About DELTA campaign

Introduction

Large-scale atmospheric circulation in the high latitude thermosphere has been investigated by many modeling studies and satellite observations. Compared to the large-scale circulation, meso-scale (1-1000 km) phenomena such as the thermospheric response to auroral disturbance are not well understood. In recent years, measurements of neutral winds by the chemical release technique in the high latitude thermosphere have been conducted, and thereby strong winds and wind shears are found to exist. However, a cause of the wind structure particularly in the vertical direction is not elucidated mainly because of uncertainty in the related parameters, which are necessary for the modeling study. Simultaneous observations of the neutral atmospheric temperature, the neutral wind, and the auroral energy input are necessary for further understanding of the thermospheric response to the auroral disturbance.

"DELTA" is the acronym for "Dynamics and Energetics of the Lower Thermosphere in Aurora". In another sense, this campaign is a collaboration among three instruments, a sounding rocket, the EISCAT radar, and ground-based optical instruments.

Science Objectives and Instrumentation

Main objective of this rocket campaign is to study the dynamics and energetics in the lower thermosphere accompanied with the auroral activity. In this campaign, rocket-borne instruments and two remote (ground-based) facilities will be simultaneously operated as explained below:

  1. Measurements of neutral atmospheric temperature and density, the auroral emission rate, and the electron temperature and density by the rocket-borne instruments
  2. Measurements of the ion drift, temperature and density as well as electron temperature and density by EISCAT radar
  3. Measurements of the neutral wind and temperature by the ground-based Fabry-Perot Interferometer (FPI)

A vertical profile of the neutral temperature/density and the auroral emission rate were measured by the sounding rocket while the ion drift and the neutral wind were provided by the EISCAT radar and the FPI observations, respectively. A list of the rocket-borne and ground-based instruments is shown below.

List of instruments and observation altitude. Click on the image to enlarge.

Rocket Launch and Geophysical Condition

Japanese sounding rocket "S-310-35" was successfully launched from Andøya Rocket Range in Norway, at 00:33 UT on 13 December 2004. The apex height was about 140 km. Other ground-based instruments are located in the north of Scandinavian Peninsula, as shown below.

Map of the launch site and observatories. Click on the image to enlarge. The dotted line in the map shows the trajectory projected into the Earth surface.

The EISCAT radar observed an enhancement of the electron density due to ionization by the precipitating electrons for more than half an hour before. The magnetogram data also indicate the auroral jet current was flowing over the area. The all-sky cameras obtained images, which shows that several bright auroral arcs were passing through the sky during the flight of the rocket.