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Surface Renewal: An Advanced Micrometeorological Method for Measuring and Processing Field-Scale Energy Flux Density Data
Published on: December 12, 2013
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Magnetosheath Jets Over Solar Cycle 24: An Empirical Model
Laura Vuorinen1, Adrian T LaMoury2, Heli Hietala1,2,3
1Department of Physics and Astronomy University of Turku Turku Finland.
Journal of Geophysical Research. Space Physics
|March 5, 2024
Summary
Magnetosheath jets, flows of enhanced pressure, were studied over a solar cycle using THEMIS data. Occurrence rates are not strongly dependent on solar cycle variations, despite initial sampling biases.
Area of Science:
- Space Physics
- Solar-Terrestrial Physics
- Magnetospheric Dynamics
Background:
- The Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission has provided extensive data from the subsolar magnetosheath.
- Understanding phenomena dependent on solar wind conditions requires consistent solar wind sampling.
- Magnetosheath jets, characterized by enhanced earthward dynamic pressure, are influenced by solar wind parameters.
Purpose of the Study:
- To investigate the occurrence rates of magnetosheath jets over a full solar cycle (24).
- To address biases in THEMIS data due to spacecraft orbits and uneven solar wind sampling.
- To develop a model for jet occurrence based on solar wind conditions and estimate unbiased yearly rates.
Main Methods:
- Analysis of THEMIS spacecraft observations in the subsolar magnetosheath from 2008-2019.
- Correlation of jet occurrence with solar wind conditions, particularly interplanetary magnetic field orientation.
- Development of a predictive model for jet occurrence based on solar wind parameters.
- Utilizing OMNI data to calculate unbiased yearly jet occurrence rates for solar cycles 24 and 23.
Main Results:
- Yearly occurrence rates of magnetosheath jets recorded by THEMIS were found to be biased.
- A model was developed to predict jet occurrence based on solar wind conditions.
- Unbiased analysis suggests no strong solar cycle dependency in magnetosheath jet formation.
- Jets are predominantly observed downstream of the quasi-parallel bow shock.
Conclusions:
- Initial THEMIS observations of magnetosheath jet occurrence were biased by sampling inconsistencies.
- Magnetosheath jet formation does not exhibit a strong dependence on solar cycle phase.
- Solar wind conditions, especially IMF orientation, are critical drivers for jet occurrence.
- Further research can refine the understanding of jet dynamics and their impact on the magnetosphere.
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