Space Weather

Space Weather

Space weather describes changing environmental conditions in near-Earth space. Magnetic fields, radiation, particles and matter, which have been ejected from the Sun, can interact with the Earth’s upper atmosphere and surrounding magnetic field to produce a  variety of effects.

Image courtesy of NASA/SDO and the AIA, EVE, and HMI science teams

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Aurora forecasts

Northern Hemisphere

There is the prospect of some minor enhancement to the auroral oval at times in the period, potentially affecting northern Scotland and similar geomagnetic latitudes, perhaps most likely on Saturday night into Sunday morning (UTC). Confidence in the timing of enhancements is relatively low, although the latitudes potentially affected are more assured.

Southern Hemisphere

There is the prospect of some minor enhancement to the auroral oval at times in the period at high latitudes, perhaps most likely on Saturday night into Sunday morning (UTC). Confidence in the timing of enhancements is relatively low, although the latitudes potentially affected are more assured.

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Forecast overview

Space Weather Forecast Headline: Residual slight chance of minor geomagnetic storm G1 today. Reduced daily chance of Moderate-class X-ray flares throughout.

Analysis of Space Weather Activity over past 24 hours

Solar Activity: Solar activity has been low, with occasional low-level Common-class X-ray flares recorded. One of the largest of these flares was a long-period one tied to a possible 'filament lift-off' (arc of plasma ejected from the Sun) in the northwest that started around 07/0730UTC, perhaps nudged higher by concurrent brightening of both of the largest sunspot regions on the facing side. Imagery to determine the trajectory of any ejecta from the filament is not yet available, however is a source of active monitoring. At the current time, no Coronal Mass Ejections (CMEs) were seen in imagery.

There are now seven sunspot regions on the Sun, with the development and numbering of a new, small magnetically bipolar region in the northeast. As in recent days, the facing side is dominated by the presence of the very large span of the most complex group which sprawls across about an eighth of the visible side of the Sun (in terms of longitude), although this spot group showed a slight decaying tendency in terms of area. The main potential 'threat' appears to be its contorted central portion, although this has yet to produce sympathetic activity. As well as this region, its immediate northern neighbour was the other noteworthy occupant of the front-side, showing slight proliferation of its intermediate spots. The remaining spots were small, and either stable or in decay, with little accompanying activity noted.

Solar Wind / Geomagnetic Activity: Solar winds are a reasonable analogue for those seen at a satellite 1.5 days upwind of Earth, and Earth is now considered likely to be sampling the tail end of a fast wind. There may also be minor Coronal Mass Ejection (CME) activity mixed in to bolster the usually quiet tail of the incumbent 'coronal hole', although this is not conclusive.

The solar wind speed itself showed a gradual decline through Slightly Elevated levels, before recovering to early highs after 07/1000UTC. Both the number of particles and their associated magnetic field were unremarkable.

The net result of these solar wind measures was just below Minor Storm G1. A possible reason for the sustained activity seen may be some minor component of a CME, else the frequent changes in the orientation of the magnetic field vector, although these are not conclusive surmises.

Energetic Particles / Solar Radiation: No solar radiation storms were observed.

Four-Day Space Weather Forecast Summary

Solar Activity: Solar activity carries a now reduced chance of reaching moderate, with the main risk predominately attributed to the largest sunspot. No significant regions leave the Sun in the period, and one forecast arrival later in the UTC weekend has yet to present for analysis, leading to a flat risk trend throughout.

Solar Wind / Geomagnetic Activity: The possible 'filament eruption' mentioned in the Solar Activity section does not feature in this forecast, pending imagery for analysis.

The only transient that does potentially feature in the forecast is the CME from a filament eruption on Tuesday 04 October, which may still arrive at Earth imminently. Any forecast effects have been accordingly reduced for it being a later, slower and presumably less impactful arrival. This may still lead to a resurgence in Elevated winds, but the chances are now slight.

The residual fast wind should abate in earnest over the remainder of day one (Friday 07 October). The next fast wind enhancement is then due either later day 2 (Saturday 08 October) or day 3 from another arriving 'coronal hole', the risk continuing into early day 4.

Geomagnetic activity is Likely to remain a little perturbed in the immediate term, with a now reduced slight chance of Minor Geomagnetic Storm G1, from here reducing for a time early day two (Saturday 08 October). There is then a resurgent slight chance of G1/Minor Storms again from the forecast fast wind arrival, this probably peaking on day 3 (Sunday 09 October).

Energetic Particles / Solar Radiation: There is now a reduced very slight chance of minor solar radiation storms, most likely due to any activity in the largest sunspot group.

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Solar imagery

SDO AIA-193

This channel highlights the outer atmosphere of the Sun - called the corona - as well as hot flare plasma. Hot active regions, solar flares, and coronal mass ejections will appear bright here. The dark areas - called coronal holes - are places where very little radiation is emitted, yet are the main source of solar wind particles.

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SDO AIA-304

This channel is especially good at showing areas where cooler dense plumes of plasma (filaments and prominences) are located above the visible surface of the Sun. Many of these features either can't be seen or appear as dark lines in the other channels. The bright areas show places where the plasma has a high density.

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