Effect of meteor ionization on sporadic‐E observed at Jicamarca

Malhotra, Akshay; Mathews, J. D.; Urbina, Julio

doi:10.1029/2008gl034661

Cited by 17 publications

(18 citation statements)

References 19 publications

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“…The richness of this data set provides a number of clues to the underlying physics. The weak but existent UHF signal indicates that a cascade process drives waves' energy down to 36 cm in size; however, note that it is not necessary to invoke FAI scattering if we do indeed have an inhomogeneous plasma with discontinuities arising from fragmentation [Malhotra et al, 2008]. The total power appears to fall off faster than f −2 and, as noted earlier, is much closer to f −6 [Close et al, 2008], unlike scattering from PMSE, which, in the limit of very large Schmidt numbers, is closer to f −3 .…”

Section: Polarization Propertiesmentioning

confidence: 99%

“…Often, tens of milliseconds after the head echo vanishes, a more persistent echo returns from the nonspecular trail . These trails have also been referred to as range-spread echoes [Malhotra et al, 2008;Mathews et al, 2008], spread meteor echoes [Reddi et al, 2002], and turbulent trail echoes, and they typically endure for less than a few seconds. They have been detected using both HPLA radars [Chapin and Kudeki, 1994;Oppenheim et al, 2009] and, less frequently, lowpower radars and are thought to result from Bragg scattering from field aligned irregularities (FAIs) in the trail [Heritage et al, 1962]; detection results from the growth of plasma instabilities.…”

Section: Introductionmentioning

confidence: 99%

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Polarization and scattering of a long-duration meteor trail

Kelley

Vertatschitsch

et al. 2011

J. Geophys. Res.

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[1] High-power, large-aperture (HPLA) radars have been used over the past two decades to characterize the plasmas formed both around and behind meteoroids as they enter Earth's atmosphere. These plasmas, referred to as heads and trails, respectively, occur with relative frequency (peak head echo detection rate of ∼1/s) but are extremely diverse and have been difficult to define in a general sense. One particular type of plasma, referred to as the nonspecular trail, occurs when the meteoroid travels quasi-parallel to the radar beam with the radar beam lying quasi-perpendicular to the background magnetic field. Reflection is believed to occur from field-aligned irregularities (FAIs) that form after the trail becomes unstable. While FAI scattering pertains to the majority of nonspecular trails that are short in duration, a subset of these trails, referred to as long-duration trails, still remains open to interpretation. In this paper we present a case study analysis of a longduration, nonspecular trail and its associated head echo detected with the Advanced Research Project Agency (ARPA) Long-Range Tracking and Identification Radar (ALTAIR), which is an HPLA radar. These data are unique in that they are high resolution (with monopulse angles), dual frequency, and, most importantly, dual polarized, which allows for unprecedented insight into the scattering process from both heads and trails. First, we determine the velocity and mass of the parent meteoroid, which is a particle weighing more than a milligram and is one of the largest meteoroids ever detected by ALTAIR. Second, we determine the peak plasma density and polarization of the head echo and characterize the unique, yet strong returns in the opposite polarization, which may be due to multiple scattering centers within the range gate. Finally, we examine the polarization properties of the trail and discuss the first conclusive evidence of polarization flipping along the trail striations, which we believe corresponds to sharp gradients at the edges of the trail related to turbulent mixing of a dusty plasma that is elongating along the magnetic field. We look into a new idea, namely, the notion that some nonspecular echoes might correspond to a high Schmidt number, dusty plasma, as is found in and above noctilucent clouds. Our results show how polarized return can aid in scattering diagnostics and that single polarization radars must be used with caution for determining head and trail plasma densities given that some of the return can occur in the "unexpected" channel.

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Section: Polarization Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polarization and scattering of a long-duration meteor trail

Kelley

Vertatschitsch

et al. 2011

J. Geophys. Res.

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“…In order to explain the large time scales over which Es is observed (minutes to hours), it has long been accepted that metallic ions are dominant ions in the formation of Es, and that meteor ionization is the source of these long-lived metallic ions (Malhotra et al, 2008). Thus it is quite natural to speculate that meteor activities may affect the occurrence of Es.…”

Section: Discussionmentioning

confidence: 98%

“…Es consists of a considerable amount of long-lived metallic ions. The mechanism of the wind shear theory is the widely accepted explanation for the formation of Es at mid to low latitudes (Whitehead, 1989;Malhotra et al, 2008). In this theory, vertical shears in the horizontal wind can drive the long-lived metal ions in the lower thermosphere to move vertically and converge into dense plasma layers.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric scintillations at Guilin detected by GPS ground-based and radio occultation observations

Zou

2011

Advances in Space Research

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“…The huge amount of mass flux due to these particles, by some estimates as high a few thousands of kilograms per day (Mathews et al 2001), and thus the threat they pose to our space infrastructure (Caswell et al 1995;Close et al 2010) and the effect they have on E-region aeronomy (Rapp et al 2007;Malhotra et al 2008), makes it imperative that we understand the composition of these bodies. Of particular interest has been the role of fragmentation as a meteoroid disintegration mechanism.…”

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confidence: 99%

Evidence of Meteoroid Fragmentation in Specular Trail Echoes Observed Using Gadanki MST Radar

et al. 2014

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Meteoroids are responsible for deposition of thousands of kilograms of annual mass flux in the Earth's upper atmosphere but the disintegration mechanisms of these bodies, and hence their composition, still remains a subject of debate in the meteor radar community. The role and significance of fragmentation as a meteoroid disintegration mechanism has been of particular interest in the past few years but in contrast to the head echoes, relatively little work has been done to study the effect and extent of fragmentation on trail echoes observed by the high power large aperture radars. Using the 53 MHz Gadanki MST radar, we present examples of radar meteor trails whose evolution cannot be explained with just the aid of classical meteor ablation theory. These examples are analyzed and discussed on a case-by-case basis and it is reported that the evolution of these trails can be explained with the help of fragmentation. This study will form the basis for future modeling efforts of fragmenting meteor trails and has important implications on the form in which the meteoroid mass is deposited in the upper atmosphere.

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Effect of meteor ionization on sporadic‐E observed at Jicamarca

Cited by 17 publications

References 19 publications

Polarization and scattering of a long-duration meteor trail

Polarization and scattering of a long-duration meteor trail

Ionospheric scintillations at Guilin detected by GPS ground-based and radio occultation observations

Evidence of Meteoroid Fragmentation in Specular Trail Echoes Observed Using Gadanki MST Radar

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