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Energetic particle measurements from the Ulysses/COSPIN/LET instrument obtained during the August/September 2005 events
O. E. Malandraki, R. G. Marsden, C. Tranquille, R. J. Forsyth, H. A. Elliott,A. Geranios
Annales Geophysicae (ANGEO) , 2008,
Abstract: We report recent observations of energetic particles at energies 1–40 MeV/n made by the COSPIN/LET instrument onboard the Ulysses spacecraft during the period of intense solar activity in August/September 2005 during the declining phase of solar cycle 23. Ulysses, having started its climb to high southern latitudes for the third time, was located at ~5 AU, at a helio-latitude of ~30 degrees south. It detected the arrival of a solar wind compound stream resulting from the merging of a series of fast halo CMEs ejected from the Sun in late August and early September 2005 and their interaction with the pre-existing pattern of solar wind Stream Interaction Regions (SIRs) in the ambient medium through which they propagated. The heavy ion intensities are observed by COSPIN/LET to remain elevated for at least 20 days following the very intense X17.0/3B solar flare on 7 September and its associated very fast CME (plane of sky projected CME speed ~2400 km s 1). We carry out an analysis of the composition of the particle increases observed at the location of the spacecraft. Although the composition signatures were predominantly Solar Energetic Particle (SEP)-like, after the passage of the compound stream over Ulysses, in association with a characteristic forward and reverse shock pair, the observations showed evidence of an enhanced He content.
F-region ionospheric perturbations in the low-latitude ionosphere during the geomagnetic storm of 25-27 August 1987
A. V. Pavlov, S. Fukao,S. Kawamura
Annales Geophysicae (ANGEO) , 2004,
Abstract: We have presented a comparison between the modeled NmF2 and hmF2, and NmF2 and hmF2 which were observed at the equatorial anomaly crest and close to the geomagnetic equator simultaneously by the Akita, Kokubunji, Yamagawa, Okinawa, Manila, Vanimo, and Darwin ionospheric sounders and by the middle and upper atmosphere (MU) radar (34.85° N, 136.10° E) during the 25-27 August 1987 geomagnetically storm-time period at low solar activity near 201°, geomagnetic longitude. A comparison between the electron and ion temperatures measured by the MU radar and those produced by the model of the ionosphere and plasmasphere is presented. The corrections of the storm-time zonal electric field, EΛ, from 16:30 UT to 21:00 UT on 25 August bring the modeled and measured hmF2 into reasonable agreement. In both hemispheres, the meridional neutral wind, W, taken from the HWW90 wind model and the NRLMSISE-00 neutral temperature, Tn, and densities are corrected so that the model results agree with the ionospheric sounders and MU radar observations. The geomagnetic latitude variations in NmF2 on 26 August differ significantly from those on 25 and 27 August. The equatorial plasma fountain undergoes significant inhibition on 26 August. This suppression of the equatorial anomaly on 26 August is not due to a reduction in the meridional component of the plasma drift perpendicular to the geomagnetic field direction, but is due to the action of storm-time changes in neutral winds and densities on the plasma fountain process. The asymmetry in W determines most of the north-south asymmetry in hmF2 and NmF2 on 25 and 27 August between about 01:00-01:30 UT and about 14:00 UT when the equatorial anomaly exists in the ionosphere, while asymmetries in W, Tn, and neutral densities relative to the geomagnetic equator are responsible for the north-south asymmetry in NmF2 and hmF2 on 26 August. A theory of the primary mechanisms causing the morning and evening peaks in the electron temperature, Te, is developed. An appearance, magnitude variations, latitude variations, and a disappearance of the morning Te peaks during 25-27 August are caused by variations in EΛ, thermospheric composition, Tn, and W. The magnitude of the evening Te peak and its time location are decreased with the lowering of the geomagnetic latitude due to the weakening of the effect of the plasma drift caused by W on the electron density. The difference between 25 August and 26-27 August in an appearance, magnitude and latitude variations, and a disappearance of the evening Te peak is caused by variations in W, the thermospheric composition, Tn, and EΛ.
TEC variations during low solar activity period (2005–2007) near the Equatorial Ionospheric Anomaly Crest region in India
Mala S. Bagiya, H. P. Joshi, K. N. Iyer, M. Aggarwal, S. Ravindran,B. M. Pathan
Annales Geophysicae (ANGEO) , 2009,
Abstract: The dual frequency signals from the GPS satellites recorded at Rajkot (22.29° N, 70.74° E, Geographic, 14.03° N Geomagnetic) near the Equatorial ionization anomaly crest in India have been analyzed to study the ionospheric variations in terms of Total Electron Content (TEC) for the low solar activity period from April 2005 to December 2007. In this study, we describe the diurnal and seasonal variations of TEC, solar activity dependence of TEC and effects of a space weather related event, a geomagnetic storm on TEC. The diurnal variation of TEC shows pre-dawn minimum for a short period of time, followed by a steep early morning increase and then reaches maximum value between 14:00 LT and 16:00 LT. The mean diurnal variations during different seasons are brought out. It is found that TEC at Rajkot is at its maximum during Equinoctial months (March, April, September, October), and minimum during the Winter months (November, December, January, February), with intermediate values during Summer months (May, June, July, August), showing a semi annual variation. TEC values have been decreasing since 2005, onwards showing positive correlation with solar activity. TEC variations during the geomagnetic storm commencing 24 August 2005 with Dst= 216 nT are analysed. TEC shows a positive ionospheric storm effect on the first day of the storm and negative ionospheric storm effect on the next day. The equatorial Electrojet control on the development of the equatorial anomaly is also demonstrated.
Microwave burst with fine spectral structures in a solar flare on 2011 August 9  [PDF]
Baolin Tan,Chengming Tan,Yuying Liu
Physics , 2012, DOI: 10.1051/eas/1255035
Abstract: On August 9, 2011, there was an X6.9 flare event occurred near the west limb of solar disk. From the observation obtained by the spectrometer of the Chinese Solar Broadband Radio Spectrometer in Huairou (SBRS/Huairou) around the flare, we find that this powerful flare has only a short-duration microwave burst of about only 5 minutes, and during the short-duration microwave burst, there are several kinds of fine structures on the spectrogram. These fine structures include very short-period pulsations, millisecond spike bursts, and type III bursts. The most interesting is that almost all of the pulses of very short-period pulsation (VSP) are structured by clusters of millisecond timescales of spike bursts or type III bursts. And there exists three different kinds of frequency drift rates in the VSP: the frequency drift rates with absolute value of about 55 - 130 MHz s^{-1} in the pulse groups, the frequency drift rates with absolute value of about 2.91 - 16.9 GHz s^{-1} on each individual pulse, and the frequency drift rates with absolute value of about 15 - 25 GHz s$^{-1}$) at each individual spike burst or type III burst.
Hemispheric Differences in the Response of the Upper Atmosphere to the August 2011 Geomagnetic Storm: A Simulation Study  [PDF]
Erdal Yi?it,Harald U. Frey,Mark B. Moldwin,Thomas J. Immel,Aaron J. Ridley
Physics , 2015,
Abstract: Using a three-dimensional nonhydrostatic general circulation model, we investigate the response of the thermosphere-ionosphere system to the 5-6 August 2011 major geomagnetic storm. The model is driven by measured storm-time input data of the Interplanetary Magnetic Field (IMF), solar activity, and auroral activity. Simulations for quiet steady conditions over the same period are performed as well in order to assess the response of the neutral and plasma parameters to the storm. During the storm, the high-latitude mean ion flows are enhanced by up to 150-180%. Largest ion flows are found in the main phase of the storm. Overall, the global mean neutral temperature increases by up to 15%, while the maximum thermal response is higher in the winter Southern Hemisphere at high-latitudes than the summer Northern Hemisphere: 40% vs. 20%increase in high-latitude mean temperature, respectively. The global mean Joule heating increases by more than a factor of three. There are distinct hemispheric differences in the magnitude and morphology of the horizontal ion flows and thermospheric flows during the different phases of the storm. The largest hemispheric difference in the thermospheric circulation is found during the main and recovery phases of the storm, demonstrating appreciable geographical variations. The advective forcing is found to contribute to the modeled hemispheric differences.
Study of the turbulence in the central plasma sheet during August 24-28 geomagnetic storm using the CLUSTER satellite data
Arancibia Riveros, K;Stepanova, M;Bosqued, J. M.;Antonova, E. E.;
Geofísica internacional , 2008,
Abstract: we used the local intermittency measure technique based on the wavelet transform to study plasma velocity fluctuations measured by cluster ii ion spectrometry experiment during august 24-28 geomagnetic storm. the results obtained showed a significant increase in the level of intermittent turbulence at the end of main phase. it can be related to a significant increase in the substorm activity, and stretching of the geomagnetic field lines observed during the main phase. this fact is important for understanding the nature of geomagnetic storms.
Study of the turbulence in the central plasma sheet during August 24-28 geomagnetic storm using the CLUSTER satellite data  [PDF]
K. Arancibia Riveros,M. Stepanova,J. M. Bosqued,E. E. Antonova
Geofísica internacional , 2008,
Abstract: We used the local Intermittency Measure Technique based on the wavelet transform to study plasma velocity fluctuations measured by CLUSTER II Ion Spectrometry experiment during August 24-28 geomagnetic storm. The results obtained showed a significant increase in the level of intermittent turbulence at the end of main phase. It can be related to a significant increase in the substorm activity, and stretching of the geomagnetic field lines observed during the main phase. This fact is important for understanding the nature of geomagnetic storms.
Comparative study on cigarette smoking control strategies used in Tanzania and the United Kingdom, August to September 2005
H Hassan
Dar Es Salaam Medical Students' Journal , 2006,
Abstract: Objective: To identify and compare different smoking control strategies used in the United Kingdom and United Republic of Tanzania Design: Descriptive cross-sectional study Methodology: Data was collected by an interview and observation at various institutions and clinics in Dar Es Salaam, Tanzania and London, UK and analysed using Epi-Info 2002. Results: It was found that both the two countries have very good strategies against cigarette smoking but UK has a better organized system which is more effective in lowering down smoking prevalence. Conclusion: More efforts is needed to put into action the Tanzanian tobacco products regulation act 2003 because this act has very concrete objectives that if achieved as soon as possible will reduce the impending tobacco burden that is posing a big threat to our country.
A study of the Forbush decrease event of September 11, 2005 with GRAND  [PDF]
J. Poirier,M. Herrera,P. Hemphill,C. D'Andrea
Physics , 2008,
Abstract: Project GRAND, a proportional wire chamber array, is used to examine the decreased counting rate of ground level muons during the Forbush decrease event of September 11, 2005. Data are presented and compared to that of other cosmic ray monitors. A directional study of the Forbush decrease was undertaken and precursor anisotropies to this geomagnetic storm were studied utilizing GRAND's angular resolution.
Ultra low frequency geomagnetic field measurements during earthquake activity in Italy (September-October 1997)
U. Villante,M. Vellante,A. Piancatelli
Annals of Geophysics , 2001, DOI: 10.4401/ag-3594
Abstract: Different methods with different results have been proposed in the scientific literature to identify the possible occurrence of weak seismo-magnetic ULF emissions. In September-October, 1997 Central Italy was struck by repeated seismic activity (M L < 5.8). A simple amplitude analysis of the geomagnetic field variations (horizontal components, in the frequency range 4-100 mHz) at a geomagnetic facility located 65-85 km from epicenters of major earthquakes does not reveal in this case any clear evidence for possible ULF emissions.
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