November 2020
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34 Reads
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November 2020
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34 Reads
January 2020
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30 Reads
December 2007
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122 Reads
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41 Citations
Journal of Geophysical Research Atmospheres
1] Precipitation of relativistic electrons into the atmosphere has been suggested as the primary loss mechanism for radiation belt electrons during large geomagnetic storms. Here we investigate the geographical spread of precipitation as a result of the arrival of a coronal mass ejection (CME) on 21 January 2005. In contrast to previous statistical studies we provide one of the first attempts to describe the geographic and temporal variability of energetic particle precipitation on a global scale using an array of instruments. We combine data from subionospheric VLF radio wave receivers, the high-altitude Miniature Spectrometer (MINIS) balloons, riometers, and pulsation magnetometers during the first hour of the event. There were three distinct types of energetic electron precipitation observed, one globally, one on the dayside, and one on the nightside. The most extensively observed form of precipitation was a large burst starting when the CME arrived at the Earth, where electrons from the outer radiation belt were lost to the atmosphere over a large region of the Earth. On the dayside of the Earth (10–15 MLT) the CME produced a further series of precipitation bursts, while on the nightside dusk sector (50 min was observed at 2.5 < L < 3.7 along with Pc 1–2 pulsations observed with a ground-based magnetometer. These observations suggest that the generation of energetic electron precipitation at the inner edge of the outer radiation belt from electromagnetic ion cyclotron (EMIC) wave scattering into the loss cone is the most direct evidence to date connecting EMIC activity and energetic precipitation. (2007), Energetic particle precipitation into the middle atmosphere triggered by a coronal mass ejection,
March 2007
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98 Reads
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19 Citations
Eos Transactions American Geophysical Union
During the night of 22-23 February 2006, more than 400 middle-atmospheric optical discharges were observed above one large thunderstorm system over northeastern Argentina. These transient luminous events (TLEs) were imaged during the Southern Brazil Sprite Campaign, the first campaign to focus on TLEs over southern Brazil, northeastern Argentina, and Uruguay. All of the TLEs were imaged from the Brazilian Southern Space Observatory (SSO) near Santa Maria, which is nearly in the center of the southernmost Brazilian state of Rio Grande do Sul. Although the fields of view of the imaging cameras were too narrow to view the entire storm, the more than 400 confirmed TLEs imaged indicate that this storm ranks as the third most active TLE producer ever reported. Hence, storms in this region of South America might be some of the leading TLE generators on Earth.
December 2006
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8 Reads
The MINIS campaign provided the first opportunities for multi-point measurements of electron precipitation up to MeV energies, including simultaneous measurements at different longitudes and at near-conjugate locations. Two balloons, each carrying an X-ray spectrometer for measuring the bremsstrahlung produced as electrons precipitate into the atmosphere, were launched from Churchill, Manitoba at 0850 UT on 21 January 2005 and 0140 UT on 25 January 2005. Four balloons, each carrying an X-ray spectrometer, a Z-axis search coil magnetometer, and a 3-axis electric field instrument providing DC electric field and VLF measurements in 3 frequency bands, were launched from the South African Antarctic Station (SANAE IV). The Southern launches took place at 1400 UT on 17 January, 1309 UT on 19 January, 2115 UT on 20 January, and 0950 UT on 24 January 2005. On 20 January, there was an X 7.1 class solar flare at 0650 UT. This flare produced a halo coronal mass ejection (CME) that impacted the Earth 36 hours later. At the Earth, there were two shocks with a staircase structure in density observed by the ACE spacecraft. The delayed to Earth arrival times of these shocks were 1713 and 1844 UT. The Cluster spacecraft in the solar wind also observed the shock waves closer to the Earth. Refined arrival time estimates will be discussed. During the geomagnetic storm that this CME impact produced there were 3 MINIS balloons aloft, one in the N Hemisphere and two in the South. In the balloon data, the first shock impact appeared to produce two electric field impulses of ~30 minute duration and up to 60 mV/m amplitude corresponding to flow toward the dayside cusp. These events were accompanied or followed by bursts of MeV electron precipitation, the first of which was observed in both hemispheres. The relationship between these impulses and the variations in IMF Bz will be explored. Additionally, the resulting phase shift (~ 20 min) between peak convection times in the N Hemisphere and S Hemisphere, as measured by the SuperDARN radar and MINIS, are presented and discussed. The electric field variations detected from separated balloon platforms can provide insight into the fields that convect energetic particles to form new radiation belts.
December 2005
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39 Reads
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20 Citations
Advances in Space Research
Vertical electric current density was obtained from direct electric field and conductivity measurements on two stratospheric balloon payloads during the 2nd polar patrol balloon (PPB) campaign from Syowa Station in Antarctica during January 2003. Payloads of these two flights were identical and were launched 8-h apart resulting in separation distances of a few hundred km during the time of overlapping data. The float altitude of each was a little over 30 km. The global circuit return current derived from these measurements is compared to the global lightning activity determined by the world wide lightning location (WWLLN) network. The total number of lightning events detected anywhere in the world are simply summed to form an hourly lightning flash rate for the time of the PPB data. The WWLLN and return current density data are shown to have a strong correlation, often with a strong universal time daily variation, similar to that expected for the global circuit.
December 2005
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71 Reads
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11 Citations
Advances in Space Research
The first campaign of the Polar Patrol Balloon (PPB) experiment (1st-PPB) was carried out at Syowa Station in Antarctica during 1990–1991 and 1992–1993. Based on the results of the 1st-PPB experiment, the next campaign (2nd-PPB) was carried out in the austral summer of 2002–2003. This paper will present stratospheric conductivity results from the 2nd-PPB experiment. In that experiment, three balloons were launched for the purpose of upper atmosphere physics observation (three balloons). Payloads of these three flights were identical with each other, and were launched as close together in time as allowed by weather conditions to constitute a cluster of balloons during their flights. Such a “Balloon Cluster” is suitable to observe temporal evolution and spatial distribution of phenomena in the ionospheric regions and boundaries that the balloons traversed during their circumpolar trajectory. More than 20 days of simultaneous fair weather 3-axis electric field and stratospheric conductivity data were obtained at geomagnetic latitudes ranging from sub-auroral to the polar cap. Balloon separation varied from ∼60 to >1000 km. This paper will present stratospheric conductivity observations with emphasis on the temporal and spatial variations that were observed.
... La densité électronique et le champ électrique ayant une grande variabilité spatiale dans les têtes de streamers, le champ électrique maximal devrait être corrigé d'un facteur > 1.4 pour les streamers positifs, et > 1.5 pour les streamers négatifs. Gerken et al. 2000 ;Lyons 1994 ;. D'autres ont été menées au Brésil (Thomas et al. 2007), en Hongrie (Bór 2013), en Afrique du Sud (Nnadih et al. 2016), en Espagne (Passas et al. 2016), et depuis l'Observatoire du Pic du Midi (Soula et al. 2014). ...
March 2007
Eos Transactions American Geophysical Union
... High fluxes of relativistic electrons existed at least a week after a major geomagnetic storm, even while Dst was -30 to -20 nT, and they concluded that ion pair production below 60 km can easily be an order of magnitude more than during quiet geomagnetic conditions. Clilverd et al. (2007) were further able to demonstrate dayside relativistic electron precipitation (REP) from EMIC waves, originating in the 4 ≤ L ≤ 5 outer radiation belt that were associated with a CMEmagnetosphere coupled event. Xu et al. (2018) studied monoenergetic beams of 0.1-10 MeV precipitating electrons into the atmosphere to understand the process of bremsstrahlung radiation and its resultant ionization production and atmospheric effects, including pitch angle dependence in the ionization rate profile. ...
December 2007
Journal of Geophysical Research Atmospheres
... Byrne et al. (1988) observed stratospheric conductivity and its change at three latitudes (10-30 km) by using nine high-altitude balloons, and they discussed the effects of aerosols and latitudinal temperature variations. In addition, Hu and Holzworth (1996), Bering et al. (2005) and John et al. (2009) have completed measurements of stratospheric conductivity. They used the relaxation probe method, which saves space and electricity and is also applicable to space missions (Berthelier et al. 2000). ...
December 2005
Advances in Space Research
... This is a real-time global flash detection network with worldwide coverage. WWLLN has more than 70 sensors around the world today [59][60][61]. Each station in the network consists of a 1.5 m antenna, a GPS (global positioning system) receiver, a receiver for very low frequency electromagnetic radiation (VLF) called lightning sferics and a computer with internet connection. ...
December 2005
Advances in Space Research