12th International EISCAT Workshop, Kiruna, Sweden, 29 August - 3 September 2005

Active modification of the negative ion region (AMORE)

C.-F. Enell¹, A. Kero¹, E. Turunen¹, Th. Ulich¹, T. Bösinger², P. T. Verronen³, A. Seppälä³

¹Sodankylä Geophysical Observatory, Sodankylä, Finland,
²Department of Physical Sciences, University of Oulu, Oulu, Finland,
³Finnish Meteorological Institute, Helsinki, Finland.

Abstract

In the lower D region, i.e. the upper mesosphere, negative ions are important in the chemical balance between ions and neutrals. It is, however, difficult to measure the effects of negative ions directly with remote methods. We therefore suggest studying the negative-ion region indirectly by heating experiments and modelling with the Sodankylä Ion Chemistry (SIC) model.

The EISCAT Heating facility is capable of increasing the electron temperature in the D region up to ten times. This increases the rate of attachment of electrons to neutrals and thus the concentration of negative ions. Estimates using SIC show enhancements of the total negative ion density by up to 40% at the relevant altitudes.

Applicable experiments include:

• artificial periodic irregularities (API), a heating experiment using the standing waves caused by reflection of the heater wave from the F region,
• sporadic-E APIs, where we propose to utilise the reflection from sporadic E layers,
• observations by imaging riometers, such as IRIS in Kilpisjärvi, Finland, or ARIES at Ramfjordmoen, Norway, and
• monitoring of VLF radio wave propagation through the heater volume.

In this talk we show model calculations of the effects of heating in the negative ion region, and propose experimental setups.