Isaac Sutka
Research Mentor: Mojtaba Akhavan-Tafti
Mentor Department: Climate and Space Sciences and Engineering, Engineering
Author(s): Mojtaba Akhavan-Tafti , Dominic Payne
Session: Session 7 (4:00 PM – 4:50 PM)
Presentation Type: Oral Presentation
Abstract
The solar wind is a continuous stream of charged particles flowing outward from the Sun. Structures within the solar wind, across many scales, can influence space weather by disrupting satellite operations and GPS navigation, and by contributing to geomagnetic storms that disturb Earth’s magnetosphere. Therefore, it is important to understand the occurrence of different solar wind structures across a range of sizes. We investigate how the occurrence rate of solar wind structures varies with scale size at 1 Astronomical Unit (AU). We analyze NASA’s WIND satellite data to study Alfvénic deflections in the solar wind using measurements collected at approximately one AU from the Sun. To quantify prominent fluctuations, we calculate background-normalized fluctuation amplitudes using a range of short- and long-duration averages corresponding to different structural sizes, spanning approximately 4 to 1000 Earth radii. We then identify only the normalized fluctuations above a given percent threshold and count their number within each timescale band. This method enables us to identify significant fluctuations and assess their frequency and distribution across multiple spatial scales in the solar wind. We examined thresholds ranging from 10% to 40% to determine how many structures pass through each threshold. We measured fluctuations in the Bx, By, and Bz components of the solar wind magnetic field and applied the same methodology to compare the distribution of density and velocity fluctuations across scale sizes. For all variables, the number of detected structures was largest at scale sizes of 4-100 Earth radii, but near 2 orders of magnitude smaller for scale sizes closer to 500 Earth radii. At larger scales, Bx fluctuations dominate over By and Bz fluctuations, indicating that larger-scale fluctuations tend to align along the X axis, whereas smaller scales show greater isotropy, indicating that fluctuations are more evenly distributed across all magnetic field components. The magnetic and density structures occurred at comparable rates for scale sizes of 4-100 Earth radii, but both dropped off by 1-3 orders of magnitude for scale sizes closer to 500 Earth radii. With a threshold of 5%, we find that dBx structures decrease uniformly with increasing scale size, while dVx structures maintain comparable counts on the order of 10-100 for sizes of 400-800 Earth radii. Overall, these findings provide insight into the types of solar wind structures that exist at 1 AU, which contributes to the study of space weather and provides physical insight into the types of solar wind structures that can affect the near-Earth environment. Future work will analyze the average structure size and standard deviation and apply machine learning techniques to automatically detect and classify solar wind structures across different scales.
