Bibliography

Subauroral Flow Channel Structures and Auroral Undulations Triggered by Kelvin-Helmholtz Waves

We investigate Kelvin-Helmholtz (K-H) waves on/near the magnetopause and surface waves near the plasmapause—in the outer region of the plasmasphere: in the hot zone—by utilizing multi-instrument/satellite observations. Our main aim is to study how the K-H waves and the K-H instability mechanisms impacted the subauroral and auroral regions during the geomagnetic storms of May 27–29 and July 16, 2017. For the subauroral region, we specify the structured flows as Sub-Auroral Polarization Streams Wave Structures (SAPS-WS) and the combined flows—created by Abnormal Sub-Auroral Ion Drifts (ASAID) and SAID or SAPS—as a complex equatorward-poleward ASAID-SAID or SAPS-ASAID. For the auroral zone, we identify the large auroral undulations appearing inside the auroral zone. The correlated observations of the K-H waves, the structured or complex subauroral flows and large auroral undulations, and the local geomagnetic field oscillations confirm the connections of both the subauroral flows and the auroral undulations with the K-H waves via the eigenfrequency of the Near-Earth Plasma Sheet (NEPS) resonator activated by the K-H waves. For the first time, we demonstrate the simultaneous detections of K-H waves near the magnetopause and surface waves near the plasmapause in the hot zone on July 16, 2017, and conclude their coupling via the NEPS resonator s eigenfrequency. Thus, the surface waves near the plasmapause were the manifestation of the undulating (or rippled) earthward inner boundary of the NEPS that led to the development of ASAID-SAID/SAPS-ASAID or SAPS-WS in the subauroral region and to the large auroral undulation inside the auroral zone.

Horvath, Ildiko; Lovell, Brian;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2021     DOI: 10.1029/2021JA029144

ASAID/SAPS/SAPS-WS; auroral undulations; hot zone; K-H instability

Investigating Magnetosphere-Ionosphere-Thermosphere (M-I-T) Coupling Occurring During the 7\textendash8 November 2004 Superstorm

In this study, we investigate the shock-sheath driven 7\textendash8 November 2004 superstorm for its flux transfer events and resultant flow channel (FC) events and associated neutral (D_N) and electron (Ne) density features in order to understand better the underlying coupled magnetosphere (M) and ionosphere (I) processes and responses in the thermosphere (T). We focus on the (i) subauroral, auroral, and polar cap regions, (ii) localized D_N increases and associated Ne features and FCs developed, and (iii) energy deposition occurred. Results show the development of localized D_N increases (1) within/over FCs and associated enhanced small-scale field aligned currents suggesting Joule heating driving upwelling during forward and reverse polar convections, (2) appearing with Ne increases during storm-enhanced density (SED) events suggesting strong M-I-T coupling and with Ne depletions during plasmaspheric erosion events suggesting weak M-I-T coupling, and (3) in the thermosphere\textquoterights increasing NO and continuously low O/N₂ composition regions. During erosion events, strong storm-time subauroral polarization streams (SAPS) E fields developed. Meanwhile the well-developed plasmapause appeared with decreased total electron content (TEC) on its poleward side and with increased TEC and Ne (appearing as a shoulder feature that is the signature of SED) on its equatorward side. From these we conclude that although strong M-I-T coupling was apparent during SED events, M-I-T coupling was also strong during erosion events when the combination of strong convection E field and large storm-time SAPS E fields eroded the high-latitude region and thus decreased the high-latitude Ne and TEC.

Horvath, Ildiko; Lovell, Brian;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2020

YEAR: 2020     DOI: 10.1029/2019JA027484

flow channels; large-scale FACs; localized neutral density increases; nitric oxide (NO); Poynting flux; type-1 and type-2 aurorae

Investigating Ionospheric Heat Sources and Resultant Thermospheric Responses

During this project, the team conducted detailed investigations on various complex geophysical processes occurring in the coupled system of solar wind, magnetosphere, ionosphere

Horvath, Ildiko;

Published by:       Published on:

YEAR: 2020     DOI:

Positive and negative ionospheric storms occurring during the 15 May 2005 geomagnetic superstorm

This study focuses on the 15 May 2005 geomagnetic superstorm and aims to investigate the global variation of positive and negative storm phases and their development. Observations are provided by a series of global total electron content maps and multi-instrument line plots. Coupled Thermosphere-Ionosphere-Plasmasphere electrodynamics (CTIPe) simulations are also employed. Results reveal some sunward streaming plumes of storm-enhanced density (SED) over Asia and a well-developed midlatitude trough over North America forming isolated positive and negative storms, respectively. The simultaneous development of positive and negative storms over North America is also shown. Then, some enhanced auroral ionizations maintained by strong equatorward neutral winds appeared in the depleted nighttime ionosphere. Meanwhile, the northern nighttime polar region became significantly depleted as the SED plume plasma could not progress further than the dayside cusp. Oppositely, a polar tongue of ionization (TOI) developed in the daytime southern polar region. According to CTIP simulations, solar heating locally maximized (minimized) over the southern (northern) magnetic pole. Furthermore, strong upward surges of molecular-rich air created O/N₂\ decreases both in the auroral zone and in the trough region, while some SED-related downward surges produced O/N₂\ increases. From these results we conclude for the time period studied that (1) composition changes contributed to the formation of positive and negative storms, (2) strengthening polar convection and increasing solar heating of the polar cap supported polar TOI development, and (3) a weaker polar convection and minimized solar heating of the polar cap aided the depletion of polar plasma.

Horvath, Ildiko; Lovell, Brian;

Published by: Journal of Geophysical Research: Space Physics      Published on: 09/2015

YEAR: 2015     DOI: 10.1002/2015JA021206

CTIP/CTIPe simulations; Ionospheric storms; midlatitude trough; polar TOI; SED plume; thermospheric composition