The effects of particle precipitation on the ionosphere in the South Atlantic Anomaly Region
- Authors: Haggard, Raymond
- Date: 1994
- Subjects: Precipitation (Chemistry) Ionosphere Ionospheric electron density
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5463 , http://hdl.handle.net/10962/d1005248
- Description: The first ground based observations of aeronomic phenomena in the South Atlantic Anomaly Region are presented. These data show that enhancements in foF2 and foE can be directly attributed to precipitated electron energy fluxes in the Anomaly Region. The regular occurrence of particle induced sporadic-E ionization is also presented together with the first measurable 391.4 nm airglow radiation of about 16 R. The first comprehensive survey of energy fluxes carried by energetic particles using satellites is also presented for both daytime and nighttime as well as the seasonal fluctuations. We found that the nocturnally precipitated electron energy fluxes varied between 1 x 10⁻⁴ and 38 x 10⁻⁴ erg cm²s⁻¹, depending upon magnetic activity and season, whereas the daytime precipitated electron energy fluxes tended to vary between 1 x 10⁻³ and 8 x 10⁻³ erg cm⁻²s⁻¹, with a tendency to decrease during magnetically active periods. Electron density and temperature contours as well as NO⁺ and 0⁺ ions contours for nighttime are also presented. The main conclusion of the study is that precipitating electrons provide a significant and sometimes dominant source of ionization in the ionosphere over the South Atlantic Anomaly Region.
- Full Text:
- Date Issued: 1994
- Authors: Haggard, Raymond
- Date: 1994
- Subjects: Precipitation (Chemistry) Ionosphere Ionospheric electron density
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5463 , http://hdl.handle.net/10962/d1005248
- Description: The first ground based observations of aeronomic phenomena in the South Atlantic Anomaly Region are presented. These data show that enhancements in foF2 and foE can be directly attributed to precipitated electron energy fluxes in the Anomaly Region. The regular occurrence of particle induced sporadic-E ionization is also presented together with the first measurable 391.4 nm airglow radiation of about 16 R. The first comprehensive survey of energy fluxes carried by energetic particles using satellites is also presented for both daytime and nighttime as well as the seasonal fluctuations. We found that the nocturnally precipitated electron energy fluxes varied between 1 x 10⁻⁴ and 38 x 10⁻⁴ erg cm²s⁻¹, depending upon magnetic activity and season, whereas the daytime precipitated electron energy fluxes tended to vary between 1 x 10⁻³ and 8 x 10⁻³ erg cm⁻²s⁻¹, with a tendency to decrease during magnetically active periods. Electron density and temperature contours as well as NO⁺ and 0⁺ ions contours for nighttime are also presented. The main conclusion of the study is that precipitating electrons provide a significant and sometimes dominant source of ionization in the ionosphere over the South Atlantic Anomaly Region.
- Full Text:
- Date Issued: 1994
The establishment of a Lidar facility at Rhodes University
- Grant, Richard Peter James Seton
- Authors: Grant, Richard Peter James Seton
- Date: 1988
- Subjects: Optical radar , LIDAR , Receiver , Transmitter , Photon counting electronics , Aerosol scattering , Temperature profiles , Stratosphere
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5445 , http://hdl.handle.net/10962/d1001998
- Description: LIDAR is the optical equivalent of RADAR. A LIDAR facility has been established at Rhodes University using a flashlamp-pumped dye laser as the transmitter and a photomultiplier tube at the focus of a searchlight mirror as the receiver. The setting up of the receiver and transmitter as well as the design and construction of the photon counting electronics is described. The LIDAR has been used to measure aerosol scattering ratios and temperature profiles in the stratosphere and these results are presented with the algorithms and software used to reduce the data. Finally some recommendations are made for future work
- Full Text:
- Date Issued: 1988
- Authors: Grant, Richard Peter James Seton
- Date: 1988
- Subjects: Optical radar , LIDAR , Receiver , Transmitter , Photon counting electronics , Aerosol scattering , Temperature profiles , Stratosphere
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5445 , http://hdl.handle.net/10962/d1001998
- Description: LIDAR is the optical equivalent of RADAR. A LIDAR facility has been established at Rhodes University using a flashlamp-pumped dye laser as the transmitter and a photomultiplier tube at the focus of a searchlight mirror as the receiver. The setting up of the receiver and transmitter as well as the design and construction of the photon counting electronics is described. The LIDAR has been used to measure aerosol scattering ratios and temperature profiles in the stratosphere and these results are presented with the algorithms and software used to reduce the data. Finally some recommendations are made for future work
- Full Text:
- Date Issued: 1988
Atmospheric ionization by precipitated electrons
- Authors: Wulff, Annemarie
- Date: 1973 , 2013-10-31
- Subjects: Ionization , Electrons
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5503 , http://hdl.handle.net/10962/d1007229 , Ionization , Electrons
- Description: From Introduction: Precipitation of energetic particl es into the upper atmosphere is known to cause aurora at high latitudes. Sanae is situated in the vicinity of the South Atlantic Geomagnetic Anomaly (Gledhill and Van Rooyen (1963)) where the magnetic field intensity is very low and it is felt that this phenomenon may enhance the loss of particles from the trapping zone into the upper atmosphere. Previous work at Rhodes has shown that it is extremely likely that particle precipitation could be the cause of some ionospheric effects at Sanae. Gledhill and Torr (1966) found that a "disturbed" ionosphere at Sanae was linked with "high" fluxes of precipitated electrons in the area conjugate to Sanae. Later papers by Gledhill, Torr and Torr (1967), and Torr and Torr (1967a, 1968a) established that electrons are precipitated over a large part of the earth's surface and this phenomenon is probably responsible for an average of about 30% of F-layer disturbances. The frequency of precipitation and corresponding disturbances is most pronounced in the South Atlantic Geomagnetic Anomaly . , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1973
- Authors: Wulff, Annemarie
- Date: 1973 , 2013-10-31
- Subjects: Ionization , Electrons
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5503 , http://hdl.handle.net/10962/d1007229 , Ionization , Electrons
- Description: From Introduction: Precipitation of energetic particl es into the upper atmosphere is known to cause aurora at high latitudes. Sanae is situated in the vicinity of the South Atlantic Geomagnetic Anomaly (Gledhill and Van Rooyen (1963)) where the magnetic field intensity is very low and it is felt that this phenomenon may enhance the loss of particles from the trapping zone into the upper atmosphere. Previous work at Rhodes has shown that it is extremely likely that particle precipitation could be the cause of some ionospheric effects at Sanae. Gledhill and Torr (1966) found that a "disturbed" ionosphere at Sanae was linked with "high" fluxes of precipitated electrons in the area conjugate to Sanae. Later papers by Gledhill, Torr and Torr (1967), and Torr and Torr (1967a, 1968a) established that electrons are precipitated over a large part of the earth's surface and this phenomenon is probably responsible for an average of about 30% of F-layer disturbances. The frequency of precipitation and corresponding disturbances is most pronounced in the South Atlantic Geomagnetic Anomaly . , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1973
Electron precipitation and ionospheric disturbance
- Authors: Torr, Marsha R
- Date: 1966
- Subjects: Electrons , Electron precipitation , Ionosphere , Ionospheric electron density
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5509 , http://hdl.handle.net/10962/d1007691
- Description: From Introduction: The minimum in the scalar magnitude of the geographic total field, which lies off the coast of Brazil, allows the mirror points of trapped particles to dip low into the atmosphere over the South Atlantic Ocean, resulting in two regions of maximum intensity of preciptated particles in that region, one from the inner belt and one from the outer. High charged particle fluxes have been observed at low altitudes over these regions by satellites Sputnik 5 and 6 (Ginsburg et al, 1961) and Discoverer 31 (Seward and Kornblum, 1963) amongst others. The more southerly of these two regions acts as a sink for electrons from the outer radiation belt and will be referred to in what follows as the Southern Radiation Anomaly. Gladhill and van Rooyen (1963) predicted that the energy deposited in the upper atmosphere by these charged particles would be sufficient to give rise to enhanced geophysical effects such as auroral emission, X-rays and ionization and heating of the upper atmosphere in this region. Although some of these effects have been correlated with precipitated electrons, no definite relation had until now been established between ionospheric effects and precipitated particles. The aim of this thesis was to investigate such a relationship and the results were extremely successful. It will be shown conclusively in what follows, that the precipitation of electrons can account for the ionospheric disturbances defined by a disturbance criterion at all stations around L=4. Part I describes the exploration of the radiation belts and the magnetosphere with rockets and satellites. The resulting theoretical models based on the observations are discussed. A brief review is given of the work that has been done to date to derive equations for the loss and replenishment of particles in the belts. Because of the complexity of these and the number of doubtful factors involved, a simple model of injection of electrons into the outer belt is devised, giving average values of trapped and precipitated electron fluxes at any point around L=4. In Part II, this model is employed together with the disturbance criterion of Gledhill and Torr (1965) to examine the relationship between ionospheric disturbances and electron fluxes. Also the energy range of the precipitated particles is examined.
- Full Text:
- Date Issued: 1966
- Authors: Torr, Marsha R
- Date: 1966
- Subjects: Electrons , Electron precipitation , Ionosphere , Ionospheric electron density
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5509 , http://hdl.handle.net/10962/d1007691
- Description: From Introduction: The minimum in the scalar magnitude of the geographic total field, which lies off the coast of Brazil, allows the mirror points of trapped particles to dip low into the atmosphere over the South Atlantic Ocean, resulting in two regions of maximum intensity of preciptated particles in that region, one from the inner belt and one from the outer. High charged particle fluxes have been observed at low altitudes over these regions by satellites Sputnik 5 and 6 (Ginsburg et al, 1961) and Discoverer 31 (Seward and Kornblum, 1963) amongst others. The more southerly of these two regions acts as a sink for electrons from the outer radiation belt and will be referred to in what follows as the Southern Radiation Anomaly. Gladhill and van Rooyen (1963) predicted that the energy deposited in the upper atmosphere by these charged particles would be sufficient to give rise to enhanced geophysical effects such as auroral emission, X-rays and ionization and heating of the upper atmosphere in this region. Although some of these effects have been correlated with precipitated electrons, no definite relation had until now been established between ionospheric effects and precipitated particles. The aim of this thesis was to investigate such a relationship and the results were extremely successful. It will be shown conclusively in what follows, that the precipitation of electrons can account for the ionospheric disturbances defined by a disturbance criterion at all stations around L=4. Part I describes the exploration of the radiation belts and the magnetosphere with rockets and satellites. The resulting theoretical models based on the observations are discussed. A brief review is given of the work that has been done to date to derive equations for the loss and replenishment of particles in the belts. Because of the complexity of these and the number of doubtful factors involved, a simple model of injection of electrons into the outer belt is devised, giving average values of trapped and precipitated electron fluxes at any point around L=4. In Part II, this model is employed together with the disturbance criterion of Gledhill and Torr (1965) to examine the relationship between ionospheric disturbances and electron fluxes. Also the energy range of the precipitated particles is examined.
- Full Text:
- Date Issued: 1966
Ionospheric effects in the Southern radiation anomaly
- Authors: Torr, Douglas G
- Date: 1966
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5540 , http://hdl.handle.net/10962/d1013305
- Description: From introduction: As ionosphericist on the 4th South African National Antarctic Expedition, I spent twelve months at Sanae (70°18'S, 2°2l'W, L= 4) in 1963. In the course of routine vertical incidence soundings, it was noticed with some surprise that the frequency of occurrence of ionospheric blackouts was unexpectedly high. Initially this aroused considerable concern about the reliability of the equipment. In fact it has been · observed that some stations lying in and near the Southern Radiation Anomaly report such occasions as records lost due to non-ionospheric reasons. Coincidently, however, Gledhill and van Rooyen (1963), also of Rhodes University, predicted ionospheric irregularities and other geophysical phenomena in a region around Sanae where Ginsburg et al. (1962) observed high intensities of charged particles with Sputniks 5 and 6.
- Full Text:
- Date Issued: 1966
- Authors: Torr, Douglas G
- Date: 1966
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5540 , http://hdl.handle.net/10962/d1013305
- Description: From introduction: As ionosphericist on the 4th South African National Antarctic Expedition, I spent twelve months at Sanae (70°18'S, 2°2l'W, L= 4) in 1963. In the course of routine vertical incidence soundings, it was noticed with some surprise that the frequency of occurrence of ionospheric blackouts was unexpectedly high. Initially this aroused considerable concern about the reliability of the equipment. In fact it has been · observed that some stations lying in and near the Southern Radiation Anomaly report such occasions as records lost due to non-ionospheric reasons. Coincidently, however, Gledhill and van Rooyen (1963), also of Rhodes University, predicted ionospheric irregularities and other geophysical phenomena in a region around Sanae where Ginsburg et al. (1962) observed high intensities of charged particles with Sputniks 5 and 6.
- Full Text:
- Date Issued: 1966
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