Solar wind control of the terrestrial magnetotail as seen by STEREO

Abstract

At the beginning of 2007 the twin STEREO spacecraft provided a unique opportunity to study the global solar wind control of the terrestrial magnetotail under typical solar activity minimum conditions. The STEREO-B (STB) spacecraft flew in the vicinity of the far terrestrial magnetotail, while the STEREO-A (STA) spacecraft was located in front of the Earth performing measurements in the undisturbed solar wind. In February, the STB spacecraft was located in the magnetosheath most of the time but experienced several incursions into the distant magnetotail. Comparison of STA and STB observations determines unambiguously whether solar wind events such as energetic particle enhancements observed by STB are of pure solar origin or due to the influence of the terrestrial magnetosphere. During this time period in 2007, there were solar minimum conditions with alternating fast and slow solar wind streams that formed corotating interaction regions, which were the dominating source of magnetospheric disturbances encountering the Earth almost every week. Under these conditions, STB experienced multiple bow shock and magnetopause crossings due to the induced highly dynamic behavior of the terrestrial magnetotail and detected bursts of tailward directed energetic ions in the range of 110-2200 keV accompanied by suprathermal electrons of~700-1500 eV, which were not seen in the undisturbed solar wind by STA. The corotating interaction regions triggered these energetic particle enhancements, and we demonstrate their magnetosphere-related origin. Even after leaving the magnetosheath in March 2007, STB continued to observe antisunward directed energetic ion bursts until May up to a distance of~800 R E behind Earth, the largest distance to which solar wind and magnetospheric interaction has been observed. These results show that Earth is a very significant source of energetic particles in its local interplanetary environment.

Unusual Location of the Geotail Magnetopause Near Lunar Orbit: A Case Study

“…In addition, the case mentioned by Shodhan et al (1996) also showed that the windsock caused variations on a timescale of hours, and breathing dominates on a timescale of tens of minutes. The flapping motions caused by solar wind direction changes and shock/corotating interaction regions (Opitz et al, 2014) in the deeper tail (at X=∼-230 R E ) were confirmed by Grygorov et al (2014). Due to small fluctuations of the solar wind velocity direction, Grygorov et al (2014) found that the Wind satellite entered the south lobe and then scanned the whole magnetotail in Z direction before the shock arrival.…”

Looking for Evidence of Wind‐Shear Disconnections of the Earth's Magnetotail: GEOTAIL Measurements and LFM MHD Simulations

“…ISEE-3 made six orbits into the distant magnetotail (Bame et al, 1983(Bame et al, ) in 1982(Bame et al, -1983; the mission was hampered by the absence of ion measurements; however, plasma flow velocities were obtained from electron measurements. In February of 2007 the STEREO-B spacecraft made several encounters with the distant magnetotail (Opitz et al, 2014;Sauvaud et al, 2011), although plasma flow vectors in the magnetotail may not be available.…”

Characterisation of suprathermal electron pitch-angle distributions

“…In spite of the small angular separation between STEREO-A and STEREO-B (less than 11 • ) during March-May 2007, significant discrepancies were observed in both isotropy and BDE. Some contribution of electrons escaping from the Earth's magnetosphere at STEREO-B (Opitz et al 2014) or a shielding effect of the magnetospheric obstacle cannot be discarded as a possible source of this discrepancy at the earliest part of the plots.…”