Interhemispheric Asymmetries in Magnetospheric Energy Input

Zesta, E.; Boudouridis, A.; Weygand, J. M.; Yizengaw, E.; Moldwin, M. B.; Chi, Peter

doi:10.1002/9781118929216.ch1

Cited by 8 publications

(14 citation statements)

References 65 publications

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“…In contrast, in the low latitudes the southern regions experience more prominent poststorm density enhancements. While it is possible that this asymmetry is created by the ionosonde location biases and differences in the operation period of the ionosondes (see Figure ), prior studies have found a similar asymmetrical feature in the global total electron content (TEC) measurements from ground GPS receivers [ Mendillo et al ., ; Zesta et al ., ]. These studies and the references therein reported that the TEC amounts were stronger in the Northern Hemisphere and the North‐South TEC ratios were much more pronounced in the higher latitudes compared to the lower latitudes.…”

Section: Resultsmentioning

confidence: 74%

A global scale picture of ionospheric peak electron density changes during geomagnetic storms

Kumar

Parkinson

2017

Space Weather

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Changes in ionospheric plasma densities can affect society more than ever because of our increasing reliance on communication, surveillance, navigation, and timing technology. Models struggle to predict changes in ionospheric densities at nearly all temporal and spatial scales, especially during geomagnetic storms. Here we combine a 50 year (1965–2015) geomagnetic disturbance storm time (Dst) index with plasma density measurements from a worldwide network of ~132 vertical incidence ionosondes to develop a picture of global scale changes in peak plasma density due to geomagnetic storms. Vertical incidence ionosondes provide measurements of the critical frequency of the ionospheric F2 layer (foF2), a direct measure of the peak electron density (NmF2) of the ionosphere. By dissecting the NmF2 perturbations with respect to the local time at storm onset, season, and storm intensity, it is found that (i) the storm‐associated depletions (negative storm effects) and enhancements (positive storm effects) are driven by different but related physical mechanisms, and (ii) the depletion mechanism tends to dominate over the enhancement mechanism. The negative storm effects, which are detrimental to HF radio links, are found to start immediately after geomagnetic storm onset in the nightside high‐latitude ionosphere. The depletions in the dayside high‐latitude ionosphere are delayed by a few hours. The equatorward expansion of negative storm effects is found to be regulated by storm intensity (farthest equatorward and deepest during intense storms), season (largest in summer), and time of day (generally deeper on the nightside). In contrast, positive storm effects typically occur on the dayside midlatitude and low‐latitude ionospheric regions when the storms are in the main phase, regardless of the season. Closer to the magnetic equator, moderate density enhancements last up to 40 h during the recovery phase of equinox storms, regardless of the local time. Strikingly, high‐latitude plasma densities are moderately enhanced for up to 60 h prior to the actual onset of storms during the equinoxes and summer; a potential precursor of a geomagnetic storm.

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Section: Resultsmentioning

confidence: 74%

A global scale picture of ionospheric peak electron density changes during geomagnetic storms

Kumar

Parkinson

2017

Space Weather

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“…Past studies dealing with interhemispheric asymmetries of ULF waves have focused on ULF wave power obtained from ground-based magnetometers located at conjugate locations from cusp latitudes to low latitudes. The discussed influence factors include local precipitation of electrons (Posch et al, 1999), ionospheric conductivity (Obana et al, 2005;Surkan & Lanzerotti, 1974), and the state of the ionosphere (Zesta et al, 2016). In contrast to single-point observations made with ground-based magnetometers, low Earth-orbiting satellites offer the capability of an extensive survey over the full range of longitudes and latitudes.…”

Section: 1029/2019ja027103mentioning

confidence: 99%

Features of Nightside ULF Wave Activity in the Ionosphere

et al. 2019

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We investigate the features of nightside ultralow frequency (ULF) waves in the ionosphere using electric field data in the DC/ULF range observed by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite over a~5.5-year period from May 2005 to November 2010. The ULF wave events are recognized by an automatic detection algorithm, and a superposed epoch analysis is performed to study the characteristics of ULF waves during geomagnetic storms. The results show that (1) ULF waves of both nonmagnetospheric and magnetospheric origins occur in the ionosphere; (2) nonmagnetospheric ULF waves present seasonal variations but have no clear response to storms; (3) magnetospheric ULF waves show clear association with the recovery phase of storms but have no obvious seasonal variations; and (4) an interhemispheric asymmetry with higher magnetospheric ULF wave occurrence rate in the Southern Hemisphere particularly around storms can be partly explained by the fact that more of selected isolated storms occurred during summer in the Northern Hemisphere (NH), hence higher conductivity in the NH. However, an analysis of few storms during equinoxes also shows a minor asymmetry. These results still indicate that the ionospheric conductivity in the Southern Hemisphere would be lower than in the NH at nighttime. Plain Language SummaryPast knowledge of ultralow frequency (ULF) waves are mainly based on single-point or multipoint observations from high-altitude satellites or ground-based magnetometers. Satellites at low altitudes offer the capability of a global survey of ULF waves that help us to deeply understand ULF waves in the ionosphere. The origins of ULF fluctuations observed by low-altitude satellites are still controversial to date. In this work we statistically explore the characteristics of ULF waves in the ionosphere originated from different sources (e.g., magnetosphere, ionosphere, and atmosphere). Higher occurrence rate of ULF waves from the magnetosphere is in the Southern Hemisphere, indicating lower conductivity there allowing waves more easily propagating into the ionosphere. We also find that ULF waves from different sources have different behaviors with respect to seasonal variations and the response to the strong external perturbations. This study will promote our understanding of ULF waves and their effects on dynamics of the ionosphere.

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“…These products are listed below, along with references to existing or developing examples of their generation: New mapping products Global maps of magnetospheric mass density as a function of L and local time including location and characterization of the plasmapause, based on field line resonance‐based remote sensing (e.g., Chi et al, ; Menk & Waters, ). Global and/?or regional maps of equatorial electrojets (Yizengaw et al, , ) and auroral zone equivalent currents (Weygand et al, ). Routine production of maps of global equivalent current data from magnetometers and other instruments such as the SuperDARN radars. Derivation of the full vector electric current system in the ionosphere requires simultaneous magnetic field data from space and the ground (Lotko, ). Maps of magnetic perturbations and the synoptic open/?closed boundary of the magnetosphere in both polar caps (Urban et al, ). Statistical maps of magnetic perturbations (Pothier et al, ; Weimer et al, ) and various categories of ULF waves as functions of solar wind/?IMF drivers and/?or geomagnetic activity. Quick‐look event‐specific maps and/?or magnetic keograms of Pc5 ULF waves (Kozyreva et al, ) and other ULF wave categories superposed on magnetospheric regions such as the polar cap, auroral zone, plasmatrough, and plasmasphere. Global and regional maps and parameterizations of geomagnetic disturbances (and time derivatives) that drive ground‐induced currents (e.g., Carter et al, ; Love et al, ; Woodroffe et al, ). Interhemispheric comparisons of regional ULF wave activity (e.g., Kim et al, , ; Zesta et al, ), electrojet currents, and cusp and substorm phenomena, in order to understand the way energy from the solar wind is transmitted asymmetrically to Earth's high‐latitude regions. New activity indices, indicators, and tools Regional activity indices ( K indices) specifying localized activity. Stacked plots of time series of “virtual magnetometers” at fixed local times. Visual products using the ULF index (Kozyreva et al, ; Pilipenko et al, ). Development of more “interpretive” capabilities such as automated identification and location of substorms (Murphy et al, ) and Pi2 pulsations. Shared software tools for analysis of magnetometer data, as is done, for example, in the seismic and astrophysical communities. …”

Section: Higher‐level Data Productsmentioning

confidence: 99%

“…Interhemispheric comparisons of regional ULF wave activity (e.g., Kim et al, , ; Zesta et al, ), electrojet currents, and cusp and substorm phenomena, in order to understand the way energy from the solar wind is transmitted asymmetrically to Earth's high‐latitude regions.…”

Section: Higher‐level Data Productsmentioning

confidence: 99%

“…g. Global and regional maps and parameterizations of geomagnetic disturbances (and time derivatives) that drive ground-induced currents (e.g., Carter et al, 2016;Love et al, 2016;Woodroffe et al, 2016). h. Interhemispheric comparisons of regional ULF wave activity (e.g., Kim et al, 2013Kim et al, , 2015Zesta et al, 2016), electrojet currents, and cusp and substorm phenomena, in order to understand the way energy from the solar wind is transmitted asymmetrically to Earth's high-latitude regions. 2.…”

Section: Higher-level Data Productsmentioning

confidence: 99%

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The Future of Ground Magnetometer Arrays in Support of Space Weather Monitoring and Research

Engebretson

Zesta

2017

Space Weather

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A community workshop was held in Greenbelt, Maryland, on 5–6 May 2016 to discuss recommendations for the future of ground magnetometer array research in space physics. The community reviewed findings contained in the 2016 Geospace Portfolio Review of the Geospace Section of the Division of Atmospheric and Geospace Science of the National Science Foundation and discussed the present state of ground magnetometer arrays and possible pathways for a more optimal, robust, and effective organization and scientific use of these ground arrays. This paper summarizes the report of that workshop to the National Science Foundation (Engebretson & Zesta, ) as well as conclusions from two follow‐up meetings. It describes the current state of U.S.‐funded ground magnetometer arrays and summarizes community recommendations for changes in both organizational and funding structures. It also outlines a variety of new and/or augmented regional and global data products and visualizations that can be facilitated by increased collaboration among arrays. Such products will enhance the value of ground‐based magnetometer data to the community's effort for understanding of Earth's space environment and space weather effects.

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Interhemispheric Asymmetries in Magnetospheric Energy Input

Cited by 8 publications

References 65 publications

A global scale picture of ionospheric peak electron density changes during geomagnetic storms

A global scale picture of ionospheric peak electron density changes during geomagnetic storms

Features of Nightside ULF Wave Activity in the Ionosphere

The Future of Ground Magnetometer Arrays in Support of Space Weather Monitoring and Research

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