Photometric and Thermal Cross-calibration of Solar EUV Instruments

Boerner, P.; Testa, Paola; Warren, H. P.; Weber, Mark; Schrijver, Carolus J.

doi:10.1007/s11207-013-0452-z

Cited by 101 publications

(120 citation statements)

References 34 publications

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“…The NASA Extreme Ultraviolet Explorer (EUVE) mission observed the 93.9Å Fe XVIII line in a large number of active stars, but with insufficient signal-to-noise to identify cooler lines at neighbouring wavelengths (e.g., Mewe et al 1995;Sanz-Forcada et al 2003). Such cool (e.g., Fe X) lines were known to lie near the Fe XVIII line when SDO was launched ), but CHIANTI did not reproduce the spectrum completely (Aschwanden & Boerner 2011;Reale et al 2011;Testa et al 2012b;Aschwanden et al 2013), although it is believed that the Fe XVIII 93.9Å line itself is correctly represented in CHIANTI (Warren et al 2012;Del Zanna 2013 identified an Fe XIV line that is blended with Fe XVIII in the EVE spectra, and empirical corrections have been made to the AIA temperature response functions (Del Zanna 2013;Boerner et al 2014). These complications are often avoidable in flare studies where the pre-flare emission can be subtracted (e.g.…”

Section: Appendixmentioning

confidence: 99%

The Slowly Varying Corona. I. Daily Differential Emission Measure Distributions Derived from EVE Spectra

Schonfeld

White

Hock-Mysliwiec

et al. 2017

ApJ

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Daily differential emission measure (DEM) distributions of the solar corona are derived from spectra obtained by the Extreme-ultraviolet Variability Experiment (EVE) over a 4-year period starting in 2010 near solar minimum and continuing through the maximum of solar cycle 24. The DEMs are calculated using six strong emission features dominated by Fe lines of charge states VIII, IX, XI, XII, XIV, and XVI that sample the non-flaring coronal temperature range 0.3-5 MK. A proxy for the non-Fe XVIII emission in the wavelength band around the 93.9Å line is demonstrated. There is little variability in the cool component of the corona (T < 1.3 MK) over the four years, suggesting that the quiet-Sun corona does not respond strongly to the solar cycle, whereas the hotter component (T > 2.0 MK) varies by more than an order of magnitude. A discontinuity in the behavior of coronal diagnostics in 2011 February-March, around the time of the first X-class flare of cycle 24, suggests fundamentally different behavior in the corona under solar minimum and maximum conditions. This global state transition occurs over a period of several months. The DEMs are used to estimate the thermal energy of the visible solar corona (of order 10 31 erg), its radiative energy loss rate (2.5-8 ×10 27 erg s −1 ), and the corresponding energy turnover timescale (about an hour). The uncertainties associated with the DEMs and these derived values are mostly due to the coronal Fe abundance and density and the CHIANTI atomic line database.

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Section: Appendixmentioning

confidence: 99%

The Slowly Varying Corona. I. Daily Differential Emission Measure Distributions Derived from EVE Spectra

Schonfeld

White

Hock-Mysliwiec

et al. 2017

ApJ

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“…The AIA 94 Å response function has two maxima: a "hot" component at T ≈ 10 6.85 K, due to the Fe xviii ion, and a "warm" component at T ≈ 10 6.2 K (Boerner et al 2014). Reale et al (2011) extract the hot 94 Å signal by subtracting a fraction of the 171 Å signal that is used to model the "warm" component (which these authors label "cool").…”

Section: Datamentioning

confidence: 99%

HEATING MECHANISMS FOR INTERMITTENT LOOPS IN ACTIVE REGION CORES FROM AIA/SDOEUV OBSERVATIONS

Cadavid

Lawrence

Christian

et al. 2014

ApJ

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We investigate intensity variations and energy deposition in five coronal loops in active region cores. These were selected for their strong variability in the AIA/SDO 94 Å intensity channel. We isolate the hot Fe xviii and Fe xxi components of the 94 Å and 131 Å by modeling and subtracting the "warm" contributions to the emission. HMI/SDO data allow us to focus on "inter-moss" regions in the loops. The detailed evolution of the inter-moss intensity time series reveals loops that are impulsively heated in a mode compatible with a nanoflare storm, with a spike in the hot 131 Å signals leading and the other five EUV emission channels following in progressive cooling order. A sharp increase in electron temperature tends to follow closely after the hot 131 Å signal confirming the impulsive nature of the process. A cooler process of growing emission measure follows more slowly. The Fourier power spectra of the hot 131 Å signals, when averaged over the five loops, present three scaling regimes with break frequencies near 0.1 min −1 and 0.7 min −1 . The low frequency regime corresponds to 1/f noise; the intermediate indicates a persistent scaling process and the high frequencies show white noise. Very similar results are found for the energy dissipation in a 2D "hybrid" shell model of loop magneto-turbulence, based on reduced magnetohydrodynamics, that is compatible with nanoflare statistics. We suggest that such turbulent dissipation is the energy source for our loops.

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“…Since the NoRH are normalized to 10 4 K, the quiet Sun oscillates around it. As reported by Boerner et al (2014), the AIA responses have degraded over the years, most notably in the 304 Å channel. Using the SolarSoft routine aia_get_response.pro, one can see the degradation of the AIA responses over time with respect to the EUV Variability Experiment (EVE) on board the SDO.…”

Section: The Quiet Sunmentioning

confidence: 62%

Comparison of solar radio and extreme ultraviolet synoptic limb charts during the present solar maximum

Silva¹,

Selhorst²,

Simões³

et al. 2016

A&A

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Aims. The present solar cycle is particular in many aspects: it had a delayed rising phase, it is the weakest of the last 100 yrs, and it presents two peaks separated by more than one year. To understand the impact of these characteristics on the solar chromosphere and coronal dynamics, images from a wide wavelength range are needed. In this work we use the 17 GHz radio continuum, which is formed in the upper chromosphere and the extreme ultraviolet (EUV) lines 304 and 171 Å, that come from the transition region (He ii, T ∼ 6−8 × 10 4 K) and the corona (Fe IX, X, T ∼ 10 6 K), respectively. We extend upon a previous similar analysis, and compare the mean equatorial and polar brightening behavior at radio and EUV wavelengths during the maximum of the present solar cycle, covering the period between 2010 and 2015. Methods. We analyze daily images at 304 and 171 Å obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The 17 GHz maps were obtained by the Nobeyama Radioheliograph (NoRH). To construct synoptic limb charts, we calculated the mean emission of delimited limb areas with 100 wide and angular separation of 5 • . Results. At the equatorial region, the results show a hemispheric asymmetry of the solar activity. The northern hemisphere dominance is coincident with the first sunspot number peak, whereas the second peak occurs concurrently with the increase in the activity at the south. The polar emission reflects the presence of coronal holes at both EUV wavelengths, moreover, the 17 GHz polar brightenings can be associated with the coronal holes. Until 2013, both EUV coronal holes and radio polar brightenings were more predominant at the south pole. Since then they have not been apparent in the north, but thus appear in the beginning of 2015 in the south as observed in the synoptic charts. Conclusions. This work strengthens the association between coronal holes and the 17 GHz polar brightenings as it is evident in the synoptic limb charts in agreement with previous case study papers. The enhancement of the radio brightness in coronal holes is explained by the presence of bright patches closely associated with the presence of intense unipolar magnetic fields. However, observations with better spatial resolution and also at different radio wavelengths will be necessary to fully understand the physical mechanisms that link these features.

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Photometric and Thermal Cross-calibration of Solar EUV Instruments

Cited by 101 publications

References 34 publications

The Slowly Varying Corona. I. Daily Differential Emission Measure Distributions Derived from EVE Spectra

The Slowly Varying Corona. I. Daily Differential Emission Measure Distributions Derived from EVE Spectra

HEATING MECHANISMS FOR INTERMITTENT LOOPS IN ACTIVE REGION CORES FROM AIA/SDOEUV OBSERVATIONS

Comparison of solar radio and extreme ultraviolet synoptic limb charts during the present solar maximum

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