PERVASIVE FAINT Fe XIX EMISSION FROM A SOLAR ACTIVE REGION OBSERVED WITH EUNIS-13: EVIDENCE FOR NANOFLARE HEATING

Brosius, J. W.; Daw, A. N.; Rabin, D. M.

doi:10.1088/0004-637x/790/2/112

Cited by 82 publications

(78 citation statements)

References 60 publications

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“…This means that observations will see more high temperature plasma than is currently predicted. One approach for finding nanoflares in the solar corona is to detect plasma emitted from charge states with high formation temperatures of ∼10 MK plasma (Reale et al 2009;Schmelz et al 2009;Brosius et al 2014). Our findings suggest that it is somewhat easier to form such charge states than current models predict.…”

Section: Application To Nanoflaresmentioning

confidence: 71%

“…Recently, there has been significant work on predicting the spectroscopic signatures of nanoflares (e.g., Bradshaw & Mason 2003;Cargill & Klimchuk 2004;Reale & Orlando 2008;Bradshaw & Klimchuk 2011). Nanoflares are predicted to heat the plasma to ∼10 7 K (Schmelz et al 2009;Reale et al 2009;Brosius et al 2014). However, simulations predict such hot plasma is difficult to detect because the ionization balance needs time to adjust to the high temperature (Bradshaw & Klimchuk 2011).…”

Section: Application To Nanoflaresmentioning

confidence: 99%

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Influence of Electron-Impact Multiple Ionization on Equilibrium and Dynamic Charge State Distributions: A Case Study Using Iron

Hahn

Savin

2015

ApJ

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We describe the influence of electron-impact multiple ionization (EIMI) on the ionization balance of collisionally ionized plasmas. Previous ionization balance calculations have largely neglected EIMI. Here, EIMI cross-section data are incorporated into calculations of both equilibrium and non-equilibrium charge-state distributions (CSDs). For equilibrium CSDs, we find that EIMI has only a small effect and can usually be ignored. However, for nonequilibrium plasmas the influence of EIMI can be important. In particular, we find that for plasmas in which the temperature oscillates there are significant differences in the CSD when including versus neglecting EIMI. These results have implications for modeling and spectroscopy of impulsively heated plasmas, such as nanoflare heating of the solar corona.

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Section: Application To Nanoflaresmentioning

confidence: 71%

Section: Application To Nanoflaresmentioning

confidence: 99%

Influence of Electron-Impact Multiple Ionization on Equilibrium and Dynamic Charge State Distributions: A Case Study Using Iron

Hahn

Savin

2015

ApJ

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“…While many workers (Reale et al 2009;Schmelz et al 2009Schmelz et al , 2015Miceli et al 2012;Del Zanna & Mason 2014;Petralia et al 2014) have claimed evidence of this hot, faint component of the emission measure, poor spectral resolution (Testa et al 2011;Winebarger et al 2012) and non-equilibrium ionization (NEI; Bradshaw & Cargill 2006;Reale & Orlando 2008) may make a positive detection of nanoflare heating difficult. However, Brosius et al (2014) used observations from the EUNIS-13 sounding rocket to identify relatively faint emission from Fe XIX in a non-flaring AR, suggesting temperatures of ∼8.9 MK.…”

Section: Introductionmentioning

confidence: 99%

Inference of Heating Properties From “Hot” Non-Flaring Plasmas in Active Region Cores. Ii. Nanoflare Trains

Barnes

Cargill

Bradshaw

2016

ApJ

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Despite its prediction over two decades ago, the detection of faint, high-temperature ("hot") emission due to nanoflare heating in non-flaring active region cores has proved challenging. Using an efficient two-fluid hydrodynamic model, this paper investigates the properties of the emission expected from repeating nanoflares (a nanoflare train) of varying frequency as well as the separate heating of electrons and ions. If the emission measure distribution (EM(T)) peaks at T = T m , we find that EM(T m ) is independent of details of the nanoflare train, and EM(T) above and below T m reflects different aspects of the heating. Below T m , the main influence is the relationship of the waiting time between successive nanoflares to the nanoflare energy. Above T m , power-law nanoflare distributions lead to an extensive plasma population not present in a mono-energetic train. Furthermore, in some cases, characteristic features are present in EM(T). Such details may be detectable given adequate spectral resolution and a good knowledge of the relevant atomic physics. In the absence of such resolution we propose some metrics that can be used to infer the presence of "hot" plasma.

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“…The 30 parallel slits allow good spatial coverage of the Hα spectra, which made it easy to determine which part of the flare was most energetic, and where the filaments were activated in the early stages. Instruments for rocket flights have been developed over the years to produce high time resolution spectra, and having a co-alignment slot "dumb-bell" (e.g., Brosius et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Measuring Velocities in the Early Stage of an Eruption: Using “Overlappogram” Data from Hinode EIS

Harra¹,

Hara

Doschek

et al. 2017

ApJ

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In order to understand the onset phase of a solar eruption, plasma parameter measurements in the early phases are key to constraining models. There are two current instrument types that allow us to make such measurements: narrow-band imagers and spectrometers. In the former case, even narrow-band filters contain multiple emission lines, creating some temperature confusion. With imagers, however, rapid cadences are achievable and the field of view can be large. Velocities of the erupting structures can be measured by feature tracking. In the spectrometer case, slit spectrometers can provide spectrally pure images by "rastering" the slit to build up an image. This method provides limited temporal resolution, but the plasma parameters can be accurately measured, including velocities along the line of sight. Both methods have benefits and are often used in tandem. In this paper we demonstrate for the first time that data from the wide slot on the Hinode EUV Imaging Spectrometer, along with imaging data from AIA, can be used to deconvolve velocity information at the start of an eruption, providing line-of-sight velocities across an extended field of view. Using He II 256 Å slot data at flare onset, we observe broadening or shift(s) of the emission line of up to ±280 km s −1 . These are seen at different locations-the redshifted plasma is seen where the hard X-ray source is later seen (energy deposition site). In addition, blueshifted plasma shows the very early onset of the fast rise of the filament.

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PERVASIVE FAINT Fe XIX EMISSION FROM A SOLAR ACTIVE REGION OBSERVED WITH EUNIS-13: EVIDENCE FOR NANOFLARE HEATING

Cited by 82 publications

References 60 publications

Influence of Electron-Impact Multiple Ionization on Equilibrium and Dynamic Charge State Distributions: A Case Study Using Iron

Influence of Electron-Impact Multiple Ionization on Equilibrium and Dynamic Charge State Distributions: A Case Study Using Iron

Inference of Heating Properties From “Hot” Non-Flaring Plasmas in Active Region Cores. Ii. Nanoflare Trains

Measuring Velocities in the Early Stage of an Eruption: Using “Overlappogram” Data from Hinode EIS

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