Model Info

How MSWIM2D turns near-Earth observations into a global picture of the solar wind across the ecliptic plane, from the physics to the grid.

How it works

01 · Observe

The inner boundary at 1 AU is set by four data streams: OMNI (near-Earth solar wind), MIDL (merged multi-satellite L1 data), STEREO (off-Sun-Earth-line), and Solar Orbiter (ballistically propagated to 1 AU). Together they reconstruct the full 360° of the ecliptic. The operational record is stitched at a seam in July 2004: years before the seam come from the original OMNI-driven run, and July 2004 onward from the current MIDL-driven run.

02 · Simulate

The BATSRUS MHD solver (part of the SWMF) runs the Outer Heliosphere domain on a 2D spherical grid covering all longitudes and r = 1–75 AU. Shocks, CIRs, and CMEs propagate self-consistently outward through the domain.

03 · Interpolate

Users supply a spacecraft trajectory in HGI coordinates, or pick a built-in target. The model output is interpolated to 1-hour resolution along the path, yielding ρ, U, B, and Ti.

Data products

The production run is one continuous simulation with an unbroken clock. We publish it in three tiers by how well-constrained the inner boundary was at each point in time. Together they tile a single timeline with no gaps and no overlaps; the two seams march forward as new spacecraft data arrives, so months are steadily promoted to a more confident tier over time.

Final

Fully data-constrained reanalysis. Every assimilated source (L1 (OMNI/MIDL), STEREO-A, and Solar Orbiter as available) reports through this window, so the 1 AU boundary is as well-determined as the observations allow. The validated product; use without caveat.

Preliminary

Provisional. Past the point where all sources report, the boundary is built from a thinner set: L1 + Solar Orbiter, then L1 alone once STEREO-A's plasma ends. These months are revised and promoted to Final as the missing data backfills, so treat the values as subject to change.

Prediction

Forecast, not observation. Beyond the last available data the model keeps running on a persistence boundary: the last solar rotation of L1 looped forward. Skillful far from the Sun for months, but stale near Earth almost immediately. See the Prediction tab for the skill horizon (~4 days per AU).

The Solver

MSWIM2D uses the BATSRUS MHD solver from the Space Weather Modeling Framework (SWMF). The Outer Heliosphere component is configured for a 2D spherical grid in the ecliptic plane, solving the ideal MHD equations with time-dependent boundary conditions driven by real observations.

Unlike 1D models that propagate along a single radial line, the 2D grid captures the full longitudinal structure of the solar wind: stream interactions, shock geometry, and the spiral magnetic field all evolve self-consistently across the plane.

SWMF software →

Limitations

  1. Ecliptic plane only: the 2D grid covers the ecliptic. Out-of-plane components are approximate and the model does not resolve high-latitude structure.
  2. No pickup ions: the single-fluid MHD formulation does not include pickup ion effects, which become dynamically important beyond ~10 AU near the heliopause.
  3. Input coverage gaps: periods with poor upstream monitoring or missing STEREO data may reduce boundary accuracy, which propagates into the simulation domain.