Dong Lin

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.

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.

HIWIND Balloon and Antarctica Jang Bogo FPI High Latitude Conjugate Thermospheric Wind Observations and Simulations

whawkins — Fri, 21 Jun 2024 18:59:58 +0000

HIWIND Balloon and Antarctica Jang Bogo FPI High Latitude Conjugate Thermospheric Wind Observations and Simulations whawkins Fri, 06/21/2024 - 12:59

Author:

whawkins

Jun 21, 2024

JGR Space Physics: Using balloon instrument in the northern hemisphere and ground based instrument in the southern hemisphere, we study the conjugacy of the thermospheric winds of high latitudes. We found that the more summer hemispheric heating alters the thermospheric winds and resulted in a double-hump feature on the dayside meridional winds. We also used model with cusp heating to simulate the winds and were able to reproduce the double-hump feature.

Thermospheric wind observations from HIWIND (northern summer) and JBS (southern winter) along with the TIEGCM simulations at the respective locations. The JBS data were shifted by 7 hours so that the local time of the JBS is approximately equal to that of HIWIND. The meridional winds from JBS were reversed so that the poleward meridional winds from JBS is positive for easy comparison with HIWIND data. The prominent double hump feature in northern hemisphere meridional winds (HIWIND, upper penal) is a result of the high energy input in the summer hemisphere.
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MAGE Model Simulation of the Pre-reversal Enhancement and Comparison with ICON and Jicamarca ISR Observations

whawkins — Fri, 21 Jun 2024 18:52:03 +0000

MAGE Model Simulation of the Pre-reversal Enhancement and Comparison with ICON and Jicamarca ISR Observations whawkins Fri, 06/21/2024 - 12:52

Author:

whawkins

Jun 21, 2024

JGR Space Physics: Using the latest coupled geospace model MAGE (Multiscale Atmosphere-Geospace Environment) and observations from Jicamarca ISR and ICON IVM instrument, we examine the pre-reversal enhancement during geomagnetic quiet time period. The MAGE shows comparable PRE to both the Jicamarca ISR and ICON observations. There appears to be a discrepancy between the Jicamarca ISR and ICON IVM with the later showed PRE about two times larger (~ 40 m/s). This is the first time that MAGE is used to simulate the PRE. The results show that the MAGE can simulate the PRE well and are mostly consistent with observations.

MAGE simulations of the equatorial vertical ion drifts (black vectors along the magnetic equator) at 23:49 UT. The MAGE simulated ExB meridional ion drift (IVM definition) sampled along the ICON satellite track (black line above the satellite track shown as the dashed line) and the IVM observed ExB meridional drift (lime or magenta vector) from 23:15 to 23:55 UT. The magenta vectors are values near 2349 UT. The PRE is visible in the simulated equatorial vertical ion drift and in both the MAGE simulated and ICON observed ExB meridional ion drifts along the satellite tracks . The background shows the nmf2 from the MAGE simulation.

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.

Dong Lin

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

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

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