Ionospheric plasma caves under the equatorial ionization anomaly

Abstract

.[1] This paper reports the existence of plasma caves, minima in the electron density located at 5-10 to the magnetic equator, in the bottomside ionosphere based on electron densities simulations from the International Reference Ionosphere (IRI-2007) and clear evidences given by plasma density and drift measurements of the Dynamic Explorer 2 (DE 2) satellite during [1981][1982][1983]. The IRI simulations suggest plasma caves as daytime features (08:00-19:00 LT; length of 18,158 km in the longitudinal direction), that range from the E region up to about 300 km altitude with 10 (or 1100 km) width in the latitudinal direction. In situ measurements of the ion and electron densities probed by the DE 2 confirm the existence of the plasma caves at low altitudes of the EIA ionosphere. The unexpected downward and upward (or weakly and strongly upward) ion drifts at the magnetic equator and the two off equators seem to play an important role responsible for the plasma cave formation.

Theoretical study of the ionospheric plasma cave in the equatorial ionization anomaly region

“…[] and Lee et al . [], the depletion belt in the longitude‐latitude map and the two cave‐shaped depletions in the altitude‐latitude map are features of the plasma cave. The plasma caves structure is well developed around 14:01 LT with around 15° width away from the magnetic equator and disappears around 18:00 LT (not shown).…”

“…Lee et al . [] used satellite in situ observations from Dynamics Explorer 2 (DE‐2) as well as outputs from the empirical International Reference Atmosphere 2007 model and confirmed the existence of plasma caves. They found that the caves are most likely to occur at ~11 LT and 14–17 LT around 0°E–120°E longitudes during the equinoxes.…”

“…The simulations carried out here have seasonal conditions corresponding to day of year 073 (14 March) 2001, near the spring equinox. Selection of this time period is based on DE‐2 observations showing that the plasma cave feature occurs more frequently around spring equinox [ Lee et al ., ]. The geophysical parameters used in the simulation are F 10.7 = 140.7, F 10.7 A = 166.8, and Ap = 7.…”

The International Reference Ionosphere – Status 2013

“…While theoretical models still struggle to include this phenomenon in their modeling framework, IRI already includes a smoothed version of this phenomenon (McNamara et al, 2010); a smoothing effect is to be expected since IRI is based on monthly averages. Other examples are the midlatitude evening anomaly (Weddell Sea anomaly) observed by the Super Dual Auroral Radar Network (SuperDARN) radars that is well captured by IRI (de Larquier et al, 2011) and the occurrence of ionospheric plasma caves under the Equatorial Ionization Anomaly (EIA) (Lee et al, 2012).…”

The fast development of solar terrestrial sciences in Taiwan

“…It not only predicts the growth of the X-and O-mode waves but is also an efficient mechanism for direct amplification of waves. This mechanism have also been applied to the generation of Z-and whistler-mode waves, in which these waves can, in turn, further accelerate electrons from a few hundreds of keV to MeV (Lee et al 2012a(Lee et al , 2013a.…”