Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsm33a1765s&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #SM33A-1765
Physics
2403 Active Experiments, 2481 Topside Ionosphere, 2487 Wave Propagation (0689, 3285, 4275, 4455, 6934), 2494 Instruments And Techniques, 2772 Plasma Waves And Instabilities (2471)
Scientific paper
This paper presents the physical principles of the whistler mode (WM) echo generation when WM waves are injected from a spacecraft at low altitudes (< 5000 km). A WM echo is generated when a wave injected from a source in the magnetosphere reflects and comes back to the source either by retracing its path or by forming a loop. There are two reflection mechanisms: 1) magnetospheric reflection (MR) that occurs at altitudes where the wave frequency (f) approximately equals the lower hybrid frequency (flh). WM waves that undergo magnetospheric reflection and come back to the satellite are called magnetospherically reflected whistler mode (MR-WM) echoes. The echo ray path in this case is a loop. 2) Specular reflection that occurs at the Earth-ionosphere boundary. There are two kinds of echoes that are generated via specular reflection: a) vertically (or normally) incident specularly reflected whistler mode (VI-SR-WM or NI-SR-WM) echo that retraces its path and returns back to the source. b) Obliquely incident specularly reflected whistler mode (OI-SR-WM) echo that forms a loop and returns back to the satellite. The changes in topology and size of the WM refractive index surface as a function of altitude along the geomagnetic field line and the Snell's law explain the generation of both retracing and looping types of echoes. The type of reflection that WM wave undergoes and the properties of WM echoes generated depend on the value of wave frequency relative to the plasma frequency (fpe), gyro frequency (fce), and lower hybrid frequency (flh) along the field line passing through the injection point (satellite). For example, waves injected from an altitude of a few thousand kilometers lead to the following echoes: (1) In the frequency regime flh,Sat, where flh,Sat is the lower hybrid frequency at the satellite, the rays injected from the spacecraft undergo both magnetospheric and specular reflection; magnetospherically reflected waves diverge away from the satellite, and only one echo - VI-SR-WM echo - is observed. (2) For flh,Satlh,max, where flh,max is the maximum lower hybrid frequency along the field line passing through the satellite, MR-WM and VI-SR-WM echoes are observed. (3) For flh,maxce/2 and assuming fce < fpe, OI- SR-WM and VI-SR-WM echoes are observed. (4) For fce/2 ce and assuming fce < fpe, VI-SR- WM and OI-SR-WM echoes are observed for frequencies close to fce/2, but as the wave frequency approaches fce only VI-SR-WM echo is observed. The generation mechanisms of various types of echoes are demonstrated with Poeverlein constructions and ray tracing simulations, and are illustrated with MR-WM and SR-WM echoes observed by Radio Plasma Imager (RPI) on IMAGE at < 5000 km.
class="ab'>
Carpenter Donald L.
Reddy Akula Aneesh
Reinisch Bodo. W.
Sonwalkar Vikas S.
No associations
LandOfFree
The Physical Principles of the Generation of Whistler Mode Echoes by a Radio Sounder (RPI) on a Spacecraft (IMAGE) 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 The Physical Principles of the Generation of Whistler Mode Echoes by a Radio Sounder (RPI) on a Spacecraft (IMAGE), we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Physical Principles of the Generation of Whistler Mode Echoes by a Radio Sounder (RPI) on a Spacecraft (IMAGE) will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1096813