Determining L‐M‐N Current Sheet Coordinates at the Magnetopause From Magnetospheric Multiscale Data. Issue 3 (23rd March 2018)

• Record Type: Journal Article
• Authors: Denton, R. E.; Sonnerup, B. U. Ö.; Russell, C. T.; Hasegawa, H.; Phan, T.‐D.; Strangeway, R. J.; Giles, B. L.; Ergun, R. E; Lindqvist, P.‐A.; Torbert, R. B.; Burch, J. L; Vines, S. K.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 3(2018)
• Page Start: 2274
• Page End: 2295
• Publication Date: 2018-03-23
• Subjects: magnetic reconnection -- LMN coordinate system -- magnetopause -- magnetospheric multiscale mission -- MMS -- multispacecraft methods; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2017JA024619
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: We discuss methods to determine L ‐ M ‐ N coordinate systems for current sheet crossings observed by the Magnetospheric Multiscale (MMS) spacecraft mission during ongoing reconnection, wheree L is the direction of the reconnecting component of the magnetic field, B, ande N is normal to the magnetopause. We present and test a new hybrid method, withe L estimated as the maximum variance direction ofB (MVAB) ande N as the direction of maximum directional derivative ofB, and then adjust these directions to be perpendicular. In the best case, only small adjustment is needed. Results from this method, applied to an MMS crossing of the dayside magnetopause at 1305:45 UT on 16 October 2015, are discussed and compared with those from other methods for whiche N is obtained by other means. Each of the other evaluations can be combined withe L from MVAB in a generalized hybrid approach to provide an L ‐ M ‐ N system. The quality of the results is judged by eigenvalue ratios, constancy of directions using different data segments and methods, and expected sign and magnitude of the normal component ofB . For this event, the hybrid method appears to producee N accurate to within less than 10°. We discuss variance analysis using the electric current density, J, or theJ ×B force, which yield promising results, and minimum Faraday residue analysis and MVAB alone, which can be useful for other events. We also briefly discuss results from our hybrid method and MVAB alone for a few other MMS reconnection events. Plain Language Summary: We discuss methods for determining coordinate systems in order to study magnetic reconnection events at the magnetopause, the boundary between the ionized gas in the region of space dominated by the Earth's magnetic field and the ionized gas coming from the solar wind. We introduce a new method that combines results from multiple methods in order to determine the three coordinate directions in space. We demonstrate this method by applying it to an event observed by the Magnetospheric Multiscale spacecraft on 16 October 2015 and at other times. Key Points: Methods to determine L ‐ M ‐ N current sheet coordinates are described and tested Quality of results is judged by eigenvalue ratios and consistency using different data intervals and methods and with the geophysical context For the interval examined here, the uncertainty of the normal direction was at least several degrees but probably less than 10°