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Titre du document / Document title

Forecasting the occurrence of ionospheric scintillation activity in the equatorial ionosphere on a day-to-day basis

Auteur(s) / Author(s)

ANDERSON David N. (1) ; REINISCH Bodo (2) ; VALLADARE Cesar (3) ; CHAU Jorge (4) ; VELIZ Oscar (4) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) University of Colorado/CIRES; NOAA/SEC, ETATS-UNIS
(2) Center for Atmospheric Research, University of Massachausetts, Lowell, MA, ETATS-UNIS
(3) Institute for Space Research, Boston College, Boston, MA, ETATS-UNIS
(4) Radio Observatorio de Jicamarca, Instituto Geofisico del Peru, Apartado 13-0207, Lima, PEROU

Résumé / Abstract

In the low-latitude ionospheric F region, ambient conditions after sunset are often conducive to the generation of small-scale plasma density structures by the Rayleigh-Taylor instability mechanism. Radio wave signals passing through these electron density irregularities experience amplitude fluctuations that lead to radio wave scintillation. The scintillation index, S4, is a measure of the severity of these amplitude fluctuations. It is well known that the occurrence frequency of scintillation activity depends on solar cycle, season, longitude and local time, with a large day-to-day variability. In this paper, we present the results of a continuing study that utilizes a ground-based digital sounder at the magnetic equator to provide a forecast of the subsequent occurrence of scintillation activity and a network of UHF and L-band receivers that measure the S4 index, on a night-to-night basis. To establish the forecasting relationship, observations were carried out in 1998 and 1999 in the Peruvian/Chilean longitude sector. The relationship between the magnitude of the vertical E x B drift velocity enhancement just after sunset as determined by the Jicamarca Digisonde and the magnitude of the S4 index subsequently observed an hour or two later by the scintillation receivers at Ancon, Peru and Antofagasta, Chile was established. In most cases at both UHF and L-band frequencies, this relationship is not linear, but there appears to be a threshold in E x B drift of ∼ 20 m/s. On nights when E x B drift was less than 20 m/s, the UHF S4 index generally was less than 0.5, while on nights when E x B drift exceeded 20 m/s, the S4 index was greater than 0.5. The day-to-day variability of this relationship will be presented and discussed. Since October 1, 2001, the Jicamarca Digisonde has been used to forecast the occurrence of UHF S4>0.5 or S4<0.5 on a night-to-night basis. The validity of the forecast is subsequently confirmed by UHF S4 observations at Ancon, Peru and Antofagasta, Chile. The resulting statistics for these nightly S4 forecasts from November 1, 2001 to April 30, 2002 will be presented and discussed.

Revue / Journal Title

Journal of atmospheric and solar-terrestrial physics    ISSN  1364-6826 

Source / Source

Congrès
40th Years of Equatorial Aeronomy Sparked by the Jicamarca Radio Observatory. Workshop, Lima , PEROU (05/2002)
2004, vol. 66, no 17 (164 p.)  [Document : 6 p.] (7 ref.), [Notes: Selected papers], pp. 1567-1572 [6 page(s) (article)]

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Kidlington, ROYAUME-UNI  (1997) (Revue)

Mots-clés anglais / English Keywords

South America

;

Spread F

;

Chile

;

Peru

;

Drift velocity

;

Night

;

Day to day variation

;

solar cycles

;

solar activity

;

Occurrence frequency

;

Scintillation index

;

fluctuations

;

electron density

;

Radio wave

;

Rayleigh Taylor instability

;

Plasma density

;

Sunset

;

Ionospheric F region

;

Low latitude

;

Equatorial ionosphere

;

scintillations

;

prediction

;

Mots-clés français / French Keywords

Amérique du Sud

;

F diffus

;

Chili

;

Pérou

;

Vitesse dérive

;

Nuit

;

Variation d'un jour à l'autre

;

Cycle solaire

;

Activité solaire

;

Fréquence apparition

;

Indice scintillation

;

Fluctuation

;

Densité électron

;

Onde radioélectrique

;

Instabilité Rayleigh Taylor

;

Densité plasma

;

Coucher soleil

;

Ionosphère région F

;

Basse latitude

;

Ionosphère équatoriale

;

Scintillation

;

Prévision

;

Mots-clés espagnols / Spanish Keywords

America del sur

;

F difuso

;

Chile

;

Perú

;

Velocidad deriva

;

Noche

;

Variación de una día al otro

;

Frecuencia aparición

;

Indice centelleo

;

Fluctuación

;

Densidad electrón

;

Onda radio

;

Inestabilidad Rayleigh Taylor

;

Densidad plasma

;

Puesta sol

;

Ionosfera región F

;

Baja latitud

;

Ionosfera ecuatorial

;

Previsión

;

Mots-clés d'auteur / Author Keywords

Scintillation

;

Equatorial ionosphere

;

Spread-F

;

Localisation / Location

INIST-CNRS, Cote INIST : 5742, 35400012065406.0050

Nº notice refdoc (ud4) : 16230693



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