Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsa14a..02b&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #SA14A-02
Physics
2415 Equatorial Ionosphere, 2437 Ionospheric Dynamics, 2439 Ionospheric Irregularities, 2471 Plasma Waves And Instabilities (2772), 2481 Topside Ionosphere
Scientific paper
DEMETER, the first micro-satellite of the CNES MYRIAD program, was launched from Baikonour on June 29, 2004 on a nearly circular, quasi helio-synchronous polar orbit at ~ 715 km altitude. The DEMETER mission focuses primarily on the search for a possible coupling between seismic activity and ionospheric disturbances as well as on the effects of natural phenomena such as tropospheric thunderstorms and man-made activities on the ionosphere. The scientific payload provides fairly complete measurements of the ionospheric plasma, energetic particles above ~ 70 keV, and plasma waves, up to 20 kHz for the magnetic and 3.3 MHz for the electric components. Several studies related to space weather and ionospheric physics have been conducted over the past years. Following a brief description of the payload and the satellite modes of operation, this presentation will focus on a set of results that provide a new insight into the physics of instabilities in the night-time equatorial ionosphere. The observations were performed during the major magnetic storm of November 2004. Deep plasma depletions were observed on several night-time passes at low latitudes characterized by the decrease of the plasma density by nearly 3 orders of magnitude relative to the undisturbed plasma, and a significant abundance of molecular ions. These features can be best interpreted as resulting from the rise of the F-layer above the satellite altitude over an extended region of the ionosphere. In one of the passes, DEMETER was operated in the Burst mode and the corresponding high resolution data allowed for the discovery of two unexpected phenomena. The first one is the existence of high intensity monochromatic wave packets at the LH frequency that develop during the decay phase of intense bursts of broadband LH turbulence. The broadband LH turbulence is triggered by whistlers emitted by lightning from atmospheric thunderstorms beneath the satellite. The second unexpected feature is the detection of a population of super-thermal ionospheric ions with a density of about 2-3% of the thermal ion population. The super- thermal ions appeared to be heated to temperatures of a few eV at times when LH turbulence and monochromatic wave packets are observed while the temperature of the core ion population is not affected. High time resolution plasma density measurements show the presence of strong small scale plasma irregularities in the depletions that scatter the high amplitude whistler waves and may lead to the development of strong LH turbulence and of monochromatic wave packets. The ensuing interaction between these waves and the ambient ions may lead to the formation of a super-thermal tail in the ion distribution function. Ion acceleration by LH turbulence and solitary waves is a commonly observed phenomenon along auroral magnetic field lines but, to our knowledge, this is the first time that a similar process has been observed in the equatorial ionosphere. These findings exemplify a novel coupling mechanism between the troposphere and the ionosphere: Under highly disturbed conditions at times of magnetic storms, part of the energy released by lightning and radiated as whistlers can dissipate in the equatorial ionosphere and produce super-thermal ion populations.
Berthelier Jean-Jacques
Jasperse J.
Malingre Michel
Parrot Michel
Pfaff Robert
No associations
LandOfFree
DEMETER Observations of Equatorial Plasma Depletions and Related Ionospheric Phenomena does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with DEMETER Observations of Equatorial Plasma Depletions and Related Ionospheric Phenomena, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and DEMETER Observations of Equatorial Plasma Depletions and Related Ionospheric Phenomena will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1243689