Extreme Ultraviolet Variability Experiment (EVE) Multiple EUV Grating Spectrographs (MEGS): Radiometric Calibrations and Results

Hock, R. A.; Chamberlin, Phillip C.; Woods, Thomas N.; Crotser, David A.; Eparvier, F.; Woodraska, D.; Woods, Evanne

doi:10.1007/978-1-4614-3673-7_8

Cited by 10 publications

(17 citation statements)

References 20 publications

(13 reference statements)

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“…After the 2010 launch of the Solar Dynamics Observatory (SDO), Version 3 of the LASP composite was created which filled gaps in the SORCE SOLSTICE Lyman α observations with Lyman α measurements from the Extreme Ultraviolet Variability Experiment (EVE) (Woods et al, ) Multiple Extreme ultraviolet Grating Spectrographs P (Hock et al, ) instrument. In the Version 3 composite, TIMED SEE, SORCE SOLSTICE, and SDO EVE data are all scaled to UARS SOLSTICE and are not smoothed.…”

Section: Previous Lasp Lyman α Composites (Versions 1–3)mentioning

confidence: 99%

An Improved Lyman‐Alpha Composite

Machol

Snow

Woodraska

et al. 2019

Earth and Space Science

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The hydrogen Lyman-alpha (Lyman α) line at 121.56 nm is the strongest solar vacuum ultraviolet emission line. Especially because of the impacts on planetary atmospheres, long-term data sets of Lyman α are important for understanding solar and atmospheric processes. A revised composite data set of daily Lyman α values beginning in 1947 is constructed using measurements of Lyman α from Atmospheric Explorer E, Solar Mesospheric Explorer, Upper Atmosphere Research Satellite, and Solar Radiation and Climate Experiment. Gaps are filled using proxy models based on the Magnesium II index and the 10.7-and 30-cm solar radio fluxes (F10.7 and F30).Plain Language Summary When ultraviolet light from the Sun is absorbed in the Earth's upper atmosphere above 70 km, it can impact radio communications and satellite orbits. The brightest solar wavelength in the ultraviolet is called the Lyman-alpha line and is emitted by hydrogen in the Sun's atmosphere. Because ultraviolet light is absorbed by the Earth's atmosphere, measurements of the Lyman-alpha line must be made by satellites which are above most the atmosphere. This paper is about the development of a set of daily measurements of Lyman-alpha brightness (irradiance) from 1947 through the present time. This data set will be used to validate other solar irradiance data, models of the Sun's variable intensity, and models of terrestrial atmospheric processes.

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Section: Previous Lasp Lyman α Composites (Versions 1–3)mentioning

confidence: 99%

An Improved Lyman‐Alpha Composite

Machol

Snow

Woodraska

et al. 2019

Earth and Space Science

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“…FISM‐M advances daily and flare empirical irradiance variability modeling by relating measurements of EUV irradiance variations in broad spectral bands to spectral irradiance measurements in the 6–106 nm range made by the EUV Variability Experiment (EVE) [ Woods et al , ], which is on board the Solar Dynamics Observatory (SDO) satellite launched on 11 February 2010 and has improved spectral and temporal resolution as well as an improved responsivity calibration accuracy compared to its predecessor, Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) Solar EUV Experiment (SEE) [ Woods et al , ; Hock et al , ]. The 6–106 nm range is measured by EVE with the Multiple EUV Grating Spectrographs (MEGS) at 0.1 nm resolution and 10s time cadence.…”

Section: Introductionmentioning

confidence: 99%

“…SDO EVE's improved observation cadence is suitable for measuring flare irradiance, which can vary by tens to hundreds of percent over a period of minutes and last tens of minutes to hours (depending on wavelength and flare magnitude). With regard to improved uncertainty, the MEGS responsivity is known to within 1–3% (1 σ ) uncertainty below 80 nm from preflight calibrations [ Hock et al , ], in comparison with the 3–7% (1 σ ) preflight responsivity uncertainty of SEE EGS [ Woods et al , ].…”

Section: Introductionmentioning

confidence: 99%

The MAVEN EUVM model of solar spectral irradiance variability at Mars: Algorithms and results

et al. 2017

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Solar extreme ultraviolet (EUV) radiation is a primary energy input to the Mars atmosphere, causing ionization and driving photochemical processes above approximately 100 km. Because solar EUV radiation varies with wavelength and time, measurements must be spectrally resolved to accurately quantify its impact on the Mars atmosphere. The Mars Atmosphere and Volatile EvolutioN (MAVEN) EUV Monitor (EUVM) measures solar EUV irradiance incident on the Mars atmosphere in three bands. These three bands drive a spectral irradiance variability model called the Flare Irradiance Spectral Model (FISM)‐Mars (FISM‐M) which is an iteration of the FISM model by Chamberlin et al. (2007, 2008) for spectral irradiance at Earth. In this paper, we report the algorithms used to derive FISM‐M and its associated uncertainties, focusing on differences from the original FISM. FISM‐M spectrally resolves the solar EUV irradiance at Mars from 0.5 to 189.5 nm at 1min cadence, and 0.1 nm resolution in the 6–106 nm range or 1 nm resolution otherwise. FISM‐M is suitable for both daily average and flaring spectral irradiance estimates and is based on the linear association of the broadband EUVM measurements with spectral irradiance measurements, including recent high time cadence 0.1 nm resolution measurements from the EUV Variability Experiment (EVE) on the Space Dynamics Observatory (SDO) between 6 and 106 nm. In addition, we present examples of model outputs for EUV irradiance variability due to solar flares, solar rotations, Mars orbit eccentricity, and the solar cycle, between October 2015 and November 2016.

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“…Considering the corona in such a holistic sense provides perspectives lost in narrowly focused active region studies. EVE spectra are particularly well suited to this task because extra effort has been made to provide in-flight calibration thanks to sounding rocket under-flights with an identical instrument (Hock et al 2010). Additionally, the ability to identify individual emission lines in EVE spectra allows for the selection of diagnostics representing a wide range of coronal conditions.…”

Section: Introductionmentioning

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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Extreme Ultraviolet Variability Experiment (EVE) Multiple EUV Grating Spectrographs (MEGS): Radiometric Calibrations and Results

Cited by 10 publications

References 20 publications

An Improved Lyman‐Alpha Composite

An Improved Lyman‐Alpha Composite

The MAVEN EUVM model of solar spectral irradiance variability at Mars: Algorithms and results

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

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