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Structured Waves Near The Plasma Frequency Observed In Three Auroral Rocket Flights, M Samara, J Labelle
Structured Waves Near The Plasma Frequency Observed In Three Auroral Rocket Flights, M Samara, J Labelle
Dartmouth Scholarship
Abstract. We present observations of waves at and just above the plasma frequency (fpe) from three high frequency electric field experiments on three recent rockets launched to altitudes of 300–900 km in active aurora. The predominant observed HF waves just above fpe are narrowband, short- lived emissions with amplitudes ranging from <1mV/m to 20 mV/m, often associated with structured electron den- sity. The nature of these HF waves, as determined from frequency-time spectrograms, is highly variable: in some cases, the frequency decreases monotonically with time as in the “HF-chirps” previously reported (McAdams and La- Belle, 1999), but in other cases rising frequencies are ob- served, or features which alternately rise and fall in fre- quency. They exhibit two timescales of amplitude variation: a short timescale, typically 50–100 ms, associated with in- dividual discrete features, and a longer timescale associated with the general decrease in the amplitudes of the emissions as the rocket moves away from where the condition f ∼fpe holds. The latter timescale ranges from 0.6 to 6.0 s, corre- sponding to distances of 2–7 km, assuming the phenomenon to be stationary and using the rocket velocity to convert time to distance.
The Structure Of Flux Transfer Events Recovered From Cluster Data, H Hasegawa, B U. Ö Sonnerup, C J. Owen, B Klecker, G Paschmann, A Balogh, H Re`Me
The Structure Of Flux Transfer Events Recovered From Cluster Data, H Hasegawa, B U. Ö Sonnerup, C J. Owen, B Klecker, G Paschmann, A Balogh, H Re`Me
Dartmouth Scholarship
The structure and formation mechanism of a to- tal of five Flux Transfer Events (FTEs), encountered on the equatorward side of the northern cusp by the Cluster space- craft, with separation of ∼5000 km, are studied by apply- ing the Grad-Shafranov (GS) reconstruction technique to the events. The technique generates a magnetic field/plasma map of the FTE cross section, using combined magnetic field and plasma data from all four spacecraft, under the assump- tion that the structure is two-dimensional (2-D) and time- independent. The reconstructed FTEs consist of one or more magnetic flux ropes embedded in the magnetopause, suggest- ing …