Sökning: "solar activity"

Visar resultat 1 - 5 av 114 avhandlingar innehållade orden solar activity.

1. 1. Geomagnetic activity : periodic variations and connection to solar and interplanetary magnetic fields

   Författare :Hans Hauska; Uppsala universitet; []
   Nyckelord :NATURAL SCIENCES; NATURVETENSKAP;

   Sammanfattning : .... LÄS MER

3. 2. Combining Models of Coronal Mass Ejections and Solar Dynamos

   Författare :Jörn Warnecke; Axel Brandenburg; Juri Toomre; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Magnetohydrodynamics; convection; turbulence; solar dynamo; solar rotation; solar activity; coronal mass ejections; Astronomy; astronomi;

   Sammanfattning : Observations show that Coronal Mass Ejections (CMEs) are associated with twisted magnetic flux configurations. Conventionally, CMEs are modeled by shearing and twisting the footpoints of a certain distribution of magnetic flux at the solar surface and letting it evolve at the surface. LÄS MER

4. 3. Solar Wind and Geomagnetic Activity - Predictions Using Neural Networks

   Författare :Hans Gleisner; Astronomi - Genomgår omorganisation; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Geophysics; kosmisk kemi; rymdvetenskap; magnetosphere; solar wind; space weather; geomagnetic activity; geomagnetism; ring current; auroral electrojet; neural networks; forecasting; Astronomy; space research; Astronomi; cosmic chemistry; physical oceanography; meteorology; Geofysik; fysisk oceanografi; meteorologi; Fysicumarkivet A:2000:Gleisner;

   Sammanfattning : This thesis shows how artificial neural networks (ANNs) can be applied to predict geomagnetic activity from solar-wind data. It introduces and summarizes five papers where development of ANN models are reported, and where predictions of geomagnetic activity are discussed. LÄS MER

5. 4. Space Weather Physics, Prediction and classification of solar wind structures and geomagnetic activity using artificial neural networks

   Författare :Peter Wintoft; Astronomi - Genomgår omorganisation; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomi; cosmic chemistry; space research; Astronomy; solar magnetic fields; space weather; solar wind; magnesphere; artificial neural networks; geomagnetic activity; rymdvetenskap; kosmisk kemi; Fysicumarkivet A:1997:Wintoft;

   Sammanfattning : This thesis concerns the application of artificial neural network techniques to space weather physics. The networks applied include multi-layer error-backpropagation, radial basis function, and self-organized maps. LÄS MER

7. 5. Origin of solar surface activity and sunspots

   Författare :SARAH JABBARI; AXEL BRANDENBURG; Vasilis Archontis; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Sun-Solar activity-Sunspots; teoretisk astrofysik; Theoretical Astrophysics;

   Sammanfattning : In the last few years, there has been significant progress in the development of a new model for explaining magnetic flux concentrations, by invoking the negative effective magnetic pressure instability (NEMPI) in a highly stratified turbulent plasma. According to this model, the suppression of the turbulent pressure by a large-scale magnetic field leads to a negative contribution of turbulence to the effective magnetic pressure (the sum of non-turbulent and turbulent contributions). LÄS MER