Short large-amplitude magnetic structures (SLAMS) at Mercury observed by MESSENGER

IF 1.7 4区地球科学 Q3 ASTRONOMY & ASTROPHYSICS

Annales Geophysicae Pub Date : 2024-04-25 DOI:10.5194/angeo-42-117-2024

T. Karlsson, F. Plaschke, A. Glass, J. Raines

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Abstract

Abstract. We present the first observations of short large-amplitude magnetic structures (denoted SLAMS) at Mercury. We have investigated approximately 4 years of MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) data to identify SLAMS in the Mercury foreshock. Defining SLAMS as magnetic field compressional structures, with an increase in magnetic field strength of at least twice the background magnetic field strength, when MESSENGER is located in the solar wind, we find 435 SLAMS. The SLAMS are found either in regions of a general ultra-low frequency (ULF) wave field, at the boundary of such a ULF wave field, or in a few cases isolated from the wave field. We present statistics on several properties of the SLAMS, such as temporal scale size, amplitude, and the presence of whistler-like wave emissions. We find that SLAMS are mostly found during periods of low interplanetary magnetic field strength, indicating that they are more common for higher solar wind Alfvénic Mach number (MA). We use the Tao solar wind model to estimate solar wind parameters to verify that MA is indeed larger during SLAMS observations than otherwise. Finally, we also investigate how SLAMS observations are related to foreshock geometry.

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MESSENGER 在水星观测到的短大振幅磁结构 (SLAMS)

摘要。我们首次观测到水星的短大振幅磁结构（SLAMS）。我们调查了大约4年的MESSENGER（水星表面、空间环境、地球化学和测距）数据，以确定水星前震中的SLAMS。将SLAMS定义为磁场压缩结构，当MESSENGER位于太阳风中时，磁场强度增加至少为背景磁场强度的两倍，我们发现了435个SLAMS。这些 SLAMS 要么出现在一般超低频（ULF）波场的区域，要么出现在这种超低频波场的边界，要么出现在与波场隔离的少数情况下。我们对 SLAMS 的几个特性进行了统计，如时间尺度大小、振幅以及是否存在类似于哨兵的波发射。我们发现，SLAMS 大多出现在行星际磁场强度较低的时期，这表明它们在太阳风阿尔费尼科马赫数（MA）较高时更为常见。我们利用陶太阳风模型来估算太阳风参数，以验证SLAMS观测期间的太阳风马赫数确实比其他时候要大。最后，我们还研究了SLAMS观测与前震几何的关系。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Annales Geophysicae 地学-地球科学综合

CiteScore

4.30

自引率

0.00%

发文量

审稿时长

2 months

期刊介绍： Annales Geophysicae (ANGEO) is a not-for-profit international multi- and inter-disciplinary scientific open-access journal in the field of solar–terrestrial and planetary sciences. ANGEO publishes original articles and short communications (letters) on research of the Sun–Earth system, including the science of space weather, solar–terrestrial plasma physics, the Earth''s ionosphere and atmosphere, the magnetosphere, and the study of planets and planetary systems, the interaction between the different spheres of a planet, and the interaction across the planetary system. Topics range from space weathering, planetary magnetic field, and planetary interior and surface dynamics to the formation and evolution of planetary systems.