The Relationship Between Large Scale Thermospheric Density Enhancements and the Spatial Distribution of Poynting Flux

Abstract

Large thermospheric neutral density enhancements in the cusp region have been examined for many years. The Challenging Minisatellite Payload (CHAMP) satellite for example has enabled many observations of the perturbation, showing that it is mesoscale in size and exists statistically over solar cycle timescales. Further studies examining the relationship with magnetospheric energy input have shown that fine‐scale Poynting fluxes are associated with the density perturbations on a case‐by‐case basis, whilst others have found that mesoscale downward fluxes also exist in the cusp region statistically. In this study, we use nearly 8 years of the overlapping Super Dual Auroral Radar Network and Active Magnetosphere and Planetary Electrodynamics Response Experiment datasets to generate global‐scale patterns of the high‐latitude and height‐integrated Poynting flux into the ionosphere, with a time resolution of 2 min. From these, average patterns are generated based on the interplanetary magnetic field orientation. We show the cusp is indeed an important feature in the Poynting flux maps, but the magnitude does not correlate well with statistical neutral mass density perturbations observed by the CHAMP satellite on similar spatial scales. Importantly, the lack of correlation between mesoscale height‐integrated Poynting fluxes and the cusp neutral mass density enhancement gives possible insight into other processes that may account for the discrepancy, such as energy deposition at finer scale sizes or at higher altitudes than captured.

Ionospheric Energy Input in Response to Changes in Solar Wind Driving: Statistics From the SuperDARN and AMPERE Campaigns

“…The superposed epoch analysis presented in this study has shown the reconfiguration process of high-latitude PF in response to sign transitions of the IMF B z component, with a two-minute temporal resolution and a spatial resolution of a few hundred kilometers. The PF patterns shown in this study have a similar general morphology to those in previous studies of PF/Joule heating (e.g., Cosgrove et al, 2014;Knipp et al, 2021;Weimer, 2005) as well as the initial manuscript that introduces this data set (Billett et al, 2021). In short, PF is mostly dissipated around the auroral electrojets, as well as around the dayside cusp at ∼80° latitude.…”

“…Therefore, there is little uncertainty in the parallel field condition for SuperDARN-AMPERE derived PF using Equation 1. Previously, a data set of PF patterns for the northern hemisphere ionosphere has been generated for the entire overlapping AMPERE-SuperDARN datasets between 2010 and 2017 using Equation 1, which has been shown to be consistent with several models and observations (Billett et al, 2021).…”

Hemispheric Asymmetries in Poynting Flux Derived From DMSP Spacecraft

“…This may be interpreted as an extension of Alfvenic behavior into what has previously been considered as the "quasi-static" regime (see Pakhotin et al, 2021). We also find persistent PF in the near-cusp region at a higher intensity than that reported by Billett et al (2021). For low levels of geomagnetic activity (∼80% of the time in this study) the near-cusp PF dominates the auroral zone PF.…”

“…Figures 2 and 3 indicate strong near-cusp PF in the NH (e.g., Olsson et al, 2004. ) with higher intensities than in Billett et al (2021). This feature also appears in the SH cusp where satellite coverage exists, although direct comparison is not possible due to limited coverage.…”

Using Temporal Relationship of Thermospheric Density With Geomagnetic Activity Indices and Joule Heating as Calibration for NRLMSISE‐00 During Geomagnetic Storms

“…However, the original NRLMSISE-00 model vastly underestimates GRACE density observations in the cusp region, especially to the density peaks (Figures 7c and 7d). Billett et al (2021) revealed the impact of solar-terrestrial energy on thermosphere, such as Poynting flux (PF) mainly depositing in the cusp regions. Even more, Knipp et al (2021) concluded that Poynting flux in the cusp region often exceeds the energy intensity in the auroral zone.…”