Variations in total electron content and other ionospheric parameters associated with magnetic storms

Hibberd, F. H.; Ross, William T.

doi:10.1029/jz072i021p05331

Cited by 45 publications

(14 citation statements)

References 23 publications

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“…Thus, percent-change time sequences are simply averaged to form <D st (τ , %)> i , where τ is at hourly intervals from the UT of the SC, and i represents sample size, e.g., the number of storms in winter months, or the number of storms during solar minimum years, etc. This type of analysis was first introduced for the study of geomagnetic storms, and then popularized for use with ionospheric storms by Matsushita (1959) with ionosonde data, and later for TEC data by Hibberd and Ross (1967) and Mendillo (1971).…”

Section: Formation Of Statistical Patternsmentioning

confidence: 99%

“…1, the solar flux parameter F10.7 portrays the typical pattern of a steeper rise than decline in solar activity. We have divided this cycle into four phases: Minimum (onset in October 1964through 1965, plus 1975through June 1976, Rising (1966 and1967), Maximum (1968Maximum ( through 1970 and Declining (1971Declining ( through 1974. Geomagnetic activity, as represented by the daily index A p , does not following this pattern closely, leading to the discovery that coronal holes are the dominant cause of geomagnetic activity during the declining phases.…”

Section: Effects During Different Phases Of the Solar Cyclementioning

confidence: 99%

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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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Section: Formation Of Statistical Patternsmentioning

confidence: 99%

Section: Effects During Different Phases Of the Solar Cyclementioning

confidence: 99%

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

Mendillo

Narvaez

2009

Ann. Geophys.

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“…Examples on the Feb. 11, 1958 storm given by Matuura (1963) are illustrated in Figure 5. Decreases in Nr on one or two days after sudden commencement have been observed by Taylor (1961), Nakata (1966), Hibberd and Ross (1967), Titheridge andAndrews (1967), Mendillo et al (1969) and Taylor and Earnshaw (1969). The vertical structure of the F-region at Kokubunji during the sharp decrease on Feb. 11, 1958 is shown in Figure 6.…”

Section: Hours After Start Of Stormmentioning

confidence: 74%

Theoretical models of ionospheric storms

Matuura¹

1972

Space Sci Rev

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“…Recent works by Pirog et al [2006] and Romanova et al [2006] found that, both in winter and summer seasons, the ionospheric disturbances are positive at low latitudes in the daytime. A positive response is also typical for lower levels of geomagnetic activity [ Hibberd and Ross , 1967].…”

Section: Introductionmentioning

confidence: 99%

Short‐term relationship of total electron content with geomagnetic activity in equatorial regions

et al. 2008

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The short‐term relationship between equatorial ionosphere and geomagnetic activity is examined. Hourly averages of the total electron content (TEC) and critical frequency of the F2 layer (foF2) are compared with the Dst index, a proxy for equatorial geomagnetic activity, at three local times (0700–0800, 1200–1300, and 1600–1700 LT) from March 1998 to August 1999. Owing to the geomagnetic latitude and local times used, positive storms, almost exclusively, are observed (cf. Prölss, 1995). While foF2 measurements over an extended period (∼10 years) have been studied (Matsushita, 1959) and TEC and foF2 are coupled, TEC measurements can provide a significantly better signal‐to‐noise ratio. At timescales of 2–3, 3–5, 5–9, and 9–11 days, there are significant correlations (∼0.4 at local noon, when all the data are included) between TEC and Dst. These correlations increase from morning to afternoon. By comparison, correlations between foF2 and Dst are significantly smaller, ∼0.2 (near the noise level) at local noon. Even during geomagnetically quiet times (Dst > −20), a clear correlation (0.21, which exceeds the 95% confidence level by 0.05) is seen between TEC and Dst at the shortest timescale examined. As geomagnetic activity increases, the correlations increase rapidly. For example, when moderate levels of geomagnetic activity (Dst > −50) are included for observations at local noon, distinct correlations (∼0.3) are seen and persist for all but the longest timescale; with higher levels of geomagnetic activity included, there are distinct correlations at all the timescales examined. The presence of a significant correlation at quiet conditions and persistence of the correlation at moderate levels of activity are both unexpected.

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Variations in total electron content and other ionospheric parameters associated with magnetic storms

Cited by 45 publications

References 23 publications

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

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

Theoretical models of ionospheric storms

Short‐term relationship of total electron content with geomagnetic activity in equatorial regions

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