Intensity Conserving Spectral Fitting

Klimchuk, J. A.; Patsourakos, S.; Tripathi, Durgesh

doi:10.1007/s11207-015-0827-4

Cited by 13 publications

(14 citation statements)

References 25 publications

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“…We therefore take an additional step in order to measure the line center position as accurately as possible. We apply a procedure called Intensity Conserving Spectral Fitting (ICSF; Klimchuk et al 2016), which accounts for the finite size of the spectral bins. A spectrometer measures the average intensity over a bin, and this intensity is typically assigned to the wavelength position at bin center.…”

Section: Data Analysis and Resultsmentioning

confidence: 99%

On Doppler Shift and Its Center-to-limb Variation in Active Regions in the Transition Region

Ghosh

Klimchuk

Tripathi

2019

ApJ

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A comprehensive understanding of the structure of Doppler motions in transition region including the center-to-limb variation and its relationship with the magnetic field structure is vital for the understanding of mass and energy transfer in the solar atmosphere. In this paper, we have performed such a study in an active region using the Si IV 1394Å emission line recorded by the Interface Region Imaging Spectrograph (IRIS) and the line-of-sight photospheric magnetic field obtained by the Helioseismic and Magnetic Imager (HMI) on-board the Solar Dynamics Observatory (SDO). The active region has two opposite polarity strong field regions separated by a weak field corridor, which widened as the active region evolved. On average the strong field regions (corridor) show(s) redshifts of 5-10 (3-9) km s −1 (depending on the date of observation). There is, however, a narrow lane in the middle of the corridor with near-zero Doppler shifts at all disk positions, suggesting that any flows there are very slow. The Doppler velocity distributions in the corridor seem to have two components-a low velocity component centered near 0 km/s and a high velocity component centered near 10 km s −1 . The high velocity component is similar to the velocity distributions in the strong field regions, which have just one component. Both exhibit a small center-to limb variation and seem to come from the same population of flows. To explain these results, we suggest that the emission from the lower transition region comes primarily from warm type II spicules, and we introduce the idea of a 'chromospheric wall'-associated with classical cold spicules-to account for a diminished center-to-limb variation.

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Section: Data Analysis and Resultsmentioning

confidence: 99%

On Doppler Shift and Its Center-to-limb Variation in Active Regions in the Transition Region

Ghosh

Klimchuk

Tripathi

2019

ApJ

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“…In the bottom row of Figure 2 we present the RB asymmetries calculated following the same approach as used by De Pontieu et al (2009) which interpolates in the wavelength axis using spline. We tested the Klimchuk et al (2016) interpolation method (not shown here) and the calculated RB asymmetries do not differ from the one using spline interpolation shown in Figure 2.…”

Section: Observables and Constraintsmentioning

confidence: 99%

Impact of Type II Spicules in the Corona: Simulations and Synthetic Observables

Martínez-Sykora

Pontieu

Moortel

et al. 2018

ApJ

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The role of type II spicules in the corona has been a much debated topic in recent years. This paper aims to shed light on the impact of type II spicules in the corona using novel 2.5D radiative MHD simulations including ion-neutral interaction effects with the Bifrost code. We find that the formation of simulated type II spicules, driven by the release of magnetic tension, impacts the corona in various manners. Associated with the formation of spicules, the corona exhibits 1) magneto-acoustic shocks and flows which supply mass to coronal loops, and 2) transversal magnetic waves and electric currents that propagate at Alfvén speeds. The transversal waves and electric currents, generated by the spicule's driver and lasting for many minutes, are dissipated and heat the associated loop. These complex interactions in the corona can be connected with blue shifted secondary components in coronal spectral lines (Red-Blue asymmetries) observed with Hinode/EIS and SOHO/SUMER, as well as the EUV counterpart of type II spicules and propagating coronal disturbances (PCDs) observed with the 171Å and 193Å SDO/AIA channels.

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“…In the first and second columns of Table 1, we provide the date and µ-value of each observation, where µ is defined as the cosine of the angle between the surface normal and the LOS to the observer of the centre of the FOV (Thompson 2006) 1 We have used Level-2 IRIS raster data in which all instrumental effects such as flat-fielding, dark currents, offsets and thermal orbital variations have been accounted for, so as to make it suitable for scientific analysis 2 . Further, we apply the procedure called the Intensity Conserving Spectral Fitting (ICSF; Klimchuk et al 2016) on the original line profiles, as explained in Paper I. We use single Gaussian fitting routines 3 on the resultant spectral lines, provided in Solarsoft (Freeland & Handy 1998) for analysing the data.…”

Section: Observationsmentioning

confidence: 99%

Non-thermal Velocity in the Transition Region of Active Regions and its Centre-to-Limb Variation

Ghosh,

Tripathi,

Klimchuk

2021

Preprint

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We derive the non-thermal velocities (NTVs) in the transition region of an active region using the Si IV 1393.78 Å line observed by the Interface Region Imaging Spectrograph (IRIS) and compare them with the line-of-sight photospheric magnetic fields obtained by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The active region consists of two strong field regions with opposite polarity, separated by a weak field corridor, that widened as the active region evolved. The means of the NTV distributions in strong-field regions (weak field corridors) range between ∼18-20 (16-18) km s −1 , albeit the NTV maps show much larger range. In addition, we identify a narrow lane in the middle of the corridor with significantly reduced NTV. The NTVs do not show a strong center-to-limb variation, albeit somewhat larger values near the disk center. The NTVs are well correlated with redshifts as well as line intensities. The results obtained here and those presented in our companion paper on Doppler shifts suggest two populations of plasma in the active region emitting in Si IV. The first population exists in the strong field regions and extends partway into the weak field corridor between them. We attribute this plasma to spicules heated to ∼0.1 MK (often called type II spicules). They have a range of inclinations relative to vertical. The second population exists in the center of the corridor, is relatively faint, and has smaller velocities, likely horizontal. These results provide further insights into the heating of the transition region.

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Intensity Conserving Spectral Fitting

Cited by 13 publications

References 25 publications

On Doppler Shift and Its Center-to-limb Variation in Active Regions in the Transition Region

On Doppler Shift and Its Center-to-limb Variation in Active Regions in the Transition Region

Impact of Type II Spicules in the Corona: Simulations and Synthetic Observables

Non-thermal Velocity in the Transition Region of Active Regions and its Centre-to-Limb Variation

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