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Title: A STUDY OF SOLAR PHOTOSPHERIC TEMPERATURE GRADIENT VARIATION USING LIMB DARKENING MEASUREMENTS

Abstract

The variation in area of quiet magnetic network measured over the sunspot cycle should modulate the spatially averaged photospheric temperature gradient, since temperature declines with optical depth more gradually in magnetic flux tube atmospheres. Yet, limb darkening measurements show no dependence upon activity level, even at an rms precision of 0.04%. We study the sensitivity of limb darkening to changes in area filling factor using a 3D MHD model of the magnetized photosphere. The limb darkening change expected from the measured 11-year area variation lies below the level of measured limb darkening variations, for a reasonable range of magnetic flux in quiet network and internetwork regions. So the remarkably constant limb darkening observed over the solar activity cycle is not inconsistent with the measured 11-year change in area of quiet magnetic network. Our findings offer an independent constraint on photospheric temperature gradient changes reported from measurements of the solar spectral irradiance from the Spectral Irradiance Monitor, and recently, from wavelength-differential spectrophotometry using the Solar Optical Telescope aboard the HINODE spacecraft.

Authors:
 [1];  [2]
  1. National Solar Observatory, Boulder, CO 80303 (United States)
  2. 192 Willow Road, Nahant, MA 01908 (United States)
Publication Date:
OSTI Identifier:
22663824
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; ACTIVITY LEVELS; COMPUTERIZED SIMULATION; LIMBS; LIMITING VALUES; MAGNETIC FLUX; MAGNETOHYDRODYNAMICS; PHOTOSPHERE; RADIANT FLUX DENSITY; SENSITIVITY; SOLAR CYCLE; SPACE VEHICLES; SPECTROPHOTOMETRY; SUN; SUNSPOTS; TELESCOPES; TEMPERATURE GRADIENTS; WAVELENGTHS

Citation Formats

Criscuoli, Serena, and Foukal, Peter. A STUDY OF SOLAR PHOTOSPHERIC TEMPERATURE GRADIENT VARIATION USING LIMB DARKENING MEASUREMENTS. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/1/99.
Criscuoli, Serena, & Foukal, Peter. A STUDY OF SOLAR PHOTOSPHERIC TEMPERATURE GRADIENT VARIATION USING LIMB DARKENING MEASUREMENTS. United States. doi:10.3847/1538-4357/835/1/99.
Criscuoli, Serena, and Foukal, Peter. Fri . "A STUDY OF SOLAR PHOTOSPHERIC TEMPERATURE GRADIENT VARIATION USING LIMB DARKENING MEASUREMENTS". United States. doi:10.3847/1538-4357/835/1/99.
@article{osti_22663824,
title = {A STUDY OF SOLAR PHOTOSPHERIC TEMPERATURE GRADIENT VARIATION USING LIMB DARKENING MEASUREMENTS},
author = {Criscuoli, Serena and Foukal, Peter},
abstractNote = {The variation in area of quiet magnetic network measured over the sunspot cycle should modulate the spatially averaged photospheric temperature gradient, since temperature declines with optical depth more gradually in magnetic flux tube atmospheres. Yet, limb darkening measurements show no dependence upon activity level, even at an rms precision of 0.04%. We study the sensitivity of limb darkening to changes in area filling factor using a 3D MHD model of the magnetized photosphere. The limb darkening change expected from the measured 11-year area variation lies below the level of measured limb darkening variations, for a reasonable range of magnetic flux in quiet network and internetwork regions. So the remarkably constant limb darkening observed over the solar activity cycle is not inconsistent with the measured 11-year change in area of quiet magnetic network. Our findings offer an independent constraint on photospheric temperature gradient changes reported from measurements of the solar spectral irradiance from the Spectral Irradiance Monitor, and recently, from wavelength-differential spectrophotometry using the Solar Optical Telescope aboard the HINODE spacecraft.},
doi = {10.3847/1538-4357/835/1/99},
journal = {Astrophysical Journal},
number = 1,
volume = 835,
place = {United States},
year = {Fri Jan 20 00:00:00 EST 2017},
month = {Fri Jan 20 00:00:00 EST 2017}
}