Abstract
AbstractWe present an overview of the ionospheric conditions during the launch of the Investigation of Cusp Irregularities 3 (ICI‐3) sounding rocket. ICI‐3 was launched from Ny‐Ålesund, Svalbard, at 7:21.31 UT on 3 December 2011. The objective of ICI‐3 was to intersect the reversed flow event (RFE), which is thought to be an important source for the rapid development of ionospheric irregularities in the cusp ionosphere. The interplanetary magnetic field was characterized by strongly negative Bz and weakly negative By. The EISCAT Svalbard radar (ESR) 32‐m beam was operating in a fast azimuth sweep mode between 180° (south) and 300° (northwest) at an elevation angle of 30°. The ESR observed a series of RFEs as westward flow channels that were opposed to the large‐scale eastward plasma flow in the prenoon sector. ICI‐3 intersected the first RFE in the ESR field of view and observed flow structures that were consistent with the ESR observations. Furthermore, ICI‐3 revealed finer‐scale flow structures inside the RFE. The high‐resolution electron density data show intense fluctuations at all scales throughout the RFE. The ionospheric pierce point of the GPS satellite PRN30, which was tracked at Hornsund, intersected the RFE at the same time. The GPS scintillation data show moderate phase scintillations and weak amplitude scintillations. A comparison of the power spectra reveals a good match between the ground‐based GPS carrier phase measurements and the spectral slope of the in situ electron density data in the lower frequency range. It demonstrates the possibility of modelling GPS scintillations from high‐resolution in situ electron density data.
Highlights
A reversed flow event (RFE) is a mesoscale flow structure in the cusp ionosphere, which refers to east‐west elongated segments of the enhanced ion flow in the direction opposite to the background plasma flow (Rinne et al, 2007)
From the fast azimuth sweeps of the EISCAT Svalbard radar (ESR) in the winter cusp ionosphere, it was found that RFEs never formed simultaneously in pairs, and they cannot be explained with the symmetric Southwood flux transfer event (FTE) model (Southwood, 1987)
Since we do not have in situ magnetic field data from the ICI‐3, which can derive the field‐aligned currents, nor ground‐based optical auroral measurements, which can monitor the exact location of auroral arcs, we can only infer the observational geometry from the other data sets that we have presented and previous literature (Moen et al, 2008; Rinne et al, 2007)
Summary
A reversed flow event (RFE) is a mesoscale flow structure in the cusp ionosphere, which refers to east‐west elongated segments of the enhanced ion flow in the direction opposite to the background plasma flow (Rinne et al, 2007). The large flow shears associated with the RFE led Carlson et al (2007) to propose a two‐step process to explain the observed rapid development of cusp irregularities. In this new framework, the KHI first works on the cusp‐entering plasma to quickly produce mesoscale plasma. We focus on characterizing plasma irregularities associated with the RFE on 3 December 2011, by combining in situ ICI‐3 sounding rocket and ground‐based instruments Both the ground‐based GPS scintillation data and the in situ electron density data are widely used to study ionospheric irregularities (Basu et al, 1988; Kelley et al, 1980). The current study benefits from a very high‐resolution electron density data from the ICI‐3 sounding rocket and the GPS scintillation data, which gives us an opportunity to study plasma irregularities using two different observational techniques and investigate the relation between the cause (ionospheric irregularities) and the scintillation effect on the ground
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