Observations of the upper frequency cutoffs of the auroral kilometric radiation

Details Observations of the upper frequency cutoffs of the auroral kilometric radiation Observations of the upper frequency cutoffs of the auroral kilometric radiation

Sep 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998angeo..16.1097h&link_type=abstract

Annales Geophysicae, vol. 16, Issue 9, pp.1097-1104

Physics

7

Scientific paper

Intense auroral kilometric radiation (AKR) is being frequently observed with POLRAD from the Auroral Probe (Interball-2). Observations of the abrupt upper frequency cutoffs (UFCs) in the spectra of AKR are reported. The UFCs can be observed at a frequency range from 300 to 700 kHz, corresponding to AKR generation altitudes from approximately 4800 to 2100 km, and are distributed in magnetic local time (MLT) hours similarly to the AKR events, with a maximum at 1 h MLT. The observed frequency extent of the UFCs is leq12 kHz, and is often determined by the instrumental resolution (4 kHz). It is suggested that the UFC may be associated with an abrupt switching on of the generation mechanism, when the electron density becomes sufficiently low inside a plasma depletion at an altitude where the ratio of fpe/fce crosses some threshold value. The steepness of the UFCs can imply a non-linear process of generation. The estimated distance of the e-folding field aligned wave amplification is between 3 and 8 km. The UFCs are sometimes, though very seldom (<10%), accompanied by narrow band (less than 4 kHz) ridges of radiation observed at the cutoff frequency. They are smoothly drifting in frequncy for several minutes. The power density of radiation in the ridge can be up to 2 orders of magnitude stronger than in the accompanying wide band emission of AKR. The ridge at UFC can imply either energy concentration at the source bottom, or focusing, if specific conditions for the escape of the radiation are assumed.

Affiliated with

Also associated with

No associations

Rating

Observations of the upper frequency cutoffs of the auroral kilometric radiation 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 Observations of the upper frequency cutoffs of the auroral kilometric radiation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Observations of the upper frequency cutoffs of the auroral kilometric radiation will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-810837