Kevin Pham

Efficiency of Electromagnetic Energy Transfer from Solar Wind to Ionosphere through Magnetospheric Ultra-Low Frequency Waves

whawkins — Wed, 13 Aug 2025 20:10:55 +0000

Efficiency of Electromagnetic Energy Transfer from Solar Wind to Ionosphere through Magnetospheric Ultra-Low Frequency Waves whawkins Wed, 08/13/2025 - 14:10

Author:

whawkins

Aug 13, 2025

(a) 5-200 s bandpassed $S_{A//}$ mapped to the ionospheric altitude and averaged over the four-hour interval. (b) 5-200s bandpassed $S_{A//}$ in the 7 MLT plane. (c) 4.5-5.5 mHz root-integrated power (RIP) of radial electric field $E_r$ in the equatorial plane. (d) 4.5-5.5 mHz RIP of azimuthal magnetic field $B_\phi$ in the meridional plane of 7 MLT. (e-f) Field-aligned keograms of $E_{mrd}$ and $B_\phi$ along the green field line with the largest $S_{A//}$. The green curve in (b) and (d) is a magnetic field line in the 7 MLT plane connecting to the green cross in (a) which marks the location with the peak $S_{A//}$. This field line crosses the equatorial plane at the green cross in (c).

Geophysical Research Letter: Scientists have long been interested in how energy from the Sun is transferred into Earth’s space environment. The Earth's magnetosphere is an important intermediate environment between the solar wind and the upper atmosphere. Consisting of plasma and magnetic field, the magnetosphere is full of intrinsic plasma waves that are capable of energy transport, particularly a group in the frequency range of a few to a few tens Millihertz that are especially efficient in connecting the magnetosphere and the ionosphere. However, due to the global presence and propagation features of those waves, it has been very challenging with measurements from a limited number of locations to understand the efficiency of the wave based energy transfer mechanism. This study uses a first-principles computational model that can resolve the fundamental physics related to the low frequency plasma waves, to carry out idealized numerical experiments to investigate the electromagnetic energy flow in response to undulating solar wind. The theoretical study provides new understanding of the significance of the electromagnetic energy flow and its dependence on different parameters.

Penetrating electric field with/without disturbed electric fields During the 7-8 July 2022 geomagnetic storm simulated by MAGE and observed by ICON MIGHTI

whawkins — Wed, 09 Apr 2025 21:17:49 +0000

Penetrating electric field with/without disturbed electric fields During the 7-8 July 2022 geomagnetic storm simulated by MAGE and observed by ICON MIGHTI whawkins Wed, 04/09/2025 - 15:17

Author:

whawkins

Apr 9, 2025

7 July, MAGE simulation and ICON observation of zonal thermospheric winds and ion drifts. ICON MIGHTI observed zonal wind and MAGE simulations along the MIGHTI sampling points (right) are plotted. Data from each orbit are plotted according to the longitude. The starting time for each orbit is provided. The midnight is marked by blue triangles. MIGHTI data gaps are due to SAA (South Atlantic Anomaly) or day-night transitions (see Englert et al., 2023). The IMF Bz southward turning occurred after 12 UT, which is highlighted by a dashed oval. The nightside zonal wind start to see reaction in the next orbit. Not much change is seen on the dayside. The ExB meridional ion drifts (vertical upward at the magnetic equator) for each orbit are plotted on the right.

JGR Space Physics: Using a numerical model where the coupled physical processes of the magnetosphere, ionosphere, and thermosphere are represented, we simulated the nighttime ionospheric disturbances caused by electric fields that enter this system from the magnetosphere and electric fields generated internally by changes in the thermospheric winds. The former is quick to reach the low latitudes, and the latter is delayed by the slower response of the neutral winds. The coupled model and NASA satellite observation showed good agreement. The results show good capability and lend themselves to the future effort to forecasting space weather at low latitudes.

SubAuroral Red Arcs Generated by Inner Magnetospheric Heat Flux and by SubAuroral Polarization Streams

whawkins — Fri, 06 Sep 2024 19:51:29 +0000

SubAuroral Red Arcs Generated by Inner Magnetospheric Heat Flux and by SubAuroral Polarization Streams whawkins Fri, 09/06/2024 - 13:51

Author:

whawkins

Sep 6, 2024

Heat flux/SAPS impacts on SAR arcs. (a-c) 6300 A column emission rates in the baseline TIEGCM run, CIMI heat flux driven TIEGCM run, and their difference in the northern hemisphere. (d-f) Same format for the southern hemisphere. (g-l) Same format for the comparison between with and without SAPS.

Geophysical Research Letters: The Earth's topside atmosphere is subject to energy inputs from the magnetosphere and solar wind. In addition to the Joule heating generated by high latitude plasma convection and energy flux carried by precipitating magnetospheric particles, magnetospheric energy can be also deposited in the ionosphere-thermosphere via heat flux, i.e., energy flows carried by low-energy thermal electrons. When hot ions in the ring current collide with the cold plasma in the plasmasphere, heat conduction occurs and the resultant heat flux is transported along geomagnetic field lines to the footprint ionosphere. The additional heating raises the electron temperature in the subauroral ionosphere and modifies the ionosphere-thermosphere states. This study uses first-principles inner magnetosphere model and ionosphere-thermosphere model to illustrate the thermodynamic coupling effects between the topside ionosphere and the magnetosphere, and compare the relative significance between the heat flux and plasma convection due to electrodynamic coupling. The numerical experiments show that the heat flux primarily increases electron temperature while subauroral plasma flow heats up both plasma and neutrals. Despite different physical mechanisms, the heat flux and subauroral plasma convection make comparable contributions to red line emission rates in the subauroral region.

The contribution of plasma sheet bubbles to stormtime ring current buildup and evolution of the energy composition

whawkins — Thu, 18 May 2023 16:28:08 +0000

The contribution of plasma sheet bubbles to stormtime ring current buildup and evolution of the energy composition whawkins Thu, 05/18/2023 - 10:28

Author:

whawkins

May 18, 2023

JGR Space Physics: The formation of the ring current is one of the defining features of the near-Earth space response to solar storms. While it is known that the ring current originates from Earth’s magnetic tail, the relative roles of different transport mechanisms remains unclear. In this study, we utilize numerical modeling to investigate ring current buildup for a specific solar storm, and find that flows that are medium scale relative to the system size and referred to as plasma “bubbles”, are responsible for at least half of the total buildup of ring current plasma. Our analysis also shows that the bubbles displace some of the background plasma on their way Earthward, which is important when calculating their net contribution to the ring current. The modeled ring current energy spectrum is in good agreement with spacecraft observations, and the evolution of the energy spectrum is driven by both an evolving plasma population in the tail and by energy-dependent charge exchange. The ability to accurately model the complex interactions between the ring current and Earth’s geospace system is critical for understanding the full impacts of solar storms.

Comparison of proton intensities between (a) RBSPICE and (b) RCM for the full energy spectra between 10 and 200 keV. (c) Comparison between the Observed Sym-H (blue), that calculated from the simulation (orange), and the DPS-Dst evaluated in the model within 6 RE (green), the same as in Figure 1. (d) RCM pressure and RBSP-B's full trajectory (orange line) and current position (white circle with orange border) mapped along field lines to the equatorial plane. The vertical lines in panels (a), (b), and (c), and pressure and spacecraft location in panel (d), all correspond to the time indicated in panel (d). The thin colored bar below panel (b) shows the RCM pressure at the spacecraft location for a given time, with the same colorbar as panel (d).

Thermospheric Density Perturbations Produced by Traveling Atmospheric Disturbances during August 2005 Storm

whawkins — Fri, 16 Dec 2022 19:44:31 +0000

Thermospheric Density Perturbations Produced by Traveling Atmospheric Disturbances during August 2005 Storm whawkins Fri, 12/16/2022 - 12:44

Author:

whawkins

Dec 16, 2022

During geomagnetic storms, increased activity within the geospace environment causes large scale plasma convection to occur and electrons to precipitate into the upper atmosphere. The enhanced heating of the thermosphere by the plasma convection and electron precipitation can produce large perturbations in the neutral density. These neutral density perturbations propagate away from their point of origin, oftentimes traveling to the equator and into the other hemisphere. Here, simulation results using a high resolution coupled geospace model that includes a magnetosphere, inner magnetosphere, ionosphere, and thermosphere model show that neutral density perturbations generated in one hemisphere can propagate far enough to interact with those in the other hemisphere. The intersection of two or more perturbations produce regions of larger neutral density perturbations. The high resolution coupled geospace model performs significantly better than the standalone model when compared to observations of neutral density by low altitude spacecraft. A significant fraction of the observed neutral density perturbations is captured by the coupled model, especially those at low latitudes. Proper simulation and understanding of storm-time neutral density perturbations is imperative to space weather prediction as neutral density perturbations can greatly affect satellite drag.

Snapshots that follow the neutral density perturbation observed by CHAMP (star) and GRACE (circle) at low latitude at 13:20 UT. The approximate location of the wavefront for TADs that intersect near CHAMP’s position at 13:20 UT are indicated by a line white line for the northern hemisphere and black line for the southern hemisphere.

Thermospheric Neutral Density Variation during the "SpaceX" Storm: Implications from Physics-based Whole Geospace Modeling

whawkins — Wed, 23 Nov 2022 18:32:53 +0000

Thermospheric Neutral Density Variation during the "SpaceX" Storm: Implications from Physics-based Whole Geospace Modeling whawkins Wed, 11/23/2022 - 11:32

Author:

whawkins

Nov 23, 2022

Space Weather—Dong Lin, Wenbin Wang, Katherine Garcia-Sage, Jia Yue, Viacheslav Merkin, Joseph McInerney, Kevin Pham, Kareem Sorathia

Neutral density variations along the Starlink orbit calculated by (a) MAGE, (b) TIEGCM, (c) DTM-2012, and (d) NRLMSIS 2.0. (e) Relative variations of neutral density based on the values on February 1 at the same UT and location. (f) Starlink altitude. (g) The Ap index used to drive NRLMSIS 2.0.

On February 3, 2022, 40 Starlink satellites were launched by the SpaceX Corporation when a moderate geomagnetic storm occurred, followed by another storm on February 4. The storm activities have been regarded as the culprit for the loss of the Starlink satellites afterwards. Although strong geomagnetic storms are well-known to be able to increase the neutral atmospheric mass density so as to satellite drag in the thermosphere where many space vehicles are orbiting around the Earth, a not-so-strong storm was not expected to bring such huge impacts based on engineering design evaluation using empirical atmospheric density models. This study compares the performance of a state-of-the-art physics-based, fully coupled whole geospace model and empirical models in predicting the neutral mass density variation in the thermosphere. It turns out that the physics-based model is more accurate in capturing the magnitude of storm enhancement of neutral density. It also resolves the gradual recovery process even though it is not reflected in some geomagnetic indices that are used to drive the empirical models. Using such first-principles whole geospace model is suggested as a necessary step in future space weather applications.

Thermospheric Impact on the Magnetosphere through Ionospheric Outflow

whawkins — Wed, 12 Oct 2022 20:32:56 +0000

Thermospheric Impact on the Magnetosphere through Ionospheric Outflow whawkins Wed, 10/12/2022 - 14:32

Author:

whawkins

Oct 12, 2022

Latest coupled model of thermosphere-ionosphere-magnetosphere system that includes realistic and causal ion outflow.

Kevin Pham, William Lotko, Roger Varney, Binzheng Zhang, Jing Liu have taken a key step in evaluating the importance of ionospheric outflows relative to electrodynamic coupling in the thermosphere’s impact on geospace dynamics. We isolated the thermosphere’s material influence and suppressed electrodynamic feedback in whole geospace simulations by imposing a time-constant ionospheric conductance in the ionospheric Ohm’s law in a coupled model that combines the multi-fluid Lyon-Fedder-Mobarry magnetosphere model with the Thermosphere Ionosphere Electrodynamic General Circulation Model and the Ionosphere Polar Wind Model that includes both polar wind and transversely accelerated ion species. Numerical experiments were conducted for different thermospheric states parameterized by F10.7 for interplanetary driving representative of the stream interaction region that swept past Earth on 27 March 2003. We demonstrate that thermosphere through its regulation of ionospheric outflows influences magnetosphere-ionosphere (MI) convection and the ion composition, symmetries, x-line perimeter and magnetic merging of the magnetosphere. Feedback to the ionosphere-thermosphere from evolving MI convection, and Alfvénic Poynting fluxes and soft (~ few 100 eV) electron precipitation originating in the magnetosphere, in turn, modify the evolving O+ outflow properties. The simulation results identify a variety of observed magnetospheric features that are attributable directly to the thermosphere’s material influence: Asymmetries in O+ outflow fluxes and velocities in the pre/postnoon low-altitude magnetosphere, dawn/duskside lobes and pre/postmidnight plasmasheet; O+ distribution of the plasmasheet; magnetic x-line location and reconnection rate along it. O+ outflows during solar maximum conditions (high F10.7) tend to counteract the plasmasheet’s pre/postmidnight asymmetries caused by the night-to-day gradient in ionospheric Hall conductance.

Geospace response to an extreme solar flare

kolinski — Mon, 15 Nov 2021 21:58:00 +0000

Geospace response to an extreme solar flare kolinski Mon, 11/15/2021 - 14:58

Publication Name: AGU Advances; HAO Author: Jing Liu; Authors names as listed: Jing Liu, Wenbin Wang, Liying Qian, William Lotko, Alan G. Burns, Kevin Pham, Gang Lu, Stanley C. Solomon, et al.

Author:

kolinski

Nov 15, 2021

Solar flares—a sudden eruption of electromagnetic radiation at the Sun—are known to have significant impacts on Earth’s upper atmosphere and ionosphere, but their collective effects on geospace as an integrated system have never been examined. We use a newly developed whole geospace model, combined with key observational data, to study the effects of the 6 September 2017 X9.3 flare on the geospace system.

Solar flare effects on magnetospheric convection and ionospheric potential. Comparison of 50-minute averages (12:02-12:51 UT) from LTR simulations of magnetospheric and ionospheric states on September 6, 2017 with and without solar flare effects. Bottom row: LTR-simulated magnetospheric convection velocity in equatorial plane (ZGSM = 0) with (A) and without (B) solar flare effects and their difference (C). Arrows indicate direction and magnitude (also in color) of the convection velocity projected onto the plane. Top row: High-latitude electric potential, essentially convection streamlines in the ionosphere with (D) and without (E) solar flare effects and their difference (F). The minimum and maximum potentials are labeled below panels (D-F).

The analysis shows that the solar wind-magnetosphere interaction, magnetotail, field-aligned current distribution, auroral precipitation and high-latitude ionospheric convection respond to atmospheric absorption of solar flare radiation. This study, for the first time, demonstrates that a rapid and large increase in the iono-spheric E-region photoionization due to a solar transient event globally modifies the electrodynamic cou-pling of the geospace system.

Kevin Pham

Efficiency of Electromagnetic Energy Transfer from Solar Wind to Ionosphere through Magnetospheric Ultra-Low Frequency Waves

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Penetrating electric field with/without disturbed electric fields During the 7-8 July 2022 geomagnetic storm simulated by MAGE and observed by ICON MIGHTI

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SubAuroral Red Arcs Generated by Inner Magnetospheric Heat Flux and by SubAuroral Polarization Streams

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The contribution of plasma sheet bubbles to stormtime ring current buildup and evolution of the energy composition

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Thermospheric Density Perturbations Produced by Traveling Atmospheric Disturbances during August 2005 Storm

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Thermospheric Neutral Density Variation during the "SpaceX" Storm: Implications from Physics-based Whole Geospace Modeling

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Thermospheric Impact on the Magnetosphere through Ionospheric Outflow

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Geospace response to an extreme solar flare

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