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AsteriaStar
Live · NOAA SWPC

Solar wind

A continuous supersonic stream of plasma from the Sun's corona, carrying the Sun's magnetic field past Earth. Measured a million and a half kilometres upstream, which is the only reason there is any warning at all.

Measured now

  • Speed

    Live

    494km/s

    Moderate

    Typical solar wind speed. The magnetosphere is being pushed at an ordinary rate.

    Measured
    2026-09-17 05:10 UTC
    Type
    Observation
    Provider
    NOAA Space Weather Prediction Center

  • Proton density

    Live

    3.99cm^-3

    Measured
    2026-09-17 05:10 UTC
    Type
    Model product
    Provider
    NOAA Space Weather Prediction Center

    Observed at L1 and advected to Earth's bow shock nose by SWPC's propagation model.

  • Field strength (Bt)

    Live

    5nT

    Measured
    2026-09-17 05:10 UTC
    Type
    Observation
    Provider
    NOAA Space Weather Prediction Center

  • North–south field (Bz)

    Live

    5nT

    Northward

    The interplanetary field points north, the same way as Earth's own field where the two meet on the dayside. Aligned fields do not reconnect efficiently, so coupling into the magnetosphere is weak and geomagnetic activity tends to subside.

    Measured
    2026-09-17 05:10 UTC
    Type
    Observation
    Provider
    NOAA Space Weather Prediction Center

The last hour

0 nT+5−5514470km/s04:1605:10 UTC
  • Speed (km/s, left)
  • Bz GSM (nT, right)

Solar wind over the last hour: 55 one-minute rows. Speed 494 km/s at 2026-09-17 05:10 UTC, ranging 473 to 510 km/s. Bz 4.9 nT, reaching -1.5 nT southward.

Show these values as a table
Solar wind over the last hour: 55 one-minute rows. Speed 494 km/s at 2026-09-17 05:10 UTC, ranging 473 to 510 km/s. Bz 4.9 nT, reaching -1.5 nT southward.
Observed at L1 (UTC)Speed (km/s)Density (cm⁻³)Bt (nT)Bz GSM (nT)Modelled arrival
05:104943.995.14.905:56
05:095104.695.24.705:54
05:085084.246.0-0.605:53
05:074733.526.0-0.305:55
05:064804.276.0-0.305:53
05:054804.085.9-0.405:52
05:044763.575.80.405:52
05:034794.425.82.205:50
05:024874.726.01.705:49
05:014824.366.12.405:48
05:004874.875.82.705:47
04:594864.755.82.605:46
04:584854.595.83.005:45
04:574865.225.73.405:44
04:564844.535.93.505:43
04:554793.845.93.705:43
04:544853.805.83.205:41
04:534793.985.81.205:41
04:524844.485.71.505:40
04:514804.315.72.705:39
04:504885.045.63.305:37
04:494814.315.72.805:36
04:484924.395.62.505:35
04:474824.575.73.005:34
04:464824.415.63.505:33
04:454864.125.54.005:32
04:444904.245.63.405:31
04:434884.475.72.905:30
04:424824.475.82.705:30
04:414804.126.31.305:29
04:404733.866.3-0.805:28
04:394744.116.30.205:27
04:384763.916.10.805:26
04:374814.456.00.705:24
04:364834.436.01.605:23
04:354824.796.01.005:22
04:344854.716.3-1.505:21
04:334883.846.40.105:19
04:324754.276.40.305:20
04:314774.196.40.305:18
04:304753.546.50.205:18
04:294733.606.40.605:17
04:284874.946.4-0.105:14
04:274834.416.30.305:14
04:264896.036.30.205:12
04:254854.936.20.105:12
04:244845.186.1-0.305:11
04:234964.856.2-0.405:09
04:224905.136.3-0.305:08
04:214874.446.31.405:07
04:204885.366.12.505:06
04:194925.616.02.105:05
04:184945.696.31.405:04
04:174763.826.51.205:05
04:164763.676.61.105:04

An em dash means the provider published no value for that field in that row — it does not mean zero.

From NOAA's propagated solar-wind product: L1 observations advected to Earth's bow shock nose. Each row carries both its observation time at L1 and the modelled time the same plasma reaches Earth, and the table shows both. This is a model product, not a measurement made at Earth.

How to read these numbers

Speed sets how hard the wind presses on the magnetosphere and how quickly a disturbance arrives. The ambient slow wind runs at 300–400 km/s; a coronal-hole stream is typically 500–800 km/s.

Density multiplies with the square of speed to give the dynamic pressure, which is what compresses the magnetosphere. A dense, slow stream and a thin, fast one can push equally hard.

Bzis the one to watch. It is the north–south component of the interplanetary magnetic field in geocentric solar magnetospheric coordinates. When it is negative — southward — it opposes Earth's field where the two meet on the dayside, they reconnect, and solar-wind energy enters the system. A 900 km/s stream with a firmly northward field does far less than a 450 km/s stream with a sustained southward one.

Bt is the total field strength. A strong field with no southward component is not, by itself, a geomagnetic event.

Provenance

Every value on these pages is fetched from NOAA SWPC or NASA CCMC and carries the provider's own timestamp. Nothing is simulated, interpolated or filled in: when a provider cannot be reached, the panel says so and shows no number. There is no overall “space weather score” here — the agencies publish scales, and a single figure invented on top of them would be an opinion wearing NOAA's authority.

Speed

Live
Status
Live
Kind
Observation
Provider
NOAA Space Weather Prediction Center
Organisation
NOAA / National Weather Service
Fetched
2026-09-17 05:18 UTC
Generated by provider
2026-09-17 05:10 UTC
Provider cadence
1 min
Cached for
1 min
Treated as stale after
3 h
Licence
Public domain (US Government work). No licence fee and no redistribution restriction.

Source file: https://services.swpc.noaa.gov/products/summary/solar-wind-speed.json

Solar wind speed (real-time summary) from NOAA Space Weather Prediction Center, fetched from https://services.swpc.noaa.gov/products/summary/solar-wind-speed.json. The underlying spacecraft cadence is one minute, so a sixty-second cache can never hide a published value for longer than the interval between publications.

A single spot value from the real-time solar-wind monitor at the L1 Lagrange point, roughly 1.5 million km sunward of Earth — not a measurement at Earth. Solar wind takes on the order of an hour to cross that gap.

Magnetic field

Live
Status
Live
Kind
Observation
Provider
NOAA Space Weather Prediction Center
Organisation
NOAA / National Weather Service
Fetched
2026-09-17 05:18 UTC
Generated by provider
2026-09-17 05:10 UTC
Provider cadence
1 min
Cached for
1 min
Treated as stale after
3 h
Licence
Public domain (US Government work). No licence fee and no redistribution restriction.

Source file: https://services.swpc.noaa.gov/products/summary/solar-wind-mag-field.json

Interplanetary magnetic field (real-time summary) from NOAA Space Weather Prediction Center, fetched from https://services.swpc.noaa.gov/products/summary/solar-wind-mag-field.json. Matches the one-minute publication cadence of the real-time solar-wind monitor.

Total field strength and the north–south component in GSM coordinates, measured at L1. A southward Bz is what lets the solar wind couple into Earth's magnetosphere; the value alone does not forecast a storm.

Propagated series

Live
Status
Live
Kind
Model product
Provider
NOAA Space Weather Prediction Center
Organisation
NOAA / National Weather Service
Fetched
2026-09-17 05:18 UTC
Generated by provider
2026-09-17 05:10 UTC
Provider cadence
1 min
Cached for
1 min
Treated as stale after
3 h
Licence
Public domain (US Government work). No licence fee and no redistribution restriction.

Source file: https://services.swpc.noaa.gov/products/geospace/propagated-solar-wind-1-hour.json

Solar wind propagated to the bow shock (1 hour) from NOAA Space Weather Prediction Center, fetched from https://services.swpc.noaa.gov/products/geospace/propagated-solar-wind-1-hour.json. One-minute rows; a sixty-second cache adds at most one row of delay to the timeline.

A MODEL product, not a measurement at Earth: L1 observations advected to the bow shock nose. Each row carries both the observation time at L1 and the propagated arrival time, and AsteriaStar shows the distinction rather than collapsing it.

Sources & references

The primary and reference sources this topic draws on.

  • NOAA SWPCNOAA Space Weather Prediction Center

    Space-weather forecasts and alerts: aurora (OVATION), the Kp index, and the G1–G5 geomagnetic storm scale.