Articles | Volume 38, issue 2
https://doi.org/10.5194/angeo-38-467-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/angeo-38-467-2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The increase in the curvature radius of geomagnetic field lines preceding a classical dipolarization
Office Geophysik, Ogoori, 838-0141, Japan
Related authors
Osuke Saka
Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2023-32, https://doi.org/10.5194/angeo-2023-32, 2023
Manuscript not accepted for further review
Short summary
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Auroral spirals known as northern lights are a spectacular light show in the polar night sky. Internal processes in the polar ionosphere initiate northern lights by producing charge separations along the field lines. Parallel electric fields generated above the ionosphere by charge separations are steady-state electric fields. They occasionally discharge to produce northern lights, analogous to lightning flash in a thunderstorm.
Osuke Saka
Ann. Geophys., 41, 369–373, https://doi.org/10.5194/angeo-41-369-2023, https://doi.org/10.5194/angeo-41-369-2023, 2023
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Transverse electric fields transmitted from the magnetosphere and those generated by the neutral winds yield a local breakdown of the charge neutrality at the boundaries between the thermosphere and mesosphere. The breakdown may create parallel electric fields in the thermosphere to produce spiral auroras and outflows. This explanation supposes an auroral generator located not in a distant space, but rather in our much nearer upper atmosphere.
Osuke Saka
Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2021-66, https://doi.org/10.5194/angeo-2021-66, 2021
Revised manuscript not accepted
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Auroral spirals known as northern lights are a spectacular light show in the polar night sky. We show that auroral spirals are produced in the polar ionosphere by the internal processes that ensure quasi-neutral equilibrium of the polar ionosphere which is often violated during field line dipolarization. The internal driver produces spiral auroras in a manner different from the field line mapping scenario.
Osuke Saka
Ann. Geophys., 39, 455–460, https://doi.org/10.5194/angeo-39-455-2021, https://doi.org/10.5194/angeo-39-455-2021, 2021
Short summary
Short summary
The ionosphere is a partly ionized medium above the atmosphere. Because of its anisotropic properties, the imposed electric fields from the magnetosphere produce space charge. Polarization electric fields induced in the ionosphere by this process generate ion drifts (Pedersen currents) and plasma evaporation along the field lines, thus achieving a quasi-neutral equilibrium of the ionosphere. The evaporation grows as a large-scale parallel potential structure in the magnetosphere.
Osuke Saka
Ann. Geophys., 37, 381–387, https://doi.org/10.5194/angeo-37-381-2019, https://doi.org/10.5194/angeo-37-381-2019, 2019
Short summary
Short summary
Flow channel extending in north–south directions is produced in the initial pulse of Pi2 pulsations associated with the field line dipolarization. Drifts in the ionosphere of the order of kilometers per second accumulated plasmas at the low-latitude end of the flow channel. The plasma compression in the ionosphere produced field-aligned currents, parallel electric fields, and auroral expansion. We called the compressive ionosphere a "dynamic ionosphere".
O. Saka, K. Hayashi, and M. Thomsen
Ann. Geophys., 32, 1011–1023, https://doi.org/10.5194/angeo-32-1011-2014, https://doi.org/10.5194/angeo-32-1011-2014, 2014
Osuke Saka
Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2023-32, https://doi.org/10.5194/angeo-2023-32, 2023
Manuscript not accepted for further review
Short summary
Short summary
Auroral spirals known as northern lights are a spectacular light show in the polar night sky. Internal processes in the polar ionosphere initiate northern lights by producing charge separations along the field lines. Parallel electric fields generated above the ionosphere by charge separations are steady-state electric fields. They occasionally discharge to produce northern lights, analogous to lightning flash in a thunderstorm.
Osuke Saka
Ann. Geophys., 41, 369–373, https://doi.org/10.5194/angeo-41-369-2023, https://doi.org/10.5194/angeo-41-369-2023, 2023
Short summary
Short summary
Transverse electric fields transmitted from the magnetosphere and those generated by the neutral winds yield a local breakdown of the charge neutrality at the boundaries between the thermosphere and mesosphere. The breakdown may create parallel electric fields in the thermosphere to produce spiral auroras and outflows. This explanation supposes an auroral generator located not in a distant space, but rather in our much nearer upper atmosphere.
Osuke Saka
Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2021-66, https://doi.org/10.5194/angeo-2021-66, 2021
Revised manuscript not accepted
Short summary
Short summary
Auroral spirals known as northern lights are a spectacular light show in the polar night sky. We show that auroral spirals are produced in the polar ionosphere by the internal processes that ensure quasi-neutral equilibrium of the polar ionosphere which is often violated during field line dipolarization. The internal driver produces spiral auroras in a manner different from the field line mapping scenario.
Osuke Saka
Ann. Geophys., 39, 455–460, https://doi.org/10.5194/angeo-39-455-2021, https://doi.org/10.5194/angeo-39-455-2021, 2021
Short summary
Short summary
The ionosphere is a partly ionized medium above the atmosphere. Because of its anisotropic properties, the imposed electric fields from the magnetosphere produce space charge. Polarization electric fields induced in the ionosphere by this process generate ion drifts (Pedersen currents) and plasma evaporation along the field lines, thus achieving a quasi-neutral equilibrium of the ionosphere. The evaporation grows as a large-scale parallel potential structure in the magnetosphere.
Osuke Saka
Ann. Geophys., 37, 381–387, https://doi.org/10.5194/angeo-37-381-2019, https://doi.org/10.5194/angeo-37-381-2019, 2019
Short summary
Short summary
Flow channel extending in north–south directions is produced in the initial pulse of Pi2 pulsations associated with the field line dipolarization. Drifts in the ionosphere of the order of kilometers per second accumulated plasmas at the low-latitude end of the flow channel. The plasma compression in the ionosphere produced field-aligned currents, parallel electric fields, and auroral expansion. We called the compressive ionosphere a "dynamic ionosphere".
O. Saka, K. Hayashi, and M. Thomsen
Ann. Geophys., 32, 1011–1023, https://doi.org/10.5194/angeo-32-1011-2014, https://doi.org/10.5194/angeo-32-1011-2014, 2014
Related subject area
Subject: Magnetosphere & space plasma physics | Keywords: Magnetospheric configuration and dynamics
Unsupervised classification of simulated magnetospheric regions
The fate of O+ ions observed in the plasma mantle: particle tracing modelling and cluster observations
A multi-fluid model of the magnetopause
Magnetodisc modelling in Jupiter's magnetosphere using Juno magnetic field data and the paraboloid magnetic field model
Maria Elena Innocenti, Jorge Amaya, Joachim Raeder, Romain Dupuis, Banafsheh Ferdousi, and Giovanni Lapenta
Ann. Geophys., 39, 861–881, https://doi.org/10.5194/angeo-39-861-2021, https://doi.org/10.5194/angeo-39-861-2021, 2021
Short summary
Short summary
Spacecraft missions do not always record observations at the highest possible resolution, and the so-called burst mode is switched on only occasionally. It is of paramount importance that processes of interest are sampled in burst mode. At the moment, many missions rely on a scientist in the loop, who decides when to trigger burst mode by looking at the preview data. Our work constitutes a first step towards making this decision automatic to improve mission operations and decrease human bias.
Audrey Schillings, Herbert Gunell, Hans Nilsson, Alexandre De Spiegeleer, Yusuke Ebihara, Lars G. Westerberg, Masatoshi Yamauchi, and Rikard Slapak
Ann. Geophys., 38, 645–656, https://doi.org/10.5194/angeo-38-645-2020, https://doi.org/10.5194/angeo-38-645-2020, 2020
Short summary
Short summary
The Earth's atmosphere is constantly losing molecules and charged particles, amongst them oxygen ions or O+. Quantifying this loss provides information about the evolution of the atmosphere on geological timescales. In this study, we investigate the final destination of O+ observed with Cluster satellites in a high-altitude magnetospheric region (plasma mantle) by tracing the particles forward in time using simulations. We find that approximately 98 % of O+ escapes the Earth's magnetosphere.
Roberto Manuzzo, Francesco Califano, Gerard Belmont, and Laurence Rezeau
Ann. Geophys., 38, 275–286, https://doi.org/10.5194/angeo-38-275-2020, https://doi.org/10.5194/angeo-38-275-2020, 2020
Short summary
Short summary
We investigate the magnetopause stability and mixing using a new three-fluid model aimed at reproducing the system configuration obtained directly from satellite data. This
realisticmodel is a basic starting point for numerical simulations; however, the realistic three-fluid equilibrium presented in this paper should allow this work to be taken a step further and could be applied to other experimental cases in the future.
Ivan A. Pensionerov, Elena S. Belenkaya, Stanley W. H. Cowley, Igor I. Alexeev, Vladimir V. Kalegaev, and David A. Parunakian
Ann. Geophys., 37, 101–109, https://doi.org/10.5194/angeo-37-101-2019, https://doi.org/10.5194/angeo-37-101-2019, 2019
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In the present work we used unique data on the magnetic field in the
Jovian magnetosphere measured by the Juno spacecraft. The data allowed
us to determine optimal parameters of the magnetodisc in the paraboloid
magnetospheric model and find the ways to qualitatively improve the
model.
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Short summary
The first 10 min interval of Pi2 onset is the most active period of substorms composed of field line deformations associated with an increase in curvature radius of flux tubes and their longitudinal expansion. The flux tube deformations were triggered by the ballooning instability of slow magnetoacoustic waves upon arrival of the dipolarization front from the tail. They preceded the classical dipolarization caused by the reduction of cross-tail currents and resulting pileup of the field lines.
The first 10 min interval of Pi2 onset is the most active period of substorms composed of field...