Global distribution of equatorial plasma bubbles in the premidnight sector during solar maximum as observed by KOMPSAT‐1 and Defense Meteorological Satellite Program F15

Abstract

We investigated the global distribution of equatorial plasma bubbles (EPBs) using in situ plasma density measurements from Korea Multipurpose Satellite‐1 (KOMPSAT‐1) and Defense Meteorological Satellite Program (DMSP) F15 during the solar maximum period from June 2000 to August 2001. The results were generally consistent with those of previous studies. EPBs were observed at all longitudes around the magnetic dip equator in the equinoctial seasons with the peak occurrence in the American‐Atlantic‐African regions. During the June solstice, EPBs occurred predominantly in the African sector, with enhancements in the magnetic north in the Indian and west Pacific regions, but were totally suppressed in the American‐Atlantic sector. During the December solstice, EPBs occurred frequently in the American‐Atlantic sector but were suppressed in the other longitude sectors, especially in the Pacific sector. The EPB occurrence probability was seen to be correlated with the observed topside plasma density and the model prereversal upward drift speed of ambient plasmas (Fejer et al., 1999), with their respective dominance dependent on the seasons. However, the peak EPB occurrence in the American‐Atlantic sector during the December solstice was displaced somewhat from the region of peak density and upward drift, probably due to a strong solar terminator influence on the flux tube–integrated E region Pedersen conductivity and due to anomaly morphology. The peak EPB occurrence in the African sector during the June solstice is consistent only with the high ambient density in that region, for there was no coincidence with the maximum vertical drift or the minimum E region Pedersen conductivity.

Relation between the occurrence rate of ESF and the equatorial vertical plasma drift velocity at sunset derived from global observations

“…The climatological features such as seasonal/longitudinal and local time occurrence rate distributions derived from the multi-years magnetic survey compare very well with the global distribution of ESFs derived from plasma depletion observations (e.g. Kil and Heelis, 1998;Huang et al, 2001;Burke et al, 2004;Park et al, 2005). This confirms the reliability of magnetic measurements for detecting these F-region irregularities.…”

“…Global maps of ESF related occurrence rates were derived from satellite observations of local plasma depletions (e.g. Kil and Heelis, 1998;Huang et al, 2001;Palmroth et al, 2001;Burke et al, 2004;Park et al, 2005) or from total electron content observations at a ground-based GPS receiver network (Nishioka et al, 2008). Alternatively, Stolle et al (2006) obtained the ESF distribution from magnetic signatures of the instabilities.…”

Field-aligned current associated with low-latitude plasma blobs as observed by the CHAMP satellite

“…There is a consensus that those FACs are (1) generated by diverted zonal background currents at field-aligned EPB walls and (2) closed at conjugate conducting layers at lower altitude (Aggson et al, 1992;Bhattacharyya and Burke, 2000;Stolle et al, 2006). There is another consensus that blobs are nearconjugate to EPBs: no matter whether (1) the enhanced Efield is mapped along geomagnetic field lines to unperturbed EIA latitudes and lifts up dense plasma from the bottomside (Le et al, 2003;Pimenta et al, 2004;Yokoyama et al, 2007) or (2) the super-fountain effect accumulates plasma at the poleward EPB boundaries (Park et al, 2003;Krall et al, 2009). A natural consequence of these two consensi is: a blob, if any, is a part of the "conjugate conducting layer" of an EPB and closes a portion of its FAC.…”

“…1 is located in the Pacific sector, where EPB activity is high around June solstice (e.g. Kil and Heelis, 1998;Huang et al, 2001;Park et al, 2005;Stolle et al, 2006), and in the Southern winter Hemisphere where blobs are frequently observed (e.g. Watanabe and Oya, 1986;Park et al, 2008b).…”

“…Tsunoda, Correspondence to: J. Park (park@gfz-potsdam.de) 1985; Kil and Heelis, 1998;Huang et al, 2001;Park et al, 2005;Stolle et al, 2006). On the other hand, lowlatitude plasma blobs are regions of abrupt plasma density enhancement observed in the low-latitude ionosphere (poleward of latitudes where EPBs generally occur).…”