Flare Irradiance Spectral Model (FISM): Daily component algorithms and results

[1] The solar photon output from the Sun was once thought to be constant but is now known to vary considerably over timescales from seconds during solar flares to years due to the solar cycle. This is especially true in the wavelengths shorter than 208 nm (Al ionization edge), where measurements and models of the solar irradiance at these short wavelengths are needed. The time-variant solar irradiance drives physical changes in the Earth's atmosphere that can affect many things including GPS accuracy and satellite drag rates. The Flare Irradiance Spectral Model (FISM) is an empirical model that estimates the solar irradiance at wavelengths from 0.1 to 190 nm at 1 nm resolution with a time cadence of 60 s. This is a high enough temporal resolution to model variations due to solar flares, where few accurate measurements at these wavelengths exist, as well as the solar cycle and solar rotation variations. The modeling of the FISM daily component, including the solar irradiance variations due to the solar cycle and the solar rotation, is the topic of this paper. The daily component algorithms are given, and results and comparisons of the daily component demonstrate that the FISM estimations agree within the stated uncertainties to the various measurements of the solar VUV irradiance. A third type of event that causes sudden changes in the solar irradiance is solar flares. The FISM modeling of the variations in the solar irradiance due to solar flares is the topic of the second paper.

[1]  W. Kent Tobiska,et al.  SOLAR2000 irradiances for climate change research, aeronomy and space system engineering , 2004 .

[2]  Yuei-An Liou,et al.  Ionospheric solar flare effects monitored by the ground‐based GPS receivers: Theory and observation , 2004 .

[3]  Gary J. Rottman,et al.  The SOLAR2000 empirical solar irradiance model and forecast tool , 2000 .

[4]  H. Hinteregger,et al.  Observational, reference and model data on solar EUV, from measurements on AE-E , 1981 .

[5]  L. R. Canfield,et al.  First Solar EUV Irradiances Obtained from SOHO by the Celias/Sem , 1998 .

[6]  Judith L. Lean,et al.  THE SUN'S VARIABLE RADIATION AND ITS RELEVANCE FOR EARTH1 , 1997 .

[7]  Harry P. Warren,et al.  A new reference spectrum for the EUV irradiance of the quiet Sun , 1998 .

[8]  Donald F. Heath,et al.  The Mg 280‐nm doublet as a monitor of changes in solar ultraviolet irradiance , 1986 .

[9]  T. Woods,et al.  HEUVAC: A new high resolution solar EUV proxy model , 2006 .

[10]  R. Viereck,et al.  A composite Mg II index spanning from 1978 to 2003 , 2004 .

[11]  P. Richards,et al.  EUVAC: A solar EUV Flux Model for aeronomic calculations , 1994 .

[12]  H. P. Warren,et al.  A new model of solar EUV irradiance variability 2. Comparisons with empirical models and observations and implications for space weather , 2003 .

[13]  K. Tapping,et al.  Recent solar radio astronomy at centimeter wavelengths: The temporal variability of the 10.7‐cm flux , 1987 .

[14]  J. Worden,et al.  Improved solar Lyman α irradiance modeling from 1947 through 1999 based on UARS observations , 2000 .

[15]  Gary J. Rottman,et al.  Solar‐Stellar Irradiance Comparison Experiment 1: 1. Instrument design and operation , 1993 .

[16]  R. F. Donnelly.  Empirical models of solar flare X ray and EUV emission for use in studying their E and F region effects , 1976 .

[17]  H. Warren.  A Solar Minimum Irradiance Spectrum for Wavelengths below 1200 Å , 2005 .

[18]  J. Lean,et al.  A new model of solar EUV irradiance variability: 1. Model formulation , 2001 .

[19]  Gary J. Rottman,et al.  Solar EUV Experiment (SEE): Mission overview and first results , 2005 .

[20]  Thomas N. Woods,et al.  Rocket Extreme Ultraviolet Grating Spectrometer (EGS): calibrations and results of the solar irradiance on February 8, 2002 , 2006 .

[21]  Gary J. Rottman,et al.  TIMED solar EUV experiment , 1998, Optics & Photonics.

[22]  R. Viereck,et al.  The Mg II index: A proxy for solar EUV , 2001 .

[23]  John R. Worden,et al.  Far-Ultraviolet Intensities and Center-to-Limb Variations of Active Regions and Quiet Sun Using UARS SOLSTICE Irradiance Measurements and Ground-based Spectroheliograms , 2001 .

[24]  P. R. Bevington,et al.  Data Reduction and Error Analysis for the Physical Sciences , 1969 .

[25]  David A. Crotser,et al.  The EUV Variability Experiment (EVE) aboard the NASA Solar Dynamics Observatory (SDO) , 2004, SPIE Asia-Pacific Remote Sensing.