A study of geoeffective magnetic clouds in the interplanetary medium / Estudo de nuvens magneticas geoefetivas no meio interplanetario

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Magnetic clouds are interplanetary structures whose origins are related to Coronal Mass Ejections (CME). Their features are: strong magnetic field intensity (typically > 10nT4), a large rotation in the magnetic field angle as the cloud crosses the spacecraft, low proton temperature and b5 values (~0.1). For a set of previously published magnetic cloud events and another set of clouds identified in the whole year of 1979 we present a study of plasma and magnetic field parameters. We have shown the existence of a relationship between the peak magnetic field strength and peak velocity value of the cloud, with a tendency that clouds which move at higher speeds also possess higher core magnetic field strengths. There is also an indication that this relationship is peculiar to magnetic clouds, whereas other types of non-cloud driver gas, or ICME6, events do not seam to show a similar relationship. Both parameters, velocity and magnetic field strength, are related to Magnetic Storms. It is also addressed the interaction between magnetic clouds and other features in the interplanetary medium by calculating the Total Static Pressure, Magnetic plus Thermal, and the Dynamic Pressure relative to other structures surrounding the cloud, investigating their possible relation to magnetic cloud field enhancement. This work contributes to: (1) Space Weather Forecasting, through the calculation of the magnetic cloud field strengths by knowing their velocities (the latter can be remotely measured by sequences of coronograph images); (2) the study of the relation between magnetic clouds and magnetic storms; and (3) the study of the interaction between magnetic clouds and other interplanetary structures surrounding it. 4 nT = nano Tesla = 10-9 T = 10-5 gauss; Magnetic Induction. 5 b = (thermal pressure)/(magnetic pressure) = (NkT)/(B2/8p) 6 ICME Interplanetary Coronal Mass Ejections.

ASSUNTO(S)

campo magnetico interplanetario interacoes sol-terra tempestades magneticas geofisica espacial nuvens magneticas meio interplanetario

ACESSO AO ARTIGO

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