juliensimon/substorm-onsets

Substorm Onset Events (SuperMAG)

Credit: NASA

Part of the Space Weather Datasets collection on Hugging Face.

A consolidated catalog of 253,319 magnetospheric substorm onset events spanning 1975--2024, combining five independent detection algorithms from the SuperMAG collaboration. This is the most comprehensive substorm event list available, enabling multi-algorithm comparison and consensus studies.

Dataset description

Magnetospheric substorms are fundamental space weather events driven by the solar wind's interaction with Earth's magnetic field. During a substorm, magnetic energy stored in the magnetotail is explosively released, accelerating charged particles that stream along field lines into the polar regions. This produces sudden auroral brightenings — the dramatic intensification of the Northern and Southern Lights — along with rapid changes in ground-level magnetic fields detected by magnetometer networks worldwide.

This dataset merges five complementary onset detection methods:

Source	Events	Detection method
forsyth	120,069	SML/SMU expansion-recovery (ground magnetometers)
newell	81,914	SML index (ground magnetometers)
ohtani	44,606	SML bay detection (ground magnetometers)
frey	4,191	IMAGE/FUV auroral imaging (space-based)
liou	2,539	Polar UVI auroral imaging (space-based)

Ground-based methods (246,589 events) detect substorms through characteristic negative bays in the SML (SuperMAG Lower) index — a measure of the westward auroral electrojet current. Space-based methods (6,730 events) directly observe the initial auroral brightening using ultraviolet imagers aboard the IMAGE and Polar satellites.

Each algorithm has different sensitivity and false-positive rates, so researchers often require onset confirmation across multiple lists. The source column enables filtering by algorithm or finding consensus events where multiple methods agree within a time window.

Schema

Column	Type	Description
datetime_utc	datetime	Substorm onset time (UTC)
mlt_hours	float64	Magnetic Local Time of onset (hours, 0-24)
magnetic_latitude_deg	float64	Magnetic latitude of onset (degrees)
geographic_longitude_deg	float64	Geographic longitude of onset (degrees)
geographic_latitude_deg	float64	Geographic latitude of onset (degrees)
source	string	Detection algorithm: newell, forsyth, ohtani, frey, liou
method	string	Detection method description

Quick stats

• 253,319 total substorm onset events
• 1975--2024 temporal coverage
• 5 independent detection algorithms
• 246,589 ground magnetometer detections, 6,730 auroral imaging detections

Usage

from datasets import load_dataset

ds = load_dataset("juliensimon/substorm-onsets", split="train")
df = ds.to_pandas()

# Events per algorithm
print(df["source"].value_counts())

# Annual substorm rate by algorithm
import matplotlib.pyplot as plt
df["year"] = df["datetime_utc"].dt.year
df.groupby(["year", "source"]).size().unstack().plot(figsize=(12, 5))
plt.ylabel("Substorm onsets per year")
plt.title("Annual Substorm Rate by Detection Algorithm")
plt.show()

# MLT distribution — substorms peak near midnight
df["mlt_hours"].hist(bins=48, alpha=0.7)
plt.xlabel("Magnetic Local Time (hours)")
plt.ylabel("Count")
plt.title("Substorm Onset MLT Distribution")
plt.show()

# Find consensus events (multiple algorithms within 10 minutes)
from datetime import timedelta
newell = df[df["source"] == "newell"]["datetime_utc"]
ohtani = df[df["source"] == "ohtani"]["datetime_utc"]

Data source

SuperMAG substorm onset lists, provided by the Johns Hopkins University Applied Physics Laboratory:

• Newell & Gjerloev (2011), doi:10.1029/2010JA016141
• Forsyth et al. (2015), doi:10.1002/2015JA021343
• Ohtani & Gjerloev (2020), doi:10.1029/2019JA027680
• Frey et al. (2004), doi:10.1029/2003JA010300
• Liou (2010), doi:10.1016/j.jastp.2009.08.005

Related datasets

• Dst Index — Hourly geomagnetic storm index
• Kp Index — 3-hourly geomagnetic activity
• AE Index — Auroral electrojet indices
• DONKI Space Weather — CMEs, flares, and geomagnetic storms

Pipeline

Source code: juliensimon/space-datasets

Support

If you find this dataset useful, please give it a ❤️ on the dataset page and share feedback in the Community tab! Also consider giving a ⭐ to the space-datasets repo.

Citation

@dataset{substorm_onsets,
  author = {Simon, Julien},
  title = {Substorm Onset Events (SuperMAG)},
  year = {2026},
  publisher = {Hugging Face},
  url = {https://huggingface.co/datasets/juliensimon/substorm-onsets},
  note = {Consolidated from SuperMAG: Newell, Forsyth, Ohtani, Frey, Liou lists}
}

License

CC-BY-4.0