Coordinated stable auroral red arc observations: Relationship to plasma convection

Foster, J. C.; Buonsanto, M. J.; Mendillo, M.; Nottingham, D.; Rich, F. J.; Denig, W. F.

doi:10.1029/93ja03140

Cited by 108 publications

(142 citation statements)

References 22 publications

(5 reference statements)

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“…During storms, equatorward motions have the trough's poleward wall over those sites during the first ∼24-30 h of a storm. This is a well documented effect with past examples seen at Millstone Hill, just poleward of Wallops Island, in case studies presented by Mendillo et al (1987), Foster et al (1994 and Baumgardner et al (2007). In each case, the irregular patterns of enhanced F-layer plasma poleward of the trough are the clear signatures of precipitation-induced ionization.…”

Section: Comparisons Of Characteristic Storm Patternssupporting

confidence: 76%

“…Modulating these broad photo-chemical depletions (termed the "DC negative phase" by Rodger et al, 1989) are the local time ("AC negative phase") effects of equatorward motions of the ionospheric trough to the latitudes of Wallops Island and Hobart (L ∼ 2.5 to 3) near 03:00 local time. Such motions of the trough during storms are well known effects (Moffett and Quegan, 1983;Whalen, 1989), and particularly so in the Wallops Island longitude sector (Mendillo et al, 1974;Foster et al, 1994;Baumgardner et al, 2007). Equatorward motions of the trough and its auroral-precipitationinduced poleward wall also occur in the Southern Hemisphere, as documented clearly in ionospheric storm effects upon NmF2 in the study by Rodger et al (1989).…”

Section: Comparisons Of Characteristic Storm Patternsmentioning

confidence: 55%

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Ionospheric storms at geophysically-equivalent sites – Part 2: Local time storm patterns for sub-auroral ionospheres

Mendillo

Narvaez

2010

Ann. Geophys.

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Abstract. The response of the mid-latitude ionosphere to geomagnetic storms depends upon several pre-storm conditions, the dominant ones being season and local time of the storm commencement (SC). The difference between a site's geographic and geomagnetic latitudes is also of major importance since it governs the blend of processes linked to solar production and magnetospheric input, respectively. Case studies of specific storms using ionospheric data from both hemispheres are inherently dominated by seasonal effects and the various local times versus longitude of the SCs. To explore inter-hemispheric consistency of ionospheric storms, we identify "geophysically-equivalent-sites" as locations where the geographic and geomagnetic latitudes have the same relationship to each other in both hemispheres. At the longitudes of the dipole tilt, the differences between geographic and geomagnetic latitudes are at their extremes, and thus these are optimal locations to see if pre-conditioning and/or storm-time input are the same or differ between the hemispheres.In this study, we use ionosonde values of the F2-layer maximum electron density (NmF2) to study geophysical equivalency at Wallops Island (VA) and Hobart (Tasmania), using statistical summaries of 206 events during solar cycle #20. We form average patterns of NmF2 (%) versus local time over 7-day storm periods that are constructed in ways that enhance the portrayal of the average characteristic features of the positive and negative phases of ionospheric storms. The results show a consistency between four local time characteristic patterns of storm-induced perturbations, and thus for the average magnitudes and time scales of the processes that cause them in each hemisphere. Subtle differences linked to small departures from pure geophysical equivalency point to a possible presence of hemispheric asymmetries governedCorrespondence to: C. Narvaez (cnarvaez@bu.edu) by the non-mirror-image of geomagnetic morphology in each hemisphere.

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Section: Comparisons Of Characteristic Storm Patternssupporting

confidence: 76%

Section: Comparisons Of Characteristic Storm Patternsmentioning

confidence: 55%

Ionospheric storms at geophysically-equivalent sites – Part 2: Local time storm patterns for sub-auroral ionospheres

Mendillo

Narvaez

2010

Ann. Geophys.

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“…Thus, the onset of the negative phase is due both to dynamics and chemistry. Consistent with this behavior is the pronounced intrusion of trough/plasmapause/ring current effects that lead to the appearance of stable auroral red (SAR) arcs (Foster et al, 1994;Baumgardner et al, 2008). Condition (3) deals with storm-time auroral heating of the thermosphere by precipitating particles and currents (Joule heating), processes that generally occurs poleward of L∼2.5 (except during the most severe storms).…”

Section: Introductionmentioning

confidence: 94%

Ionospheric storms at geophysically-equivalent sites – Part 1: Storm-time patterns for sub-auroral ionospheres

Mendillo

Narvaez

2009

Ann. Geophys.

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Abstract. The systematic study of ionospheric storms has been conducted primarily with groundbased data from the Northern Hemisphere. Significant progress has been made in defining typical morphology patterns at all latitudes; mechanisms have been identified and tested via modeling. At higher mid-latitudes (sites that are typically sub-auroral during non-storm conditions), the processes that change significantly during storms can be of comparable magnitudes, but with different time constants. These include ionospheric plasma dynamics from the penetration of magnetospheric electric fields, enhancements to thermospheric winds due to auroral and Joule heating inputs, disturbance dynamo electrodynamics driven by such winds, and thermospheric composition changes due to the changed circulation patterns. The ∼12 • tilt of the geomagnetic field axis causes significant longitude effects in all of these processes in the Northern Hemisphere. A complementary series of longitude effects would be expected to occur in the Southern Hemisphere. In this paper we begin a series of studies to investigate the longitudinal-hemispheric similarities and differences in the response of the ionosphere's peak electron density to geomagnetic storms.The ionosonde stations at Wallops Island (VA) and Hobart (Tasmania) have comparable geographic and geomagnetic latitudes for sub-auroral locations, are situated at longitudes close to that of the dipole tilt, and thus serve as our candidate station-pair choice for studies of ionospheric storms at geophysically-comparable locations. They have an excellent record of observations of the ionospheric penetration frequency (foF2) spanning several solar cycles, and thus are suitable for long-term studies. During solar cycle #20 (1964)(1965)(1966)(1967)(1968)(1969)(1970)(1971)(1972)(1973)(1974)(1975)(1976), 206 geomagnetic storms occurred that had A p ≥30 or K p ≥5 for at least one day of the storm. Our analCorrespondence to: C. Narvaez (cnarvaez@bu.edu) ysis of average storm-time perturbations (percent deviations from the monthly means) showed a remarkable agreement at both sites under a variety of conditions. Yet, small differences do appear, and in systematic ways. We attempt to relate these to stresses imposed over a few days of a storm that mimic longer term morphology patterns occurring over seasonal and solar cycle time spans. Storm effects versus season point to possible mechanisms having hemispheric differences (as opposed to simply seasonal differences) in how solar wind energy is transmitted through the magnetosphere into the thermosphere-ionosphere system. Storm effects versus the strength of a geomagnetic storm may, similarly, be related to patterns seen during years of maximum versus minimum solar activity.

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“…It is possible that the absence of southward wave activity on this night is because any aurorally generated waves were filtered out by equatorward winds. Equatorward neutral wind flow has been shown to occur in the thermosphere during auroral activity [Foster et al, 1994] Table 3. A non imaging photometric study of gravity waves in the southern auroral zone (not shown in …”

Section: The All-sky Imaging Systemmentioning

confidence: 99%

Mesospheric gravity wave imaging at a subauroral site: First results from Millstone Hill

Smith¹,

Mendillo²,

Baumgardner³

et al. 2000

J. Geophys. Res.

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Coordinated stable auroral red arc observations: Relationship to plasma convection

Cited by 108 publications

References 22 publications

Ionospheric storms at geophysically-equivalent sites – Part 2: Local time storm patterns for sub-auroral ionospheres

Ionospheric storms at geophysically-equivalent sites – Part 2: Local time storm patterns for sub-auroral ionospheres

Ionospheric storms at geophysically-equivalent sites – Part 1: Storm-time patterns for sub-auroral ionospheres

Mesospheric gravity wave imaging at a subauroral site: First results from Millstone Hill

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