By Andrey Samsonov (University College London)
The magnetopause standoff distance characterizes global magnetospheric compression and deformation in response to changes in the solar wind dynamic pressure and interplanetary magnetic field. We cannot derive this parameter directly from in situ spacecraft measurements because spacecraft cross the magnetopause rarely and in different regions along the magnetopause surface. However, it will be possible to obtain the time series of the magnetopause standoff distance in the near future using observations by soft X-ray imagers. In two companion papers (see below), we describe methods of finding the standoff distance from X-ray images. Soft X-rays are emitted in the magnetosheath and cusps as a result of charge exchange between heavy solar wind ions and exospheric neutrals. We use the results of MHD simulations to calculate the X-ray emissivity for different solar wind conditions. We simulate an artificial case with constant solar wind conditions and a case with an interplanetary coronal mass ejection (ICME) observed by the Wind spacecraft on 16-17 June 2012. Some MHD models predict relatively high density in the magnetosphere, larger than observed in the data. Correcting this, we develop magnetospheric masking methods to separate the magnetosphere from the magnetosheath and cusps.
We use the SXI_SIM numerical code developed at the University of Leicester to simulate the expected output of the Soft X-ray Imager (SXI) on board the forthcoming Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission. Using the MHD results as input conditions, this code calculates the integrated emissivity along the Line-of-Sight (Ix) and SXI counts maps (see Figure 1). We verify the assumption that the maximum of the integrated emissivity is tangent to the magnetopause. Overall, the magnetopause is located close to the maximum Ix gradient or between the maximum Ix gradient and the maximum Ix depending on the method used. But since the angular distance between the maximum Ix gradient and the maximum Ix is relatively small (about 3°), the maximum Ix might be used as an indicator of the outer boundary of a wide magnetopause layer usually obtained in MHD simulations.
Original articles for further detail:
Samsonov, A., Carter, J. A., Read, A., Sembay, S., Branduardi-Raymont, G., Sibeck, D., & Escoubet, P. (2022). Finding magnetopause standoff distance using a soft X-ray imager: 1. Magnetospheric masking. Journal of Geophysical Research: Space Physics,
127, e2022JA030848. https://doi.org/10.1029/2022JA030848
Samsonov, A., Sembay, S., Read, A., Carter, J. A., Branduardi-Raymont, G., Sibeck, D., & Escoubet, P. (2022). Finding magnetopause standoff distance using a Soft X-ray Imager: 2. Methods to analyze 2-D X-ray images. Journal of Geophysical Research: Space Physics, 127, e2022JA030850. https://doi.org/10.1029/2022JA030850
Spring MIST will be held at the University of Birmingham from 3rd to 5th April 2023.
With eight sessions dedicated to MIST science this is an excellent opportunity to see the truly excellent and world-class research being done across the UK. Included in the registration we will also have a Poster Session and Drinks Reception, a Conference Banquet held at the beautiful Birmingham Botanical Gardens and, after a Covid-induced break, the Spring MIST Football Tournament will also be back.
There are two registration options: with or without B&B accommodation. All tickets include:
The accommodation option includes B&B at the venue (Edgbaston Park Hotel, University of Birmingham) on the Monday and Tuesday night.
The price is £350 for registration with accommodation and £200 for just registration (no accommodation).
Abstract submissions closes on January 30th and Registration closes on February 20th (please register as early as possible to help with the logistic planning!).
All the details, links to submit abstracts and register are available here: https://spaceweather.bham.ac.uk/conference/spring-mist-2023/
We look forward to seeing you at Spring MIST 2023!