Diurnal Variations of Quasi-Periodic and Periodic VLF emissions in the Outer Magnetosphere

Details Diurnal Variations of Quasi-Periodic and Periodic VLF emissions in the Outer Magnetosphere Diurnal Variations of Quasi-Periodic and Periodic VLF emissions in the Outer Magnetosphere

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufmsm11c1189e&link_type=abstract

American Geophysical Union, Fall Meeting 2003, abstract #SM11C-1189

Other

2731 Magnetosphere: Outer, 2736 Magnetosphere/Ionosphere Interactions, 2752 Mhd Waves And Instabilities, 2772 Plasma Waves And Instabilities

Scientific paper

ELF-VLF receiver and search coil magnetometer data from four Antarctic stations during 1998 have been analyzed to study quasi-periodic emissions (QPs) and periodic emissions (PEs), which occur as ULF-range modulations of ELF-VLF signals between 0.5 kHz and ˜4 kHz. QPs are modulated at frequencies of 15-50 mHz, and PEs are modulated at frequencies of 100-500 mHz. The stations used covered a range of magnetic latitudes from -62° (Halley) to -74° (South Pole Station); two automated geophysical observatories (AGOs) were located at intermediate latitudes. Consistent with earlier studies, most QPs were observed with magnetic pulsations of identical period in the Pc 3-4 range (type I QPs). Of those QPs not observed with simultaneous magnetic pulsations (type II QPs), nearly all were accompanied by PEs. It is also notable that no PE events simultaneous with Pc 3-4 magnetic pulsations but without QPs were observed during the entire year at any station. Diurnal patterns of all categories of QP events show occurrence maxima in the noon or post-noon sectors. The total absence of type I QP occurrences without PEs on the nightside is consistent with the expected absence of Pc 3-4 pulsations there, because of their origin at the upstream bow shock. PEs, on the other hand, could be seen at all local times. Diurnal profiles showed no latitudinal or seasonal differences for most categories, except for a clear reversal of the profile of PE occurrence with latitude. In every multistation event studied, we have found QP and/or PE modulations to be simultaneous at all stations to within the 1-s sampling time of the data. This suggests that all such events originate a single, localized region, most probably near the plasmapause. In contrast, the magnetic pulsations showed little or no detailed correlation between stations. Both statistical and single event studies support the hypothesis that highly localized field-aligned currents stimulated by echoing whistlers (PEs) may be responsible for producing type II QPs on the same flux tubes, typically in the subauroral or auroral regions. In addition, we have noted that the small number of type II QP events we have observed without accompanying PEs is tightly clustered near local noon. The existence of a set of equatorially-localized, near-noon, compressional Pc 3-4 waves that evidently do not appear in ground records suggests that this category as well might be generated by ULF wave modulation of equatorial ELF/VLF wave growth.

Affiliated with

Also associated with

No associations

Rating

Diurnal Variations of Quasi-Periodic and Periodic VLF emissions in the Outer Magnetosphere 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 Diurnal Variations of Quasi-Periodic and Periodic VLF emissions in the Outer Magnetosphere, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diurnal Variations of Quasi-Periodic and Periodic VLF emissions in the Outer Magnetosphere will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1647924