Slip-Squashing Factors

March 31, 2026 · View on GitHub

Slip-squashing factors QsfQ_\mathrm{sf} and QsbQ_\mathrm{sb} (Titov_2009_ApJ_693_1029) are defined by two field line mappings and two boundary flow mappings between two instants; their large values define the surfaces that border of the reconnected or to-be-reconnected magnetic flux tubes for a given period of time during the magnetic evolution.

For the case of static boundaries (u⃗(t)=0⃗\vec{u}(t) = \vec{0} at the bottom boundary), we can compute the slip-squashing factors using the coordinate mapping provided by FastQSL. Following the initial coordinate mapping within the first magnetic field, the resulting mapped coordinates can be served as a seed grid for applying FastQSL to the second magnetic field.

This program can be downloaded with the command

git clone https://github.com/el2718/slipq

And FastQSL2 should be downloaded first

git clone https://github.com/el2718/FastQSL2

Please address comments and suggestions to Dr. Chen, Jun (陈俊)

CC BY-NC-SA 4.0

This program is licensed under a CC BY-NC-SA 4.0 License.

Cite as

  • Jun Chen*, Thomas Wiegelmann, Li Feng*, Chaowei Jiang, and Rui Liu. FastQSL 2: A Comprehensive Toolkit for Magnetic Connectivity Analysis. 2026, SCIENCE CHINA Physics, Mechanics & Astronomy, submitted

Parameters

  • bx0, by0, bz0: the three components of magnetic field at t0t_0

  • bx1, by1, bz1: the three components of magnetic field at t1t_1

  • xa, ya, za, spherical, xreg, yreg, factor, lon_delta, lat_delta, preview, fname are the same as those in FastQSL2

Products

Both slipq.pro and slipq.py are functions, their return is a slip-squashing factor. If t0<t1t_0 < t_1, QsfQ_\mathrm{sf} is returned; If t1<t0t_1 < t_0, QsbQ_\mathrm{sb} is returned.

qsl0 is the product of FastQSL 2 at for the field bx0, by0, bz0 at t0t_0. If use slipq.pro, it is return by the keyword qsl0. If use slipq.py, t0<t1t_0 < t_1, the results are returned by the tuple (qsf, qsl0), see the example of demo_Btitov2009.py

Demos

If use fastqsl.pro

IDL> .r demo_Btitov2009.pro

If use fastqsl.py

python3 demo_Btitov2009.py

History

  • Feb 26, 2026 Jun Chen, version 1.0