Semiannual and solar activity variations of daytime plasma observed by DEMETER in the ionosphere‐plasmasphere transition region

Abstract

Using the plasma data of Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite and the NRLMSISE‐00 atmospheric model, we examined the semiannual and solar activity variations of the daytime plasma and neutral composition densities in the ionosphere‐plasmasphere transition region (~670–710 km). The results demonstrate that the semiannually latitudinal variation of the daytime oxygen ions (O+) is basically controlled by that of neutral atomic oxygen (O), whereas the latitude distributions of the helium and hydrogen ions (He+ and H+) do not fully depend on the neutral atomic helium (He) and hydrogen (H). The summer enhancement of the heavy oxygen ions is consistent with the neutral O enhancement in the summer hemisphere, and the oxygen ion density has significantly the summer‐dense and winter‐tenuous hemispheric asymmetry with respect to the dip equator. Although the winter enhancements of the lighter He+ and H+ ions are also associated with the neutral He and H enhancements in the winter hemisphere, the high‐density light ions (He+ and H+) and electrons (e−) mainly appear at the low and middle magnetic latitudes (|λ| < 50°). The equatorial accumulations of the light plasma species indicate that the light charged particles (He+, H+, and e−) are easily transported by some equatorward forces (e.g., the magnetic mirror force and centrifugal force). The frequent Coulomb collisions between the charged particles probably lead to the particle trappings at different latitudes. Moreover, the neutral composition densities also influence their ion concentrations during different solar activities. From the low‐F10.7 year (2007–2008) to the high‐F10.7 year (2004–2005), the daytime oxygen ions and electrons increase with the increasing neutral atomic oxygen, whereas the daytime hydrogen ions tend to decrease with the decreasing neutral atomic hydrogen. The helium ion density has no obvious solar activity variation, suggesting that the generation (via the neutral He photoionization) and loss (via the charge exchange with neutral nitrogen N2 and/or the recombination with electrons) of the daytime He+ ions are comparable during different solar activities.

Source of the low‐altitude hiss in the ionosphere

“…In the winter hemisphere, during periods of low solar activity the relative contributions of H + and He + to the topside ion density will be increased. Furthermore, the contributions of He + is a strong function of latitude with a local peak near 20° magnetic latitude [ Li et al , ]. Thus, further evidence of the trapping mechanisms described here may be found by examining the relationships between the frequency range of the emission and the local ion composition in the ionosphere.…”

Large‐Scale Depletion of Nighttime Oxygen Ions at the Low and Middle Latitudes in the Winter Hemisphere

“…The chemical production ( S ) and loss ( L ) of plasma mainly result from photoionization and/or charge exchange reactions (Li et al., 2015; Waldrop et al., 2006). The plasma transports (Velocity V ) can be driven by neutral wind and/or E × B ( E is an eastward electric field vector and B is geomagnetic field vector) (He et al., 2009, 2011; Lu et al., 2013).…”

“…Interestingly, the density ([O]) of neutral atomic oxygen is also maximum at the middle and high latitudes (| λ | ≥ 50°) of summer hemisphere (Figures 6a and 6b). This is perhaps due to the heating expansion of the dense atmosphere at lower altitudes (Li et al., 2015). Like the daytime, the enough atomic oxygen in the polar‐day region can be ionized to more oxygen ions (O + hv → O + + e − ).…”

“…One of the typically irregular structures is the nighttime midlatitude trough with a significant decrease in plasma electron density [e − ] or total electron content at middle latitudes (∼50°–70°) (Chen et al., 2018; He et al., 2011; Lee et al., 2011; Liu et al., 2021; Rodger, 2008; Xiong et al., 2013). Besides the nighttime midlatitude trough, plasma density also decreases in the South Atlantic Magnetic Anomaly (SAMA) in the topside ionosphere (Horvath & Lovell, 2009b; Li et al., 2011, 2015). The steep density gradients in irregular structures can deteriorate the accuracy of the GPS positioning (Wanninger, 1993) and cause the Doppler and delay spread of HF signals (Stocker & Warrington, 2011).…”

The Effect of Hot Protons on Magnetosonic Waves Inside and Outside the Plasmapause: New Observations and Theoretic Results

“…From the outer edge of plasmapause to its inner edge, the passing of the lower frequency MS waves and the damping of the higher frequency MS waves are inconsistent with the absorption or reflection of lower frequency electromagnetic waves on the bottom of ionosphere. Different from the ionosphere containing Journal of Geophysical Research: Space Physics 10.1002/2017JA024676 cold plasmas and neutral compositions (Li et al, 2015), the plasmasphere also contains a lot of hot ions and electrons, as indicated by Figures 1c and 3c. These hot plasmas in different velocity distributions can cause the plasma wave growth or damping through cyclotron resonance or Landau resonance (Horne et al, 2000).…”