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, 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 when all the 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 irregularity structures. There was a strong consensus between ground-based observations of irregularity structures and Swarm's depth of disturbance of electron density for most passes. Cases, where irregularity structures 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. Also, similar seasonal patterns of occurrence of in situ and ground-based ionospheric irregularities were observed with the highest percentage occurrence in December Solstice and Equinoxes and low occurrence in 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 of in situ density observed meridionally along magnetic field lines passing through JRO can be used as an indication of the existence of well-developed plasma plumes.

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).…”

Ionospheric Nighttime F‐Region Irregularities During Geomagnetically Quiet Conditions as Observed With 205 MHz VHF Radar at an Equatorial Trough Station, Cochin

“…Aol et al. (2020) reported the simultaneous validation of JULIA radar and ionosonde with the Swarm satellites indicating that Swarm data can be used as a better tool for probing ionospheric events. Their observations spanning from 2014 to 2018 showed an extensive comparison of ionospheric irregularities from radar with the Swarm data.…”