Alfven: magnetosphere-ionosphere connection explorers

The aurorae are dynamic, luminous displays that grace the night skies of Earth’s high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the ionospheric environment at the top of Earth’s atmosphere play a central role. In this Auroral Acceleration Region (AAR) persistent electric fields directed along the magnetic field accelerate magnetospheric electrons to the high energies needed to excite luminosity when they hit the atmosphere. The “ideal magnetohydrodynamics” description of space plasmas which is useful in much of the magnetosphere cannot be used to understand the AAR. The AAR has been studied by a small number of single spacecraft missions which revealed an environment rich in wave-particle interactions, plasma turbulence, and nonlinear acceleration processes, acting on a variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster magnetospheric research mission is now fortuitously visiting the AAR, but its particle instruments are too slow to allow resolve many of the key plasma physics phenomena. The Alfvén concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planet

TARANIS - impact of recent observations on the scientific payload

International audienceTARANIS (Tool for the Analysis of Radiations from lightNings and Sprites) is a CNES satellite project dedicated to the study of impulsive transfers of energy between the Earth atmosphere and the space environment, and more precisely to the physics of the Transient Luminous Events (TLEs) and of the Terrestrial Gamma ray Flashes (TGFs). Recent observations have leaded the TARANIS scientific team to reinforce several scientific objectives, to redesign the gamma ray instrument, and to check the adequacy of the other instruments. As a result it is shown that: (i) satellite optical observations at the nadir may have, as a supplementary advantage, to spatially resolve close TLE structures observed at ground, (ii) with its new design, the gamma ray instrument reaches the sensitivity to detect almost every TGFs, with their temporal evolutions, and provides more accurate information on the spatial localization (not only altitude, but also azimuth and elevation) of the production sources, (iii) the electron spectrometers allows to characterize the energy distribution of runaway electrons and the angular distribution of lightning induced electron precipitations, (iv) radio observations are well suited to a full characterization of 0+ whistlers below 1 MHz and to an investigation of the nature of lightning-related pulses in the HF band. Finally, the present status of the mission is presented

TARANIS - impact of recent observations on the scientific payload

International audienceTARANIS (Tool for the Analysis of Radiations from lightNings and Sprites) is a CNES satellite project dedicated to the study of impulsive transfers of energy between the Earth atmosphere and the space environment, and more precisely to the physics of the Transient Luminous Events (TLEs) and of the Terrestrial Gamma ray Flashes (TGFs). Recent observations have leaded the TARANIS scientific team to reinforce several scientific objectives, to redesign the gamma ray instrument, and to check the adequacy of the other instruments. As a result it is shown that: (i) satellite optical observations at the nadir may have, as a supplementary advantage, to spatially resolve close TLE structures observed at ground, (ii) with its new design, the gamma ray instrument reaches the sensitivity to detect almost every TGFs, with their temporal evolutions, and provides more accurate information on the spatial localization (not only altitude, but also azimuth and elevation) of the production sources, (iii) the electron spectrometers allows to characterize the energy distribution of runaway electrons and the angular distribution of lightning induced electron precipitations, (iv) radio observations are well suited to a full characterization of 0+ whistlers below 1 MHz and to an investigation of the nature of lightning-related pulses in the HF band. Finally, the present status of the mission is presented

TARANIS - impact of recent observations on the scientific payload

International audienceTARANIS (Tool for the Analysis of Radiations from lightNings and Sprites) is a CNES satellite project dedicated to the study of impulsive transfers of energy between the Earth atmosphere and the space environment, and more precisely to the physics of the Transient Luminous Events (TLEs) and of the Terrestrial Gamma ray Flashes (TGFs). Recent observations have leaded the TARANIS scientific team to reinforce several scientific objectives, to redesign the gamma ray instrument, and to check the adequacy of the other instruments. As a result it is shown that: (i) satellite optical observations at the nadir may have, as a supplementary advantage, to spatially resolve close TLE structures observed at ground, (ii) with its new design, the gamma ray instrument reaches the sensitivity to detect almost every TGFs, with their temporal evolutions, and provides more accurate information on the spatial localization (not only altitude, but also azimuth and elevation) of the production sources, (iii) the electron spectrometers allows to characterize the energy distribution of runaway electrons and the angular distribution of lightning induced electron precipitations, (iv) radio observations are well suited to a full characterization of 0+ whistlers below 1 MHz and to an investigation of the nature of lightning-related pulses in the HF band. Finally, the present status of the mission is presented

The Magnetosheath

International audienc

Immune response to Bordetella pertussis is associated with season and undernutrition in Senegalese children

Background: While vaccines elicit a protective response in most recipients, studies suggest that environmental and nutritional factors can influence the strength of the individual response to immunization and to subsequent natural infectious challenges. Methods: We conducted a longitudinal survey in Senegal to assess the individual response to B. pertussis, a respiratory disease against which Senegalese children are vaccinated before the age of one (Clinicaltrials.gov ID: NCT01545115). A cohort of 203 children aged 1-9 from four villages of the Senegal River Valley was followed-up for 14 months (October 2008-January 2010). During that period, four visits have been made to the villages to assess the immunological and nutritional status of these children and to determine risk factors involved in the modulation of their humoral immune response to B. pertussis toxin. Results: A multivariate model has demonstrated that birth season and nutritional status appeared to modulate humoral response to pertussis toxin. Moreover, response to B. pertussis was dependent on age, village and time of visit. Conclusions: These results are consistent with the hypothesis that environmental and nutritional factors modulate children's response to pertussis following natural infection or vaccination

Effects of malnutrition on children's immunity to bacterial antigens in Northern Senegal

To evaluate immunity to vaccine-preventable diseases according to nutritional status, a longitudinal study was conducted in Senegalese children ages 1-9 years old. A linear regression analysis predicted that weight for age was positively associated with immunoglobulin G (IgG) response to tetanus toxoid in children born during the rainy season or at the beginning of the dry season. A relationship between village, time of visits, and levels of antibodies to tetanus showed that environmental factors played a role in modulating humoral immunity to tetanus vaccine over time. Moreover, a whole-blood stimulation assay highlighted that the production of interferon-gamma (IFN-gamma) in response to tetanus toxoid was compromised in stunted children. However, the absence of cytokine modulation in response to Mycobacterium tuberculosis-purified protein derivatives and phytohemagglutinin suggests that the overall ability to produce IFN-gamma was preserved in stunted children. Therefore, these results show that nutritional status can specifically alter the efficacy of long-lasting immunity to tetanus