Solar Flux Dependence of Upper Thermosphere Diurnal Variations: Observed and Modeled Journal Article uri icon

Overview

abstract

  • Upper thermosphere mass density over the declining phase of solar cycle; 23 are investigated using a day-to-night ratio (DNR) of thermosphere; properties as a metric to evaluate how much relative change occurs; climatologically between day and night. CHAMP observations from; 2002-2009, MSIS 2.0 output, and TIEGCM V2.0 simulations are analyzed to; assess their relative response in DNR. The CHAMP observations; demonstrate nightside densities decrease more significantly than dayside; densities as solar flux decreases. This causes a steadily increasing; CHAMP mass density DNR from two to four with decreasing solar flux. The; MSIS 2.0 nightside densities decrease more significantly than the; dayside, resulting in the same trend as CHAMP. TIEGCM V2.0 displays an; opposing trend in density DNR with decreasing solar flux due to dayside; densities decreasing more significantly than nightside densities. A; sensitivity analysis of the two models reveals the TIEGCM V2.0 to have; greater sensitivity in temperature to levels of solar flux, while MSIS; 2.0 displayed a greater sensitivity in mean molecular weight. The; pressure DNR from both models contributed the most to the density DNR; value at 400 km. As solar flux decreases, the two models’ estimate of; pressure DNR deviate appreciably and trend in opposite directions. The; TIEGCM V2.0 dayside temperatures during middle-to-low solar flux are too; cold relative to MSIS 2.0. Increasing the dayside temperature values by; about 50 – 100 K and decreasing the nightside temperature slightly; would bring the TIEGCM V2.0 into better agreement with MSIS 2.0 and; CHAMP observations.

publication date

  • November 11, 2022

has restriction

  • bronze

Date in CU Experts

  • November 22, 2022 6:47 AM

Full Author List

  • Thayer JP; Waldron ZC; Sutton EK

author count

  • 3

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