| Journal: | Revista brasileira de geofisica |
| Database: | PERIÓDICA |
| System number: | 000335233 |
| ISSN: | 0102-261X |
| Authors: | Muralikrishna, Polinaya1 Vieira, Leandro Paulino1 |
| Institutions: | 1Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, Sao Paulo. Brasil |
| Year: | 2007 |
| Volumen: | 25 |
| Pages: | 139-145 |
| Country: | Brasil |
| Language: | Inglés |
| Document type: | Artículo |
| Approach: | Analítico, descriptivo |
| English abstract | Several sounding rockets carrying plasma diagnostic experiments were launched from the Brazilian rocket launching stations in Natal (5.9◦S, 35.2◦W Geog. Lat.) and Alcˆantara (2.31◦S, 44.4◦W Geog. Lat.). Langmuir Probes (LP) were used to measure the height profiles of electron density and electron temperature and High Frequency Capacitance (HFC) probes were used to measure electron density. The LP’s were also used to measure the amplitude of electron density fluctuations. A detailed study of the characteristic features of electron density irregularities in the scale size range of less than a meter to a few kilometres, observed by rocket-borne electron density probes under different ionospheric conditions is presented here. The main objective of these studies is the identification of these irregularities from the point of view of the dynamic and electrodynamic processes responsible for their generation. The existing theories of the Rayleigh Taylor Instability (RTI) mechanism applicable for conditions of the geomagnetic equatorial ionosphere over Brazil are critically examined in the light of the observations. The observed characteristics of the irregularities during four rocket launches are compared with the theoretically expected characteristics. These results confirm the operation of a cascade process that is responsible for the generation of a wide spectrum of irregularities. The large-scale irregularities are first generated probably by the RTI mechanism that creates conditions favourable for the operation of the Cross-Field (CFI) or the Gradient Drift Instability (GDI) mechanism. From the k-spectra of irregularities it is possible to obtain the spectral index n corresponding to the height chosenarities generated by the |
| Portuguese abstract | Varios foguetes de sondagem carregando experimentos de diagnostico de plasma foram lancados dos centros Brasileiros de lancamento de foguetes em Natal (5.9◦S, 35.2◦O Lat. Geog.) e Alcantara (2.31◦S, 44.4◦O Lat. Geog.). Sondas de Langmuir (LP) foram usadas para medir os perfis de densidade e temperatura do plasma e Sondas Capacitivas em Alta Frequencia (HFC) foram usadas para medir a densidade eletronica. As LP’s foram usadas tambem para medir a amplitude das flutuacoes de densidade eletrˆonica. Um estudo detalhado dos aspectos caracteiısticos das irregularidades de densidade eletronica da escala de menos de um metro a alguns quilometros, observadas pelas sondas de densidade eletronica a bordo dos foguetes sob condicoes diferentes da ionosfera ´e apresentado aqui. O objetivo principal destes estudos e a identificacao destas irregularidades do ponto de vista dos processos dinamicos e eletrodinˆamicos responsaveis pela geracao delas. As teorias existentes do mecanismo de instabilidade de Rayleigh-Taylor aplicaveis para as condicoes da ionosfera equatorial geomagn´etica sobre Brasil, sao analisadas criticamente, a luz das observacoes. As caracterısticas observadas das irregularidades durante os quatro lanc¸amentos de foguetes foram comparadas com as caracterısticas esperadas das teorias. Estes resultados confirmam a operacao do processo cascata, que e responsavel pela geracao de um largo espectro de irregularidades. As irregularidades de larga escala sao geradas primeiras, provavelmente pelo mecanismo RTI que cria condic¸ oes favoraveis pela operacao do mecanismo de Instabilidade “Cross-Field” (CFI) ou “Gradient-Drift” (GDI). A partir dos espectros-k das irregularidades e possiıvel obter o ındice espectral n correspondendo a uma altura escolhida. Na maioria dos casos o indice espectral estimado esta em boa concordancia com os publicados |
| Disciplines: | Geociencias |
| Keyword: | Ciencias de la atmósfera, Geofísica, Ionósfera, Plasma, Región F, Inestabilidad de Rayleigh-Taylor, Cohetes, Brasil |
| Keyword: | Earth sciences, Atmospheric sciences, Geophysics, Ionosphere, Plasma, F region, Rayleigh-Taylor inestability, Rockets, Brazil |
| Full text: | Texto completo (Ver PDF) |
