The correlation between electron temperature and density in the topside ionosphere during 2006–2009

Abstract

Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions satellite data have been used to investigate the global relationship between electron density (Ne) and electron temperature (Te) in the topside ionosphere (~680 km) from 2006 to 2009. Te and Ne were negatively correlated in most of the low and middle latitude regions at ~10:30 solar local time (LT). In these regions, photoelectron heating of the electrons was balanced by cooling through collisions with the ions. The negative correlation became weaker at midlatitudes, due to the increasing influence of heat conduction. The correlation was negative in most seasons during the daytime except at high latitudes in the northern winter, where a positive correlation occurred. There were wave‐like longitudinal structures in Ne and Te around the geomagnetic equator, but they had different patterns in the day and the night. However, no obvious longitudinal variations in the correlation were associated with these structures. A positive correlation occurred near the magnetic equator at ~22:30 LT, which depended on thermal equilibrium between the electrons, ions, and neutrals. A negative correlation occurred at midlatitudes. Around the September equinox, at night around the magnetic equator, the positive correlation had a wider latitudinal range. At midlatitudes, a negative correlation occurred in smaller areas than it did around the March equinox. Around the December solstice the direct nighttime coupling between Ne and Te was weaker than it was around the June solstice. The negative correlation depends on the collisions between the electrons and the ions and the heating source.

A linear scale height Chapman model supported by GNSS occultation measurements

“…Also note that through Chapman model, i.e., equation , the scale height and temperature are correlated with the electron density, which is in good agreement with Su et al [, and references therein].…”

“…Nevertheless, this explanation just transfers to the temperature field the question regarding the linear relationship. One simple hypothesis for the linear temperature may be the unbalanced energy rate in the ionosphere following the explanations of Su et al []. Indeed, if the energy source (e.g., solar EUV flux) imposes on any dissipative process, the temperature may increase in the ionosphere.…”

Morning Overshoot of Electron Temperature as Observed by the Swarm Constellation and the International Space Station

“…We speculate that other "nonlocal" factors can also control morning overshoot, such as extra heat transport between the local plasma system and remote (e.g., conjugate) regions. Heating by conjugate (or remote) photoelectrons, as suggested by Oyama, Balan, et al (1996), and heat conduction due to magnetic inclination, as suggested by Stolle et al (2011) and Su et al (2015), may contribute to the nonlocal effects on electron temperature variations around morning overshoot. Further simulation studies are needed to elucidate the relative contributions of the above-mentioned factors.…”

How Often Do Thermally Excited 630.0 nm Emissions Occur in the Polar Ionosphere?

“…Therefore, the ionosphere is expected to be in good thermal contact Journal of Geophysical Research: Space Physics 10.1002/2017JA024744 whenever the electron density is high. Several studies have reported the expected negative correlation between the electron density and electron temperature in the ionosphere (e.g., Brace & Theis, 1978;Bilitza, 1975;Bilitza et al, 2007;Su et al, 2015).…”