Upper thermospheric responses to forcing from above and below during 1–10 April 2010: Results from an ensemble of numerical simulations

Abstract

In this report we examine the spatial and temporal variability of the quiescent thermosphere leading up to and after the 5 April 2010 geomagnetic disturbance. We attribute the dominant driver of this variability to a combination of tides generated in situ and in the troposphere, stratosphere, and mesosphere. We identify nonmigrating tidal signatures attributable to the latter source that are ubiquitous, persistent, and significant at all thermospheric latitudes. Further, these perturbations underlie the upper atmospheric response to solar geomagnetic disturbances and are measurably altered, along with their migrating counterparts, during the storm. Our investigation is centered on a series of National Center for Atmospheric Research thermosphere-ionosphere-mesosphere-electrodynamics general circulation model simulations during 1-10 April 2010, including an optimal simulation with lower boundary forcing based on Modern-Era Retrospective Analysis for Research and Application reanalysis data and upper boundary forcing based on satellite and ground magnetometer measurements and the Assimilative Mapping of Ionospheric Electrodynamics procedure and three diagnostic simulations. The differences between the optimal and diagnostic simulations allow us to quantify thermospheric variability attributable to solar geomagnetic forcing and dynamical effects propagating into the thermosphere from below. We find that they can be comparable at high latitudes for some nonmigrating tidal components.

Scientific challenges in thermosphere-ionosphere forecasting – conclusions from the October 2014 NASA JPL community workshop

“…Figure 1 exemplifies some of the neutral temperature variability that characterized the results from their TIME-GCM simulations. These latitude-longitude temperature maps are 12 UT snapshots at 340 km and illustrate the magnitude of some of the TIME-GCM temperature variability reported by Hagan et al (2015). These maps complement and extend the results shown in Figure 2 of their report.…”

“…While the temperatures in the middle right panel capture salient features of the temperatures that are driven by the geomagnetic disturbance on April 5 (top right), there are also notable differences between the top and middle right panels that are attributable to differences in lowerboundary forcing. Figure 1 thus underscores the conclusions of Hagan et al (2015) that the thermospheric response to any solar geomagnetic storm is predicated on the prevailing undisturbed thermospheric conditions. The global-scale spatial and temporal variability of these prevailing conditions is largely characterized by an aggregate of tidal and planetary wave oscillations, a significant component of which originates below the T-I system.…”

“…TIME-GCM runs driven by AMIE are used in the work described next as the basis for exploring the role of lower-boundary forcing in thermospheric variability during geomagnetic disturbances. Hagan et al (2015) diagnosed an ensemble of TIME-GCM simulations for the April 1-10, 2010 period to investigate the spatial and temporal variability of quiescent thermospheric temperature and zonal wind leading up to, during, and subsequent to the April 5 disturbance. Figure 1 exemplifies some of the neutral temperature variability that characterized the results from their TIME-GCM simulations.…”

The Effects of Vertically Propagating Tides on the Mean Dynamical Structure of the Lower Thermosphere

“…Similar types of scenarios to those described above for varying solar conditions could be envisioned for geomagnetically active periods, as tidal amplitudes, their dissipative characteristics, and their contribution to the mean zonal circulation of thermosphere are known to vary compared to geomagnetically quite periods (e.g., Hagan et al, 2015). Similar types of scenarios to those described above for varying solar conditions could be envisioned for geomagnetically active periods, as tidal amplitudes, their dissipative characteristics, and their contribution to the mean zonal circulation of thermosphere are known to vary compared to geomagnetically quite periods (e.g., Hagan et al, 2015).…”

Estimation of energy budget of ionosphere-thermosphere system during two CIR-HSS events: observations and modeling

“…We would like to note that ''driving IT from below'' in several instances can cause effects comparable to external driving, e.g. (Hagan et al 2015) and requires detailed analysis for individual events (see also Sect. 4).…”