location of the break (R brkII) in units of the inner disk scale-length with the break strength S (Laine et al. 2014). Radial variation of the scale-height of the disc (flaring) can explain the existence of many breaks in edge-on galaxies, especially of those with low break strengths 10\\frac{ho}{hi} \\sim \\ [-0.3,-0.1]$ .

Black carbon in the Arctic: the underestimated role of gas flaring and residential combustion emissions

NASA Astrophysics Data System (ADS)

Stohl, A.; Klimont, Z.; Eckhardt, S.; Kupiainen, K.; Shevchenko, V. P.; Kopeikin, V. M.; Novigatsky, A. N.

2013-09-01

Arctic haze is a seasonal phenomenon with high concentrations of accumulation-mode aerosols occurring in the Arctic in winter and early spring. Chemistry transport models and climate chemistry models struggle to reproduce this phenomenon, and this has recently prompted changes in aerosol removal schemes to remedy the modeling problems. In this paper, we show that shortcomings in current emission data sets are at least as important. We perform a 3 yr model simulation of black carbon (BC) with the Lagrangian particle dispersion model FLEXPART. The model is driven with a new emission data set ("ECLIPSE emissions") which includes emissions from gas flaring. While gas flaring is estimated to contribute less than 3% of global BC emissions in this data set, flaring dominates the estimated BC emissions in the Arctic (north of 66° N). Putting these emissions into our model, we find that flaring contributes 42% to the annual mean BC surface concentrations in the Arctic. In March, flaring even accounts for 52% of all Arctic BC near the surface. Most of the flaring BC remains close to the surface in the Arctic, so that the flaring contribution to BC in the middle and upper troposphere is small. Another important factor determining simulated BC concentrations is the seasonal variation of BC emissions from residential combustion (often also called domestic combustion, which is used synonymously in this paper). We have calculated daily residential combustion emissions using the heating degree day (HDD) concept based on ambient air temperature and compare results from model simulations using emissions with daily, monthly and annual time resolution. In January, the Arctic-mean surface concentrations of BC due to residential combustion emissions are 150% higher when using daily emissions than when using annually constant emissions. While there are concentration reductions in summer, they are smaller than the winter increases, leading to a systematic increase of annual mean Arctic BC surface concentrations due to residential combustion by 68% when using daily emissions. A large part (93%) of this systematic increase can be captured also when using monthly emissions; the increase is compensated by a decreased BC burden at lower latitudes. In a comparison with BC measurements at six Arctic stations, we find that using daily-varying residential combustion emissions and introducing gas flaring emissions leads to large improvements of the simulated Arctic BC, both in terms of mean concentration levels and simulated seasonality. Case studies based on BC and carbon monoxide (CO) measurements from the Zeppelin observatory appear to confirm flaring as an important BC source that can produce pollution plumes in the Arctic with a high BC / CO enhancement ratio, as expected for this source type. BC measurements taken during a research ship cruise in the White, Barents and Kara seas north of the region with strong flaring emissions reveal very high concentrations of the order of 200-400 ng m-3. The model underestimates these concentrations substantially, which indicates that the flaring emissions (and probably also other emissions in northern Siberia) are rather under- than overestimated in our emission data set. Our results suggest that it may not be "vertical transport that is too strong or scavenging rates that are too low" and "opposite biases in these processes" in the Arctic and elsewhere in current aerosol models, as suggested in a recent review article (Bond et al., Bounding the role of black carbon in the climate system: a scientific assessment, J. Geophys. Res., 2013), but missing emission sources and lacking time resolution of the emission data that are causing opposite model biases in simulated BC concentrations in the Arctic and in the mid-latitudes.

M Dwarf Flare Continuum Variations on One-second Timescales: Calibrating and Modeling of ULTRACAM Flare Color Indices

NASA Astrophysics Data System (ADS)

Kowalski, Adam F.; Mathioudakis, Mihalis; Hawley, Suzanne L.; Wisniewski, John P.; Dhillon, Vik S.; Marsh, Tom R.; Hilton, Eric J.; Brown, Benjamin P.

2016-04-01

We present a large data set of high-cadence dMe flare light curves obtained with custom continuum filters on the triple-beam, high-speed camera system ULTRACAM. The measurements provide constraints for models of the near-ultraviolet (NUV) and optical continuum spectral evolution on timescales of ≈1 s. We provide a robust interpretation of the flare emission in the ULTRACAM filters using simultaneously obtained low-resolution spectra during two moderate-sized flares in the dM4.5e star YZ CMi. By avoiding the spectral complexity within the broadband Johnson filters, the ULTRACAM filters are shown to characterize bona fide continuum emission in the NUV, blue, and red wavelength regimes. The NUV/blue flux ratio in flares is equivalent to a Balmer jump ratio, and the blue/red flux ratio provides an estimate for the color temperature of the optical continuum emission. We present a new “color-color” relationship for these continuum flux ratios at the peaks of the flares. Using the RADYN and RH codes, we interpret the ULTRACAM filter emission using the dominant emission processes from a radiative-hydrodynamic flare model with a high nonthermal electron beam flux, which explains a hot, T ≈ 104 K, color temperature at blue-to-red optical wavelengths and a small Balmer jump ratio as observed in moderate-sized and large flares alike. We also discuss the high time resolution, high signal-to-noise continuum color variations observed in YZ CMi during a giant flare, which increased the NUV flux from this star by over a factor of 100. Based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium, based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofsica de Canarias, and observations, and based on observations made with the ESO Telescopes at the La Silla Paranal Observatory under programme ID 085.D-0501(A).

Can Sgr A* flares reveal the molecular gas density PDF?

NASA Astrophysics Data System (ADS)

Churazov, E.; Khabibullin, I.; Sunyaev, R.; Ponti, G.

2017-11-01

Illumination of dense gas in the Central Molecular Zone by powerful X-ray flares from Sgr A* leads to prominent structures in the reflected emission that can be observed long after the end of the flare. By studying this emission, we learn about past activity of the supermassive black hole in our Galactic Center and, at the same time, we obtain unique information on the structure of molecular clouds that is essentially impossible to get by other means. Here we discuss how X-ray data can improve our knowledge of both sides of the problem. Existing data already provide (I) an estimate of the flare age, (II) a model-independent lower limit on the luminosity of Sgr A* during the flare and (III) an estimate of the total emitted energy during Sgr A* flare. On the molecular clouds side, the data clearly show a voids-and-walls structure of the clouds and can provide an almost unbiased probe of the mass/density distribution of the molecular gas with the hydrogen column densities lower than few 1023 cm-2. For instance, the probability distribution function of the gas density PDF(ρ) can be measured this way. Future high energy resolution X-ray missions will provide the information on the gas velocities, allowing, for example, a reconstruction of the velocity field structure functions and cross-matching the X-ray and molecular data based on positions and velocities.

Modeling of Ionosphere Effects of Geomagnetic Storm Sequence on September 9-14, 2005 in View of Solar Flares and Dependence of Model Input Parameters from AE-and Kp-indices

NASA Astrophysics Data System (ADS)

Klimenko, Maxim; Klimenko, Vladimir; Ratovsky, Konstantin; Goncharenko, Larisa

Earlier by Klimenko et al., 2009 under carrying out the calculations of the ionospheric effects of storm sequence on September 9-14, 2005 the model input parameters (potential difference through polar caps, field-aligned currents of the second region and particle precipitation fluxes and energy) were set as function of Kp-index of geomagnetic activity. The analyses of obtained results show that the reasons of quantitative distinctions of calculation results and observations can be: the use of 3 hour Kp-index at the setting of time dependence of model input parameters; the dipole approach of geomagnetic field; the absence in model calculations the effects of the solar flares, which were taken place during the considered period. In the given study the model input parameters were set as function of AE-and Kp-indices of geomagnetic activity according to different empirical models and morphological representations Feshchenko and Maltsev, 2003; Cheng et al., 2008; Zhang and Paxton, 2008. At that, we taken into account the shift of field-aligned currents of the second region to the lower latitudes as by Sojka et al., 1994 and 30 min. time delay of variations of the field-aligned currents of second region relative to the variations of the potential difference through polar caps at the storm sudden commencement phase. Also we taken into account the ionospheric effects of solar flares. Calculation of ionospheric effects of storm sequence has been carried out with use of the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) developed in WD IZMIRAN (Nam-galadze et al., 1988). We carried out the comparison of calculation results with experimental data. This study is supported by RFBR grant 08-05-00274. References Cheng Z.W., Shi J.K., Zhang T.L., Dunlop M. and Liu Z.X. Relationship between FAC at plasma sheet boundary layers and AE index during storms from August to October, 2001. Sci. China Ser. E-Tech. Sci., 2008, Vol. 51, No. 7, 842-848. Feshchenko E.Yu., Maltsev Yu.P. Relations of the polar cap voltage to the geophysical activity. Physics of Auroral Phenomena: XXVI Annual Seminar (February 25-28, 2003): Proc./PGI KSC RAS. Apatity, 2003, 59-61. Klimenko M.V., Klimenko V.V., Ratovsky K.G., and Goncharenko L.P. Numerical modeling of ionospheric parameters during sequence of geomagnetic storms on September 9-14, 2005. Physics of Auroral Phenomena: XXXII Annual Seminar (March 3-6, 2009): Proc./PGI KSC RAS. Apatity, 2009, 162-165. Namgaladze A.A., Korenkov Yu.N., Klimenko V.V., Karpov I.V., Bessarab F.S., Surotkin V.A., Glushenko T.A., Naumova N.M. Global model of the thermosphere-ionosphere-protonosphere system. Pure and Applied Geophysics (PAGEOPH), 1988, Vol. 127, No. 2/3, 219-254. Sojka J.J., Schunk R.W., Denig W.F. Ionospheric response to the sustained high geomagnetic activity during the March '89 great storm. J. Geophys. Res., 1994, Vol. 99, No. A11, 21341-21352. Zhang Y., Paxton L.J. An empirical Kp-dependent global auroral model based on TIMED/GUVI FUV data. J. Atmos. Solar-Terr. Phys., 2008, Vol. 70, 1231-1242.

Helium emission from model flare layers. [of outer solar atmosphere

NASA Technical Reports Server (NTRS)

Kulander, J. I.

1976-01-01

The emission of visible and UV He I and He II line radiation from a plane-parallel model flare layer characterized by electron temperatures of 10,000 to 50,000 K and electron densities of 10 to the 10th power to 10 to the 15th power per cu cm is analyzed by solving the statistical-equilibrium equations for a 30-level He I-II-III system, using parametric representations of the line and continuum radiation fields. The atomic model was chosen to provide accurate solutions for the first two resonance lines of He I and He II as well as for the D3 and 10,830-A lines of He I. Reaction rates are discussed, and sample solutions to the steady-state population equations are given for a generally optically thin gas assumed to be irradiated over 2pi sr by a blackbody spectrum at 6000 K. Specific results are examined for ionization equilibrium, level populations, approximate optical depths of a 1000-km-thick flare layer, line intensities, and upper-level population rates.

Hydrogen Balmer Line Broadening in Solar and Stellar Flares

NASA Technical Reports Server (NTRS)

Kowalski, Adam F.; Allred, Joel C.; Uitenbroek, Han; Tremblay, Pier-Emmanuel; Brown, Stephen; Carlsson, Mats; Osten, Rachel A.; Wisniewski, John P.; Hawley, Suzanne L.

2017-01-01

The broadening of the hydrogen lines during flares is thought to result from increased charge (electron, proton) density in the flare chromosphere. However, disagreements between theory and modeling prescriptions have precluded an accurate diagnostic of the degree of ionization and compression resulting from flare heating in the chromosphere. To resolve this issue, we have incorporated the unified theory of electric pressure broadening of the hydrogen lines into the non-LTE radiative-transfer code RH. This broadening prescription produces a much more realistic spectrum of the quiescent, A0 star Vega compared to the analytic approximations used as a damping parameter in the Voigt profiles. We test recent radiative-hydrodynamic (RHD) simulations of the atmospheric response to high nonthermal electron beam fluxes with the new broadening prescription and find that the Balmer lines are overbroadened at the densest times in the simulations. Adding many simultaneously heated and cooling model loops as a 'multithread' model improves the agreement with the observations. We revisit the three component phenomenological flare model of the YZ CMi Megaflare using recent and new RHD models. The evolution of the broadening, line flux ratios, and continuum flux ratios are well-reproduced by a multithread model with high-flux nonthermal electron beam heating, an extended decay phase model, and a 'hot spot' atmosphere heated by an ultra relativistic electron beam with reasonable filling factors: approximately 0.1%, 1%, and 0.1% of the visible stellar hemisphere, respectively. The new modeling motivates future work to understand the origin of the extended gradual phase emission.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Yunchun; Yang, Jiayan; Liu, Yu

In this paper, we report the interaction and subsequent merging of two sinistral filaments (F1 and F2) occurring at the boundary of AR 9720 on 2001 December 6. The two filaments were close and nearly perpendicular to each other. The interaction occurred after F1 was erupted and the eruption was impeded by a more extended filament channel (FC) standing in the way, in which F2 was embedded. The erupted material ran into FC along its axis, causing F1 and F2 to merge into a single structure that subsequently underwent a large-amplitude to-and-fro motion. A significant plasma heating process was observedmore » in the merging process, making the mixed material largely disappear from the Hα passband, but appear in Extreme Ultraviolet Telescope 195 Å images for a while. These observations can serve as strong evidence of merging reconnection between the two colliding magnetic structures. A new sinistral filament was formed along FC after the cooling of the merged and heated material. No coronal mass ejection was observed to be associated with the event; though, the eruption was accompanied by a two-ribbon flare with a separation motion, indicating that the eruption had failed. This event shows that, in addition to overlying magnetic fields, such an interaction is an effective restraint to make a filament eruption fail in this way.« less

NEW ASPECTS OF A LID-REMOVAL MECHANISM IN THE ONSET OF AN ERUPTION SEQUENCE THAT PRODUCED A LARGE SOLAR ENERGETIC PARTICLE (SEP) EVENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.

We examine a sequence of two ejective eruptions from a single active region on 2012 January 23, using magnetograms and EUV images from the Solar Dynamics Observatory's (SDO) Helioseismic and Magnetic Imager (HMI) and Atmospheric and Imaging Assembly (AIA), and EUV images from STEREO/EUVI. This sequence produced two coronal mass ejections (CMEs) and a strong solar energetic particle event (SEP); here we focus on the magnetic onset of this important space weather episode. Cheng et al. showed that the first eruption's ({sup E}ruption 1{sup )} flux rope was apparent only in ''hotter'' AIA channels, and that it removed overlying field thatmore » allowed the second eruption ({sup E}ruption 2{sup )} to begin via ideal MHD instability; here we say that Eruption 2 began via a ''lid removal'' mechanism. We show that during Eruption 1's onset, its flux rope underwent a ''tether weakening'' (TW) reconnection with field that arched from the eruption-source active region to an adjacent active region. Standard flare loops from Eruption 1 developed over Eruption 2's flux rope and enclosed filament, but these overarching new loops were unable to confine that flux rope/filament. Eruption 1's flare loops, from both TW reconnection and standard-flare-model internal reconnection, were much cooler than Eruption 2's flare loops (GOES thermal temperatures of ∼7.5 MK and 9 MK, compared to ∼14 MK). The corresponding three sequential GOES flares were, respectively, due to TW reconnection plus earlier phase Eruption 1 tether-cutting reconnection, Eruption 1 later-phase tether-cutting reconnection, and Eruption 2 tether-cutting reconnection.« less

Prediction of Shock Arrival Times from CME and Flare Data

NASA Technical Reports Server (NTRS)

Nunez, Marlon; Nieves-Chinchilla, Teresa; Pulkkinen, Antti

2016-01-01

This paper presents the Shock ARrival Model (SARM) for predicting shock arrival times for distances from 0.72 AU to 8.7 AU by using coronal mass ejections (CME) and flare data. SARM is an aerodynamic drag model described by a differential equation that has been calibrated with a dataset of 120 shocks observed from 1997 to 2010 by minimizing the mean absolute error (MAE), normalized to 1 AU. SARM should be used with CME data (radial, earthward or plane-of-sky speeds), and flare data (peak flux, duration, and location). In the case of 1 AU, the MAE and the median of absolute errors were 7.0 h and 5.0 h respectively, using the available CMEflare data. The best results for 1 AU (an MAE of 5.8 h) were obtained using both CME data, either radial or cone-model-estimated speeds, and flare data. For the prediction of shock arrivals at distances from 0.72 AU to 8.7 AU, the normalized MAE and the median were 7.1 h and 5.1 h respectively, using the available CMEflare data. SARM was also calibrated to be used with CME data alone or flare data alone, obtaining normalized MAE errors of 8.9 h and 8.6 h respectively for all shock events. The model verification was carried out with an additional dataset of 20 shocks observed from 2010 to 2012 with radial CME speeds to compare SARM with the empirical ESA model [Gopalswamy et al., 2005a] and the numerical MHD-based ENLIL model [Odstrcil et al., 2004]. The results show that the ENLIL's MAE was lower than the SARM's MAE, which was lower than the ESA's MAE. The SARM's best results were obtained when both flare and true CME speeds were used.

SoFAST: Automated Flare Detection with the PROBA2/SWAP EUV Imager

NASA Astrophysics Data System (ADS)

Bonte, K.; Berghmans, D.; De Groof, A.; Steed, K.; Poedts, S.

2013-08-01

The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV imager onboard PROBA2 provides a non-stop stream of coronal extreme-ultraviolet (EUV) images at a cadence of typically 130 seconds. These images show the solar drivers of space-weather, such as flares and erupting filaments. We have developed a software tool that automatically processes the images and localises and identifies flares. On one hand, the output of this software tool is intended as a service to the Space Weather Segment of ESA's Space Situational Awareness (SSA) program. On the other hand, we consider the PROBA2/SWAP images as a model for the data from the Extreme Ultraviolet Imager (EUI) instrument prepared for the future Solar Orbiter mission, where onboard intelligence is required for prioritising data within the challenging telemetry quota. In this article we present the concept of the software, the first statistics on its effectiveness and the online display in real time of its results. Our results indicate that it is not only possible to detect EUV flares automatically in an acquired dataset, but that quantifying a range of EUV dynamics is also possible. The method is based on thresholding of macropixelled image sequences. The robustness and simplicity of the algorithm is a clear advantage for future onboard use.

Requirements for flare reactions of joint inflammation induced in mice by cloned MT4+, Lyt-2- T cells.

PubMed

Klasen, I S; Ladestein, R M; van den Berg, W B; Benner, R

1989-03-01

Joint inflammation was induced in C57B1/6 mice by injection of cloned MT4+, Lyt-2- T cells specific for the antigen methylated bovine serum albumin (mBSA), together with mBSA. In this model, after waning of the inflammation, flare reactions can be induced by a rechallenge with the specific antigen. Herein we show that such flare reactions can still be induced several weeks after waning of the joint inflammation, as was demonstrated both in normal C57B1/6 mice and in athymic C57B1 nude mice. The results in the latter group indicate that T cells of the recipient mice are not necessary for the elicitation of flare reactions. On histologic examination, the inflammatory infiltrates in the knee joints of the nude mice appeared to be mainly granulocytic. The cloned T cells persisted and remained functionally reactive in the knee joint for at least 2 weeks in the absence of the antigen, and thus, in the absence of inflammation. In view of the similarities between induced joint inflammation in mice and rheumatoid arthritis in humans, these data may be relevant to our understanding of the processes involved in the latter disease.

Rotational modulation and flares on RS CVn and BY DRA systems. VIII - Simultaneous EXOSAT and H-alpha observations of a flare on the dMe star GL 644 AB (Wolf 630) on 24/25 August 1985

NASA Astrophysics Data System (ADS)

Doyle, J. G.; Butler, C. J.; Callanan, P. J.; Tagliaferri, G.; de La Reza, R.; White, N. E.; Torres, C. A.; Quast, G.

1988-02-01

A large flare was detected simultaneously in X-rays and H-alpha on the visual binary Gl 644 AB at about 00:15 UT on August 25, 1985. The flare was detected with both the low (0.05-2 keV) and medium energy (2-7 keV) experiments onboard Exosat, with the flare rise time being similar in both the low and medium energy ranges, although in the low energy the peak occurred about 30 s later. This was followed a few minutes later by a second burst. The flare decay time lasted about 10 minutes longer in the low energy band than in the medium energy. The integrated flare energy detected was 11.9 x 10 to the 32nd and 4.15 x 10 to the 32nd erg respectively in the low and medium energy X-rays and 7 x 10 to the 31st erg in H-alpha. This gives an H-alpha flux of approximately 4 percent of the total X-ray flux detected from the flare or 6 percent of the low X-ray flare energy, similar to that observed in a compact solar flare. Based on the observed cooling time, the flare was estimated to have 2-3 loops of height about 10 to the 9th cm and electron density of about 10 to the 12th/cu cm.

Statistical research into low-power solar flares. Main phase duration

NASA Astrophysics Data System (ADS)

Borovik, Aleksandr; Zhdanov, Anton

2017-12-01

This paper is a sequel to earlier papers on time parameters of solar flares in the Hα line. Using data from the International Flare Patrol, an electronic database of solar flares for the period 1972-2010 has been created. The statistical analysis of the duration of the main phase has shown that it increases with increasing flare class and brightness. It has been found that the duration of the main phase depends on the type and features of development of solar flares. Flares with one brilliant point have the shortest main phase; flares with several intensity maxima and two-ribbon flares, the longest one. We have identified more than 3000 cases with an ultra-long duration of the main phase (more than 60 minutes). For 90% of such flares the duration of the main phase is 2-3 hrs, but sometimes it reaches 12 hrs.

Kepler Flares. IV. A Comprehensive Analysis of the Activity of the dM4e Star GJ 1243

NASA Astrophysics Data System (ADS)

Silverberg, Steven M.; Kowalski, Adam F.; Davenport, James R. A.; Wisniewski, John P.; Hawley, Suzanne L.; Hilton, Eric J.

2016-10-01

We present a comprehensive study of the active dM4e star GJ 1243. We use previous observations and ground-based echelle spectroscopy to determine that GJ 1243 is a member of the Argus association of field stars, suggesting it is ∼ 30{--}50 {{Myr}} old. We analyze 11 months of 1 minute cadence data from Kepler, presenting Kepler flare frequency distributions, as well as determining correlations between flare energy, amplitude, duration, and decay time. We find that the exponent α of the power-law flare energy distribution varies in time, primarily due to completeness of sample and the low frequency of high-energy flares. We also find a deviation from a single power law at high energy. We use ground-based spectroscopic observations that were simultaneous with the Kepler data to provide simultaneous photometric and spectroscopic analysis of three low-energy flares, the lowest-energy dMe flares with detailed spectral analysis to date on any star. The spectroscopic data from these flares extend constraints for radiative hydrodynamic flare models to a lower energy regime than has previously been studied. We use this simultaneous spectroscopy and Kepler photometry to develop approximate conversions from the Kepler bandpass to the traditional U and B bands. This conversion will be a critical factor in comparing any Kepler flare analyses to the canon of previous ground-based flare studies.

Study of magnetic helicity injection in the active region NOAA 9236 producing multiple flare-associated coronal mass ejection events

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Sung-Hong; Cho, Kyung-Suk; Bong, Su-Chan

To better understand a preferred magnetic field configuration and its evolution during coronal mass ejection (CME) events, we investigated the spatial and temporal evolution of photospheric magnetic fields in the active region NOAA 9236 that produced eight flare-associated CMEs during the time period of 2000 November 23-26. The time variations of the total magnetic helicity injection rate and the total unsigned magnetic flux are determined and examined not only in the entire active region but also in some local regions such as the main sunspots and the CME-associated flaring regions using SOHO/MDI magnetogram data. As a result, we found thatmore » (1) in the sunspots, a large amount of positive (right-handed) magnetic helicity was injected during most of the examined time period, (2) in the flare region, there was a continuous injection of negative (left-handed) magnetic helicity during the entire period, accompanied by a large increase of the unsigned magnetic flux, and (3) the flaring regions were mainly composed of emerging bipoles of magnetic fragments in which magnetic field lines have substantially favorable conditions for making reconnection with large-scale, overlying, and oppositely directed magnetic field lines connecting the main sunspots. These observational findings can also be well explained by some MHD numerical simulations for CME initiation (e.g., reconnection-favored emerging flux models). We therefore conclude that reconnection-favored magnetic fields in the flaring emerging flux regions play a crucial role in producing the multiple flare-associated CMEs in NOAA 9236.« less

Onset of solar flares as predicted by two-dimensional MHD-models of quiescent prominences

NASA Technical Reports Server (NTRS)

Galindotrejo, J.

1985-01-01

The close connection between the sudden disapperance (disparition brusque) of the quiescent prominences and the two-ribbon flares are well known. During this dynamic phase the prominence ascends rapidly (typically with a velocity about 100 Km/sec) and disappears. In another later stage is observed material falling back into the chromosphere. The impact of this downfalling matter on the chromosphere produces the H brightening, which shows the symmetric double pattern. The occurence of the disparition brusque is thought to be a consequence of a plasma instability of magnetohydrostatic (MHD) structures. By means of the MHD-energy principle, the stability properties of four prominence models are analyzed. It is shown that all considered models undergo instabilities for parameters outside of the observed range at quiescent prominences. The possibility that such instabilities in the flare parameter range may indicate just the onset of a flare is considered.

Mini-filament Eruptions Triggering Confined Solar Flares Observed by ONSET and SDO

NASA Astrophysics Data System (ADS)

Yang, Shuhong; Zhang, Jun

2018-06-01

Using the observations from the Optical and Near-infrared Solar Eruption Tracer (ONSET) and the Solar Dynamics Observatory (SDO), we study an M5.7 flare in AR 11476 on 2012 May 10 and a micro-flare in the quiet Sun on 2017 March 23. Before the onset of each flare, there is a reverse S-shaped filament above the polarity inversion line, then the filaments become unstable and begin to rise. The rising filaments gain the upper hand over the tension force of the dome-like overlying loops and thus successfully erupt outward. The footpoints of the reconnecting overlying loops successively brighten and are observed as two flare ribbons, while the newly formed low-lying loops appear as post-flare loops. These eruptions are similar to the classical model of successful filament eruptions associated with coronal mass ejections (CMEs). However, the erupting filaments in this study move along large-scale lines and eventually reach the remote solar surface; i.e., no filament material is ejected into the interplanetary space. Thus, both the flares are confined. These results reveal that some successful filament eruptions can trigger confined flares. Our observations also imply that this kind of filament eruption may be ubiquitous on the Sun, from active regions (ARs) with large flares to the quiet Sun with micro-flares.

Theoretical studies of the solar atmosphere and interstellar pickup ions

NASA Technical Reports Server (NTRS)

1994-01-01

Solar atmosphere research activities are summarized. Specific topics addressed include: (1) coronal mass ejections and related phenomena; (2) parametric instabilities of Alfven waves; (3) pickup ions in the solar wind; and (4) cosmic rays in the outer heliosphere. Also included is a list of publications covering the following topics: catastrophic evolution of a force-free flux rope; maximum energy release in flux-rope models of eruptive flares; sheet approximations in models of eruptive flares; material ejection, motions of loops and ribbons of two-ribbon flares; dispersion relations for parametric instabilities of parallel-propagating; parametric instabilities of parallel-propagating Alfven waves; beat, modulation, and decay instabilities of a circularly-polarized Alfven wave; effects of time-dependent photoionization on interstellar pickup helium; observation of waves generated by the solar wind pickup of interstellar hydrogen ions; ion thermalization and wave excitation downstream of the quasi-perpendicular bowshock; ion cyclotron instability and the inverse correlation between proton anisotrophy and proton beta; and effects of cosmic rays and interstellar gas on the dynamics of a wind.

Multi-wavelength observations of PKS 2142-75 during active and quiescent gamma-ray states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutka, Michael S.; Ojha, Roopesh; Pottschmidt, Katja

2013-12-04

Here, PKS 2142–75 (a.k.a. 2FGL J2147.4–7534) is a flat-spectrum radio quasar that was observed quasi-simultaneously by a suite of instruments across the electromagnetic spectrum during two flaring states in 2010 April and 2011 August as well as a quiescent state from 2011 December through 2012 January. The results of these campaigns and model spectral energy distributions (SEDs) from the active and quiescent states are presented. The SED model parameters of PKS 2142–75 indicate that the two flares of the source are created by unique physical conditions. SED studies of flat-spectrum radio quasars are beginning to indicate that there might bemore » two types of flares, those that can be described purely by changes in the electron distribution and those that require changes in other parameters, such as the magnetic field strength or the size of the emitting region.« less

Orbit of the OJ287 black hole binary as determined from the General Relativity centenary flare

NASA Astrophysics Data System (ADS)

Valtonen, Mauri; Gopakumar, Achamveedu; Mikkola, Seppo; Zola, Staszek; Ciprini, Stefano; Matsumoto, Katsura; Sadakane, Kozo; Kidger, Mark; Gazeas, Kosmas; Nilsson, Kari; Berdyugin, Andrei; Piirola, Vilppu; Jermak, Helen; Baliyan, Kiran; Hudec, Rene; Reichart, Daniel

2016-05-01

OJ287 goes through large optical flares twice each 12 years. The times of these flares have been predicted successfully now 5 times using a black hole binary model. In this model a secondary black hole goes around a primary black hole, impacting the accretion disk of the latter twice per orbital period, creating a thermal flare. Together with 6 flares from the historical data base, the set of flare timings determines uniquely the 7 parameters of the model: the two masses, the primary spin, the major axis, eccentricity and the phase of the orbit, plus a time delay parameter that gives the extent of time between accretion disk impacts and the related optical flares. Based on observations by the OJ287-15/16 Collaboration, OJ287 went into the phase of rapid flux rise on November 25, on the centenary of Einstein’s General Relativity, and peaked on December 5. At that time OJ287 was the brightest in over 30 years in optical wavelengths. The flare was of low polarization, and did not extend beyond the optical/UV region of the spectrum. On top of the main flare there were a number of small flares; their excess brightness correlates well with the simultaneous X-ray data. With these properties the main flare qualifies as the marker of the orbit of the secondary going around the primary black hole. Since the orbit solution is strongly over-determined, its parameters are known very accurately, at better than one percent level for the masses and the spin. The next flare is predicted to peak on July 28, 2019.Detailed monitoring of this event should allow us to test, for the first time, the celebrated black hole no-hair theorem for a massive black hole at the 10% level. The present data is consistent with the theorem only at a 30% level. The main difficulty in observing OJ287 from Earth at our predicted epoch is its closeness to the sun. Therefore, it is desirable to monitor OJ287 from a space-based telescope not in the vicinity of Earth. Unfortunately, this unique opportunity for testing the above celebrated theorem of General Relativity using OJ287 will not be available again until after several orbital cycles.The full list of participants in the OJ287-15/16 Collaboration is found in ApJL 819, L37, 2016.

Multi-wavelength Observations of Blazar AO 0235+164 in the 2008-2009 Flaring State

NASA Astrophysics Data System (ADS)

Ackermann, M.; Ajello, M.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cutini, S.; D'Ammando, F.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Fuhrmann, L.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hughes, R. E.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Lee, S.-H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Nishino, S.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Pelassa, V.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Rastawicki, D.; Razzano, M.; Readhead, A.; Reimer, A.; Reimer, O.; Reyes, L. C.; Richards, J. L.; Sbarra, C.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Szostek, A.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Zimmer, S.; Fermi-LAT Collaboration; Moderski, R.; Nalewajko, K.; Sikora, M.; Villata, M.; Raiteri, C. M.; Aller, H. D.; Aller, M. F.; Arkharov, A. A.; Benítez, E.; Berdyugin, A.; Blinov, D. A.; Boettcher, M.; Bravo Calle, O. J. A.; Buemi, C. S.; Carosati, D.; Chen, W. P.; Diltz, C.; Di Paola, A.; Dolci, M.; Efimova, N. V.; Forné, E.; Gurwell, M. A.; Heidt, J.; Hiriart, D.; Jordan, B.; Kimeridze, G.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Kurtanidze, O. M.; Lähteenmäki, A.; Larionova, E. G.; Larionova, L. V.; Larionov, V. M.; Leto, P.; Lindfors, E.; Lin, H. C.; Morozova, D. A.; Nikolashvili, M. G.; Nilsson, K.; Oksman, M.; Roustazadeh, P.; Sievers, A.; Sigua, L. A.; Sillanpää, A.; Takahashi, T.; Takalo, L. O.; Tornikoski, M.; Trigilio, C.; Troitsky, I. S.; Umana, G.; GASP-WEBT Consortium; Angelakis, E.; Krichbaum, T. P.; Nestoras, I.; Riquelme, D.; F-GAMMA; Krips, M.; Trippe, S.; Iram-PdBI; Arai, A.; Kawabata, K. S.; Sakimoto, K.; Sasada, M.; Sato, S.; Uemura, M.; Yamanaka, M.; Yoshida, M.; Kanata; Belloni, T.; Tagliaferri, G.; RXTE; Bonning, E. W.; Isler, J.; Urry, C. M.; SMARTS; Hoversten, E.; Falcone, A.; Pagani, C.; Stroh, M.; (Swift-XRT

2012-06-01

The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to γ-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the γ-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R g. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus.

Testing Solar Flare Models with BATSE

NASA Astrophysics Data System (ADS)

Zarro, Dominic M.

1995-07-01

We propose to use high-sensitivity Burst and Transient Source Experiment (BATSE) hard X-ray observations to test the thick-target and electric field acceleration models of solar flares. We will compare the predictions made by these models with hard X-ray spectral observations obtained with BATSE and simultaneous soft X-ray Ca XIX emission observed with the Yohkoh Bragg Crystal Spectrometer (BCS). The increased sensitivities of the BATSE and BCS (relative to previous detectors) permits a renewed study of the relationship between heating and dynamical motions during the crucial rise phase of flares. With these observations, we will: (1) investigate the ability of the thick-target model to explain the temporal evolution of hard X-ray emission relative to the soft X-ray blueshift during the earliest stages of the impulsive phase; and (2) search for evidence of electric-field acceleration as implied by temporal correlations between hard X-ray spectral breaks and the Ca XIX blueshift. The proposed study will utilize hard X-ray lightcurve and spectral measurements in the 10-100 keV energy range obtained with the BATSE Large Area Detectors (LAD). The DISCLA and CONT data will be the primary data products used in this analysis.

HOOKED FLARE RIBBONS AND FLUX-ROPE-RELATED QSL FOOTPRINTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Jie; Li, Hui; Gilchrist, Stuart A.

2016-05-20

We studied the magnetic topology of active region 12158 on 2014 September 10 and compared it with the observations before and early in the flare that begins at 17:21 UT (SOL2014-09-10T17:45:00). Our results show that the sigmoidal structure and flare ribbons of this active region observed by the Solar Dynamics Observatory /Atmospheric Imaging Assembly can be well reproduced from a Grad–Rubin nonlinear force-free field extrapolation method. Various inverse-S- and inverse-J-shaped magnetic field lines, which surround a coronal flux rope, coincide with the sigmoid as observed in different extreme-ultraviolet wavelengths, including its multithreaded curved ends. Also, the observed distribution of surfacemore » currents in the magnetic polarity where it was not prescribed is well reproduced. This validates our numerical implementation and setup of the Grad–Rubin method. The modeled double inverse-J-shaped quasi-separatrix layer (QSL) footprints match the observed flare ribbons during the rising phase of the flare, including their hooked parts. The spiral-like shape of the latter may be related to a complex pre-eruptive flux rope with more than one turn of twist, as obtained in the model. These ribbon-associated flux-rope QSL footprints are consistent with the new standard flare model in 3D, with the presence of a hyperbolic flux tube located below an inverse-teardrop-shaped coronal QSL. This is a new step forward forecasting the locations of reconnection and ribbons in solar flares and the geometrical properties of eruptive flux ropes.« less

Characteristics of Solar Flare Hard X-ray Emissions: Observations and Models

NASA Astrophysics Data System (ADS)

Liu, Wei

2006-12-01

The main theme of this thesis is the investigation of the physics of acceleration and transport of particles in solar flares, and their thermal and nonthermal radiative signatures. The observational studies, using hard X-rays (HXRs) observed by the RHESSI mission, concentrate on four flares, which support the classical magnetic reconnection model of solar flares in various ways. In the X3.9 flare occurring on 11/03/2003, there is a monotonic upward motion of the loop top (LT) source accompanied by a systematic increase in the separation of the footpoint (FP) sources at a comparable speed. This is consistent with the reconnection model with an inverted-Y geometry. The 04/30/2002 event exhibits rarely observed two coronal sources. The two sources (with almost identical spectra) show energy-dependent structures, with higher-energy emission being close together. This suggests that reconnection takes place within the region between the sources. In the 10/29/2003 X10 flare, the logarithmic total HXR flux of the FPs correlates with the mean magnetic field. The two FPs show asymmetric HXR fluxes, which is qualitatively consistent with the magnetic mirroring effect. The M1.7 flare on 11/13/2003 reveals evidence of evaporation directly imaged by RHESSI for the first time, in which emission from the legs of the loop appears at intermediate energies. The emission centroid moves toward the LT as time proceeds, indicating an increase of density in the loop. The theoretical modeling of this work combines the stochastic acceleration model with the NRL hydrodynamic model to study the interplay of the particle acceleration, transport, and radiation effects and the atmospheric response to the energy deposition by nonthermal electrons. We find that low-energy electrons in the quasi-thermal portion of the spectrum affects the hydrodynamics by producing more heating in the corona than the previous models that used a power-law spectrum with a low-energy cutoff. The Neupert effect is found to be present and effects of suppression of conduction are tested in the presence of hydrodynamic flows.

Measurements of the spatial structure and directivity of 100 KeV photon sources in solar flares using PVO and ISEE-3 spacecraft

NASA Technical Reports Server (NTRS)

Anderson, Kinsey A.

1991-01-01

The objective of this grant was to measure the spatial structure and directivity of the hard X-ray and low energy gamma-ray (100 keV-2 MeV) continuum sources in solar flares using stereoscopic observations made with spectrometers aboard the Pioneer Venus Orbiter (PVO) and Third International Sun Earth Explorer (ISEE-3) spacecraft. Since the hard X-ray emission is produced by energetic electrons through the bremsstrahlung process, the observed directivity can be directly related to the 'beaming' of electrons accelerated during the flare as they propagate from the acceleration region in the corona to the chromosphere/transition region. Some models (e.g., the thick-target model) predict that most of the impulsive hard X-ray/low energy gamma-ray source is located in the chromosphere, the effective height of the X-ray source above the photosphere increasing with the decrease in the photon energy. This can be verified by determining the height-dependence of the photon source through stereoscopic observations of those flares which are partially occulted from the view of one of the two spacecraft. Thus predictions about beaming of electrons as well as their spatial distributions could be tested through the analysis proposed under this grant.

DISCOVERY OF 6.035 GHz HYDROXYL MASER FLARES IN IRAS 18566+0408

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Marzouk, A. A.; Araya, E. D.; Hofner, P.

2012-05-10

We report the discovery of 6.035 GHz hydroxyl (OH) maser flares toward the massive star-forming region IRAS 18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8 GHz H{sub 2}CO) and methanol (6.7 GHz CH{sub 3}OH) maser flares. The observations were conducted between 2008 October and 2010 January with the 305 m Arecibo Telescope in Puerto Rico. We detected two flare events, one in 2009 March and one in 2009 September to November. The OH maser flares are not simultaneous with the H{sub 2}CO flares, but may be correlated with CH{sub 3}OH flares from a component atmore » corresponding velocities. A possible correlated variability of OH and CH{sub 3}OH masers in IRAS 18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.« less

Characteristics of gamma-ray line flares

NASA Technical Reports Server (NTRS)

Bai, T.; Dennis, B.

1983-01-01

Observations of solar gamma rays by the Solar Maximum Mission (SMM) demonstrate that energetic protons and ions are rapidly accelerated during the impulsive phase. To understand the acceleration mechanisms for these particles, the characteristics of the gamma ray line flares observed by SMM were studied. Some very intense hard X-ray flares without detectable gamma ray lines were also investigated. Gamma ray line flares are distinguished from other flares by: (1) intense hard X-ray and microwave emissions; (2) delay of high energy hard X-rays; (3) emission of type 2 and/or type 4 radio bursts; and (4) flat hard X-ray spectra (average power law index: 3.1). The majority of the gamma ray line flares shared all these characteristics, and the remainder shared at least three of them. Positive correlations were found between durations of spike bursts and spatial sizes of flare loops as well as between delay times and durations of spike bursts.

Short duration flares in GALEX data

NASA Astrophysics Data System (ADS)

Brasseur, Clara; Osten, Rachel A.

2018-06-01

Flares on cool stars indicate short time-scale magnetic reconnection processes that provide temporary increases in the stellar radiative output. While recent work has focused on long-duration flares from solar-like stars and those of lower mass, the existence of short-duration flares in the ultraviolet has not been systematically probed before. We will present an interesting population of short duration flares we discovered in a sample of ~37,000 light curves observed from 2009-2012 by the GALEX and Kepler missions. These flares range in duration from under a minute to a few minutes and are almost entirely distinct from a previous flare survey of Kepler data. We were able to detect this unique population of flares because the time resolution of the GALEX data allowed us to construct light curves with a 10 second cadence and thus detect shorter duration flares than could be detected within Kepler data. We applied algorithmic flare detection to a sample of ~37,000 stars, and identified a final count of 2,065 flares on 1,121 stars. We discuss the implication of these events for the flare frequency distributions of solar-like stars.

Thermal Structure of Supra-Arcade Plasma in Two Solar Flares

NASA Technical Reports Server (NTRS)

Reeves, Katharine K.; Savage, Sabrina; McKenzie, David E.; Weber, Mark A.

2012-01-01

In this work, we use Hinode/XRT and SDO/AIA data to determine the thermal structure of supra-arcade plasma in two solar flares. The first flare is a Ml.2 flare that occurred on November 5, 2010 on the east limb. This flare was one of a series of flares from AR 11121, published in Reeves & Golub (2011). The second flare is an XI.7 flare that occurred on January 27, 2012 on the west limb. This flare exhibits visible supra-arcade downflows (SADs), where the November 2010 flare does not. For these two flares we combine XRT and AlA data to calculate DEMs of each pixel in the supra-arcade plasma, giving insight into the temperature and density structures in the fan of plasma above the post-flare arcade. We find in each case that the supra-arcade plasma is around 10 MK, and there is a marked decrease in the emission measure in the SADs. We also compare the DEMs calculated with the combined AIA/XRT dataset to those calculated using AIA alone.

The frequency of and associations with hospitalization secondary to lupus flares from the 1000 Faces of Lupus Canadian cohort.

PubMed

Lee, J; Peschken, C A; Muangchan, C; Silverman, E; Pineau, C; Smith, C D; Arbillaga, H; Zummer, M; Clarke, A; Bernatsky, S; Hudson, M; Hitchon, C; Fortin, P R; Pope, J E

2013-11-01

Hospitalization is a major factor in health care costs and a surrogate for worse outcomes in chronic disease. The aim of this study was to determine the frequency of hospitalization secondary to lupus flare, the causes of hospitalization, and to determine risk factors for hospitalization in patients with systemic lupus erythematosus (SLE). Data were collected as part of the 1000 Canadian Faces of Lupus, a prospective cohort study, where annual major lupus flares including hospitalizations were recorded over a 3-year period. Of 665 patients with available hospitalization histories, 68 reported hospitalization related to a SLE flare over 3 years of follow-up. The average annual hospitalization rate was 7.6% (range 6.6-8.9%). The most common reasons for hospitalization were: hematologic (22.1%), serositis (20.6%), musculoskeletal (MSK) (16.2%), and renal (14.7%). Univariate risk factors for lupus hospitalization included (OR [95% CI]; p < 0.05): juvenile-onset lupus (2.2 [1.1-4.7]), number of ACR SLE criteria (1.4 [1.1-1.7], baseline body mass index (BMI) (1.1 [1.0-1.1]), psychosis (3.4 [1.2-9.9]), aboriginal race (3.2 [1.5-6.7]), anti-Smith (2.6 [1.2-5.4]), erythrocyte sedimentation rate >25 mm/hr (1.9 [1.1-3.4]), proteinuria >0.5 g/d (4.2 [1.9-9.3], and SLAM-2 score (1.1 [1.0-1.2]). After multivariate regression only BMI, number of ACR criteria, and psychosis were associated with hospitalization for lupus flare. The mean annual rate of hospitalization attributed to lupus was lower than expected. Hematologic, serositis, MSK and renal were the most common reasons. In a regression model elevated BMI, more ACR criteria and psychosis were associated with hospitalization.

Influence of magnetic field structure on the conduction cooling of flare loops

NASA Technical Reports Server (NTRS)

Antiochos, S. K.; Sturrock, P. A.

1976-01-01

A simple model facilitates calculation of the influence of magnetic-field configuration on the conduction cooling rate of a hot post-flare coronal plasma. The magnetic field is taken to be that produced by a line dipole or point dipole at an arbitrary depth below the chromosphere. For the high temperatures (at least 10 million K) produced by flares, the plasma may remain static and isobaric. The influence of the field is such as to increase the heat flux (per unit area) into the chromosphere, but to decrease the total conduction cooling of the flare plasma. This leads to a significant enhancement of the total energy radiated by the flare plasma.

Derivation of the physical parameters for strong and weak flares from the Hα line

NASA Astrophysics Data System (ADS)

Semeida, M. A.; Rashed, M. G.

2016-06-01

The two flares of 19 and 30 July 1999 were observed in the Hα line using the multichannel flare spectrograph (MFS) at the Astronomical Institute in Ondřejov, Czech Republic. We use a modified cloud method to fit the Hα line profiles which avoids using the background profile. We obtain the four parameters of the two flares: the source function, the optical thickness at line center, the line-of-sight velocity and the Doppler width. The observed asymmetry profiles have been reproduced by the theoretical ones based on our model. A discussion is made about the results of strong and weak flares using the present method.

Search for Intra-day Optical Variability in Mrk 501

NASA Astrophysics Data System (ADS)

Feng, Hai-Cheng; Liu, H. T.; Fan, X. L.; Zhao, Yinghe; Bai, J. M.; Wang, Fang; Xiong, D. R.; Li, S. K.

2017-11-01

We present our observations of the optical intra-day variability (IDV) in γ-ray BL Lac object Mrk 501. The observations were run with the 1.02 m and 2.4 m optical telescopes at Yunnan Observatories from 2005 April to 2012 May. The light curve at the R band on 2010 May 15 passes both variability tests (the F-test and the ANOVA test). A flare within the light curve on 2010 May 15 has a magnitude change of {{Δ }}m=0.03+/- {0.005}{stat}+/- {0.007}{sys} mag, a darkening timescale of {τ }{{d}}=26.7 minutes, and an amplitude of IDV {Amp}=2.9 % +/- 0.7 % . A decline described by 11 consecutive flux measurements within the flare can be fitted linearly with a Pearson’s correlation coefficient r = 0.945 at the confidence level of > 99.99 % . Under the assumptions that the IDV is tightly connected to the mass of the black hole, and that the flare duration, being two times {τ }{{d}}, is representative of the minimum characteristic timescale, we can derive upper bounds to the mass of the black hole. In the case of the Kerr black hole, the timescale of {{Δ }}{t}\\min {ob}=0.89 hr gives {M}\\bullet ≲ {10}9.20{M}⊙ , which is consistent with measurements reported in the literature. This agreement indicates that the hypothesis about {M}\\bullet and {{Δ }}{t}\\min {ob} is consistent with the measurements/data.

Solar Activity from 2006 to 2014 and Short-term Forecasts of Solar Proton Events Using the ESPERTA Model

NASA Astrophysics Data System (ADS)

Alberti, T.; Laurenza, M.; Cliver, E. W.; Storini, M.; Consolini, G.; Lepreti, F.

2017-03-01

To evaluate the solar energetic proton (SEP) forecast model of Laurenza et al., here termed ESPERTA, we computed the input parameters (soft X-ray (SXR) fluence and ˜1 MHz radio fluence) for all ≥M2 SXR flares from 2006 to 2014. This database is outside the 1995-2005 interval on which ESPERTA was developed. To assess the difference in the general level of activity between these two intervals, we compared the occurrence frequencies of SXR flares and SEP events for the first six years of cycles 23 (1996 September-2002 September) and 24 (2008 December-2014 December). We found a reduction of SXR flares and SEP events of 40% and 46%, respectively, in the latter period. Moreover, the numbers of ≥M2 flares with high values of SXR and ˜1 MHz fluences (>0.1 J m-2 and >6 × 105 sfu × minute, respectively) are both reduced by ˜30%. A somewhat larger percentage decrease of these two parameters (˜40% versus ˜30%) is obtained for the 2006-2014 interval in comparison with 1995-2005. Despite these differences, ESPERTA performance was comparable for the two intervals. For the 2006-2014 interval, ESPERTA had a probability of detection (POD) of 59% (19/32) and a false alarm rate (FAR) of 30% (8/27), versus a POD = 63% (47/75) and an FAR = 42% (34/81) for the original 1995-2005 data set. In addition, for the 2006-2014 interval the median (average) warning time was estimated to be ˜2 hr (˜7 hr), versus ˜6 hr (˜9 hr), for the 1995-2005 data set.

Solar Activity from 2006 to 2014 and Short-term Forecasts of Solar Proton Events Using the ESPERTA Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alberti, T.; Lepreti, F.; Laurenza, M.

2017-03-20

To evaluate the solar energetic proton (SEP) forecast model of Laurenza et al., here termed ESPERTA, we computed the input parameters (soft X-ray (SXR) fluence and ∼1 MHz radio fluence) for all ≥M2 SXR flares from 2006 to 2014. This database is outside the 1995–2005 interval on which ESPERTA was developed. To assess the difference in the general level of activity between these two intervals, we compared the occurrence frequencies of SXR flares and SEP events for the first six years of cycles 23 (1996 September–2002 September) and 24 (2008 December–2014 December). We found a reduction of SXR flares andmore » SEP events of 40% and 46%, respectively, in the latter period. Moreover, the numbers of ≥M2 flares with high values of SXR and ∼1 MHz fluences (>0.1 J m{sup −2} and >6 × 10{sup 5} sfu × minute, respectively) are both reduced by ∼30%. A somewhat larger percentage decrease of these two parameters (∼40% versus ∼30%) is obtained for the 2006–2014 interval in comparison with 1995–2005. Despite these differences, ESPERTA performance was comparable for the two intervals. For the 2006–2014 interval, ESPERTA had a probability of detection (POD) of 59% (19/32) and a false alarm rate (FAR) of 30% (8/27), versus a POD = 63% (47/75) and an FAR = 42% (34/81) for the original 1995–2005 data set. In addition, for the 2006–2014 interval the median (average) warning time was estimated to be ∼2 hr (∼7 hr), versus ∼6 hr (∼9 hr), for the 1995–2005 data set.« less

A Data-Driven, Integrated Flare Model Based on Self-Organized Criticality

NASA Astrophysics Data System (ADS)

Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M.

2013-09-01

We interpret solar flares as events originating in solar active regions having reached the self-organized critical state, by alternatively using two versions of an "integrated flare model" - one static and one dynamic. In both versions the initial conditions are derived from observations aiming to investigate whether well-known scaling laws observed in the distribution functions of characteristic flare parameters are reproduced after the self-organized critical state has been reached. In the static model, we first apply a nonlinear force-free extrapolation that reconstructs the three-dimensional magnetic fields from two-dimensional vector magnetograms. We then locate magnetic discontinuities exceeding a threshold in the Laplacian of the magnetic field. These discontinuities are relaxed in local diffusion events, implemented in the form of cellular-automaton evolution rules. Subsequent loading and relaxation steps lead the system to self-organized criticality, after which the statistical properties of the simulated events are examined. In the dynamic version we deploy an enhanced driving mechanism, which utilizes the observed evolution of active regions, making use of sequential vector magnetograms. We first apply the static cellular automaton model to consecutive solar vector magnetograms until the self-organized critical state is reached. We then evolve the magnetic field inbetween these processed snapshots through spline interpolation, acting as a natural driver in the dynamic model. The identification of magnetically unstable sites as well as their relaxation follow the same rules as in the static model after each interpolation step. Subsequent interpolation/driving and relaxation steps cover all transitions until the end of the sequence. Physical requirements, such as the divergence-free condition for the magnetic field vector, are approximately satisfied in both versions of the model. We obtain robust power laws in the distribution functions of the modelled flaring events with scaling indices in good agreement with observations. We therefore conclude that well-known statistical properties of flares are reproduced after active regions reach self-organized criticality. The significant enhancement in both the static and the dynamic integrated flare models is that they initiate the simulation from observations, thus facilitating energy calculation in physical units. Especially in the dynamic version of the model, the driving of the system is based on observed, evolving vector magnetograms, allowing for the separation between MHD and kinetic timescales through the assignment of distinct MHD timestamps to each interpolation step.

INVESTIGATIONS ON FLARE STARS AND NEBULAE.

DTIC Science & Technology

The first part of the report deals with the searching of flare stars in the Pleiades and Praesepe clusters. 13 flares have been found on the... Pleiades and 2 on the Praesepe. Position and characteristics of the flare stars are given. The second part deals with the study of the Orion Nebula with

Foreign Language Analysis and Recognition (FLARe) Initial Progress

DTIC Science & Technology

2012-11-29

University Language Modeling ToolKit CoMMA Count Mediated Morphological Analysis CRUD Create, Read , Update & Delete CPAN Comprehensive Perl Archive...DATES COVERED (From - To) 1 October 2010 – 30 September 2012 4. TITLE AND SUBTITLE Foreign Language Analysis and Recognition (FLARe) Initial Progress...AFRL-RH-WP-TR-2012-0165 FOREIGN LANGUAGE ANALYSIS AND RECOGNITION (FLARE) INITIAL PROGRESS Brian M. Ore

Assessment of the Lower Urinary Tract Microbiota during Symptom Flare in Women with Urologic Chronic Pelvic Pain Syndrome: A MAPP Network Study.

PubMed

Nickel, J Curtis; Stephens, Alisa; Landis, J Richard; Mullins, Chris; van Bokhoven, Adrie; Lucia, M Scott; Ehrlich, Garth D

2016-02-01

We compared culture independent assessment of microbiota of the lower urinary tract in standard culture negative female patients with urological chronic pelvic pain syndrome who reported symptom flare vs those who did not report a flare. Initial stream (VB1) and midstream (VB2) urine specimens (233 patients with urological chronic pelvic pain syndrome) were analyzed with Ibis T-5000 Universal Biosensor system technology for comprehensive identification of microorganism species. Differences between flare and nonflare groups for presence or number of different species within a higher level group (richness) were examined by permutational multivariate analysis of variance and logistic regression. Overall 81 species (35 genera) were detected in VB1 and 73 (33) in VB2. Mean (SD) VB1 and VB2 species count per person was 2.6 (1.5) and 2.4 (1.5) for 86 flare cases and 2.8 (1.3) and 2.5 (1.5) for 127 nonflare cases, respectively. Overall the species composition did not significantly differ between flare and nonflare cases at any level (p=0.14 species, p=0.95 genus in VB1 and VB2, respectively) in multivariate analysis for richness. Univariate analysis, unadjusted as well as adjusted, confirmed a significantly greater prevalence of fungi (Candida and Saccharomyces) in the flare group (15.7%) compared to the nonflare group in VB2 (3.9%) (p=0.01). When adjusted for antibiotic use and menstrual phase, women who reported a flare remained more likely to have fungi present in VB2 specimens (OR 8.3, CI 1.7-39.4). Among women with urological chronic pelvic pain syndrome the prevalence of fungi (Candida and Saccharomyces sp.) was significantly greater in those who reported a flare compared to those who did not. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Assessment of the Lower Urinary Tract Microbiota during Symptom Flare in Women with Urologic Chronic Pelvic Pain Syndrome: A MAPP Network Study

PubMed Central

Nickel, J. Curtis; Stephens, Alisa; Landis, J. Richard; Mullins, Chris; van Bokhoven, Adrie; Lucia, M. Scott; Ehrlich, Garth D.

2016-01-01

Purpose We compared culture independent assessment of microbiota of the lower urinary tract in standard culture negative female patients with urological chronic pelvic pain syndrome who reported symptom flare vs those who did not report a flare. Materials and Methods Initial stream (VB1) and midstream (VB2) urine specimens (233 patients with urological chronic pelvic pain syndrome) were analyzed with Ibis T-5000 Universal Biosensor system technology for comprehensive identification of microorganism species. Differences between flare and nonflare groups for presence or number of different species within a higher level group (richness) were examined by permutational multivariate analysis of variance and logistic regression. Results Overall 81 species (35 genera) were detected in VB1 and 73 (33) in VB2. Mean (SD) VB1 and VB2 species count per person was 2.6 (1.5) and 2.4 (1.5) for 86 flare cases and 2.8 (1.3) and 2.5 (1.5) for 127 nonflare cases, respectively. Overall the species composition did not significantly differ between flare and nonflare cases at any level (p=0.14 species, p=0.95 genus in VB1 and VB2, respectively) in multivariate analysis for richness. Univariate analysis, unadjusted as well as adjusted, confirmed a significantly greater prevalence of fungi (Candida and Saccharomyces) in the flare group (15.7%) compared to the nonflare group in VB2 (3.9%) (p=0.01). When adjusted for antibiotic use and menstrual phase, women who reported a flare remained more likely to have fungi present in VB2 specimens (OR 8.3, CI 1.7–39.4). Conclusions Among women with urological chronic pelvic pain syndrome the prevalence of fungi (Candida and Saccharomyces sp.) was significantly greater in those who reported a flare compared to those who did not. PMID:26410734

Modelling Quasi-Periodic Pulsations in Solar and Stellar Flares

NASA Astrophysics Data System (ADS)

McLaughlin, J. A.; Nakariakov, V. M.; Dominique, M.; Jelínek, P.; Takasao, S.

2018-02-01

Solar flare emission is detected in all EM bands and variations in flux density of solar energetic particles. Often the EM radiation generated in solar and stellar flares shows a pronounced oscillatory pattern, with characteristic periods ranging from a fraction of a second to several minutes. These oscillations are referred to as quasi-periodic pulsations (QPPs), to emphasise that they often contain apparent amplitude and period modulation. We review the current understanding of quasi-periodic pulsations in solar and stellar flares. In particular, we focus on the possible physical mechanisms, with an emphasis on the underlying physics that generates the resultant range of periodicities. These physical mechanisms include MHD oscillations, self-oscillatory mechanisms, oscillatory reconnection/reconnection reversal, wave-driven reconnection, two loop coalescence, MHD flow over-stability, the equivalent LCR-contour mechanism, and thermal-dynamical cycles. We also provide a histogram of all QPP events published in the literature at this time. The occurrence of QPPs puts additional constraints on the interpretation and understanding of the fundamental processes operating in flares, e.g. magnetic energy liberation and particle acceleration. Therefore, a full understanding of QPPs is essential in order to work towards an integrated model of solar and stellar flares.

Equatorial ionospheric electrodynamics during solar flares

NASA Astrophysics Data System (ADS)

Zhang, Ruilong; Liu, Libo; Le, Huijun; Chen, Yiding

2017-05-01

Previous investigations on ionospheric responses to solar flares focused mainly on the photoionization caused by the increased X-rays and extreme ultraviolet irradiance. However, little attention was paid to the related electrodynamics. In this letter, we explored the equatorial electric field (EEF) and electrojet (EEJ) in the ionosphere at Jicamarca during flares from 1998 to 2008. It is verified that solar flares increase dayside eastward EEJ but decrease dayside eastward EEF, revealing a negative correlation between EEJ and EEF. The decreased EEF weakens the equatorial fountain effect and depresses the low-latitude electron density. During flares, the enhancement in the Cowling conductivity may modulate ionospheric dynamo and decrease the EEF. Besides, the decreased EEF is closely related to the enhanced ASY-H index that qualitatively reflects Region 2 field-aligned current (R2 FAC). We speculated that solar flares may also decrease EEF through enhancing R2 FAC that leads to an overshielding-like effect.

Photospheric Current Spikes And Their Possible Association With Flares - Results from an HMI Data Driven Model

NASA Astrophysics Data System (ADS)

Goodman, M. L.; Kwan, C.; Ayhan, B.; Eric, S. L.

2016-12-01

A data driven, near photospheric magnetohydrodynamic model predicts spikes in the horizontal current density, and associated resistive heating rate. The spikes appear as increases by orders of magnitude above background values in neutral line regions (NLRs) of active regions (ARs). The largest spikes typically occur a few hours to a few days prior to M or X flares. The spikes correspond to large vertical derivatives of the horizontal magnetic field. The model takes as input the photospheric magnetic field observed by the Helioseismic & Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO) satellite. This 2.5 D field is used to determine an analytic expression for a 3 D magnetic field, from which the current density, vector potential, and electric field are computed in every AR pixel for 14 ARs. The field is not assumed to be force-free. The spurious 6, 12, and 24 hour Doppler periods due to SDO orbital motion are filtered out of the time series of the HMI magnetic field for each pixel. The subset of spikes analyzed at the pixel level are found to occur on HMI and granulation scales of 1 arcsec and 12 minutes. Spikes are found in ARs with and without M or X flares, and outside as well as inside NLRs, but the largest spikes are localized in the NLRs of ARs with M or X flares. The energy to drive the heating associated with the largest current spikes comes from bulk flow kinetic energy, not the electromagnetic field, and the current density is highly non-force free. The results suggest that, in combination with the model, HMI is revealing strong, convection driven, non-force free heating events on granulation scales, and it is plausible these events are correlated with subsequent M or X flares. More and longer time series need to be analyzed to determine if such a correlation exists.

F-GAMMA program: Unification and physical interpretation of the radio spectra variability patterns in Fermi blazars and detection of radio jet emission from NLSY1 galaxies

NASA Astrophysics Data System (ADS)

Angelakis, E.

2012-01-01

The F-GAMMA program aims at understanding the physics at work in AGN via a multi-frequency monitoring approach. A number of roughly 65 Fermi-GST detectable blazars are being monitored monthly since January 2007 at radio wavelengths. The core program relies on the 100-m Effelsberg telescope operating at 8 frequencies between 2.6 and 43 GHz, the 30-m IRAM telescope observing at 86, 145 and 240 GHz and the APEX 12-m telescope at 345 GHz. For the targeted sources the LAT instrument onboard Fermi-GST provides gamma-ray light curves sampled daily. Here we discuss two recent findings: A). On the basis of their variability pattern, the observed quasi-simultaneous broad-band spectra can be classified to merely 5 classes. The variability for the first 4 is clearly dominated by spectral-evolution. Sources of the last class vary self-similarly with almost no apparent shift of the peak frequency. The former classes can be attributed to a two-component principal system made of a quiescent optically thin spectrum and a super-imposed flaring event. The later class must be interpreted in terms of a completely different mechanism. The apparent differences among the classes are explained in terms of a redshift modulus and an intrinsic-source/flare parameters modulus. Numerical simulations have shown that a shock-in-jet model can very well describe the observed behavior. It is concluded therefore that only two mechanisms seem to be producing variability. None of the almost 90 sources used for this study show a switch of class indicating that the variability mechanism is either (a) a finger-print of the source, or (b) remains stable on timescales far longer than the monitoring period of almost 4 years. B). Recently it has been disclosed that Narrow Line Seyfert 1 galaxies show gamma-ray emission. Within the F-GAMMA program radio jet emission has been detected from 3 such sources challenging the belief that jets are associated with elliptical galaxies. The recent findings in this area will be discussed.

Water Formation and Destruction by 'Super' X-ray Flares from a T-Tauri Star in a Protoplanetary Disk

NASA Astrophysics Data System (ADS)

Waggoner, Abygail R.; Cleeves, L. Ilsedore

2018-01-01

We present models of H2O chemistry is protoplanetary disks in the presence of 'super' X-ray flares emitted by a T-Tauri star. We examine the time-evolving chemistry of H2O at radial locations from 1 to 20 AU at various vertical heights from the mid-plane to the surface of the disk. We find the gas-phase H2O abundance can be enhanced in the surface (Z/R ≥ 0.3) by more than a factor of approximately 3 - 5 by strong flares, i.e., those that increase the ionization rate by a factor of 100. Dissociative recombination of H3O+ , H2O adsorption onto grain, and photolysis of H2O are found to be the three dominant processes leading to a change in H2O abundance. We find X-ray flares have predominantly short- term (days) effects on gaseous H2O abundance, but some regions show a long-term (for the duration of the test about 15 days) decrease in gaseous H2O due to adsorption onto grains, which results in an increase (up to 200%) in ice H2O in regions where ice H2O is < 10-9 abundance with respect to H atom. In regions where ice H2 O is > 10-8 abundance no are response in the ice is observed.Thanks to the National Science Foundation for funding this research as a part of the Smithsonian Astrophysical Observatory Research Experience for Undergraduates (SAO REU).

Analysis of a flare-director concept for an externally blown flap STOL aircraft

NASA Technical Reports Server (NTRS)

Middleton, D. B.

1974-01-01

A flare-director concept involving a thrust-required flare-guidance equation was developed and tested on a moving-base simulator. The equation gives a signal to command thrust as a linear function of the errors between the variables thrust, altitude, and altitude rate and corresponding values on a desired reference flare trajectory. During the simulator landing tests this signal drove either the horizontal command bar of the aircraft's flight director or a thrust-command dot on a head-up virtual-image display of a flare director. It was also used as the input to a simple autoflare system. An externally blown flap STOL (short take-off and landing) aircraft (with considerable stability and control augmentation) was modeled for the landing tests. The pilots considered the flare director a valuable guide for executing a proper flare-thrust program under instrument-landing conditions, but were reluctant to make any use of the head-up display when they were performing the landings visually.

Closed coronal structures. V - Gasdynamic models of flaring loops and comparison with SMM observations

NASA Technical Reports Server (NTRS)

Peres, G.; Serio, S.; Vaiana, G.; Acton, L.; Leibacher, J.; Rosner, R.; Pallavicini, R.

1983-01-01

A time-dependent one-dimensional code incorporating energy, momentum and mass conservation equations, and taking the entire solar atmospheric structure into account, is used to investigate the hydrodynamic response of confined magnetic structures to strong heating perturbations. Model calculation results are compared with flare observations which include the light curves of spectral lines formed over a wide range of coronal flare temperatures, as well as determinations of Doppler shifts for the high temperature plasma. It is shown that the numerical simulation predictions are in good overall agreement with the observed flare coronal plasma evolution, correctly reproducing the temporal profile of X-ray spectral lines and their relative intensities. The predicted upflow velocities support the interpretation of the blueshifts as due to evaporation of chromospheric material.

A qualitative interpretation of 7 August 1972 impulsive phase flare H alpha line profiles

NASA Technical Reports Server (NTRS)

Canfield, R. C.

1982-01-01

The considered investigation shows that existing models of the formation of the H-alpha line during flares appear to provide clear qualitative evidence that heating of the H-alpha forming regions of the flare chromosphere in the bright H-alpha kernels observed during the impulsive phase of solar flares is not due primarily to heating by Coulomb collisions of a power-law distribution of 10-100 keV electrons with chromospheric material. It appears rather that some shorter-range process, involving possibly conduction or optically thick radiative transfer, is favored. Such a conclusion is clearly relevant to collisionless confinement modelling. However, much work remains to be done before there will be a basis for quantitatively testing the consistency of the considered picture with chromospheric diagnostics.

46 CFR 160.036-2 - Type.

Code of Federal Regulations, 2012 CFR

2012-10-01

... APPROVAL LIFESAVING EQUIPMENT Hand-Held Rocket-Propelled Parachute Red Flare Distress Signals § 160.036-2 Type. (a) Handheld rocket-propelled parachute red flare distress signals specified by this subpart... fired from the hand to provide a rocket-propelled parachute red flare distress signal. (b) [Reserved] ...

46 CFR 160.036-2 - Type.

Code of Federal Regulations, 2014 CFR

2014-10-01

... APPROVAL LIFESAVING EQUIPMENT Hand-Held Rocket-Propelled Parachute Red Flare Distress Signals § 160.036-2 Type. (a) Handheld rocket-propelled parachute red flare distress signals specified by this subpart... fired from the hand to provide a rocket-propelled parachute red flare distress signal. (b) [Reserved] ...

46 CFR 160.036-2 - Type.

Code of Federal Regulations, 2010 CFR

2010-10-01

... APPROVAL LIFESAVING EQUIPMENT Hand-Held Rocket-Propelled Parachute Red Flare Distress Signals § 160.036-2 Type. (a) Handheld rocket-propelled parachute red flare distress signals specified by this subpart... fired from the hand to provide a rocket-propelled parachute red flare distress signal. (b) [Reserved] ...

46 CFR 160.036-2 - Type.

Code of Federal Regulations, 2011 CFR

2011-10-01

... APPROVAL LIFESAVING EQUIPMENT Hand-Held Rocket-Propelled Parachute Red Flare Distress Signals § 160.036-2 Type. (a) Handheld rocket-propelled parachute red flare distress signals specified by this subpart... fired from the hand to provide a rocket-propelled parachute red flare distress signal. (b) [Reserved] ...

46 CFR 160.036-2 - Type.

Code of Federal Regulations, 2013 CFR

2013-10-01

... APPROVAL LIFESAVING EQUIPMENT Hand-Held Rocket-Propelled Parachute Red Flare Distress Signals § 160.036-2 Type. (a) Handheld rocket-propelled parachute red flare distress signals specified by this subpart... fired from the hand to provide a rocket-propelled parachute red flare distress signal. (b) [Reserved] ...

Temporal and spectral characteristics of solar flare hard X-ray emission

NASA Technical Reports Server (NTRS)

Dennis, B. R.; Kiplinger, A. L.; Orwig, L. E.; Frost, K. J.

1985-01-01

Solar Maximum Mission observations of three flares that impose stringent constraints on physical models of the hard X-ray production during the impulsive phase are presented. Hard X-ray imaging observations of the flares on 1980 November 5 at 22:33 UT show two patches in the 16 to 30 keV images that are separated by 70,000 km and that brighten simultaneously to within 5 s. Observations to O V from one of the footprints show simultaneity of the brightening in this transition zone line and in the total hard X-ray flux to within a second or two. These results suggest but do not require the existence of electron beams in this flare. The rapid fluctuations of the hard X-ray flux within some flares on the time scales of 1 s also provide evidence for electron beams and limits on the time scale of the energy release mechanism. Observations of a flare on 1980 June 6 at 22:34 UT show variations in the 28 keV X-ray counting rate from one 20 ms interval to the next over a period of 10 s. The hard X-ray spectral variations measured with 128 ms time resolution for one 0.5 s spike during this flare are consistent with the predictions of thick-target non-thermal beam model.

Discovery of 1-5 Hz Flaring at High Luminosity in SAX J1808.4-3658

NASA Astrophysics Data System (ADS)

Bult, Peter; van der Klis, Michiel

2014-07-01

We report the discovery of a 1-5 Hz X-ray flaring phenomenon observed at >30 mCrab near peak luminosity in the 2008 and 2011 outbursts of the accreting millisecond X-ray pulsar SAX J1808.4-3658 in observations with the Rossi X-ray Timing Explorer. In each of the two outbursts this high luminosity flaring is seen for ~3 continuous days and switches on and off on a timescale of 1-2 hr. The flaring can be seen directly in the light curve, where it shows sharp spikes of emission at quasi-regular separation. In the power spectrum it produces a broad noise component, which peaks at 1-5 Hz. The total 0.05-10 Hz variability has a fractional rms amplitude of 20%-45%, well in excess of the 8%-12% rms broadband noise usually seen in power spectra of SAX J1808.4-3658. We perform a detailed timing analysis of the flaring and study its relation to the 401 Hz pulsations. We find that the pulse amplitude varies proportionally with source flux through all phases of the flaring, indicating that the flaring is likely due to mass density variations created at or outside the magnetospheric boundary. We suggest that this 1-5 Hz flaring is a high mass accretion rate version of the 0.5-2 Hz flaring which is known to occur at low luminosity (<13 mCrab), late in the tail of outbursts of SAX J1808.4-3658. We propose the dead-disk instability, previously suggested as the mechanism for the 0.5-2 Hz flaring, as a likely mechanism for the high luminosity flaring reported here.

The X-ray Spectral Evolution of eta Carinae as Seen by ASCA

NASA Technical Reports Server (NTRS)

Corcoran, M. F.; Fredericks, A. C.; Petre, R.; Swank, J. H.; Drake, S. A.; White, Nicholas E. (Technical Monitor)

2000-01-01

Using data from the ASCA X-ray observatory, we examine the variations in the X-ray spectrum of the supermassive star nu Carinae with an unprecedented combination of spatial and spectral resolution. We include data taken during the recent X-ray eclipse in 1997-1998, after recovery from the eclipse, and during and after an X-ray flare. We show that the eclipse variation in the X-ray spectrum is apparently confined to a decrease in the emission measure of the source. We compare our results with a simple colliding wind binary model and find that the observed spectral variations are only consistent, with the binary model if there is significant high-temperature emission far from the star and/or a substantial change in the temperature distribution of the hot plasma. If contamination in the 2-10 keV band is important, the observed eclipse spectrum requires an absorbing column in excess of 10(exp 24)/sq cm for consistency with the binary model, which may indicate an increase in the first derivative of M from nu Carinae near the time of periastron passage. The flare spectra are consistent with the variability seen in nearly simultaneous RXTE observations and thus confirm that nu Carinae itself is the source of the flare emission. The variation in the spectrum during the flare seems confined to a change in the source emission measure. By comparing 2 observations obtained at the same phase in different X-ray cycles, we find that the current, X-ray brightness of the source is slightly higher than the brightness of the source during the last cycle perhaps indicative of a long-term increase in the first derivative of M, not associated with the X-ray cycle.

Preliminary criteria for global flares in childhood-onset systemic lupus erythematosus.

PubMed

Brunner, Hermine I; Mina, Rina; Pilkington, Clarissa; Beresford, Michael W; Reiff, Andreas; Levy, Deborah M; Tucker, Lori B; Eberhard, B Anne; Ravelli, Angelo; Schanberg, Laura E; Saad-Magalhaes, Claudia; Higgins, Gloria C; Onel, Karen; Singer, Nora G; von Scheven, Emily; Itert, Lukasz; Klein-Gitelman, Marisa S; Punaro, Marilynn; Ying, Jun; Giannini, Edward H

2011-09-01

To develop widely acceptable preliminary criteria of global flare for childhood-onset systemic lupus erythematosus (cSLE). Pediatric rheumatologists (n = 138) rated a total of 358 unique patient profiles with information about the cSLE flare descriptors from 2 consecutive visits: patient global assessment of well-being, physician global assessment of disease activity (MD-global), health-related quality of life, anti-double-stranded DNA antibodies, disease activity index scores, protein:creatinine (P:C) ratio, complement levels, and erythrocyte sedimentation rate (ESR). Based on 2,996 rater responses about the course of cSLE (baseline versus followup), the accuracy (sensitivity, specificity, and area under the receiver operating characteristic curve) of candidate flare criteria was assessed. An international consensus conference was held to rank these candidate flare criteria as per the American College of Rheumatology recommendations for the development and validation of criteria sets. The highest-ranked candidate criteria considered absolute changes (Δ) of the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) or British Isles Lupus Assessment Group (BILAG), MD-global, P:C ratio, and ESR; flare scores can be calculated (0.5 × ΔSLEDAI + 0.45 × ΔP:C ratio + 0.5 × ΔMD-global + 0.02 × ΔESR), where values of ≥1.04 are reflective of a flare. Similarly, BILAG-based flare scores (0.4 × ΔBILAG + 0.65 × ΔP:C ratio + 0.5 × ΔMD-global + 0.02 × ΔESR) of ≥1.15 were diagnostic of a flare. Flare scores increased with flare severity. Consensus has been reached on preliminary criteria for global flares in cSLE. Further validation studies are needed to confirm the usefulness of the cSLE flare criteria in research and for clinical care. Copyright © 2011 by the American College of Rheumatology.

Flare research with the NASA/MSFC vector magnetograph - Observed characteristics of sheared magnetic fields that produce flares

NASA Technical Reports Server (NTRS)

Moore, R. L.; Hagyard, M. J.; Davis, J. M.

1987-01-01

The present MSFC Vector Magnetograph has sufficient spatial resolution (2.7 arcsec pixels) and sensitivity to the transverse field (the noise level is about 100 gauss) to map the transverse field in active regions accurately enough to reveal key aspects of the sheared magnetic fields commonly found at flare sites. From the measured shear angle along the polarity inversion line in sites that flared and in other shear sites that didn't flare, evidence is found that a sufficient condition for a flare to occur in 1000 gauss fields in and near sunspots is that both: (1) the maximum shear angle exceed 85 degrees; and (2) the extent of strong shear (shear angle of greater than 80 degrees) exceed 10,000 km.

Anthropogenic activities impact on atmospheric environmental quality in a gas-flaring community: application of fuzzy logic modelling concept.

PubMed

Akintola, Olayiwola Akin; Sangodoyin, Abimbola Yisau; Agunbiade, Foluso Oyedotun

2018-05-24

We present a modelling concept for evaluating the impacts of anthropogenic activities suspected to be from gas flaring on the quality of the atmosphere using domestic roof-harvested rainwater (DRHRW) as indicator. We analysed seven metals (Cu, Cd, Pb, Zn, Fe, Ca, and Mg) and six water quality parameters (acidity, PO 4 3- , SO 4 2- , NO 3 - , Cl - , and pH). These were used as input parameters in 12 sampling points from gas-flaring environments (Port Harcourt, Nigeria) using Ibadan as reference. We formulated the results of these input parameters into membership function fuzzy matrices based on four degrees of impact: extremely high, high, medium, and low, using regulatory limits as criteria. We generated indices that classified the degree of anthropogenic activity impact on the sites from the product membership function matrices and weight matrices, with investigated (gas-flaring) environment as between medium and high impact compared to those from reference (residential) environment that was classified as between low and medium impact. Major contaminants of concern found in the harvested rainwater were Pb and Cd. There is also the urgent need to stop gas-flaring activities in Port Harcourt area in particular and Niger Delta region of Nigeria in general, so as to minimise the untold health hazard that people living in the area are currently faced with. The fuzzy methodology presented has also indicated that the water cannot safely support potable uses and should not be consumed without purification due to the impact of anthropogenic activities in the area but may be useful for other domestic purposes.