Possible Ionospheric Influence on Substorm Onset Location

Elhawary, Reham; Laundal, K. M.; Reistad, Jone Peter; Hatch, Spencer

doi:10.1029/2021gl096691

Cited by 7 publications

(5 citation statements)

References 38 publications

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“…The influence of the IMF By is asymmetric in the northern and southern tail lobes (e.g., Ohma et al., 2019). Thus, it is unlikely that the IMF By controls any onset conditions occurring in the equatorial plane (see also Elhawary et al., 2022). The observed shift in the auroral break‐up position due to IMF By is probably caused by the field line mapping.…”

Section: The Role Of the Solar Wind Energy Inputmentioning

confidence: 99%

Solar Wind Energy Input: The Primary Control Factor of Magnetotail Reconnection Site

Nagai¹,

Shinohara

2022

JGR Space Physics

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Magnetic reconnection occurs in the near-Earth magnetotail in association with the onset of magnetospheric substorms. It converts magnetic energy that is previously stored in the magnetotail to plasma kinetic and thermal energy and produces various dynamic phenomena in the magnetosphere-ionosphere system. It produces fast plasma flows, which are observed more frequently in the premidnight (dusk) sector of the plasma sheet relative to those in the postmidnight (dawn) sector (e.g., Nagai et al., 1998). Satellite observations reveal that the occurrence of auroral brightening is high in the 21-24 magnetic local time (MLT) range (e.g., Frey et al., 2004;Liou et al., 2001). Hence, the tail fast plasma flow results are consistent with the occurrence of auroral brightening corresponding to an onset of substorms.Nagai and Shinohara (2021) reported distribution of in situ magnetic reconnection observations in the near-Earth magnetotail (at radial distances of 20-30 R E ) in association with substorm onsets made by Geotail over the period of 1994-2019. Magnetic reconnection can be observed in the 21-02 MLT (corresponding to the region of Y GSM = +15 to −10 R E ). The important finding of their study is that magnetic reconnection has a short dawn-dusk X-line corresponding to 1-hr MLT. There are several examples of magnetic reconnection in the postmidnight sector of the plasma sheet, and they are mostly observed in highly active geomagnetic conditions and storms by Geotail (Nagai et al., 2013(Nagai et al., , 2015. The Cluster mission observed the ion diffusion region in magnetic reconnection near Y GSM = −5 R E (Eastwood et al., 2010), and the postmidnight event on 21 August 2002 was observed during a storm. During an intense storm on 28 May 2017, the Magnetospheric Multiscale mission made in situ observations of the ion diffusion region at ( et al., 2019). Hence, magnetic reconnection can be formed in the postmidnight sector of the plasma sheet. It may be conceivable that magnetic reconnection observed in the postmidnight sector is a dawnward extension of the X-line initially formed in the premidnight sector. However, magnetic reconnection in the postmidnight sector produces a substorm current system in the same sector. Any dawnward or duskward extension of the X-line is not confirmed (Nagai & Shinohara, 2021).It is reasonable to attribute an onset of magnetic reconnection to pre-conditions in the plasma sheet during the loading period (the growth phase of substorms). In the growth phase of a substorm, magnetic field lines are transported to the magnetotail as the loading process, and the magnetic field intensity increases in the tail lobes (e.g.,

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Section: The Role Of the Solar Wind Energy Inputmentioning

confidence: 99%

Solar Wind Energy Input: The Primary Control Factor of Magnetotail Reconnection Site

Nagai¹,

Shinohara

2022

JGR Space Physics

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“…(2021) and Elhawary et al. (2023). This wave coupling method could be detected by spacecraft magnetometers, but it would likely require an intentional observation campaign to place them appropriately.…”

Section: Discussionmentioning

confidence: 97%

Substorms and Solar Eclipses: A Mutual Information Based Study

Coyle,

Baker,

Chakraborty

et al. 2023

Geophysical Research Letters

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Solar eclipses present a rare glimpse into the impact of ionospheric electrodynamics on the magnetosphere independent of other well studied seasonal influences. Despite decades of study, we still do not have a complete description of the conditions for geomagnetic substorm onset. We present herein a mutual information based study of previously published substorm onsets and the past two decades of eclipses which indicates the likelihood of co‐occurrence is greater than random chance. A plausible interpretation for this relation suggests that the abrupt fluctuations in ionospheric conductivity during an eclipse may influence the magnetospheric preconditions of substorm initiation. While the mechanism remains unclear, this study presents strong evidence of a link between substorm onset and solar eclipses.

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“…For example, we know that substorms excite ionospheric convection (Grocott et al., 2009 ; Provan et al., 2004 ), but we do not know how fast it happens, or how the flow is organized with respect to the substorm bulge (e.g., Laundal et al., 2010 ). Understanding this coupling could also help us to understand how the ionospheric reaction may alter the imposed flows and influence magnetospheric dynamics (e.g., Elhawary et al., 2022 ; Lotko et al., 2014 ). Furthermore, as demonstrated in Section 4.3 , the Lompe technique can be used to estimate frictional heating rates, which is an important driver of dynamics in the upper atmosphere (e.g., Ridley et al., 2006 ).…”

Section: Discussionmentioning

confidence: 99%

Local Mapping of Polar Ionospheric Electrodynamics

Laundal¹,

Reistad²,

Hatch³

et al. 2022

JGR Space Physics

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An accurate description of the state of the ionosphere is crucial for understanding the physics of Earth's coupling to space, including many potentially hazardous space weather phenomena. To support this effort, ground networks of magnetometer stations, optical instruments, and radars have been deployed. However, the spatial coverage of such networks is naturally restricted by the distribution of land mass and access to necessary infrastructure. We present a new technique for local mapping of polar ionospheric electrodynamics, for use in regions with high data density, such as Fennoscandia and North America. The technique is based on spherical elementary current systems (SECS), which were originally developed to map ionospheric currents. We expand their use by linking magnetic field perturbations in space and on ground, convection measurements from space and ground, and conductance measurements, via the ionospheric Ohm's law. The result is a technique that is similar to the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) technique, but tailored for regional analyses of arbitrary spatial extent and resolution. We demonstrate our technique on synthetic data, and with real data from three different regions. We also discuss limitations of the technique and potential areas for improvement.

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Possible Ionospheric Influence on Substorm Onset Location

Cited by 7 publications

References 38 publications

Solar Wind Energy Input: The Primary Control Factor of Magnetotail Reconnection Site

Solar Wind Energy Input: The Primary Control Factor of Magnetotail Reconnection Site

Substorms and Solar Eclipses: A Mutual Information Based Study

Local Mapping of Polar Ionospheric Electrodynamics

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