Mastergradsoppgaver i teknologi - romfysikk

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Mastergradsoppgaver i teknologi - romfysikk

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• Influence of Meteoric Aerosol particles on the Charge Balance in the Upper Mesosphere During ECOMA 2010

  Svendsen, Åse (Master thesis; Mastergradsoppgave, 15-Dec-2011)

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  Abstract:

  This work is focused on the three sounding rocket launches during the ECOMA Geminids campaign in December 2010: One before the Geminids meteor shower, one at its peak and one some days after the peak. In this work, the main emphasis is on analyzing the results from electron and ion probes on the rockets, obtaining electron and ion density profiles, and comparing them with the measurements of meteoric smoke particles. Aerosol particles originating from meteors may be the condensation nuclei for ice particles that form phenomena such as NLC ad PMSE. This work concludes that there are strong indications of the existence of negatively charged smoke particles in the height region between 80-95km. It describes how these parameters were measured, and how to get from raw data to the end results.

  URI:

  http://hdl.handle.net/10037/3996

  File(s) in this item: 1

  thesis.pdf   (5.068Mb)
• Air temperature at 90 km altitude in the Artic obtained using meteor radar : validation, characterization and climate change.

  Kluken, Lars Grytbakk (Master thesis; Mastergradsoppgave, 30-Sep-2011)

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  Abstract:

  Temperatures at 90 km altitude above Ramfjordmoen (69°N, 19°E) have been obtained with the Nippon/Norwegian Tromsø Meteor Radar. The temperatures have been derived from meteor radar decay rates using two techniques: the pressure based and the temperature gradient based methods. The results have been compared to the Microwave Limb Sounder (MLS) instrument on board the Aura spacecraft. It was found that the pressure method was simpler to implement than the temperature gradient method and gave better results in relation to the MLS temperatures. With the use of a technique for statistical comparison of geophysical data, the intrinsic uncertainty of the radar temperatures was estimated to be less than 4 K. Two attempts to combine the two techniques in order to measure both temperatures and pressure with the meteor radar have been carried out. One of the approaches proved to be feasible and gave promising results. This indicates that the meteor radar may have the potential of producing continuous temperature and pressure measurements virtually independent of external data. A new collocated sodium lidar is introduced and some initial comparisons are carried out between the two instruments. At times there were large discrepancies, but more data is necessary in order to obtain reliable results. Finally, some possible uses of the radar temperatures are proposed. A method for investigating long term trends is discussed in detail. The data available resulted in a trend of - 2.2 K per decade, but more data is required to establish a trend with higher confidence. It was estimated that approximately 13 years of data are needed to determine the trend with a probability of 90 %.

  URI:

  http://hdl.handle.net/10037/3712

  File(s) in this item: 1

  thesis.pdf   (3.063Mb)
• Na lidar measurements during the ECOMA/Geminids campaign with focus on Na peak density and temperature

  Østerpart, Jørgen Olai Kristensen (Master thesis; Mastergradsoppgave, Feb-2011)

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  Abstract:

  Using a resonance lidar, atomic Na (sodium) can be observed in the 80-110 km altitude range of the atmosphere. Na belongs to the alkali metal group and is highly reactive, so one could expect that it would quickly react with other particles and leave its atomic state. Its actual behaviour however includes the formation of relatively dense layers which, from the perspective of a stationary lidar, form suddenly and can last for several hours before quickly disappearing again. Several theories on the formation of these layers have been developed, including temperature dependent chemical processes, but none of them seem to explain all of the observed events. In 2008, two articles about these sudden sodium layers were published by scientists who have worked with the Weber Na lidar at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR), located at Andøya, Norway \((69^{\circ} 16' N, 16^{\circ} 00' E)\). Nesse et al. (2008) describe one particular Na layer observed 5 November 2005 and consider in turn how the most probable theories match the observed data during this event. Heinrich et al. (2008) identify all the sudden Na layers that have been observed on ALOMAR between August 2000 and June 2006 and investigate in particular how these coincide with sporadic E-layers (thin layers of several types of metallic ions). The fourth ECOMA (Existence and Charged State of Meteoric Smoke Particles in the Middle Atmosphere) rocket campaign took place at the Andøya Rocket Range during November and December 2010. The Na lidar was operated to the extent possible during this period, resulting in near real-time data for two of the three rocket launches and a total of 48 hours of measurements which are presented in this text. Using the two formerly mentioned articles as a starting point, I have studied available theory about sudden Na layers and the ALOMAR Na lidar in particular, and the upper atmosphere and resonance lidars in general. While we did not observe any sudden Na layers during the ECOMA measurements, I look into an older dataset as an example.

  URI:

  http://hdl.handle.net/10037/3363

  File(s) in this item: 1

  thesis.pdf   (1.327Mb)
• Review and test of funnel shape geometries in solar wind acceleration

  Trollebø, Robert (Master thesis; Mastergradsoppgave, 15-Dec-2009)

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  Abstract:

  The origin and heating of the solar wind is still a puzzle. We review in this study the idea that the solar wind originates in coronal funnels. We place emphasis on the fast solar wind. This study provides primarily a historic overview over the development of the idea of funnel expansion. We present examples of recent solar wind studies that investigate the funnel geometry. These studies include both static and time dependent reconnection geometries. The time dependent reconnection geometry that we present and evaluate in more detail is He et al. 2008. They present their model in order to explain why blue and red shift of the spectral lines Si II, C IV and Ne VIII can be seen in the same flow tubes on the sun. We have found some of the strengths and weaknesses with this model by comparing the models results to observations and to contemporary papers that treat the same ions. We have found that the model results fit relatively well to observed Doppler shifts (velocities), but that the model ignores the physical mechanism below 5*10^6 m that transports the heavy ions to that height, and it does not fully explain the choices of initial conditions, in particular why the mass input occurs exactly at 5*10^6 m. These challenges with this model may be important to take into account when developing future models of funnels.

  URI:

  http://hdl.handle.net/10037/2406

  File(s) in this item: 1

  thesis.pdf   (1.822Mb)
• Multifractals and their application to geospace data

  Østvand, Lene (Master thesis; Mastergradsoppgave, 02-Jun-2008)

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  Abstract:

  In this thesis I first introduce multifractal theory and mathematical concepts for multifractal analysis. Different methods for different uses are described, with focus on a differentiating between coarse and fine theory approaches. Methods for analysing time series are also described, more specificly a direct method based on the coarse theory analysis, the wavelet transform modulus maxima (WTMM) method and the multifractal detrended fluctuation analysis (MFDFA). The next part of this thesis contains a selection of examples of applications of multifractals in science. Multifractal analysis have become very useful to describe properties of many phenomena in a wide range of fields, for instance space physics, medicine and finance, in addition to geology where fractal theory was first introduced. Finally, I have analysed the three components of the interplanetary magnetic field strength at the Earth's bow shock nose, the AE index and the Dst index for solar cycle 23, lasting from 1996 to 2006 with a peak in 1999. Multifractality was found for the IMF data and the AE index, which may indicate that both the AE index and the interplanetary magnetic field have a intermittent and turbulent character. Multifractality for the D$_{st}$ index was not shown as clearly, which indicates that this index is only weakly intermittent or not intermittent at all.

  URI:

  http://hdl.handle.net/10037/1772

  File(s) in this item: 1

  thesis.pdf   (1.314Mb)

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