HAO Colloquium - Qingyu Zhu, HAO

Improving Joule heating estimations in general circulation models of the upper atmosphere

 
Joule heating is an important energy source for the upper atmosphere and can significantly alter the upper atmosphere especially during geomagnetic storms. Hence, correctly estimating Joule heating is critical for space weather research and applications. General circulation models (GCMs) of the upper atmosphere are widely used in estimating Joule heating and simulating its consequences, and accurate Joule heating estimation depends on the accuracy of high-latitude electric field and electron precipitation specifications. Empirical models that reflect the average large-scale high-latitude electric field and electron precipitation distributions under certain conditions are often used in GCMs. However, it has been frequently found that the simulation cannot well reproduce observed phenomena when empirical models are used to specify high-latitude electrodynamical forcings. This could result from the deficiencies of empirical models which leads to inaccurate Joule heating estimations in GCMs. In this presentation, I will focus on two primary deficiencies of current high-latitude empirical models: 1) lack of electric field and electron precipitation variability and their correlations and 2) underestimation of soft (<1 keV) electron precipitation. For the first item, I will start with the statistical distributions of the electric field and electron precipitation variabilities along with their correlations on different spatial scales based on the data from the Dynamic Explorer 2 (DE-2) satellite. Then I will show the impact of electric field and electron precipitation variabilities on Joule heating based on the Global Ionosphere Thermosphere Model (GITM) simulations to highlight the significance of quantifying electric field and electron precipitation variabilities together with their correlations to Joule heating estimations. For the second item, I will introduce a recently developed empirical model, ASHLEY, to show how to improve soft electron precipitation in empirical models. In addition, I will present some GITM-ASHLEY simulation results along with data-model comparisons during intense geomagnetic storms to highlight the potential significance of improving soft electron precipitation specifications in improving the accuracy of GCMs.
Date and time: 
Wednesday, March 24, 2021 - 2:00pm to 3:00pm