An overview of type-3 radar auroral research: Basic observational properties and new interpretation propositions

Physics

Scientific paper

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

2

Auroral Arcs, Auroral Echoes, Auroral Electrojets, Auroral Zones, Backscattering, E Region, Plasma Waves, Auroral Spectroscopy, Density Distribution, Doppler Radar, Electric Fields, Spectral Signatures

Scientific paper

Type-3 radio auroral backscatter is recognized by its narrow Doppler spectrum centered at sub-ion acoustic velocities and its spectrum stability in both space and time. Originally this scatter was attributed to electrostatic ion cyclotron waves in the upper E-region, a proposition which has been disproved by experiment. Today, we know that these echoes are due to plasma waves generated inside the electrojet where ions are unmagnetized. Also, whenever type-3 and type-1 (Farley-Bunemann) echoes are observed simultaneously they have the same Doppler polarity which suggests a direct role for the ambient electric field in type-3 generation under some critical conditions in the plasma. Moreover, there are results showing that type-3 echoes originate in the vicinity of optical auroral arcs. In this paper we use past and new data to evaluate and summarize first the basic observational properties of type-3 echoes and then take a critical view of newly proposed interpretation ideas. Mainly, we focus on the role of sharp, destabilizing plasma density gradients in reducing the phase velocity of Farley-Bunemann waves to sub-ion acoustic speeds. This examined in the framework of the linear theory and also of recent non-linear theory of spectrum broadening due to turbulence induced by mode-coupling. Further, we reexamine some published data in an attempt to evaluate the hypothesis that the required sharp density gradients can exist at the edges of discrete auroral arcs. We conclude that the existing evidence in favor of the plasma gradient hypothesis is necessary but not sufficient. Also, with mechanism it would be difficult to explain the preferential type-3 velocities which are independent of radar frequency, and the stability of the Doppler spectrum. At this stage of research, there is a need for well-designed, high-resolution, multi-instrument experiments in order to obtain an integrated observational test of the current interpretation propositions.

No associations

LandOfFree

Say what you really think

Search LandOfFree.com for scientists and scientific papers. Rate them and share your experience with other people.

Rating

An overview of type-3 radar auroral research: Basic observational properties and new interpretation propositions does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with An overview of type-3 radar auroral research: Basic observational properties and new interpretation propositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and An overview of type-3 radar auroral research: Basic observational properties and new interpretation propositions will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFWR-SCP-O-1818426

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.