Analysis of the seasonal variations of equatorial plasma bubble occurrence observed from Haleakala, Hawaii

Abstract

Abstract. Over 300 nights of airglow and GPS scintillation data collected between January 2002 and August 2003 (a period near solar maximum) from the Haleakala Volcano, Hawaii are analyzed to obtain the seasonal trends for the occurrence of equatorial plasma bubbles in the Pacific sector (203 • E). A maximum probability for bubble development is seen in the data in April (45%) and September (83%). A broad maximum of occurrence is seen in the data from June to October (62%). Many of the bubbles observed from June through August occur later in the evening, and, as seen in the optical data, tend to be "fossilized." This suggests that the active growth region during these months is to the west of the observing location. These seasonal trends are consistent with previous data sets obtained both from other groundbased and satellite studies of the occurrence of equatorial bubbles in the Pacific sector. However, our data suggests a much greater probability of bubble occurrence than is seen in other data sets, with bubbles observed on over 40% of the nights studied.

Statistical analysis of radar observed F region irregularities from three longitudinal sectors

“…From CXI, we note the following characteristics: (1) the % occurrence of ESF is maximum during summer solstice month of August and secondary maximum is in equinoctial September month, (2) the % occurrence is minimum during winter-solstice month of February and equinoctial MarchApril, (3) the % occurrence of the plume also follows the seasonal trend of % occurrence of ESF, (4) the % occurrence (6) % of occurrence of ESF during these maximum occurrence seasons is greater (smaller) than 50 % over CXI (SLZ/ROJ), (7) the season of maximum % occurrence of ESF with plume is summer-solstice for CXI/SLZ and is equinox for ROJ, (8) % of occurrence of plume during these maximum occurrence seasons is ∼ 80 % over SLZ, ∼ 50 % over ROJ and ∼ 36 % over CXI, (9) % of occurrence of plume during the minimum occurrence seasons is ∼ 0 % over SLZ, ∼ 16 % over ROJ and ∼ 25 % over CXI, (10) % occurrence of the bottom-type ESF shows seasonal dependence over SLZ/ROJ compared to the no seasonal dependence over CXI. The characteristics noted under (1-3) are known from the previous study by Makela et al (2004). Characteristics noted under (4-10) bring additional aspects in the present study.…”

Simultaneous observations of equatorial F-region plasma depletions over Brazil during the Spread-F Experiment (SpreadFEx)

“…Equatorial plasma irregularities have previously been studied extensively through optical observations of the F-region nightglow emissions on many occasions (e.g., Weber et al, 1978, Mendillo andBaumgardner, 1982;Rohrbaugh et al, 1989;Sahai et al, 1994;Taylor et al, 1997;Santana et al, 2001;Makela et al, 2001Makela et al, , 2004Martinis et al, 2003;Kelley et al, 2002). Here we summarize the plasma depletion properties observed during the campaign using novel twostation measurements of the OI 630.0 nm emission which is produced at the bottomside of the ionospheric F-region, between 250 and 300 km of altitude.…”

“…Depletions have also been extensively studied via their optical signatures in the F-region nightglow emissions mainly using photometers and imagers (e.g., Weber et al, 1978, Mendillo and Baumgardner, 1982, Sahai et al, 1994Makela et al, 2004). Many theoretical and simulation studies of their properties and seasonal characteristics have also been carried out (e.g., Fejer et al, 1985;Haerendel et al, 1992;Abdu, 2001;Abdu et al, 2003;Kudeki et al, 2007).…”

Climatology of nighttime medium-scale traveling ionospheric disturbances (MSTIDs) in the Central Pacific and South American sectors

“…Both the Cornell All-Sky Imager (CASI) and Cornell Narrow-Field Imager (CNFI) employ a 1024 × 1024 pixel CCD array binned to 512 × 512 pixels. Thermal noise is reduced by cooling each imager to −40 • C. The 630.0 nm filtered images are made using an exposure time of 90 s. In addition to studying the properties of MSTIDs, CASI and CNFI have been used extensively for studying equatorial plasma bubbles (EPBs) since the early 2000s (e.g., Kelley, 2002a;Makela et al, 2004). In the current study, data are obtained beginning in September 2006 to coincide with observations from Cerro Tololo, Chile.…”