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Harder JW, Béland S, Penton S, Woods TN. Long-Term Trend Analysis in the Solar Radiation and Climate Experiment (SORCE)/ Spectral Irradiance Monitor (SIM). SOLAR PHYSICS 2022; 297:69. [PMID: 35663641 PMCID: PMC9160118 DOI: 10.1007/s11207-022-02001-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 05/09/2022] [Indexed: 06/14/2023]
Abstract
The Solar Radiation and Climate Experiment/Spectral Irradiance Monitor (SORCE/SIM) instrument was launched on 25 January 2003 with mission termination occurring on 25 February 2020. The SORCE/SIM provides a unique data set of the variability in solar spectral irradiance (SSI) during the descending phase of Solar Cycle 23 (SC23) from April 2003 to February 2009, the weaker solar-maximum conditions of SC24, and the quiescent SC24/SC25 minimum. The determination of the magnitude and phase of SSI variations rely on the unambiguous determination of the effects of the space environment and solar-exposure-related degradation mechanisms. The instrument-only corrections for SIM are based on a comparison of two functionally identical (mirror image) prism spectrometers with four independent detectors in each spectrometer channel. The degradation correction is strictly instrumental in its methodology and makes no assumptions about the magnitude, slope, or wavelength dependence of the SSI variability.
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Affiliation(s)
- Jerald W. Harder
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 USA
| | - Stéphane Béland
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 USA
| | - Steven Penton
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 USA
| | - Thomas N. Woods
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 USA
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Woods TN, Harder JW, Kopp G, Snow M. Solar-Cycle Variability Results from the Solar Radiation and Climate Experiment (SORCE) Mission. SOLAR PHYSICS 2022; 297:43. [PMID: 35465471 PMCID: PMC8986744 DOI: 10.1007/s11207-022-01980-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 03/15/2022] [Indexed: 06/14/2023]
Abstract
The Solar Radiation and Climate Experiment (SORCE) was a NASA mission that operated from 2003 to 2020 to provide key climate-monitoring measurements of total solar irradiance (TSI) and solar spectral irradiance (SSI). This 17-year mission made TSI and SSI observations during the declining phase of Solar Cycle 23, during all of Solar Cycle 24, and at the very beginning of Solar Cycle 25. The SORCE solar-variability results include comparisons of the solar irradiance observed during Solar Cycles 23 and 24 and the solar-cycle minima levels in 2008 - 2009 and 2019 - 2020. The differences between these two minima are very small and are not significantly above the estimate of instrument stability over the 11-year period. There are differences in the SSI variability for Solar Cycles 23 and 24, notably for wavelengths longer than 250 nm. Consistency comparisons with SORCE variability on solar-rotation timescales and solar-irradiance model predictions suggest that the SORCE Solar Cycle 24 SSI results might be more accurate than the SORCE Solar Cycle 23 results. The SORCE solar-variability results have been useful for many Sun-climate studies and will continue to serve as a reference for comparisons with future missions studying solar variability.
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Affiliation(s)
- Thomas N. Woods
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
| | - Jerald W. Harder
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
| | - Greg Kopp
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
| | - Martin Snow
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
- South African National Space Agency Hospital Street, Hermanus, 7200 South Africa
- Department of Physics and Astronomy Robert Sobukwe Road, University of the Western Cape, Bellville, 7535 South Africa
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Thuillier G, Zhu P, Snow M, Zhang P, Ye X. Characteristics of solar-irradiance spectra from measurements, modeling, and theoretical approach. LIGHT, SCIENCE & APPLICATIONS 2022; 11:79. [PMID: 35351849 PMCID: PMC8964690 DOI: 10.1038/s41377-022-00750-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 02/14/2022] [Accepted: 02/22/2022] [Indexed: 06/12/2023]
Abstract
An accurate solar-irradiance spectrum is needed as an input to any planetary atmosphere or climate model. Depending on the spectral characteristics of the chosen model, uncertainties in the irradiance may introduce significant differences in atmospheric and climate predictions. This is why several solar spectral-irradiance data sets have been published during the last decade. They have been obtained by different methods: either measurements from a single instrument or a composite of different spectra, or they are theoretical or semi-empirical solar models. In this paper, these spectral datasets will be compared in terms of irradiance, power per spectral interval, their derived solar-atmosphere brightness temperature, and time series. Whatever the different sources of these spectra are, they generally agree to within their quoted accuracy. The solar-rotation effect simultaneously observed by SORCE and PREMOS-PICARD is accurately measured. The 11-year long-term variability remains a difficult task, given the weak activity of solar cycle 24 and long-term instrument aging.
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Affiliation(s)
- Gerard Thuillier
- Physikalisch-Meteorologisches Observatorium Davos World Radiation Centre (PMOD/WRC), Davos Dorf, Switzerland
| | - Ping Zhu
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Science, 3888 Dong Nanhu Road, Changchun, 130033, China.
- Royal Observatory of Belgium, Av. Circulaire 3, 1180, Brussels, Belgium.
| | - Martin Snow
- Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, 80309, USA
- South African National Space Agency (SANSA), Hospital Street, Hermanus, 7200, South Africa
- University of the Western Cape, Department of Physics and Astronomy, Robert Sobukwe Rd, Belville, Cape Town, 7535, South Africa
| | - Peng Zhang
- National Satellite Meteorological Center, China Meteorological Administration, Beijing, 100081, China
- Innovation Center for FengYun Meteorological Satellite, China Meteorological Administration, Beijing, 100081, China
| | - Xin Ye
- Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Science, 3888 Dong Nanhu Road, Changchun, 130033, China
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Abstract
For the first time thermospheric parameters (neutral composition, exospheric temperature and vertical plasma drift related to thermospheric winds) have been inferred for ionospheric G-conditions observed with Millstone Hill ISR on 11–13 September 2005; 13 June 2005, and 15 July 2012. The earlier developed method to extract a consistent set of thermospheric parameters from ionospheric observations has been revised to solve the problem in question. In particular CHAMP/STAR and GOCE neutral gas density observations were included into the retrieval process. It was found that G-condition days were distinguished by enhanced exospheric temperature and decreased by ~2 times of the column atomic oxygen abundance in a comparison to quiet reference days, the molecular nitrogen column abundance being practically unchanged. The inferred upward plasma drift corresponds to strong ~90 m/s equatorward thermospheric wind presumably related to strong auroral heating on G-condition days.
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Woods TN, Harder JW, Kopp G, McCabe D, Rottman G, Ryan S, Snow M. Overview of the Solar Radiation and Climate Experiment (SORCE) Seventeen-Year Mission. SOLAR PHYSICS 2021; 296:127. [PMID: 34776547 PMCID: PMC8550650 DOI: 10.1007/s11207-021-01869-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 07/21/2021] [Indexed: 06/12/2023]
Abstract
The Solar Radiation and Climate Experiment (SORCE) was a NASA mission that operated from 2003 to 2020 to provide key climate-monitoring measurements of total solar irradiance (TSI) and solar spectral irradiance (SSI). Three important accomplishments of the SORCE mission are i) the continuation of the 42-year-long TSI climate data record, ii) the continuation of the ultraviolet SSI record, and iii) the initiation of the near-ultraviolet, visible, and near-infrared SSI records. All of the SORCE instruments functioned well over the 17-year mission, which far exceeded its five-year prime mission goal. The SORCE spacecraft, having mostly redundant subsystems, was also robust over the mission. The end of the SORCE mission was a planned passivation of the spacecraft following a successful two-year overlap with the NASA Total and Spectral Solar Irradiance Sensor (TSIS) mission, which continues the TSI and SSI climate records. There were a couple of instrument anomalies and a few spacecraft anomalies during SORCE's long mission, but operational changes and updates to flight software enabled SORCE to remain productive to the end of its mission. The most challenging of the anomalies was the degradation of the battery capacity that began to impact operations in 2009 and was the cause for the largest SORCE data gap (August 2013 - February 2014). An overview of the SORCE mission is provided with a couple of science highlights and a discussion of flight anomalies that impacted the solar observations. Companion articles about the SORCE instruments and their final science data-processing algorithms provide additional details about the instrument measurements over the duration of the mission.
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Affiliation(s)
- Thomas N. Woods
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
| | - Jerald W. Harder
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
| | - Greg Kopp
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
| | - Debra McCabe
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
| | - Gary Rottman
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
| | - Sean Ryan
- Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Dr., Boulder, CO 80303 USA
| | - Martin Snow
- South African National Space Agency, Hospital Street, Hermanus, 7200 South Africa
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Meier RR. The Thermospheric Column O/N 2 Ratio. JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS 2021; 126:e2020JA029059. [PMID: 33968559 PMCID: PMC8097966 DOI: 10.1029/2020ja029059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 02/26/2021] [Indexed: 06/12/2023]
Abstract
More than 2 decades ago, D. J. Strickland and colleagues proposed use of the O/N2 column number density ratio as a new geophysical quantity to interpret thermospheric processes recorded in far ultraviolet (FUV) images of the Earth. This concept has enabled multiple advances in understanding the global behavior of Earth's thermosphere. Nevertheless, confusion remains about the conceptual meaning of the column density ratio, and in the application of this integral quantity. This is so even though it is now a key thermospheric measurement made by current and planned far ultraviolet remote sensing missions in pursuit of new understanding of thermospheric processes and variability. The intent here is to review the historical context of the O/N2 column density ratio, clarify its physical meaning, and resolve misunderstandings evident in the literature. Simple examples elucidate its original derivation for extracting column O/N2 ratios from measurements of the OI 135.6 nm/N2 Lyman-Birge-Hopfield (LBH) emission based on an algorithmic synthesis of model precomputations. These are organized in the form of a table lookup of column density ratio as a function of observed radiance ratios. To accommodate generalized solar-geophysical and viewing conditions, the table required to specify the number of needed parameters becomes large. Proposed as an alternative is a simplified, first principles approach to obtaining the column density ratio from the emission ratio. This new methodology is now being applied successfully to FUV measurements made from onboard the Ionospheric CONnection satellite and will be applied retrospectively to the Global Ultraviolet Imager data.
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Affiliation(s)
- R. R. Meier
- Department of Physics and Astronomym, George Mason University, Fairfax, VA, USA
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Daytime mid-latitude F 2-layer Q-disturbances: A formation mechanism. Sci Rep 2020; 10:9997. [PMID: 32561762 PMCID: PMC7305116 DOI: 10.1038/s41598-020-66134-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 05/11/2020] [Indexed: 11/08/2022] Open
Abstract
Negative and positive near noontime prolonged (≥3 hours) F2-layer Q-disturbances with deviations in NmF2 > 35% occurred at Rome have been analyzed using aeronomic parameters inferred from fp180 (plasma frequency at 180 km height) and foF2 observations. Both types of NmF2 perturbations occur under quiet (daily Ap < 15 nT) geomagnetic conditions. Day-to-day atomic oxygen [O] variations at F2-region heights specify the type (positive or negative) of Q-disturbance. The [O] concentration is larger on positive and is less on negative Q-disturbance days compared to reference days. This difference takes place not only on average but for all individual Q-disturbances in question. An additional contribution to Q-disturbances formation is provided by solar EUV day-to-day variations. Negative Q-disturbance days are characterized by lower hmF2 while positive – by larger hmF2 compared to reference days. This is due to larger average Tex and vertical plasma drift W on positive Q-disturbance days, the inverse situation takes place for negative Q-disturbance days. Day-to-day changes in global thermospheric circulation may be considered as a plausible mechanism. The analyzed type of F2-layer Q-disturbances can be explained in the framework of contemporary understanding of the thermosphere-ionosphere interaction based on solar and geomagnetic activity as the main drivers.
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