The GOES-R EUVS model for EUV irradiance variability

The Geostationary Operational Environmental Satellite R (GOES-R) series of four satellites are the next generation NOAA GOES satellites. Once on orbit and commissioned, they are renamed GOES 16–19, making critical terrestrial and space weather measurements through 2035. GOES 16 and 17 are currently on orbit, having been launched in 2016 and 2018, respectively. The GOES-R satellites include the Extreme Ultraviolet (EUV) and X-ray Irradiance Sensors (EXIS) instrument suite, which measures calibrated solar irradiance in eight lines or bands between 25 nm and 285 nm with the Extreme Ultraviolet Sensors (EUVS) instrument. EXIS also includes the X-Ray Sensor (XRS) instrument, which measures solar soft X-ray irradiance at the legacy GOES bands. The EUVS Measurements are used as inputs to the EUVS Model, a solar spectral irradiance model for space weather operations that predicts irradiance in twenty-two 5 nm wide intervals from 5 nm to 115 nm, and one 10 nm wide interval from 117 to 127 nm at 30 s cadence. Once fully operational, NOAA will distribute the EUVS Model irradiance with 1 min latency as a primary space weather data product, ushering in a new era of rapid dissemination and measurement continuity of EUV irradiance spectra. This paper describes the EUVS Model algorithms, data sources, calibration methods and associated uncertainties. Typical model (relative) uncertainties are less than ~5% for variability at time-scales longer than 6 h, and are ~25% for solar flare induced variability. The absolute uncertainties, originating from the instruments used to calibrate the EUVS Model, are ~10%. Examples of model results are presented at both sub-daily and multi-year timescales to demonstrate the model’s capabilities and limitations. Example solar flare irradiances are also modeled.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316008668 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 134-137

Author(s):

John P. Pye ◽

Simon R. Rosen

Keyword(s):

Solar System ◽

Solar Flare ◽

Space Weather ◽

White Light ◽

Large Scale ◽

The Sun ◽

X Ray ◽

Cool Star ◽

Exoplanetary Systems ◽

Solar Type

AbstractWe present estimates of cool-star X-ray flare rates determined from the XMM-Tycho survey (Pyeet al. 2015, A&A, 581, A28), and compare them with previously published values for the Sun and for other stellar EUV and white-light samples. We demonstrate the importance of applying appropriate corrections, especially in regard to the total, effective size of the stellar sample. Our results are broadly consistent with rates reported in the literature for Kepler white-light flares from solar-type stars, and with extrapolations of solar flare rates, indicating the potential of stellar X-ray flare observations to address issues such as ‘space weather’ in exoplanetary systems and our own solar system.

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GOES High cadence Operational Total Irradiance: planned data products

10.5194/egusphere-egu21-10348 ◽

2021 ◽

Author(s):

Martin Snow ◽

Stephane Beland ◽

Odele Coddington ◽

Steven Penton ◽

Don Woodraska

Keyword(s):

Extreme Ultraviolet ◽

Solar Spectrum ◽

Total Solar Irradiance ◽

The Other ◽

Spectral Irradiance ◽

First Year ◽

X Ray ◽

Solar Spectral Irradiance ◽

Total Irradiance ◽

High Cadence

The GOES-R series of satellites includes a redesigned instrument for solar spectral irradiance: the Extreme ultraviolet and X-ray Irradiance Sensor (EXIS).&#160; Our team will be using a high-cadence broadband visible light diode to construct a proxy for Total Solar Irradiance (TSI).&#160; This will have two advantages over the existing TSI measurements:&#160; measurements are taken at 4 Hz, so the cadence of our TSI proxy is likely faster than any existing applications, and the observations are taken from geostationary orbit, so the time series of measurements is virtually uninterrupted.&#160; Calibration of the diode measurements will still rely on the standard TSI composites.&#160;&#160;The other measurement from EXIS that will be used is the Magnesium II core-to-wing ratio.&#160; The MgII index is a proxy for chromospheric activity, and is measured by EXIS every 3 seconds.&#160; The combination of the two proxies can be used to generate a model of the full solar spectrum similar to the NRLSSI2 empirical model.We are in the first year of a three-year grant to develop the TSI proxy and the SSI model, so only very preliminary findings will be discussed in this presentation.

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Forecasting Solar Energetic Particle (SEP) events with Flare X-ray peak ratios

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2018033 ◽

2018 ◽

Vol 8 ◽

pp. A47 ◽

Cited By ~ 5

Author(s):

Stephen W. Kahler ◽

Alan. G. Ling

Keyword(s):

Solar Flare ◽

Space Weather ◽

Coronal Mass Ejections ◽

Energetic Particle ◽

Solar Energetic Particle ◽

Western Hemisphere ◽

X Rays ◽

X Ray ◽

Forecasting Methods ◽

Versus Peak

Solar flare X-ray peak fluxes and fluences in the 0.1–0.8 nm band are often used in models to forecast solar energetic particle (SEP) events. Garcia (2004) [Forecasting methods for occurrence and magnitude of proton storms with solar soft X rays, Space Weather, 2, S02002, 2004] used ratios of the 0.05–0.4 and 0.1–0.8 nm bands of the X-ray instrument on the GOES spacecraft to plot inferred peak flare temperatures versus peak 0.1–0.8 nm fluxes for flares from 1988 to 2002. Flares associated with E > 10 MeV SEP events of >10 proton flux units (pfu) had statistically lower peak temperatures than those without SEP events and therefore offered a possible empirical forecasting tool for SEP events. We review the soft and hard X-ray flare spectral variations as SEP event forecast tools and repeat Garcia’s work for the period 1998–2016, comparing both the peak ratios and the ratios of the preceding 0.05–0.4 nm peak fluxes to the later 0.1–0.8 nm peak fluxes of flares >M3 to the occurrence of associated SEP events. We divide the events into eastern and western hemisphere sources and compare both small (1.2–10 pfu) and large (≥300 pfu) SEP events with those of >10 pfu. In the western hemisphere X-ray peak ratios are statistically lower for >10 pfu SEP events than for non-SEP events and are even lower for the large (>300 pfu) events. The small SEP events, however, are not distinguished from the non-SEP events. We discuss the possible connections between the flare X-ray peak ratios and associated coronal mass ejections that are presumed to be the sources of the SEPs.

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Preflare very long-periodic pulsations observed in Hα emission before the onset of a solar flare

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038398 ◽

2020 ◽

Vol 639 ◽

pp. L5

Author(s):

Dong Li ◽

Song Feng ◽

Wei Su ◽

Yu Huang

Keyword(s):

Solar Flare ◽

Light Curve ◽

Solar Flares ◽

Extreme Ultraviolet ◽

Light Curves ◽

Trigger Mechanism ◽

X Ray ◽

Hα Emission ◽

Plasma Loop ◽

Full Disk

Context. Very long-periodic pulsations during preflare phases (preflare-VLPs) have been detected in the full-disk solar soft X-ray (SXR) flux. They may be regarded as precursors to solar flares and may help us better understand the trigger mechanism of solar flares. Aims. In this Letter, we report a preflare-VLP event prior to the onset of an M1.1 circular-ribbon flare on 2015 October 16. It was simultaneously observed in Hα, SXR, and extreme ultraviolet (EUV) wavelengths. Methods. The SXR fluxes in 1−8 Å and 1−70 Å were recorded by the Geostationary Operational Environmental Satellite (GOES) and Extreme Ultraviolet Variability Experiment, respectively; the light curves in Hα and EUV 211 Å were integrated over a small local region, which were measured by the 1 m New Vacuum Solar Telescope and the Atmospheric Imaging Assembly (AIA), respectively. The preflare-VLP is identified as the repeat and quasi-periodic pulses in light curves during preflare phase. The quasi-periodicity can be determined from the Fourier power spectrum with Markov chain Monte Carlo-based Bayesian. Results. Seven well-developed pulses are found before the onset of an M1.1 circular-ribbon flare. They are firstly seen in the local light curve in Hα emission and then discovered in full-disk SXR fluxes in GOES 1−8 Å and ESP 1−70 Å, as well as the local light curve in AIA 211 Å. These well-developed pulses can be regarded as the preflare-VLP, which might be modulated by LRC-circuit oscillation in the current-carrying plasma loop. The quasi-period is estimated to be ∼9.3 min. Conclusions. We present the first report of a preflare-VLP event in the local Hα line and EUV wavelength, which could be considered a precursor of a solar flare. This finding should therefore prove useful for the prediction of solar flares, especially for powerful flares.

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Solar Flares

Oxford Research Encyclopedia of Physics ◽

10.1093/acrefore/9780190871994.013.20 ◽

2020 ◽

Author(s):

Dana Longcope

Keyword(s):

Solar Flare ◽

Current Sheet ◽

Extreme Ultraviolet ◽

Magnetic Energy ◽

Theoretical Models ◽

Heat Radiation ◽

Electromagnetic Spectrum ◽

Model Framework ◽

X Ray ◽

Solar Brightness

A solar flare is a transient increase in solar brightness powered by the release of magnetic energy stored in the Sun’s corona. Flares are observed in all wavelengths of the electromagnetic spectrum. The released magnetic energy heats coronal plasma to temperatures exceeding ten million Kelvins, leading to a significant increase in solar brightness at X-ray and extreme ultraviolet wavelengths. The Sun’s overall brightness is normally low at these wavelengths, and a flare can increase it by two or more an orders of magnitude. The size of a given flare is traditionally characterized by its peak brightness in a soft X-ray wavelength. Flares occur with frequency inversely related to this measure of size, with those of greatest size occuring less than once per year. Images and light curves from different parts of the spectrum from many different flares have led to an accepted model framework for explaining the typical solar flare. According to this model, a sheet of electric current (a current sheet) is first formed in the corona, perhaps by a coronal mass ejection. Magnetic reconnection at this current sheet allows stored magnetic energy to be converted into bulk flow energy, heat, radiation, and a population of non-thermal electrons and ions. Some of this energy is transmitted downward to cooler layers, which are then evaporated (or ablated) upward to fill the coronal with hot dense plasma. Much of the flares bright emission comes from this newly heated plasma. Theoretical models have been proposed to describe each step in this process.

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Extreme‐Ultraviolet and X‐Ray Spectroscopy of a Solar Flare Loop Observed at High Time Resolution: A Case Study in Chromospheric Evaporation

The Astrophysical Journal ◽

10.1086/422873 ◽

2004 ◽

Vol 613 (1) ◽

pp. 580-591 ◽

Cited By ~ 92

Author(s):

Jeffrey W. Brosius ◽

Kenneth J. H. Phillips

Keyword(s):

Solar Flare ◽

Time Resolution ◽

Extreme Ultraviolet ◽

High Time ◽

High Time Resolution ◽

Flare Loop ◽

X Ray ◽

Chromospheric Evaporation

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Extreme ultraviolet spectral irradiance measurements since 1946

History of Geo- and Space Sciences ◽

10.5194/hgss-6-3-2015 ◽

2015 ◽

Vol 6 (1) ◽

pp. 3-22 ◽

Cited By ~ 8

Author(s):

G. Schmidtke

Keyword(s):

Real Time ◽

Space Weather ◽

Extreme Ultraviolet ◽

Dominant Role ◽

Low Cost ◽

Solar Spectrum ◽

Upper Atmosphere ◽

Spectral Irradiance ◽

Time Space ◽

The Impact

Abstract. In the physics of the upper atmosphere the solar extreme ultraviolet (EUV) radiation plays a dominant role controlling most of the thermospheric/ionospheric (T/I) processes. Since this part of the solar spectrum is absorbed in the thermosphere, platforms to measure the EUV fluxes became only available with the development of rockets reaching altitude levels exceeding 80 km. With the availability of V2 rockets used in space research, recording of EUV spectra started in 1946 using photographic films. The development of pointing devices to accurately orient the spectrographs toward the sun initiated intense activities in solar–terrestrial research. The application of photoelectric recording technology enabled the scientists placing EUV spectrometers aboard satellites observing qualitatively strong variability of the solar EUV irradiance on short-, medium-, and long-term scales. However, as more measurements were performed more radiometric EUV data diverged due to the inherent degradation of the EUV instruments with time. Also, continuous recording of the EUV energy input to the T/I system was not achieved. It is only at the end of the last century that there was progress made in solving the serious problem of degradation enabling to monitore solar EUV fluxes with sufficient radiometric accuracy. The data sets available allow composing the data available to the first set of EUV data covering a period of 11 years for the first time. Based on the sophisticated instrumentation verified in space, future EUV measurements of the solar spectral irradiance (SSI) are promising accuracy levels of about 5% and less. With added low-cost equipment, real-time measurements will allow providing data needed in ionospheric modeling, e.g., for correcting propagation delays of navigation signals from space to earth. Adding EUV airglow and auroral emission monitoring by airglow cameras, the impact of space weather on the terrestrial T/I system can be studied with a spectral terrestrial irradiance camera (STI-Cam) and also be used investigating real-time space weather effects and deriving more detailed correction procedures for the evaluation of Global Navigation Satellite System (GNSS) signals. Progress in physics goes with achieving higher accuracy in measurements. This review historically guides the reader on the ways of exploring the impact of the variable solar radiation in the extreme ultraviolet spectral region on our upper atmosphere in the altitude regime from 80 to 1000 km.

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A DEFT Way to Forecast Solar Flares

The Astrophysical Journal ◽

10.3847/1538-4357/ac2840 ◽

2021 ◽

Vol 922 (2) ◽

pp. 218

Author(s):

Larisza D. Krista ◽

Matthew Chih

Keyword(s):

Space Weather ◽

Solar Flares ◽

Extreme Ultraviolet ◽

Weather Forecast ◽

Start Time ◽

X Ray ◽

Solar Observations ◽

Solar Eruptions ◽

Intensity Changes ◽

Solar Ultraviolet

Abstract Solar flares have been linked to some of the most significant space weather hazards at Earth. These hazards, including radio blackouts and energetic particle events, can start just minutes after the flare onset. Therefore, it is of great importance to identify and predict flare events. In this paper we introduce the Detection and EUV Flare Tracking (DEFT) tool, which allows us to identify flare signatures and their precursors using high spatial and temporal resolution extreme-ultraviolet (EUV) solar observations. The unique advantage of DEFT is its ability to identify small but significant EUV intensity changes that may lead to solar eruptions. Furthermore, the tool can identify the location of the disturbances and distinguish events occurring at the same time in multiple locations. The algorithm analyzes high temporal cadence observations obtained from the Solar Ultraviolet Imager instrument aboard the GOES-R satellite. In a study of 61 flares of various magnitudes observed in 2017, the “main” EUV flare signatures (those closest in time to the X-ray start time) were identified on average 6 minutes early. The “precursor” EUV signatures (second-closest EUV signatures to the X-ray start time) appeared on average 14 minutes early. Our next goal is to develop an operational version of DEFT and to simulate and test its real-time use. A fully operational DEFT has the potential to significantly improve space weather forecast times.

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