Overview of the Rocket Experiment for Neutral Upwelling Sounding Rocket 2 (RENU2)

Abstract

The Rocket Experiment for Neutral Upwelling 2 (RENU2) rocket was launched on 13 December 2015 at 07:34 UT. The payload transited the cusp region during a neutral upwelling event, supported by a comprehensive set of onboard and ground-based instrumentation. RENU2 data highlight two important processes. One is that a proper understanding of neutral upwelling by Poleward Moving Auroral Forms (PMAFs) requires a treatment that mimics the quasiperiodic passage of a sequence of PMAFs. As a PMAF reaches a flux tube, its physical consequences must be determined including the residual history of effects from previous passages, implying that understanding such a process requires an accounting of the system hysteresis. Second, RENU2 observations suggest that neutral density enhancements driven by precipitation and/or Joule heating can be highly structured in altitude and latitude. In addition, timescales involving neutral dynamics suggest that the structuring must be slowly changing, for example, over the course of 10 to tens of minutes. 1.1. Altitudinal Structuring Additional modeling constraints have arisen from recent observations, those that show not only density enhancements but also depletions at higher altitudes. For example, the Streak satellite observed relative density depletions near the southern cusp in the altitude range 123-325 km when averaged over all orbits

RENU2 UV PMT Observations of the Cusp

“…As the following analysis of GLOW model results shows, however, N 2 likely contributes to the signal as the payload drops to altitudes below 300 km and must be considered in analysis of the RENU2 UV PMT data. Lessard et al (2019) describes several environmental precursors (Kervalishvili & Lühr, 2013 that indicated a cusp anomaly, or thermospheric neutral upwelling event, should have been present prior to the launch of RENU2, and a few pertinent details are related here. Southward interplanetary magnetic field is one of the precursors correlated with the cusp density anomalies, and the interplanetary magnetic field was weakly southward for about an hour prior to launch (B z ≈ −1.5 nT).…”

“…Solar wind speed and density were moderate to low both before and during the RENU2 event. Once B z turned southward, ground-based imagers and meridian scanning photometers (MSPs) began to track poleward moving auroral forms, or PMAFs (Lessard et al, 2019), as an indicator of the cusp.…”

“…A comprehensive set of remote and in situ observations by the RENU2 sounding rocket payload, along with supporting ground-based observations, has provided a view of the cusp at unprecedented levels of detail. A full mission summary is provided by Lessard et al (2019).…”

Transient Ionospheric Upflow Driven by Poleward Moving Auroral forms Observed During the Rocket Experiment for Neutral Upwelling 2 (RENU2) Campaign

“…These measurements, when compared to the speed of this PMAF, suggest that the PMAF was not locked into the slower background convection; a somewhat unusual situation (e.g., Kozlovsky & Kangas, ). A more comprehensive description and analysis of the data summarized in Figure is given in Lessard et al (). Here we focus on only the basic features necessary to set up a modeling study of transient behavior .…”

A New Technique for Estimating the Lifetime of Bursts of Electron Precipitation From Sounding Rocket Measurements

“…The Rocket Experiment for Neutral Upwelling‐2 (RENU2) rocket was launched north from Andoya Rocket Range in northern Norway with an apogee near 450 km over Svalbard at 0734 UT on 13 December 2015. The rocket was instrumented with a number of sensors including a three‐channel photometer to measure the auroral redline (OI(630 nm)) and greenline (OI (558 nm)), an electron spectrometer (EPLAS) to measure the electron spectrum form 5 eV to 14.6 keV (Lessard et al, ), and an electron retarding potential analyzer (ERPA; Cohen et al, ) that can measure ionospheric thermal electron temperature. On the down leg, at about 77°N latitude, the rocket entered a region of low‐energy electron precipitation, and based on ground‐based optical imaging, this region was associated with the presence of poleward moving auroral forms (PMAFs; Lessard et al, ).…”