Wavelength Dependence of Solar Rotation and Solar Cycle UV Irradiance Variations

It is shown that for the 5-year period 1982 to 1987 the solar irradiance decrease is estimated to be about 5 to 7 percent over the spectral interval 195 to 225 nm. This change becomes progressively smaller with increasing wavelength. For the 2-1/3 year period, January 1987 to April 1989, the irradiance increases about 6 percent at 195 to 205 nm and about 2 percent between 215 to 250 nm. Both 27-day and 13.5-day relative amplitudes peak at the time near solar maximum (1982) but remain comparatively small between 1983 and the onset of solar cycle 22. An average 280 day oscillation is noted for wavelengths up to 230 nm. No physical mechanism is offered for this variation

Observed solar near UV variability: A contribution to variations of the solar constant

Continuous Measurements of the Solar UV have been made by an instrument on the Solar Mesosphere Explorer (SME) since October 1981. The results for the wavelength interval 200 to 300 nm show an irradiance decrease to a minimum in early 1987 and a subsequent increase to mid-April 1989. The observed UV changes during part of solar cycles 21 to 22 represent approx. 35 percent (during the decreasing phase) and 25 percent (during the increasing phase) of the observed variations of the solar constant for the same time period as the SME measurements

Vacuum ultraviolet instrumentation for solar irradiance and thermospheric airglow

A NASA sounding rocket experiment was developed to study the solar extreme ultraviolet (EUV) spectral irradiance and its effect on the upper atmosphere. Both the solar flux and the terrestrial molecular nitrogen via the Lyman-Birge-Hopfield bands in the far ultraviolet (FUV) were measured remotely from a sounding rocket on October 27, 1992. The rocket experiment also includes EUV instruments from Boston University (Supriya Chakrabarti), but only the National Center for Atmospheric Research (NCAR)/University of Colorado (CU) four solar instruments and one airglow instrument are discussed here. The primary solar EUV instrument is a 1/4 meter Rowland circle EUV spectrograph which has flown on three rockets since 1988 measuring the solar spectral irradiance from 30 to 110 nm with 0.2 nm resolution. Another solar irradiance instrument is an array of six silicon XUV photodiodes, each having different metallic filters coated directly on the photodiodes. This photodiode system provides a spectral coverage from 0.1 to 80 nm with about 15 nm resolution. The other solar irradiance instrument is a silicon avalanche photodiode coupled with pulse height analyzer electronics. This avalanche photodiode package measures the XUV photon energy providing a solar spectrum from 50 to 12,400 eV (25 to 0.1 nm) with an energy resolution of about 50 eV. The fourth solar instrument is an XUV imager that images the sun at 17.5 nm with a spatial resolution of 20 arc-seconds. The airglow spectrograph measures the terrestrial FUV airglow emissions along the horizon from 125 to 160 nm with 0.2 nm spectral resolution. The photon-counting CODACON detectors are used for three of these instruments and consist of coded arrays of anodes behind microchannel plates. The one-dimensional and two-dimensional CODACON detectors were developed at CU by Dr. George Lawrence. The pre-flight and post-flight photometric calibrations were performed at our calibration laboratory and at the Synchrotron Ultraviolet Radiation Facility (SURF) at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland

2003: Total irradiance monitor design and on-orbit functionality. SPIE

The solar Total Irradiance Monitor (TIM) on NASA's SORCE mission began taking data in early 2003. This instrument continues the 25-year record of space-borne, total solar irradiance (TSI) measurements, with improved precision from its new technologies and calibration methods. We present an overview of the TIM instrument, including the design features enabling its high precision, and we present preliminary on-orbit TSI data

SORCE Monitors Solar Variability during Record Solar Flares

The SORCE mission monitors solar variability to determine its impact on the Earths climate. The X-ray photometer aboard SORCE observes the record-breaking solar flares in the Fall of 2003. The line graph shows the photometers measured solar radiation flux in the 1-7 nanometer wavelength band (x-ray) measured in milliwatts per square meter. The ultraviolet (195 Angstrom) imagery from SOHO-EIT (green) illustrates where the flares (the bright white spots) are located on the solar disk. Educational levels: Undergraduate lower division, Undergraduate upper division, Graduate or professional

The Solar Constant - Faculae vs. Sunspots

Three views of the Sun showing different levels of solar activity. The color table has been altered to enhance the appearance of the faculae (white regions) which are hotter than sunspots (red-black regions) and whose greater total area contribute to increasing the solar flux reaching the Earth. Educational levels: Undergraduate lower division, Undergraduate upper division, Graduate or professional

Zoom-out from the Sun

A close-up view of a sunspot group with faculae and pull-out to show the entire Sun. Educational levels: Undergraduate lower division, Undergraduate upper division, Graduate or professional