Simultaneous ground-based and in situ Swarm observations of equatorial F-region irregularities over Jicamarca

Abstract

Abstract. Ionospheric irregularities are a common phenomenon in the low-latitude ionosphere. They can be seen in situ as depletions of plasma density, radar plasma plumes, or ionogram spread F by ionosondes. In this paper, we compared simultaneous observations of plasma plumes by the Jicamarca Unattended Long-term Investigations of the Ionosphere and Atmosphere (JULIA) radar, ionogram spread F generated from ionosonde observations installed at the Jicamarca Radio Observatory (JRO), and irregularities observed in situ by Swarm in order to determine whether Swarm in situ observations can be used as indicators of the presence of plasma plumes and spread F on the ground. The study covered the years from 2014 to 2018, as this was the period for which JULIA, Swarm, and ionosonde data sets were available. Overall, the results showed that Swarm's in situ density fluctuations on magnetic flux tubes passing over (or near) the JRO may be used as indicators of plasma plumes and spread F over (or near) the observatory. For Swarm and the ground-based observations, a classification procedure was conducted based on the presence or absence of ionospheric irregularities. There was a strong consensus between ground-based observations of ionospheric irregularities and Swarm's depth of disturbance of electron density for most passes. Cases, where ionospheric irregularities were observed on the ground with no apparent variation in the in situ electron density or vice versa, suggest that irregularities may either be localized horizontally or restricted to particular height intervals. The results also showed that the Swarm and ground-based observations of ionospheric irregularities had similar local time statistical trends with the highest occurrence obtained between 20:00 and 22:00 LT. Moreover, similar seasonal patterns of the occurrence of in situ and ground-based ionospheric irregularities were observed with the highest percentage occurrence at the December solstice and the equinoxes and low occurrence at the June solstice. The observed seasonal pattern was explained in terms of the pre-reversal enhancement (PRE) of the vertical plasma drift. Initial findings from this research indicate that fluctuations in the in situ density observed meridionally along magnetic field lines passing through the JRO can be used as an indication of the existence of well-developed plasma plumes.

Statistical Characteristics of the Occurrence of ERI and FRI in the Equatorial Ionosphere With Observations of JULIA Radar

“…The statistical result is listed in Table 1. The occurrence number and proportion of different type F‐region echoes are similar with those in previous work (Aol et al., 2020; Hysell & Burcham, 2002), except that the proportion of bottomside echoes is higher than those previous results. In equinoxes, the topside echoes account for nearly half the observations on days with FRI.…”

Penetrating Electric Field Simulated by the MAGE and Comparison With ICON Observation

“…The vertical ion drift reverses at 18 MLT in typical conditions (e.g. Aol et al, 2020), when we should expect zero vertical ion drift. After consulting with the IVM team from U. of Texas at Dallas, we applied a shift based on the 6-min MLT median value at 18 MLT in the E × B meridional ion drift to bring the drift to zero at 18 MLT (blue line).…”

Statistical analysis of Low latitude Spread F at the American, Atlantic and Pacific sectors using digisonde observations

“…The other two plots also show huge plumes and corresponding intense spread F signatures in the ionograms. Aol et al, [2020] drew similar comparisons observing plasma plumes coinciding with spread F signatures on ionograms between the JULIA radar data and the JRO ionosonde.…”