Antarctic Space Science - Publications
2006
[back]Effects of the equatorward auroral boundary location and solar wind parameters on Pc5 activity at auroral zone stations: A multiple regression analysis
Authors: Simms, L. E.; Engebretson, M. J.; Posch, J. L.; Hughes, W. J.
Journal: Journal of Geophysical Research, Volume 111, Issue A10, CiteID A10217
Date: Oct 2006
Abstract: We have conducted a multiple regression analysis of the effect of auroral boundary movement on Pc5 power, the pulsation index, and the product of these two parameters at 17 auroral zone ground magnetometer stations in both hemispheres in March-April 2001, during which time several strong magnetic storms occurred. Solar wind parameters observed by the ACE satellite (velocity, ion density, and Bz) were included as additional independent variables in the regression models to control for their known effects. Auroral boundary data were determined from particle data collected by the DMSP satellites. The fraction of time a station was poleward of the equatorward auroral boundary increased Pc5 power, pulsation index, and the product of the two parameters independent of changes in the solar wind and interplanetary magnetic field. When data were analyzed by storm onset and storm recovery, this association was seen only during storm recovery periods. Individual station analyses showed a reduction in Pc5 power when stations were equatorward of the boundary, but there was no reduction in the Pc5 pulsation index. However, this association between Pc5 activity and auroral boundary movement was not seen in simple graphical presentations; this argues for the value of multifactor analyses in the determination of the drivers of Pc5 activity, rather than the individual study of single factors. A more northward Bz correlated with increased Pc5 power and pulsation index. Solar wind velocity and ion density were both associated with higher Pc5 activity during daylight hours.
Narrow-band extremely low frequency (ELF) wave phenomena observed at South Pole Station
Authors: Kim, Hyomin; Lessard, Marc R.; LaBelle, James; Johnson, Jay R.
Journal: Geophysical Research Letters, Volume 33, Issue 6, CiteID L06109
Date: Mar 2006
Abstract: Extremely low frequency (ELF) magnetic pulsations which show a whistler-like spectral structure have been measured at South Pole Station. An initial survey of the first 70 days of data revealed narrow-band ELF pulsations with slowly varying frequency over time. The narrow-band (a few Hz) signatures maintain their bandwidth as their frequencies decrease from 110 to 50 Hz (and their second harmonics) over the course of 40-90 s. Although the narrow-band ELF waves have a signature somewhat similar to very low frequency (VLF) whistlers, their duration and frequency range are much different from those of whistlers; they also show an unusual characteristic where their frequency often increases before it decreases. These events show a peak in their magnetic local time (MLT) occurrence distribution near the pre-midnight region, a result that contrasts sharply with the only three previously published studies of these waves. Two possibilities of generation mechanism are discussed.
Further study of flickering auroral roar emission: 1. South Pole observations
Authors: Ye, S.; LaBelle, J.; Weatherwax, A. T.
Journal: Journal of Geophysical Research, Volume 111, Issue A7, CiteID A07301
Date: Jul 2006
Abstract: Hughes and LaBelle (2001) reported a single example of a new geophysical phenomenon: ~10 Hz modulation of auroral radio emissions near twice the auroral ionospheric electron gyrofrequency. They called this phenomenon flickering auroral roar and suggested that it is related to flickering aurora, which results from ~10 Hz modulation of the precipitating auroral electrons. Observations at South Pole Station during 2003 using a new high-bandwidth receiving system have yielded 10 examples of flickering roar emissions. Although 10 examples is still a small number for statistics, these observations considerably extend previous knowledge of this phenomenon which was based on a single example. On the basis of the 2003 South Pole data set, flickering auroral roar accounts for only about 1-2% of auroral roar in number of seconds, but ~20% of auroral roar events have some flickering feature. The observed modulation frequencies range from ~3 to 30 Hz. The 10- to 20-Hz modulations, which correspond to about 65% of the time when flickering roar occurs, are much more common than the higher-frequency 20- to 30-Hz modulations, which correspond to about 20% of the time when flickering roar occurs. These frequencies compare favorably with optical observations of auroral emissions, rocket observations of electron flux modulations, and modeling results. If these frequencies correspond to the oxygen gyrofrequency where electrons and ion cyclotron waves interact, the 3- to 30-Hz frequency range would imply sources at altitudes of 1500-10,500 km. Six of the ten flickering roar examples occurred during substorm expansion phase as defined from local magnetometer data, in contrast to flickering aurora, which is usually observed after the onset of auroral breakup.
Precipitation and total power consumption in the ionosphere: Global MHD simulation results compared with Polar and SNOE observations
Authors: Palmroth, M.; Janhunen, P.; Germany, G.; Lummerzheim, D.; Liou, K.; Baker, D. N.; Barth, C.; Weatherwax, A. T.; Watermann, J.
Journal: Annales Geophysicae, Volume 24, Issue 3, 2006, pp.861-872
Date: May 2006
Abstract: We compare the ionospheric electron precipitation morphology and power from a global MHD simulation (GUMICS-4) with direct measurements of auroral energy flux during a pair of substorms on 28-29 March 1998. The electron precipitation power is computed directly from global images of auroral light observed by the Polar satellite ultraviolet imager (UVI). Independent of the Polar UVI measurements, the electron precipitation energy is determined from SNOE satellite observations on the thermospheric nitric oxide (NO) density. We find that the GUMICS-4 simulation reproduces the spatial variation of the global aurora rather reliably in the sense that the onset of the substorm is shown in GUMICS-4 simulation as enhanced precipitation in the right location at the right time. The total integrated precipitation power in the GUMICS-4 simulation is in quantitative agreement with the observations during quiet times, i.e., before the two substorm intensifications. We find that during active times the GUMICS-4 integrated precipitation is a factor of 5 lower than the observations indicate. However, we also find factor of 2-3 differences in the precipitation power among the three different UVI processing methods tested here. The findings of this paper are used to complete an earlier objective, in which the total ionospheric power deposition in the simulation is forecasted from a mathematical expression, which is a function of solar wind density, velocity and magnetic field. We find that during this event, the correlation coefficient between the outcome of the forecasting expression and the simulation results is 0.83. During the event, the simulation result on the total ionospheric power deposition agrees with observations (correlation coefficient 0.8) and the AE index (0.85).
Further study of flickering auroral roar emission: 2. Theory and numerical calculations
Authors: Weatherwax, A. T.; Yoon, P. H.; Hughes, J. M.; LaBelle, J.; Ziebell, L. F.
Journal: Journal of Geophysical Research, Volume 111, Issue A7, CiteID A07302
Date: Jul 2006
Abstract: Two recent papers report ground-based observations of ~3-30 Hz pulsations in the amplitude of 2fce auroral roar radio emissions. These pulsations occur in groups which last for ~1 s with adjacent pulsation groups spaced from one to several seconds. We put forth that these pulsations reflect periodic modulation of precipitating auroral electron fluxes, which could include periodic downward field-aligned bursts (FABs) and periodically modulated inverted-V electron precipitation, similar to those that could account for flickering aurora. We calculate time and frequency variations in the growth rate of Z-mode waves in the ionosphere for two different models of time-varying electron distribution functions, one corresponding to acceleration by electromagnetic ion cyclotron waves (EMIC) and the other corresponding to a simple time-varying accelerating potential (TVP). On the basis of these numerical calculations, the reported characteristics of ~10 Hz flickering roar appear consistent with modulations induced in the electron distribution function via interaction with EMIC waves, since the modulation associated with EMIC waves results in flickering of only the lower portion of the auroral roar frequency band, as in most of the observations. The few observed cases of higher-frequency flickering roar, at ~20-30 Hz, fall above the O+ cyclotron frequency for the altitude range on interest, and may represent a different source of electron flux modulation such as a varying electrostatic potential. The radio observations provide an additional means of probing flickering phenomenon and in particular may put constraints on the form of modulations of the electron distribution function at the auroral roar source height of a few hundred kilometers.
The outer radiation belt injection, transport, acceleration and loss satellite (ORBITALS): A canadian small satellite mission for ILWS
Authors: Mann, I. R.; Balmain, K. G.; Blake, J. B.; Boteler, D.; Bourdarie, S.; Clemmons, J. H.; Dent, Z. C.; Degeling, A. W.; Fedosejeves, R.; Fennell, J. F.; Fraser, B. J.; Green, J. C.; Jordanova, V. K.; Kale, A.; Kistler, L. M.; Knudsen, D. J.; Lessard, M. R.; Loto'Aniu, T. M.; Milling, D. K.; O'Brien, T. P.; Onsager, T. G.; Ozeke, L. G.; Rae, I. J.; Rankin, R.; Reeves, G. D.; Ridley, A. J.; Sofko, G. J.; Summers, D.; Thomson, I.; Thorne, R. M.; Tsui, Y. Y.; Unick, C.; Vassiliadis, D.; Wygant, J. R.; Yau, A. W.
Journal: Advances in Space Research, Volume 38, Issue 8, p. 1838-1860.
Date: n/a 2006
Abstract: The outer radiation belt injection, transport, acceleration and loss satellite (ORBITALS) is a small satellite mission proposed as a Canadian contribution to the satellite infrastructure for the International Living With a Star (ILWS) program. The ORBITALS will monitor the energetic electron and ion populations in the inner magnetosphere across a wide range of energies (keV to tens of MeV) as well as the dynamic electric and magnetic fields, waves and cold plasma environment which govern the injection, transport, acceleration and loss of these energetic and space weather critical particle populations. ORBITALS will be launched around 2010 2012 into a low-inclination GTO-like orbit which maximizes the long-lasting apogee-pass conjunctions with both the ground-based instruments of the Canadian Geospace Monitoring (CGSM) array as well as with the GOES East and West and geosynchronous communications satellites in the North American sector. Specifically, the ORBITALS will make the measurements necessary to gain fundamental new understanding of the relative importance of different physical acceleration and loss processes which are hypothesised to shape the energetic particle populations in the inner magnetosphere. The ORBITALS will also provide the raw radiation measurements at MEO altitudes necessary for the development of the next-generation of radiation belt specification models, and on-board experiments will also monitor the dose, single-event upset, and deep-dielectric charging responses of electronic components on-orbit. In this paper we outline the scientific objectives of the ORBITALS mission, discuss how the ORBITALS will lead to solutions to outstanding questions in inner magnetospheric science, and examine how the ORBITALS will complement other proposed inner magnetosphere missions in the ILWS era.
Global geomagnetic and auroral response to variations in the solar wind dynamic pressure on April 1, 1997
Authors: Solovyev, S. I.; Moiseev, A. V.; Barkova, E. S.; Yumoto, K.; Engebretson, M.
Journal: Geomagnetism and Aeronomy, vol. 46, issue 1, pp. 41-51
Date: Jan 2006
Abstract: Not Available
Nature of Pi1B pulsations as inferred from ground and satellite observations
Authors: Lessard, M. R.; Lund, E. J.; Jones, S. L.; Arnoldy, R. L.; Posch, J. L.; Engebretson, M. J.; Hayashi, K.
Journal: Geophysical Research Letters, Volume 33, Issue 14, CiteID L14108
Date: Jul 2006
Abstract: The occurrence of Pi1B pulsations is well-documented, including the fact that these pulsations can be observed both on the ground and at geosynchronous orbit at substorm onset, although information about their propagation characteristics has been lacking. In this paper, data are presented from FAST, GOES 9 and various ground stations that show the simultaneous observations of Pi1B pulsations in association with an onset. While the data at GOES 9 show that the pulsations are compressional in nature, data from FAST show the presence of shear mode waves, implying that Pi1B mode conversion of some type must take place in the region between geosynchronous orbit and FAST altitudes. An additional point is that Pi1B pulsations apparently propagate through auroral phenomena routinely, begging the question of what role they may play.
Statistical characteristics of the spatial distribution of Pc3-4 geomagnetic pulsations at high latitudes in the antarctic regions
Authors: Chugunova, O. M.; Pilipenko, V. F.; Engebretson, M.; Rodger, A. S.
Journal: Geomagnetism and Aeronomy, vol. 46, issue 1, pp. 64-73
Date: Jan 2006
Abstract: Not Available